https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110539
Bug ID: 110539
Summary: [14 Regression] Dead Code Elimination Regression at
since r14-338-g1dd154f6407
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/h9vrrj5je
Given the following code:
void foo(void);
static int a, c = 1;
static short b;
static int *d = &c, *e = &a;
static int **f = &d;
void __assert_fail() __attribute__((__noreturn__));
static void g(short h) {
if (*d)
;
else {
if (e) __assert_fail();
if (a) {
__builtin_unreachable();
} else
__assert_fail();
}
if ((((0, 0) || h) == h) + b) *f = 0;
}
int main() {
int i = 0 != 10 & a;
g(i);
*e = 9;
e = 0;
if (d == 0)
;
else
foo();
;
}
gcc-trunk -O2 does not eliminate the call to foo:
main:
subq $8, %rsp
movq d(%rip), %rax
movq e(%rip), %rdx
movl (%rax), %edi
testl %edi, %edi
jne .L2
xorl %eax, %eax
call __assert_fail
.L2:
xorl %ecx, %ecx
xorl %esi, %esi
movq %rcx, d(%rip)
cmpq $0, d(%rip)
movl $9, (%rdx)
movq %rsi, e(%rip)
je .L3
call foo
.L3:
xorl %eax, %eax
popq %rdx
ret
gcc-13.1.0 -O2 eliminates the call to foo:
main:
movq d(%rip), %rax
movq e(%rip), %rdx
movl (%rax), %esi
testl %esi, %esi
jne .L2
pushq %rcx
xorl %eax, %eax
call __assert_fail
.L2:
xorl %eax, %eax
movq %rax, d(%rip)
xorl %eax, %eax
movl $9, (%rdx)
xorl %edx, %edx
movq %rdx, e(%rip)
ret
Bisects to r14-338-g1dd154f6407
