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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - New vector shuffle lowering misses to use punpckhbw"
href="http://llvm.org/bugs/show_bug.cgi?id=21139">21139</a>
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<th>Summary</th>
<td>New vector shuffle lowering misses to use punpckhbw
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<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
</td>
</tr>
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<th>Reporter</th>
<td>qcolombet@apple.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=13123" name="attach_13123" title="IR to reproduce the problem.">attachment 13123</a> <a href="attachment.cgi?id=13123&action=edit" title="IR to reproduce the problem.">[details]</a></span>
IR to reproduce the problem.
With the new vector shuffle lowering we produce a sequence of a shuffle +
unpckl instead of a more direct unpckh.
To reproduce:
llc -x86-experimental-vector-shuffle-lowering=true none_shuf_unpckl_unpckh.ll
-o new.s
llc -x86-experimental-vector-shuffle-lowering=false none_shuf_unpckl_unpckh.ll
-o old.s
diff -U 10 old.s new.s
_foo: ## @foo
.cfi_startproc
## BB#0: ## %entry
+ pshufd $78, %xmm1, %xmm1 ## xmm1 = xmm1[2,3,0,1]
pxor %xmm0, %xmm0
- punpckhbw %xmm1, %xmm0 ## xmm0 =
xmm0[8],xmm1[8],xmm0[9],xmm1[9],xmm0[10],xmm1[10],xmm0[11],xmm1[11],xmm0[12],xmm1[12],xmm0[13],xmm1[13],xmm0[14],xmm1[14],xmm0[15],xmm1[15]
+ punpcklbw %xmm1, %xmm0 ## xmm0 =
xmm0[0],xmm1[0],xmm0[1],xmm1[1],xmm0[2],xmm1[2],xmm0[3],xmm1[3],xmm0[4],xmm1[4],xmm0[5],xmm1[5],xmm0[6],xmm1[6],xmm0[7],xmm1[7]
retq</pre>
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