<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/57330>57330</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
Missed optimization of uaddo(x, x)
</td>
</tr>
<tr>
<th>Labels</th>
<td>
llvm:codegen,
missed-optimization
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
chfast
</td>
</tr>
</table>
<pre>
```c
_Bool src(unsigned x, unsigned* acc) {
unsigned s = x + x;
*acc = s;
return (s < x);
}
_Bool tgt(unsigned x, unsigned* acc) {
return __builtin_uadd_overflow(x, x, acc);
}
```
https://godbolt.org/z/PsGoGGWj8
The `uaddo` is not created for the case of `x + x`. This would save us single `cmp` instruction. This may be because the `x + x` is optimized to `x << 1`.
Discovered while analyzing https://github.com/llvm/llvm-project/issues/57316.
</pre>
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