From 51491186cb045520ace001e005164a97a8695504 Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Thu, 20 Oct 2022 10:37:05 +0300
Subject: [PATCH] stage2: fix x86_64 C ABI of struct with array member

Closes #12185
---
 src/arch/x86_64/abi.zig | 13 +++++++++++++
 test/c_abi/cfuncs.c     | 15 +++++++++++++++
 test/c_abi/main.zig     | 16 ++++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/src/arch/x86_64/abi.zig b/src/arch/x86_64/abi.zig
index 298fc6656f72b2f860338124cd42121e2d46db2e..45c576054097d2b66bddaa10c8b7c7376daaa680 100644
--- a/src/arch/x86_64/abi.zig
+++ b/src/arch/x86_64/abi.zig
@@ -388,6 +388,19 @@ pub fn classifySystemV(ty: Type, target: Target) [8]Class {
             }
             return result;
         },
+        .Array => {
+            const ty_size = ty.abiSize(target);
+            if (ty_size <= 64) {
+                result[0] = .integer;
+                return result;
+            }
+            if (ty_size <= 128) {
+                result[0] = .integer;
+                result[1] = .integer;
+                return result;
+            }
+            return memory_class;
+        },
         else => unreachable,
     }
 }
diff --git a/test/c_abi/cfuncs.c b/test/c_abi/cfuncs.c
index 004dc9c4068c6754a50f5711d6af6b6bd3f70e44..382840e2aa17f3fe0385779bae8c9e742b9ca911 100644
--- a/test/c_abi/cfuncs.c
+++ b/test/c_abi/cfuncs.c
@@ -596,3 +596,18 @@ int32_t c_ret_i32() {
 int64_t c_ret_i64() {
     return -1;
 }
+
+typedef struct {
+    uint32_t a;
+    uint8_t padding[4];
+    uint64_t b;
+} StructWithArray;
+
+void c_struct_with_array(StructWithArray x) {
+    assert_or_panic(x.a == 1);
+    assert_or_panic(x.b == 2);
+}
+
+StructWithArray c_ret_struct_with_array() {
+    return (StructWithArray) { 4, {}, 155 };
+}
diff --git a/test/c_abi/main.zig b/test/c_abi/main.zig
index 9344c2efaee49af836e887d0301dabbf174c451b..6f1b336b011d145e45e3df1de6ed014cafd8c57b 100644
--- a/test/c_abi/main.zig
+++ b/test/c_abi/main.zig
@@ -665,3 +665,19 @@ test "C ABI integer return types" {
     try expect(c_ret_i32() == -1);
     try expect(c_ret_i64() == -1);
 }
+
+const StructWithArray = extern struct {
+    a: i32,
+    padding: [4]u8,
+    b: i64,
+};
+extern fn c_struct_with_array(StructWithArray) void;
+extern fn c_ret_struct_with_array() StructWithArray;
+
+test "Struct with array as padding." {
+    c_struct_with_array(.{ .a = 1, .padding = undefined, .b = 2 });
+
+    var x = c_ret_struct_with_array();
+    try std.testing.expect(x.a == 4);
+    try std.testing.expect(x.b == 155);
+}
-- 
2.54.0