const std = @import("std");
const Allocator = std.mem.Allocator;
const llvm = @import("../llvm_api.zig");
const c = llvm.c;
const target_mod = @import("../target.zig");
const TargetConfig = target_mod.TargetConfig;
const ir_types = @import("types.zig");
const TypeId = ir_types.TypeId;
const TypeInfo = ir_types.TypeInfo;
const TypeTable = ir_types.TypeTable;
const StringId = ir_types.StringId;
const errors = @import("../errors.zig");
const ir_inst = @import("inst.zig");
const Ref = ir_inst.Ref;
const Span = ir_inst.Span;
const BlockId = ir_inst.BlockId;
const FuncId = ir_inst.FuncId;
const GlobalId = ir_inst.GlobalId;
const Inst = ir_inst.Inst;
const Op = ir_inst.Op;
const Block = ir_inst.Block;
const Function = ir_inst.Function;
const Global = ir_inst.Global;
const ir_module = @import("module.zig");
const Module = ir_module.Module;
const interp_mod = @import("interp.zig");
const Interpreter = interp_mod.Interpreter;
const Value = interp_mod.Value;

// The vendored error-trace ring buffer (library/vendors/sx_trace_runtime/sx_trace.c)
// is linked into the compiler. Comptime `#run` evaluation pushes frames to it via
// foreign `sx_trace_push` calls; after a `#run` we read it here to render the
// return trace for an escaping comptime error (E5.2).
extern fn sx_trace_len() u32;
extern fn sx_trace_frame_at(i: u32) u64;
extern fn sx_trace_clear() void;

fn isIdentByte(b: u8) bool {
    return (b >= 'a' and b <= 'z') or (b >= 'A' and b <= 'Z') or (b >= '0' and b <= '9') or b == '_';
}

/// JNI vtable slot offsets — indices into the `JNINativeInterface`
/// function-pointer array reachable via `*env`. Stable per the JNI
/// spec across versions; locked to the documented order in
/// `<jni.h>`. Slot numbers here MUST match the order of fields in
/// the C `JNINativeInterface_` struct.
const Jni = struct {
    const FindClass: u32 = 6;
    const NewGlobalRef: u32 = 21;
    const NewObject: u32 = 28;
    const GetObjectClass: u32 = 31;
    const GetMethodID: u32 = 33;
    // Call<Type>Method (instance, varargs variant). Each numeric type
    // has its own slot — distinct ABI per return type, so the JNI
    // runtime dispatches the right arg-shuffle for each.
    const CallObjectMethod: u32 = 34;
    const CallBooleanMethod: u32 = 37;
    const CallIntMethod: u32 = 49;
    const CallLongMethod: u32 = 52;
    const CallFloatMethod: u32 = 55;
    const CallDoubleMethod: u32 = 58;
    const CallVoidMethod: u32 = 61;
    // CallNonvirtual<T>Method (instance, super-dispatch variant). Used by
    // `super.method(args)` from inside a `#jni_main` Activity method body:
    // dispatch is bound to a specific class rather than going through the
    // vtable, so subclass overrides don't intercept the call. Signature:
    // `(JNIEnv*, jobject obj, jclass clazz, jmethodID, args...)`.
    const CallNonvirtualObjectMethod: u32 = 64;
    const CallNonvirtualBooleanMethod: u32 = 67;
    const CallNonvirtualIntMethod: u32 = 79;
    const CallNonvirtualLongMethod: u32 = 82;
    const CallNonvirtualFloatMethod: u32 = 85;
    const CallNonvirtualDoubleMethod: u32 = 88;
    const CallNonvirtualVoidMethod: u32 = 91;
    // Static-dispatch siblings — `target` IS already a `jclass`, so
    // no `GetObjectClass` step. `GetStaticMethodID` returns a
    // method-ID that's bound to a class+method+sig like the instance
    // variant; `CallStatic<Type>Method` dispatches without a `this`.
    const GetStaticMethodID: u32 = 113;
    const CallStaticObjectMethod: u32 = 114;
    const CallStaticBooleanMethod: u32 = 117;
    const CallStaticIntMethod: u32 = 129;
    const CallStaticLongMethod: u32 = 132;
    const CallStaticFloatMethod: u32 = 135;
    const CallStaticDoubleMethod: u32 = 138;
    const CallStaticVoidMethod: u32 = 141;
};

// ── LLVMEmitter ─────────────────────────────────────────────────────────
// Emits LLVM IR from an IR Module. This is the Phase 3 replacement for
// the AST-based codegen.

pub const LLVMEmitter = struct {
    // LLVM handles
    context: c.LLVMContextRef,
    llvm_module: c.LLVMModuleRef,
    builder: c.LLVMBuilderRef,
    target_machine: ?c.LLVMTargetMachineRef,

    // IR Module being emitted
    ir_mod: *const Module,

    // Set when a comptime `#run` raised an unhandled error (E5.2). The driver
    // (core.generateCode) aborts with a non-zero exit after emit() when set.
    comptime_failed: bool = false,

    // Allocator for temporary bookkeeping
    alloc: Allocator,

    // Maps IR Ref → LLVM Value for the current function
    ref_map: std.AutoHashMap(u32, c.LLVMValueRef),

    // Maps IR FuncId → LLVM function value
    func_map: std.AutoHashMap(u32, c.LLVMValueRef),

    // Maps IR GlobalId → LLVM global value
    global_map: std.AutoHashMap(u32, c.LLVMValueRef),

    // Maps (func_idx, block_idx) → LLVM BasicBlock
    block_map: std.AutoHashMap(u64, c.LLVMBasicBlockRef),

    // Cached LLVM types
    cached_i1: c.LLVMTypeRef,
    cached_i8: c.LLVMTypeRef,
    cached_i16: c.LLVMTypeRef,
    cached_i32: c.LLVMTypeRef,
    cached_i64: c.LLVMTypeRef,
    cached_f32: c.LLVMTypeRef,
    cached_f64: c.LLVMTypeRef,
    cached_ptr: c.LLVMTypeRef,
    cached_void: c.LLVMTypeRef,

    // Current ref counter — tracks which Ref index we're emitting within a function
    ref_counter: u32 = 0,

    // Pending PHI nodes to fixup after all blocks in a function are emitted
    pending_phis: std.ArrayList(PendingPhi),

    // Whether the current function being emitted is "main" (needs i32 return for JIT)
    current_func_is_main: bool = false,
    current_func_idx: u32 = 0,

    // Cached composite types
    string_struct_type: ?c.LLVMTypeRef,
    any_struct_type: ?c.LLVMTypeRef,
    closure_struct_type: ?c.LLVMTypeRef,
    // The shared `@objc_msgSend` function value. Lazily declared on
    // first `objc_msg_send` instruction; all `#objc_call` sites
    // dispatch through it with their own LLVMBuildCall2 function type
    // (opaque pointers — the function value is just a `ptr`).
    objc_msg_send_value: ?c.LLVMValueRef,
    // `(name, sig)` → `{cls_slot, mid_slot}` cache for `#jni_call`
    // interning (step 1.17). Two call sites with the same literal
    // name + signature share one pair of static slots, populated
    // lazily on the first call.
    jni_slots: std.StringHashMap(JniSlotPair),

    // Cached field name arrays for reflection (TypeId → LLVM global)
    field_name_arrays: std.AutoHashMap(u32, c.LLVMValueRef),
    // The always-linked tag-name table (global tag id → name); built once.
    tag_name_array: ?c.LLVMValueRef = null,

    // Lazy global `[N x string]` indexed by TypeId.index(), holding
    // each type's display name. Built on the first dynamic
    // `type_name(t)` call site; reused thereafter.
    type_name_array: ?c.LLVMValueRef = null,
    type_name_array_len: u32 = 0,

    // Target configuration (stored for ABI decisions during emission)
    target_config: TargetConfig,

    // Build configuration accumulated from #run blocks
    build_config: interp_mod.BuildConfig,

    // ── DWARF debug info (ERR E3.0) ──────────────────────────────────
    // Emitted only when the build keeps error traces (opt_level
    // none/less, matching lower.zig's `tracesEnabled`) AND a source map
    // is wired in via `setDebugContext`. One `DICompileUnit` (on the
    // main file) + a `DIFile` per source file + a `DISubprogram` per
    // emitted function + a `DILocation` per instruction (resolved from
    // `Inst.span`). Lets a captured return-address PC resolve to
    // file:line:col for E3.3's runtime trace formatting, and makes sx
    // binaries debuggable in lldb/gdb as a bonus.
    di_builder: c.LLVMDIBuilderRef = null,
    di_cu: c.LLVMMetadataRef = null,
    di_files: std.StringHashMap(c.LLVMMetadataRef),
    // The current function's DISubprogram — the scope for its
    // DILocations. Null between functions (and in functions we don't
    // describe, e.g. the synthetic Obj-C init constructors).
    di_scope: c.LLVMMetadataRef = null,
    // Source file of the function currently being emitted (span → line).
    current_func_file: []const u8 = "",
    // File path → source text (the diagnostics' `import_sources` map).
    // Null in unit tests, so no debug info is emitted there.
    import_sources: ?*const std.StringHashMap([:0]const u8) = null,
    // Main file path — the compile unit's file and the span-resolution
    // fallback for functions with no recorded source file.
    main_file: []const u8 = "",

    // ── Error-trace `Frame` (ERR E3.0 slice 3a) ──────────────────────
    // The compiled return-trace frame type: `{ string file, i32 line,
    // i32 col, string func }`. Hand-built here (not looked up from a sx
    // `TypeId`) so traces work even when the program doesn't import the
    // module that declares `Frame`. The layout MUST stay in lockstep with
    // `Frame` in `library/modules/trace.sx` (sx-side reader) and `SxFrame`
    // in `sx_trace.c` (the failable-main reporter).
    frame_struct_type: ?c.LLVMTypeRef = null,
    // Interns the `{ptr,i64}` string constants the `Frame` globals embed,
    // keyed by content, so a file/func name shared by N push sites is
    // emitted once. Keys are owned.
    frame_str_cache: std.StringHashMap(c.LLVMValueRef),

    const PendingPhi = struct {
        phi: c.LLVMValueRef,
        block_id: BlockId, // the block this phi belongs to
        param_index: u32,
    };

    const JniSlotPair = struct {
        cls_slot: c.LLVMValueRef, // @SX_JNI_CLS_<key>: ptr (GlobalRef to jclass)
        mid_slot: c.LLVMValueRef, // @SX_JNI_MID_<key>: ptr (jmethodID)
    };

    pub fn init(alloc: Allocator, ir_mod: *const Module, module_name: [*:0]const u8, target_config: TargetConfig) LLVMEmitter {
        // Initialize LLVM targets
        if (target_config.triple == null) {
            llvm.initNativeTarget();
        } else {
            llvm.initAllTargets();
        }

        const ctx = c.LLVMContextCreate();
        const llvm_module = c.LLVMModuleCreateWithNameInContext(module_name, ctx);
        const builder = c.LLVMCreateBuilderInContext(ctx);

        // Set target triple
        const triple_owned = target_config.triple == null;
        const triple = target_config.triple orelse c.LLVMGetDefaultTargetTriple();
        defer if (triple_owned) c.LLVMDisposeMessage(@constCast(triple));

        c.LLVMSetTarget(llvm_module, triple);

        // Create target machine and set data layout
        var target: c.LLVMTargetRef = null;
        var err_msg: [*c]u8 = null;
        var tm: c.LLVMTargetMachineRef = null;
        if (c.LLVMGetTargetFromTriple(triple, &target, &err_msg) == 0) {
            tm = c.LLVMCreateTargetMachine(
                target,
                triple,
                target_config.getCpu(),
                target_config.getFeatures(),
                target_config.opt_level.toLLVM(),
                c.LLVMRelocPIC,
                c.LLVMCodeModelDefault,
            );
            const dl = c.LLVMCreateTargetDataLayout(tm);
            c.LLVMSetModuleDataLayout(llvm_module, dl);
            c.LLVMDisposeTargetData(dl);
        } else {
            if (err_msg != null) c.LLVMDisposeMessage(err_msg);
        }

        return .{
            .context = ctx,
            .llvm_module = llvm_module,
            .builder = builder,
            .target_machine = tm,
            .ir_mod = ir_mod,
            .alloc = alloc,
            .ref_map = std.AutoHashMap(u32, c.LLVMValueRef).init(alloc),
            .func_map = std.AutoHashMap(u32, c.LLVMValueRef).init(alloc),
            .global_map = std.AutoHashMap(u32, c.LLVMValueRef).init(alloc),
            .block_map = std.AutoHashMap(u64, c.LLVMBasicBlockRef).init(alloc),
            .pending_phis = std.ArrayList(PendingPhi).empty,
            .cached_i1 = c.LLVMInt1TypeInContext(ctx),
            .cached_i8 = c.LLVMInt8TypeInContext(ctx),
            .cached_i16 = c.LLVMInt16TypeInContext(ctx),
            .cached_i32 = c.LLVMInt32TypeInContext(ctx),
            .cached_i64 = c.LLVMInt64TypeInContext(ctx),
            .cached_f32 = c.LLVMFloatTypeInContext(ctx),
            .cached_f64 = c.LLVMDoubleTypeInContext(ctx),
            .cached_ptr = c.LLVMPointerTypeInContext(ctx, 0),
            .cached_void = c.LLVMVoidTypeInContext(ctx),
            .string_struct_type = null,
            .any_struct_type = null,
            .closure_struct_type = null,
            .objc_msg_send_value = null,
            .jni_slots = std.StringHashMap(JniSlotPair).init(alloc),
            .field_name_arrays = std.AutoHashMap(u32, c.LLVMValueRef).init(alloc),
            .target_config = target_config,
            .build_config = .{},
            .di_files = std.StringHashMap(c.LLVMMetadataRef).init(alloc),
            .frame_str_cache = std.StringHashMap(c.LLVMValueRef).init(alloc),
        };
    }

    pub fn deinit(self: *LLVMEmitter) void {
        self.build_config.deinit(self.alloc);
        self.ref_map.deinit();
        self.func_map.deinit();
        self.field_name_arrays.deinit();
        var jni_it = self.jni_slots.keyIterator();
        while (jni_it.next()) |k| self.alloc.free(k.*);
        self.jni_slots.deinit();
        self.global_map.deinit();
        self.block_map.deinit();
        self.di_files.deinit();
        var fsc_it = self.frame_str_cache.keyIterator();
        while (fsc_it.next()) |k| self.alloc.free(k.*);
        self.frame_str_cache.deinit();
        if (self.di_builder != null) c.LLVMDisposeDIBuilder(self.di_builder);
        if (self.target_machine) |tm| c.LLVMDisposeTargetMachine(tm);
        c.LLVMDisposeBuilder(self.builder);
        c.LLVMDisposeModule(self.llvm_module);
        c.LLVMContextDispose(self.context);
    }

    // ── Top-level emit ──────────────────────────────────────────────

    pub fn emit(self: *LLVMEmitter) void {
        // Pass -1: Set up DWARF debug info (compile unit + module flags).
        // Must precede any DISubprogram (created per function below).
        self.initDebugInfo();

        // Pass 0: Declare and initialize globals
        self.emitGlobals();

        // Pass 0.5: Run comptime side-effect functions (#run expr; at top level)
        self.runComptimeSideEffects();

        // Pass 1: Declare all functions (so calls can reference them)
        for (self.ir_mod.functions.items, 0..) |func, i| {
            self.declareFunction(&func, @intCast(i));
        }

        // Pass 1.5: Initialize vtable globals (needs function declarations from Pass 1)
        self.initVtableGlobals();

        // Pass 2: Emit function bodies
        for (self.ir_mod.functions.items, 0..) |func, i| {
            if (func.is_extern or func.blocks.items.len == 0) continue;
            self.emitFunction(&func, @intCast(i));
        }

        // Pass 2.5: Emit Obj-C selector init constructor (Phase 1.5).
        self.emitObjcSelectorInit();

        // Pass 2.5b: Emit Obj-C class-pair registration constructor for
        // sx-defined classes (M1.2 A.4+). Runs BEFORE the foreign
        // class-cache populator (2.5c) so a sx-defined class is already
        // registered with the Obj-C runtime by the time
        // `objc_getClass(\"SxFoo\")` runs to populate the Phase 3.1
        // class-object cache — otherwise the cache slot would store
        // null and `SxFoo.method()` dispatches against null.
        self.emitObjcDefinedClassInit();

        // Pass 2.5c: Emit Obj-C class-object init constructor (Phase 3.1).
        // Same shape as the selector init — populates the per-module
        // cached `Class*` slots via `objc_getClass` at module-init time.
        self.emitObjcClassInit();

        // Pass 2.6: On macOS, chdir to the .app bundle's Resources dir at
        // startup so relative asset paths work when Finder/`open`
        // launches the binary with CWD=/. Non-bundled binaries no-op.
        self.emitMacosBundleChdir();

        // Pass 3: Verify typeSizeBytes matches LLVM's ABI sizes
        self.verifySizes();

        // Pass 4: Resolve DWARF temporary metadata. Must come after all
        // DISubprograms / DILocations are created and before the module
        // is verified or emitted.
        self.finalizeDebugInfo();
    }

    // ── DWARF debug info (ERR E3.0) ──────────────────────────────────

    /// Wire the source map + main file so spans can resolve to
    /// file:line:col. Called by the driver after `init`; absent in unit
    /// tests, which keeps debug-info emission off there.
    pub fn setDebugContext(self: *LLVMEmitter, import_sources: *const std.StringHashMap([:0]const u8), main_file: []const u8) void {
        self.import_sources = import_sources;
        self.main_file = main_file;
    }

    /// Debug info is emitted only when error traces are kept (opt_level
    /// none/less, matching `tracesEnabled` in lower.zig) and a source
    /// map is available. Release builds (default/aggressive) skip it, so
    /// the DWARF is strippable cost-free.
    fn debugEnabled(self: *const LLVMEmitter) bool {
        if (self.import_sources == null) return false;
        return self.target_config.opt_level == .none or self.target_config.opt_level == .less;
    }

    /// Source text for `file` via the diagnostics' file→source map (the
    /// same map `#caller_location` uses). Empty when unavailable —
    /// line:col then degrades to 1:1 rather than crash.
    fn sourceForFile(self: *LLVMEmitter, file: []const u8) []const u8 {
        const is = self.import_sources orelse return "";
        if (is.get(file)) |s| return s;
        if (self.main_file.len > 0) {
            if (is.get(self.main_file)) |s| return s;
        }
        return "";
    }

    /// The `DIFile` for `path`, created once and cached. Splits the path
    /// into basename + directory as DWARF expects. The directory MUST be
    /// non-empty: an empty `DW_AT_comp_dir` makes Apple's `ld` silently drop
    /// the whole object's debug map (no `N_OSO`), so a binary built from a
    /// bare filename (e.g. `sx build main.sx`) becomes undebuggable. Fall back
    /// to "." when the path has no directory component.
    fn diFileFor(self: *LLVMEmitter, path: []const u8) c.LLVMMetadataRef {
        if (self.di_files.get(path)) |f| return f;
        const slash = std.mem.lastIndexOfScalar(u8, path, '/');
        const dir = if (slash) |s| (if (s == 0) "/" else path[0..s]) else ".";
        const base = if (slash) |s| path[s + 1 ..] else path;
        const f = c.LLVMDIBuilderCreateFile(self.di_builder, base.ptr, base.len, dir.ptr, dir.len);
        self.di_files.put(path, f) catch {};
        return f;
    }

    /// Create the DIBuilder, the module flags ("Debug Info Version" /
    /// "Dwarf Version"), and the single compile unit on the main file.
    fn initDebugInfo(self: *LLVMEmitter) void {
        if (!self.debugEnabled()) return;
        self.di_builder = c.LLVMCreateDIBuilder(self.llvm_module);

        c.LLVMAddModuleFlag(
            self.llvm_module,
            c.LLVMModuleFlagBehaviorWarning,
            "Debug Info Version",
            "Debug Info Version".len,
            c.LLVMValueAsMetadata(c.LLVMConstInt(self.cached_i32, c.LLVMDebugMetadataVersion(), 0)),
        );
        c.LLVMAddModuleFlag(
            self.llvm_module,
            c.LLVMModuleFlagBehaviorWarning,
            "Dwarf Version",
            "Dwarf Version".len,
            c.LLVMValueAsMetadata(c.LLVMConstInt(self.cached_i32, 4, 0)),
        );

        const cu_file = self.diFileFor(if (self.main_file.len > 0) self.main_file else "sx");
        self.di_cu = c.LLVMDIBuilderCreateCompileUnit(
            self.di_builder,
            c.LLVMDWARFSourceLanguageC,
            cu_file,
            "sx",
            "sx".len,
            0, // isOptimized
            "",
            0, // flags
            0, // runtime version
            "",
            0, // split name
            c.LLVMDWARFEmissionFull,
            0, // DWOId
            0, // split debug inlining
            0, // debug info for profiling
            "",
            0, // sysroot
            "",
            0, // sdk
        );
    }

    /// Create a `DISubprogram` for `func` and attach it to `llvm_func`,
    /// making it the scope (`di_scope`) for the function's instruction
    /// locations. Clears any stale builder location first so synthetic
    /// functions emitted between sx functions carry none.
    fn beginFunctionDebug(self: *LLVMEmitter, func: *const Function, llvm_func: c.LLVMValueRef, name: []const u8) void {
        self.di_scope = null;
        c.LLVMSetCurrentDebugLocation2(self.builder, null);
        if (self.di_builder == null) return;

        const file = func.source_file orelse self.main_file;
        self.current_func_file = file;
        const di_file = self.diFileFor(file);
        const subroutine_ty = c.LLVMDIBuilderCreateSubroutineType(self.di_builder, di_file, null, 0, c.LLVMDIFlagZero);

        // Line = the first instruction's line (the function body's start),
        // else 1 when the body is empty / span-less.
        var line: c_uint = 1;
        if (func.blocks.items.len > 0 and func.blocks.items[0].insts.items.len > 0) {
            const sp = func.blocks.items[0].insts.items[0].span;
            const src = self.sourceForFile(file);
            line = errors.SourceLoc.compute(src, sp.start).line;
        }

        const is_local: c.LLVMBool = if (func.linkage == .external) 0 else 1;
        const subprogram = c.LLVMDIBuilderCreateFunction(
            self.di_builder,
            di_file, // scope
            name.ptr,
            name.len,
            name.ptr,
            name.len, // linkage name
            di_file,
            line,
            subroutine_ty,
            is_local,
            1, // is definition
            line, // scope line
            c.LLVMDIFlagZero,
            0, // isOptimized
        );
        c.LLVMSetSubprogram(llvm_func, subprogram);
        self.di_scope = subprogram;
    }

    /// End the current function's debug scope and clear the builder's
    /// location, so the next (possibly synthetic) function doesn't
    /// inherit a DILocation pointing into this function's subprogram.
    fn endFunctionDebug(self: *LLVMEmitter) void {
        self.di_scope = null;
        c.LLVMSetCurrentDebugLocation2(self.builder, null);
    }

    /// Set the builder's current debug location from an instruction span,
    /// scoped to the current function's subprogram. No-op when debug info
    /// is off (`di_scope == null`).
    fn setInstDebugLocation(self: *LLVMEmitter, span: Span) void {
        const scope = self.di_scope orelse return;
        const src = self.sourceForFile(self.current_func_file);
        const loc = errors.SourceLoc.compute(src, span.start);
        const di_loc = c.LLVMDIBuilderCreateDebugLocation(self.context, loc.line, loc.col, scope, null);
        c.LLVMSetCurrentDebugLocation2(self.builder, di_loc);
    }

    fn finalizeDebugInfo(self: *LLVMEmitter) void {
        if (self.di_builder == null) return;
        c.LLVMDIBuilderFinalize(self.di_builder);
    }

    /// Synthesize a module constructor that populates each interned
    /// Obj-C selector slot via `sel_registerName`, once at module
    /// load. Registered in `@llvm.global_ctors` so dyld / ld.so / the
    /// LLVM ORC JIT all run it before main. Per `#objc_call` site
    /// collapses to a single load from the slot.
    ///
    /// We tried clang's section-based shape (`__DATA,__objc_selrefs` +
    /// `externally_initialized` linkage, no constructor — dyld
    /// resolves at load time) and it works for fully-linked binaries
    /// via the system loader, BUT LLVM's ORC JIT (the engine behind
    /// `sx run`) doesn't process Mach-O Obj-C metadata sections —
    /// the slot stays at its initial value (the method-name string
    /// pointer) and `objc_msgSend` dispatches with a bogus SEL.
    /// `@llvm.global_ctors` is a portable choice that works both
    /// in-JIT and as a linked binary, at the cost of a tiny
    /// startup pass (one sel_registerName + store per unique
    /// selector).
    fn emitObjcSelectorInit(self: *LLVMEmitter) void {
        if (self.ir_mod.objc_selector_cache.items.len == 0) return;

        // Lazy-declare sel_registerName for the constructor body —
        // lower.zig only declares it when a non-literal selector
        // appears, which the constructor doesn't depend on.
        const sel_reg_name = "sel_registerName";
        const sel_reg_z = self.alloc.dupeZ(u8, sel_reg_name) catch unreachable;
        defer self.alloc.free(sel_reg_z);
        var sel_reg_fn = c.LLVMGetNamedFunction(self.llvm_module, sel_reg_z.ptr);
        var sel_reg_ty: c.LLVMTypeRef = undefined;
        if (sel_reg_fn == null) {
            var params: [1]c.LLVMTypeRef = .{self.cached_ptr};
            sel_reg_ty = c.LLVMFunctionType(self.cached_ptr, &params, 1, 0);
            sel_reg_fn = c.LLVMAddFunction(self.llvm_module, sel_reg_z.ptr, sel_reg_ty);
            c.LLVMSetLinkage(sel_reg_fn, c.LLVMExternalLinkage);
        } else {
            sel_reg_ty = c.LLVMGlobalGetValueType(sel_reg_fn);
        }

        // Constructor: void __sx_objc_selector_init().
        var no_params: [0]c.LLVMTypeRef = .{};
        const ctor_ty = c.LLVMFunctionType(self.cached_void, &no_params, 0, 0);
        const ctor = c.LLVMAddFunction(self.llvm_module, "__sx_objc_selector_init", ctor_ty);
        c.LLVMSetLinkage(ctor, c.LLVMInternalLinkage);
        const entry = c.LLVMAppendBasicBlockInContext(self.context, ctor, "entry");
        c.LLVMPositionBuilderAtEnd(self.builder, entry);

        for (self.ir_mod.objc_selector_cache.items) |entry_kv| {
            const sel_str = entry_kv.sel;
            const slot_gid = entry_kv.slot;
            const slot_global = self.global_map.get(@intCast(slot_gid.index())) orelse continue;

            // Method-name C-string — names match clang's convention
            // so debuggers / nm / dyld see the same symbols, even
            // though the surrounding section tagging isn't load-
            // bearing in our JIT path.
            const meth_str_z = self.alloc.allocSentinel(u8, sel_str.len, 0) catch continue;
            defer self.alloc.free(meth_str_z);
            @memcpy(meth_str_z[0..sel_str.len], sel_str);
            const str_const = c.LLVMConstStringInContext(self.context, meth_str_z.ptr, @intCast(sel_str.len), 0);
            const str_global = c.LLVMAddGlobal(self.llvm_module, c.LLVMTypeOf(str_const), "OBJC_METH_VAR_NAME_");
            c.LLVMSetInitializer(str_global, str_const);
            c.LLVMSetLinkage(str_global, c.LLVMPrivateLinkage);
            c.LLVMSetGlobalConstant(str_global, 1);
            c.LLVMSetUnnamedAddress(str_global, c.LLVMGlobalUnnamedAddr);

            var sel_args: [1]c.LLVMValueRef = .{str_global};
            const sel_val = c.LLVMBuildCall2(self.builder, sel_reg_ty, sel_reg_fn, &sel_args, 1, "sel");
            _ = c.LLVMBuildStore(self.builder, sel_val, slot_global);
        }
        _ = c.LLVMBuildRetVoid(self.builder);

        // Register the constructor in @llvm.global_ctors. dyld picks
        // this up for a fully-linked binary at load time.
        const i32_ty = self.cached_i32;
        const ptr_ty = self.cached_ptr;
        var ctor_field_types: [3]c.LLVMTypeRef = .{ i32_ty, ptr_ty, ptr_ty };
        const ctor_struct_ty = c.LLVMStructTypeInContext(self.context, &ctor_field_types, 3, 0);
        var ctor_fields: [3]c.LLVMValueRef = .{
            c.LLVMConstInt(i32_ty, 65535, 0),
            ctor,
            c.LLVMConstNull(ptr_ty),
        };
        const ctor_entry = c.LLVMConstNamedStruct(ctor_struct_ty, &ctor_fields, 3);
        const ctors_arr_ty = c.LLVMArrayType2(ctor_struct_ty, 1);
        var ctor_entries: [1]c.LLVMValueRef = .{ctor_entry};
        const ctors_init = c.LLVMConstArray2(ctor_struct_ty, &ctor_entries, 1);
        const ctors_global = c.LLVMAddGlobal(self.llvm_module, ctors_arr_ty, "llvm.global_ctors");
        c.LLVMSetInitializer(ctors_global, ctors_init);
        c.LLVMSetLinkage(ctors_global, c.LLVMAppendingLinkage);

        // BUT — LLVM's ORC JIT (the engine for `sx run`) doesn't
        // automatically run `@llvm.global_ctors`. Inject a direct
        // call from `main`'s entry block as well; idempotent under
        // dyld (sel_registerName returns the same SEL on second call).
        const main_z = "main";
        const main_fn = c.LLVMGetNamedFunction(self.llvm_module, main_z);
        if (main_fn != null) {
            const entry_bb = c.LLVMGetEntryBasicBlock(main_fn);
            const first_inst = c.LLVMGetFirstInstruction(entry_bb);
            if (first_inst != null) {
                c.LLVMPositionBuilderBefore(self.builder, first_inst);
            } else {
                c.LLVMPositionBuilderAtEnd(self.builder, entry_bb);
            }
            var no_args: [0]c.LLVMValueRef = .{};
            _ = c.LLVMBuildCall2(self.builder, ctor_ty, ctor, &no_args, 0, "");
        }
    }

    /// Phase 3.1 companion to `emitObjcSelectorInit`. Walks
    /// `module.objc_class_cache` and synthesizes a constructor that
    /// populates each cached `Class*` slot via `objc_getClass(name)`
    /// exactly once at module-init. Registered in `@llvm.global_ctors`
    /// AND injected at the top of `main()` for the ORC JIT path.
    fn emitObjcClassInit(self: *LLVMEmitter) void {
        if (self.ir_mod.objc_class_cache.items.len == 0) return;

        // Lazy-declare objc_getClass(name: *u8) -> *void.
        const get_class_name = "objc_getClass";
        const get_class_z = self.alloc.dupeZ(u8, get_class_name) catch unreachable;
        defer self.alloc.free(get_class_z);
        var get_class_fn = c.LLVMGetNamedFunction(self.llvm_module, get_class_z.ptr);
        var get_class_ty: c.LLVMTypeRef = undefined;
        if (get_class_fn == null) {
            var params: [1]c.LLVMTypeRef = .{self.cached_ptr};
            get_class_ty = c.LLVMFunctionType(self.cached_ptr, &params, 1, 0);
            get_class_fn = c.LLVMAddFunction(self.llvm_module, get_class_z.ptr, get_class_ty);
            c.LLVMSetLinkage(get_class_fn, c.LLVMExternalLinkage);
        } else {
            get_class_ty = c.LLVMGlobalGetValueType(get_class_fn);
        }

        // Constructor: void __sx_objc_class_init().
        var no_params: [0]c.LLVMTypeRef = .{};
        const ctor_ty = c.LLVMFunctionType(self.cached_void, &no_params, 0, 0);
        const ctor = c.LLVMAddFunction(self.llvm_module, "__sx_objc_class_init", ctor_ty);
        c.LLVMSetLinkage(ctor, c.LLVMInternalLinkage);
        const entry = c.LLVMAppendBasicBlockInContext(self.context, ctor, "entry");
        c.LLVMPositionBuilderAtEnd(self.builder, entry);

        for (self.ir_mod.objc_class_cache.items) |entry_kv| {
            const class_name = entry_kv.name;
            const slot_gid = entry_kv.slot;
            const slot_global = self.global_map.get(@intCast(slot_gid.index())) orelse continue;

            // Class-name C-string.
            const name_z = self.alloc.allocSentinel(u8, class_name.len, 0) catch continue;
            defer self.alloc.free(name_z);
            @memcpy(name_z[0..class_name.len], class_name);
            const str_const = c.LLVMConstStringInContext(self.context, name_z.ptr, @intCast(class_name.len), 0);
            const str_global = c.LLVMAddGlobal(self.llvm_module, c.LLVMTypeOf(str_const), "OBJC_CLASS_NAME_");
            c.LLVMSetInitializer(str_global, str_const);
            c.LLVMSetLinkage(str_global, c.LLVMPrivateLinkage);
            c.LLVMSetGlobalConstant(str_global, 1);
            c.LLVMSetUnnamedAddress(str_global, c.LLVMGlobalUnnamedAddr);

            var call_args: [1]c.LLVMValueRef = .{str_global};
            const class_val = c.LLVMBuildCall2(self.builder, get_class_ty, get_class_fn, &call_args, 1, "cls");
            _ = c.LLVMBuildStore(self.builder, class_val, slot_global);
        }
        _ = c.LLVMBuildRetVoid(self.builder);

        // Register in @llvm.global_ctors for AOT + inject into main for ORC JIT.
        const i32_ty = self.cached_i32;
        const ptr_ty = self.cached_ptr;
        var ctor_field_types: [3]c.LLVMTypeRef = .{ i32_ty, ptr_ty, ptr_ty };
        const ctor_struct_ty = c.LLVMStructTypeInContext(self.context, &ctor_field_types, 3, 0);
        var ctor_fields: [3]c.LLVMValueRef = .{
            c.LLVMConstInt(i32_ty, 65535, 0),
            ctor,
            c.LLVMConstNull(ptr_ty),
        };
        const ctor_entry = c.LLVMConstNamedStruct(ctor_struct_ty, &ctor_fields, 3);

        // Append-vs-replace the existing global_ctors. Selector init may
        // have created `@llvm.global_ctors` already — extend its array
        // rather than overwriting.
        const existing_z = "llvm.global_ctors";
        const existing = c.LLVMGetNamedGlobal(self.llvm_module, existing_z);
        if (existing != null) {
            const existing_init = c.LLVMGetInitializer(existing);
            const existing_arr_ty = c.LLVMGlobalGetValueType(existing);
            const old_count = c.LLVMGetArrayLength(existing_arr_ty);
            const new_count: c_uint = old_count + 1;
            var new_entries = std.ArrayList(c.LLVMValueRef).empty;
            defer new_entries.deinit(self.alloc);
            var i: c_uint = 0;
            while (i < old_count) : (i += 1) {
                new_entries.append(self.alloc, c.LLVMGetAggregateElement(existing_init, i)) catch unreachable;
            }
            new_entries.append(self.alloc, ctor_entry) catch unreachable;
            const new_arr_ty = c.LLVMArrayType2(ctor_struct_ty, new_count);
            const new_init = c.LLVMConstArray2(ctor_struct_ty, new_entries.items.ptr, new_count);
            const new_global = c.LLVMAddGlobal(self.llvm_module, new_arr_ty, "llvm.global_ctors.new");
            c.LLVMSetInitializer(new_global, new_init);
            c.LLVMSetLinkage(new_global, c.LLVMAppendingLinkage);
            c.LLVMSetValueName2(existing, "llvm.global_ctors.old", "llvm.global_ctors.old".len);
            c.LLVMSetValueName2(new_global, "llvm.global_ctors", "llvm.global_ctors".len);
            c.LLVMDeleteGlobal(existing);
        } else {
            const ctors_arr_ty = c.LLVMArrayType2(ctor_struct_ty, 1);
            var ctor_entries: [1]c.LLVMValueRef = .{ctor_entry};
            const ctors_init = c.LLVMConstArray2(ctor_struct_ty, &ctor_entries, 1);
            const ctors_global = c.LLVMAddGlobal(self.llvm_module, ctors_arr_ty, "llvm.global_ctors");
            c.LLVMSetInitializer(ctors_global, ctors_init);
            c.LLVMSetLinkage(ctors_global, c.LLVMAppendingLinkage);
        }

