https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85115
Bug ID: 85115
Summary: Failure to (auto)vectorize sqrtf
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: robertw89 at googlemail dot com
Target Milestone: ---
Fails to (auto)vectorize the code bellow with the flags
-O3 -mavx
#include <cmath>
void simdSqrt(
float * __restrict__ a,
float * __restrict__ res,
int size)
{
int i;
float *aAligned = (float*)__builtin_assume_aligned(a, 32);
float *resAligned = (float*)__builtin_assume_aligned(res, 32);
for (i = 0; i < size; i++) {
resAligned[i] = sqrtf(aAligned[i]);
}
}
produces (as displayed by https://godbolt.org/)
simdSqrt(float*, float*, int):
test edx, edx
jle .L8
lea eax, [rdx-1]
push r12
vxorps xmm2, xmm2, xmm2
lea r12, [rdi+4+rax*4]
sub rsp, 32
.L3:
vmovss xmm0, DWORD PTR [rdi]
vucomiss xmm2, xmm0
vsqrtss xmm1, xmm1, xmm0
ja .L12
add rdi, 4
vmovss DWORD PTR [rsi], xmm1
add rsi, 4
cmp rdi, r12
jne .L3
.L6:
add rsp, 32
pop r12
ret
.L8:
rep ret
.L12:
vmovss DWORD PTR [rsp+28], xmm2
mov QWORD PTR [rsp+16], rsi
mov QWORD PTR [rsp+8], rdi
vmovss DWORD PTR [rsp+24], xmm1
call sqrtf
mov rdi, QWORD PTR [rsp+8]
mov rsi, QWORD PTR [rsp+16]
vmovss xmm1, DWORD PTR [rsp+24]
vmovss xmm2, DWORD PTR [rsp+28]
add rdi, 4
vmovss DWORD PTR [rsi], xmm1
add rsi, 4
cmp rdi, r12
jne .L3
jmp .L6
