https://bugs.llvm.org/show_bug.cgi?id=42538
Bug ID: 42538
Summary: vzeroupper elimination
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: Backend: X86
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
#include <immintrin.h>
Since GCC 9+, GCC can eliminate vzeroupper in various cases, e.g.:
long long get_elem2(__m256i v) {
return v[2];
}
Clang -O3 -march=skylake-avx512
get_elem2:
vextracti128 xmm0, ymm0, 1
vmovq rax, xmm0
vzeroupper
ret
GCC -O3 -march=skylake-avx512
get_elem2:
vextracti64x2 xmm0, ymm0, 0x1
vmovq rax, xmm0
ret
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