        // ORC JIT injection: same trick as emitObjcSelectorInit. Inject a
        // direct call from main's entry so the JIT path populates the
        // slots too. Must run AFTER the selector init's main injection
        // (selectors are needed independently of class objects), so we
        // place this call AFTER the first instruction (which is the
        // selector-init call, if present) rather than at the very top.
        const main_z = "main";
        const main_fn = c.LLVMGetNamedFunction(self.llvm_module, main_z);
        if (main_fn != null) {
            const entry_bb = c.LLVMGetEntryBasicBlock(main_fn);
            // Walk past any existing init calls (selector init etc.) so
            // class init runs after them. The order within main's prelude
            // doesn't matter functionally (the two caches are independent),
            // but stable ordering keeps IR snapshots deterministic.
            var insert_before = c.LLVMGetFirstInstruction(entry_bb);
            while (insert_before != null) : (insert_before = c.LLVMGetNextInstruction(insert_before)) {
                if (c.LLVMGetInstructionOpcode(insert_before) != c.LLVMCall) break;
            }
            if (insert_before != null) {
                c.LLVMPositionBuilderBefore(self.builder, insert_before);
            } else {
                c.LLVMPositionBuilderAtEnd(self.builder, entry_bb);
            }
            var no_args: [0]c.LLVMValueRef = .{};
            _ = c.LLVMBuildCall2(self.builder, ctor_ty, ctor, &no_args, 0, "");
        }
    }

    /// M1.2 A.4 — emit class-pair registration constructor for every
    /// sx-defined `#objc_class` declaration. Same shape as the Phase
    /// 3.1 `emitObjcClassInit` companion: a `@llvm.global_ctors`-
    /// registered constructor that runs at module load AND gets
    /// injected at the top of `main` for the ORC JIT path (which
    /// doesn't honor `@llvm.global_ctors`).
    ///
    /// For each entry in `objc_defined_class_cache`:
    ///   super_cls = objc_getClass("<ParentName>")  // default NSObject
    ///   cls       = objc_allocateClassPair(super_cls, "<ClassName>", 0)
    ///   class_addIvar(cls, "__sx_state", 8, 3, "^v")     // M1.2 A.4b.i
    ///   objc_registerClassPair(cls)
    ///   g_<ClassName>_state_ivar = class_getInstanceVariable(cls, "__sx_state")
    ///
    /// Method IMPs (`class_addMethod`) and the `+alloc` / `-dealloc`
    /// overrides come in A.4b.ii / A.5 / A.6.
    fn emitObjcDefinedClassInit(self: *LLVMEmitter) void {
        if (self.ir_mod.objc_defined_class_cache.items.len == 0) return;

        const ptr_ty = self.cached_ptr;
        const i32_ty = self.cached_i32;
        const i64_ty = self.cached_i64;
        const i8_ty = c.LLVMInt8TypeInContext(self.context);

        // Lazy-declare the Obj-C runtime APIs the constructor calls.
        // objc_getClass(name: *u8) -> *void.
        const get_class_fn, const get_class_ty = self.lazyDeclareCRuntime("objc_getClass", &[_]c.LLVMTypeRef{ptr_ty}, ptr_ty, 0);
        // objc_allocateClassPair(super: *void, name: *u8, extra: usize) -> *void.
        const alloc_pair_fn, const alloc_pair_ty = self.lazyDeclareCRuntime("objc_allocateClassPair", &[_]c.LLVMTypeRef{ ptr_ty, ptr_ty, i64_ty }, ptr_ty, 0);
        // class_addIvar(cls: *void, name: *u8, size: u64, log2align: u8, type: *u8) -> bool.
        const add_ivar_fn, const add_ivar_ty = self.lazyDeclareCRuntime("class_addIvar", &[_]c.LLVMTypeRef{ ptr_ty, ptr_ty, i64_ty, i8_ty, ptr_ty }, i8_ty, 0);
        // sel_registerName(name: *u8) -> *void.
        const sel_reg_fn, const sel_reg_ty = self.lazyDeclareCRuntime("sel_registerName", &[_]c.LLVMTypeRef{ptr_ty}, ptr_ty, 0);
        // class_addMethod(cls: *void, sel: *void, imp: *void, types: *u8) -> bool.
        const add_method_fn, const add_method_ty = self.lazyDeclareCRuntime("class_addMethod", &[_]c.LLVMTypeRef{ ptr_ty, ptr_ty, ptr_ty, ptr_ty }, i8_ty, 0);
        // objc_registerClassPair(cls: *void) -> void.
        const register_fn, const register_ty = self.lazyDeclareCRuntime("objc_registerClassPair", &[_]c.LLVMTypeRef{ptr_ty}, self.cached_void, 0);
        // class_getInstanceVariable(cls: *void, name: *u8) -> *Ivar.
        const get_iv_fn, const get_iv_ty = self.lazyDeclareCRuntime("class_getInstanceVariable", &[_]c.LLVMTypeRef{ ptr_ty, ptr_ty }, ptr_ty, 0);

        // Constructor: void __sx_objc_defined_class_init().
        var no_params: [0]c.LLVMTypeRef = .{};
        const ctor_ty = c.LLVMFunctionType(self.cached_void, &no_params, 0, 0);
        const ctor = c.LLVMAddFunction(self.llvm_module, "__sx_objc_defined_class_init", ctor_ty);
        c.LLVMSetLinkage(ctor, c.LLVMInternalLinkage);
        const entry = c.LLVMAppendBasicBlockInContext(self.context, ctor, "entry");
        c.LLVMPositionBuilderAtEnd(self.builder, entry);

        // Reusable C-string globals for ivar metadata (same across classes).
        const sx_state_name_global = self.emitPrivateCString("__sx_state", "OBJC_IVAR_NAME_");
        const sx_state_enc_global = self.emitPrivateCString("^v", "OBJC_IVAR_TYPE_");

        for (self.ir_mod.objc_defined_class_cache.items) |entry_kv| {
            const fcd = entry_kv.decl;
            const class_name = fcd.name;

            // Parent class — pre-resolved Obj-C runtime name from
            // lower.zig (M2.3 resolveObjcParentName). Stored on the
            // cache entry so emit_llvm doesn't re-walk
            // foreign_class_map here.
            const parent_name = entry_kv.parent_objc_name;

            const parent_str_global = self.emitPrivateCString(parent_name, "OBJC_CLASS_NAME_");
            const class_str_global = self.emitPrivateCString(class_name, "OBJC_CLASS_NAME_");

            // super_cls = objc_getClass("ParentName")
            var get_args: [1]c.LLVMValueRef = .{parent_str_global};
            const super_val = c.LLVMBuildCall2(self.builder, get_class_ty, get_class_fn, &get_args, 1, "super_cls");

            // cls = objc_allocateClassPair(super_cls, "ClassName", 0)
            var alloc_args: [3]c.LLVMValueRef = .{ super_val, class_str_global, c.LLVMConstInt(i64_ty, 0, 0) };
            const cls_val = c.LLVMBuildCall2(self.builder, alloc_pair_ty, alloc_pair_fn, &alloc_args, 3, "cls");

            // class_addIvar(cls, "__sx_state", 8, 3, "^v")
            //   size = 8 (pointer)        — sizeof(*void) on 64-bit
            //   log2align = 3             — alignof(*void) = 8 = 2^3
            //   type = "^v" (encoded *void)
            var ivar_args: [5]c.LLVMValueRef = .{
                cls_val,
                sx_state_name_global,
                c.LLVMConstInt(i64_ty, 8, 0),
                c.LLVMConstInt(i8_ty, 3, 0),
                sx_state_enc_global,
            };
            _ = c.LLVMBuildCall2(self.builder, add_ivar_ty, add_ivar_fn, &ivar_args, 5, "");

            // Class-method registration (M2.1(b)) and the +alloc IMP
            // (M1.2 A.5) both target the metaclass. Compute it once
            // up-front so all metaclass-bound class_addMethod calls
            // can reference the same LLVM value.
            //
            // metaclass = object_getClass(cls).  (object_getClass on a
            // Class returns the metaclass — a Class IS an instance of
            // its metaclass. Distinct from objc_getClass(name).)
            const obj_get_class_fn, const obj_get_class_ty = self.lazyDeclareCRuntime("object_getClass", &[_]c.LLVMTypeRef{ptr_ty}, ptr_ty, 0);
            var ogc_args: [1]c.LLVMValueRef = .{cls_val};
            const metaclass_val = c.LLVMBuildCall2(self.builder, obj_get_class_ty, obj_get_class_fn, &ogc_args, 1, "metacls");

            // class_addMethod(target, sel_registerName(sel), imp, encoding)
            // — register each method's IMP trampoline (M1.2 A.4b.iii
            // + M2.1(b)). Instance methods register on `cls`; class
            // methods (`is_class`) on the metaclass. Must run BEFORE
            // objc_registerClassPair; the runtime locks the method
            // list at registration time on some SDK versions.
            for (entry_kv.methods) |method| {
                const sel_str_global = self.emitPrivateCString(method.sel, "OBJC_METH_VAR_NAME_");
                const enc_str_global = self.emitPrivateCString(method.encoding, "OBJC_METH_VAR_TYPE_");

                var sel_args: [1]c.LLVMValueRef = .{sel_str_global};
                const sel_val = c.LLVMBuildCall2(self.builder, sel_reg_ty, sel_reg_fn, &sel_args, 1, "sel");

                const imp_z = self.alloc.dupeZ(u8, method.imp_name) catch continue;
                defer self.alloc.free(imp_z);
                const imp_fn = c.LLVMGetNamedFunction(self.llvm_module, imp_z.ptr);
                if (imp_fn == null) continue;

                const target_cls = if (method.is_class) metaclass_val else cls_val;
                var add_args: [4]c.LLVMValueRef = .{ target_cls, sel_val, imp_fn, enc_str_global };
                _ = c.LLVMBuildCall2(self.builder, add_method_ty, add_method_fn, &add_args, 4, "");
            }

            // M2.3 / M3.2 — register `#implements` protocol conformances
            // BEFORE objc_registerClassPair. iOS checks
            // `class_conformsToProtocol` when instantiating scene
            // delegates and other protocol-typed callbacks; without
            // these the runtime silently rejects the class.
            //
            // The protocol may not be present on every SDK / runtime
            // (dead-strip pruning, version skew), so `objc_getProtocol`
            // returning null is non-fatal — skip the addProtocol call.
            const get_proto_fn, const get_proto_ty = self.lazyDeclareCRuntime("objc_getProtocol", &[_]c.LLVMTypeRef{ptr_ty}, ptr_ty, 0);
            const add_proto_fn, const add_proto_ty = self.lazyDeclareCRuntime("class_addProtocol", &[_]c.LLVMTypeRef{ ptr_ty, ptr_ty }, i8_ty, 0);
            for (fcd.members) |m| switch (m) {
                .implements => |proto_alias| {
                    const proto_str_global = self.emitPrivateCString(proto_alias, "OBJC_PROTOCOL_NAME_");
                    var gp_args: [1]c.LLVMValueRef = .{proto_str_global};
                    const proto_val = c.LLVMBuildCall2(self.builder, get_proto_ty, get_proto_fn, &gp_args, 1, "proto");
                    var ap_args: [2]c.LLVMValueRef = .{ cls_val, proto_val };
                    _ = c.LLVMBuildCall2(self.builder, add_proto_ty, add_proto_fn, &ap_args, 2, "");
                },
                else => {},
            };

            // objc_registerClassPair(cls)
            var reg_args: [1]c.LLVMValueRef = .{cls_val};
            _ = c.LLVMBuildCall2(self.builder, register_ty, register_fn, &reg_args, 1, "");

            // Cache the class pointer in `__<Cls>_class` global so the
            // synthesized -dealloc trampoline (M1.2 A.6) can use it for
            // [super dealloc] dispatch via objc_msgSendSuper2.
            const class_global_name = std.fmt.allocPrint(self.alloc, "__{s}_class", .{class_name}) catch continue;
            defer self.alloc.free(class_global_name);
            const class_global_z = self.alloc.dupeZ(u8, class_global_name) catch continue;
            defer self.alloc.free(class_global_z);
            const class_global = c.LLVMGetNamedGlobal(self.llvm_module, class_global_z.ptr);
            if (class_global != null) {
                _ = c.LLVMBuildStore(self.builder, cls_val, class_global);
            }

            // M1.2 A.6 — register the synthesized `-dealloc` IMP on the
            // class itself (instance method). The runtime fires it at
            // refcount-zero; the IMP frees __sx_state and chains to
            // [super dealloc].
            const dealloc_imp_name = std.fmt.allocPrint(self.alloc, "__{s}_dealloc_imp", .{class_name}) catch continue;
            defer self.alloc.free(dealloc_imp_name);
            const dealloc_imp_z = self.alloc.dupeZ(u8, dealloc_imp_name) catch continue;
            defer self.alloc.free(dealloc_imp_z);
            const dealloc_imp_fn = c.LLVMGetNamedFunction(self.llvm_module, dealloc_imp_z.ptr);
            if (dealloc_imp_fn != null) {
                const dealloc_sel_global = self.emitPrivateCString("dealloc", "OBJC_METH_VAR_NAME_");
                const dealloc_enc_global = self.emitPrivateCString("v@:", "OBJC_METH_VAR_TYPE_");

                var sel_args: [1]c.LLVMValueRef = .{dealloc_sel_global};
                const sel_val = c.LLVMBuildCall2(self.builder, sel_reg_ty, sel_reg_fn, &sel_args, 1, "sel_dealloc");

                var add_args: [4]c.LLVMValueRef = .{ cls_val, sel_val, dealloc_imp_fn, dealloc_enc_global };
                _ = c.LLVMBuildCall2(self.builder, add_method_ty, add_method_fn, &add_args, 4, "");
            }

            // M1.2 A.5 — register the synthesized `+alloc` IMP on the
            // metaclass. Class methods live on the metaclass (every
            // Class object's `isa` points to the metaclass), so we
            // resolve it via `object_getClass(cls)` and `class_addMethod`
            // the IMP there. Encoding `@@:` = returns id, takes Class,
            // then SEL — Apple's standard `+alloc` shape. This override
            // wins over NSObject's default +alloc; runtime instantiations
            // (UIKit, Info.plist, NSCoder) go through our IMP and get the
            // __sx_state ivar bound.
            const alloc_imp_name = std.fmt.allocPrint(self.alloc, "__{s}_alloc_imp", .{class_name}) catch continue;
            defer self.alloc.free(alloc_imp_name);
            const alloc_imp_z = self.alloc.dupeZ(u8, alloc_imp_name) catch continue;
            defer self.alloc.free(alloc_imp_z);
            const alloc_imp_fn = c.LLVMGetNamedFunction(self.llvm_module, alloc_imp_z.ptr);
            if (alloc_imp_fn != null) {
                // metaclass_val was computed up-front above (shared
                // with class-method registration). +alloc is a class
                // method registered on the metaclass.
                const alloc_sel_global = self.emitPrivateCString("alloc", "OBJC_METH_VAR_NAME_");
                const alloc_enc_global = self.emitPrivateCString("@@:", "OBJC_METH_VAR_TYPE_");

                var sel_args: [1]c.LLVMValueRef = .{alloc_sel_global};
                const sel_val = c.LLVMBuildCall2(self.builder, sel_reg_ty, sel_reg_fn, &sel_args, 1, "sel_alloc");

                var add_args: [4]c.LLVMValueRef = .{ metaclass_val, sel_val, alloc_imp_fn, alloc_enc_global };
                _ = c.LLVMBuildCall2(self.builder, add_method_ty, add_method_fn, &add_args, 4, "");
            }

            // Cache the ivar handle in the per-class global so trampolines
            // can read the __sx_state ivar without re-looking-it-up. The
            // global is declared by lower.zig (M1.2 A.4b.i) and starts as
            // null; the constructor fills it in here.
            const ivar_global_name = std.fmt.allocPrint(self.alloc, "__{s}_state_ivar", .{class_name}) catch continue;
            defer self.alloc.free(ivar_global_name);
            const ivar_global_z = self.alloc.dupeZ(u8, ivar_global_name) catch continue;
            defer self.alloc.free(ivar_global_z);
            const ivar_global = c.LLVMGetNamedGlobal(self.llvm_module, ivar_global_z.ptr);
            if (ivar_global != null) {
                var iv_args: [2]c.LLVMValueRef = .{ cls_val, sx_state_name_global };
                const iv_val = c.LLVMBuildCall2(self.builder, get_iv_ty, get_iv_fn, &iv_args, 2, "iv");
                _ = c.LLVMBuildStore(self.builder, iv_val, ivar_global);
            }
        }
        _ = c.LLVMBuildRetVoid(self.builder);

        // Inject the call into main's entry block ONLY — skip
        // @llvm.global_ctors. Apple's frameworks (UIKit on iOS,
        // AppKit on macOS) register their Obj-C classes during
        // dyld's image-init phase, which overlaps global_ctors. If
        // we ran there too, `objc_getClass(\"UIResponder\")` would
        // return null and `objc_allocateClassPair(null, ...)` would
        // crash inside objc_registerClassPair. main's entry runs
        // AFTER dyld's framework init is complete but BEFORE user
        // code (UIApplicationMain), so the runtime sees the parent
        // class properly.
        self.injectCtorIntoMain(ctor, ctor_ty);

        _ = i32_ty;
    }

    /// Lazy-declare an extern C runtime function. Returns (fn-value, fn-type).
    fn lazyDeclareCRuntime(self: *LLVMEmitter, name: []const u8, params: []const c.LLVMTypeRef, ret_ty: c.LLVMTypeRef, is_var_arg: c_int) struct { c.LLVMValueRef, c.LLVMTypeRef } {
        const name_z = self.alloc.dupeZ(u8, name) catch unreachable;
        defer self.alloc.free(name_z);
        var fn_value = c.LLVMGetNamedFunction(self.llvm_module, name_z.ptr);
        var fn_ty: c.LLVMTypeRef = undefined;
        if (fn_value == null) {
            fn_ty = c.LLVMFunctionType(ret_ty, @constCast(params.ptr), @intCast(params.len), is_var_arg);
            fn_value = c.LLVMAddFunction(self.llvm_module, name_z.ptr, fn_ty);
            c.LLVMSetLinkage(fn_value, c.LLVMExternalLinkage);
        } else {
            fn_ty = c.LLVMGlobalGetValueType(fn_value);
        }
        return .{ fn_value, fn_ty };
    }

    /// Emit a private constant C string global. Used for class names,
    /// selector names, etc. consumed by the Obj-C runtime.
    fn emitPrivateCString(self: *LLVMEmitter, s: []const u8, name_hint: []const u8) c.LLVMValueRef {
        const s_z = self.alloc.allocSentinel(u8, s.len, 0) catch unreachable;
        defer self.alloc.free(s_z);
        @memcpy(s_z[0..s.len], s);
        const str_const = c.LLVMConstStringInContext(self.context, s_z.ptr, @intCast(s.len), 0);
        const name_z = self.alloc.dupeZ(u8, name_hint) catch unreachable;
        defer self.alloc.free(name_z);
        const str_global = c.LLVMAddGlobal(self.llvm_module, c.LLVMTypeOf(str_const), name_z.ptr);
        c.LLVMSetInitializer(str_global, str_const);
        c.LLVMSetLinkage(str_global, c.LLVMPrivateLinkage);
        c.LLVMSetGlobalConstant(str_global, 1);
        c.LLVMSetUnnamedAddress(str_global, c.LLVMGlobalUnnamedAddr);
        return str_global;
    }

    /// Append a constructor entry to `@llvm.global_ctors` (creating the
    /// global if not present, extending the array if so) AND inject a
    /// direct call from `main`'s entry block so the ORC JIT path runs
    /// the constructor too.
    /// Inject a call to `ctor()` at the start of `main`'s entry block
    /// (past any existing init calls). Used by class-pair init etc.
    /// that need to run BEFORE user code but AFTER dyld's framework
    /// load — global_ctors is too early because Apple frameworks
    /// (UIKit etc.) register their Obj-C classes during their own
    /// init phase that overlaps ours.
    fn injectCtorIntoMain(self: *LLVMEmitter, ctor: c.LLVMValueRef, ctor_ty: c.LLVMTypeRef) void {
        const main_z = "main";
        const main_fn = c.LLVMGetNamedFunction(self.llvm_module, main_z);
        if (main_fn == null) return;
        const entry_bb = c.LLVMGetEntryBasicBlock(main_fn);
        var insert_before = c.LLVMGetFirstInstruction(entry_bb);
        while (insert_before != null) : (insert_before = c.LLVMGetNextInstruction(insert_before)) {
            if (c.LLVMGetInstructionOpcode(insert_before) != c.LLVMCall) break;
        }
        if (insert_before != null) {
            c.LLVMPositionBuilderBefore(self.builder, insert_before);
        } else {
            c.LLVMPositionBuilderAtEnd(self.builder, entry_bb);
        }
        var no_args: [0]c.LLVMValueRef = .{};
        _ = c.LLVMBuildCall2(self.builder, ctor_ty, ctor, &no_args, 0, "");
    }

    fn appendModuleCtor(self: *LLVMEmitter, ctor: c.LLVMValueRef, ctor_ty: c.LLVMTypeRef) void {
        const i32_ty = self.cached_i32;
        const ptr_ty = self.cached_ptr;
        var ctor_field_types: [3]c.LLVMTypeRef = .{ i32_ty, ptr_ty, ptr_ty };
        const ctor_struct_ty = c.LLVMStructTypeInContext(self.context, &ctor_field_types, 3, 0);
        var ctor_fields: [3]c.LLVMValueRef = .{
            c.LLVMConstInt(i32_ty, 65535, 0),
            ctor,
            c.LLVMConstNull(ptr_ty),
        };
        const ctor_entry = c.LLVMConstNamedStruct(ctor_struct_ty, &ctor_fields, 3);

        const existing_z = "llvm.global_ctors";
        const existing = c.LLVMGetNamedGlobal(self.llvm_module, existing_z);
        if (existing != null) {
            const existing_init = c.LLVMGetInitializer(existing);
            const existing_arr_ty = c.LLVMGlobalGetValueType(existing);
            const old_count = c.LLVMGetArrayLength(existing_arr_ty);
            const new_count: c_uint = old_count + 1;
            var new_entries = std.ArrayList(c.LLVMValueRef).empty;
            defer new_entries.deinit(self.alloc);
            var i: c_uint = 0;
            while (i < old_count) : (i += 1) {
                new_entries.append(self.alloc, c.LLVMGetAggregateElement(existing_init, i)) catch unreachable;
            }
            new_entries.append(self.alloc, ctor_entry) catch unreachable;
            const new_arr_ty = c.LLVMArrayType2(ctor_struct_ty, new_count);
            const new_init = c.LLVMConstArray2(ctor_struct_ty, new_entries.items.ptr, new_count);
            const new_global = c.LLVMAddGlobal(self.llvm_module, new_arr_ty, "llvm.global_ctors.new");
            c.LLVMSetInitializer(new_global, new_init);
            c.LLVMSetLinkage(new_global, c.LLVMAppendingLinkage);
            c.LLVMSetValueName2(existing, "llvm.global_ctors.old", "llvm.global_ctors.old".len);
            c.LLVMSetValueName2(new_global, "llvm.global_ctors", "llvm.global_ctors".len);
            c.LLVMDeleteGlobal(existing);
        } else {
            const ctors_arr_ty = c.LLVMArrayType2(ctor_struct_ty, 1);
            var ctor_entries: [1]c.LLVMValueRef = .{ctor_entry};
            const ctors_init = c.LLVMConstArray2(ctor_struct_ty, &ctor_entries, 1);
            const ctors_global = c.LLVMAddGlobal(self.llvm_module, ctors_arr_ty, "llvm.global_ctors");
            c.LLVMSetInitializer(ctors_global, ctors_init);
            c.LLVMSetLinkage(ctors_global, c.LLVMAppendingLinkage);
        }

        // ORC JIT: inject a direct call at the end of main's prelude
        // (past any existing init calls).
        const main_z = "main";
        const main_fn = c.LLVMGetNamedFunction(self.llvm_module, main_z);
        if (main_fn != null) {
            const entry_bb = c.LLVMGetEntryBasicBlock(main_fn);
            var insert_before = c.LLVMGetFirstInstruction(entry_bb);
            while (insert_before != null) : (insert_before = c.LLVMGetNextInstruction(insert_before)) {
                if (c.LLVMGetInstructionOpcode(insert_before) != c.LLVMCall) break;
            }
            if (insert_before != null) {
                c.LLVMPositionBuilderBefore(self.builder, insert_before);
            } else {
                c.LLVMPositionBuilderAtEnd(self.builder, entry_bb);
            }
            var no_args: [0]c.LLVMValueRef = .{};
            _ = c.LLVMBuildCall2(self.builder, ctor_ty, ctor, &no_args, 0, "");
        }
    }

    /// On macOS, emit a startup helper that chdir's to the .app bundle's
    /// `Contents/Resources` directory when the executable lives inside a
    /// `.app/Contents/MacOS/` path. Lets relative asset paths like
    /// `assets/foo.png` resolve correctly when Finder/`open` launches the
    /// binary with CWD=/.
    ///
    /// Bundled binary: strstr finds the marker, chdir succeeds.
    /// CLI binary / `sx run`: strstr returns null, the function no-ops.
    ///
    /// The call is injected at the very start of `main()` (matching the
    /// pattern used for the Obj-C selector init) rather than registered
    /// via `@llvm.global_ctors`, so the ORC JIT path runs it too without
    /// special handling.
    fn emitMacosBundleChdir(self: *LLVMEmitter) void {
        if (!self.target_config.is_aot) return;
        if (!self.target_config.isMacOS()) return;

        const ptr_ty = self.cached_ptr;
        const i32_ty = self.cached_i32;
        const i8_ty = self.cached_i8;
        const void_ty = self.cached_void;

        // Declare libc externs (re-use if already declared).
        var ns_params: [2]c.LLVMTypeRef = .{ ptr_ty, ptr_ty };
        const ns_ty = c.LLVMFunctionType(i32_ty, &ns_params, 2, 0);
        var ns_fn = c.LLVMGetNamedFunction(self.llvm_module, "_NSGetExecutablePath");
        if (ns_fn == null) ns_fn = c.LLVMAddFunction(self.llvm_module, "_NSGetExecutablePath", ns_ty);

        var chdir_params: [1]c.LLVMTypeRef = .{ptr_ty};
        const chdir_ty = c.LLVMFunctionType(i32_ty, &chdir_params, 1, 0);
        var chdir_fn = c.LLVMGetNamedFunction(self.llvm_module, "chdir");
        if (chdir_fn == null) chdir_fn = c.LLVMAddFunction(self.llvm_module, "chdir", chdir_ty);

        var ss_params: [2]c.LLVMTypeRef = .{ ptr_ty, ptr_ty };
        const ss_ty = c.LLVMFunctionType(ptr_ty, &ss_params, 2, 0);
        var ss_fn = c.LLVMGetNamedFunction(self.llvm_module, "strstr");
        if (ss_fn == null) ss_fn = c.LLVMAddFunction(self.llvm_module, "strstr", ss_ty);

        var sc_params: [2]c.LLVMTypeRef = .{ ptr_ty, ptr_ty };
        const sc_ty = c.LLVMFunctionType(ptr_ty, &sc_params, 2, 0);
        var sc_fn = c.LLVMGetNamedFunction(self.llvm_module, "strcpy");
        if (sc_fn == null) sc_fn = c.LLVMAddFunction(self.llvm_module, "strcpy", sc_ty);

        var no_params: [0]c.LLVMTypeRef = .{};
        const ctor_ty = c.LLVMFunctionType(void_ty, &no_params, 0, 0);
        const ctor = c.LLVMAddFunction(self.llvm_module, "__sx_macos_bundle_chdir", ctor_ty);
        c.LLVMSetLinkage(ctor, c.LLVMInternalLinkage);

        const entry_bb = c.LLVMAppendBasicBlockInContext(self.context, ctor, "entry");
        const found_bb = c.LLVMAppendBasicBlockInContext(self.context, ctor, "found");
        const done_bb  = c.LLVMAppendBasicBlockInContext(self.context, ctor, "done");

        c.LLVMPositionBuilderAtEnd(self.builder, entry_bb);

        const buf_ty = c.LLVMArrayType2(i8_ty, 1024);
        const buf = c.LLVMBuildAlloca(self.builder, buf_ty, "buf");
        const bufsize = c.LLVMBuildAlloca(self.builder, i32_ty, "bufsize");
        _ = c.LLVMBuildStore(self.builder, c.LLVMConstInt(i32_ty, 1024, 0), bufsize);

        var ns_args: [2]c.LLVMValueRef = .{ buf, bufsize };
        _ = c.LLVMBuildCall2(self.builder, ns_ty, ns_fn, &ns_args, 2, "");

        const needle = self.emitCStringGlobal("/Contents/MacOS/", "__sx_macos_chdir_needle");
        const replacement = self.emitCStringGlobal("/Contents/Resources", "__sx_macos_chdir_replacement");

        var ss_args: [2]c.LLVMValueRef = .{ buf, needle };
        const p = c.LLVMBuildCall2(self.builder, ss_ty, ss_fn, &ss_args, 2, "p");

        const is_null = c.LLVMBuildIsNull(self.builder, p, "is_null");
        _ = c.LLVMBuildCondBr(self.builder, is_null, done_bb, found_bb);

        c.LLVMPositionBuilderAtEnd(self.builder, found_bb);
        var sc_args: [2]c.LLVMValueRef = .{ p, replacement };
        _ = c.LLVMBuildCall2(self.builder, sc_ty, sc_fn, &sc_args, 2, "");
        var chdir_args: [1]c.LLVMValueRef = .{buf};
        _ = c.LLVMBuildCall2(self.builder, chdir_ty, chdir_fn, &chdir_args, 1, "");
        _ = c.LLVMBuildBr(self.builder, done_bb);

        c.LLVMPositionBuilderAtEnd(self.builder, done_bb);
        _ = c.LLVMBuildRetVoid(self.builder);

        // Inject a call at the very start of main(). Matches the
        // emitObjcSelectorInit pattern so the ORC JIT path picks it up
        // without needing `@llvm.global_ctors` plumbing.
        const main_fn = c.LLVMGetNamedFunction(self.llvm_module, "main");
        if (main_fn != null) {
            const main_entry = c.LLVMGetEntryBasicBlock(main_fn);
            const first_inst = c.LLVMGetFirstInstruction(main_entry);
            if (first_inst != null) {
                c.LLVMPositionBuilderBefore(self.builder, first_inst);
            } else {
                c.LLVMPositionBuilderAtEnd(self.builder, main_entry);
            }
            var no_args: [0]c.LLVMValueRef = .{};
            _ = c.LLVMBuildCall2(self.builder, ctor_ty, ctor, &no_args, 0, "");
        }
    }

    /// Return `{cls_slot, mid_slot}` global pair for the
    /// `(name, sig)` literal — created on first lookup, shared across
    /// later `#jni_call` sites with the same literal pair. Both
    /// slots are zero-initialized `ptr`; the call-site lowering does
    /// lazy population on first dispatch.
    fn getOrCreateJniSlots(self: *LLVMEmitter, name: []const u8, sig: []const u8) JniSlotPair {
        // Compose the key from name + a separator + sig. The separator
        // is a byte that can't appear in a JNI method name or signature
        // (NUL), so the same key never collides across distinct pairs.
        const key = std.fmt.allocPrint(self.alloc, "{s}\x00{s}", .{ name, sig }) catch unreachable;
        if (self.jni_slots.get(key)) |existing| {
            self.alloc.free(key);
            return existing;
        }
        const mangled = self.mangleJniKey(name, sig);
        defer self.alloc.free(mangled);
        const cls_name = std.fmt.allocPrintSentinel(self.alloc, "SX_JNI_CLS_{s}", .{mangled}, 0) catch unreachable;
        defer self.alloc.free(cls_name);
        const mid_name = std.fmt.allocPrintSentinel(self.alloc, "SX_JNI_MID_{s}", .{mangled}, 0) catch unreachable;
        defer self.alloc.free(mid_name);
        const cls_slot = c.LLVMAddGlobal(self.llvm_module, self.cached_ptr, cls_name.ptr);
        c.LLVMSetLinkage(cls_slot, c.LLVMInternalLinkage);
        c.LLVMSetInitializer(cls_slot, c.LLVMConstNull(self.cached_ptr));
        const mid_slot = c.LLVMAddGlobal(self.llvm_module, self.cached_ptr, mid_name.ptr);
        c.LLVMSetLinkage(mid_slot, c.LLVMInternalLinkage);
        c.LLVMSetInitializer(mid_slot, c.LLVMConstNull(self.cached_ptr));
        const pair = JniSlotPair{ .cls_slot = cls_slot, .mid_slot = mid_slot };
        self.jni_slots.put(key, pair) catch unreachable;
        return pair;
    }

    /// Build an LLVM-friendly identifier suffix from a JNI
    /// `(method_name, signature)` pair. Non-identifier characters are
    /// rewritten to `_`; the resulting string is unique per pair (the
    /// caller guarantees uniqueness on `(name, sig)`, which we
    /// preserve through the separator between mangled name and sig).
    fn mangleJniKey(self: *LLVMEmitter, name: []const u8, sig: []const u8) []u8 {
        var buf = std.ArrayList(u8).empty;
        for (name) |b| buf.append(self.alloc, if (isIdentByte(b)) b else '_') catch unreachable;
        buf.appendSlice(self.alloc, "__") catch unreachable;
        for (sig) |b| buf.append(self.alloc, if (isIdentByte(b)) b else '_') catch unreachable;
        return buf.toOwnedSlice(self.alloc) catch unreachable;
    }

    /// If `val` is a `{ptr, i64}` slice struct, extract field 0
    /// (the ptr); otherwise return it unchanged. Used by JNI dispatch
    /// to feed string-literal method names + signatures to
    /// `GetMethodID`, which expects raw C strings.
    fn extractSlicePtr(self: *LLVMEmitter, val: c.LLVMValueRef) c.LLVMValueRef {
        const val_ty = c.LLVMTypeOf(val);
        if (c.LLVMGetTypeKind(val_ty) != c.LLVMStructTypeKind) return val;
        if (c.LLVMCountStructElementTypes(val_ty) != 2) return val;
        const f0 = c.LLVMStructGetTypeAtIndex(val_ty, 0);
        if (c.LLVMGetTypeKind(f0) != c.LLVMPointerTypeKind) return val;
        return c.LLVMBuildExtractValue(self.builder, val, 0, "jni.str.ptr");
    }

