<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/62430>62430</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Miscompilation in LoopStrengthReduce
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            miscompilation
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          d-makogon
      </td>
    </tr>
</table>

<pre>
    Reproducer: https://godbolt.org/z/54r6nnccM
Alive2: https://alive2.llvm.org/ce/z/AmPCvh

LSR inserts a lot of IVs during code expansion for some SCEVs.
In the test loop `bb4` never takes its backedge, so effectively `%phi5` and `%shl` values are zeroes.
Then `@foo` is called with the argument equal to the value of `%phi` to the power of 6. On the first iteration it is zero, on the second iteration it is `4^6 = 4096`.
LSR replaces the `@foo` argument with the newly inserted `%lsr.iv21`. It is an expansion of some large SCEV expression with many addrecs. However it is inserted in the `bb4` loop, so effectively `%lsr.iv21` value is always zero. So in the version after LSR we always call `@foo` with argument equal to zero while in the initial test its value changes (on 2nd iter it's 4096).


</pre>
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