https://bugs.llvm.org/show_bug.cgi?id=42653
Bug ID: 42653
Summary: [X86][AVX] Rematerializable lower 'allones' subvector
masks
Product: libraries
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: llvm-...@redking.me.uk
CC: craig.top...@gmail.com, llvm-bugs@lists.llvm.org,
llvm-...@redking.me.uk, spatel+l...@rotateright.com
https://gcc.godbolt.org/z/ESwT78
We should be able to rematerialize masks where the lower subvector half is -1
and the upper 0 by using a smaller destination and the implicit zeroing of the
upper bits:
#include <x86intrin.h>
__m128i low128_128() {
// GOOD
return _mm_setr_epi32(-1,-1,-1,-1);
}
__m256i low256_128() {
// BAD: vpcmpeqd %xmm0, %xmm0, %xmm0
return _mm256_setr_epi32(-1,-1,-1,-1,0,0,0,0);
}
__m512i low512_128() {
// BAD: vpcmpeqd %xmm0, %xmm0, %xmm0
return _mm512_setr_epi32(-1,-1,-1,-1,0,0,0,0,0,0,0,0,0,0,0,0);
}
__m512i low512_256() {
// BAD: vpcmpeqd %ymm0, %ymm0, %ymm0
return _mm512_setr_epi32(-1,-1,-1,-1,-1,-1,-1,-1,0,0,0,0,0,0,0,0);
}
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