    /// Load a JNI vtable function pointer at the given offset. `ifs`
    /// is the `JNINativeInterface*` loaded from `JNIEnv*`. Treats the
    /// vtable as an array of opaque `ptr`s and indexes into it.
    fn loadJniFn(self: *LLVMEmitter, ifs: c.LLVMValueRef, offset: u32, name: [*:0]const u8) c.LLVMValueRef {
        const offset_val = c.LLVMConstInt(self.cached_i32, offset, 0);
        var idx = [_]c.LLVMValueRef{offset_val};
        const slot = c.LLVMBuildInBoundsGEP2(self.builder, self.cached_ptr, ifs, &idx, 1, "");
        return c.LLVMBuildLoad2(self.builder, self.cached_ptr, slot, name);
    }

    /// Lazily look up / declare the shared `@objc_msgSend` function.
    /// Cached on the emitter; all `objc_msg_send` instructions hand
    /// LLVMBuildCall2 their own per-call-site function type — the
    /// underlying function value is just an opaque `ptr` symbol.
    fn getObjcMsgSendValue(self: *LLVMEmitter) c.LLVMValueRef {
        if (self.objc_msg_send_value) |v| return v;
        const name_z = "objc_msgSend";
        if (c.LLVMGetNamedFunction(self.llvm_module, name_z)) |existing| {
            self.objc_msg_send_value = existing;
            return existing;
        }
        // Seed with a `(ptr, ptr) -> ptr` shape; opaque pointers mean
        // each call site can override.
        var params: [2]c.LLVMTypeRef = .{ self.cached_ptr, self.cached_ptr };
        const fn_ty = c.LLVMFunctionType(self.cached_ptr, &params, 2, 0);
        const fn_val = c.LLVMAddFunction(self.llvm_module, name_z, fn_ty);
        c.LLVMSetLinkage(fn_val, c.LLVMExternalLinkage);
        self.objc_msg_send_value = fn_val;
        return fn_val;
    }

    /// Compare IR typeSizeBytes against LLVMABISizeOfType for all user-defined types.
    fn verifySizes(self: *LLVMEmitter) void {
        // Skip for wasm32: 4-byte pointers vs IR's assumed 8-byte,
        // so struct sizes will differ. LLVM handles emission correctly.
        if (self.target_config.isWasm32()) return;
        const dl = c.LLVMGetModuleDataLayout(self.llvm_module);
        if (dl == null) return;
        const type_count = self.ir_mod.types.infos.items.len;
        for (TypeId.first_user..type_count) |idx| {
            const ty = TypeId.fromIndex(@intCast(idx));
            const info = self.ir_mod.types.get(ty);
            // Only verify aggregate types where sizing is non-trivial
            switch (info) {
                .@"struct", .@"union", .tagged_union, .tuple => {},
                else => continue,
            }
            const llvm_ty = self.toLLVMType(ty);
            const llvm_size = c.LLVMABISizeOfType(dl, llvm_ty);
            const ir_size = self.ir_mod.types.typeSizeBytes(ty);
            std.debug.assert(llvm_size == ir_size);
        }
    }

    /// The error-set channel of a (possibly failable) type: the set itself for
    /// a pure `-> !` result, or the last tuple slot for `-> (T..., !)`. null if
    /// the type carries no error channel. Mirror of lower.errorChannelOf.
    fn comptimeErrChannel(self: *LLVMEmitter, ty: TypeId) ?TypeId {
        if (ty.isBuiltin()) return null;
        switch (self.ir_mod.types.get(ty)) {
            .error_set => return ty,
            .tuple => |t| {
                if (t.fields.len == 0) return null;
                const last = t.fields[t.fields.len - 1];
                if (last.isBuiltin()) return null;
                return if (self.ir_mod.types.get(last) == .error_set) last else null;
            },
            else => return null,
        }
    }

    /// Inspect a failable `#run` result. On a non-zero error tag, print the
    /// comptime-error diagnostic + return trace, flag compilation failed, and
    /// return null. On success, return the value part (error channel stripped):
    /// `void_val` for a pure failable, the lone value for `(T, !)`, the
    /// value-tuple for multi-value. (E5.2)
    fn checkComptimeFailable(self: *LLVMEmitter, result: Value, fail_ty: TypeId, label: []const u8) ?Value {
        const channel = self.comptimeErrChannel(fail_ty) orelse return result;
        var tag: u32 = 0;
        var success: Value = .void_val;
        if (channel == fail_ty) {
            // pure failable — the result IS the error tag (u32)
            tag = switch (result) {
                .int => |v| @truncate(@as(u64, @bitCast(v))),
                else => 0,
            };
        } else {
            // value-carrying — the result is the `{values..., tag}` aggregate
            const fields = switch (result) {
                .aggregate => |f| f,
                else => return result,
            };
            if (fields.len == 0) return result;
            tag = switch (fields[fields.len - 1]) {
                .int => |v| @truncate(@as(u64, @bitCast(v))),
                else => 0,
            };
            success = if (fields.len == 2) fields[0] else .{ .aggregate = fields[0 .. fields.len - 1] };
        }
        if (tag == 0) {
            sx_trace_clear();
            return success;
        }
        self.reportComptimeEscape(label, tag);
        sx_trace_clear();
        self.comptime_failed = true;
        return null;
    }

    /// Print the locked comptime-escape diagnostic: the raised tag name, the
    /// resolved return trace from the thread-local buffer, and a help line.
    fn reportComptimeEscape(self: *LLVMEmitter, label: []const u8, tag: u32) void {
        const tname = self.ir_mod.types.tags.getName(tag);
        std.debug.print("error: comptime `#run` ({s}) raised an unhandled error: error.{s}\n", .{ label, tname });
        const n = sx_trace_len();
        if (n > 0) {
            std.debug.print("error return trace (most recent call last):\n", .{});
            var i: u32 = 0;
            while (i < n) : (i += 1) {
                const packed_frame = sx_trace_frame_at(i);
                const fid: u32 = @intCast(packed_frame >> 32);
                const offset: u32 = @truncate(packed_frame);
                if (fid >= self.ir_mod.functions.items.len) continue;
                const func = self.ir_mod.getFunction(FuncId.fromIndex(fid));
                const fname = self.ir_mod.types.getString(func.name);
                const file_full = func.source_file orelse "";
                const file = std.fs.path.basename(file_full);
                var line: usize = 1;
                var col: usize = 1;
                if (self.import_sources) |sm| {
                    if (sm.get(file_full)) |src| {
                        const loc = errors.SourceLoc.compute(src, offset);
                        line = loc.line;
                        col = loc.col;
                    }
                }
                std.debug.print("  {s} at {s}:{d}:{d}\n", .{ fname, file, line, col });
            }
        }
        std.debug.print("help: handle it at the `#run` site — `#run <expr> catch e {{ ... }}` or `#run <expr> or <default>`\n", .{});
    }

    /// Run comptime side-effect functions (e.g., `#run main();` at top level).
    /// These are functions marked `is_comptime = true` with void return that
    /// aren't associated with any global. They produce compile-time output.
    fn runComptimeSideEffects(self: *LLVMEmitter) void {
        for (self.ir_mod.functions.items, 0..) |func, i| {
            // `#run expr;` side-effects are the `__run_N` wrappers (global
            // initializers are named after their global and run by emitGlobals;
            // inline `__ct`/`__insert` wrappers run from their call sites). A
            // failable side-effect carries the error channel on `func.ret`.
            if (!func.is_comptime) continue;
            const fname = self.ir_mod.types.getString(func.name);
            if (!std.mem.startsWith(u8, fname, "__run")) continue;

            const func_id = ir_inst.FuncId.fromIndex(@intCast(i));
            var interp_inst = Interpreter.init(self.ir_mod, self.alloc);
            interp_inst.build_config = &self.build_config;
            if (self.import_sources) |sm| interp_inst.setSourceMap(sm);
            sx_trace_clear();
            const result = interp_inst.call(func_id, &.{}) catch Value.void_val;
            // Route #run `print` output to fd 1 so it joins the
            // JIT-executed runtime's stream. Same call site shape as
            // `core.flushInterpOutput` — see issue-0047.
            if (interp_inst.output.items.len > 0) {
                _ = std.c.write(1, interp_inst.output.items.ptr, interp_inst.output.items.len);
            }
            // A bare failable `#run f();` whose error escapes → diagnostic + halt.
            if (self.comptimeErrChannel(func.ret) != null) {
                _ = self.checkComptimeFailable(result, func.ret, "top-level statement");
            }
            interp_inst.deinit();
        }
    }

    fn emitGlobals(self: *LLVMEmitter) void {
        for (self.ir_mod.globals.items, 0..) |global, i| {
            const name = self.ir_mod.types.getString(global.name);
            const llvm_ty = self.toLLVMType(global.ty);
            const name_z = self.alloc.dupeZ(u8, name) catch continue;
            defer self.alloc.free(name_z);

            const llvm_global = c.LLVMAddGlobal(self.llvm_module, llvm_ty, name_z.ptr);

            // Extern globals (`<name> : <type> #foreign;`) resolve at link time
            // to a libSystem / framework symbol — no initializer, default linkage.
            if (global.is_extern) {
                c.LLVMSetLinkage(llvm_global, c.LLVMExternalLinkage);
                self.global_map.put(@intCast(i), llvm_global) catch {};
                continue;
            }

            c.LLVMSetLinkage(llvm_global, c.LLVMInternalLinkage);

            if (global.is_thread_local) {
                c.LLVMSetThreadLocal(llvm_global, 1);
            }

            // Evaluate comptime initializer if present
            if (global.comptime_func) |func_id| {
                var interp_inst = Interpreter.init(self.ir_mod, self.alloc);
                interp_inst.build_config = &self.build_config;
                if (self.import_sources) |sm| interp_inst.setSourceMap(sm);
                Interpreter.last_bail_op = null;
                Interpreter.last_bail_builtin = null;
                Interpreter.last_bail_detail = null;
                sx_trace_clear();
                const result = interp_inst.call(func_id, &.{}) catch |err| blk: {
                    // Surface the bail loudly instead of silently filling
                    // the const with zero. Stale state from a previous
                    // comptime function would otherwise hide the error.
                    const op = Interpreter.last_bail_op orelse "<unknown>";
                    const detail = Interpreter.last_bail_detail orelse "";
                    const sep: []const u8 = if (detail.len > 0) ": " else "";
                    const gname = self.ir_mod.types.getString(global.name);
                    std.debug.print("error: comptime init of '{s}' failed: {s} (op={s}{s}{s})\n", .{ gname, @errorName(err), op, sep, detail });
                    break :blk .void_val;
                };
                // A bare failable `NAME :: #run f();`: the comptime function
                // returns the failable tuple; split it. Escaping error →
                // diagnostic + halt (leave the global undef); success → the
                // value part materializes into the global's success type (E5.2).
                const cf_ret = self.ir_mod.getFunction(func_id).ret;
                var init_value = result;
                if (self.comptimeErrChannel(cf_ret) != null) {
                    if (self.checkComptimeFailable(result, cf_ret, self.ir_mod.types.getString(global.name))) |succ| {
                        init_value = succ;
                    } else {
                        c.LLVMSetInitializer(llvm_global, c.LLVMGetUndef(llvm_ty));
                        self.global_map.put(@intCast(i), llvm_global) catch {};
                        continue;
                    }
                }
                const init_val = self.valueToLLVMConst(init_value, global.ty, &interp_inst, self.ir_mod.types.getString(global.name));
                c.LLVMSetInitializer(llvm_global, init_val);
            } else if (global.init_val) |iv| {
                const init_val = switch (iv) {
                    .int => |v| c.LLVMConstInt(llvm_ty, @bitCast(v), 1),
                    .float => |v| c.LLVMConstReal(llvm_ty, v),
                    .boolean => |v| c.LLVMConstInt(llvm_ty, @intFromBool(v), 0),
                    .string => |sid| self.emitConstStringGlobal(self.ir_mod.types.getString(sid)),
                    .aggregate => |agg| self.emitConstAggregate(agg, llvm_ty),
                    .vtable => c.LLVMConstNull(llvm_ty), // placeholder — initialized in initVtableGlobals after function declarations
                    else => c.LLVMConstNull(llvm_ty),
                };
                c.LLVMSetInitializer(llvm_global, init_val);
            } else {
                c.LLVMSetInitializer(llvm_global, c.LLVMConstNull(llvm_ty));
            }

            self.global_map.put(@intCast(i), llvm_global) catch {};
        }
    }

    /// Initialize vtable + aggregate-with-func_ref globals with function
    /// pointer constants. Must run after Pass 1 (function declarations) so
    /// func_map is populated — that's why these globals get a placeholder
    /// initializer in `emitGlobals` and we fix them up here.
    fn initVtableGlobals(self: *LLVMEmitter) void {
        for (self.ir_mod.globals.items, 0..) |global, i| {
            const iv = global.init_val orelse continue;
            const llvm_global = self.global_map.get(@intCast(i)) orelse continue;
            const llvm_ty = self.toLLVMType(global.ty);

            switch (iv) {
                .vtable => |func_ids| {
                    var field_vals = std.ArrayList(c.LLVMValueRef).empty;
                    defer field_vals.deinit(self.alloc);
                    for (func_ids) |fid| {
                        const llvm_func = self.func_map.get(fid.index()) orelse {
                            field_vals.append(self.alloc, c.LLVMConstNull(self.cached_ptr)) catch unreachable;
                            continue;
                        };
                        field_vals.append(self.alloc, llvm_func) catch unreachable;
                    }
                    const init_val = c.LLVMConstNamedStruct(llvm_ty, field_vals.items.ptr, @intCast(field_vals.items.len));
                    c.LLVMSetInitializer(llvm_global, init_val);
                    c.LLVMSetGlobalConstant(llvm_global, 1);
                },
                .aggregate => |agg| {
                    // Re-emit. The first pass in `emitGlobals` already ran,
                    // but func_ref leaves resolved to null then (func_map
                    // wasn't populated yet). Now they resolve properly.
                    const init_val = self.emitConstAggregate(agg, llvm_ty);
                    c.LLVMSetInitializer(llvm_global, init_val);
                },
                else => continue,
            }
        }
    }

    /// Read `len` bytes from `addr` in the current process. Used to lift
    /// comptime-evaluated heap data into a static binary constant — the
    /// interp ran in this process, so any libc-malloc'd buffer it
    /// produced is still mapped and readable. Returns `null` on a
    /// null/zero address (callers handle empty-slice as a special case
    /// before calling this).
    fn readHostBytes(addr: usize, len: usize) ?[]const u8 {
        if (addr == 0) return null;
        const ptr: [*]const u8 = @ptrFromInt(addr);
        return ptr[0..len];
    }

    /// Serialize an interp `Value` to an LLVM constant for use as a static
    /// global initializer. `ty` is the IR-level type of the destination;
    /// the LLVM type is derived from it. `interp` gives access to the
    /// interpreter's heap so heap_ptr values can be walked. `global_name`
    /// is included in any diagnostic the path produces so the user can
    /// locate the offending `#run` site.
    ///
    /// Returns `LLVMGetUndef` on bail — the build continues so adjacent
    /// constants can still emit, but the diagnostic makes the problem clear.
    fn valueToLLVMConst(
        self: *LLVMEmitter,
        val: Value,
        ty: TypeId,
        interp: *const Interpreter,
        global_name: []const u8,
    ) c.LLVMValueRef {
        const llvm_ty = self.toLLVMType(ty);
        return switch (val) {
            .int => |v| blk: {
                // Host-pointer-as-int trap: the interp marshals raw pointers
                // (libc-malloc'd buffers, etc.) into a .int that holds the
                // host address. When that address is meant for a `ptr` slot
                // in the destination type, emitting `LLVMConstInt` against
                // the ptr type silently produces a malformed `i0 0`. The
                // string/slice paths above handle this case by reading the
                // pointed-to bytes; anything else with an int landing in a
                // ptr slot is a Phase-1.4a heap-walk case we don't yet
                // know how to serialize.
                const kind = c.LLVMGetTypeKind(llvm_ty);
                if (kind == c.LLVMPointerTypeKind) {
                    std.debug.print(
                        "error: comptime init of '{s}' produced a raw integer for a pointer field — needs IR-typed heap-walk serialization (Phase 1.4a heap-walk follow-up)\n",
                        .{global_name},
                    );
                    break :blk c.LLVMGetUndef(llvm_ty);
                }
                break :blk c.LLVMConstInt(llvm_ty, @bitCast(v), 1);
            },
            .float => |v| c.LLVMConstReal(llvm_ty, v),
            .boolean => |v| c.LLVMConstInt(llvm_ty, @intFromBool(v), 0),
            .null_val => c.LLVMConstNull(llvm_ty),
            .void_val, .undef => c.LLVMGetUndef(llvm_ty),
            .func_ref => |fid| self.func_map.get(fid.index()) orelse c.LLVMConstNull(llvm_ty),
            .string => |s| self.emitConstStringGlobal(s),
            .aggregate => |fields| self.serializeAggregateValue(fields, ty, interp, global_name),
            // The remaining Value variants cannot become static binary
            // constants outside of a fat-pointer aggregate. Bail loudly.
            // (`heap_ptr` / `byte_ptr` / `int → ptr` are handled inside
            // `serializeAggregateValue` when they appear in a string or
            // slice fat-pointer's data field.)
            .heap_ptr, .byte_ptr, .slot_ptr, .closure, .type_tag => blk: {
                std.debug.print(
                    "error: comptime init of '{s}' produced a {s} value, which cannot be serialized as a static constant\n",
                    .{ global_name, @tagName(val) },
                );
                break :blk c.LLVMGetUndef(llvm_ty);
            },
        };
    }

    /// Helper for `valueToLLVMConst` — serialize an aggregate value
    /// against an IR TypeId. Splits on the type:
    ///
    ///   - `string` / `slice` — fat pointer `{ data, len }`. The data
    ///     field can be a heap_ptr (interp-managed memory), byte_ptr
    ///     (raw host address), int (same), or string literal. The len
    ///     field is consulted to know how many bytes to capture from
    ///     the data. Bytes are emitted as a private global byte array
    ///     and the aggregate constant points at it.
    ///   - `struct` — walk the IR field types in lockstep with the
    ///     value fields; recurse per field with its declared TypeId.
    ///   - `array` — walk elements with the array's element TypeId.
    fn serializeAggregateValue(
        self: *LLVMEmitter,
        fields: []const Value,
        ty: TypeId,
        interp: *const Interpreter,
        global_name: []const u8,
    ) c.LLVMValueRef {
        const llvm_ty = self.toLLVMType(ty);

        // Fat-pointer types: extract len, then read bytes from the data
        // field's address (whatever flavour the interp produced for it).
        const is_string = (ty == .string);
        const is_slice = !ty.isBuiltin() and self.ir_mod.types.get(ty) == .slice;
        if ((is_string or is_slice) and fields.len == 2) {
            const data = fields[0];
            const len_i = fields[1].asInt() orelse {
                std.debug.print(
                    "error: comptime init of '{s}' produced a fat-pointer aggregate whose len field is not an integer\n",
                    .{global_name},
                );
                return c.LLVMGetUndef(llvm_ty);
            };
            const len: usize = @intCast(len_i);

            const bytes_opt: ?[]const u8 = switch (data) {
                .heap_ptr => |hp| blk: {
                    const mem = interp.heapSlice(hp) orelse break :blk null;
                    break :blk if (len <= mem.len) mem[0..len] else null;
                },
                .byte_ptr => |addr| readHostBytes(addr, len),
                .int => |v| blk: {
                    if (v == 0 and len == 0) break :blk &.{}; // empty slice
                    if (v == 0) break :blk null;
                    break :blk readHostBytes(@as(usize, @bitCast(v)), len);
                },
                .string => |s| if (len <= s.len) s[0..len] else null,
                else => null,
            };

            const bytes = bytes_opt orelse {
                std.debug.print(
                    "error: comptime init of '{s}' produced a fat-pointer aggregate whose data field ({s}) cannot be resolved to {} bytes — needs Phase 1.4a heap-walk for this shape\n",
                    .{ global_name, @tagName(data), len },
                );
                return c.LLVMGetUndef(llvm_ty);
            };

            return self.emitConstStringGlobal(bytes);
        }

        // Generic struct: walk IR fields by their declared TypeIds.
        if (!ty.isBuiltin()) {
            const info = self.ir_mod.types.get(ty);
            if (info == .@"struct") {
                const ir_fields = info.@"struct".fields;
                if (ir_fields.len != fields.len) {
                    std.debug.print(
                        "error: comptime init of '{s}' produced aggregate with {} fields but struct '{s}' expects {}\n",
                        .{ global_name, fields.len, self.ir_mod.types.getString(info.@"struct".name), ir_fields.len },
                    );
                    return c.LLVMGetUndef(llvm_ty);
                }
                var field_vals = std.ArrayList(c.LLVMValueRef).empty;
                defer field_vals.deinit(self.alloc);
                for (ir_fields, fields) |ir_field, fv| {
                    field_vals.append(self.alloc, self.valueToLLVMConst(fv, ir_field.ty, interp, global_name)) catch unreachable;
                }
                return c.LLVMConstNamedStruct(llvm_ty, field_vals.items.ptr, @intCast(field_vals.items.len));
            }
            if (info == .array) {
                const elem_ty = info.array.element;
                const llvm_elem_ty = self.toLLVMType(elem_ty);
                var elem_vals = std.ArrayList(c.LLVMValueRef).empty;
                defer elem_vals.deinit(self.alloc);
                for (fields) |fv| {
                    elem_vals.append(self.alloc, self.valueToLLVMConst(fv, elem_ty, interp, global_name)) catch unreachable;
                }
                return c.LLVMConstArray2(llvm_elem_ty, elem_vals.items.ptr, @intCast(elem_vals.items.len));
            }
        }

        std.debug.print(
            "error: comptime init of '{s}' produced an aggregate but the destination type ({s}) is neither struct, array, string, nor slice\n",
            .{ global_name, self.ir_mod.types.typeName(ty) },
        );
        return c.LLVMGetUndef(llvm_ty);
    }

    // ── Function declaration ────────────────────────────────────────

    fn declareFunction(self: *LLVMEmitter, func: *const Function, func_idx: u32) void {
        const name = self.ir_mod.types.getString(func.name);

        // Skip builtins that are declared via getOrDeclare* with correct C-compatible types.
        // The IR lowering creates extern stubs with IR types (e.g. memset → void return),
        // but the C ABI may differ (memset returns ptr). Let getOrDeclare* handle these.
        if (func.is_extern and isBuiltinLibcName(name)) {
            // Still register in func_map so call resolution works
            const builtin_fn = self.getOrDeclareBuiltinByName(name);
            if (builtin_fn) |bf| {
                self.func_map.put(func_idx, bf) catch unreachable;
                return;
            }
        }

        const is_main = std.mem.eql(u8, name, "main");

        // main always returns i32 at the LLVM level (JIT expects it)
        const raw_ret_ty = self.toLLVMType(func.ret);
        const needs_c_abi = func.is_extern or func.call_conv == .c;
        // sret return: C-ABI functions returning a >16 B non-HFA struct
        // use the indirect-return convention (caller allocates space,
        // passes its pointer as a hidden first arg with `sret(<T>)`,
        // function writes through and returns void). Distinct from
        // small-struct register coercion (i64 / [2 x i64]) and HFA.
        const uses_sret = needs_c_abi and !is_main and self.needsByval(func.ret, raw_ret_ty);
        const ret_ty = if (is_main) self.cached_i32
            else if (uses_sret) self.cached_void
            else if (needs_c_abi) self.abiCoerceParamTypeEx(func.ret, raw_ret_ty, func.is_extern)
            else raw_ret_ty;

        // Build parameter types — apply C ABI coercion for foreign/callconv(.c) functions.
        // When uses_sret, prepend the sret pointer at index 0.
        const sret_offset: usize = if (uses_sret) 1 else 0;
        const param_count: c_uint = @intCast(func.params.len + sret_offset);
        const param_types = self.alloc.alloc(c.LLVMTypeRef, func.params.len + sret_offset) catch unreachable;
        defer self.alloc.free(param_types);
        if (uses_sret) param_types[0] = self.cached_ptr;
        for (func.params, 0..) |param, j| {
            const llvm_ty = self.toLLVMType(param.ty);
            param_types[j + sret_offset] = if (needs_c_abi) self.abiCoerceParamTypeEx(param.ty, llvm_ty, func.is_extern) else llvm_ty;
        }

        const is_var_arg: c_int = if (func.is_variadic) 1 else 0;
        const fn_type = c.LLVMFunctionType(ret_ty, param_types.ptr, param_count, is_var_arg);
        const name_z = self.alloc.dupeZ(u8, name) catch unreachable;
        defer self.alloc.free(name_z);

        const llvm_func = c.LLVMAddFunction(self.llvm_module, name_z.ptr, fn_type);

        // sret(<RetType>) attribute on the prepended pointer param.
        // LLVMAttributeIndex 1 = first parameter (0 = return value).
        if (uses_sret) {
            const sret_kind = c.LLVMGetEnumAttributeKindForName("sret", 4);
            const sret_attr = c.LLVMCreateTypeAttribute(self.context, sret_kind, raw_ret_ty);
            const param1_idx: c.LLVMAttributeIndex = @bitCast(@as(i32, 1));
            c.LLVMAddAttributeAtIndex(llvm_func, param1_idx, sret_attr);
        }

        // Set linkage
        switch (func.linkage) {
            .external => c.LLVMSetLinkage(llvm_func, c.LLVMExternalLinkage),
            .internal => c.LLVMSetLinkage(llvm_func, c.LLVMInternalLinkage),
            .private => c.LLVMSetLinkage(llvm_func, c.LLVMPrivateLinkage),
        }

        // Set calling convention
        if (func.call_conv == .c) {
            c.LLVMSetFunctionCallConv(llvm_func, c.LLVMCCallConv);
        }

        // Add frame-pointer and nounwind attributes for correct ARM64 codegen
        {
            const fp_kind = "frame-pointer";
            const fp_val = "all";
            const fp_attr = c.LLVMCreateStringAttribute(
                self.context,
                fp_kind.ptr,
                @intCast(fp_kind.len),
                fp_val.ptr,
                @intCast(fp_val.len),
            );
            const func_idx_attr: c.LLVMAttributeIndex = @bitCast(@as(i32, -1));
            c.LLVMAddAttributeAtIndex(llvm_func, func_idx_attr, fp_attr);

            // Add nounwind
            const nounwind_id = c.LLVMGetEnumAttributeKindForName("nounwind", 8);
            const nounwind_attr = c.LLVMCreateEnumAttribute(self.context, nounwind_id, 0);
            c.LLVMAddAttributeAtIndex(llvm_func, func_idx_attr, nounwind_attr);
        }

        // Apple ARM64 ABI for >16B non-HFA composites: pass by reference
        // via a pointer in the next int register (NOT via LLVM's `byval`
        // attribute, which lowers the struct on the stack — incompatible
        // with what `clang` emits and what foreign C callees expect).
        // abiCoerceParamType returned `ptr` for these slots, so the formal
        // param IS a plain pointer; the prologue loads the struct back.

        self.func_map.put(func_idx, llvm_func) catch unreachable;
    }

    // ── Function body emission ──────────────────────────────────────

    fn emitFunction(self: *LLVMEmitter, func: *const Function, func_idx: u32) void {
        const llvm_func = self.func_map.get(func_idx) orelse unreachable;
        const name = self.ir_mod.types.getString(func.name);
        self.current_func_is_main = std.mem.eql(u8, name, "main");
        self.current_func_idx = func_idx;
        // Source file for span resolution — needed by `.trace_frame` even when
        // DWARF is off (traces gate on opt level only, not on a source map).
        self.current_func_file = func.source_file orelse self.main_file;

        // DWARF: describe this function and make it the scope for the
        // per-instruction locations set in emitInst (no-op if off).
        self.beginFunctionDebug(func, llvm_func, name);

        // Clear ref_map and pre-map parameter refs
        self.ref_map.clearRetainingCapacity();
        self.ref_counter = 0;

        // Refs 0..N-1 are function parameters (matching the IR convention)
        for (0..func.params.len) |pi| {
            const param_val = c.LLVMGetParam(llvm_func, @intCast(pi));
            self.mapRef(param_val);
        }

        // Create all basic blocks first (so branches can reference them)
        for (func.blocks.items, 0..) |block, bi| {
            const block_name = self.ir_mod.types.getString(block.name);
            const block_name_z = self.alloc.dupeZ(u8, block_name) catch unreachable;
            defer self.alloc.free(block_name_z);
            const bb = c.LLVMAppendBasicBlockInContext(self.context, llvm_func, block_name_z.ptr);
            const block_key = makeBlockKey(func_idx, @intCast(bi));
            self.block_map.put(block_key, bb) catch unreachable;
        }

        // byval params arrive as `ptr` in LLVM but the IR body expects struct values.
        // At entry, load each byval param into a struct SSA value and re-map its ref.
        const needs_c_abi = func.is_extern or func.call_conv == .c;
        if (needs_c_abi and func.blocks.items.len > 0) {
            const entry_key = makeBlockKey(func_idx, 0);
            const entry_bb = self.block_map.get(entry_key) orelse unreachable;
            c.LLVMPositionBuilderAtEnd(self.builder, entry_bb);
            for (func.params, 0..) |param, pi| {
                const raw_llvm_ty = self.toLLVMType(param.ty);
                if (self.needsByval(param.ty, raw_llvm_ty)) {
                    const ptr_val = c.LLVMGetParam(llvm_func, @intCast(pi));
                    const loaded = c.LLVMBuildLoad2(self.builder, raw_llvm_ty, ptr_val, "byval.load");
                    self.ref_map.put(@intCast(pi), loaded) catch unreachable;
                }
            }
        }

        // Clear pending phis for this function
        self.pending_phis.clearRetainingCapacity();

        // Emit instructions for each block — use first_ref to sync ref numbering
        for (func.blocks.items, 0..) |block, bi| {
            const block_key = makeBlockKey(func_idx, @intCast(bi));
            const bb = self.block_map.get(block_key) orelse unreachable;
            c.LLVMPositionBuilderAtEnd(self.builder, bb);

            // Reset ref_counter to this block's actual starting ref
            // (blocks may not be in emission order due to nested control flow)
            self.ref_counter = block.first_ref;

            for (block.insts.items, 0..) |instruction, inst_i| {
                _ = inst_i;
                self.emitInst(&instruction, func_idx);
            }
        }

        // Fixup PHI nodes: scan all blocks for branches that pass args
        self.fixupPhiNodes(func, func_idx);

        // DWARF: leave no stale location for the next function.
        self.endFunctionDebug();
    }

    /// After emitting all blocks, fill in PHI incoming values from branch args.
    fn fixupPhiNodes(self: *LLVMEmitter, func: *const Function, func_idx: u32) void {
        if (self.pending_phis.items.len == 0) return;

        for (func.blocks.items, 0..) |block, bi| {
            const src_key = makeBlockKey(func_idx, @intCast(bi));
            const src_bb = self.block_map.get(src_key) orelse continue;

            for (block.insts.items) |instruction| {
                switch (instruction.op) {
                    .br => |branch| {
                        self.addPhiIncoming(branch.target, branch.args, src_bb);
                    },
                    .cond_br => |cb| {
                        self.addPhiIncoming(cb.then_target, cb.then_args, src_bb);
                        self.addPhiIncoming(cb.else_target, cb.else_args, src_bb);
                    },
                    .switch_br => |sw| {
                        for (sw.cases) |case| {
                            self.addPhiIncoming(case.target, case.args, src_bb);
                        }
                        self.addPhiIncoming(sw.default, sw.default_args, src_bb);
                    },
                    else => {},
                }
            }
        }
    }

    fn addPhiIncoming(self: *LLVMEmitter, target: BlockId, args: []const Ref, src_bb: c.LLVMBasicBlockRef) void {
        for (args, 0..) |arg, pi| {
            const val = self.resolveRef(arg) orelse continue;
            // Find the matching pending phi
            for (self.pending_phis.items) |pp| {
                if (pp.block_id.index() == target.index() and pp.param_index == pi) {
                    var incoming_vals = [1]c.LLVMValueRef{val};
                    var incoming_bbs = [1]c.LLVMBasicBlockRef{src_bb};
                    c.LLVMAddIncoming(pp.phi, &incoming_vals, &incoming_bbs, 1);
                    break;
                }
            }
        }
    }

    // ── Instruction emission ────────────────────────────────────────

    fn emitInst(self: *LLVMEmitter, instruction: *const Inst, func_idx: u32) void {
        // DWARF: stamp every LLVM instruction this op emits with the sx
        // source location (no-op when debug info is off).
        self.setInstDebugLocation(instruction.span);
        switch (instruction.op) {
            // ── Constants ───────────────────────────────────────────
            .const_int => |val| {
                const ty = self.toLLVMType(instruction.ty);
                const kind = c.LLVMGetTypeKind(ty);
                const llvm_val = if (kind == c.LLVMIntegerTypeKind)
                    c.LLVMConstInt(ty, @bitCast(val), 1)
                else if (kind == c.LLVMPointerTypeKind)
                    c.LLVMConstNull(ty)
                else
                    // void or other non-integer type: emit i64 0 as unused placeholder
                    c.LLVMConstInt(c.LLVMInt64TypeInContext(self.context), 0, 0);
                self.mapRef(llvm_val);
            },
            .const_float => |val| {
                const ty = self.toLLVMType(instruction.ty);
                const llvm_val = c.LLVMConstReal(ty, val);
                self.mapRef(llvm_val);
            },
            .const_bool => |val| {
                const llvm_val = c.LLVMConstInt(self.cached_i1, @intFromBool(val), 0);
                self.mapRef(llvm_val);
            },
            .is_comptime => {
                // Compiled code is never the comptime interpreter → constant
                // `false`. A `if is_comptime() { … }` branch becomes dead.
                self.mapRef(c.LLVMConstInt(self.cached_i1, 0, 0));
            },
            .interp_print_frames => {
                // No interpreter stack in compiled code; this only ever sits in
                // a dead `is_comptime()` branch. Emit nothing.
                self.advanceRefCounter();
            },
            .trace_frame => {
                self.mapRef(self.emitTraceFrame(instruction));
            },
            .trace_resolve => |u| {
                // The operand is a `Frame*` stamped in by `.trace_frame` (as
                // i64); reinterpret and load it.
                const raw = self.resolveRef(u.operand);
                const frame_ty = self.getFrameStructType();
                const ptr = c.LLVMBuildIntToPtr(self.builder, raw, self.cached_ptr, "frame.ptr");
                self.mapRef(c.LLVMBuildLoad2(self.builder, frame_ty, ptr, "frame.val"));
            },
            .const_string => |str_id| {
                const str = self.ir_mod.types.getString(str_id);
                const llvm_val = self.emitStringConstant(str);
                self.mapRef(llvm_val);
            },
            .const_null => {
                const ty = if (instruction.ty == .void) self.cached_ptr else self.toLLVMType(instruction.ty);
                const llvm_val = c.LLVMConstNull(ty);
                self.mapRef(llvm_val);
            },
            .const_undef => {
                if (instruction.ty == .void) {
                    // void has no value — map to undef i64 as placeholder
                    self.mapRef(c.LLVMGetUndef(self.cached_i64));
                } else {
                    const ty = self.toLLVMType(instruction.ty);
                    const llvm_val = c.LLVMGetUndef(ty);
                    self.mapRef(llvm_val);
                }
            },
            .const_type => |tid| {
                // Type values are Any-shaped pairs:
                //   { tag = .any.index() (the meta-marker),
                //     value = tid.index() }
                // Lets storage in Any slots, struct fields,
                // `Type`-typed vars, and slice elements all round-
                // trip through the standard Any infrastructure.
                // `case type:` in `any_to_string` matches on
                // tag == `.any.index()`. Runtime `type_name(t)`
                // extracts the value field and indexes into the
                // type-name lookup table.
                const any_ty = self.getAnyStructType();
                const tag = c.LLVMConstInt(self.cached_i64, TypeId.any.index(), 0);
                const val = c.LLVMConstInt(self.cached_i64, tid.index(), 0);
                var result = c.LLVMGetUndef(any_ty);
                result = c.LLVMBuildInsertValue(self.builder, result, tag, 0, "ct.tag");
                result = c.LLVMBuildInsertValue(self.builder, result, val, 1, "ct.val");
                self.mapRef(result);
            },

