<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/141627>141627</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [RISCV] Unsigned atomics use signed load + zero-extension instead of unsigned loads
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          tom-rein
      </td>
    </tr>
</table>

<pre>
    The following code ([godbolt](https://godbolt.org/z/raqnhrGxa)):
```C++
#include <atomic>
unsigned char load(std::atomic_uchar &x) {
    return x.load(std::memory_order_relaxed);
}
```

Compiles into:
```
load(std::atomic<unsigned char>&):
        lb      a0, 0(a0)
 andi    a0, a0, 255
        ret
```

Instead of:
```
load(std::atomic<unsigned char>&):
        lbu     a0, 0(a0)
 ret
```
Same is the case for `unsigned short` and signed atomics casted to unsigned.
For `unsigned int` signed load is correct because of the ABI, but when it is zero-extended, llvm fails to combine the zero-extension with the load.
Non-atomic loads correctly result in unsigned loads.

</pre>
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