https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108707
Bug ID: 108707
Summary: suboptimal allocation with same memory op for many
different instructions.
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: crazylht at gmail dot com
Target Milestone: ---
#include<immintrin.h>
void
foo (__m512* pv, float* __restrict ps, int n, __m512* pdest,
__m512* p1, __m512* p2, __m512* p3)
{
__m512 a = _mm512_setzero_ps ();
__m512 b = a;
__m512 c = a;
for (int i = 0; i != n ;i++)
{
a = _mm512_fmadd_ps (p1[i], pv[i], a);
b = _mm512_fmadd_ps (p2[i], pv[i], b);
c = _mm512_fmadd_ps (p3[i], pv[i], c);
}
pdest[0] = a;
pdest[1] = b;
pdest[2] = c;
}
g++ -O2 -mavx512f -S
got
.L3:
vmovaps (%r8,%rax), %zmm3
vmovaps (%r9,%rax), %zmm4
vmovaps (%rsi,%rax), %zmm5
vfmadd231ps (%rdi,%rax), %zmm3, %zmm2
vfmadd231ps (%rdi,%rax), %zmm4, %zmm1
vfmadd231ps (%rdi,%rax), %zmm5, %zmm0
addq $64, %rax
cmpq %rax, %rdx
jne .L3
It would be better to load (%rdi, %rax) into a zmm then
.L3:
vmovaps (%rdi,%rax), %zmm0
vfmadd231ps (%r8,%rax), %zmm0, %zmm3
vfmadd231ps (%r9,%rax), %zmm0, %zmm2
vfmadd231ps (%rsi,%rax), %zmm0, %zmm1
addq $64, %rax
cmpq %rax, %rdx
jne .L3
