<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/63121>63121</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Possible wrong-code on -O2 and above (affecting LLVM 12.0.1 downward versions)
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          haoxintu
      </td>
    </tr>
</table>

<pre>
    Hi, the following code makes LLVM 12.0.1 downward versions behave differently. It might be an issue in LLVM's optimization, can you take a look, please?

```
#include <stdint.h>
#include <stdio.h>
int8_t a = 0, j=0, b=0;
int ids = 0;
void __attribute__((noinline)) marker_1() {
    printf(" b%db ", 1);
    ids ++;
}
int8_t *c(uint32_t, uint16_t);
void d();
int16_t e(uint8_t, int8_t *, uint32_t);
uint32_t f() {
  int8_t g[1][10] = {0,0,0,0,0,0,0,0,0,0};
  d();
  c(g[0][2], g[0][8]);
  return 0;
}
int8_t *c(uint32_t h, uint16_t i) {
  marker_1();
  return &b;
}
void d() {
  int m = 0;
  for (; m <= 5; m++)
    e(0, &a, 0);
}
int16_t e(uint8_t k, int8_t *l, uint32_t o) {
  for (; j;)
  n:;
    goto n;
}
int main() { 
    f(); 
 printf("%d\n", ids); 
}
```
$clang-trunk -w -O2 test.c ; ./a.out
(output nothing)
$clang-12.0.1 -w -O2 test.c ; ./a.out
 b1b 1
$clang-12.0.1 -w -O1 test.c ; ./a.out
(hang)

$clang-trunk -v
clang version 16.0.0 (https://github.com/llvm/llvm-project bf6f82a9df6a1693a5399039dcadd7fc00dab65e)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/haoxin/haoxin-data/compilers/llvm-project/build/bin
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/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
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
Found CUDA installation: /usr/lib/cuda, version 

Code on GodBolt: https://godbolt.org/z/Wsh6Thd5v

Thanks,
Haoxin
</pre>
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