            // ── Arithmetic ─────────────────────────────────────────
            .add => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                const is_float = isFloatOrVecFloat(instruction.ty, &self.ir_mod.types);
                const result = if (is_float)
                    c.LLVMBuildFAdd(self.builder, lhs, rhs, "fadd")
                else
                    c.LLVMBuildAdd(self.builder, lhs, rhs, "add");
                self.mapRef(result);
            },
            .sub => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                const is_float = isFloatOrVecFloat(instruction.ty, &self.ir_mod.types);
                const result = if (is_float)
                    c.LLVMBuildFSub(self.builder, lhs, rhs, "fsub")
                else
                    c.LLVMBuildSub(self.builder, lhs, rhs, "sub");
                self.mapRef(result);
            },
            .mul => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                const is_float = isFloatOrVecFloat(instruction.ty, &self.ir_mod.types);
                const result = if (is_float)
                    c.LLVMBuildFMul(self.builder, lhs, rhs, "fmul")
                else
                    c.LLVMBuildMul(self.builder, lhs, rhs, "mul");
                self.mapRef(result);
            },
            .div => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                const is_float = isFloatOrVecFloat(instruction.ty, &self.ir_mod.types);
                const result = if (is_float)
                    c.LLVMBuildFDiv(self.builder, lhs, rhs, "fdiv")
                else if (isSignedType(instruction.ty))
                    c.LLVMBuildSDiv(self.builder, lhs, rhs, "sdiv")
                else
                    c.LLVMBuildUDiv(self.builder, lhs, rhs, "udiv");
                self.mapRef(result);
            },
            .mod => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                const is_float = isFloatOrVecFloat(instruction.ty, &self.ir_mod.types);
                const result = if (is_float)
                    c.LLVMBuildFRem(self.builder, lhs, rhs, "fmod")
                else if (isSignedType(instruction.ty))
                    c.LLVMBuildSRem(self.builder, lhs, rhs, "srem")
                else
                    c.LLVMBuildURem(self.builder, lhs, rhs, "urem");
                self.mapRef(result);
            },
            .neg => |un| {
                const operand = self.resolveRef(un.operand);
                const is_float = isFloatOrVecFloat(instruction.ty, &self.ir_mod.types);
                const result = if (is_float)
                    c.LLVMBuildFNeg(self.builder, operand, "fneg")
                else
                    c.LLVMBuildNeg(self.builder, operand, "neg");
                self.mapRef(result);
            },

            // ── Bitwise ────────────────────────────────────────────
            .bit_and => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                self.mapRef(c.LLVMBuildAnd(self.builder, lhs, rhs, "and"));
            },
            .bit_or => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                self.mapRef(c.LLVMBuildOr(self.builder, lhs, rhs, "or"));
            },
            .bit_xor => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                self.mapRef(c.LLVMBuildXor(self.builder, lhs, rhs, "xor"));
            },
            .bit_not => |un| {
                const operand = self.resolveRef(un.operand);
                self.mapRef(c.LLVMBuildNot(self.builder, operand, "not"));
            },
            .shl => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                self.mapRef(c.LLVMBuildShl(self.builder, lhs, rhs, "shl"));
            },
            .shr => |bin| {
                var lhs = self.resolveRef(bin.lhs);
                var rhs = self.resolveRef(bin.rhs);
                self.matchBinOpTypes(&lhs, &rhs, instruction.ty);
                // Use arithmetic shift right for signed, logical for unsigned
                const result = if (isSignedType(instruction.ty))
                    c.LLVMBuildAShr(self.builder, lhs, rhs, "ashr")
                else
                    c.LLVMBuildLShr(self.builder, lhs, rhs, "lshr");
                self.mapRef(result);
            },

            // ── Comparisons ───────────────────────────────────────
            .cmp_eq => |bin| self.emitCmp(bin, instruction.ty, c.LLVMIntEQ, c.LLVMRealOEQ),
            .cmp_ne => |bin| self.emitCmp(bin, instruction.ty, c.LLVMIntNE, c.LLVMRealONE),
            .cmp_lt => |bin| self.emitCmpOrdered(bin, instruction.ty, c.LLVMIntSLT, c.LLVMIntULT, c.LLVMRealOLT),
            .cmp_le => |bin| self.emitCmpOrdered(bin, instruction.ty, c.LLVMIntSLE, c.LLVMIntULE, c.LLVMRealOLE),
            .cmp_gt => |bin| self.emitCmpOrdered(bin, instruction.ty, c.LLVMIntSGT, c.LLVMIntUGT, c.LLVMRealOGT),
            .cmp_ge => |bin| self.emitCmpOrdered(bin, instruction.ty, c.LLVMIntSGE, c.LLVMIntUGE, c.LLVMRealOGE),
            .str_eq => |bin| self.emitStrCmp(bin, true),
            .str_ne => |bin| self.emitStrCmp(bin, false),

            // ── Logical ───────────────────────────────────────────
            .bool_and => |bin| {
                const lhs = self.resolveRef(bin.lhs);
                const rhs = self.resolveRef(bin.rhs);
                self.mapRef(c.LLVMBuildAnd(self.builder, lhs, rhs, "land"));
            },
            .bool_or => |bin| {
                const lhs = self.resolveRef(bin.lhs);
                const rhs = self.resolveRef(bin.rhs);
                self.mapRef(c.LLVMBuildOr(self.builder, lhs, rhs, "lor"));
            },
            .bool_not => |un| {
                const operand = self.resolveRef(un.operand);
                self.mapRef(c.LLVMBuildNot(self.builder, operand, "lnot"));
            },

            // ── Memory ────────────────────────────────────────────
            .alloca => |elem_ty| {
                const llvm_ty = self.toLLVMType(elem_ty);
                const result = c.LLVMBuildAlloca(self.builder, llvm_ty, "alloca");
                self.mapRef(result);
            },
            .load => |un| {
                const ptr = self.resolveRef(un.operand);
                const ptr_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(ptr));
                if (ptr_kind == c.LLVMPointerTypeKind and instruction.ty != .void) {
                    const llvm_ty = self.toLLVMType(instruction.ty);
                    const result = c.LLVMBuildLoad2(self.builder, llvm_ty, ptr, "load");
                    self.mapRef(result);
                } else {
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(if (instruction.ty == .void) .s64 else instruction.ty)));
                }
            },
            .store => |st| {
                const ptr = self.resolveRef(st.ptr);
                var val = self.resolveRef(st.val);
                // Guard: don't store void types or store to non-pointer
                const ptr_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(ptr));
                const val_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(val));
                if (ptr_kind == c.LLVMPointerTypeKind and val_kind != c.LLVMVoidTypeKind) {
                    // Coerce value to match the IR-declared pointer target type.
                    // E.g. storing i64 to *i8 (from index_gep on string) needs truncation.
                    //
                    // Only unwrap .pointer (from index_gep/alloca: *element → element).
                    // Never unwrap .many_pointer — it only appears as struct_gep field
                    // value types (e.g., [*]BigNode), where unwrapping to the element
                    // type gives a wrong store size (stores BigNode-sized instead of ptr).
                    if (self.getRefIRType(st.ptr)) |ptr_ir_ty| {
                        const pointee_info = self.ir_mod.types.get(ptr_ir_ty);
                        const target_ty: ?c.LLVMTypeRef = switch (pointee_info) {
                            .pointer => |p| self.toLLVMType(p.pointee),
                            else => null,
                        };
                        if (target_ty) |tt| {
                            val = self.coerceArg(val, tt);
                        }
                    }
                    _ = c.LLVMBuildStore(self.builder, val, ptr);
                }
                self.advanceRefCounter();
            },
            // ── Globals ───────────────────────────────────────────
            .global_get => |gid| {
                const llvm_global = self.global_map.get(gid.index()) orelse {
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                    return;
                };
                const llvm_ty = self.toLLVMType(instruction.ty);
                self.mapRef(c.LLVMBuildLoad2(self.builder, llvm_ty, llvm_global, "gload"));
            },
            .global_addr => |gid| {
                const llvm_global = self.global_map.get(gid.index()) orelse {
                    self.mapRef(c.LLVMGetUndef(self.cached_ptr));
                    return;
                };
                // Return the global's address directly (no load)
                self.mapRef(llvm_global);
            },
            .func_ref => |fid| {
                // Produce a reference to the function as a function pointer value
                if (self.func_map.get(@intFromEnum(fid))) |llvm_func| {
                    self.mapRef(llvm_func);
                } else {
                    self.mapRef(c.LLVMGetUndef(self.cached_ptr));
                }
            },
            .global_set => |gs| {
                const llvm_global = self.global_map.get(gs.global.index()) orelse {
                    self.advanceRefCounter();
                    return;
                };
                const val = self.resolveRef(gs.value);
                _ = c.LLVMBuildStore(self.builder, val, llvm_global);
                self.advanceRefCounter();
            },

            // ── Conversions ───────────────────────────────────────
            .widen => |conv| {
                const operand = self.resolveRef(conv.operand);
                const to_ty = self.toLLVMType(conv.to);
                const result = self.emitConversion(operand, conv.from, conv.to, to_ty);
                self.mapRef(result);
            },
            .narrow => |conv| {
                const operand = self.resolveRef(conv.operand);
                const to_ty = self.toLLVMType(conv.to);
                const result = self.emitConversion(operand, conv.from, conv.to, to_ty);
                self.mapRef(result);
            },
            .bitcast => |conv| {
                const operand = self.resolveRef(conv.operand);
                const to_ty = self.toLLVMType(conv.to);
                // LLVMBuildBitCast doesn't accept ptr↔int on modern
                // LLVM. Dispatch to PtrToInt / IntToPtr when needed —
                // lower.zig emits a `bitcast` IR op for both shapes.
                const from_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(operand));
                const to_kind = c.LLVMGetTypeKind(to_ty);
                if (from_kind == c.LLVMPointerTypeKind and to_kind == c.LLVMIntegerTypeKind) {
                    const i64_val = c.LLVMBuildPtrToInt(self.builder, operand, self.cached_i64, "pti");
                    const w = c.LLVMGetIntTypeWidth(to_ty);
                    if (w == 64) {
                        self.mapRef(i64_val);
                    } else if (w < 64) {
                        self.mapRef(c.LLVMBuildTrunc(self.builder, i64_val, to_ty, "pti.tr"));
                    } else {
                        self.mapRef(c.LLVMBuildZExt(self.builder, i64_val, to_ty, "pti.ext"));
                    }
                } else if (from_kind == c.LLVMIntegerTypeKind and to_kind == c.LLVMPointerTypeKind) {
                    self.mapRef(c.LLVMBuildIntToPtr(self.builder, operand, to_ty, "itp"));
                } else {
                    self.mapRef(c.LLVMBuildBitCast(self.builder, operand, to_ty, "bitcast"));
                }
            },
            .int_to_float => |conv| {
                const operand = self.resolveRef(conv.operand);
                const to_ty = self.toLLVMType(conv.to);
                const result = if (isSignedType(conv.from))
                    c.LLVMBuildSIToFP(self.builder, operand, to_ty, "sitofp")
                else
                    c.LLVMBuildUIToFP(self.builder, operand, to_ty, "uitofp");
                self.mapRef(result);
            },
            .float_to_int => |conv| {
                const operand = self.resolveRef(conv.operand);
                const to_ty = self.toLLVMType(conv.to);
                const result = if (isSignedType(conv.to))
                    c.LLVMBuildFPToSI(self.builder, operand, to_ty, "fptosi")
                else
                    c.LLVMBuildFPToUI(self.builder, operand, to_ty, "fptoui");
                self.mapRef(result);
            },

            // ── Pointer ops ───────────────────────────────────────
            .addr_of => |un| {
                // addr_of returns the pointer directly (the operand is already a ptr from alloca)
                self.mapRef(self.resolveRef(un.operand));
            },
            .deref => |un| {
                const ptr = self.resolveRef(un.operand);
                const llvm_ty = self.toLLVMType(instruction.ty);
                self.mapRef(c.LLVMBuildLoad2(self.builder, llvm_ty, ptr, "deref"));
            },

            // ── Calls ─────────────────────────────────────────────
            .objc_msg_send => |msg| {
                const msg_send = self.getObjcMsgSendValue();
                // Detect the sret case: >16 B non-HFA struct return.
                // Same predicate as the plain-foreign-call path so the
                // two arms stay in lockstep.
                const raw_ret_ty = self.toLLVMType(instruction.ty);
                const uses_sret = self.needsByval(instruction.ty, raw_ret_ty);
                const ret_ty = if (uses_sret) self.cached_void else raw_ret_ty;

                // Slot layout:
                //   uses_sret = false → [recv, sel, args...]
                //   uses_sret = true  → [sret_slot, recv, sel, args...]
                const sret_off: usize = if (uses_sret) 1 else 0;
                const total_params: usize = 2 + msg.args.len + sret_off;
                const param_types = self.alloc.alloc(c.LLVMTypeRef, total_params) catch unreachable;
                defer self.alloc.free(param_types);
                const call_args = self.alloc.alloc(c.LLVMValueRef, total_params) catch unreachable;
                defer self.alloc.free(call_args);

                var sret_slot: c.LLVMValueRef = null;
                if (uses_sret) {
                    sret_slot = c.LLVMBuildAlloca(self.builder, raw_ret_ty, "objc.sret");
                    param_types[0] = self.cached_ptr;
                    call_args[0] = sret_slot;
                }

                // recv (typed *void from the IR)
                param_types[sret_off] = self.cached_ptr;
                call_args[sret_off] = self.coerceArg(self.resolveRef(msg.recv), self.cached_ptr);
                // sel (loaded SEL — opaque ptr)
                param_types[sret_off + 1] = self.cached_ptr;
                call_args[sret_off + 1] = self.coerceArg(self.resolveRef(msg.sel), self.cached_ptr);
                // additional args take their IR types, with ABI
                // coercion applied so structs / strings decay the
                // same way they do for any C foreign call.
                for (msg.args, 0..) |arg_ref, i| {
                    const raw_ty = self.getRefIRType(arg_ref) orelse .void;
                    const raw_llvm = self.toLLVMType(raw_ty);
                    const coerced_ty = self.abiCoerceParamType(raw_ty, raw_llvm);
                    param_types[i + 2 + sret_off] = coerced_ty;
                    call_args[i + 2 + sret_off] = self.coerceArg(self.resolveRef(arg_ref), coerced_ty);
                }

                const fn_ty = c.LLVMFunctionType(ret_ty, param_types.ptr, @intCast(total_params), 0);
                const call_label: [*:0]const u8 = if (instruction.ty == .void or uses_sret) "" else "objc.msg";
                var result = c.LLVMBuildCall2(self.builder, fn_ty, msg_send, call_args.ptr, @intCast(total_params), call_label);
                if (uses_sret) {
                    // Tag the call's arg 0 (sret slot) with the sret
                    // attribute so the AArch64 / SysV backends route
                    // through the x8 / hidden-pointer convention.
                    const sret_kind = c.LLVMGetEnumAttributeKindForName("sret", 4);
                    const sret_attr = c.LLVMCreateTypeAttribute(self.context, sret_kind, raw_ret_ty);
                    const param1_idx: c.LLVMAttributeIndex = @bitCast(@as(i32, 1));
                    c.LLVMAddCallSiteAttribute(result, param1_idx, sret_attr);
                    result = c.LLVMBuildLoad2(self.builder, raw_ret_ty, sret_slot, "objc.sret.load");
                }
                // Always mapRef — the IR Ref counter for this
                // instruction advances regardless of return type,
                // so skipping it would misalign every subsequent
                // ref lookup in this function.
                self.mapRef(result);
            },
            .jni_msg_send => |msg| {
                // JNI vtable indirection:
                //   ifs = *env                                   // JNINativeInterface*
                //   instance:  cls = ifs[GetObjectClass](env, target)
                //              mid = ifs[GetMethodID](env, cls, name, sig)
                //              ifs[Call<T>Method](env, target, mid, args...)
                //   static:    target IS the jclass — skip GetObjectClass
                //              mid = ifs[GetStaticMethodID](env, target, name, sig)
                //              ifs[CallStatic<T>Method](env, target, mid, args...)
                //   ctor:      cls = ifs[FindClass](env, parent_class_path)
                //              mid = ifs[GetMethodID](env, cls, "<init>", sig)
                //              ifs[NewObject](env, cls, mid, args...) → jobject
                //   nonvirt:   handled below via FindClass + GetMethodID +
                //              CallNonvirtual<T>Method.
                // The cached path (msg.cache_key != null) still shares one
                // (jclass GlobalRef, jmethodID) pair per literal (name, sig).
                if (msg.is_constructor) {
                    self.emitJniConstructor(msg, instruction.ty);
                    return;
                }
                const ret_ty_id = instruction.ty;
                const is_pointer_ret = switch (self.ir_mod.types.get(ret_ty_id)) {
                    .pointer, .many_pointer => true,
                    else => false,
                };
                const call_method_offset: u32 = if (msg.is_static) blk: {
                    if (is_pointer_ret) break :blk Jni.CallStaticObjectMethod;
                    break :blk switch (ret_ty_id) {
                        .void => Jni.CallStaticVoidMethod,
                        .s32 => Jni.CallStaticIntMethod,
                        .s64 => Jni.CallStaticLongMethod,
                        .f32 => Jni.CallStaticFloatMethod,
                        .f64 => Jni.CallStaticDoubleMethod,
                        .bool => Jni.CallStaticBooleanMethod,
                        else => {
                            self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                            return;
                        },
                    };
                } else if (msg.is_nonvirtual) blk: {
                    if (is_pointer_ret) break :blk Jni.CallNonvirtualObjectMethod;
                    break :blk switch (ret_ty_id) {
                        .void => Jni.CallNonvirtualVoidMethod,
                        .s32 => Jni.CallNonvirtualIntMethod,
                        .s64 => Jni.CallNonvirtualLongMethod,
                        .f32 => Jni.CallNonvirtualFloatMethod,
                        .f64 => Jni.CallNonvirtualDoubleMethod,
                        .bool => Jni.CallNonvirtualBooleanMethod,
                        else => {
                            self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                            return;
                        },
                    };
                } else blk: {
                    if (is_pointer_ret) break :blk Jni.CallObjectMethod;
                    break :blk switch (ret_ty_id) {
                        .void => Jni.CallVoidMethod,
                        .s32 => Jni.CallIntMethod,
                        .s64 => Jni.CallLongMethod,
                        .f32 => Jni.CallFloatMethod,
                        .f64 => Jni.CallDoubleMethod,
                        .bool => Jni.CallBooleanMethod,
                        else => {
                            self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                            return;
                        },
                    };
                };
                const get_mid_offset: u32 = if (msg.is_static) Jni.GetStaticMethodID else Jni.GetMethodID;

                const env = self.resolveRef(msg.env);
                const target = self.resolveRef(msg.target);
                // String literals lower as `{ptr, i64}` slices in sx IR;
                // JNI's `GetMethodID` expects raw C strings, so extract
                // field 0 when the source is a slice.
                const name_ptr = self.extractSlicePtr(self.resolveRef(msg.name));
                const sig_ptr = self.extractSlicePtr(self.resolveRef(msg.sig));

                const ifs = c.LLVMBuildLoad2(self.builder, self.cached_ptr, env, "jni.ifs");

                // Method-ID resolution. When `name` and `sig` are both
                // string literals the call site participates in
                // `(name, sig)` slot interning (step 1.17): a shared
                // pair of static globals holds the `jclass` GlobalRef
                // and the `jmethodID`, populated lazily on the first
                // call to any matching site. Non-literal sites fall
                // back to the per-call `GetObjectClass + GetMethodID`
                // sequence (1.15 shape).
                const mid = if (msg.cache_key) |ck| blk: {
                    const pair = self.getOrCreateJniSlots(ck.name_str, ck.sig_str);
                    const cached_mid = c.LLVMBuildLoad2(self.builder, self.cached_ptr, pair.mid_slot, "jni.cached.mid");
                    const is_cached = c.LLVMBuildICmp(self.builder, c.LLVMIntNE, cached_mid, c.LLVMConstNull(self.cached_ptr), "jni.is.cached");

                    const cur_fn = c.LLVMGetBasicBlockParent(c.LLVMGetInsertBlock(self.builder));
                    const miss_bb = c.LLVMAppendBasicBlockInContext(self.context, cur_fn, "jni.miss");
                    const cont_bb = c.LLVMAppendBasicBlockInContext(self.context, cur_fn, "jni.cont");
                    const before_bb = c.LLVMGetInsertBlock(self.builder);
                    _ = c.LLVMBuildCondBr(self.builder, is_cached, cont_bb, miss_bb);

                    // Miss path:
                    //   instance: GetObjectClass → NewGlobalRef → GetMethodID
                    //   static:   target IS class → NewGlobalRef(target) → GetStaticMethodID
                    c.LLVMPositionBuilderAtEnd(self.builder, miss_bb);
                    const local_cls = if (msg.is_static) target else inst_cls: {
                        const get_obj_cls = self.loadJniFn(ifs, Jni.GetObjectClass, "jni.GetObjectClass");
                        var gocls_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr };
                        const gocls_ty = c.LLVMFunctionType(self.cached_ptr, &gocls_params, 2, 0);
                        var gocls_args = [_]c.LLVMValueRef{ env, target };
                        break :inst_cls c.LLVMBuildCall2(self.builder, gocls_ty, get_obj_cls, &gocls_args, 2, "jni.cls");
                    };
                    const new_global_ref = self.loadJniFn(ifs, Jni.NewGlobalRef, "jni.NewGlobalRef");
                    var ngref_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr };
                    const ngref_ty = c.LLVMFunctionType(self.cached_ptr, &ngref_params, 2, 0);
                    var ngref_args = [_]c.LLVMValueRef{ env, local_cls };
                    const global_cls = c.LLVMBuildCall2(self.builder, ngref_ty, new_global_ref, &ngref_args, 2, "jni.global.cls");
                    _ = c.LLVMBuildStore(self.builder, global_cls, pair.cls_slot);
                    const get_mid = self.loadJniFn(ifs, get_mid_offset, if (msg.is_static) "jni.GetStaticMethodID" else "jni.GetMethodID");
                    var gmid_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr, self.cached_ptr, self.cached_ptr };
                    const gmid_ty = c.LLVMFunctionType(self.cached_ptr, &gmid_params, 4, 0);
                    var gmid_args = [_]c.LLVMValueRef{ env, global_cls, name_ptr, sig_ptr };
                    const fresh_mid = c.LLVMBuildCall2(self.builder, gmid_ty, get_mid, &gmid_args, 4, "jni.fresh.mid");
                    _ = c.LLVMBuildStore(self.builder, fresh_mid, pair.mid_slot);
                    const miss_end_bb = c.LLVMGetInsertBlock(self.builder);
                    _ = c.LLVMBuildBr(self.builder, cont_bb);

                    // Cont: phi the cached vs fresh mid.
                    c.LLVMPositionBuilderAtEnd(self.builder, cont_bb);
                    const phi = c.LLVMBuildPhi(self.builder, self.cached_ptr, "jni.mid");
                    var phi_vals = [_]c.LLVMValueRef{ cached_mid, fresh_mid };
                    var phi_blocks = [_]c.LLVMBasicBlockRef{ before_bb, miss_end_bb };
                    c.LLVMAddIncoming(phi, &phi_vals, &phi_blocks, 2);
                    break :blk phi;
                } else blk: {
                    const cls = if (msg.is_static) target else if (msg.is_nonvirtual) nonvirt_cls: {
                        // `super.method(args)`: dispatch is bound to a
                        // specific class (the parent), not subclass-override.
                        // Resolve via FindClass(parent_path). No caching yet —
                        // per-call lookup. The parent path is a NUL-terminated
                        // C string emitted as a private LLVM global.
                        const path = msg.parent_class_path orelse "";
                        const path_global = self.emitCStringGlobal(path, "jni.parent.path");
                        const find_class = self.loadJniFn(ifs, Jni.FindClass, "jni.FindClass");
                        var fc_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr };
                        const fc_ty = c.LLVMFunctionType(self.cached_ptr, &fc_params, 2, 0);
                        var fc_args = [_]c.LLVMValueRef{ env, path_global };
                        break :nonvirt_cls c.LLVMBuildCall2(self.builder, fc_ty, find_class, &fc_args, 2, "jni.parent.cls");
                    } else inst_cls: {
                        const get_obj_cls = self.loadJniFn(ifs, Jni.GetObjectClass, "jni.GetObjectClass");
                        var gocls_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr };
                        const gocls_ty = c.LLVMFunctionType(self.cached_ptr, &gocls_params, 2, 0);
                        var gocls_args = [_]c.LLVMValueRef{ env, target };
                        break :inst_cls c.LLVMBuildCall2(self.builder, gocls_ty, get_obj_cls, &gocls_args, 2, "jni.cls");
                    };
                    const get_mid = self.loadJniFn(ifs, get_mid_offset, if (msg.is_static) "jni.GetStaticMethodID" else "jni.GetMethodID");
                    var gmid_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr, self.cached_ptr, self.cached_ptr };
                    const gmid_ty = c.LLVMFunctionType(self.cached_ptr, &gmid_params, 4, 0);
                    var gmid_args = [_]c.LLVMValueRef{ env, cls, name_ptr, sig_ptr };
                    const mid_val = c.LLVMBuildCall2(self.builder, gmid_ty, get_mid, &gmid_args, 4, "jni.mid");
                    if (msg.is_nonvirtual) {
                        // Stash cls in a dummy slot so the call site below
                        // can pick it up. Easiest path: do the call right
                        // here and return Ref.none, but we need to keep the
                        // outer phi shape. Instead, return both via tuple
                        // through an auxiliary local — simplest is to attach
                        // `cls` to a per-invocation slot. Use a stack alloca.
                        const cls_slot = c.LLVMBuildAlloca(self.builder, self.cached_ptr, "jni.parent.cls.slot");
                        _ = c.LLVMBuildStore(self.builder, cls, cls_slot);
                        // Tag the slot pointer onto the phi result via the
                        // generated metadata: we'll re-extract by re-running
                        // FindClass — actually simpler: lower nonvirtual on
                        // the spot below. Drop the implicit `break` here:
                        const call_fn = self.loadJniFn(ifs, call_method_offset, "jni.callfn.nonvirtual");
                        const raw_ret = self.toLLVMType(ret_ty_id);
                        const total_call_params_nv: usize = 4 + msg.args.len;
                        const call_param_types_nv = self.alloc.alloc(c.LLVMTypeRef, total_call_params_nv) catch unreachable;
                        defer self.alloc.free(call_param_types_nv);
                        const call_args_nv = self.alloc.alloc(c.LLVMValueRef, total_call_params_nv) catch unreachable;
                        defer self.alloc.free(call_args_nv);
                        call_param_types_nv[0] = self.cached_ptr;
                        call_param_types_nv[1] = self.cached_ptr;
                        call_param_types_nv[2] = self.cached_ptr;
                        call_param_types_nv[3] = self.cached_ptr;
                        call_args_nv[0] = env;
                        call_args_nv[1] = target;
                        call_args_nv[2] = cls;
                        call_args_nv[3] = mid_val;
                        for (msg.args, 0..) |arg_ref, i| {
                            const raw_ty = self.getRefIRType(arg_ref) orelse .void;
                            const raw_llvm = self.toLLVMType(raw_ty);
                            const coerced_ty = self.abiCoerceParamType(raw_ty, raw_llvm);
                            call_param_types_nv[i + 4] = coerced_ty;
                            call_args_nv[i + 4] = self.coerceArg(self.resolveRef(arg_ref), coerced_ty);
                        }
                        const call_fn_ty_nv = c.LLVMFunctionType(raw_ret, call_param_types_nv.ptr, @intCast(total_call_params_nv), 0);
                        const label_nv: [*:0]const u8 = if (ret_ty_id == .void) "" else "jni.nonvirtual.ret";
                        const result_nv = c.LLVMBuildCall2(self.builder, call_fn_ty_nv, call_fn, call_args_nv.ptr, @intCast(total_call_params_nv), label_nv);
                        self.mapRef(result_nv);
                        return;
                    }
                    break :blk mid_val;
                };

                // Call<Type>Method: (JNIEnv*, jobject, jmethodID, args...) -> RetTy
                const call_fn = self.loadJniFn(ifs, call_method_offset, "jni.callfn");
                const raw_ret = self.toLLVMType(ret_ty_id);
                const total_call_params: usize = 3 + msg.args.len;
                const call_param_types = self.alloc.alloc(c.LLVMTypeRef, total_call_params) catch unreachable;
                defer self.alloc.free(call_param_types);
                const call_args = self.alloc.alloc(c.LLVMValueRef, total_call_params) catch unreachable;
                defer self.alloc.free(call_args);
                call_param_types[0] = self.cached_ptr;
                call_param_types[1] = self.cached_ptr;
                call_param_types[2] = self.cached_ptr;
                call_args[0] = env;
                call_args[1] = target;
                call_args[2] = mid;
                for (msg.args, 0..) |arg_ref, i| {
                    const raw_ty = self.getRefIRType(arg_ref) orelse .void;
                    const raw_llvm = self.toLLVMType(raw_ty);
                    const coerced_ty = self.abiCoerceParamType(raw_ty, raw_llvm);
                    call_param_types[i + 3] = coerced_ty;
                    call_args[i + 3] = self.coerceArg(self.resolveRef(arg_ref), coerced_ty);
                }
                const call_fn_ty = c.LLVMFunctionType(raw_ret, call_param_types.ptr, @intCast(total_call_params), 0);
                const label: [*:0]const u8 = if (ret_ty_id == .void) "" else "jni.ret";
                const result = c.LLVMBuildCall2(self.builder, call_fn_ty, call_fn, call_args.ptr, @intCast(total_call_params), label);
                self.mapRef(result);
            },
            .call => |call_op| {
                // Evaluate comptime functions at compile time
                const callee_func = &self.ir_mod.functions.items[call_op.callee.index()];
                if (callee_func.is_comptime and call_op.args.len == 0) {
                    var interp_inst = Interpreter.init(self.ir_mod, self.alloc);
                    interp_inst.build_config = &self.build_config;
                    if (self.import_sources) |sm| interp_inst.setSourceMap(sm);
                    defer interp_inst.deinit();
                    if (interp_inst.call(call_op.callee, &.{})) |result| {
                        if (result.asInt()) |v| {
                            self.mapRef(c.LLVMConstInt(self.toLLVMType(instruction.ty), @bitCast(v), 0));
                            return;
                        } else if (result.asFloat()) |v| {
                            self.mapRef(c.LLVMConstReal(self.toLLVMType(instruction.ty), v));
                            return;
                        } else if (result.asBool()) |v| {
                            self.mapRef(c.LLVMConstInt(self.toLLVMType(instruction.ty), @intFromBool(v), 0));
                            return;
                        } else if (result == .string) {
                            self.mapRef(self.emitStringConstant(result.string));
                            return;
                        }
                    } else |_| {}
                }
                const callee = self.func_map.get(call_op.callee.index()) orelse {
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                    return;
                };
                const callee_needs_c_abi = callee_func.is_extern or callee_func.call_conv == .c;
                const callee_raw_ret = self.toLLVMType(callee_func.ret);
                const callee_uses_sret = callee_needs_c_abi and self.needsByval(callee_func.ret, callee_raw_ret);

                // When the callee uses sret, prepend an alloca for the result.
                // Index alignment: actual_args[0] = sret_slot; actual_args[i+1] = sx arg i.
                const sret_off: usize = if (callee_uses_sret) 1 else 0;
                const total_args = call_op.args.len + sret_off;
                const args = self.alloc.alloc(c.LLVMValueRef, total_args) catch unreachable;
                defer self.alloc.free(args);
                var sret_slot: c.LLVMValueRef = null;
                if (callee_uses_sret) {
                    sret_slot = c.LLVMBuildAlloca(self.builder, callee_raw_ret, "sret.slot");
                    args[0] = sret_slot;
                }
                for (call_op.args, 0..) |arg_ref, j| {
                    args[j + sret_off] = self.resolveRef(arg_ref);
                }
                const arg_count: c_uint = @intCast(total_args);

                // Get the function type from LLVM and coerce arguments
                const fn_ty = c.LLVMGlobalGetValueType(callee);
                const param_count = c.LLVMCountParamTypes(fn_ty);
                if (param_count > 0) {
                    const param_types = self.alloc.alloc(c.LLVMTypeRef, param_count) catch unreachable;
                    defer self.alloc.free(param_types);
                    c.LLVMGetParamTypes(fn_ty, param_types.ptr);
                    for (0..@min(args.len, param_count)) |j| {
                        // The sret slot is already a properly-typed pointer; skip coercion.
                        if (callee_uses_sret and j == 0) continue;
                        const fn_param_idx = j - sret_off;
                        // Materialize byval args before coercion so we pass a ptr instead of the struct value.
                        if (callee_needs_c_abi and fn_param_idx < callee_func.params.len) {
                            const ir_ty = callee_func.params[fn_param_idx].ty;
                            const raw_struct = self.toLLVMType(ir_ty);
                            if (self.needsByval(ir_ty, raw_struct)) {
                                args[j] = self.materializeByvalArg(args[j], raw_struct);
                                continue;
                            }
                        }
                        args[j] = self.coerceArg(args[j], param_types[j]);
                    }
                }
                // A `void`/`noreturn` call has no value, so it must stay
                // unnamed (LLVM rejects a named void result).
                const call_is_void_like = instruction.ty == .void or instruction.ty == .noreturn;
                const call_label: [*:0]const u8 = if (call_is_void_like or callee_uses_sret) "" else "call";
                var result = c.LLVMBuildCall2(self.builder, fn_ty, callee, args.ptr, arg_count, call_label);
                if (callee_uses_sret) {
                    // Mirror the function-decl `sret(<T>)` attribute on the call site so the
                    // LLVM backend lowers arg 0 via x8 (AAPCS64) / hidden ptr (SysV AMD64).
                    const sret_kind = c.LLVMGetEnumAttributeKindForName("sret", 4);
                    const sret_attr = c.LLVMCreateTypeAttribute(self.context, sret_kind, callee_raw_ret);
                    const param1_idx: c.LLVMAttributeIndex = @bitCast(@as(i32, 1));
                    c.LLVMAddCallSiteAttribute(result, param1_idx, sret_attr);
                    // Load the actual struct value the callee wrote into the slot.
                    result = c.LLVMBuildLoad2(self.builder, callee_raw_ret, sret_slot, "sret.load");
                } else if (!call_is_void_like and callee_func.is_extern) {
                    // Coerce ABI return value (e.g. i64 / [2 x i64]) back to IR struct type if needed
                    const expected_ty = self.toLLVMType(instruction.ty);
                    result = self.coerceArg(result, expected_ty);
                }
                self.mapRef(result);
            },
            .call_indirect => |call_op| {
                const callee = self.resolveRef(call_op.callee);
                const arg_count: c_uint = @intCast(call_op.args.len);
                const args = self.alloc.alloc(c.LLVMValueRef, call_op.args.len) catch unreachable;
                defer self.alloc.free(args);
                for (call_op.args, 0..) |arg_ref, j| {
                    args[j] = self.resolveRef(arg_ref);
                }

