Fix WASM C ABI for raw unions

1 files changed, 56 insertions, 14 deletions

diff --git a/src/llvm_abi.cpp b/src/llvm_abi.cpp
index af08722c3..e1cbe7558 100644
--- a/src/llvm_abi.cpp
+++ b/src/llvm_abi.cpp
@@ -1313,7 +1313,7 @@ namespace lbAbiWasm {
 		            registers/arguments if possible rather than by pointer.
 	*/
 	gb_internal Array<lbArgType> compute_arg_types(LLVMContextRef c, LLVMTypeRef *arg_types, unsigned arg_count, ProcCallingConvention calling_convention, Type *original_type);
-	gb_internal LB_ABI_COMPUTE_RETURN_TYPE(compute_return_type);
+	gb_internal lbArgType compute_return_type(lbFunctionType *ft, LLVMContextRef c, LLVMTypeRef return_type, bool return_is_defined, bool return_is_tuple, Type* original_type);
 
 	enum {MAX_DIRECT_STRUCT_SIZE = 32};
 
@@ -1323,7 +1323,9 @@ namespace lbAbiWasm {
 		ft->ctx = c;
 		ft->calling_convention = calling_convention;
 		ft->args = compute_arg_types(c, arg_types, arg_count, calling_convention, original_type);
-		ft->ret = compute_return_type(ft, c, return_type, return_is_defined, return_is_tuple);
+
+		GB_ASSERT(original_type->kind == Type_Proc);
+		ft->ret = compute_return_type(ft, c, return_type, return_is_defined, return_is_tuple, original_type->Proc.results);
 		return ft;
 	}
 
@@ -1359,7 +1361,7 @@ namespace lbAbiWasm {
 		return false;
 	}
 
-	gb_internal bool type_can_be_direct(LLVMTypeRef type, ProcCallingConvention calling_convention) {
+	gb_internal bool type_can_be_direct(LLVMTypeRef type, Type *original_type, ProcCallingConvention calling_convention) {
 		LLVMTypeKind kind = LLVMGetTypeKind(type);
 		i64 sz = lb_sizeof(type);
 		if (sz == 0) {
@@ -1372,9 +1374,21 @@ namespace lbAbiWasm {
 				return false;
 			} else if (kind == LLVMStructTypeKind) {
 				unsigned count = LLVMCountStructElementTypes(type);
+
+				// NOTE(laytan): raw unions are always structs with 1 field in LLVM, need to check our own def.
+				Type *bt = base_type(original_type);
+				if (bt->kind == Type_Struct && bt->Struct.is_raw_union) {
+					count = cast(unsigned)bt->Struct.fields.count;
+				}
+
 				if (count == 1) {
-					return type_can_be_direct(LLVMStructGetTypeAtIndex(type, 0), calling_convention);
+					return type_can_be_direct(
+						LLVMStructGetTypeAtIndex(type, 0),
+						type_internal_index(original_type, 0),
+						calling_convention
+					);
 				}
+
 			} else if (is_basic_register_type(type)) {
 				return true;
 			}
@@ -1398,7 +1412,7 @@ namespace lbAbiWasm {
 		return false;
 	}
 
-	gb_internal lbArgType is_struct(LLVMContextRef c, LLVMTypeRef type, ProcCallingConvention calling_convention) {
+	gb_internal lbArgType is_struct(LLVMContextRef c, LLVMTypeRef type, Type *original_type, ProcCallingConvention calling_convention) {
 		LLVMTypeKind kind = LLVMGetTypeKind(type);
 		GB_ASSERT(kind == LLVMArrayTypeKind || kind == LLVMStructTypeKind);
 		
@@ -1406,15 +1420,15 @@ namespace lbAbiWasm {
 		if (sz == 0) {
 			return lb_arg_type_ignore(type);
 		}
-		if (type_can_be_direct(type, calling_convention)) {
+		if (type_can_be_direct(type, original_type, calling_convention)) {
 			return lb_arg_type_direct(type);
 		}
 		return lb_arg_type_indirect(type, nullptr);
 	}
 	
