https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126732
Bug ID: 126732
Summary: Redundant scalar check after vectorized operation
Product: gcc
Version: 16.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: blubban at gmail dot com
Target Milestone: ---
bool x(int* y)
{
for (int i=0;i<8;i++)
{
if (y[i] == 42)
return true;
}
return false;
}
-mavx2 -O3
Result:
"x(int*)":
test dil, 31
jne .L2
mov eax, 42
vmovd xmm0, eax
xor eax, eax
vpbroadcastd ymm0, xmm0
vpcmpeqd ymm0, ymm0, YMMWORD PTR [rdi]
vptest ymm0, ymm0
jne .L16
vzeroupper
ret
.L16:
cmp DWORD PTR [rdi], 42
je .L14
cmp DWORD PTR [rdi+4], 42
je .L14
cmp DWORD PTR [rdi+8], 42
je .L14
cmp DWORD PTR [rdi+12], 42
je .L14
cmp DWORD PTR [rdi+16], 42
je .L14
cmp DWORD PTR [rdi+20], 42
je .L14
cmp DWORD PTR [rdi+24], 42
je .L14
cmp DWORD PTR [rdi+28], 42
sete al
vzeroupper
ret
.L14:
vzeroupper
.L4:
mov eax, 1
ret
.L2:
cmp DWORD PTR [rdi], 42
je .L4
cmp DWORD PTR [rdi+4], 42
je .L4
cmp DWORD PTR [rdi+8], 42
je .L4
cmp DWORD PTR [rdi+12], 42
je .L4
cmp DWORD PTR [rdi+16], 42
je .L4
cmp DWORD PTR [rdi+20], 42
je .L4
cmp DWORD PTR [rdi+24], 42
je .L4
cmp DWORD PTR [rdi+28], 42
sete al
ret
Expected: Reaching .L16 means at least one element is 42, so that string of
compares is known to return true and should be optimized out. (The .L2 compare
string belongs there.)