                // Get callee's IR type to resolve parameter types accurately
                const callee_ir_ty = self.getRefIRType(call_op.callee);
                const fn_params: ?[]const @import("types.zig").TypeId = if (callee_ir_ty) |cty| blk: {
                    if (!cty.isBuiltin()) {
                        const ci = self.ir_mod.types.get(cty);
                        switch (ci) {
                            .function => |f| break :blk f.params,
                            .closure => |cl| break :blk cl.params,
                            else => {},
                        }
                    }
                    break :blk null;
                } else null;

                // Read the fn-pointer type's calling convention. Only `.c` opts
                // into the C-ABI byval coercion for >16B aggregate params.
                const fp_is_c_abi: bool = if (callee_ir_ty) |cty| blk: {
                    if (!cty.isBuiltin()) {
                        const ci = self.ir_mod.types.get(cty);
                        if (ci == .function and ci.function.call_conv == .c) break :blk true;
                    }
                    break :blk false;
                } else false;

                // Default-conv fn-pointers under implicit-ctx carry a hidden
                // `*void` (the implicit __sx_ctx) at LLVM slot 0. The IR fn
                // type does not include it, so shift fn_params lookups by 1.
                const fp_ctx_slots: usize = if (callee_ir_ty) |cty| blk: {
                    if (!self.ir_mod.has_implicit_ctx) break :blk 0;
                    if (cty.isBuiltin()) break :blk 0;
                    const ci = self.ir_mod.types.get(cty);
                    switch (ci) {
                        .function => |f| break :blk if (f.call_conv == .c) @as(usize, 0) else 1,
                        else => break :blk 0,
                    }
                } else 0;

                const ret_ty = if (callee_ir_ty) |cty| blk: {
                    if (!cty.isBuiltin()) {
                        const ci = self.ir_mod.types.get(cty);
                        switch (ci) {
                            .function => |f| break :blk self.toLLVMType(f.ret),
                            .closure => |cl| break :blk self.toLLVMType(cl.ret),
                            else => {},
                        }
                    }
                    break :blk self.toLLVMType(instruction.ty);
                } else self.toLLVMType(instruction.ty);

                const param_tys = self.alloc.alloc(c.LLVMTypeRef, call_op.args.len) catch unreachable;
                defer self.alloc.free(param_tys);
                if (fn_params) |fp| {
                    for (0..call_op.args.len) |j| {
                        // Slots 0..fp_ctx_slots are the implicit __sx_ctx
                        // (passed as opaque ptr; not in fp).
                        if (j < fp_ctx_slots) {
                            param_tys[j] = self.cached_ptr;
                            args[j] = self.coerceArg(args[j], self.cached_ptr);
                            continue;
                        }
                        const fp_idx = j - fp_ctx_slots;
                        if (fp_idx < fp.len) {
                            const raw_struct = self.toLLVMType(fp[fp_idx]);
                            if (fp_is_c_abi and self.needsByval(fp[fp_idx], raw_struct)) {
                                args[j] = self.materializeByvalArg(args[j], raw_struct);
                                param_tys[j] = self.cached_ptr;
                                continue;
                            }
                            var llvm_pty = raw_struct;
                            // Array params in fn-ptr calls decay to pointers (C ABI)
                            if (c.LLVMGetTypeKind(llvm_pty) == c.LLVMArrayTypeKind) {
                                llvm_pty = self.cached_ptr;
                            }
                            param_tys[j] = llvm_pty;
                            args[j] = self.coerceArg(args[j], llvm_pty);
                        } else {
                            param_tys[j] = c.LLVMTypeOf(args[j]);
                        }
                    }
                } else {
                    for (args, 0..) |arg, j| {
                        param_tys[j] = c.LLVMTypeOf(arg);
                    }
                }
                const fn_ty = c.LLVMFunctionType(ret_ty, param_tys.ptr, arg_count, 0);
                const icall_void_like = instruction.ty == .void or instruction.ty == .noreturn;
                var result = c.LLVMBuildCall2(self.builder, fn_ty, callee, args.ptr, arg_count, if (icall_void_like) "" else "icall");

                // Coerce call result to instruction's expected type
                const expected_ty = self.toLLVMType(instruction.ty);
                if (!icall_void_like and c.LLVMTypeOf(result) != expected_ty) {
                    result = self.coerceArg(result, expected_ty);
                }
                self.mapRef(result);
            },

            // ── Terminators ────────────────────────────────────────
            .ret => |un| {
                var val = self.resolveRef(un.operand);
                const func = &self.ir_mod.functions.items[self.current_func_idx];
                // Failable main: wrap the return in the entry-point reporter
                // (ERR E4.2) — exit 0 (or the value) on success, else print the
                // trace + tag to stderr and exit 1 — instead of returning the
                // tag/tuple as the raw exit code. Two shapes:
                //   `-> !`        → `val` is the bare u32 error tag.
                //   `-> (int, !)` → `val` is a `{value, tag}` tuple; extract both.
                if (self.current_func_is_main) {
                    const rinfo = self.ir_mod.types.get(func.ret);
                    if (rinfo == .error_set) {
                        self.emitFailableMainRet(null, val);
                        self.advanceRefCounter();
                        return;
                    }
                    if (rinfo == .tuple and rinfo.tuple.fields.len == 2 and
                        self.ir_mod.types.get(rinfo.tuple.fields[1]) == .error_set)
                    {
                        const value = c.LLVMBuildExtractValue(self.builder, val, 0, "main.ret.val");
                        const tag = c.LLVMBuildExtractValue(self.builder, val, 1, "main.ret.tag");
                        self.emitFailableMainRet(value, tag);
                        self.advanceRefCounter();
                        return;
                    }
                }
                // sret-shaped function: declared return-type-in-IR is
                // the struct, but the LLVM signature is void with a
                // prepended ptr sret param. Store the value through
                // the sret slot and emit ret void.
                const needs_c_abi = func.is_extern or func.call_conv == .c;
                const raw_ret = self.toLLVMType(func.ret);
                if (needs_c_abi and self.needsByval(func.ret, raw_ret)) {
                    const llvm_func2 = c.LLVMGetBasicBlockParent(c.LLVMGetInsertBlock(self.builder));
                    const sret_ptr = c.LLVMGetParam(llvm_func2, 0);
                    _ = c.LLVMBuildStore(self.builder, val, sret_ptr);
                    _ = c.LLVMBuildRetVoid(self.builder);
                    self.advanceRefCounter();
                    return;
                }
                // Coerce return value to match the function's LLVM return type
                const llvm_func = c.LLVMGetBasicBlockParent(c.LLVMGetInsertBlock(self.builder));
                const fn_ty = c.LLVMGlobalGetValueType(llvm_func);
                const expected_ret = c.LLVMGetReturnType(fn_ty);
                val = self.coerceArg(val, expected_ret);
                // If coercion didn't fix the type (e.g. dead comptime function),
                // emit undef of the correct type to avoid LLVM verification error
                if (c.LLVMTypeOf(val) != expected_ret) {
                    val = c.LLVMGetUndef(expected_ret);
                }
                _ = c.LLVMBuildRet(self.builder, val);
                self.advanceRefCounter();
            },
            .ret_void => {
                if (self.current_func_is_main) {
                    // main must return i32 0 for JIT
                    _ = c.LLVMBuildRet(self.builder, c.LLVMConstInt(self.cached_i32, 0, 0));
                } else {
                    _ = c.LLVMBuildRetVoid(self.builder);
                }
                self.advanceRefCounter();
            },
            .@"unreachable" => {
                _ = c.LLVMBuildUnreachable(self.builder);
                self.advanceRefCounter();
            },
            .br => |branch| {
                const target = self.getBlock(func_idx, branch.target);
                _ = c.LLVMBuildBr(self.builder, target);
                self.advanceRefCounter();
            },
            .cond_br => |cbr| {
                var cond = self.resolveRef(cbr.cond);
                const then_bb = self.getBlock(func_idx, cbr.then_target);
                const else_bb = self.getBlock(func_idx, cbr.else_target);
                // Coerce condition to i1 if needed (e.g., loaded bool stored as i64)
                const cond_ty = c.LLVMTypeOf(cond);
                const cond_kind = c.LLVMGetTypeKind(cond_ty);
                if (cond_ty != self.cached_i1) {
                    if (cond_kind == c.LLVMPointerTypeKind) {
                        cond = c.LLVMBuildICmp(self.builder, c.LLVMIntNE, cond, c.LLVMConstNull(cond_ty), "tobool");
                    } else if (cond_kind == c.LLVMIntegerTypeKind) {
                        cond = c.LLVMBuildICmp(self.builder, c.LLVMIntNE, cond, c.LLVMConstInt(cond_ty, 0, 0), "tobool");
                    } else if (cond_kind == c.LLVMStructTypeKind) {
                        // Struct values are always truthy
                        cond = c.LLVMConstInt(self.cached_i1, 1, 0);
                    } else {
                        cond = c.LLVMConstInt(self.cached_i1, 1, 0); // default truthy
                    }
                }
                _ = c.LLVMBuildCondBr(self.builder, cond, then_bb, else_bb);
                self.advanceRefCounter();
            },

            // ── Struct ops ────────────────────────────────────────────
            .struct_init => |agg| {
                const struct_ty = self.toLLVMType(instruction.ty);
                const type_kind = c.LLVMGetTypeKind(struct_ty);
                // For vector types, use InsertElement instead of InsertValue
                const is_vector = type_kind == c.LLVMVectorTypeKind or type_kind == c.LLVMScalableVectorTypeKind;
                // For array types, get expected element type for coercion
                const is_array = type_kind == c.LLVMArrayTypeKind;
                const elem_llvm_ty = if (is_array) c.LLVMGetElementType(struct_ty) else null;
                var result = c.LLVMGetUndef(struct_ty);
                for (agg.fields, 0..) |field_ref, i| {
                    var field_val = self.resolveRef(field_ref);
                    if (is_vector) {
                        // Coerce element to match vector element type
                        const vec_elem_ty = c.LLVMGetElementType(struct_ty);
                        const val_ty = c.LLVMTypeOf(field_val);
                        if (val_ty != vec_elem_ty) {
                            field_val = self.coerceArg(field_val, vec_elem_ty);
                        }
                        const idx = c.LLVMConstInt(self.cached_i32, @intCast(i), 0);
                        result = c.LLVMBuildInsertElement(self.builder, result, field_val, idx, "vi");
                    } else {
                        // Coerce element to match array element type if needed
                        if (elem_llvm_ty) |elt| {
                            const val_ty = c.LLVMTypeOf(field_val);
                            if (val_ty != elt) {
                                const val_kind = c.LLVMGetTypeKind(val_ty);
                                const elt_kind = c.LLVMGetTypeKind(elt);
                                if (val_kind == c.LLVMIntegerTypeKind and elt_kind == c.LLVMIntegerTypeKind) {
                                    const val_w = c.LLVMGetIntTypeWidth(val_ty);
                                    const elt_w = c.LLVMGetIntTypeWidth(elt);
                                    if (val_w > elt_w) {
                                        field_val = c.LLVMBuildTrunc(self.builder, field_val, elt, "atrunc");
                                    } else if (val_w < elt_w) {
                                        field_val = c.LLVMBuildZExt(self.builder, field_val, elt, "aext");
                                    }
                                }
                            }
                        } else if (type_kind == c.LLVMStructTypeKind) {
                            // Coerce struct field value to match declared field type
                            const n_elts = c.LLVMCountStructElementTypes(struct_ty);
                            if (n_elts > 0 and i < n_elts) {
                                const field_ty = c.LLVMStructGetTypeAtIndex(struct_ty, @intCast(i));
                                const val_ty = c.LLVMTypeOf(field_val);
                                if (val_ty != field_ty) {
                                    field_val = self.coerceArg(field_val, field_ty);
                                }
                            }
                        }
                        result = c.LLVMBuildInsertValue(self.builder, result, field_val, @intCast(i), "si");
                    }
                }
                self.mapRef(result);
            },
            .struct_get => |fa| {
                const base = self.resolveRef(fa.base);
                // Safety: null base means unresolved reference — emit undef
                if (base == null) {
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                } else {
                    // Safety: check that base is an aggregate type (struct/array/vector), not scalar
                    const base_ty = c.LLVMTypeOf(base);
                    const base_ty_kind = c.LLVMGetTypeKind(base_ty);
                    if (base_ty_kind == c.LLVMVectorTypeKind or base_ty_kind == c.LLVMScalableVectorTypeKind) {
                        // Vector: use ExtractElement with an index
                        const idx = c.LLVMConstInt(self.cached_i32, @intCast(fa.field_index), 0);
                        const result = c.LLVMBuildExtractElement(self.builder, base, idx, "ve");
                        self.mapRef(result);
                    } else if (base_ty_kind == c.LLVMStructTypeKind or base_ty_kind == c.LLVMArrayTypeKind) {
                        // Validate field index is in bounds
                        const n_fields = if (base_ty_kind == c.LLVMStructTypeKind) c.LLVMCountStructElementTypes(base_ty) else 0;
                        // Check builder has valid insert point
                        const insert_bb = c.LLVMGetInsertBlock(self.builder);
                        if (insert_bb == null or (n_fields == 0 and base_ty_kind == c.LLVMStructTypeKind) or (n_fields > 0 and fa.field_index >= n_fields)) {
                            self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                        } else {
                            const result = c.LLVMBuildExtractValue(self.builder, base, @intCast(fa.field_index), "sg");
                            self.mapRef(result);
                        }
                    } else {
                        // Base is not an aggregate (e.g., placeholder undef of scalar type)
                        self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                    }
                }
            },
            .struct_gep => |fa| {
                const base_ptr = self.resolveRef(fa.base);
                // Safety: verify base is a pointer before GEP
                const base_ty_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(base_ptr));
                if (base_ty_kind == c.LLVMPointerTypeKind) {
                    const struct_llvm_ty = if (fa.base_type) |bt|
                        self.toLLVMType(self.resolveAggregate(bt))
                    else
                        self.resolveGepStructType(fa.base, instruction);
                    const st_kind = c.LLVMGetTypeKind(struct_llvm_ty);
                    if (st_kind == c.LLVMStructTypeKind or st_kind == c.LLVMArrayTypeKind) {
                        const result = c.LLVMBuildStructGEP2(self.builder, struct_llvm_ty, base_ptr, @intCast(fa.field_index), "gep");
                        self.mapRef(result);
                    } else {
                        self.mapRef(c.LLVMGetUndef(self.cached_ptr));
                    }
                } else {
                    self.mapRef(c.LLVMGetUndef(self.cached_ptr));
                }
            },

            // ── Enum ops ─────────────────────────────────────────────
            .enum_init => |ei| {
                if (ei.payload.isNone()) {
                    // Simple enum (no payload) — just a tag integer
                    const ty = self.toLLVMType(instruction.ty);
                    const ty_kind = c.LLVMGetTypeKind(ty);
                    if (ty_kind == c.LLVMIntegerTypeKind) {
                        // Plain enum or builtin integer → integer constant
                        self.mapRef(c.LLVMConstInt(ty, ei.tag, 0));
                    } else if (ty_kind == c.LLVMStructTypeKind) {
                        // Tagged union with no payload — header field 0 holds the tag
                        const header_ty = c.LLVMStructGetTypeAtIndex(ty, 0);
                        const tag_val = c.LLVMConstInt(header_ty, ei.tag, 0);
                        var result = c.LLVMGetUndef(ty);
                        result = c.LLVMBuildInsertValue(self.builder, result, tag_val, 0, "ei.tag");
                        self.mapRef(result);
                    } else {
                        self.mapRef(c.LLVMConstInt(self.cached_i64, ei.tag, 0));
                    }
                } else {
                    // Tagged union with payload — { header, payload_bytes }
                    const union_ty = self.toLLVMType(instruction.ty);
                    const header_ty = c.LLVMStructGetTypeAtIndex(union_ty, 0);
                    const tag_val = c.LLVMConstInt(header_ty, ei.tag, 0);
                    const payload_val = self.resolveRef(ei.payload);

                    // alloca union, store tag, bitcast payload area, store payload
                    const tmp = c.LLVMBuildAlloca(self.builder, union_ty, "ei.tmp");
                    // Store tag at field 0
                    const tag_ptr = c.LLVMBuildStructGEP2(self.builder, union_ty, tmp, 0, "ei.tagp");
                    _ = c.LLVMBuildStore(self.builder, tag_val, tag_ptr);
                    // Store payload at field 1 (bitcast the byte array to payload type)
                    const payload_ptr = c.LLVMBuildStructGEP2(self.builder, union_ty, tmp, 1, "ei.pp");
                    const payload_typed_ptr = c.LLVMBuildBitCast(self.builder, payload_ptr, self.cached_ptr, "ei.pcast");
                    _ = c.LLVMBuildStore(self.builder, payload_val, payload_typed_ptr);
                    // Load the whole union value
                    self.mapRef(c.LLVMBuildLoad2(self.builder, union_ty, tmp, "ei.val"));
                }
            },
            .enum_tag => |un| {
                const val = self.resolveRef(un.operand);
                // Check if this is a plain enum (integer) or tagged union (struct with tag at 0)
                const val_ty = c.LLVMTypeOf(val);
                const kind = c.LLVMGetTypeKind(val_ty);
                if (kind == c.LLVMStructTypeKind) {
                    // Tagged union — extract field 0 (tag)
                    var tag = c.LLVMBuildExtractValue(self.builder, val, 0, "etag");
                    // Truncate to declared tag width if needed (e.g. i64 → i32 for u32 tags)
                    // This is essential for FFI unions where the i64 tag slot contains
                    // a smaller tag + uninitialized padding (e.g. SDL_Event's u32 type + u32 reserved)
                    const target_ty = self.toLLVMType(instruction.ty);
                    const extracted_bits = c.LLVMGetIntTypeWidth(c.LLVMTypeOf(tag));
                    const target_bits = c.LLVMGetIntTypeWidth(target_ty);
                    if (target_bits < extracted_bits) {
                        tag = c.LLVMBuildTrunc(self.builder, tag, target_ty, "etag.trunc");
                    }
                    self.mapRef(tag);
                } else {
                    // Plain enum — the value IS the tag
                    self.mapRef(val);
                }
            },
            .enum_payload => |fa| {
                const base = self.resolveRef(fa.base);
                const result_ty = self.toLLVMType(instruction.ty);
                const base_ty = c.LLVMTypeOf(base);
                const base_kind = c.LLVMGetTypeKind(base_ty);
                if (base_kind == c.LLVMStructTypeKind) {
                    // Tagged union: alloca, store, GEP field 1 (payload area), bitcast, load
                    const tmp = c.LLVMBuildAlloca(self.builder, base_ty, "ep.tmp");
                    _ = c.LLVMBuildStore(self.builder, base, tmp);
                    const payload_ptr = c.LLVMBuildStructGEP2(self.builder, base_ty, tmp, 1, "ep.pp");
                    const typed_ptr = c.LLVMBuildBitCast(self.builder, payload_ptr, self.cached_ptr, "ep.cast");
                    self.mapRef(c.LLVMBuildLoad2(self.builder, result_ty, typed_ptr, "ep.val"));
                } else {
                    self.mapRef(c.LLVMGetUndef(result_ty));
                }
            },

            // ── Union ops ────────────────────────────────────────────
            .union_get => |fa| {
                const base = self.resolveRef(fa.base);
                const result_ty = self.toLLVMType(instruction.ty);
                // Union field access: reinterpret the union's data area as the target type
                const base_ty = c.LLVMTypeOf(base);
                const kind = c.LLVMGetTypeKind(base_ty);
                if (kind == c.LLVMStructTypeKind) {
                    // Tagged union { header, payload_bytes } — access payload at field 1
                    const tmp = c.LLVMBuildAlloca(self.builder, base_ty, "ug.tmp");
                    _ = c.LLVMBuildStore(self.builder, base, tmp);
                    const payload_ptr = c.LLVMBuildStructGEP2(self.builder, base_ty, tmp, 1, "ug.pp");
                    self.mapRef(c.LLVMBuildLoad2(self.builder, result_ty, payload_ptr, "ug.val"));
                } else {
                    // Untagged union [N x i8] — alloca, store, reinterpret-load
                    const tmp = c.LLVMBuildAlloca(self.builder, base_ty, "ug.tmp");
                    _ = c.LLVMBuildStore(self.builder, base, tmp);
                    self.mapRef(c.LLVMBuildLoad2(self.builder, result_ty, tmp, "ug.val"));
                }
            },
            .union_gep => |fa| {
                const base_ptr = self.resolveRef(fa.base);
                const base_ty_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(base_ptr));
                if (base_ty_kind == c.LLVMPointerTypeKind) {
                    const union_llvm_ty = if (fa.base_type) |bt|
                        self.toLLVMType(self.resolveAggregate(bt))
                    else
                        self.resolveGepStructType(fa.base, instruction);
                    const st_kind = c.LLVMGetTypeKind(union_llvm_ty);
                    if (st_kind == c.LLVMStructTypeKind) {
                        // Tagged union — payload is at field 1
                        const payload_ptr = c.LLVMBuildStructGEP2(self.builder, union_llvm_ty, base_ptr, 1, "ugep.pp");
                        self.mapRef(payload_ptr);
                    } else {
                        // Untagged union — data starts at offset 0
                        self.mapRef(base_ptr);
                    }
                } else {
                    self.mapRef(c.LLVMGetUndef(self.cached_ptr));
                }
            },

            // ── Array/Slice ops ───────────────────────────────────────
            .index_get => |bin| {
                const base = self.resolveRef(bin.lhs);
                const idx = self.resolveRef(bin.rhs);
                const base_ty = c.LLVMTypeOf(base);
                const kind = c.LLVMGetTypeKind(base_ty);
                if (kind == c.LLVMVectorTypeKind or kind == c.LLVMScalableVectorTypeKind) {
                    // Vector — use extractelement
                    // Coerce index to i32 if needed
                    const idx32 = self.coerceArg(idx, self.cached_i32);
                    self.mapRef(c.LLVMBuildExtractElement(self.builder, base, idx32, "ve"));
                } else if (kind == c.LLVMArrayTypeKind) {
                    // Fixed-size array value — alloca, store, GEP, load
                    const tmp = c.LLVMBuildAlloca(self.builder, base_ty, "ig.tmp");
                    _ = c.LLVMBuildStore(self.builder, base, tmp);
                    const elem_ty = self.toLLVMType(instruction.ty);
                    var indices = [_]c.LLVMValueRef{ c.LLVMConstInt(self.cached_i64, 0, 0), idx };
                    const ptr = c.LLVMBuildGEP2(self.builder, base_ty, tmp, &indices, 2, "ig.ptr");
                    self.mapRef(c.LLVMBuildLoad2(self.builder, elem_ty, ptr, "ig.val"));
                } else if (kind == c.LLVMPointerTypeKind) {
                    // Pointer (many-pointer or raw ptr) — GEP + load
                    const elem_ty = self.toLLVMType(instruction.ty);
                    var indices = [_]c.LLVMValueRef{idx};
                    const ptr = c.LLVMBuildGEP2(self.builder, elem_ty, base, &indices, 1, "ig.ptr");
                    self.mapRef(c.LLVMBuildLoad2(self.builder, elem_ty, ptr, "ig.val"));
                } else if (kind == c.LLVMStructTypeKind) {
                    // Slice/string {ptr, len} — extract ptr, GEP, load
                    const data = c.LLVMBuildExtractValue(self.builder, base, 0, "ig.data");
                    const elem_ty = self.toLLVMType(instruction.ty);
                    var indices = [_]c.LLVMValueRef{idx};
                    const ptr = c.LLVMBuildGEP2(self.builder, elem_ty, data, &indices, 1, "ig.ptr");
                    self.mapRef(c.LLVMBuildLoad2(self.builder, elem_ty, ptr, "ig.val"));
                } else {
                    // Non-aggregate base (lowering error) — emit undef
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                }
            },
            .index_gep => |bin| {
                const base = self.resolveRef(bin.lhs);
                const idx = self.resolveRef(bin.rhs);
                const base_ty = c.LLVMTypeOf(base);
                const kind = c.LLVMGetTypeKind(base_ty);
                if (kind == c.LLVMArrayTypeKind) {
                    // Fixed-size array value — alloca, store, GEP
                    const tmp = c.LLVMBuildAlloca(self.builder, base_ty, "igp.tmp");
                    _ = c.LLVMBuildStore(self.builder, base, tmp);
                    var indices = [_]c.LLVMValueRef{ c.LLVMConstInt(self.cached_i64, 0, 0), idx };
                    self.mapRef(c.LLVMBuildGEP2(self.builder, base_ty, tmp, &indices, 2, "igp.ptr"));
                } else if (kind == c.LLVMPointerTypeKind) {
                    // Pointer — GEP with proper element type
                    const gep_elem = blk: {
                        // instruction.ty is the result type (ptr to element)
                        // Resolve the pointee type for the GEP element size
                        const info = self.ir_mod.types.get(instruction.ty);
                        break :blk switch (info) {
                            .pointer => |p| self.toLLVMType(p.pointee),
                            .many_pointer => |p| self.toLLVMType(p.element),
                            else => self.cached_i8, // fallback
                        };
                    };
                    var indices = [_]c.LLVMValueRef{idx};
                    self.mapRef(c.LLVMBuildGEP2(self.builder, gep_elem, base, &indices, 1, "igp.ptr"));
                } else if (kind == c.LLVMStructTypeKind) {
                    // Slice/string {ptr, len} — extract ptr, GEP with proper element type
                    const data = c.LLVMBuildExtractValue(self.builder, base, 0, "igp.data");
                    const gep_elem = blk: {
                        const info = self.ir_mod.types.get(instruction.ty);
                        break :blk switch (info) {
                            .pointer => |p| self.toLLVMType(p.pointee),
                            .many_pointer => |p| self.toLLVMType(p.element),
                            else => self.cached_i8,
                        };
                    };
                    var indices = [_]c.LLVMValueRef{idx};
                    self.mapRef(c.LLVMBuildGEP2(self.builder, gep_elem, data, &indices, 1, "igp.ptr"));
                } else {
                    self.mapRef(c.LLVMGetUndef(self.cached_ptr));
                }
            },
            .length => |un| {
                const val = self.resolveRef(un.operand);
                const val_ty = c.LLVMTypeOf(val);
                const kind = c.LLVMGetTypeKind(val_ty);
                if (kind == c.LLVMArrayTypeKind) {
                    const len = c.LLVMGetArrayLength2(val_ty);
                    self.mapRef(c.LLVMConstInt(self.cached_i64, len, 0));
                } else if (kind == c.LLVMStructTypeKind) {
                    // Slice/string {ptr, len} — extract field 1 (len)
                    self.mapRef(c.LLVMBuildExtractValue(self.builder, val, 1, "len"));
                } else {
                    self.mapRef(c.LLVMGetUndef(self.cached_i64));
                }
            },
            .data_ptr => |un| {
                const val = self.resolveRef(un.operand);
                const val_ty = c.LLVMTypeOf(val);
                const kind = c.LLVMGetTypeKind(val_ty);
                if (kind == c.LLVMStructTypeKind) {
                    self.mapRef(c.LLVMBuildExtractValue(self.builder, val, 0, "dptr"));
                } else {
                    self.mapRef(c.LLVMGetUndef(self.cached_ptr));
                }
            },
            .subslice => |ss| {
                const base = self.resolveRef(ss.base);
                var lo = self.resolveRef(ss.lo);
                var hi = self.resolveRef(ss.hi);
                // Normalize lo/hi to i64 for consistent arithmetic (indices are unsigned)
                if (c.LLVMTypeOf(lo) != self.cached_i64) {
                    lo = c.LLVMBuildZExt(self.builder, lo, self.cached_i64, "ss.lo64");
                }
                if (c.LLVMTypeOf(hi) != self.cached_i64) {
                    hi = c.LLVMBuildZExt(self.builder, hi, self.cached_i64, "ss.hi64");
                }
                const base_ty = c.LLVMTypeOf(base);
                const base_kind = c.LLVMGetTypeKind(base_ty);
                const slice_ty = self.toLLVMType(instruction.ty);
                // Resolve element type from the result slice type for correct GEP stride
                const elem_ty = blk: {
                    const info = self.ir_mod.types.get(instruction.ty);
                    break :blk switch (info) {
                        .slice => |s| self.toLLVMType(s.element),
                        else => self.cached_i8,
                    };
                };
                if (base_kind == c.LLVMStructTypeKind) {
                    // Slice/string: extract data ptr, GEP by lo
                    const data = c.LLVMBuildExtractValue(self.builder, base, 0, "ss.data");
                    var lo_indices = [_]c.LLVMValueRef{lo};
                    const new_ptr = c.LLVMBuildGEP2(self.builder, elem_ty, data, &lo_indices, 1, "ss.ptr");
                    var new_len = c.LLVMBuildSub(self.builder, hi, lo, "ss.len");
                    // Ensure length is i64 for slice struct {ptr, i64}
                    if (c.LLVMTypeOf(new_len) != self.cached_i64) {
                        new_len = c.LLVMBuildSExt(self.builder, new_len, self.cached_i64, "ss.ext");
                    }
                    var result = c.LLVMGetUndef(slice_ty);
                    result = c.LLVMBuildInsertValue(self.builder, result, new_ptr, 0, "ss.wptr");
                    result = c.LLVMBuildInsertValue(self.builder, result, new_len, 1, "ss.wlen");
                    self.mapRef(result);
                } else if (base_kind == c.LLVMArrayTypeKind) {
                    // Array: alloca, GEP to element at lo, compute len
                    const tmp = c.LLVMBuildAlloca(self.builder, base_ty, "ss.arr");
                    _ = c.LLVMBuildStore(self.builder, base, tmp);
                    var indices = [_]c.LLVMValueRef{ c.LLVMConstInt(self.cached_i64, 0, 0), lo };
                    const new_ptr = c.LLVMBuildGEP2(self.builder, base_ty, tmp, &indices, 2, "ss.ptr");
                    var new_len = c.LLVMBuildSub(self.builder, hi, lo, "ss.len");
                    // Ensure length is i64 for slice struct {ptr, i64}
                    if (c.LLVMTypeOf(new_len) != self.cached_i64) {
                        new_len = c.LLVMBuildSExt(self.builder, new_len, self.cached_i64, "ss.ext");
                    }
                    var result = c.LLVMGetUndef(slice_ty);
                    result = c.LLVMBuildInsertValue(self.builder, result, new_ptr, 0, "ss.wptr");
                    result = c.LLVMBuildInsertValue(self.builder, result, new_len, 1, "ss.wlen");
                    self.mapRef(result);
                } else {
                    self.mapRef(c.LLVMGetUndef(slice_ty));
                }
            },
            .array_to_slice => |un| {
                const arr = self.resolveRef(un.operand);
                const arr_ty = c.LLVMTypeOf(arr);
                const arr_kind = c.LLVMGetTypeKind(arr_ty);
                if (arr_kind == c.LLVMArrayTypeKind) {
                    const len = c.LLVMGetArrayLength2(arr_ty);
                    const tmp = c.LLVMBuildAlloca(self.builder, arr_ty, "a2s.tmp");
                    _ = c.LLVMBuildStore(self.builder, arr, tmp);
                    var indices = [_]c.LLVMValueRef{ c.LLVMConstInt(self.cached_i64, 0, 0), c.LLVMConstInt(self.cached_i64, 0, 0) };
                    const elem_ptr = c.LLVMBuildGEP2(self.builder, arr_ty, tmp, &indices, 2, "a2s.ptr");
                    const slice_ty = self.toLLVMType(instruction.ty);
                    var result = c.LLVMGetUndef(slice_ty);
                    result = c.LLVMBuildInsertValue(self.builder, result, elem_ptr, 0, "a2s.wptr");
                    const len_val = c.LLVMConstInt(self.cached_i64, len, 0);
                    result = c.LLVMBuildInsertValue(self.builder, result, len_val, 1, "a2s.wlen");
                    self.mapRef(result);
                } else {
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                }
            },

            // ── Call extensions ───────────────────────────────────────
            .call_builtin => |bi| {
                // Builtins that map to libc functions or LLVM intrinsics
                switch (bi.builtin) {
                    .sqrt, .sin, .cos, .floor => {
                        const val = self.resolveRef(bi.args[0]);
                        const val_ty = c.LLVMTypeOf(val);
                        const val_kind = c.LLVMGetTypeKind(val_ty);
                        if (val_kind == c.LLVMFloatTypeKind) {
                            const f = self.getOrDeclareMathF32(bi.builtin);
                            var args = [_]c.LLVMValueRef{val};
                            self.mapRef(c.LLVMBuildCall2(self.builder, self.getMathF32Type(), f, &args, 1, @tagName(bi.builtin)));
                        } else {
                            const coerced = if (val_kind != c.LLVMDoubleTypeKind) self.coerceArg(val, self.cached_f64) else val;
                            const f = self.getOrDeclareMathF64(bi.builtin);
                            var args = [_]c.LLVMValueRef{coerced};
                            self.mapRef(c.LLVMBuildCall2(self.builder, self.getMathF64Type(), f, &args, 1, @tagName(bi.builtin)));
                        }
                    },
                    .out => {
                        // out(str): extract ptr and len from string fat pointer, call write(1, ptr, len)
                        const str_val = self.resolveRef(bi.args[0]);
                        const raw_ptr = c.LLVMBuildExtractValue(self.builder, str_val, 0, "str.ptr");
                        const str_len = c.LLVMBuildExtractValue(self.builder, str_val, 1, "str.len");
                        // On wasm32, count param is i32 (size_t)
                        const count = if (self.target_config.isWasm32())
                            c.LLVMBuildTrunc(self.builder, str_len, self.cached_i32, "len.tr")
                        else
                            str_len;
                        const write_fn = self.getOrDeclareWrite();
                        var write_args = [_]c.LLVMValueRef{
                            c.LLVMConstInt(self.cached_i32, 1, 0), // fd = stdout
                            raw_ptr,
                            count,
                        };
                        _ = c.LLVMBuildCall2(self.builder, self.getWriteType(), write_fn, &write_args, 3, "");
                        self.advanceRefCounter();
                    },
                    .type_name => {
                        // Dynamic `type_name(t)` at runtime: extract
                        // the TypeId from the arg (an Any-boxed Type
                        // value: tag=`.s64.index()`, value=tid), GEP
                        // into the compiler-emitted `__sx_type_names`
                        // global, load the string. The arg's LLVM
                        // shape is the `{i64, i64}` Any aggregate
                        // (because the IR-side arg type is `.any`
                        // when boxed); for unboxed direct call sites
                        // (the arg IR type is `.s64` from
                        // `const_type`), the value IS the TypeId
                        // index directly.
                        const arg_ref = bi.args[0];
                        const arg_val = self.resolveRef(arg_ref);
                        const arg_ir_ty = self.getRefIRType(arg_ref) orelse @import("types.zig").TypeId.s64;
                        const tid_idx = blk: {
                            if (arg_ir_ty == .any) {
                                // Boxed: extract value field.
                                break :blk c.LLVMBuildExtractValue(self.builder, arg_val, 1, "tn.tid");
                            }
                            // Bare i64 (TypeId index).
                            break :blk arg_val;
                        };
                        const arr_global = self.getOrBuildTypeNameArray();
                        const arr_len = self.type_name_array_len;
                        const string_ty = self.getStringStructType();
                        const arr_ty = c.LLVMArrayType(string_ty, arr_len);
                        const zero = c.LLVMConstInt(self.cached_i64, 0, 0);
                        var indices = [2]c.LLVMValueRef{ zero, tid_idx };
                        const gep = c.LLVMBuildInBoundsGEP2(self.builder, arr_ty, arr_global, &indices, 2, "tn.gep");
                        const result = c.LLVMBuildLoad2(self.builder, string_ty, gep, "tn.load");
                        self.mapRef(result);
                    },
                    .type_eq => {
                        // Dynamic `type_eq(a, b)` — both args are
                        // Type values. Extract TypeId from each Any
                        // box (or use directly if `.s64`-typed),
                        // icmp eq.
                        const a = blk: {
                            const v = self.resolveRef(bi.args[0]);
                            const ty = self.getRefIRType(bi.args[0]) orelse @import("types.zig").TypeId.s64;
                            if (ty == .any) break :blk c.LLVMBuildExtractValue(self.builder, v, 1, "te.a");
                            break :blk v;
                        };
                        const b = blk: {
                            const v = self.resolveRef(bi.args[1]);
                            const ty = self.getRefIRType(bi.args[1]) orelse @import("types.zig").TypeId.s64;
                            if (ty == .any) break :blk c.LLVMBuildExtractValue(self.builder, v, 1, "te.b");
                            break :blk v;
                        };
                        const eq_res = c.LLVMBuildICmp(self.builder, c.LLVMIntEQ, a, b, "te.eq");
                        self.mapRef(eq_res);
                    },
                    .has_impl => {
                        // Runtime has_impl needs a protocol-map
                        // snapshot — not wired yet. Silent false for
                        // now; the lower-time fold via
                        // `tryConstBoolCondition` covers every
                        // statically-resolvable call.
                        self.mapRef(c.LLVMConstInt(self.cached_i1, 0, 0));
                    },
                    else => {
                        // size_of, cast — handled by lowering or codegen glue
                        self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                    },
                }
            },
            .compiler_call => {
                // Compiler hooks are comptime-only; if one reaches emission, produce undef
                self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
            },
            .call_closure => |call_op| {
                // Closure: { fn_ptr, env }.
                //
                // ABI (when module.has_implicit_ctx):
                //   trampoline signature: (__sx_ctx, env, args...)
                //   call_op.args[0]      = __sx_ctx (prepended by lowering)
                //   call_op.args[1..]    = user args
                //   extracted env_ptr     = inserted at LLVM slot 1
                //
                // ABI (without implicit_ctx):
                //   trampoline signature: (env, args...)
                //   call_op.args         = user args (no ctx prepend)
                //   extracted env_ptr     = inserted at LLVM slot 0
                const closure = self.resolveRef(call_op.callee);
                const cl_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(closure));
                if (cl_kind != c.LLVMStructTypeKind) {
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                    return;
                }
                const fn_ptr = c.LLVMBuildExtractValue(self.builder, closure, 0, "cl.fn");
                const env_ptr = c.LLVMBuildExtractValue(self.builder, closure, 1, "cl.env");

