<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/63739>63739</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Program is miscompile with '-O1' option
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          Yvan-xy
      </td>
    </tr>
</table>

<pre>
    My clang version is:
```
Apple clang version 13.1.6 (clang-1316.0.21.2.5)
Target: x86_64-apple-darwin21.4.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
```

And I compiled the following program with `clang -O1 -o a a.cpp`:

```c++
#include <mutex>
#include <chrono>
#include <string>
#include <thread>
#include <vector>
#include <iostream>

#include <cassert>

std::mutex l;

void f(std::size_t id) {
  while (true) {
    {
      std::lock_guard<std::mutex> guard(l);
 std::cout << "thread " << id << " acquired\n";
    }
 }
}


int main() {
  for (std::size_t i = 0; i < 256; i++) {
    std::thread t(f, i);
    t.detach();
    std::cout << i << std::endl;
  }

  while(1);
}
```

The program would keep running the `for` loop rather than stop when `i == 256`.

I suppose that, without special treatment for `while(1)`, the exit on the control flow graph (CFG) will not post-dominant the preceding nodes. As a result, passes that rely on post-dominators for optimization will not work correctly.



</pre>
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