https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108359
Bug ID: 108359
Summary: Dead Code Elimination Regression at -Os (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 54234
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54234&action=edit
presented code as file
cat case.c #864
int b = 10;
int c;
char e;
void foo();
static char(a)(char f, char g) { return f && g == 1 ? 0 : f % g; }
short(d)(short f, short g) { return f * g; }
int main() {
short h;
int i;
unsigned j;
h = d(b && c, 5);
j = h;
i = a(h, 237);
unsigned k = i;
e = i < 0 || k >= 32 ? 0 : i >> k;
if (e) {
c = 0;
foo();
}
}
`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -Os` can not eliminate
`foo` but `gcc-releases/gcc-12.2.0 -Os` can.
`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -Os -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB2:
.cfi_startproc
movl b(%rip), %eax
testl %eax, %eax
je .L3
xorl %eax, %eax
cmpl $0, c(%rip)
setne %al
.L3:
movb $5, %dl
imull %edx, %eax
movsbl %al, %edx
movl %eax, %ecx
sarl %cl, %edx
movb %dl, e(%rip)
testl %edx, %edx
je .L12
pushq %rax
.cfi_def_cfa_offset 16
xorl %edx, %edx
xorl %eax, %eax
movl %edx, c(%rip)
call foo
xorl %eax, %eax
popq %rcx
.cfi_def_cfa_offset 8
ret
.L12:
xorl %eax, %eax
ret
---------- END OUTPUT ---------
`gcc-releases/gcc-12.2.0 -Os -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB2:
.cfi_startproc
movb $0, e(%rip)
xorl %eax, %eax
ret
---------- END OUTPUT ---------
Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=9991d84d2a84355fd3fc9afc89a963f45991bfa9