-	gb_internal lbArgType pseudo_slice(LLVMContextRef c, LLVMTypeRef type, ProcCallingConvention calling_convention) {
+	gb_internal lbArgType pseudo_slice(LLVMContextRef c, LLVMTypeRef type, Type *original_type, ProcCallingConvention calling_convention) {
 		if (build_context.metrics.ptr_size < build_context.metrics.int_size &&
-		    type_can_be_direct(type, calling_convention)) {
+		    type_can_be_direct(type, original_type, calling_convention)) {
 			LLVMTypeRef types[2] = {
 				LLVMStructGetTypeAtIndex(type, 0),
 				// ignore padding
@@ -1423,7 +1437,7 @@ namespace lbAbiWasm {
 			LLVMTypeRef new_type = LLVMStructTypeInContext(c, types, gb_count_of(types), false);
 			return lb_arg_type_direct(type, new_type, nullptr, nullptr);
 		} else {
-			return is_struct(c, type, calling_convention);
+			return is_struct(c, type, original_type, calling_convention);
 		}
 	}
 
@@ -1444,9 +1458,9 @@ namespace lbAbiWasm {
 			LLVMTypeKind kind = LLVMGetTypeKind(t);
 			if (kind == LLVMStructTypeKind || kind == LLVMArrayTypeKind) {
 				if (is_type_slice(ptype) || is_type_string(ptype)) {
-					args[i] = pseudo_slice(c, t, calling_convention);
+					args[i] = pseudo_slice(c, t, ptype, calling_convention);
 				} else {
-					args[i] = is_struct(c, t, calling_convention);
+					args[i] = is_struct(c, t, ptype, calling_convention);
 				}
 			} else {
 				args[i] = non_struct(c, t, false);
@@ -1455,11 +1469,11 @@ namespace lbAbiWasm {
 		return args;
 	}
 
-	gb_internal LB_ABI_COMPUTE_RETURN_TYPE(compute_return_type) {
+	gb_internal lbArgType compute_return_type(lbFunctionType *ft, LLVMContextRef c, LLVMTypeRef return_type, bool return_is_defined, bool return_is_tuple, Type* original_type) {
 		if (!return_is_defined) {
 			return lb_arg_type_direct(LLVMVoidTypeInContext(c));
 		} else if (lb_is_type_kind(return_type, LLVMStructTypeKind) || lb_is_type_kind(return_type, LLVMArrayTypeKind)) {
-			if (type_can_be_direct(return_type, ft->calling_convention)) {
+			if (type_can_be_direct(return_type, original_type, ft->calling_convention)) {
 				return lb_arg_type_direct(return_type);
 			} else if (ft->calling_convention != ProcCC_CDecl) {
 				i64 sz = lb_sizeof(return_type);
@@ -1471,7 +1485,35 @@ namespace lbAbiWasm {
 				}
 			}
 
-			LB_ABI_MODIFY_RETURN_IF_TUPLE_MACRO();
+			// Multiple returns.
+			if (return_is_tuple) {                                                                                      \
+				lbArgType return_arg = {};
+				if (lb_is_type_kind(return_type, LLVMStructTypeKind)) {
+					unsigned field_count = LLVMCountStructElementTypes(return_type);
+					if (field_count > 1) {
+						ft->original_arg_count = ft->args.count;
+						ft->multiple_return_original_type = return_type;
+
+						for (unsigned i = 0; i < field_count-1; i++) {
+							LLVMTypeRef field_type = LLVMStructGetTypeAtIndex(return_type, i);
+							LLVMTypeRef field_pointer_type = LLVMPointerType(field_type, 0);
+							lbArgType ret_partial = lb_arg_type_direct(field_pointer_type);
+							array_add(&ft->args, ret_partial);
+						}
+
+						return_arg = compute_return_type(
+							ft,
+							c,
+							LLVMStructGetTypeAtIndex(return_type, field_count-1),
+							true, false,
+							type_internal_index(original_type, field_count-1)
+						);
+					}
+				}
+				if (return_arg.type != nullptr) {
+					return return_arg;
+				}
+			}
 
 			LLVMAttributeRef attr = lb_create_enum_attribute_with_type(c, "sret", return_type);
 			return lb_arg_type_indirect(return_type, attr);