https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108354
Bug ID: 108354
Summary: Dead Code Elimination Regression at -O2 (trunk vs.
12.2.0)
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: yann at ywg dot ch
Target Milestone: ---
Created attachment 54229
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54229&action=edit
presented code as file
cat case.c #617
int b;
int *c;
int e;
static int *f = &e;
int g;
void foo();
short(a)(short h, short i) { return h - i; }
int(d)(int h) { return h == 83647 ? 0 : -h; }
int main() {
short j;
int *k = &e, *l = &b;
*f = 0 == c;
j = a(0 != 2, *k);
if (d(j ^ (0 == l || *k)) != *k)
;
else
foo();
c = &g;
}
`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -O2` can not eliminate
`foo` but `gcc-releases/gcc-12.2.0 -O2` can.
`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -O2 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB2:
.cfi_startproc
xorl %eax, %eax
cmpq $0, c(%rip)
setne %dl
sete %al
movzbl %dl, %edx
movl %eax, e(%rip)
orl %eax, %edx
je .L12
movq $g, c(%rip)
xorl %eax, %eax
ret
.L12:
pushq %rax
.cfi_def_cfa_offset 16
xorl %eax, %eax
call foo
xorl %eax, %eax
movq $g, c(%rip)
popq %rdx
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
`gcc-releases/gcc-12.2.0 -O2 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB2:
.cfi_startproc
xorl %eax, %eax
cmpq $0, c(%rip)
movq $g, c(%rip)
sete %al
movl %eax, e(%rip)
xorl %eax, %eax
ret
---------- END OUTPUT ---------
Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b3e98eb3396e16ae8b20c94916bc2bd7862d2c97
