https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111799
Bug ID: 111799
Summary: [14 Regression] Missed Dead Code Elimination since
r14-2365-g2e406f0753e
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/bqcvMcbqn
Given the following code:
void foo(void);
static struct d {
short e;
} g = {205}, *h = &g;
static int i;
static int *j, *a = &i;
static int **k = &j;
static int ****l;
static int *****m;
static char(n)(char b, char c) { return b + c; }
static char(o)(char b, char c) { return b * c; }
static short(p)(short f) {
if (!(((f) >= 1) && ((f) <= 65459))) {
__builtin_unreachable();
}
return 0;
}
static int *q(short);
static void s(struct d) { *k = q(i); }
static int *q(short ad) {
int b = *a;
ad = -21;
for (; ad; ad = n(ad, 7)) p((ad ^ b && *a) <= *a);
return *k;
}
int main() {
i = 0;
for (;; i = 1) {
q(3);
char r = o(126 | 1, g.e);
p(r);
s(*h);
if (i) break;
m = &l;
}
if (m)
;
else
foo();
;
}
gcc-trunk -O2 does not eliminate the call to foo:
main:
movl $2, %esi
xorl %ecx, %ecx
xorl %r9d, %r9d
movl $8, %edi
movl $0, i(%rip)
.p2align 4,,10
.p2align 3
.L10:
movl $-21, %eax
.L2:
testl %ecx, %ecx
je .L29
leal 7(%rax), %edx
movsbw %dl, %r8w
testb %dl, %dl
je .L23
.L5:
movl $8, %eax
cmpb $1, %dl
je .L2
movl %r8d, %eax
leal 7(%rax), %edx
movsbw %dl, %r8w
testb %dl, %dl
jne .L5
.p2align 4,,10
.p2align 3
.L23:
movl $-21, %eax
addb $7, %al
je .L30
.L9:
movsbl %al, %edx
cmpl %edx, %ecx
cmove %edi, %eax
cbtw
addb $7, %al
jne .L9
.L30:
cmpl $1, %esi
je .L31
movl $1, %esi
movl $1, %ecx
movl $1, %r9d
jmp .L10
.p2align 4,,10
.p2align 3
.L29:
testb $1, %al
je .L4
leal 7(%rax), %edx
movsbw %dl, %ax
testb %dl, %dl
je .L23
.L4:
leal 14(%rax), %edx
movsbw %dl, %ax
testb %dl, %dl
jne .L4
jmp .L23
.p2align 4,,10
.p2align 3
.L31:
testb %r9b, %r9b
je .L11
movq $l, m(%rip)
movl %ecx, i(%rip)
.L25:
xorl %eax, %eax
ret
.L11:
cmpq $0, m(%rip)
jne .L25
pushq %rax
call foo
xorl %eax, %eax
popq %rdx
ret
gcc-13.2.0 -O2 eliminates the call to foo:
main:
movq $l, m(%rip)
xorl %eax, %eax
movl $1, i(%rip)
ret
Bisects to r14-2365-g2e406f0753e
