https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101991
Bug ID: 101991
Summary: bit_and or bit_ior with an invariant inside loop is
not pulled out of the loop
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take these two functions:
int f(int t, int d, int e)
{
int r = d;
for(int i = 0; i < t; i++)
r &= e;
return r;
}
int f1(int t, int d, int e)
{
int r = d;
if (0 < t)
r &= e;
return r;
}
They should produce the same code. Right now f still has a loop in it.
The same is true with bit_ior.
Note the code is really bad when the vectorizer comes around really.
I forgot how I found this either.
Note clang/ICC also vectorize this code crappily.
clang on the trunk almost gets there but still has a loop:
movl %esi, %eax
xorl %esi, %esi
testl %edi, %edi
cmovgl %edi, %esi
jle .LBB0_6
# %bb.1:
leal -1(%rsi), %edi
movl %esi, %ecx
andl $7, %ecx
cmpl $7, %edi
jb .LBB0_4
# %bb.2:
andl $-8, %esi
negl %esi
.p2align 4, 0x90
.LBB0_3: # =>This Inner Loop Header: Depth=1
addl $8, %esi
jne .LBB0_3
.LBB0_4:
andl %edx, %eax
testl %ecx, %ecx
je .LBB0_6
.p2align 4, 0x90
.LBB0_5: # =>This Inner Loop Header: Depth=1
addl $-1, %ecx
jne .LBB0_5
.LBB0_6:
retq
