<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/137249>137249</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Window scheduler ignores IMPLICIT_DEF instructions
        </td>
    </tr>

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

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

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

<pre>
    ## Description
I was working with window scheduler and found confusing part in its algorithm. 
On the line llvm/lib/CodeGen/WindowScheduler.cpp:300 WindowScheduler copies region to schedule, but ignores meta instructions one of which is IMPLICIT_DEF. Because of this all uses of IMPLICIT_DEF have no definition. This results in assertion later in code.

I created a reproduction for Hexagon, but I am not sure whether this code is correct. Probably, there are other examples where IMPLICIT_DEF and its use are in the same basic block, but I could not find them.

## Reproduction
```
bash ./run.txt
```
[run.txt](https://github.com/user-attachments/files/19899179/run.txt)

[pipeliner-assert.txt](https://github.com/user-attachments/files/19899182/pipeliner-assert.txt)

Debug build fails with assertion. 
</pre>
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