| Issue |
126670
|
| Summary |
`try` block prevents LLVM from identifying a throwing path is unreachable
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
jeremy-rifkin
|
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
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