https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94962
Bug ID: 94962
Summary: Suboptimal AVX2 code for
_mm256_zextsi128_si256(_mm_set1_epi8(-1))
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: n...@self-evident.org
Target Milestone: ---
Background: https://stackoverflow.com/q/61601902/
GCC emits an unnecessary "vmovdqa xmm0,xmm0" for the following code:
__m256i mask()
{
return _mm256_zextsi128_si256(_mm_set1_epi8(-1));
}
Live example on godbolt: https://gcc.godbolt.org/z/PbsQDR
I have found no way to avoid this except by resorting to inline asm.