                // Get the closure's declared parameter types from the IR type system
                const callee_ir_ty = self.getRefIRType(call_op.callee);
                const closure_params: ?[]const @import("types.zig").TypeId = if (callee_ir_ty) |cty| blk: {
                    if (!cty.isBuiltin()) {
                        const ci = self.ir_mod.types.get(cty);
                        if (ci == .closure) break :blk ci.closure.params;
                    }
                    break :blk null;
                } else null;

                const has_ctx = self.ir_mod.has_implicit_ctx;
                const user_args_offset_in_op: usize = if (has_ctx) 1 else 0;
                const user_args_count: usize = call_op.args.len -| user_args_offset_in_op;
                const ctx_slots: usize = if (has_ctx) 1 else 0;
                const total_args = ctx_slots + 1 + user_args_count; // [ctx?] + env + user_args

                const args = self.alloc.alloc(c.LLVMValueRef, total_args) catch unreachable;
                defer self.alloc.free(args);
                if (has_ctx) {
                    args[0] = self.resolveRef(call_op.args[0]); // ctx
                }
                args[ctx_slots] = env_ptr;
                for (0..user_args_count) |j| {
                    args[ctx_slots + 1 + j] = self.resolveRef(call_op.args[user_args_offset_in_op + j]);
                }

                // Build function type using declared param types (not arg types).
                // closure_params is user-visible (no ctx, no env), so they line
                // up with args[ctx_slots+1..].
                const ret_ty = self.toLLVMType(instruction.ty);
                const param_tys = self.alloc.alloc(c.LLVMTypeRef, total_args) catch unreachable;
                defer self.alloc.free(param_tys);
                if (has_ctx) param_tys[0] = self.cached_ptr; // __sx_ctx
                param_tys[ctx_slots] = self.cached_ptr; // env
                if (closure_params) |cp| {
                    for (0..user_args_count) |j| {
                        const param_ir_ty = if (j < cp.len) cp[j] else null;
                        if (param_ir_ty) |pty| {
                            const llvm_pty = self.toLLVMType(pty);
                            param_tys[ctx_slots + 1 + j] = llvm_pty;
                            args[ctx_slots + 1 + j] = self.coerceArg(args[ctx_slots + 1 + j], llvm_pty);
                        } else {
                            param_tys[ctx_slots + 1 + j] = c.LLVMTypeOf(args[ctx_slots + 1 + j]);
                        }
                    }
                } else {
                    for (0..user_args_count) |j| {
                        param_tys[ctx_slots + 1 + j] = c.LLVMTypeOf(args[ctx_slots + 1 + j]);
                    }
                }
                const fn_ty = c.LLVMFunctionType(ret_ty, param_tys.ptr, @intCast(total_args), 0);

                const is_void = instruction.ty == .void;
                const result = c.LLVMBuildCall2(self.builder, fn_ty, fn_ptr, args.ptr, @intCast(total_args), if (is_void) "" else "ccall");
                if (!is_void) {
                    self.mapRef(result);
                } else {
                    self.advanceRefCounter();
                }
            },

            // ── Tuple ops ────────────────────────────────────────────
            .tuple_init => |agg| {
                const tuple_ty = self.toLLVMType(instruction.ty);
                var result = c.LLVMGetUndef(tuple_ty);
                for (agg.fields, 0..) |field_ref, i| {
                    const field_val = self.resolveRef(field_ref);
                    result = c.LLVMBuildInsertValue(self.builder, result, field_val, @intCast(i), "ti");
                }
                self.mapRef(result);
            },
            .tuple_get => |fa| {
                const base = self.resolveRef(fa.base);
                self.mapRef(c.LLVMBuildExtractValue(self.builder, base, @intCast(fa.field_index), "tg"));
            },

            // ── Optional ops ─────────────────────────────────────────
            .optional_wrap => |un| {
                var val = self.resolveRef(un.operand);
                const opt_ty = self.toLLVMType(instruction.ty);
                const opt_kind = c.LLVMGetTypeKind(opt_ty);
                if (opt_kind == c.LLVMPointerTypeKind) {
                    // ?*T — pointer is the optional itself (null = none)
                    self.mapRef(val);
                } else if (opt_kind == c.LLVMStructTypeKind) {
                    // Distinguish {T, i1} (real optional) from {ptr, ptr} (?Closure)
                    const num_fields = c.LLVMCountStructElementTypes(opt_ty);
                    const last_field_ty = if (num_fields > 0) c.LLVMStructGetTypeAtIndex(opt_ty, num_fields - 1) else self.cached_i1;
                    if (last_field_ty == self.cached_i1) {
                        // ?T → { T, i1 } — wrap value + true flag
                        const inner_ty = c.LLVMStructGetTypeAtIndex(opt_ty, 0);
                        val = self.coerceArg(val, inner_ty);
                        var result = c.LLVMGetUndef(opt_ty);
                        result = c.LLVMBuildInsertValue(self.builder, result, val, 0, "ow.val");
                        result = c.LLVMBuildInsertValue(self.builder, result, c.LLVMConstInt(self.cached_i1, 1, 0), 1, "ow.has");
                        self.mapRef(result);
                    } else {
                        // ?Closure → closure struct IS the optional, just pass through
                        self.mapRef(val);
                    }
                } else {
                    self.mapRef(val);
                }
            },
            .optional_unwrap => |un| {
                const val = self.resolveRef(un.operand);
                const val_ty = c.LLVMTypeOf(val);
                const kind = c.LLVMGetTypeKind(val_ty);
                if (kind == c.LLVMStructTypeKind) {
                    // Distinguish {T, i1} (real optional) from {ptr, ptr} (?Closure)
                    const num_fields = c.LLVMCountStructElementTypes(val_ty);
                    const last_field_ty = if (num_fields > 0) c.LLVMStructGetTypeAtIndex(val_ty, num_fields - 1) else self.cached_i1;
                    if (last_field_ty == self.cached_i1) {
                        // { T, i1 } → extract field 0
                        self.mapRef(c.LLVMBuildExtractValue(self.builder, val, 0, "ou.val"));
                    } else {
                        // ?Closure → the struct itself is the value
                        self.mapRef(val);
                    }
                } else {
                    // ?*T → pointer is the value itself
                    self.mapRef(val);
                }
            },
            .optional_has_value => |un| {
                const val = self.resolveRef(un.operand);
                const val_ty = c.LLVMTypeOf(val);
                const kind = c.LLVMGetTypeKind(val_ty);
                if (kind == c.LLVMStructTypeKind) {
                    // Distinguish {T, i1} (real optional) from {ptr, ptr} (?Closure)
                    const num_fields = c.LLVMCountStructElementTypes(val_ty);
                    const last_field_ty = if (num_fields > 0) c.LLVMStructGetTypeAtIndex(val_ty, num_fields - 1) else self.cached_i1;
                    if (last_field_ty == self.cached_i1) {
                        // { T, i1 } → extract has_value flag
                        self.mapRef(c.LLVMBuildExtractValue(self.builder, val, num_fields - 1, "oh.has"));
                    } else {
                        // ?Closure {fn_ptr, env} → check if fn_ptr is null
                        const fn_ptr = c.LLVMBuildExtractValue(self.builder, val, 0, "oh.fn");
                        self.mapRef(c.LLVMBuildICmp(self.builder, c.LLVMIntNE, fn_ptr, c.LLVMConstNull(c.LLVMTypeOf(fn_ptr)), "oh.nn"));
                    }
                } else {
                    // ?*T → compare with null
                    const is_nonnull = c.LLVMBuildICmp(self.builder, c.LLVMIntNE, val, c.LLVMConstNull(val_ty), "oh.nn");
                    self.mapRef(is_nonnull);
                }
            },
            .optional_coalesce => |bin| {
                // a ?? b — if a has value, use a's value; otherwise use b
                const a = self.resolveRef(bin.lhs);
                var b_val = self.resolveRef(bin.rhs);
                const a_ty = c.LLVMTypeOf(a);
                const kind = c.LLVMGetTypeKind(a_ty);
                if (kind == c.LLVMStructTypeKind) {
                    const n_fields = c.LLVMCountStructElementTypes(a_ty);
                    const f1_ty = if (n_fields >= 2) c.LLVMStructGetTypeAtIndex(a_ty, 1) else null;
                    const is_ti1 = if (f1_ty) |ft| c.LLVMGetTypeKind(ft) == c.LLVMIntegerTypeKind and c.LLVMGetIntTypeWidth(ft) == 1 else false;
                    if (is_ti1) {
                        // Standard optional {T, i1}: extract has_value and unwrap
                        const has = c.LLVMBuildExtractValue(self.builder, a, 1, "oc.has");
                        const unwrapped = c.LLVMBuildExtractValue(self.builder, a, 0, "oc.val");
                        const uw_ty = c.LLVMTypeOf(unwrapped);
                        const b_ty = c.LLVMTypeOf(b_val);
                        if (uw_ty != b_ty) {
                            b_val = self.coerceArg(b_val, uw_ty);
                        }
                        self.mapRef(c.LLVMBuildSelect(self.builder, has, unwrapped, b_val, "oc.sel"));
                    } else {
                        // ?Closure {fn_ptr, env}: check if fn_ptr is null
                        const fn_ptr = c.LLVMBuildExtractValue(self.builder, a, 0, "oc.fn");
                        const is_nonnull = c.LLVMBuildICmp(self.builder, c.LLVMIntNE, fn_ptr, c.LLVMConstNull(c.LLVMTypeOf(fn_ptr)), "oc.nn");
                        // Select the full closure struct, not just the fn_ptr
                        self.mapRef(c.LLVMBuildSelect(self.builder, is_nonnull, a, b_val, "oc.sel"));
                    }
                } else {
                    // ?*T — select on null
                    const is_nonnull = c.LLVMBuildICmp(self.builder, c.LLVMIntNE, a, c.LLVMConstNull(a_ty), "oc.nn");
                    self.mapRef(c.LLVMBuildSelect(self.builder, is_nonnull, a, b_val, "oc.sel"));
                }
            },

            // ── Box/Unbox Any ────────────────────────────────────────
            .box_any => |ba| {
                const val = self.resolveRef(ba.operand);
                const any_ty = self.getAnyStructType();
                // Any = { type_tag: i64, value: i64 }
                const tag = c.LLVMConstInt(self.cached_i64, self.anyTag(ba.source_type), 0);
                // Bitcast value to i64, using SExt for signed types, ZExt otherwise
                const is_signed = self.isSignedTypeEx(ba.source_type);
                const val_as_i64 = if (is_signed) self.coerceToI64Signed(val) else self.coerceToI64(val);
                var result = c.LLVMGetUndef(any_ty);
                result = c.LLVMBuildInsertValue(self.builder, result, tag, 0, "ba.tag");
                result = c.LLVMBuildInsertValue(self.builder, result, val_as_i64, 1, "ba.val");
                self.mapRef(result);
            },
            .unbox_any => |un| {
                const any_val = self.resolveRef(un.operand);
                const any_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(any_val));
                if (any_kind == c.LLVMStructTypeKind) {
                    const raw = c.LLVMBuildExtractValue(self.builder, any_val, 1, "ua.raw");
                    const target_ty = self.toLLVMType(instruction.ty);
                    self.mapRef(self.coerceFromI64(raw, target_ty));
                } else {
                    self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
                }
            },

            // ── Reflection ops ──────────────────────────────────────
            .field_name_get => |fr| {
                // Build global string array for this struct's field names, then GEP at runtime index
                const global = self.getOrBuildFieldNameArray(fr.struct_type);
                const idx = self.resolveRef(fr.index);
                const string_ty = self.getStringStructType();
                // Get struct field count for array type
                const field_info = self.ir_mod.types.get(fr.struct_type);
                const field_count: u32 = switch (field_info) {
                    .@"struct" => |s| @intCast(s.fields.len),
                    .@"union" => |u| @intCast(u.fields.len),
                    .tagged_union => |u| @intCast(u.fields.len),
                    .@"enum" => |e| @intCast(e.variants.len),
                    else => 0,
                };
                const array_ty = c.LLVMArrayType(string_ty, field_count);
                const zero = c.LLVMConstInt(self.cached_i64, 0, 0);
                var indices = [2]c.LLVMValueRef{ zero, idx };
                const gep = c.LLVMBuildInBoundsGEP2(self.builder, array_ty, global, &indices, 2, "fn.gep");
                const result = c.LLVMBuildLoad2(self.builder, string_ty, gep, "fn.load");
                self.mapRef(result);
            },
            .field_value_get => |fr| {
                // Switch on index, each case: extractvalue field k → box as Any
                self.emitFieldValueGet(fr, func_idx);
            },
            .error_tag_name_get => |u| {
                // Tag id → name: GEP into the always-linked tag-name table at
                // the runtime tag id (the error-set value, a u32). Out-of-range
                // ids can't occur — ids come from the same registry the table
                // is built from — so no bounds branch is needed.
                const global = self.getOrBuildTagNameArray();
                const tag_raw = self.resolveRef(u.operand);
                const idx = c.LLVMBuildZExt(self.builder, tag_raw, self.cached_i64, "etn.idx");
                const string_ty = self.getStringStructType();
                const n: u32 = @intCast(self.ir_mod.types.tags.names.items.len);
                const array_ty = c.LLVMArrayType(string_ty, n);
                const zero = c.LLVMConstInt(self.cached_i64, 0, 0);
                var indices = [2]c.LLVMValueRef{ zero, idx };
                const gep = c.LLVMBuildInBoundsGEP2(self.builder, array_ty, global, &indices, 2, "etn.gep");
                const result = c.LLVMBuildLoad2(self.builder, string_ty, gep, "etn.load");
                self.mapRef(result);
            },

            // ── Switch branch ────────────────────────────────────────
            .switch_br => |sw| {
                const operand = self.resolveRef(sw.operand);
                const default_bb = self.getBlock(func_idx, sw.default);
                const switch_inst = c.LLVMBuildSwitch(self.builder, operand, default_bb, @intCast(sw.cases.len));
                for (sw.cases) |case| {
                    const case_val = c.LLVMConstInt(c.LLVMTypeOf(operand), @bitCast(case.value), 0);
                    const case_bb = self.getBlock(func_idx, case.target);
                    c.LLVMAddCase(switch_inst, case_val, case_bb);
                }
                self.advanceRefCounter();
            },

            // ── Closure creation ─────────────────────────────────────
            .closure_create => |cc| {
                const fn_val = self.func_map.get(cc.func.index()) orelse c.LLVMGetUndef(self.cached_ptr);
                const env_val = if (cc.env.isNone()) c.LLVMConstNull(self.cached_ptr) else self.resolveRef(cc.env);
                const closure_ty = self.getClosureStructType();
                var result = c.LLVMGetUndef(closure_ty);
                result = c.LLVMBuildInsertValue(self.builder, result, fn_val, 0, "cc.fn");
                result = c.LLVMBuildInsertValue(self.builder, result, env_val, 1, "cc.env");
                self.mapRef(result);
            },

            // ── Vector ops ───────────────────────────────────────────
            .vec_splat => |un| {
                const scalar = self.resolveRef(un.operand);
                const vec_ty = self.toLLVMType(instruction.ty);
                const vec_len = c.LLVMGetVectorSize(vec_ty);
                // Build a splat: insertelement into undef for each lane
                var result = c.LLVMGetUndef(vec_ty);
                var i: c_uint = 0;
                while (i < vec_len) : (i += 1) {
                    const idx_val = c.LLVMConstInt(self.cached_i32, i, 0);
                    result = c.LLVMBuildInsertElement(self.builder, result, scalar, idx_val, "splat");
                }
                self.mapRef(result);
            },
            .vec_extract => |bin| {
                const vec = self.resolveRef(bin.lhs);
                const idx = self.resolveRef(bin.rhs);
                self.mapRef(c.LLVMBuildExtractElement(self.builder, vec, idx, "vext"));
            },
            .vec_insert => |tri| {
                const vec = self.resolveRef(tri.a);
                const idx = self.resolveRef(tri.b);
                const val = self.resolveRef(tri.c);
                self.mapRef(c.LLVMBuildInsertElement(self.builder, vec, val, idx, "vins"));
            },

            // ── Block params ─────────────────────────────────────────
            .block_param => |bp| {
                // Create a PHI node — incoming values are filled in by fixupPhiNodes
                const ty = self.toLLVMType(instruction.ty);
                const phi = c.LLVMBuildPhi(self.builder, ty, "bp");
                self.pending_phis.append(self.alloc, .{
                    .phi = phi,
                    .block_id = bp.block,
                    .param_index = bp.param_index,
                }) catch unreachable;
                self.mapRef(phi);
            },

            // ── Misc ─────────────────────────────────────────────────
            .placeholder => {
                self.mapRef(c.LLVMGetUndef(self.toLLVMType(instruction.ty)));
            },
        }
    }

    // ── Ref tracking ────────────────────────────────────────────────

    fn mapRef(self: *LLVMEmitter, val: c.LLVMValueRef) void {
        self.ref_map.put(self.ref_counter, val) catch unreachable;
        self.ref_counter += 1;
    }

    fn advanceRefCounter(self: *LLVMEmitter) void {
        self.ref_counter += 1;
    }

    fn resolveRef(self: *LLVMEmitter, ref: Ref) c.LLVMValueRef {
        if (ref.isNone()) {
            return c.LLVMGetUndef(self.cached_i64);
        }
        return self.ref_map.get(ref.index()) orelse c.LLVMGetUndef(self.cached_i64);
    }

    fn getBlock(self: *LLVMEmitter, func_idx: u32, block_id: BlockId) c.LLVMBasicBlockRef {
        const key = makeBlockKey(func_idx, block_id.index());
        return self.block_map.get(key) orelse {
            std.debug.print("getBlock: missing block func={d} block={d}\n", .{ func_idx, block_id.index() });
            unreachable;
        };
    }

    // ── Struct/union GEP helper ────────────────────────────────────────

    /// For struct_gep/union_gep: we need the LLVM type of the aggregate being pointed to.
    /// The instruction's type is the *result* (pointer to field), so we need to look at
    /// the IR instruction that produced the base pointer to find the aggregate type.
    /// As a fallback, we scan back through the ref_map to find the alloca type.
    fn getStructTypeForGep(self: *LLVMEmitter, instruction: *const Inst) c.LLVMTypeRef {
        // For GEP, the base ref points to an alloca or another pointer.
        // The instruction type is a pointer type (result of GEP), but we need the
        // aggregate type. We get it from the base pointer's allocated type.
        const fa = switch (instruction.op) {
            .struct_gep => |f| f,
            .union_gep => |f| f,
            else => unreachable,
        };
        const base_val = self.resolveRef(fa.base);
        // LLVMGetAllocatedType only works on alloca instructions
        if (c.LLVMIsAAllocaInst(base_val) != null) {
            const alloc_ty = c.LLVMGetAllocatedType(base_val);
            if (alloc_ty != null) return alloc_ty;
        }
        // Fallback: trace LLVM value chain — if base came from a load,
        // check the load's source pointer for an alloca
        if (c.LLVMIsALoadInst(base_val) != null) {
            const load_ptr = c.LLVMGetOperand(base_val, 0);
            if (load_ptr != null and c.LLVMIsAAllocaInst(load_ptr) != null) {
                const inner_alloc = c.LLVMGetAllocatedType(load_ptr);
                if (inner_alloc != null) return inner_alloc;
            }
        }
        // Fallback: look up the IR type of the base ref to find the pointee type
        const base_ir_ty = self.getRefIRType(fa.base);
        if (base_ir_ty) |ir_ty| {
            if (!ir_ty.isBuiltin()) {
                const info = self.ir_mod.types.get(ir_ty);
                switch (info) {
                    .pointer => |p| return self.toLLVMType(p.pointee),
                    else => return self.toLLVMType(ir_ty),
                }
            }
        }
        return self.cached_i64;
    }

    /// Resolve the struct LLVM type for GEP operations.
    /// Uses LLVM alloca type when available, falls back to IR type system.
    fn resolveGepStructType(self: *LLVMEmitter, base_ref: Ref, instruction: *const Inst) c.LLVMTypeRef {
        const base_val = self.resolveRef(base_ref);

        // Strategy 1: base is an alloca — get allocated type directly
        if (c.LLVMIsAAllocaInst(base_val) != null) {
            const alloc_ty = c.LLVMGetAllocatedType(base_val);
            if (alloc_ty != null) {
                const kind = c.LLVMGetTypeKind(alloc_ty);
                if (kind == c.LLVMStructTypeKind or kind == c.LLVMArrayTypeKind) return alloc_ty;
            }
        }

        // Strategy 2: Use IR type system — most accurate for chained GEPs (e.g. union_gep + struct_gep)
        const base_ir_ty = self.getRefIRType(base_ref);
        if (base_ir_ty) |ir_ty| {
            // Resolve through pointer types to find the pointee struct
            var resolved = ir_ty;
            if (!resolved.isBuiltin()) {
                const info = self.ir_mod.types.get(resolved);
                if (info == .pointer) {
                    resolved = info.pointer.pointee;
                }
            }
            if (!resolved.isBuiltin()) {
                return self.toLLVMType(resolved);
            }
        }

        // Strategy 3: base is a GEP result — get the source element type
        if (c.LLVMIsAGetElementPtrInst(base_val) != null) {
            const src_ty = c.LLVMGetGEPSourceElementType(base_val);
            if (src_ty != null) {
                const kind = c.LLVMGetTypeKind(src_ty);
                if (kind == c.LLVMStructTypeKind or kind == c.LLVMArrayTypeKind) return src_ty;
            }
        }

        // Strategy 4: old fallback
        _ = instruction;
        return self.cached_i64;
    }

    /// Resolve through pointer types to get the underlying aggregate type.
    fn resolveAggregate(self: *LLVMEmitter, ty: TypeId) TypeId {
        if (!ty.isBuiltin()) {
            const info = self.ir_mod.types.get(ty);
            if (info == .pointer) return info.pointer.pointee;
        }
        return ty;
    }

    // ── Comparison helpers ────────────────────────────────────────────

    fn emitCmp(self: *LLVMEmitter, bin: ir_inst.BinOp, _: TypeId, int_pred: c_uint, float_pred: c_uint) void {
        var lhs = self.resolveRef(bin.lhs);
        var rhs = self.resolveRef(bin.rhs);
        // Determine if float by inspecting operand LLVM type
        var lhs_ty = c.LLVMTypeOf(lhs);
        var kind = c.LLVMGetTypeKind(lhs_ty);
        var rhs_ty = c.LLVMTypeOf(rhs);
        var rhs_kind = c.LLVMGetTypeKind(rhs_ty);

        // Unwrap single-element struct (1-tuple) to scalar for comparison
        if (kind == c.LLVMStructTypeKind and rhs_kind != c.LLVMStructTypeKind) {
            if (c.LLVMCountStructElementTypes(lhs_ty) == 1) {
                lhs = c.LLVMBuildExtractValue(self.builder, lhs, 0, "tup.unwrap");
                lhs_ty = c.LLVMTypeOf(lhs);
                kind = c.LLVMGetTypeKind(lhs_ty);
            }
        } else if (rhs_kind == c.LLVMStructTypeKind and kind != c.LLVMStructTypeKind) {
            if (c.LLVMCountStructElementTypes(rhs_ty) == 1) {
                rhs = c.LLVMBuildExtractValue(self.builder, rhs, 0, "tup.unwrap");
                rhs_ty = c.LLVMTypeOf(rhs);
                rhs_kind = c.LLVMGetTypeKind(rhs_ty);
            }
        }

        // Struct types (strings, slices, tagged unions): compare fields individually
        if (kind == c.LLVMStructTypeKind and rhs_kind == c.LLVMStructTypeKind) {
            const n_fields = c.LLVMCountStructElementTypes(lhs_ty);
            if (n_fields >= 2) {
                const is_eq = (int_pred == c.LLVMIntEQ);
                const f0_l = c.LLVMBuildExtractValue(self.builder, lhs, 0, "sc.l0");
                const f0_r = c.LLVMBuildExtractValue(self.builder, rhs, 0, "sc.r0");
                const cmp0 = c.LLVMBuildICmp(self.builder, @intCast(int_pred), f0_l, f0_r, "sc.c0");

                // Check if field 1 is an array (tagged union payload) — skip comparison
                // For tagged unions {tag, [N x i8]}, the tag comparison alone is sufficient
                const f1_ty = c.LLVMStructGetTypeAtIndex(lhs_ty, 1);
                const f1_kind = c.LLVMGetTypeKind(f1_ty);
                if (f1_kind == c.LLVMArrayTypeKind) {
                    // Tagged union: compare tag only
                    self.mapRef(cmp0);
                    return;
                }

                const f1_l = c.LLVMBuildExtractValue(self.builder, lhs, 1, "sc.l1");
                const f1_r = c.LLVMBuildExtractValue(self.builder, rhs, 1, "sc.r1");
                const cmp1 = c.LLVMBuildICmp(self.builder, @intCast(int_pred), f1_l, f1_r, "sc.c1");
                const result = if (is_eq)
                    c.LLVMBuildAnd(self.builder, cmp0, cmp1, "sc.and")
                else
                    c.LLVMBuildOr(self.builder, cmp0, cmp1, "sc.or");
                self.mapRef(result);
                return;
            }
        }

        // Coerce operands to same type if needed
        if (kind == c.LLVMIntegerTypeKind and rhs_kind == c.LLVMIntegerTypeKind) {
            const lw = c.LLVMGetIntTypeWidth(lhs_ty);
            const rw = c.LLVMGetIntTypeWidth(rhs_ty);
            const is_unsigned = self.isRefUnsigned(bin.lhs) or self.isRefUnsigned(bin.rhs);
            if (is_unsigned) {
                if (lw < rw) lhs = c.LLVMBuildZExt(self.builder, lhs, rhs_ty, "cmp.ext")
                else if (rw < lw) rhs = c.LLVMBuildZExt(self.builder, rhs, lhs_ty, "cmp.ext");
            } else {
                if (lw < rw) lhs = c.LLVMBuildSExt(self.builder, lhs, rhs_ty, "cmp.ext")
                else if (rw < lw) rhs = c.LLVMBuildSExt(self.builder, rhs, lhs_ty, "cmp.ext");
            }
        }
        // Pointer vs integer: coerce int to null pointer
        if (kind == c.LLVMPointerTypeKind and rhs_kind == c.LLVMIntegerTypeKind) {
            rhs = c.LLVMConstNull(lhs_ty);
        } else if (kind == c.LLVMIntegerTypeKind and rhs_kind == c.LLVMPointerTypeKind) {
            lhs = c.LLVMConstNull(rhs_ty);
        }
        const result_kind = c.LLVMGetTypeKind(c.LLVMTypeOf(lhs));
        const result = if (result_kind == c.LLVMFloatTypeKind or result_kind == c.LLVMDoubleTypeKind)
            c.LLVMBuildFCmp(self.builder, @intCast(float_pred), lhs, rhs, "fcmp")
        else
            c.LLVMBuildICmp(self.builder, @intCast(int_pred), lhs, rhs, "icmp");
        self.mapRef(result);
    }

    fn emitCmpOrdered(self: *LLVMEmitter, bin: ir_inst.BinOp, _: TypeId, signed_pred: c_uint, unsigned_pred: c_uint, float_pred: c_uint) void {
        var lhs = self.resolveRef(bin.lhs);
        var rhs = self.resolveRef(bin.rhs);
        const lhs_ty = c.LLVMTypeOf(lhs);
        const kind = c.LLVMGetTypeKind(lhs_ty);
        // Determine signedness from IR operand type
        const is_unsigned = self.isRefUnsigned(bin.lhs) or self.isRefUnsigned(bin.rhs);
        // Coerce operands to same type if needed
        if (kind == c.LLVMIntegerTypeKind) {
            const rhs_ty = c.LLVMTypeOf(rhs);
            const rhs_kind = c.LLVMGetTypeKind(rhs_ty);
            if (rhs_kind == c.LLVMIntegerTypeKind) {
                const lw = c.LLVMGetIntTypeWidth(lhs_ty);
                const rw = c.LLVMGetIntTypeWidth(rhs_ty);
                if (is_unsigned) {
                    if (lw < rw) lhs = c.LLVMBuildZExt(self.builder, lhs, rhs_ty, "cmp.ext")
                    else if (rw < lw) rhs = c.LLVMBuildZExt(self.builder, rhs, lhs_ty, "cmp.ext");
                } else {
                    if (lw < rw) lhs = c.LLVMBuildSExt(self.builder, lhs, rhs_ty, "cmp.ext")
                    else if (rw < lw) rhs = c.LLVMBuildSExt(self.builder, rhs, lhs_ty, "cmp.ext");
                }
            }
        }
        const result = if (kind == c.LLVMFloatTypeKind or kind == c.LLVMDoubleTypeKind)
            c.LLVMBuildFCmp(self.builder, @intCast(float_pred), lhs, rhs, "fcmp")
        else if (is_unsigned)
            c.LLVMBuildICmp(self.builder, @intCast(unsigned_pred), lhs, rhs, "icmp")
        else
            c.LLVMBuildICmp(self.builder, @intCast(signed_pred), lhs, rhs, "icmp");
        self.mapRef(result);
    }

    /// String comparison via memcmp: compare length first, then content.
    fn emitStrCmp(self: *LLVMEmitter, bin: ir_inst.BinOp, is_eq: bool) void {
        const lhs = self.resolveRef(bin.lhs);
        const rhs = self.resolveRef(bin.rhs);
        const b = self.builder;
        const i32_ty = c.LLVMInt32TypeInContext(self.context);
        const i1_ty = c.LLVMInt1TypeInContext(self.context);
        const ptr_ty = c.LLVMPointerTypeInContext(self.context, 0);

        // Extract ptr and len from both fat pointers
        const lhs_ptr = c.LLVMBuildExtractValue(b, lhs, 0, "str.lp");
        const lhs_len = c.LLVMBuildExtractValue(b, lhs, 1, "str.ll");
        const rhs_ptr = c.LLVMBuildExtractValue(b, rhs, 0, "str.rp");
        const rhs_len = c.LLVMBuildExtractValue(b, rhs, 1, "str.rl");

        // Compare lengths first
        const len_eq = c.LLVMBuildICmp(b, c.LLVMIntEQ, lhs_len, rhs_len, "str.len_eq");

        // Set up basic blocks
        const cur_fn = c.LLVMGetBasicBlockParent(c.LLVMGetInsertBlock(b));
        const memcmp_bb = c.LLVMAppendBasicBlockInContext(self.context, cur_fn, "str.memcmp");
        const merge_bb = c.LLVMAppendBasicBlockInContext(self.context, cur_fn, "str.merge");

        const cur_bb = c.LLVMGetInsertBlock(b);
        _ = c.LLVMBuildCondBr(b, len_eq, memcmp_bb, merge_bb);

        // memcmp block
        c.LLVMPositionBuilderAtEnd(b, memcmp_bb);
        const size_ty = self.sizeType();
        const memcmp_fn = c.LLVMGetNamedFunction(self.llvm_module, "memcmp") orelse blk: {
            var params = [_]c.LLVMTypeRef{ ptr_ty, ptr_ty, size_ty };
            const fn_type = c.LLVMFunctionType(i32_ty, &params, 3, 0);
            break :blk c.LLVMAddFunction(self.llvm_module, "memcmp", fn_type);
        };
        const cmp_len = self.coerceArg(lhs_len, size_ty);
        var args = [_]c.LLVMValueRef{ lhs_ptr, rhs_ptr, cmp_len };
        const fn_ty = c.LLVMGlobalGetValueType(memcmp_fn);
        const cmp_result = c.LLVMBuildCall2(b, fn_ty, memcmp_fn, &args, 3, "memcmp");
        const content_eq = c.LLVMBuildICmp(b, c.LLVMIntEQ, cmp_result, c.LLVMConstInt(i32_ty, 0, 0), "str.ceq");
        _ = c.LLVMBuildBr(b, merge_bb);

        // Merge block: phi(len_mismatch=false, memcmp_result)
        c.LLVMPositionBuilderAtEnd(b, merge_bb);
        const phi = c.LLVMBuildPhi(b, i1_ty, "str.eq");
        const false_val = c.LLVMConstInt(i1_ty, 0, 0);
        var phi_vals = [_]c.LLVMValueRef{ false_val, content_eq };
        var phi_bbs = [_]c.LLVMBasicBlockRef{ cur_bb, memcmp_bb };
        c.LLVMAddIncoming(phi, &phi_vals, &phi_bbs, 2);

        const result = if (is_eq)
            phi
        else
            c.LLVMBuildNot(b, phi, "str.ne");
        self.mapRef(result);
    }

