IR emit C ABI compatible types for calling conventions (Only for x86/amd64 like processors at the moment)

src/check_expr.c

@@ -1014,6 +1014,50 @@ Type *check_get_results(Checker *c, Scope *scope, AstNode *_results) {
 	return tuple;
 }
 
+Type *type_to_abi_compat_param_type(gbAllocator a, Type *original_type) {
+	Type *new_type = original_type;
+	// NOTE(bill): Changing the passing parameter value type is to match C's ABI
+	// IMPORTANT TODO(bill): This only matches the ABI on MSVC at the moment
+	Type *bt = core_type(original_type);
+	switch (bt->kind) {
+	// Okay to pass by value
+	// Especially the only Odin types
+	case Type_Basic:   break;
+	case Type_Pointer: break;
+	case Type_Proc:    break; // NOTE(bill): Just a pointer
+
+	// Odin only types
+	case Type_Slice:
+	case Type_DynamicArray:
+	case Type_Map:
+		break;
+
+	// Odin specific
+	case Type_Array:
+	case Type_Vector:
+	// Could be in C too
+	case Type_Record: {
+		i64 size = type_size_of(a, original_type);
+		switch (8*size) {
+		case 8:  new_type = t_u8;  break;
+		case 16: new_type = t_u16; break;
+		case 32: new_type = t_u32; break;
+		case 64: new_type = t_u64; break;
+		default:
+			// NOTE(bill): It could be an empty struct that is passed
+			// and if that is the case, no need to pass by pointer
+			// (I think..)
+			if (size > 0) {
+				new_type = make_type_pointer(a, original_type);
+			}
+			break;
+		}
+	} break;
+	}
+
+	return new_type;
+}
+
 
 void check_procedure_type(Checker *c, Type *type, AstNode *proc_type_node) {
 	ast_node(pt, ProcType, proc_type_node);
@@ -1034,6 +1078,20 @@ void check_procedure_type(Checker *c, Type *type, AstNode *proc_type_node) {
 	type->Proc.result_count       = result_count;
 	type->Proc.variadic           = variadic;
 	type->Proc.calling_convention = pt->calling_convention;
+
+
+	type->Proc.abi_compat_params = gb_alloc_array(c->allocator, Type *, param_count);
+	for (isize i = 0; i < param_count; i++) {
+		Type *original_type = type->Proc.params->Tuple.variables[i]->type;
+		Type *new_type = type_to_abi_compat_param_type(c->allocator, original_type);
+		type->Proc.abi_compat_params[i] = new_type;
+	}
+
+	// NOTE(bill): The types are the same
+	type->Proc.abi_compat_results = gb_alloc_array(c->allocator, Type *, result_count);
+	for (isize i = 0; i < result_count; i++) {
+		type->Proc.abi_compat_results[i] = type->Proc.results->Tuple.variables[i]->type;
+	}
 }