https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110413
Bug ID: 110413
Summary: [14 Regression] Missed Dead Code Elimination when
using __builtin_unreachable since
r14-1880-g827e208fa64
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/75vvarEvs
Given the following code:
void foo(void);
static int a, b, d, e, g, h;
static short f;
static int *i, *k;
static int **l = &i;
void __assert_fail(char *, char *, int, char *) __attribute__((__noreturn__));
static int(c)() { return a + b; }
static int *j() {
f | e & 4073709551611 && c();
return &d;
}
int main() {
*l = j();
h = 5;
for (; h; h--) {
k = j();
if (k && k <= &d)
;
else {
__builtin_unreachable();
__assert_fail("", "", 0, __PRETTY_FUNCTION__);
}
}
if (k || k == &g)
;
else
foo();
;
}
gcc-trunk -O1 does not eliminate the call to foo:
j:
movl $d, %eax
ret
main:
subq $8, %rsp
movl $0, %eax
call j
movq %rax, i(%rip)
movq %rax, k(%rip)
movl $0, h(%rip)
cmpq $g, %rax
je .L3
testq %rax, %rax
je .L5
.L3:
movl $0, %eax
addq $8, %rsp
ret
.L5:
call foo
jmp .L3
gcc-13.1.0 -O1 eliminates the call to foo:
j:
movl $d, %eax
ret
main:
movl $0, %eax
call j
movq %rax, i(%rip)
movq %rax, k(%rip)
movl $0, h(%rip)
movl $0, %eax
ret
Bisects to r14-1880-g827e208fa64
