On 2022-11-07 03:32, Hongtao Liu wrote:
On Sun, Nov 6, 2022 at 6:54 PM i.nixman--- via Gcc-help
<gcc-help@xxxxxxxxxxx> wrote:
Hello,
look at this example(https://godbolt.org/z/TnGMsfMs6):
```
auto foo(const char *p) {
const auto substr = _mm_loadu_si128((const __m128i *)p);
return _mm_cmplt_epi8(substr, _mm_set1_epi8('0'));
}
```
and to the generated asm:
```
1: foo(char const*):
2: movdqu xmm0, XMMWORD PTR [rdi]
3: pxor xmm1, xmm1
4: pcmpgtb xmm0, XMMWORD PTR .LC0[rip]
5: pcmpeqb xmm0, xmm1
6: ret
```
look at line 5.
is there any reason for `pcmpeqb` instruction?
hi,
Looks like a mis optimization from
_4 = VIEW_CONVERT_EXPR<__v16qs>(_7);
_3 = _4 <= { 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
47, 47 };
_5 = VIEW_CONVERT_EXPR<vector(16) signed char>(_3); --- this?
Could you open a bugzilla for it
https://gcc.gnu.org/bugzilla/
sure, but for which component?
just for info, clang's output(https://godbolt.org/z/MPnvEMdhr):
```
1: foo(char const*):
2: movdqu xmm1, xmmword ptr [rdi]
3: movdqa xmm0, xmmword ptr [rip + .LCPI0_0]
4: pcmpgtb xmm0, xmm1
5: ret
```
best!
