https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107546
Bug ID: 107546 Summary: simd, redundant pcmpeqb and pxor Product: gcc Version: 12.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization Assignee: unassigned at gcc dot gnu.org Reporter: i.nixman at autistici dot org Target Milestone: --- Hello, this code sample(https://godbolt.org/z/TnGMsfMs6): ``` #include <x86intrin.h> auto foo(const char *p) { const auto substr = _mm_loadu_si128((const __m128i *)p); return _mm_cmplt_epi8(substr, _mm_set1_epi8('0')); } ``` produces the following ASM code: ``` 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 ``` please look at line 5. is there any reason for `pcmpeqb` and `pxor` instruction? 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 ``` it looks like the issue started at version 9 and up to the current trunk.