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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 can miscompile code involving uninitialized value and xor-s"
   href="https://bugs.llvm.org/show_bug.cgi?id=36610">36610</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>clang can miscompile code involving uninitialized value and xor-s
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>5.0
          </td>
        </tr>

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

        <tr>
          <th>OS</th>
          <td>FreeBSD
          </td>
        </tr>

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

        <tr>
          <th>Severity</th>
          <td>normal
          </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>avg@FreeBSD.org
          </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=20001" name="attach_20001" title="demonstration code">attachment 20001</a> <a href="attachment.cgi?id=20001&action=edit" title="demonstration code">[details]</a></span>
demonstration code

It appears can miscompile (or incorrectly optimize) code where an uninitialized
variable gets assigned a value through a series of assignments that set only a
subset of bits in the variable.  In the end all bits in the variable get
defined values, but intermediate assignments involve operations with undefined
bits.</pre>
        </div>
      </p>


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