<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 - Missed loop vectorization"
   href="https://bugs.llvm.org/show_bug.cgi?id=39420">39420</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Missed loop vectorization
          </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>Linux
          </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>Loop Optimizer
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>david.bolvansky@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>We are unable to vectorize:

  for (size_t i = 0; i < nrpt; i++) {
    for (size_t j = 0; j < nsize; j++) {
      a[j] = (float)0.0f;
    }

    for (size_t j = 0; j < nsize; j++) {
      for (size_t k = 0; k < nsize; k++) {
        a[j] += b[j] * c[j][k];
      }
    }
  }

While GCC/ICC has no issues with this code. (-march=haswell)

Code example: <a href="https://godbolt.org/z/ooyf1N">https://godbolt.org/z/ooyf1N</a></pre>
        </div>
      </p>


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