<html>
    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Merge 5b5dc2442ac7 into 11.0 release branch"
   href="https://bugs.llvm.org/show_bug.cgi?id=46807">46807</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Merge 5b5dc2442ac7 into 11.0 release branch
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Windows NT
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Backend: X86
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>llvm-dev@redking.me.uk
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
          </td>
        </tr>

        <tr>
          <th>Blocks</th>
          <td>46725
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Based off an investigation into a test case provided by Craig, we need to avoid
traversing the DAG inside getTargetShuffleMask - I investigated hasOneUse()
wrappers but this approach is safer and we have other shuffle decode/combines
that can handle more complex broadcast shuffle folds.

Craig - are you OK with this getting merged?


<a href="https://reviews.llvm.org/rG5b5dc2442ac7">https://reviews.llvm.org/rG5b5dc2442ac7</a>

[X86][AVX] getTargetShuffleMask - don't decode
VBROADCAST(EXTRACT_SUBVECTOR(X,0)) patterns.

getTargetShuffleMask is used by the various "SimplifyDemanded" folds so we
can't assume that the bypassed extract_subvector can be safely simplified -
getFauxShuffleMask performs a more general decode that allows us to more safely
catch many of these cases so the impact is minimal.</pre>
        </div>
      </p>

        <div id="referenced">
          <hr style="border: 1px dashed #969696">
          <b>Referenced Bugs:</b>
          <ul>
              <li>
                [<a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [meta] 11.0.0 Release Blockers"
   href="https://bugs.llvm.org/show_bug.cgi?id=46725">Bug 46725</a>] [meta] 11.0.0 Release Blockers
              </li>
          </ul>
        </div>
        <br>

      <hr>
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