https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105833
Bug ID: 105833
Summary: Dead Code Elimination Regression at -O2 (trunk vs.
12.1.0)
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: theodort at inf dot ethz.ch
Target Milestone: ---
cat case.c #4
void foo();
static int b;
static int **c;
static int ***d = &c;
static int ****e = &d;
static char(a)(char g, int h) { return h >= 2 ? g : g << h; }
int main() {
**e == 0;
b = b ? 4 : 0;
if (!a(*e != 0, b))
foo();
}
`gcc-1982fe2692b6c3b7f969ffc4edac59f9d4359e91 (trunk) -O2` can not eliminate
`foo` but `gcc-releases/gcc-12.1.0 -O2` can.
`gcc-1982fe2692b6c3b7f969ffc4edac59f9d4359e91 (trunk) -O2 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
movl b(%rip), %ecx
xorl %eax, %eax
testl %ecx, %ecx
setne %al
sall $2, %eax
cmpq $0, d(%rip)
movl %eax, b(%rip)
je .L8
xorl %eax, %eax
ret
.L8:
pushq %rax
.cfi_def_cfa_offset 16
xorl %eax, %eax
call foo
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
`gcc-releases/gcc-12.1.0 -O2 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
movl b(%rip), %edx
xorl %eax, %eax
testl %edx, %edx
setne %al
sall $2, %eax
movl %eax, b(%rip)
xorl %eax, %eax
ret
---------- END OUTPUT ---------
Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b7501739f3b14ac7749aace93f636d021fd607f7
