https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110768
Bug ID: 110768
Summary: [14 Regression] Dead Code Elimination Regression since
r14-2623-gc11a3aedec2
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: theodort at inf dot ethz.ch
Target Milestone: ---
https://godbolt.org/z/GsTMz1G9c
Given the following code:
void foo(void);
static int a, b;
int main() {
{
short c = 45127;
char d;
b = 0;
for (; b <= 3; b++) {
if (b) continue;
d = 0;
for (; d <= 3; d++) {
if (!(((c) >= -20409) && ((c) <= 1))) {
__builtin_unreachable();
}
if (~(0 == a) & 1) return b;
c = 0;
for (; c <= 0; c++) a = 3;
}
}
foo();
}
}
gcc-trunk -Os does not eliminate the call to foo:
main:
xorl %r9d, %r9d
movl a(%rip), %eax
xorl %edx, %edx
xorl %esi, %esi
movl %r9d, b(%rip)
xorl %ecx, %ecx
.L2:
cmpl $4, %edx
je .L31
testl %edx, %edx
jne .L3
testl %eax, %eax
je .L4
.L24:
testb %sil, %sil
je .L5
xorl %r8d, %r8d
movl %r8d, b(%rip)
.L5:
testb %cl, %cl
je .L27
movl %eax, a(%rip)
jmp .L27
.L4:
movl $3, %eax
movb $1, %cl
jmp .L24
.L3:
incl %edx
movb $1, %sil
jmp .L2
.L31:
pushq %rdi
testb %sil, %sil
je .L9
movl $4, b(%rip)
.L9:
testb %cl, %cl
je .L10
movl %eax, a(%rip)
.L10:
call foo
xorl %eax, %eax
popq %rdx
ret
.L27:
xorl %eax, %eax
ret
gcc-13.1.0 -Os eliminates the call to foo:
main:
xorl %eax, %eax
cmpl $0, a(%rip)
movl %eax, b(%rip)
jne .L2
movl $3, a(%rip)
.L2:
xorl %eax, %eax
ret
Bisects to r14-2623-gc11a3aedec2
