https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108358
Bug ID: 108358
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 54233
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54233&action=edit
presented code as file
cat case.c #25
struct a {
int b;
int c;
short d;
int e;
int f;
};
struct g {
struct a f;
struct a h;
};
int i;
void foo();
void bar31_(void);
int main() {
struct g j, l = {2, 1, 6, 1, 1, 7, 5, 1, 0, 1};
for (; i; ++i)
bar31_();
j = l;
struct g m = j;
struct g k = m;
if (k.h.b)
;
else
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:
.LFB0:
.cfi_startproc
pushq %rbx
.cfi_def_cfa_offset 16
.cfi_offset 3, -16
movl $.LC0, %esi
movl $10, %ecx
subq $80, %rsp
.cfi_def_cfa_offset 96
leaq 40(%rsp), %rdi
leaq 40(%rsp), %rbx
rep movsl
.L2:
cmpl $0, i(%rip)
je .L7
call bar31_
incl i(%rip)
jmp .L2
.L7:
movq %rsp, %rdi
movl $10, %ecx
movq %rbx, %rsi
rep movsl
cmpl $0, 20(%rsp)
jne .L4
xorl %eax, %eax
call foo
.L4:
addq $80, %rsp
.cfi_def_cfa_offset 16
xorl %eax, %eax
popq %rbx
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
`gcc-releases/gcc-12.2.0 -Os -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB0:
.cfi_startproc
cmpl $0, i(%rip)
jne .L7
xorl %eax, %eax
ret
.L7:
pushq %rax
.cfi_def_cfa_offset 16
.L3:
call bar31_
incl i(%rip)
cmpl $0, i(%rip)
jne .L3
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=f6c168f8c06047bfaa3005e570126831b8855dcc
