<html>
<head>
<base href="http://llvm.org/bugs/" />
</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 --- - Missing memory folding with new vector shuffle lowering."
href="http://llvm.org/bugs/show_bug.cgi?id=21137">21137</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing memory folding with new vector shuffle lowering.
</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>normal
</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>qcolombet@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>Created <span class=""><a href="attachment.cgi?id=13121" name="attach_13121" title="IR to reproduce the problem">attachment 13121</a> <a href="attachment.cgi?id=13121&action=edit" title="IR to reproduce the problem">[details]</a></span>
IR to reproduce the problem
When using the new vector shuffle lowering, some folding opportunities are
missed.
To reproduce:
llc -x86-experimental-vector-shuffle-lowering=true missing_folding.ll -o new.s
llc -x86-experimental-vector-shuffle-lowering=false missing_folding.ll -o old.s
diff -U 10 old.s new.s
- pshufd $27, (%rdi), %xmm0 ## xmm0 = mem[3,2,1,0]
+ movaps (%rdi), %xmm0
+ shufps $27, %xmm0, %xmm0 ## xmm0 = xmm0[3,2,1,0]
The shuffle instruction used in the new lowering is on a different than the old
one (different domain). Thus, it is likely we need to teach how to fold the
operand for that one too.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>