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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Replace ShuffleKind::SK_Alternate with ShuffleKind::SK_Blend"
href="https://bugs.llvm.org/show_bug.cgi?id=33744">33744</a>
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<th>Summary</th>
<td>Replace ShuffleKind::SK_Alternate with ShuffleKind::SK_Blend
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Scalar Optimizations
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
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<th>CC</th>
<td>a.bataev@hotmail.com, dtemirbulatov@gmail.com, hfinkel@anl.gov, llvm-bugs@lists.llvm.org, mkuper@google.com, spatel+llvm@rotateright.com
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<pre>ShuffleKind::SK_Alternate requires shuffle masks to only match an alternating
pattern from its 2 sources:
e.g. v4f32: <0,5,2,7> or <4,1,6,3>
This seems far too restrictive for most SIMD hardware which will probably
implement it using a general blend/bit-select instruction (permitting elements
from either source as long as they are inline):
e.g. v4f32: <0,5,2,7>, <4,1,6,3>, <0,1,6,7>, <4,1,2,3> etc.
Are there any reasons why we shouldn't replace ShuffleKind::SK_Alternate with
ShuffleKind::SK_Blend to encourage more vectorization?</pre>
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