| Issue |
135551
|
| Summary |
[AArch64] Argument passing is not ABI-compatible with GCC
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
hvdijk
|
```console
$ cat test.cc
struct X {
alignas(16) int F[4];
};
struct Y : X {};
void f(Y);
void g(int, Y y) { f(y); }
$ g++ -S -O3 -o - test.cc
.arch armv8-a
.file "test.cc"
.text
.align 2
.p2align 5,,15
.global _Z1gi1Y
.type _Z1gi1Y, %function
_Z1gi1Y:
.LFB0:
.cfi_startproc
mov x0, x2
mov x1, x3
b _Z1f1Y
.cfi_endproc
.LFE0:
.size _Z1gi1Y, .-_Z1gi1Y
.ident "GCC: (Ubuntu 14.2.0-19ubuntu2) 14.2.0"
.section .note.GNU-stack,"",@progbits
$ clang++ -S -O3 -o - test.cc
.file "test.cc"
.text
.globl _Z1gi1Y // -- Begin function _Z1gi1Y
.p2align 2
.type _Z1gi1Y,@function
_Z1gi1Y: // @_Z1gi1Y
.cfi_startproc
// %bb.0:
mov x0, x1
mov x1, x2
b _Z1f1Y
.Lfunc_end0:
.size _Z1gi1Y, .Lfunc_end0-_Z1gi1Y
.cfi_endproc
// -- End function
.ident "Ubuntu clang version 20.1.2 (0ubuntu1)"
.section ".note.GNU-stack","",@progbits
.addrsig
```
Clang is expecting `g`'s `Y` parameter to be passed in `x1`, `x2`, but GCC is expecting it to be passed in `x2`, `x3`.
If I remove the `alignas(16)`, GCC and Clang agree that it should be passed in `x1`, `x2`.
I do not know whether this is a bug in GCC or in Clang.
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