| Issue |
181002
|
| Summary |
[AArch64] Wrong code at -O2
|
| Labels |
backend:AArch64,
miscompilation,
generated by fuzzer
|
| Assignees |
|
| Reporter |
XChy
|
Reproducer: https://godbolt.org/z/KosfxK9ff
Testcase:
```c
#include <stdint.h>
#include <stdio.h>
#include <arm_neon.h>
#define BARRIER_v2u64(x) ((BS_VEC(uint64_t, 2))vqaddq_u64(x, (BS_VEC(uint64_t, 2)){}))
#define BS_VEC(type, num) type __attribute__((vector_size(num * sizeof(type))))
#define BITCAST(T, F, arg) \
((union { \
F src; \
T dst \
})arg) \
.dst
uint64_t BS_CHECKSUM;
void backsmith_checksum_4()
{
int64_t BS_VAR_0 = 200366739780528840;
uint64_t BS_VAR_3 = 0;
int32_t BS_VAR_4 = 0;
uint8_t BS_TEMP_479 =
~BITCAST(uint16_t, BS_VEC(uint8_t, 2),
__builtin_convertvector(BARRIER_v2u64((BS_VEC(uint64_t, 2)){}),
BS_VEC(uint8_t, 2)));
for (uint8_t BS_INC_0; BS_INC_0 < BS_TEMP_479; BS_INC_0 += 1)
{
BS_VAR_3 = BS_VAR_4;
BS_VAR_4 = BS_INC_0;
BS_VAR_0 = 0;
}
BS_CHECKSUM ^= BS_VAR_0 ^= BS_VAR_3 + 9;
}
int main()
{
backsmith_checksum_4();
printf("BackSmith Checksum = 0x%016llx\n", BS_CHECKSUM);
}
```
The output at -O1:
```
BackSmith Checksum = 0x0000000000000106
```
The output at -O2:
```
BackSmith Checksum = 0x0000000000000105
```
Looks like a recent regression as clang 21.1.0 cannot reproduce it.
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