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<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>
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<th>Summary</th>
<td>[X86][SSE] Use PHMINPOSUW for i8/i16 min/max reductions
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: X86
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
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<th>CC</th>
<td>filcab@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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<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>
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