<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/126670>126670</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            `try` block prevents LLVM from identifying a throwing path is unreachable
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          jeremy-rifkin
      </td>
    </tr>
</table>

<pre>
    For the following code LLVM inlines `std::vector::at` and optimizes away the bounds check
```cpp
std::vector<int> without_try_catch() {
    std::vector<int> v(10'000);
    for(int i = 0; i < 10'000; ++i) {
        v.at(i) = i;
 }
    return v;
}
```

However, for the following, the presence of a `try`/`catch` precludes LLVM from proving away the bounds check and the subsequent throwing path.
```cpp
std::vector<int> with_try_catch() {
 std::vector<int> v(10'000);
    for(int i = 0; i < 10'000; ++i) {
 try {
            v.at(i) = i;
        } catch(...) {}
    }
    return v;
}
```

As a result this dead-code `try`/`catch` results in far worse codegen.

CE link: https://godbolt.org/z/e3sT1z4bd
</pre>
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