<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 --- - GEP on struct pointer obtained from bitcast canonicalized incorrectly"
href="http://llvm.org/bugs/show_bug.cgi?id=19048">19048</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>GEP on struct pointer obtained from bitcast canonicalized incorrectly
</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>Linux
</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>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>benjamin@spacecurve.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=12187" name="attach_12187" title="Misoptimized testcase">attachment 12187</a> <a href="attachment.cgi?id=12187&action=edit" title="Misoptimized testcase">[details]</a></span>
Misoptimized testcase
In the attached code, if a datalayout declaration is present the instructions
%variant_source = bitcast i16* %dataload_case_ptr to { i16, i64 }*
%8 = getelementptr inbounds { i16, i64 }* %variant_source, i32 0, i32 1
%9 = load i64* %8
store i64 %9, i64* %1, align 8
get transformed by opt -O3 into
%6 = getelementptr inbounds i16* %5, i64 4
%7 = bitcast i16* %6 to i64*
%8 = load i64* %7, align 8
store i64 %8, i64* %1, align 8
If the datalayout is removed, the bitcast is instead deleted entirely and
retains the correct GEP form, at which point returning the datalayout once more
and re-optimizing correctly reduces the entire function to 'ret i8 1', which is
ideally what would happen regardless. Presumably the noncanonical form
interferes with further optimizations.</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>