https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110932
Bug ID: 110932
Summary: [14 Regression] Dead Code Elimination Regression since
r14-2230-g7e904d6c7f2
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/fs5obnhPP
Given the following code:
void foo(void);
static short a;
static int b, c, f, h, i, k;
static char d, m;
static int *j, *o = &f;
static int **l = &j, **n = &j;
static unsigned p(short g, short) { return g; }
static short(q)(unsigned e) {
if (!(((e) >= 1) && ((e) <= 65531))) {
__builtin_unreachable();
}
return 0;
}
static short r() {
q(&k != 0 | f);
*l = o;
return h;
}
static int *s() {
m = c ?: d ?: m;
b = b ?: a;
a = 0;
return *l;
}
int main() {
char t = 0;
for (; t <= 4; t = t + 2) {
int *u = &i;
if (p(~(r() <= t), *u) > i == i) {
**n = -5L;
if (*u) continue;
**n = 0;
if (t) foo();
break;
}
s();
*u = u != 0;
}
s();
h = 0;
}
gcc-trunk -O3 does not eliminate the call to foo:
main:
subq $8, %rsp
movl h(%rip), %ecx
xorl %edx, %edx
movl i(%rip), %eax
movq $f, j(%rip)
testw %cx, %cx
setle %dl
notl %edx
movswl %dx, %edx
cmpl %edx, %eax
setb %dl
movzbl %dl, %edx
cmpl %eax, %edx
jne .L22
testl %eax, %eax
jne .L23
xorl %edx, %edx
movl %edx, f(%rip)
jmp .L14
.L22:
xorl %eax, %eax
call s.isra.0
movl $1, %eax
movl $1, i(%rip)
.L6:
movq $f, j(%rip)
xorl %edx, %edx
cmpw $2, %cx
setle %dl
notl %edx
movswl %dx, %edx
cmpl %edx, %eax
setb %dl
movzbl %dl, %edx
cmpl %edx, %eax
je .L8
xorl %eax, %eax
call s.isra.0
movl $1, %eax
movl $1, i(%rip)
.L9:
movq $f, j(%rip)
xorl %edx, %edx
cmpw $4, %cx
setle %dl
notl %edx
movswl %dx, %edx
cmpl %edx, %eax
setb %dl
movzbl %dl, %edx
cmpl %edx, %eax
jne .L11
testl %eax, %eax
je .L10
movl $-5, f(%rip)
jmp .L14
.L8:
testl %eax, %eax
jne .L24
.L10:
xorl %eax, %eax
movl %eax, f(%rip)
call foo
.L14:
xorl %eax, %eax
call s.isra.0
xorl %eax, %eax
movl $0, h(%rip)
addq $8, %rsp
ret
.L11:
xorl %eax, %eax
call s.isra.0
movl $1, i(%rip)
jmp .L14
.L23:
movl $-5, f(%rip)
jmp .L6
.L24:
movl $-5, f(%rip)
jmp .L9
gcc-13.2.0 -O3 eliminates the call to foo:
main:
xorl %eax, %eax
cmpw $0, h(%rip)
movl i(%rip), %edx
movq $f, j(%rip)
setle %al
notl %eax
cwtl
cmpl %eax, %edx
setb %al
movzbl %al, %eax
cmpl %edx, %eax
jne .L11
testl %edx, %edx
jne .L6
.L7:
xorl %eax, %eax
movl %edx, f(%rip)
call s.isra.0
xorl %eax, %eax
movl $0, h(%rip)
ret
.L11:
xorl %eax, %eax
call s.isra.0
movl $1, i(%rip)
.L6:
movq $f, j(%rip)
movl $-5, %edx
jmp .L7
Bisects to r14-2230-g7e904d6c7f2
