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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 --- - optimization failure when parameters passed by pointer (vs passing in a struct)"
href="http://llvm.org/bugs/show_bug.cgi?id=22123">22123</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>optimization failure when parameters passed by pointer (vs passing in a struct)
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>skvadrik@gmail.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=13649" name="attach_13649" title="files 1a.cpp, 1b.cpp, 2a.cpp and 2b.cpp">attachment 13649</a> <a href="attachment.cgi?id=13649&action=edit" title="files 1a.cpp, 1b.cpp, 2a.cpp and 2b.cpp">[details]</a></span>
files 1a.cpp, 1b.cpp, 2a.cpp and 2b.cpp
See files 1a.cpp, 1b.cpp, 2a.cpp and 2b.cpp in attach.
The only difference between 1*.cpp and 2*.cpp is that
1*.cpp pass parameters in a struct, while 2*.cpp pass
them by pointer.
compile:
$ clang++ -g -O2 -c 1a.cpp
$ clang++ -g -O2 -c 1b.cpp
$ clang++ -g -O2 -c 2a.cpp
$ clang++ -g -O2 -c 2b.cpp
disassemble: (GNU objdump (GNU Binutils) 2.24)
$ objdump -d 1a.o > 1a.s
$ objdump -d 1b.o > 1b.s
$ objdump -d 2a.o > 2a.s
$ objdump -d 2b.o > 2b.s
Files 1a.s and 1b.s are equivalent, but
files 2a.s and 2b.s are different: extra memory load in 2b.s.
On -O1, both pairs differ in the same way.
Tested on x86_64, armv7a, powerpc64.</pre>
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