https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110963
Bug ID: 110963
Summary: [14 Regression] Dead Code Elimination Regression since
r14-2946-g46c8c225455
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/devdMf1qd
Given the following code:
void foo(void);
static int c = 76, f, g;
static int *h, *j, *k = &g;
static int **i = &h;
static short a;
static char(l)(char b) {
if (!(((b) >= 77) && ((b) <= 77))) {
__builtin_unreachable();
}
return 0;
}
static short(m)(short d, short e) { return d + e; }
static short n(char) {
j = *i;
if (j == 0)
;
else
*i = 0;
*k = 0;
return 0;
}
static char o() {
l(0);
return 0;
}
static char p(int ad) {
a = m(!0, ad);
l(a);
if (f) {
*i &&n(o());
*i = 0;
} else
n(0);
if (h == &f || h == 0)
;
else
foo();
return 0;
}
int main() {
p(c);
c = 8;
}
gcc-trunk -O3 does not eliminate the call to foo:
main:
movl f(%rip), %edi
testl %edi, %edi
je .L11
.L7:
movl $8, c(%rip)
xorl %eax, %eax
ret
.L11:
cmpq $0, h(%rip)
je .L4
xorl %esi, %esi
movq %rsi, h(%rip)
.L4:
movq h(%rip), %rax
xorl %ecx, %ecx
movl %ecx, g(%rip)
testq %rax, %rax
je .L7
cmpq $f, %rax
je .L7
pushq %rax
call foo
xorl %eax, %eax
movl $8, c(%rip)
popq %rdx
ret
gcc-13.2.0 -O3 eliminates the call to foo:
main:
movl f(%rip), %ecx
movq h(%rip), %rax
testl %ecx, %ecx
jne .L3
testq %rax, %rax
je .L4
xorl %edx, %edx
movq %rdx, h(%rip)
.L4:
xorl %eax, %eax
movl %eax, g(%rip)
.L3:
movl $8, c(%rip)
xorl %eax, %eax
ret
Bisects to r14-2946-g46c8c225455
