Commit c70c333594

Jacob Young <jacobly0@users.noreply.github.com>
2023-12-04 19:31:34
x86_64: fix packed struct field reuse
master
1 parent bdb6546
Changed files (2)
src
arch
x86_64
CodeGen.zig
test
behavior
packed-struct.zig
src/arch/x86_64/CodeGen.zig
@@ -7324,8 +7324,8 @@ fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
             .load_frame => |frame_addr| {
                 const field_abi_size: u32 = @intCast(field_ty.abiSize(mod));
                 if (field_off % 8 == 0) {
-                    const off_mcv =
-                        src_mcv.address().offset(@intCast(@divExact(field_off, 8))).deref();
+                    const field_byte_off = @divExact(field_off, 8);
+                    const off_mcv = src_mcv.address().offset(@intCast(field_byte_off)).deref();
                     const field_bit_size = field_ty.bitSize(mod);
 
                     if (field_abi_size <= 8) {
@@ -7350,7 +7350,9 @@ fn airStructFieldVal(self: *Self, inst: Air.Inst.Index) !void {
                             try self.copyToRegisterWithInstTracking(inst, field_ty, dst_mcv);
                     }
 
-                    const dst_mcv = if (self.reuseOperand(inst, operand, 0, src_mcv))
+                    const container_abi_size: u32 = @intCast(container_ty.abiSize(mod));
+                    const dst_mcv = if (field_byte_off + field_abi_size <= container_abi_size and
+                        self.reuseOperand(inst, operand, 0, src_mcv))
                         off_mcv
                     else dst: {
                         const dst_mcv = try self.allocRegOrMem(inst, true);
test/behavior/packed-struct.zig
@@ -804,7 +804,6 @@ test "nested packed struct at non-zero offset" {
 }
 
 test "nested packed struct at non-zero offset 2" {
-    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO