Union is not properly zero-initialized #1194

releasenotes.md

@@ -16,6 +16,7 @@
 - Generic modules parameterized with constants would sometimes get the wrong parameterized module name causing conversion errors #1192.
 - Duplicate emit of expressions on negation would incorrectly compile negated macros.
 - Casting a slice address to its pointer type should not compile #1193.
+- Union is not properly zero-initialized with designated initializer #1194.
 
 ### Stdlib changes
 - Add 'zstr' variants for `string::new_format` / `string::tformat`.

src/compiler/llvm_codegen_expr.c

@@ -2124,14 +2124,12 @@ static inline void llvm_emit_initialize_reference_designated(GenContext *c, BEVa
 		llvm_emit_initialize_reference_designated_bitstruct(c, ref, type->decl, elements);
 		return;
 	}
-	// Getting ready to initialize, get the real type.
-	Type *real_type = type_lowering(ref->type);
 
 	// Make sure we have an address.
 	llvm_value_addr(c, ref);
 
-	// Clear the memory if not union.
-	if (real_type->type_kind != TYPE_UNION) llvm_store_zero(c, ref);
+	// Clear the memory
+	llvm_store_zero(c, ref);
 
 	// Now walk through the elements.
 	VECEACH(elements, i)

test/test_suite/union/designated_union_zeroing.c3t

@@ -0,0 +1,33 @@
+// #target: macos-x64
+module test;
+union Rect {
+  struct { float[<2>] min, max; }
+}
+
+fn Rect test_rect(float[<2>] max) {
+  Rect rect = {.max = max};
+  assert(rect.min == {});
+  return rect;
+}
+
+/* #expect: test.ll
+
+%Rect = type { %.anon }
+%.anon = type { <2 x float>, <2 x float> }
+
+define { double, double } @test.test_rect(double %0) #0 {
+entry:
+  %max = alloca <2 x float>, align 8
+  %rect = alloca %Rect, align 8
+  store double %0, ptr %max, align 8
+  call void @llvm.memset.p0.i64(ptr align 8 %rect, i8 0, i64 16, i1 false)
+  %ptradd = getelementptr inbounds i8, ptr %rect, i64 8
+  %1 = load <2 x float>, ptr %max, align 8
+  store <2 x float> %1, ptr %ptradd, align 8
+  %2 = load <2 x float>, ptr %rect, align 8
+  %eq = fcmp oeq <2 x float> %2, zeroinitializer
+  %3 = call i1 @llvm.vector.reduce.and.v2i1(<2 x i1> %eq)
+  call void @llvm.assume(i1 %3)
+  %4 = load { double, double }, ptr %rect, align 8
+  ret { double, double } %4
+}

test/test_suite/union/union_codegen_const.c3t

@@ -1,3 +1,4 @@
+// #target: macos-x64
 module test;
 
 union Foo

test/test_suite/union/union_codegen_empty.c3t

@@ -1,3 +1,4 @@
+// #target: macos-x64
 union UnionA
 {
     int a;

test/test_suite/union/union_codegen_overwrite_call.c3t

@@ -1,3 +1,4 @@
+// #target: macos-x64
 module test;
 
 union UnionB