https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110918
Bug ID: 110918
Summary: [14 Regression] Dead Code Elimination Regression at
-O3 since r14-2331-g018e7f16408
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: scherrer.sv at gmail dot com
Target Milestone: ---
static char b = 53;
static unsigned c;
void foo(void);
static int(a)(int d, int e) { return (d ^ e) < 0 ? d : d - e; }
int main() {
{
int f = 2;
c = b;
b = 0;
for (; c <= 6;) {
if (f >= 2)
f = 0;
for (; f >= -9; f = a(f, 8))
if (!(f >= -8 && f <= 0))
foo();
}
}
}
gcc-87b0749cfb9 (trunk) -O3 cannot eliminate the call to foo but
gcc-releases/gcc-13.1.0 -O3 can.
-----------------------------------------------------------------------
gcc-87b0749cfb9406790b108208b466cf507ae3c431 -O3 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
movsbl b(%rip), %eax
pushq %rbx
.cfi_def_cfa_offset 16
.cfi_offset 3, -16
xorl %ebx, %ebx
movb $0, b(%rip)
movl %eax, c(%rip)
cmpl $6, %eax
ja .L11
.p2align 4,,10
.p2align 3
.L2:
leal 8(%rbx), %eax
cmpl $8, %eax
ja .L16
.L3:
cmpl $-8, %ebx
je .L5
cmpl $-1, %ebx
jl .L6
movl $-8, %ebx
leal 8(%rbx), %eax
cmpl $8, %eax
jbe .L3
.L16:
call foo
subl $8, %ebx
jmp .L2
.L5:
jmp .L5
.p2align 4,,10
.p2align 3
.L6:
cmpl $6, c(%rip)
ja .L11
.L8:
jmp .L8
.p2align 4,,10
.p2align 3
.L11:
xorl %eax, %eax
popq %rbx
.cfi_def_cfa_offset 8
ret
---------- END OUTPUT ---------
-----------------------------------------------------------------------
gcc-2b98cc24d6af0432a74f6dad1c722ce21c1f7458 -O3 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
movsbl b(%rip), %edx
xorl %eax, %eax
movb $0, b(%rip)
movl %edx, c(%rip)
cmpl $6, %edx
ja .L8
.p2align 4,,10
.p2align 3
.L2:
testl %eax, %eax
js .L3
subl $8, %eax
cmpl $-9, %eax
jge .L2
cmpl $6, c(%rip)
ja .L8
.L6:
jmp .L6
.L3:
jmp .L3
.p2align 4,,10
.p2align 3
.L8:
xorl %eax, %eax
ret
---------- END OUTPUT ---------
-----------------------------------------------------------------------
Bisects to r14-2331-g018e7f16408
