https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87976
Bug ID: 87976
Summary: [i386] Sub-optimal code generation for
_mm256_set1_epi64()
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: thiago at kde dot org
Target Milestone: ---
In the following code, Clang and ICC emit a very optimal function that consists
of three instructions (including the tail call). MSVC emits a pretty good
equivalent with a bit more function overhead, but no memory access
GCC emits a completely unnecessary memory access.
Code:
====
#include <immintrin.h>
#include <stdint.h>
#ifndef _MSC_VER
#define __vectorcall
#endif
void __vectorcall f(__m256i value256);
void g(uint64_t value)
{
f( _mm256_set1_epi64x(value));
}
====
Clang and ICC (optimal) output:
g:
vmovd %rdi, %xmm0
vpbroadcastq %xmm0, %ymm0
jmp f
GCC:
g:
pushq %r13
leaq 16(%rsp), %r13
andq $-32, %rsp
pushq -8(%r13)
pushq %rbp
movq %rsp, %rbp
pushq %r13
movq %rdi, -24(%rbp)
vpbroadcastq -24(%rbp), %ymm0
popq %r13
popq %rbp
leaq -16(%r13), %rsp
popq %r13
jmp f
Godbolt link for all compilers: https://gcc.godbolt.org/z/-gNvec