    // ── Conversion helpers ──────────────────────────────────────────

    fn emitConversion(self: *LLVMEmitter, operand: c.LLVMValueRef, from: TypeId, to: TypeId, to_ty: c.LLVMTypeRef) c.LLVMValueRef {
        const from_float = isFloatOrVecFloat(from, &self.ir_mod.types);
        const to_float = isFloatOrVecFloat(to, &self.ir_mod.types);

        if (from_float and to_float) {
            // float→float: FPExt or FPTrunc
            const from_bits = floatBits(from);
            const to_bits = floatBits(to);
            return if (to_bits > from_bits)
                c.LLVMBuildFPExt(self.builder, operand, to_ty, "fpext")
            else
                c.LLVMBuildFPTrunc(self.builder, operand, to_ty, "fptrunc");
        }

        if (from_float and !to_float) {
            return if (isSignedType(to))
                c.LLVMBuildFPToSI(self.builder, operand, to_ty, "fptosi")
            else
                c.LLVMBuildFPToUI(self.builder, operand, to_ty, "fptoui");
        }

        if (!from_float and to_float) {
            return if (isSignedType(from))
                c.LLVMBuildSIToFP(self.builder, operand, to_ty, "sitofp")
            else
                c.LLVMBuildUIToFP(self.builder, operand, to_ty, "uitofp");
        }

        // int→int: SExt, ZExt, or Trunc
        const ptr_bits: u32 = @as(u32, self.ir_mod.types.pointer_size) * 8;
        const from_bits = if (intBits(from) == 0) ptr_bits else intBits(from);
        const to_bits = if (intBits(to) == 0) ptr_bits else intBits(to);
        if (to_bits > from_bits) {
            return if (isSignedType(from))
                c.LLVMBuildSExt(self.builder, operand, to_ty, "sext")
            else
                c.LLVMBuildZExt(self.builder, operand, to_ty, "zext");
        } else if (to_bits < from_bits) {
            return c.LLVMBuildTrunc(self.builder, operand, to_ty, "trunc");
        }
        // Same width — no-op (bitcast or just return)
        return operand;
    }

    // ── Malloc/Free declarations ────────────────────────────────────

    fn getOrDeclareMalloc(self: *LLVMEmitter) c.LLVMValueRef {
        if (c.LLVMGetNamedFunction(self.llvm_module, "malloc")) |f| return f;
        const fn_ty = self.getMallocType();
        return c.LLVMAddFunction(self.llvm_module, "malloc", fn_ty);
    }

    fn getOrDeclareFree(self: *LLVMEmitter) c.LLVMValueRef {
        if (c.LLVMGetNamedFunction(self.llvm_module, "free")) |f| return f;
        const fn_ty = self.getFreeType();
        return c.LLVMAddFunction(self.llvm_module, "free", fn_ty);
    }

    /// Returns the LLVM type for C `size_t`: i32 on wasm32, i64 on 64-bit targets (including wasm64).
    fn sizeType(self: *LLVMEmitter) c.LLVMTypeRef {
        return if (self.target_config.isWasm32()) self.cached_i32 else self.cached_i64;
    }

    fn getMallocType(self: *LLVMEmitter) c.LLVMTypeRef {
        // malloc(size_t) → ptr
        var param_types = [_]c.LLVMTypeRef{self.sizeType()};
        return c.LLVMFunctionType(self.cached_ptr, &param_types, 1, 0);
    }

    fn getFreeType(self: *LLVMEmitter) c.LLVMTypeRef {
        // free(ptr) → void
        var param_types = [_]c.LLVMTypeRef{self.cached_ptr};
        return c.LLVMFunctionType(self.cached_void, &param_types, 1, 0);
    }

    fn getOrDeclareMemcpy(self: *LLVMEmitter) c.LLVMValueRef {
        if (c.LLVMGetNamedFunction(self.llvm_module, "memcpy")) |f| return f;
        return c.LLVMAddFunction(self.llvm_module, "memcpy", self.getMemcpyType());
    }

    fn getMemcpyType(self: *LLVMEmitter) c.LLVMTypeRef {
        // memcpy(ptr, ptr, size_t) → ptr
        var param_types = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr, self.sizeType() };
        return c.LLVMFunctionType(self.cached_ptr, &param_types, 3, 0);
    }

    fn getOrDeclareMemset(self: *LLVMEmitter) c.LLVMValueRef {
        if (c.LLVMGetNamedFunction(self.llvm_module, "memset")) |f| return f;
        return c.LLVMAddFunction(self.llvm_module, "memset", self.getMemsetType());
    }

    fn getMemsetType(self: *LLVMEmitter) c.LLVMTypeRef {
        // memset(ptr, i32, size_t) → ptr
        var param_types = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_i32, self.sizeType() };
        return c.LLVMFunctionType(self.cached_ptr, &param_types, 3, 0);
    }

    fn getOrDeclareMathF64(self: *LLVMEmitter, id: ir_inst.BuiltinId) c.LLVMValueRef {
        const name: [*:0]const u8 = switch (id) {
            .sqrt => "sqrt",
            .sin => "sin",
            .cos => "cos",
            .floor => "floor",
            else => unreachable,
        };
        if (c.LLVMGetNamedFunction(self.llvm_module, name)) |f| return f;
        return c.LLVMAddFunction(self.llvm_module, name, self.getMathF64Type());
    }

    fn getMathF64Type(self: *LLVMEmitter) c.LLVMTypeRef {
        var param_types = [_]c.LLVMTypeRef{self.cached_f64};
        return c.LLVMFunctionType(self.cached_f64, &param_types, 1, 0);
    }

    fn getOrDeclareMathF32(self: *LLVMEmitter, id: ir_inst.BuiltinId) c.LLVMValueRef {
        const name: [*:0]const u8 = switch (id) {
            .sqrt => "sqrtf",
            .sin => "sinf",
            .cos => "cosf",
            .floor => "floorf",
            else => unreachable,
        };
        if (c.LLVMGetNamedFunction(self.llvm_module, name)) |f| return f;
        return c.LLVMAddFunction(self.llvm_module, name, self.getMathF32Type());
    }

    fn getMathF32Type(self: *LLVMEmitter) c.LLVMTypeRef {
        var param_types = [_]c.LLVMTypeRef{self.cached_f32};
        return c.LLVMFunctionType(self.cached_f32, &param_types, 1, 0);
    }

    fn getOrDeclareMemcmp(self: *LLVMEmitter) c.LLVMValueRef {
        if (c.LLVMGetNamedFunction(self.llvm_module, "memcmp")) |f| return f;
        // memcmp(ptr, ptr, size_t) → i32
        var param_types = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr, self.sizeType() };
        const fn_ty = c.LLVMFunctionType(self.cached_i32, &param_types, 3, 0);
        return c.LLVMAddFunction(self.llvm_module, "memcmp", fn_ty);
    }

    fn getOrDeclareWrite(self: *LLVMEmitter) c.LLVMValueRef {
        if (c.LLVMGetNamedFunction(self.llvm_module, "write")) |f| return f;
        return c.LLVMAddFunction(self.llvm_module, "write", self.getWriteType());
    }

    fn getWriteType(self: *LLVMEmitter) c.LLVMTypeRef {
        // write(fd: i32, buf: ptr, count: size_t) → ssize_t
        const st = self.sizeType();
        var param_types = [_]c.LLVMTypeRef{ self.cached_i32, self.cached_ptr, st };
        return c.LLVMFunctionType(st, &param_types, 3, 0);
    }

    fn getOrDeclareSnprintf(self: *LLVMEmitter) c.LLVMValueRef {
        if (c.LLVMGetNamedFunction(self.llvm_module, "snprintf")) |f| return f;
        return c.LLVMAddFunction(self.llvm_module, "snprintf", self.getSnprintfType());
    }

    fn getSnprintfType(self: *LLVMEmitter) c.LLVMTypeRef {
        // snprintf(buf: ptr, size: i32, fmt: ptr, ...) → i32  (variadic)
        var param_types = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_i32, self.cached_ptr };
        return c.LLVMFunctionType(self.cached_i32, &param_types, 3, 1); // 1 = variadic
    }

    /// Check if a function name is a known libc builtin that has a dedicated
    /// getOrDeclare* helper with correct C-compatible types.
    fn isBuiltinLibcName(name: []const u8) bool {
        const builtins = [_][]const u8{ "malloc", "free", "memcpy", "memset", "memcmp", "write", "snprintf" };
        for (builtins) |b| {
            if (std.mem.eql(u8, name, b)) return true;
        }
        return false;
    }

    /// Get or declare a builtin libc function by name, using the correct C-compatible type.
    fn getOrDeclareBuiltinByName(self: *LLVMEmitter, name: []const u8) ?c.LLVMValueRef {
        if (std.mem.eql(u8, name, "malloc")) return self.getOrDeclareMalloc();
        if (std.mem.eql(u8, name, "free")) return self.getOrDeclareFree();
        if (std.mem.eql(u8, name, "memcpy")) return self.getOrDeclareMemcpy();
        if (std.mem.eql(u8, name, "memset")) return self.getOrDeclareMemset();
        if (std.mem.eql(u8, name, "memcmp")) return self.getOrDeclareMemcmp();
        if (std.mem.eql(u8, name, "write")) return self.getOrDeclareWrite();
        if (std.mem.eql(u8, name, "snprintf")) return self.getOrDeclareSnprintf();
        return null;
    }

    /// Build a string fat pointer {ptr, len} from raw pointer and length.
    fn buildStringValue(self: *LLVMEmitter, ptr: c.LLVMValueRef, len: c.LLVMValueRef) c.LLVMValueRef {
        const str_ty = self.getStringStructType();
        const undef = c.LLVMGetUndef(str_ty);
        const with_ptr = c.LLVMBuildInsertValue(self.builder, undef, ptr, 0, "s.ptr");
        return c.LLVMBuildInsertValue(self.builder, with_ptr, len, 1, "s.len");
    }

    // ── Value coercion helpers ──────────────────────────────────────

    /// Coerce any scalar value to i64 for boxing into Any.
    fn coerceToI64(self: *LLVMEmitter, val: c.LLVMValueRef) c.LLVMValueRef {
        const ty = c.LLVMTypeOf(val);
        const kind = c.LLVMGetTypeKind(ty);
        if (kind == c.LLVMVoidTypeKind) {
            return c.LLVMConstInt(self.cached_i64, 0, 0);
        }
        if (kind == c.LLVMPointerTypeKind) {
            return c.LLVMBuildPtrToInt(self.builder, val, self.cached_i64, "p2i");
        }
        if (kind == c.LLVMFloatTypeKind) {
            // f32 → bitcast to i32 → zext to i64
            const as_i32 = c.LLVMBuildBitCast(self.builder, val, self.cached_i32, "f2i32");
            return c.LLVMBuildZExt(self.builder, as_i32, self.cached_i64, "z64");
        }
        if (kind == c.LLVMDoubleTypeKind) {
            return c.LLVMBuildBitCast(self.builder, val, self.cached_i64, "d2i");
        }
        if (kind == c.LLVMIntegerTypeKind) {
            const width = c.LLVMGetIntTypeWidth(ty);
            if (width < 64) {
                return c.LLVMBuildZExt(self.builder, val, self.cached_i64, "z64");
            }
            return val; // already i64
        }
        // Struct/Array/Vector types: store to alloca, ptrtoint for the pointer
        if (kind == c.LLVMStructTypeKind or kind == c.LLVMArrayTypeKind or kind == c.LLVMVectorTypeKind or kind == c.LLVMScalableVectorTypeKind) {
            const tmp = c.LLVMBuildAlloca(self.builder, ty, "ba.tmp");
            _ = c.LLVMBuildStore(self.builder, val, tmp);
            return c.LLVMBuildPtrToInt(self.builder, tmp, self.cached_i64, "ba.p2i");
        }
        return val;
    }

    /// Coerce signed integer to i64 using sign-extension.
    fn coerceToI64Signed(self: *LLVMEmitter, val: c.LLVMValueRef) c.LLVMValueRef {
        const ty = c.LLVMTypeOf(val);
        const kind = c.LLVMGetTypeKind(ty);
        if (kind == c.LLVMIntegerTypeKind) {
            const width = c.LLVMGetIntTypeWidth(ty);
            if (width < 64) {
                return c.LLVMBuildSExt(self.builder, val, self.cached_i64, "s64");
            }
            return val;
        }
        // Fallback for non-integer types
        return self.coerceToI64(val);
    }

    /// Check if a TypeId represents a signed integer type (including arbitrary-width).
    fn isSignedTypeEx(self: *LLVMEmitter, ty: TypeId) bool {
        if (isSignedType(ty)) return true;
        if (!ty.isBuiltin()) {
            const info = self.ir_mod.types.get(ty);
            return info == .signed;
        }
        return false;
    }

    /// Map a TypeId to its Any tag value.
    /// Uses TypeId.index() directly — this matches resolveTypeCategoryTags in lower.zig
    /// which also uses TypeId indices for type-switch comparisons.
    /// For arbitrary-width ints (user-defined signed/unsigned), map to the closest
    /// builtin TypeId so the "case int:" branch matches correctly.
    /// Map a TypeId to its Any tag value.
    /// Uses TypeId.index() directly — this matches resolveTypeCategoryTags in lower.zig
    /// which also uses TypeId indices for type-switch comparisons.
    /// For arbitrary-width ints (user-defined signed/unsigned), map to the closest
    /// builtin TypeId so the "case int:" branch matches correctly.
    fn anyTag(self: *LLVMEmitter, ty: TypeId) u64 {
        if (ty.isBuiltin()) return ty.index();
        // For user-defined types, check if they're arbitrary-width ints
        const info = self.ir_mod.types.get(ty);
        return switch (info) {
            .signed => |w| switch (w) {
                8 => TypeId.s8.index(),
                16 => TypeId.s16.index(),
                32 => TypeId.s32.index(),
                64 => TypeId.s64.index(),
                else => if (w <= 32) TypeId.s32.index() else TypeId.s64.index(),
            },
            .unsigned => |w| switch (w) {
                8 => TypeId.u8.index(),
                16 => TypeId.u16.index(),
                32 => TypeId.u32.index(),
                64 => TypeId.u64.index(),
                else => if (w <= 32) TypeId.u32.index() else TypeId.u64.index(),
            },
            else => ty.index(),
        };
    }

    /// Coerce i64 back to the target type for unboxing from Any.
    fn coerceFromI64(self: *LLVMEmitter, val: c.LLVMValueRef, target: c.LLVMTypeRef) c.LLVMValueRef {
        const kind = c.LLVMGetTypeKind(target);
        if (kind == c.LLVMPointerTypeKind) {
            return c.LLVMBuildIntToPtr(self.builder, val, target, "i2p");
        }
        if (kind == c.LLVMFloatTypeKind) {
            const as_i32 = c.LLVMBuildTrunc(self.builder, val, self.cached_i32, "tr32");
            return c.LLVMBuildBitCast(self.builder, as_i32, target, "i2f");
        }
        if (kind == c.LLVMDoubleTypeKind) {
            return c.LLVMBuildBitCast(self.builder, val, target, "i2d");
        }
        if (kind == c.LLVMIntegerTypeKind) {
            const width = c.LLVMGetIntTypeWidth(target);
            if (width < 64) {
                return c.LLVMBuildTrunc(self.builder, val, target, "tr");
            }
        }
        // Struct/Array/Vector types: interpret i64 as pointer, load the value
        if (kind == c.LLVMStructTypeKind or kind == c.LLVMArrayTypeKind or kind == c.LLVMVectorTypeKind or kind == c.LLVMScalableVectorTypeKind) {
            const ptr = c.LLVMBuildIntToPtr(self.builder, val, self.cached_ptr, "ua.ptr");
            return c.LLVMBuildLoad2(self.builder, target, ptr, "ua.load");
        }
        return val;
    }

    /// Coerce a call argument to match the expected parameter type.
    /// Handles int width mismatches (trunc/ext), float width, and int↔float.
    fn coerceArg(self: *LLVMEmitter, val: c.LLVMValueRef, param_ty: c.LLVMTypeRef) c.LLVMValueRef {
        const val_ty = c.LLVMTypeOf(val);
        if (val_ty == param_ty) return val;
        const val_kind = c.LLVMGetTypeKind(val_ty);
        const param_kind = c.LLVMGetTypeKind(param_ty);

        // Int → Int (width mismatch)
        if (val_kind == c.LLVMIntegerTypeKind and param_kind == c.LLVMIntegerTypeKind) {
            const val_w = c.LLVMGetIntTypeWidth(val_ty);
            const param_w = c.LLVMGetIntTypeWidth(param_ty);
            if (val_w > param_w) {
                return c.LLVMBuildTrunc(self.builder, val, param_ty, "ca.tr");
            } else {
                // Use ZExt by default — preserves bit pattern for unsigned types.
                // Signed widening is handled by explicit widen instructions from the IR.
                return c.LLVMBuildZExt(self.builder, val, param_ty, "ca.ext");
            }
        }
        // Float → Float (width mismatch)
        if ((val_kind == c.LLVMFloatTypeKind or val_kind == c.LLVMDoubleTypeKind) and
            (param_kind == c.LLVMFloatTypeKind or param_kind == c.LLVMDoubleTypeKind))
        {
            if (val_kind == c.LLVMFloatTypeKind and param_kind == c.LLVMDoubleTypeKind) {
                return c.LLVMBuildFPExt(self.builder, val, param_ty, "ca.fpext");
            } else {
                return c.LLVMBuildFPTrunc(self.builder, val, param_ty, "ca.fptrunc");
            }
        }
        // Int → Float (use SIToFP for i1/bool, UIToFP otherwise for safe default)
        if (val_kind == c.LLVMIntegerTypeKind and (param_kind == c.LLVMFloatTypeKind or param_kind == c.LLVMDoubleTypeKind)) {
            const val_w = c.LLVMGetIntTypeWidth(val_ty);
            if (val_w == 1) {
                return c.LLVMBuildUIToFP(self.builder, val, param_ty, "ca.uitofp");
            }
            // Default to SIToFP since most sx integers are signed (s64).
            // Explicit unsigned conversions go through the IR widen/narrow path.
            return c.LLVMBuildSIToFP(self.builder, val, param_ty, "ca.sitofp");
        }
        // Float → Int
        if ((val_kind == c.LLVMFloatTypeKind or val_kind == c.LLVMDoubleTypeKind) and param_kind == c.LLVMIntegerTypeKind) {
            return c.LLVMBuildFPToSI(self.builder, val, param_ty, "ca.fptosi");
        }
        // Ptr → Struct (closure auto-promotion: fn_ptr → {fn_ptr, null_env})
        if (val_kind == c.LLVMPointerTypeKind and param_kind == c.LLVMStructTypeKind) {
            const num_fields = c.LLVMCountStructElementTypes(param_ty);
            if (num_fields == 2) {
                const f0 = c.LLVMStructGetTypeAtIndex(param_ty, 0);
                const f1 = c.LLVMStructGetTypeAtIndex(param_ty, 1);
                if (c.LLVMGetTypeKind(f0) == c.LLVMPointerTypeKind and c.LLVMGetTypeKind(f1) == c.LLVMPointerTypeKind) {
                    var result = c.LLVMGetUndef(param_ty);
                    result = c.LLVMBuildInsertValue(self.builder, result, val, 0, "ca.cls.fn");
                    result = c.LLVMBuildInsertValue(self.builder, result, c.LLVMConstNull(f1), 1, "ca.cls.env");
                    return result;
                }
            }
        }
        // Scalar → Vector (splat: broadcast scalar to all lanes)
        if (param_kind == c.LLVMVectorTypeKind or param_kind == c.LLVMScalableVectorTypeKind) {
            const vec_elem_ty = c.LLVMGetElementType(param_ty);
            const vec_len = c.LLVMGetVectorSize(param_ty);
            // First coerce scalar to the vector element type
            const scalar = self.coerceArg(val, vec_elem_ty);
            // Then splat into a vector
            var result = c.LLVMGetUndef(param_ty);
            var lane: c_uint = 0;
            while (lane < vec_len) : (lane += 1) {
                const idx = c.LLVMConstInt(self.cached_i32, lane, 0);
                result = c.LLVMBuildInsertElement(self.builder, result, scalar, idx, "splat");
            }
            return result;
        }
        // Struct → Ptr (string/slice decay: extract field 0 = raw pointer)
        // Only for 2-field structs {ptr, i64} (fat pointers) — avoids breaking other struct→ptr cases
        if (val_kind == c.LLVMStructTypeKind and param_kind == c.LLVMPointerTypeKind) {
            const num_fields = c.LLVMCountStructElementTypes(val_ty);
            if (num_fields == 2) {
                const field0_ty = c.LLVMStructGetTypeAtIndex(val_ty, 0);
                if (c.LLVMGetTypeKind(field0_ty) == c.LLVMPointerTypeKind) {
                    return c.LLVMBuildExtractValue(self.builder, val, 0, "ca.decay");
                }
            }
        }
        // Struct → Integer (C ABI coercion: store struct to memory, load as integer)
        if (val_kind == c.LLVMStructTypeKind and param_kind == c.LLVMIntegerTypeKind) {
            const tmp = c.LLVMBuildAlloca(self.builder, param_ty, "abi.tmp");
            _ = c.LLVMBuildStore(self.builder, c.LLVMConstNull(param_ty), tmp);
            _ = c.LLVMBuildStore(self.builder, val, tmp);
            return c.LLVMBuildLoad2(self.builder, param_ty, tmp, "abi.coerce");
        }
        // Integer → Struct (C ABI return coercion: store integer to memory, load as struct)
        if (val_kind == c.LLVMIntegerTypeKind and param_kind == c.LLVMStructTypeKind) {
            const tmp = c.LLVMBuildAlloca(self.builder, val_ty, "abi.ret.tmp");
            _ = c.LLVMBuildStore(self.builder, val, tmp);
            return c.LLVMBuildLoad2(self.builder, param_ty, tmp, "abi.ret.coerce");
        }
        // Struct → Array (C ABI coercion for 9..16-byte structs — paired with
        // abiCoerceParamType's `[2 x i64]` slot for that size class). Same
        // memory-bitcast pattern as the integer case; the array type carries
        // 16 bytes of storage so we alloca with param_ty to guarantee size.
        if (val_kind == c.LLVMStructTypeKind and param_kind == c.LLVMArrayTypeKind) {
            const tmp = c.LLVMBuildAlloca(self.builder, param_ty, "abi.struct2arr");
            _ = c.LLVMBuildStore(self.builder, val, tmp);
            return c.LLVMBuildLoad2(self.builder, param_ty, tmp, "abi.coerce.arr");
        }
        // Array → Struct (return-side counterpart for 9..16-byte structs)
        if (val_kind == c.LLVMArrayTypeKind and param_kind == c.LLVMStructTypeKind) {
            const tmp = c.LLVMBuildAlloca(self.builder, val_ty, "abi.arr2struct");
            _ = c.LLVMBuildStore(self.builder, val, tmp);
            return c.LLVMBuildLoad2(self.builder, param_ty, tmp, "abi.ret.coerce.arr");
        }
        // Array → Ptr (array decay: alloca + GEP to first element)
        if (val_kind == c.LLVMArrayTypeKind and param_kind == c.LLVMPointerTypeKind) {
            const tmp = c.LLVMBuildAlloca(self.builder, val_ty, "ca.arr");
            _ = c.LLVMBuildStore(self.builder, val, tmp);
            const zero = c.LLVMConstInt(self.cached_i64, 0, 0);
            var indices = [_]c.LLVMValueRef{ zero, zero };
            return c.LLVMBuildGEP2(self.builder, val_ty, tmp, &indices, 2, "ca.decay");
        }
        // Int → Ptr (null literal: inttoptr)
        if (val_kind == c.LLVMIntegerTypeKind and param_kind == c.LLVMPointerTypeKind) {
            return c.LLVMBuildIntToPtr(self.builder, val, param_ty, "ca.itp");
        }
        return val;
    }

    /// Look up the IR type of a Ref in the current function (for store coercion).
    fn getRefIRType(self: *LLVMEmitter, ref: Ref) ?TypeId {
        const func = &self.ir_mod.functions.items[self.current_func_idx];
        const idx = ref.index();
        // Check if it's a function param (refs 0..N-1)
        if (idx < func.params.len) return func.params[idx].ty;
        for (func.blocks.items) |blk| {
            if (idx >= blk.first_ref and idx < blk.first_ref + blk.insts.items.len) {
                return blk.insts.items[idx - blk.first_ref].ty;
            }
        }
        return null;
    }


    /// Coerce both binary operands to match the instruction's result type.
    /// E.g. if result is i64 but one operand is i32, sext it.
    fn matchBinOpTypes(self: *LLVMEmitter, lhs: *c.LLVMValueRef, rhs: *c.LLVMValueRef, result_ty: TypeId) void {
        const target = self.toLLVMType(result_ty);
        lhs.* = self.coerceArg(lhs.*, target);
        rhs.* = self.coerceArg(rhs.*, target);
    }

    // ── Type conversion ─────────────────────────────────────────────

    pub fn toLLVMType(self: *LLVMEmitter, ty: TypeId) c.LLVMTypeRef {
        return switch (ty) {
            .void => self.cached_void,
            .bool => self.cached_i1,
            .s8 => self.cached_i8,
            .s16 => self.cached_i16,
            .s32 => self.cached_i32,
            .s64 => self.cached_i64,
            .u8 => self.cached_i8,
            .u16 => self.cached_i16,
            .u32 => self.cached_i32,
            .u64 => self.cached_i64,
            .f32 => self.cached_f32,
            .f64 => self.cached_f64,
            .string => self.getStringStructType(),
            .any => self.getAnyStructType(),
            .noreturn => self.cached_void,
            .isize, .usize => if (self.target_config.isWasm32()) self.cached_i32 else self.cached_i64,
            else => self.toLLVMTypeInfo(ty),
        };
    }

    fn toLLVMTypeInfo(self: *LLVMEmitter, ty: TypeId) c.LLVMTypeRef {
        const info = self.ir_mod.types.get(ty);
        return switch (info) {
            .signed => |w| switch (w) {
                1 => self.cached_i1,
                8 => self.cached_i8,
                16 => self.cached_i16,
                32 => self.cached_i32,
                64 => self.cached_i64,
                else => c.LLVMIntTypeInContext(self.context, w),
            },
            .unsigned => |w| switch (w) {
                1 => self.cached_i1,
                8 => self.cached_i8,
                16 => self.cached_i16,
                32 => self.cached_i32,
                64 => self.cached_i64,
                else => c.LLVMIntTypeInContext(self.context, w),
            },
            .f32 => self.cached_f32,
            .f64 => self.cached_f64,
            .void => self.cached_void,
            .bool => self.cached_i1,
            .error_set => self.cached_i32, // u32 tag id on the error channel
            .string => self.getStringStructType(),
            .pointer, .many_pointer, .function => self.cached_ptr,
            .closure => self.getClosureStructType(),
            .slice => self.getStringStructType(), // same {ptr, i64} layout
            .optional => |opt| {
                // ?*T / ?fn → bare pointer (null = none)
                const child_info = self.ir_mod.types.get(opt.child);
                if (child_info == .pointer or child_info == .many_pointer or child_info == .function) {
                    return self.cached_ptr;
                }
                if (child_info == .closure) {
                    return self.getClosureStructType();
                }
                // ?Protocol → protocol struct (ctx ptr = field 0 is null when none).
                if (child_info == .@"struct" and child_info.@"struct".is_protocol) {
                    return self.toLLVMType(opt.child);
                }
                // ?T → { T, i1 }
                var field_types: [2]c.LLVMTypeRef = .{
                    self.toLLVMType(opt.child),
                    self.cached_i1,
                };
                return c.LLVMStructTypeInContext(self.context, &field_types, 2, 0);
            },
            .array => |arr| {
                const elem = self.toLLVMType(arr.element);
                return c.LLVMArrayType2(elem, arr.length);
            },
            .vector => |vec| {
                const elem = self.toLLVMType(vec.element);
                return c.LLVMVectorType(elem, vec.length);
            },
            .any => self.getAnyStructType(),
            .noreturn => self.cached_void,
            .@"struct" => |s| {
                // Build LLVM struct type from fields
                const n: c_uint = @intCast(s.fields.len);
                const field_llvm_types = self.alloc.alloc(c.LLVMTypeRef, s.fields.len) catch unreachable;
                defer self.alloc.free(field_llvm_types);
                for (s.fields, 0..) |field, j| {
                    field_llvm_types[j] = self.toLLVMType(field.ty);
                }
                return c.LLVMStructTypeInContext(self.context, field_llvm_types.ptr, n, 0);
            },
            .@"enum" => |e| {
                // Use backing type if declared (e.g. enum u32 → i32), else i64
                if (e.backing_type) |bt| return self.toLLVMType(bt);
                return self.cached_i64;
            },
            .@"union" => |u| {
                // Untagged union — just [N x i8]
                var max_size: usize = 0;
                for (u.fields) |field| {
                    const sz = self.ir_mod.types.typeSizeBytes(field.ty);
                    if (sz > max_size) max_size = sz;
                }
                if (max_size == 0) max_size = 8;
                return c.LLVMArrayType2(self.cached_i8, @intCast(max_size));
            },
            .tagged_union => |u| {
                // Tagged union — { header, [N x i8] }
                var max_size: usize = 0;
                for (u.fields) |field| {
                    const sz = self.ir_mod.types.typeSizeBytes(field.ty);
                    if (sz > max_size) max_size = sz;
                }
                if (max_size == 0) max_size = 8;

                var header_size: usize = self.ir_mod.types.typeSizeBytes(u.tag_type);
                if (u.backing_type) |bt| {
                    const bi = self.ir_mod.types.get(bt);
                    if (bi == .@"struct" and bi.@"struct".fields.len > 1) {
                        header_size = 0;
                        const fields = bi.@"struct".fields;
                        for (fields[0 .. fields.len - 1]) |f| {
                            header_size += self.ir_mod.types.typeSizeBytes(f.ty);
                        }
                        const backing_payload = self.ir_mod.types.typeSizeBytes(fields[fields.len - 1].ty);
                        if (backing_payload > max_size) max_size = backing_payload;
                    }
                }

                const header_llvm = c.LLVMIntTypeInContext(self.context, @intCast(header_size * 8));
                var field_types: [2]c.LLVMTypeRef = .{
                    header_llvm,
                    c.LLVMArrayType2(self.cached_i8, @intCast(max_size)),
                };
                return c.LLVMStructTypeInContext(self.context, &field_types, 2, 0);
            },
            .tuple => |t| {
                const n: c_uint = @intCast(t.fields.len);
                const field_llvm_types = self.alloc.alloc(c.LLVMTypeRef, t.fields.len) catch unreachable;
                defer self.alloc.free(field_llvm_types);
                for (t.fields, 0..) |f, j| {
                    field_llvm_types[j] = self.toLLVMType(f);
                }
                return c.LLVMStructTypeInContext(self.context, field_llvm_types.ptr, n, 0);
            },
            .protocol => {
                // Protocol values: { ctx: *void, vtable_or_fn_ptrs... }
                // For now, use opaque ptr
                return self.cached_ptr;
            },
            .usize, .isize => if (self.target_config.isWasm32()) self.cached_i32 else self.cached_i64,
            // Comptime-only: a pack is expanded to flat positional args before
            // codegen, so it must never reach LLVM type emission.
            .pack => @panic("pack type has no LLVM representation (comptime-only)"),
            // Tripwire: a failed type resolution must have been diagnosed and
            // aborted long before LLVM emission.
            .unresolved => @panic("unresolved type reached LLVM emission — a type resolution failure was not diagnosed/aborted"),
        };
    }

    // ── C ABI coercion for foreign functions ──────────────────────────
    //
    // On ARM64 (and x86_64), the C calling convention coerces small struct
    // arguments to integers for register passing:
    //   - String/slice {ptr, i64} → ptr (extract raw pointer)
    //   - Small integer struct (≤ 8 bytes, non-HFA) → i64
    //   - HFA (homogeneous float aggregate) → leave as-is (LLVM handles it)

    fn abiCoerceParamType(self: *LLVMEmitter, ir_ty: TypeId, llvm_ty: c.LLVMTypeRef) c.LLVMTypeRef {
        return self.abiCoerceParamTypeEx(ir_ty, llvm_ty, true);
    }

    /// Same as `abiCoerceParamType` but with an explicit
    /// `is_foreign_c_api` knob. When true, sx `string` / `[]T` slices
    /// collapse to `ptr` — the libc convention where the user writes
    /// `string` to mean `char *` and the length is dropped. When
    /// false (sx-internal `callconv(.c)` like block trampolines), the
    /// full slice shape is preserved and goes through the general
    /// struct-coerce path (16-byte slice → `[2 x i64]`, lands in two
    /// registers on AArch64 — the true C ABI for a 16-byte
    /// aggregate). Without the split, sx-to-sx calls through a
    /// `(*Block, string) -> void callconv(.c)` fn-pointer mismatched
    /// the caller's `{ptr, i64}` value against the trampoline's
    /// collapsed `ptr` param.
    fn abiCoerceParamTypeEx(self: *LLVMEmitter, ir_ty: TypeId, llvm_ty: c.LLVMTypeRef, is_foreign_c_api: bool) c.LLVMTypeRef {
        if (is_foreign_c_api) {
            if (ir_ty == .string) return self.cached_ptr;
            if (!ir_ty.isBuiltin()) {
                const info = self.ir_mod.types.get(ir_ty);
                if (info == .slice) return self.cached_ptr;
            }
        }

        // WASM32: usize/isize are pointer-sized (i32 on wasm32).
        // Other integer types (s64, u64) keep their declared size — they represent
        // genuinely 64-bit values (SDL_WindowFlags, timestamps, etc.).
        if (self.target_config.isWasm32()) {
            if (ir_ty == .usize or ir_ty == .isize) return self.cached_i32;
            return llvm_ty;
        }

        // Only coerce struct types
        if (c.LLVMGetTypeKind(llvm_ty) != c.LLVMStructTypeKind) return llvm_ty;

        // Check if it's an HFA (all float or all double fields) — leave as-is
        const n_fields = c.LLVMCountStructElementTypes(llvm_ty);
        if (n_fields >= 1 and n_fields <= 4) {
            var all_float = true;
            var all_double = true;
            var fi: c_uint = 0;
            while (fi < n_fields) : (fi += 1) {
                const ft = c.LLVMStructGetTypeAtIndex(llvm_ty, fi);
                const fk = c.LLVMGetTypeKind(ft);
                if (fk != c.LLVMFloatTypeKind) all_float = false;
                if (fk != c.LLVMDoubleTypeKind) all_double = false;
            }
            if (all_float or all_double) return llvm_ty;
        }

        // Small struct (≤ 8 bytes) → coerce to i64
        const size = c.LLVMABISizeOfType(
            c.LLVMGetModuleDataLayout(self.llvm_module),
            llvm_ty,
        );
        if (size <= 8) return self.cached_i64;

        // Medium struct (9-16 bytes) → coerce to [2 x i64]
        if (size <= 16) {
            return c.LLVMArrayType2(self.cached_i64, 2);
        }

        // Large composite (> 16 bytes) → pass by reference: ptr + byval(<T>) at
        // the call/sig sites. LLVM's AArch64/x86_64 backend lowers byval to
        // the right ABI sequence (caller copy + indirect arg).
        return self.cached_ptr;
    }

    fn needsByval(self: *LLVMEmitter, ir_ty: TypeId, raw_llvm_ty: c.LLVMTypeRef) bool {
        if (self.target_config.isWasm32()) return false;
        if (ir_ty == .string) return false;
        if (!ir_ty.isBuiltin()) {
            const info = self.ir_mod.types.get(ir_ty);
            if (info == .slice) return false;
        }
        if (c.LLVMGetTypeKind(raw_llvm_ty) != c.LLVMStructTypeKind) return false;
        const n = c.LLVMCountStructElementTypes(raw_llvm_ty);
        if (n >= 1 and n <= 4) {
            var all_f = true;
            var all_d = true;
            var i: c_uint = 0;
            while (i < n) : (i += 1) {
                const ft = c.LLVMStructGetTypeAtIndex(raw_llvm_ty, i);
                const fk = c.LLVMGetTypeKind(ft);
                if (fk != c.LLVMFloatTypeKind) all_f = false;
                if (fk != c.LLVMDoubleTypeKind) all_d = false;
            }
            if (all_f or all_d) return false;
        }
        const size = c.LLVMABISizeOfType(c.LLVMGetModuleDataLayout(self.llvm_module), raw_llvm_ty);
        return size > 16;
    }

    fn materializeByvalArg(self: *LLVMEmitter, val: c.LLVMValueRef, struct_ty: c.LLVMTypeRef) c.LLVMValueRef {
        const tmp = c.LLVMBuildAlloca(self.builder, struct_ty, "byval.tmp");
        _ = c.LLVMBuildStore(self.builder, val, tmp);
        return tmp;
    }

