https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109893
Bug ID: 109893
Summary: [14 Regression] Missed Dead Code Elimination when
using __builtin_unreachable since
r14-160-gf828503eeb79ad1f1ada6db7deccc5abcc2f3ca3
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: ---
void foo(void);
void bar(void);
static char a;
static int b, e, f;
static int *c = &b, *g;
int main() {
int *j = 0;
if (a) {
g = 0;
if (c)
bar();
} else {
j = &e;
c = 0;
}
if (c == &f == b || c == &e)
;
else
__builtin_unreachable();
if (g || e) {
if (j == &e || j == 0)
;
else
foo();
}
a = 4;
}
gcc -O3:
main:
cmpb $0, a(%rip)
je .L2
xorl %esi, %esi
cmpq $0, c(%rip)
movq %rsi, g(%rip)
je .L7
pushq %rdx
call bar
movb $4, a(%rip)
xorl %eax, %eax
popq %rcx
ret
.L2:
xorl %eax, %eax
movq %rax, c(%rip)
.L7:
movb $4, a(%rip)
xorl %eax, %eax
ret
c:
.quad b
gcc-trunk -O3
main:
subq $8, %rsp
cmpb $0, a(%rip)
je .L2
xorl %edx, %edx
cmpq $0, c(%rip)
movq %rdx, g(%rip)
je .L6
call bar
xorl %eax, %eax
.L4:
cmpq $0, g(%rip)
je .L9
.L6:
movb $4, a(%rip)
xorl %eax, %eax
addq $8, %rsp
ret
.L2:
xorl %eax, %eax
movq %rax, c(%rip)
movl $e, %eax
jmp .L4
.L9:
cmpl $0, e(%rip)
je .L6
testq %rax, %rax
je .L6
cmpq $e, %rax
je .L6
call foo
jmp .L6
c:
.quad b
Bisects to:
https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=f828503eeb79ad1f1ada6db7deccc5abcc2f3ca3
