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    <head>
      <base href="http://llvm.org/bugs/" />
    </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 optimisation opportunity in collapsing simple switch BBs"
   href="http://llvm.org/bugs/show_bug.cgi?id=19853">19853</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Missed optimisation opportunity in collapsing simple switch BBs
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>tools
          </td>
        </tr>

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

        <tr>
          <th>Hardware</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </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>opt
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>expipiplus1@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvmbugs@cs.uiuc.edu
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=12564" name="attach_12564" title="Function comparing two i32s in a limited range.">attachment 12564</a> <a href="attachment.cgi?id=12564&action=edit" title="Function comparing two i32s in a limited range.">[details]</a></span>
Function comparing two i32s in a limited range.

The attached function takes two i32 values (%0 and %1) in the range [0,6] and
compares equality by switching on the value of %0. In the switched to basic
block %1 is compared to a constant which is equal to %0. 

The branches to a phi and ret block could be replaced with ret instructions.

The blocks are also identical when replacing the constant with the value of %0,
and could be merged.

The function could be reduced to an icmp and a zext, instead it retains the
switch to a specialised block structure.</pre>
        </div>
      </p>
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