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    <head>
      <base href="http://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 - [X86][SSE] Use PHMINPOSUW for i8/i16 min/max reductions"
   href="http://bugs.llvm.org/show_bug.cgi?id=32841">32841</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>[X86][SSE] Use PHMINPOSUW for i8/i16 min/max reductions
          </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>Windows NT
          </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>Backend: X86
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>llvm-dev@redking.me.uk
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>filcab@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>With suitable bit twiddling, PHMINPOSUW can be used to determine the
signed/unsigned min/max element of v16i8/v8i16 vectors, not just umin v8i16.

e.g.

unsigned char umin_v16i8(__m128i a) {
  __m128i result = a;
  result = _mm_min_epu8( result, _mm_srli_epi16( result, 8 ) );
  result = _mm_minpos_epu16( result );
  return _mm_extract_epi8(result, 0);
}

char smax_v16i8(__m128i a) {
  __m128i k127 = _mm_set1_epi8(127);
  __m128i result = a;
  result = _mm_xor_si128( k127, result );
  result = _mm_min_epu8( result, _mm_srli_epi16( result, 8 ) );
  result = _mm_minpos_epu16( result );
  result = _mm_xor_si128( k127, result );
  return _mm_extract_epi8(result, 0);
}</pre>
        </div>
      </p>


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