https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110991
Bug ID: 110991
Summary: [14 Regression] Dead Code Elimination Regression at
-O2 since r14-1135-gc53f51005de
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: scherrer.sv at gmail dot com
Target Milestone: ---
static unsigned char a;
static char b;
void foo(void);
int main() {
a = 25;
for (; a > 13; --a)
b = a > 127 ?: a << 3;
if (!b)
foo();
}
gcc-3a13884b23a (trunk) -O2 cannot eliminate the call to foo but
gcc-releases/gcc-13.1.0 -O2 can.
-----------------------------------------------------------------------
gcc-3a13884b23ae32b43d56d68a9c6bd4ce53d60017 -O2 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB0:
.cfi_startproc
movd .LC0(%rip), %xmm0
movd .LC1(%rip), %xmm1
xorl %eax, %eax
.L2:
addl $1, %eax
movdqa %xmm0, %xmm2
paddb %xmm1, %xmm0
cmpl $3, %eax
jne .L2
movdqa %xmm2, %xmm0
movb $13, a(%rip)
paddb %xmm2, %xmm0
paddb %xmm0, %xmm0
movdqa %xmm0, %xmm1
paddb %xmm0, %xmm1
pxor %xmm0, %xmm0
pcmpgtb %xmm2, %xmm0
movd .LC2(%rip), %xmm2
pand %xmm0, %xmm2
pandn %xmm1, %xmm0
por %xmm2, %xmm0
movd %xmm0, %eax
sarl $24, %eax
movb %al, b(%rip)
testb %al, %al
je .L10
xorl %eax, %eax
ret
.L10:
pushq %rax
.cfi_def_cfa_offset 16
call foo
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
-----------------------------------------------------------------------
gcc-2b98cc24d6af0432a74f6dad1c722ce21c1f7458 -O2 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB0:
.cfi_startproc
movb $112, b(%rip)
xorl %eax, %eax
movb $13, a(%rip)
ret
---------- END OUTPUT ---------
-----------------------------------------------------------------------
Bisects to r14-1135-gc53f51005de
