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    <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 - Clang punts on vectorization and issues incorrect diagnostic"
   href="https://bugs.llvm.org/show_bug.cgi?id=34125">34125</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Clang punts on vectorization and issues incorrect diagnostic
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>4.0
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Macintosh
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>MacOS X
          </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>-New Bugs
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>jeff.science@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=18948" name="attach_18948" title="make command output">attachment 18948</a> <a href="attachment.cgi?id=18948&action=edit" title="make command output">[details]</a></span>
make command output

Clang claims the reason it does not vectorize star[45] is because the trip
count cannot be determined, but the trip count determination is identical in
star[123], which are vectorized.

./stencil_tbb.hpp:63:7: remark: loop not vectorized: could not determine number
of loop iterations [-Rpass-analysis]
      for (auto j=r.cols().begin(); j!=r.cols().end(); ++j ) {
      ^

As best I can tell, the issue is that the loop bodies for star[45] are too
large.  Functions with 12 or fewer terms are vectorized whereas those with 16
or more are not.</pre>
        </div>
      </p>


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