05

src/ir/module.zig

@@ -130,14 +130,38 @@ pub const Builder = struct {
     // ── Function setup ──────────────────────────────────────────────
 
     pub fn beginFunction(self: *Builder, name: StringId, params: []const Function.Param, ret_ty: TypeId) FuncId {
+        // Check if there's an existing extern stub with this name — upgrade it in-place
+        for (self.module.functions.items, 0..) |*existing, i| {
+            if (existing.name == name and existing.is_extern) {
+                existing.is_extern = false;
+                existing.linkage = .internal;
+                existing.params = self.module.alloc.dupe(Function.Param, params) catch params;
+                existing.ret = ret_ty;
+                const id = FuncId.fromIndex(@intCast(i));
+                self.func = id;
+                self.inst_counter = @intCast(params.len);
+                self.current_block = null;
+                return id;
+            }
+        }
         const func = Function.init(name, params, ret_ty);
         const id = self.module.addFunction(func);
         self.func = id;
-        self.inst_counter = 0;
+        // Reserve refs 0..N-1 for function parameters; instructions start at ref N.
+        self.inst_counter = @intCast(params.len);
         self.current_block = null;
         return id;
     }
 
+    /// Declare an extern function (no body, external linkage).
+    pub fn declareExtern(self: *Builder, name: StringId, params: []const Function.Param, ret_ty: TypeId) FuncId {
+        var func = Function.init(name, params, ret_ty);
+        func.is_extern = true;
+        func.linkage = .external;
+        const id = self.module.addFunction(func);
+        return id;
+    }
+
     pub fn finalize(self: *Builder) void {
         self.func = null;
         self.current_block = null;
@@ -160,6 +184,24 @@ pub const Builder = struct {
 
     pub fn switchToBlock(self: *Builder, block: BlockId) void {
         self.current_block = block;
+        // Record the starting ref index for this block
+        const func = self.currentFunc();
+        const blk = &func.blocks.items[block.index()];
+        blk.first_ref = self.inst_counter;
+    }
+
+    /// Get the type of a previously emitted instruction Ref.
+    pub fn getRefType(self: *Builder, ref: Ref) TypeId {
+        if (self.func == null) return .s64;
+        const func = self.currentFunc();
+        const ref_idx = @intFromEnum(ref);
+        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))) {
+                return block.insts.items[ref_idx - first].ty;
+            }
+        }
+        return .s64;
     }
 
     // ── Emit helpers ────────────────────────────────────────────────
@@ -405,7 +447,7 @@ pub const Builder = struct {
 
     // ── Internal helpers ────────────────────────────────────────────
 
-    fn currentFunc(self: *Builder) *Function {
+    pub fn currentFunc(self: *Builder) *Function {
         return self.module.getFunctionMut(self.func.?);
     }