<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/72651>72651</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [InstCombine][EarlyCSE] Missed optimization for not canonicalizing `select uge/ult, A, B`
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            llvm:instcombine,
            missed-optimization
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          XChy
      </td>
    </tr>
</table>

<pre>
    Alive2 proof: https://alive2.llvm.org/ce/z/mLG22y
Missed example: https://godbolt.org/z/5j3hjYY3o

### Description:
`select ult, A, B` could be canonicalized to `select uge, B, A`. But in this example, it's not canonicalized, and further, can not be eliminated by EarlyCSE or GVN.

### Real-world motivation

This snippet of IR is derived from zstd/.../extr_zstd_lazy.c_ZSTD_insertDUBT1.c (after O3 pipeline).
The example above is a reduced version. If you're interested in the original suboptimal IR and optimal IR, see also: https://godbolt.org/z/absa5fqEb

**Let me know if you can confirm that it's an optimization opportunity, thanks.**
</pre>
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