https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108360
Bug ID: 108360
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 54235
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54235&action=edit
case.c as file
cat case.c #321
static short b, c;
unsigned char e;
char f;
void foo();
short(a)(short h, short i) { return h + i; }
static short(d)(short h, int i) { return h >= 32 || h > 7 >> i ? h : h << i; }
unsigned g(short h, short i) { return h + i; }
int main() {
short j, k = -1;
c = a(0 >= b, k);
f = c <= 0xD315BEF1;
e = f << 4;
j = d(e, 5);
if (3 >= g(j == b, k))
foo();
b = 0;
}
`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:
.LFB3:
.cfi_startproc
movw b(%rip), %cx
xorl %edx, %edx
testw %cx, %cx
setle %dl
movl %edx, %eax
movb %dl, f(%rip)
sall $4, %eax
movb %al, e(%rip)
movzbl %al, %eax
testw %dx, %dx
jne .L4
sall $5, %eax
.L4:
cmpw %ax, %cx
jne .L7
pushq %rax
.cfi_def_cfa_offset 16
xorl %eax, %eax
call foo
xorl %eax, %eax
movw $0, b(%rip)
popq %rdx
.cfi_def_cfa_offset 8
ret
.L7:
movw $0, b(%rip)
xorl %eax, %eax
ret
---------- END OUTPUT ---------
`gcc-releases/gcc-12.2.0 -Os -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB3:
.cfi_startproc
xorl %eax, %eax
cmpw $0, b(%rip)
movw $0, b(%rip)
setle %al
movb %al, f(%rip)
sall $4, %eax
movb %al, e(%rip)
xorl %eax, %eax
ret
---------- END OUTPUT ---------
Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=418b71c0d535bf91df78bad2e198c57934682eaa
