| Issue |
176095
|
| Summary |
[AArch64] Wrong code at -Os on aarch64-unknown-linux-musl
|
| Labels |
backend:AArch64,
miscompilation,
generated by fuzzer
|
| Assignees |
|
| Reporter |
XChy
|
Reduced C testcase:
```c
#include <stdint.h>
#include <stdio.h>
#include <arm_neon.h>
#define BS_VEC(type, num) type __attribute__((vector_size(num * sizeof(type))))
#define BARRIER_v2u64(x) ((BS_VEC(uint64_t, 2))vqaddq_u64(x, (BS_VEC(uint64_t, 2)){}))
#define BARRIER_v16u8(x) ((BS_VEC(uint8_t, 16))vqaddq_u8(x, (uint8x16_t){}))
// BARRIER_xxxx(x) should be equivalent to x.
uint64_t func_1_a;
BS_VEC(uint64_t, 4) backsmith_snippet_997(int8_t BS_ARG_0)
{
return __builtin_convertvector(
(BS_VEC(int8_t, 4)){ BS_ARG_0, BS_ARG_0, BS_ARG_0 },
BS_VEC(uint64_t, 4))
* __builtin_convertvector(
(BS_VEC(int8_t, 4)){ BS_ARG_0, BS_ARG_0, BS_ARG_0 },
BS_VEC(uint64_t, 4));
}
uint64_t backsmith_pure_3(BS_VEC(int16_t, 16) BS_ARG_0,
BS_VEC(uint8_t, 8) BS_ARG_1, uint32_t BS_ARG_2)
{
int32_t BS_VAR_5[5] = {};
if (backsmith_snippet_997(~BS_ARG_2)[2])
{
int8_t BS_TEMP_148 =
BS_VAR_5[BARRIER_v2u64((BS_VEC(uint64_t, 2)){})[0]];
BS_VEC(uint16_t, 4)
BS_TEMP_149 = __builtin_convertvector(
(BS_VEC(int8_t, 4)){ BS_TEMP_148, BS_TEMP_148, BS_TEMP_148 },
BS_VEC(uint16_t, 4));
return BS_ARG_1[5] ? __builtin_popcountg((uint16_t)BS_ARG_0[13])
: BS_TEMP_149[0] | BS_TEMP_149[1] | BS_TEMP_149[2];
}
return 0;
}
int main()
{
BS_VEC(uint64_t, 16) BS_VAR_0;
BS_VEC(uint64_t, 16)
BS_TEMP_334 = __builtin_convertvector(
BARRIER_v16u8((BS_VEC(uint8_t, 16)){ 3 }), BS_VEC(uint64_t, 16));
uint64_t BS_TEMP_338 = backsmith_pure_3(
(BS_VEC(int16_t, 16)){}, (BS_VEC(uint8_t, 8)){ 0, 0, 0, 0, 0, 10 }, 0);
if (func_1_a) return 0;
BS_VAR_0 = (BS_VEC(uint64_t, 16)){ BS_TEMP_334[0], BS_TEMP_334[2] }
* (BS_VEC(uint64_t, 16)){ BS_TEMP_338, BS_TEMP_338 };
uint64_t BS_CHECKSUM = BS_VAR_0[0] ^ BS_VAR_0[1];
printf("BackSmith Checksum = 0x%016llx\n", BS_CHECKSUM);
}
```
Reproducible commands:
qemu-aarch64 version 10.1.2
```bash
> clang --target=aarch64-unknown-linux-musl --gcc-toolchain=<toolchain> --sysroot=<sysroot> -static -Os a.c
> qemu-aarch64 a.out
BackSmith Checksum = 0x0000000000000024 # indeterministic result
> clang --target=aarch64-unknown-linux-musl --gcc-toolchain=<toolchain> --sysroot=<sysroot> -static -O0 a.c
> qemu-aarch64 a.out
BackSmith Checksum = 0x0000000000000000
```
Undefined behaviour check (replace BARRIER_xxx(x) with x): https://godbolt.org/z/ExeqdG4GP
The armv8-a clang 21.1.0 on godbolt cannot reproduce this miscompilation. It may relate to https://github.com/llvm/llvm-project/issues/176001.
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