https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111293
Bug ID: 111293
Summary: [14 Regression] Missed Dead Code Elimination since
r14-3414-g0cfc9c953d0
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/9aj7sr5d6
Given the following code:
void foo(void);
static int a, d;
static short e;
static int(f)(int b, int c) { return c == 0 ? b : b / c; }
static char g(char h) {
char i = 1;
int j = 8;
e = 3;
for (; d; ++d) {
if (f(0 == j, e)) return a;
for (; i; i--) {
if (j) {
if (e)
;
else if (a)
continue;
else
foo();
j = -h;
break;
}
__builtin_unreachable();
break;
}
}
return 1;
}
int main() {
g(-1);
a = e;
}
gcc-trunk -O2 does not eliminate the call to foo:
main:
subq $8, %rsp
movl d(%rip), %ecx
movl $3, %edx
movw %dx, e(%rip)
testl %ecx, %ecx
je .L6
movl $3, %edx
.p2align 4,,10
.p2align 3
.L2:
testw %dx, %dx
jne .L3
movl a(%rip), %eax
testl %eax, %eax
je .L18
.L5:
addl $1, d(%rip)
jne .L5
.L6:
movswl e(%rip), %eax
movl %eax, a(%rip)
xorl %eax, %eax
addq $8, %rsp
ret
.p2align 4,,10
.p2align 3
.L18:
call foo
.L3:
addl $1, d(%rip)
movzwl e(%rip), %edx
jne .L2
jmp .L6
gcc-13.2.0 -O2 eliminates the call to foo:
main:
movl d(%rip), %edx
movl $3, %eax
movw %ax, e(%rip)
testl %edx, %edx
je .L3
movl $0, d(%rip)
.L3:
movl $3, a(%rip)
xorl %eax, %eax
ret
Bisects to r14-3414-g0cfc9c953d0
