<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/85065>85065</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [DAG] SDPatternMatch - add m_Neg and m_Not matchers
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            good first issue,
            llvm:SelectionDAG
      </td>
    </tr>

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

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

<pre>
    I've started using the SDPatternMatch.h matchers to simplify dag combines (especially commutable ones - thank you for that!).

We're currently missing a couple of convenience matchers for
```c
m_Neg(m_Value(X)) == m_Sub(m_Zero(), m_Value(X))
m_Not(m_Value(X)) == m_Xor(m_Value(X), m_AllOnes())
```
You will need some experience with C++ templates to understand the pattern matching system to add these.

CC @mshockwave 
</pre>
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