Merge pull request #14357 from kcbanner/llvm_byval_struct

llvm: implement Stdcall calling convention

test/c_abi/cfuncs.c

@@ -985,3 +985,33 @@ f128_struct c_f128_struct(f128_struct a) {
     return (f128_struct){56.78};
 }
 #endif
+
+void __attribute__((stdcall)) stdcall_scalars(char a, short b, int c, float d, double e) {
+    assert_or_panic(a == 1);
+    assert_or_panic(b == 2);
+    assert_or_panic(c == 3);
+    assert_or_panic(d == 4.0);
+    assert_or_panic(e == 5.0);
+}
+
+typedef struct {
+    short x;
+    short y;
+} Coord2;
+
+Coord2 __attribute__((stdcall)) stdcall_coord2(Coord2 a, Coord2 b, Coord2 c) {
+    assert_or_panic(a.x == 0x1111);
+    assert_or_panic(a.y == 0x2222);
+    assert_or_panic(b.x == 0x3333);
+    assert_or_panic(b.y == 0x4444);
+    assert_or_panic(c.x == 0x5555);
+    assert_or_panic(c.y == 0x6666);
+    return (Coord2){123, 456};
+}
+
+void __attribute__((stdcall)) stdcall_big_union(union BigUnion x) {
+    assert_or_panic(x.a.a == 1);
+    assert_or_panic(x.a.b == 2);
+    assert_or_panic(x.a.c == 3);
+    assert_or_panic(x.a.d == 4);
+}

test/c_abi/main.zig

@@ -1146,3 +1146,47 @@ test "f128 struct" {
     const a = c_f128_struct(.{ .a = 12.34 });
     try expect(@floatCast(f64, a.a) == 56.78);
 }
+
+// The stdcall attribute on C functions is ignored when compiled on non-x86
+const stdcall_callconv: std.builtin.CallingConvention = if (builtin.cpu.arch == .x86) .Stdcall else .C;
+
+extern fn stdcall_scalars(i8, i16, i32, f32, f64) callconv(stdcall_callconv) void;
+test "Stdcall ABI scalars" {
+    stdcall_scalars(1, 2, 3, 4.0, 5.0);
+}
+
+const Coord2 = extern struct {
+    x: i16,
+    y: i16,
+};
+
+extern fn stdcall_coord2(Coord2, Coord2, Coord2) callconv(stdcall_callconv) Coord2;
+test "Stdcall ABI structs" {
+    if (comptime builtin.cpu.arch.isMIPS()) return error.SkipZigTest;
+    if (comptime builtin.cpu.arch.isPPC()) return error.SkipZigTest;
+    if (comptime builtin.cpu.arch.isPPC64()) return error.SkipZigTest;
+
+    const res = stdcall_coord2(
+        .{ .x = 0x1111, .y = 0x2222 },
+        .{ .x = 0x3333, .y = 0x4444 },
+        .{ .x = 0x5555, .y = 0x6666 },
+    );
+    try expect(res.x == 123);
+    try expect(res.y == 456);
+}
+
+extern fn stdcall_big_union(BigUnion) callconv(stdcall_callconv) void;
+test "Stdcall ABI big union" {
+    if (comptime builtin.cpu.arch.isPPC()) return error.SkipZigTest;
+
+    var x = BigUnion{
+        .a = BigStruct{
+            .a = 1,
+            .b = 2,
+            .c = 3,
+            .d = 4,
+            .e = 5,
+        },
+    };
+    stdcall_big_union(x);
+}