    // ── Cached composite types ──────────────────────────────────────

    fn getStringStructType(self: *LLVMEmitter) c.LLVMTypeRef {
        if (self.string_struct_type) |t| return t;
        var field_types = [_]c.LLVMTypeRef{
            self.cached_ptr, // ptr
            self.cached_i64, // len
        };
        self.string_struct_type = c.LLVMStructTypeInContext(self.context, &field_types, 2, 0);
        return self.string_struct_type.?;
    }

    /// The compiled error-trace `Frame` type: `{ string, i32, i32, string }`.
    /// Layout must match `Frame` in `trace.sx` and `SxFrame` in `sx_trace.c`.
    fn getFrameStructType(self: *LLVMEmitter) c.LLVMTypeRef {
        if (self.frame_struct_type) |t| return t;
        const str_ty = self.getStringStructType();
        var field_types = [_]c.LLVMTypeRef{
            str_ty, // file
            self.cached_i32, // line
            self.cached_i32, // col
            str_ty, // func
            str_ty, // line_text (the source line, for the snippet)
        };
        self.frame_struct_type = c.LLVMStructTypeInContext(self.context, &field_types, 5, 0);
        return self.frame_struct_type.?;
    }

    /// An interned constant sx `string` (`{ ptr, i64 }`) of the cached string
    /// struct type, backed by a private NUL-terminated data global. Cached by
    /// content so a path/name shared by many push sites is emitted once.
    fn buildStringConst(self: *LLVMEmitter, s: []const u8) c.LLVMValueRef {
        if (self.frame_str_cache.get(s)) |v| return v;
        const str_z = self.alloc.dupeZ(u8, s) catch unreachable;
        defer self.alloc.free(str_z);
        const data = c.LLVMAddGlobal(self.llvm_module, c.LLVMArrayType(self.cached_i8, @intCast(s.len + 1)), "frame.str");
        c.LLVMSetInitializer(data, c.LLVMConstStringInContext(self.context, str_z.ptr, @intCast(s.len + 1), 1));
        c.LLVMSetGlobalConstant(data, 1);
        c.LLVMSetLinkage(data, c.LLVMPrivateLinkage);
        c.LLVMSetUnnamedAddress(data, c.LLVMGlobalUnnamedAddr);
        var fields = [_]c.LLVMValueRef{ data, c.LLVMConstInt(self.cached_i64, s.len, 0) };
        const str_const = c.LLVMConstNamedStruct(self.getStringStructType(), &fields, 2);
        const key = self.alloc.dupe(u8, s) catch return str_const;
        self.frame_str_cache.put(key, str_const) catch self.alloc.free(key);
        return str_const;
    }

    /// Build the interned `Frame` global for a `.trace_frame` push site and
    /// return its address as `i64` (the value `sx_trace_push` stores). Resolves
    /// the instruction's span + current function to `{file,line,col,func}`. The
    /// file is shown as its basename so trace output is machine-independent
    /// (the harness passes absolute paths); full paths live in DWARF.
    fn emitTraceFrame(self: *LLVMEmitter, instruction: *const Inst) c.LLVMValueRef {
        const file = std.fs.path.basename(self.current_func_file);
        const src = self.sourceForFile(self.current_func_file);
        const loc = errors.SourceLoc.compute(src, instruction.span.start);
        const func_name = self.ir_mod.types.getString(self.ir_mod.functions.items[self.current_func_idx].name);

        var fields = [_]c.LLVMValueRef{
            self.buildStringConst(file),
            c.LLVMConstInt(self.cached_i32, loc.line, 0),
            c.LLVMConstInt(self.cached_i32, loc.col, 0),
            self.buildStringConst(func_name),
            self.buildStringConst(errors.lineAt(src, instruction.span.start)),
        };
        const frame_ty = self.getFrameStructType();
        const frame_const = c.LLVMConstNamedStruct(frame_ty, &fields, 5);
        const g = c.LLVMAddGlobal(self.llvm_module, frame_ty, "trace.frame");
        c.LLVMSetInitializer(g, frame_const);
        c.LLVMSetGlobalConstant(g, 1);
        c.LLVMSetLinkage(g, c.LLVMPrivateLinkage);
        return c.LLVMConstPtrToInt(g, self.cached_i64);
    }

    fn getAnyStructType(self: *LLVMEmitter) c.LLVMTypeRef {
        if (self.any_struct_type) |t| return t;
        var field_types = [_]c.LLVMTypeRef{
            self.cached_i64, // type tag
            self.cached_i64, // value
        };
        self.any_struct_type = c.LLVMStructTypeInContext(self.context, &field_types, 2, 0);
        return self.any_struct_type.?;
    }

    fn getClosureStructType(self: *LLVMEmitter) c.LLVMTypeRef {
        if (self.closure_struct_type) |t| return t;
        var field_types = [_]c.LLVMTypeRef{
            self.cached_ptr, // fn_ptr
            self.cached_ptr, // env
        };
        self.closure_struct_type = c.LLVMStructTypeInContext(self.context, &field_types, 2, 0);
        return self.closure_struct_type.?;
    }

    // ── String constant emission ────────────────────────────────────

    /// Build a constant string { ptr, i64 } value without using the builder
    /// (safe to call during global initialization, before any function body is emitted).
    fn emitConstStringGlobal(self: *LLVMEmitter, str: []const u8) c.LLVMValueRef {
        const str_z = self.alloc.dupeZ(u8, str) catch unreachable;
        defer self.alloc.free(str_z);
        const len: c_uint = @intCast(str.len + 1); // include null terminator
        const str_const = c.LLVMConstStringInContext(self.context, str_z.ptr, len - 1, 0);
        const arr_ty = c.LLVMArrayType2(self.cached_i8, len);
        const str_global_val = c.LLVMAddGlobal(self.llvm_module, arr_ty, "str.data");
        c.LLVMSetInitializer(str_global_val, str_const);
        c.LLVMSetGlobalConstant(str_global_val, 1);
        c.LLVMSetLinkage(str_global_val, c.LLVMPrivateLinkage);
        c.LLVMSetUnnamedAddress(str_global_val, c.LLVMGlobalUnnamedAddr);
        // Build constant { ptr, i64 } aggregate
        const len_val = c.LLVMConstInt(self.cached_i64, str.len, 0);
        var fields = [_]c.LLVMValueRef{ str_global_val, len_val };
        return c.LLVMConstStructInContext(self.context, &fields, 2, 0);
    }

    fn emitConstAggregate(self: *LLVMEmitter, agg: []const ir_inst.ConstantValue, llvm_ty: c.LLVMTypeRef) c.LLVMValueRef {
        const kind = c.LLVMGetTypeKind(llvm_ty);
        const is_struct = kind == c.LLVMStructTypeKind;
        const n: c_uint = @intCast(agg.len);
        const vals = self.alloc.alloc(c.LLVMValueRef, agg.len) catch return c.LLVMConstNull(llvm_ty);
        defer self.alloc.free(vals);
        for (agg, 0..) |cv, i| {
            const elem_ty = if (is_struct)
                c.LLVMStructGetTypeAtIndex(llvm_ty, @intCast(i))
            else
                c.LLVMGetElementType(llvm_ty);
            vals[i] = switch (cv) {
                .int => |v| c.LLVMConstInt(elem_ty, @bitCast(v), 1),
                .float => |v| c.LLVMConstReal(elem_ty, v),
                .boolean => |v| c.LLVMConstInt(elem_ty, @intFromBool(v), 0),
                .string => |sid| self.emitConstStringGlobal(self.ir_mod.types.getString(sid)),
                .aggregate => |inner| self.emitConstAggregate(inner, elem_ty),
                .func_ref => |fid| self.func_map.get(fid.index()) orelse c.LLVMConstNull(elem_ty),
                else => c.LLVMConstNull(elem_ty),
            };
        }
        if (is_struct) {
            return c.LLVMConstNamedStruct(llvm_ty, vals.ptr, n);
        }
        const elem_ty = c.LLVMGetElementType(llvm_ty);
        return c.LLVMConstArray(elem_ty, vals.ptr, n);
    }

    fn emitStringConstant(self: *LLVMEmitter, str: []const u8) c.LLVMValueRef {
        // LLVMBuildGlobalStringPtr needs a null-terminated C string
        const str_z = self.alloc.dupeZ(u8, str) catch unreachable;
        defer self.alloc.free(str_z);

        // Create a global constant string and return a fat pointer { ptr, len }
        const str_global = c.LLVMBuildGlobalStringPtr(self.builder, str_z.ptr, "str");
        const len_val = c.LLVMConstInt(self.cached_i64, str.len, 0);
        const str_ty = self.getStringStructType();
        const undef = c.LLVMGetUndef(str_ty);
        const with_ptr = c.LLVMBuildInsertValue(self.builder, undef, str_global, 0, "str.ptr");
        return c.LLVMBuildInsertValue(self.builder, with_ptr, len_val, 1, "str.len");
    }

    /// Emit a NUL-terminated C string as a private LLVM global and return
    /// the pointer to its first byte. Used for FindClass(env, "<path>") etc.
    /// where the runtime expects raw `const char *`, not the sx slice shape.
    fn emitCStringGlobal(self: *LLVMEmitter, str: []const u8, name: [*:0]const u8) c.LLVMValueRef {
        const z = self.alloc.dupeZ(u8, str) catch unreachable;
        defer self.alloc.free(z);
        return c.LLVMBuildGlobalStringPtr(self.builder, z.ptr, name);
    }

    /// Expand a JNI constructor dispatch (`Foo.new(args)` in sx). Chain:
    /// `FindClass(env, parent_class_path)` → `GetMethodID(env, clazz,
    /// "<init>", sig)` → `NewObject(env, clazz, mid, args...)`. Returns
    /// the new jobject. Per-call lookups — no caching yet.
    fn emitJniConstructor(self: *LLVMEmitter, msg: ir_inst.JniMsgSend, ret_ty_id: TypeId) void {
        const env = self.resolveRef(msg.env);
        const sig_ptr = self.extractSlicePtr(self.resolveRef(msg.sig));
        const name_ptr = self.extractSlicePtr(self.resolveRef(msg.name));

        const ifs = c.LLVMBuildLoad2(self.builder, self.cached_ptr, env, "jni.ifs");

        const path = msg.parent_class_path orelse "";
        const path_global = self.emitCStringGlobal(path, "jni.ctor.path");
        const find_class = self.loadJniFn(ifs, Jni.FindClass, "jni.FindClass");
        var fc_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr };
        const fc_ty = c.LLVMFunctionType(self.cached_ptr, &fc_params, 2, 0);
        var fc_args = [_]c.LLVMValueRef{ env, path_global };
        const cls = c.LLVMBuildCall2(self.builder, fc_ty, find_class, &fc_args, 2, "jni.ctor.cls");

        const get_mid = self.loadJniFn(ifs, Jni.GetMethodID, "jni.GetMethodID");
        var gmid_params = [_]c.LLVMTypeRef{ self.cached_ptr, self.cached_ptr, self.cached_ptr, self.cached_ptr };
        const gmid_ty = c.LLVMFunctionType(self.cached_ptr, &gmid_params, 4, 0);
        var gmid_args = [_]c.LLVMValueRef{ env, cls, name_ptr, sig_ptr };
        const mid = c.LLVMBuildCall2(self.builder, gmid_ty, get_mid, &gmid_args, 4, "jni.ctor.mid");

        const new_object = self.loadJniFn(ifs, Jni.NewObject, "jni.NewObject");
        const raw_ret = self.toLLVMType(ret_ty_id);
        const total_call_params: usize = 3 + msg.args.len;
        const call_param_types = self.alloc.alloc(c.LLVMTypeRef, total_call_params) catch unreachable;
        defer self.alloc.free(call_param_types);
        const call_args = self.alloc.alloc(c.LLVMValueRef, total_call_params) catch unreachable;
        defer self.alloc.free(call_args);
        call_param_types[0] = self.cached_ptr;
        call_param_types[1] = self.cached_ptr;
        call_param_types[2] = self.cached_ptr;
        call_args[0] = env;
        call_args[1] = cls;
        call_args[2] = mid;
        for (msg.args, 0..) |arg_ref, i| {
            const raw_ty = self.getRefIRType(arg_ref) orelse .void;
            const raw_llvm = self.toLLVMType(raw_ty);
            const coerced_ty = self.abiCoerceParamType(raw_ty, raw_llvm);
            call_param_types[i + 3] = coerced_ty;
            call_args[i + 3] = self.coerceArg(self.resolveRef(arg_ref), coerced_ty);
        }
        const call_fn_ty = c.LLVMFunctionType(raw_ret, call_param_types.ptr, @intCast(total_call_params), 0);
        const result = c.LLVMBuildCall2(self.builder, call_fn_ty, new_object, call_args.ptr, @intCast(total_call_params), "jni.new.obj");
        self.mapRef(result);
    }

    // ── Reflection emission helpers ────────────────────────────────

    /// Build (or return cached) a global constant array of {ptr, i64}
    /// string values indexed by `TypeId.index()`. Lets the dynamic
    /// `type_name(t)` builtin look up the type's display name at
    /// runtime — `gep arr[tid]; load string`. The array's length is
    /// the current `infos.items.len`; new types interned after this
    /// is built fall outside the array (the gep would OOB), so
    /// callers must build LAZILY after all types are registered.
    fn getOrBuildTypeNameArray(self: *LLVMEmitter) c.LLVMValueRef {
        if (self.type_name_array) |g| return g;

        const n: u32 = @intCast(self.ir_mod.types.infos.items.len);
        const string_ty = self.getStringStructType();

        var field_vals = std.ArrayList(c.LLVMValueRef).empty;
        defer field_vals.deinit(self.alloc);
        var i: u32 = 0;
        while (i < n) : (i += 1) {
            const tid = @import("types.zig").TypeId.fromIndex(i);
            const name_str = self.ir_mod.types.formatTypeName(self.alloc, tid);
            const str_z = self.alloc.dupeZ(u8, name_str) catch unreachable;
            defer self.alloc.free(str_z);
            const global_str = c.LLVMAddGlobal(self.llvm_module, c.LLVMArrayType(self.cached_i8, @intCast(name_str.len + 1)), "tn.str");
            c.LLVMSetInitializer(global_str, c.LLVMConstStringInContext(self.context, str_z.ptr, @intCast(name_str.len + 1), 1));
            c.LLVMSetGlobalConstant(global_str, 1);
            c.LLVMSetLinkage(global_str, c.LLVMPrivateLinkage);
            const len_val = c.LLVMConstInt(self.cached_i64, name_str.len, 0);
            var struct_fields = [2]c.LLVMValueRef{ global_str, len_val };
            const const_struct = c.LLVMConstStructInContext(self.context, &struct_fields, 2, 0);
            field_vals.append(self.alloc, const_struct) catch unreachable;
        }

        const arr_ty = c.LLVMArrayType(string_ty, n);
        const arr_init = c.LLVMConstArray(string_ty, field_vals.items.ptr, n);
        const global = c.LLVMAddGlobal(self.llvm_module, arr_ty, "__sx_type_names");
        c.LLVMSetInitializer(global, arr_init);
        c.LLVMSetGlobalConstant(global, 1);
        c.LLVMSetLinkage(global, c.LLVMPrivateLinkage);

        self.type_name_array = global;
        self.type_name_array_len = n;
        return global;
    }

    /// Build (or return cached) a global constant array of {ptr, i64} string values
    /// for the field names of a struct type.
    fn getOrBuildFieldNameArray(self: *LLVMEmitter, struct_type: TypeId) c.LLVMValueRef {
        if (self.field_name_arrays.get(struct_type.index())) |g| return g;

        const info = self.ir_mod.types.get(struct_type);

        // Collect name StringIds from struct fields, union fields, or enum variants
        var name_ids = std.ArrayList(StringId).empty;
        defer name_ids.deinit(self.alloc);
        switch (info) {
            .@"struct" => |s| {
                for (s.fields) |f| name_ids.append(self.alloc, f.name) catch unreachable;
            },
            .@"union" => |u| {
                for (u.fields) |f| name_ids.append(self.alloc, f.name) catch unreachable;
            },
            .tagged_union => |u| {
                for (u.fields) |f| name_ids.append(self.alloc, f.name) catch unreachable;
            },
            .@"enum" => |e| {
                for (e.variants) |v| name_ids.append(self.alloc, v) catch unreachable;
            },
            else => {},
        }

        const string_ty = self.getStringStructType();
        const n: u32 = @intCast(name_ids.items.len);

        // Build constant initializer: [N x {ptr, i64}]
        var field_vals = std.ArrayList(c.LLVMValueRef).empty;
        defer field_vals.deinit(self.alloc);
        for (name_ids.items) |name_id| {
            const name_str = self.ir_mod.types.getString(name_id);
            const str_z = self.alloc.dupeZ(u8, name_str) catch unreachable;
            defer self.alloc.free(str_z);
            const global_str = c.LLVMAddGlobal(self.llvm_module, c.LLVMArrayType(self.cached_i8, @intCast(name_str.len + 1)), "fld.str");
            c.LLVMSetInitializer(global_str, c.LLVMConstStringInContext(self.context, str_z.ptr, @intCast(name_str.len + 1), 1));
            c.LLVMSetGlobalConstant(global_str, 1);
            c.LLVMSetLinkage(global_str, c.LLVMPrivateLinkage);
            // Build fat pointer {ptr, len} as constant struct
            const len_val = c.LLVMConstInt(self.cached_i64, name_str.len, 0);
            var struct_fields = [2]c.LLVMValueRef{ global_str, len_val };
            const const_struct = c.LLVMConstStructInContext(self.context, &struct_fields, 2, 0);
            field_vals.append(self.alloc, const_struct) catch unreachable;
        }

        // Create global array [N x {ptr, i64}]
        const array_ty = c.LLVMArrayType(string_ty, n);
        const array_init = c.LLVMConstArray(string_ty, field_vals.items.ptr, n);
        const global = c.LLVMAddGlobal(self.llvm_module, array_ty, "field_names");
        c.LLVMSetInitializer(global, array_init);
        c.LLVMSetGlobalConstant(global, 1);
        c.LLVMSetLinkage(global, c.LLVMPrivateLinkage);

        self.field_name_arrays.put(struct_type.index(), global) catch unreachable;
        return global;
    }

    /// Failable main entry-point wrapper (ERR E4.2). At the LLVM level main
    /// returns i32. `tag_val` is the u32 error tag (0 = "no error"); `value` is
    /// the integer value slot for a value-carrying `-> (int, !)` main, or null
    /// for a pure `-> !` main. Emit the branch: tag == 0 → `ret i32 <value-or-0>`
    /// (success — exit code truncated to u8 downstream); else resolve the tag
    /// name from the always-linked tag-name table, hand it + the tag to
    /// `sx_trace_report_unhandled` (prints the header + return trace to stderr),
    /// and `ret i32 1`.
    fn emitFailableMainRet(self: *LLVMEmitter, value: ?c.LLVMValueRef, tag_val: c.LLVMValueRef) void {
        const llvm_func = c.LLVMGetBasicBlockParent(c.LLVMGetInsertBlock(self.builder));
        const tag_i32 = self.coerceArg(tag_val, self.cached_i32);

        const is_err = c.LLVMBuildICmp(self.builder, c.LLVMIntNE, tag_i32, c.LLVMConstInt(self.cached_i32, 0, 0), "main.iserr");
        const ok_bb = c.LLVMAppendBasicBlockInContext(self.context, llvm_func, "main.ok");
        const err_bb = c.LLVMAppendBasicBlockInContext(self.context, llvm_func, "main.err");
        _ = c.LLVMBuildCondBr(self.builder, is_err, err_bb, ok_bb);

        // Success: exit the value (truncated to u8 by the JIT/OS) or 0.
        c.LLVMPositionBuilderAtEnd(self.builder, ok_bb);
        const ok_ret = if (value) |v| self.coerceArg(v, self.cached_i32) else c.LLVMConstInt(self.cached_i32, 0, 0);
        _ = c.LLVMBuildRet(self.builder, ok_ret);

        // Error: resolve the tag name, report to stderr, exit 1.
        c.LLVMPositionBuilderAtEnd(self.builder, err_bb);
        const global = self.getOrBuildTagNameArray();
        const idx = c.LLVMBuildZExt(self.builder, tag_i32, self.cached_i64, "main.tagidx");
        const string_ty = self.getStringStructType();
        const n: u32 = @intCast(self.ir_mod.types.tags.names.items.len);
        const array_ty = c.LLVMArrayType(string_ty, n);
        const zero = c.LLVMConstInt(self.cached_i64, 0, 0);
        var indices = [2]c.LLVMValueRef{ zero, idx };
        const gep = c.LLVMBuildInBoundsGEP2(self.builder, array_ty, global, &indices, 2, "main.tag.gep");
        const name_struct = c.LLVMBuildLoad2(self.builder, string_ty, gep, "main.tag.name");
        const name_ptr = c.LLVMBuildExtractValue(self.builder, name_struct, 0, "main.tag.ptr");
        const name_len = c.LLVMBuildExtractValue(self.builder, name_struct, 1, "main.tag.len");

        const reporter, const reporter_ty = self.lazyDeclareCRuntime(
            "sx_trace_report_unhandled",
            &[_]c.LLVMTypeRef{ self.cached_i32, self.cached_ptr, self.cached_i64 },
            self.cached_void,
            0,
        );
        var args = [3]c.LLVMValueRef{ tag_i32, name_ptr, name_len };
        _ = c.LLVMBuildCall2(self.builder, reporter_ty, reporter, &args, 3, "");
        _ = c.LLVMBuildRet(self.builder, c.LLVMConstInt(self.cached_i32, 1, 0));
    }

    /// The always-linked tag-name table: a `[N x {ptr, i64}]` global of tag
    /// names indexed by global tag id (the `TagRegistry` namespace; slot 0 is
    /// the reserved "" no-error name). `error_tag_name_get` GEPs into it at the
    /// runtime tag id. Built once per module. Always emitted (not trace-gated)
    /// so `{}` interpolation of an error tag works even in release builds.
    fn getOrBuildTagNameArray(self: *LLVMEmitter) c.LLVMValueRef {
        if (self.tag_name_array) |g| return g;

        const string_ty = self.getStringStructType();
        const names = self.ir_mod.types.tags.names.items;

        var field_vals = std.ArrayList(c.LLVMValueRef).empty;
        defer field_vals.deinit(self.alloc);
        for (names) |name_str| {
            const str_z = self.alloc.dupeZ(u8, name_str) catch unreachable;
            defer self.alloc.free(str_z);
            const global_str = c.LLVMAddGlobal(self.llvm_module, c.LLVMArrayType(self.cached_i8, @intCast(name_str.len + 1)), "tag.str");
            c.LLVMSetInitializer(global_str, c.LLVMConstStringInContext(self.context, str_z.ptr, @intCast(name_str.len + 1), 1));
            c.LLVMSetGlobalConstant(global_str, 1);
            c.LLVMSetLinkage(global_str, c.LLVMPrivateLinkage);
            const len_val = c.LLVMConstInt(self.cached_i64, name_str.len, 0);
            var struct_fields = [2]c.LLVMValueRef{ global_str, len_val };
            const const_struct = c.LLVMConstStructInContext(self.context, &struct_fields, 2, 0);
            field_vals.append(self.alloc, const_struct) catch unreachable;
        }

        const n: u32 = @intCast(names.len);
        const array_ty = c.LLVMArrayType(string_ty, n);
        const array_init = c.LLVMConstArray(string_ty, field_vals.items.ptr, n);
        const global = c.LLVMAddGlobal(self.llvm_module, array_ty, "tag_names");
        c.LLVMSetInitializer(global, array_init);
        c.LLVMSetGlobalConstant(global, 1);
        c.LLVMSetLinkage(global, c.LLVMPrivateLinkage);

        self.tag_name_array = global;
        return global;
    }

    /// Emit field_value_get: switch on runtime index, each case extracts a field and boxes it as Any.
    fn emitFieldValueGet(self: *LLVMEmitter, fr: ir_inst.FieldReflect, func_idx: u32) void {
        const base_val = self.resolveRef(fr.base);
        const idx_val = self.resolveRef(fr.index);

        const info = self.ir_mod.types.get(fr.struct_type);
        const fields = switch (info) {
            .@"struct" => |s| s.fields,
            .@"union" => |u| u.fields,
            .tagged_union => |u| u.fields,
            else => &[_]TypeInfo.StructInfo.Field{},
        };

        if (fields.len == 0) {
            // No fields (e.g., plain enum) — return void-tagged Any so payload is empty
            const any_ty = self.getAnyStructType();
            const void_tag = c.LLVMConstInt(self.cached_i64, TypeId.void.index(), 0);
            var void_any = c.LLVMGetUndef(any_ty);
            void_any = c.LLVMBuildInsertValue(self.builder, void_any, void_tag, 0, "fv.vtag");
            void_any = c.LLVMBuildInsertValue(self.builder, void_any, c.LLVMConstInt(self.cached_i64, 0, 0), 1, "fv.vval");
            self.mapRef(void_any);
            return;
        }

        const any_ty = self.getAnyStructType();
        const current_func = self.func_map.get(func_idx) orelse {
            self.mapRef(c.LLVMGetUndef(any_ty));
            return;
        };

        // Create merge block
        const merge_bb = c.LLVMAppendBasicBlockInContext(self.context, current_func, "fv.merge");
        // Create default block (returns undef)
        const default_bb = c.LLVMAppendBasicBlockInContext(self.context, current_func, "fv.default");

        // Build switch
        const switch_inst = c.LLVMBuildSwitch(self.builder, idx_val, default_bb, @intCast(fields.len));

        // Emit case blocks
        var case_blocks = std.ArrayList(c.LLVMBasicBlockRef).empty;
        defer case_blocks.deinit(self.alloc);
        var case_values = std.ArrayList(c.LLVMValueRef).empty;
        defer case_values.deinit(self.alloc);

        const is_union = info == .@"union" or info == .tagged_union;
        for (fields, 0..) |field, i| {
            const case_bb = c.LLVMAppendBasicBlockInContext(self.context, current_func, "fv.case");
            c.LLVMAddCase(switch_inst, c.LLVMConstInt(self.cached_i64, @intCast(i), 0), case_bb);

            c.LLVMPositionBuilderAtEnd(self.builder, case_bb);
            var field_val: c.LLVMValueRef = undefined;
            if (is_union) {
                // Union: extract payload via alloca + GEP to payload area + bitcast + load
                if (field.ty == .void) {
                    // Void variant has no payload — use zero
                    field_val = c.LLVMConstInt(self.cached_i64, 0, 0);
                } else {
                    const base_ty = c.LLVMTypeOf(base_val);
                    const tmp = c.LLVMBuildAlloca(self.builder, base_ty, "fv.utmp");
                    _ = c.LLVMBuildStore(self.builder, base_val, tmp);
                    const payload_ptr = c.LLVMBuildStructGEP2(self.builder, base_ty, tmp, 1, "fv.pp");
                    const field_llvm_ty = self.toLLVMType(field.ty);
                    const typed_ptr = c.LLVMBuildBitCast(self.builder, payload_ptr, self.cached_ptr, "fv.cast");
                    field_val = c.LLVMBuildLoad2(self.builder, field_llvm_ty, typed_ptr, "fv.field");
                }
            } else {
                // Struct: direct extractvalue by field index
                field_val = c.LLVMBuildExtractValue(self.builder, base_val, @intCast(i), "fv.field");
            }
            // Box as Any: {type_tag, value_as_i64}
            const tag = c.LLVMConstInt(self.cached_i64, self.anyTag(field.ty), 0);
            const is_field_signed = self.isSignedTypeEx(field.ty);
            const val_i64 = if (is_field_signed) self.coerceToI64Signed(field_val) else self.coerceToI64(field_val);
            var any_val = c.LLVMGetUndef(any_ty);
            any_val = c.LLVMBuildInsertValue(self.builder, any_val, tag, 0, "fv.tag");
            any_val = c.LLVMBuildInsertValue(self.builder, any_val, val_i64, 1, "fv.val");
            _ = c.LLVMBuildBr(self.builder, merge_bb);

            case_blocks.append(self.alloc, case_bb) catch unreachable;
            case_values.append(self.alloc, any_val) catch unreachable;
        }

        // Default block: return undef Any
        c.LLVMPositionBuilderAtEnd(self.builder, default_bb);
        _ = c.LLVMBuildBr(self.builder, merge_bb);

        // Merge block: PHI
        c.LLVMPositionBuilderAtEnd(self.builder, merge_bb);
        const phi = c.LLVMBuildPhi(self.builder, any_ty, "fv.phi");
        // Add incoming from case blocks
        for (case_blocks.items, case_values.items) |bb, val| {
            c.LLVMAddIncoming(phi, @constCast(&val), @constCast(&bb), 1);
        }
        // Add incoming from default block
        const undef_any = c.LLVMGetUndef(any_ty);
        c.LLVMAddIncoming(phi, @constCast(&undef_any), @constCast(&default_bb), 1);

        self.mapRef(phi);
    }

    // ── Helpers ─────────────────────────────────────────────────────

    fn makeBlockKey(func_idx: u32, block_idx: u32) u64 {
        return (@as(u64, func_idx) << 32) | @as(u64, block_idx);
    }

    /// Dump the LLVM module to a string (for testing).
    pub fn dumpToString(self: *LLVMEmitter) []const u8 {
        const raw = c.LLVMPrintModuleToString(self.llvm_module);
        return std.mem.span(raw);
    }

    /// Verify the LLVM module. Returns true if valid.
    pub fn verify(self: *LLVMEmitter) bool {
        return c.LLVMVerifyModule(self.llvm_module, c.LLVMReturnStatusAction, null) == 0;
    }

    /// Verify the LLVM module, returning an error message on failure.
    pub fn verifyWithMessage(self: *LLVMEmitter) !void {
        var err_msg: [*c]u8 = null;
        if (c.LLVMVerifyModule(self.llvm_module, c.LLVMReturnStatusAction, &err_msg) != 0) {
            if (err_msg != null) {
                const msg = std.mem.span(err_msg);
                // Dump IR to /tmp for debugging
                _ = c.LLVMPrintModuleToFile(self.llvm_module, "/tmp/sx_debug.ll", null);
                std.debug.print("LLVM verification failed: {s}\n", .{msg});
                c.LLVMDisposeMessage(err_msg);
            }
            return error.VerificationFailed;
        }
    }

    /// Print the LLVM IR to stderr.
    pub fn printIR(self: *LLVMEmitter) void {
        const ir_str = c.LLVMPrintModuleToString(self.llvm_module);
        defer c.LLVMDisposeMessage(ir_str);
        const len = std.mem.len(ir_str);
        std.debug.print("{s}\n", .{ir_str[0..len]});
    }

    /// Emit the module as an object file to disk.
    pub fn emitObject(self: *LLVMEmitter, output_path: [*:0]const u8) !void {
        return self.emitToFile(output_path, c.LLVMObjectFile);
    }

    /// Emit the module as an assembly file to disk.
    pub fn emitAssembly(self: *LLVMEmitter, output_path: [*:0]const u8) !void {
        return self.emitToFile(output_path, c.LLVMAssemblyFile);
    }

    /// Emit the module as LLVM bitcode to disk (for emcc to recompile with a newer LLVM).
    pub fn emitBitcode(self: *LLVMEmitter, output_path: [*:0]const u8) !void {
        if (c.LLVMWriteBitcodeToFile(self.llvm_module, output_path) != 0) {
            return error.EmitFailed;
        }
    }

    /// Dump the LLVM IR to a file for debugging.
    pub fn dumpIRToFile(self: *LLVMEmitter, path: [*:0]const u8) void {
        _ = c.LLVMPrintModuleToFile(self.llvm_module, path, null);
    }

    /// Emit the module as an object file to a memory buffer (for JIT).
    pub fn emitObjectToMemory(self: *LLVMEmitter) !c.LLVMMemoryBufferRef {
        const tm = self.target_machine orelse return error.NoTargetMachine;
        var err_msg: [*c]u8 = null;
        var buf: c.LLVMMemoryBufferRef = null;
        if (c.LLVMTargetMachineEmitToMemoryBuffer(tm, self.llvm_module, c.LLVMObjectFile, &err_msg, &buf) != 0) {
            if (err_msg != null) {
                std.debug.print("failed to emit object to memory: {s}\n", .{std.mem.span(err_msg)});
                c.LLVMDisposeMessage(err_msg);
            }
            return error.EmitFailed;
        }
        return buf;
    }

    fn emitToFile(self: *LLVMEmitter, output_path: [*:0]const u8, file_type: c.LLVMCodeGenFileType) !void {
        const tm = self.target_machine orelse return error.NoTargetMachine;
        var err_msg: [*c]u8 = null;
        if (c.LLVMTargetMachineEmitToFile(tm, self.llvm_module, output_path, file_type, &err_msg) != 0) {
            if (err_msg != null) {
                std.debug.print("failed to emit file: {s}\n", .{std.mem.span(err_msg)});
                c.LLVMDisposeMessage(err_msg);
            }
            return error.EmitFailed;
        }
    }
    /// Check if an IR Ref's type is an unsigned integer (u8, u16, u32, u64).
    fn isRefUnsigned(self: *LLVMEmitter, ref: Ref) bool {
        if (ref.isNone()) return false;
        const func = &self.ir_mod.functions.items[self.current_func_idx];
        const ref_idx = ref.index();
        // Check function parameters first (refs 0..N-1)
        if (ref_idx < func.params.len) {
            const ty = func.params[ref_idx].ty;
            return ty == .u8 or ty == .u16 or ty == .u32 or ty == .u64;
        }
        for (func.blocks.items) |*block| {
            const first = block.first_ref;
            if (ref_idx >= first and ref_idx < first + @as(u32, @intCast(block.insts.items.len))) {
                const ty = block.insts.items[ref_idx - first].ty;
                return ty == .u8 or ty == .u16 or ty == .u32 or ty == .u64;
            }
        }
        return false;
    }
};

// ── Type classification helpers ─────────────────────────────────────

fn isFloatType(ty: TypeId) bool {
    return ty == .f32 or ty == .f64;
}

/// Check if a TypeId is a float type, including float vectors.
fn isFloatOrVecFloat(ty: TypeId, types: *const TypeTable) bool {
    if (ty == .f32 or ty == .f64) return true;
    if (!ty.isBuiltin()) {
        const info = types.get(ty);
        if (info == .vector) return info.vector.element == .f32 or info.vector.element == .f64;
    }
    return false;
}

fn isSignedType(ty: TypeId) bool {
    return switch (ty) {
        .s8, .s16, .s32, .s64, .isize => true,
        else => false,
    };
}

fn floatBits(ty: TypeId) u32 {
    return switch (ty) {
        .f32 => 32,
        .f64 => 64,
        else => 0,
    };
}

fn intBits(ty: TypeId) u32 {
    return switch (ty) {
        .s8, .u8 => 8,
        .s16, .u16 => 16,
        .s32, .u32 => 32,
        .s64, .u64 => 64,
        .bool => 1,
        .usize, .isize => 0, // target-dependent — caller must query pointer_size
        else => 64,
    };
}
