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    <head>
      <base href="http://llvm.org/bugs/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - RegisterCoalescer should do more subregister remats"
   href="http://llvm.org/bugs/show_bug.cgi?id=15264">15264</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>RegisterCoalescer should do more subregister remats
          </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>All
          </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>Register Allocator
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>zwarich@apple.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>It should be possible to remat this pair of instructions:

DefMI: %vreg11<def> = MOV16r0 %EFLAGS<imp-def,dead>; GR16:%vreg11
CopyMI: %vreg23:sub_16bit<def,read-undef> = COPY %vreg11; GR32:%vreg23
NewMI: %vreg23:sub_16bit<def,read-undef> = MOV16r0 %EFLAGS<imp-def,dead>;
GR32:%vreg23

However, reMaterializeTrivialDef() currently bails because GR32 != GR16.</pre>
        </div>
      </p>
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