// issue-0025: Composite types larger than 16 bytes are passed without the
// LLVM `byval(<ty>)` attribute, and the `call_indirect` (fn-pointer cast)
// path doesn't apply C-ABI parameter coercion at all. Both gaps cause
// silent shape-mismatch when sx code calls foreign C functions that take
// large aggregates by value, OR when sx code calls a sx fn through a
// fn-pointer typed with a large-aggregate parameter.
//
// ── Two failing forms ─────────────────────────────────────────────────────
//
// (A) Direct call to a sx function with a >16B param:
//
//     Wide :: struct { a: s64; b: s64; c: s64; d: s64; }   // 32 bytes
//     accept :: (w: Wide) -> s64 { w.a + w.b + w.c + w.d; }
//     accept(Wide.{ a = 1, b = 10, c = 100, d = 1000 })   // expect 1111
//
//   src/ir/emit_llvm.zig:2747-2795 (`abiCoerceParamType`):
//     - <=8 bytes  → coerced to i64
//     - 9-16 bytes → coerced to [2 x i64]
//     - >16 bytes  → returns llvm_ty unchanged with TODO at line 2793
//
//   The TODO is the bug: large composites should be coerced to `ptr`
//   with a `byval(struct.T)` LLVM attribute. LLVM's mid-end then
//   materializes the right machine code per target. Today the struct
//   is left as-is, which LLVM tries to pass across registers + stack
//   slots in ways that don't match the C ABI promise.
//
// (B) Indirect call via fn-pointer cast (the `xx objc_msgSend` idiom):
//
//     fn_ptr : (Wide) -> s64 = xx accept;
//     fn_ptr(Wide.{ ... })
//
//   src/ir/emit_llvm.zig:902-967 (`.call_indirect`): both the
//   FunctionInfo-known arm (939-952) and the LLVMTypeOf-fallback arm
//   (953-956) construct `param_tys[j]` WITHOUT routing through
//   `abiCoerceParamType`. So even if (A) is fixed, fn-pointer-cast call
//   sites still mis-marshal large composites.
//
// ── Real-world impact ──────────────────────────────────────────────────────
//
// Every `xx objc_msgSend` call site in library/modules/platform/uikit.sx
// + library/modules/gpu/metal.sx. Works in practice today only because:
//   - We never pass aggregates >16 bytes by value through fn-pointer casts
//     (workaround: declare param as `*T` + pass `@local`; arm64 AAPCS's
//     indirect-by-ref happens to match this machine-state-wise).
//   - HFAs (CGSize 2×f64, MTLClearColor 4×f64, CGRect 4×f64 as return)
//     are correctly classified at emit_llvm.zig:2766-2779.
//
// ── Workarounds in use ─────────────────────────────────────────────────────
//
// library/modules/gpu/metal.sx declares MTLRegion (48B) + MTLScissorRect
// (32B) call sites with `*MTLRegion` / `*MTLScissorRect` and passes
// `@region` / `@rect`. Should not be needed once this issue is fixed.
//
// ── Fix sketch ─────────────────────────────────────────────────────────────
//
// (A) emit_llvm.zig:2793 — return `ptr` and emit `byval(struct.T)` on
//     the param via `LLVMAddCallSiteAttribute` / `LLVMCreateTypeAttribute`.
//     At call sites, alloca + memcpy + pass the alloca pointer. Apply
//     identically at function-definition emission so direct calls roundtrip.
//
// (B) emit_llvm.zig:902-967 — factor out a helper
//     `coerceCallParams(param_count, src_args, dst_fn_param_tys)
//        -> (coerced_args, coerced_tys)` that wraps `abiCoerceParamType`.
//     Use the helper from both arms.
//
// Edge cases to preserve:
//   - Variadic foreign functions (printf family) — variadic tail per
//     AAPCS64 still passes composites in their natural form. Keep
//     existing behavior for variadic args.
//   - HFAs already handled at 2766-2779 — don't touch.
//   - Structs <=8 bytes coerced to `i64`, 9-16 bytes to `[2 x i64]` —
//     don't touch.

#import "modules/std.sx";

Wide :: struct {
    a: s64; b: s64; c: s64; d: s64;
}

accept :: (w: Wide) -> s64 {
    w.a + w.b + w.c + w.d;
}

main :: () -> s32 {
    w := Wide.{ a = 1, b = 10, c = 100, d = 1000 };
    direct := accept(w);             // exercises path (A)
    if direct != 1111 { return 1; }

    fn_ptr : (Wide) -> s64 = xx accept;
    indirect := fn_ptr(w);           // exercises path (B)
    if indirect != 1111 { return 2; }

    0;
}