| Issue |
172824
|
| Summary |
Wrong code at -O1/O2 possbily due to backend bug since clang 21.1.0
|
| Labels |
miscompilation
|
| Assignees |
|
| Reporter |
XChy
|
Reproducer: https://godbolt.org/z/bGEMsr81M
I inspected the IR produced by `opt`, and it looks correct to me. And I can reproduce it on X86, AArch64, and RISC-V. I suspect it's the problem of the generic codegen.
Testcase:
```c
#include <stdint.h>
#include <stdio.h>
#define BS_VEC(type, num) type __attribute__((vector_size(num * sizeof(type))))
uint64_t BS_CHECKSUM;
BS_VEC(int8_t, 32)
backsmith_snippet_1116(BS_VEC(uint8_t, 32), uint16_t, BS_VEC(int64_t, 8))
{}
static int32_t g_3, g_169;
int func_1_BS_COND_4;
int func_1_BS_COND_9;
static uint32_t func_1()
{
uint64_t LOCAL_CHECKSUM = 0;
BS_LABEL_6:
for (; g_3;)
{
int32_t l_1874[1][1][3];
int i, j, k;
l_1874[i][j][k] = 1;
for (; 0; g_169)
if (0)
{
for (uint32_t BS_TEMP_34; BS_TEMP_34; BS_TEMP_34++)
{
LOCAL_CHECKSUM ^= 9;
BS_LABEL_4:
}
__builtin_convertvector(
__builtin_shufflevector(
backsmith_snippet_1116((BS_VEC(uint8_t, 32)){}, 0,
(BS_VEC(int64_t, 8)){}),
backsmith_snippet_1116((BS_VEC(uint8_t, 32)){}, 0,
(BS_VEC(int64_t, 8)){}),
0, 7, 3, 3, 3, 1, 3, 6),
BS_VEC(uint32_t, 8));
__asm goto("" : : : : BS_LABEL_6);
}
else
BS_LABEL_7:
if (l_1874[0][0][1]) break;
}
if (func_1_BS_COND_4) goto BS_LABEL_7;
switch (func_1_BS_COND_9)
case 2064568:
goto BS_LABEL_4;
BS_CHECKSUM += LOCAL_CHECKSUM;
return 0;
}
int main()
{
func_1();
printf("BackSmith Checksum = 0x%016llx\n", BS_CHECKSUM);
}
```
Commands:
```bash
> clang -O0 a.c && a.out
BackSmith Checksum = 0x0000000000000000
> clang -O1 a.c && a.out
BackSmith Checksum = 0x00007ffe970f5af8
```
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