https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111449
Bug ID: 111449
Summary: memcmp (p,q,16) == 0 can be optimized better on ppc64
with vector comparison instructions
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: guihaoc at gcc dot gnu.org
Target Milestone: ---
int compare (const char* s1, const char* s2)
{
return __builtin_memcmp (s1, s2, 16) == 0;
}
trunk outputs
ld 10,0(3)
ld 9,0(4)
cmpd 0,10,9
beq 0,.L6
.L2:
li 3,1
cntlzw 3,3
srwi 3,3,5
blr
.p2align 4,,15
.L6:
ld 10,8(3)
ld 9,8(4)
li 3,0
cmpd 0,10,9
bne 0,.L2
cntlzw 3,3
srwi 3,3,5
blr
Expect to use vector comparison to eliminate branches.
lxv 32,0(3)
lxv 33,0(4)
vcmpequb. 0,0,1
mfcr 3,2
rlwinm 3,3,25,1
blr
