https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111326
Bug ID: 111326
Summary: [14 Regression] Dead Code Elimination Regression since
r14-376-g47a76439911
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/fv3szWMTE
Given the following code:
void foo(void);
static int a = 253, d, e, f, h, i, k;
static char j, m;
static short l, n;
static char(o)(char b, char c) { return b + c; }
void(p)(int);
short(q)(short);
static short(r)(int g) {
if (!(((g) >= 253) && ((g) <= 253))) {
__builtin_unreachable();
}
return 0;
}
static void s(char ab, short) {
int ac;
ab = 27;
for (; ab > 13; ab = ab - 9) {
j |= 10 | ac;
e = 0;
if (o(ab ^ a, d)) {
--l;
f = 0;
if (a)
;
else {
p(i);
k ^= q(0);
}
i = 5;
} else {
ac = 0;
for (; ac <= 38; ac = ac + 5) foo();
k = h &= 0 >= 0;
n = 0;
}
}
}
static unsigned t() {
s(m, a);
if (l)
;
else
r(3);
return f;
}
int main() {
d = a;
t();
r(a);
printf("", e, n);
}
gcc-trunk -O3 does not eliminate the call to foo:
main:
pushq %rbp
movl $253, %edx
movl $27, %ebp
pushq %rbx
subq $8, %rsp
movl $253, d(%rip)
.L5:
movl %ebp, %eax
orb $42, j(%rip)
movl $0, e(%rip)
xorl $-3, %eax
addb %dl, %al
je .L6
subw $1, l(%rip)
movl $0, f(%rip)
movl $5, i(%rip)
.L3:
cmpb $18, %bpl
je .L4
movl d(%rip), %edx
movl $18, %ebp
jmp .L5
.p2align 4,,10
.p2align 3
.L4:
movswl n(%rip), %edx
movl e(%rip), %esi
movl $.LC0, %edi
xorl %eax, %eax
call printf
addq $8, %rsp
xorl %eax, %eax
popq %rbx
popq %rbp
ret
.L6:
movl $8, %ebx
.L2:
call foo
call foo
subl $2, %ebx
jne .L2
movw $0, n(%rip)
movl h(%rip), %eax
andl $1, %eax
movl %eax, h(%rip)
movl %eax, k(%rip)
jmp .L3
gcc-13.2.0 -O3 eliminates the call to foo:
main:
subq $8, %rsp
movswl n(%rip), %edx
xorl %esi, %esi
xorl %eax, %eax
movl $.LC0, %edi
orb $42, j(%rip)
subw $2, l(%rip)
movl $253, d(%rip)
movl $0, e(%rip)
movl $0, f(%rip)
movl $5, i(%rip)
call printf
xorl %eax, %eax
addq $8, %rsp
ret
Bisects to r14-376-g47a76439911
