| Issue |
63893
|
| Summary |
Wrong code at -O2 on x86_64-linux_gnu (a recent regression in Two-Address instruction pass)
|
| Labels |
|
| Assignees |
|
| Reporter |
shao-hua-li
|
This looks like a recent regression. Clang at -O2 produces the wrong code. `opt-bisect-limit` suggests that the issue might be in ` Two-Address instruction pass`.
Compiler explorer: https://godbolt.org/z/G6vxTTzPr
```console
% cat a.c
int printf(const char *, ...);
short c;
int f, q = 3, r, t, z, ae_y;
char g, b, h, m, o, s;
static long i_0_0 = 23772937180;
static char *j = &b;
static char **k[5] = {&j};
static char ***l = &k[4];
long n;
static long *p = &i_0_0, *e = &i_0_0;
int *ae(int *ad) {
long u;
int *v = &f;
af:
for (;;) {
*j = 8;
int w;
for (; o; o--)
if (*j + *p + g)
goto af;
if (*ad)
;
else{
for (; t <= 1; t++) {
int *x = &r;
for (;; s++) {
*v = 9;
if (q + *ad)
break;
}
if (g)
goto af;
for (; s + m; m++)
;
u = *e;
*e = (unsigned)u;
*x ^= (int)n + m;
*v = c;
if (*v)
;
else {
ad = &ae_y;
return x;
}
}
}
for (; h;)
;
}
}
void ag() { char ****a[] = {&l, &l}; }
int main() {
ae(&z);
printf("%ld\n", i_0_0);
}
%
% clang-tk -O0 a.c && ./a.out
2298100700
%
% clang-tk -O2 a.c && ./a.out
23772937180
%
% clang-tk -v
clang version 17.0.0 (https://github.com/llvm/llvm-project.git 46333f71f8e0d6444a9b2c9e063aedb83ebb9735)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /zdata/shaoli/compilers/ccbuilder-compilers
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Candidate multilib: .;@m64
Selected multilib: .;@m64
%
```
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