| Issue |
63329
|
| Summary |
Dead Code Elimination Regression when using __builtin_unreachable (trunk vs 16)
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
thetheodor
|
https://godbolt.org/z/4b8f9zWc1
Given the following code:
```C
void foo(void);
static int a, c, f;
static int *g = &a, *k = &a;
static int **h = &g, **i = &g;
static short j = 65535, l;
static char m;
static char(n)(char b) {
if (!(((b) >= -55) && ((b) <= 1))) {
__builtin_unreachable();
}
return 0;
}
static short(o)(short d, short e) { return d + e; }
static char p() {
n(1);
n(201);
**i;
*h = &f;
if (*k) return c;
m = 12 - j;
if (m)
;
else
foo();
return l;
}
int main() {
p();
n(j);
j = 0;
for (; j <= 3; j = o(j, 4))
;
}
```
clang-trunk -O2 produces:
```asm
main: # @main
# %bb.0:
movzbl j(%rip), %eax
decb %al
orb $4, %al
cmpb $12, %al
jne .LBB0_2
# %bb.1:
pushq %rax
callq foo@PLT
addq $8, %rsp
.LBB0_2:
movb $1, j(%rip)
xorl %eax, %eax
retq
.Lfunc_end0:
```
clang-16.0.5 -O2 produces:
```asm
main: # @main
# %bb.0:
movb $1, j(%rip)
xorl %eax, %eax
retq
.Lfunc_end0:
```
Bisects to 84bcfa0e1b34938d1d11a44e9e17c6e222dd2f42 (@weiguozhi )
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