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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - relocations for new removed when optimization turned on"
href="http://llvm.org/bugs/show_bug.cgi?id=21421">21421</a>
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<th>Summary</th>
<td>relocations for new removed when optimization turned on
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>danalbert@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>danalbert@google.com, eric@efcs.ca, llvmbugs@cs.uiuc.edu, srhines@google.com
</td>
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<th>Blocks</th>
<td>21420
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Enabling -Os or -O2 (probably others, but haven't checked) for the libc++ tests
causes
<a href="https://github.com/llvm-mirror/libcxx/blob/b64f8b07c104c6cc986570ac8ee0ed16a9f23976/test/language.support/support.dynamic/new.delete/new.delete.single/new_nothrow_replace.pass.cpp">https://github.com/llvm-mirror/libcxx/blob/b64f8b07c104c6cc986570ac8ee0ed16a9f23976/test/language.support/support.dynamic/new.delete/new.delete.single/new_nothrow_replace.pass.cpp</a>
to fail. Inspection shows this is because the optimization is causing no
relocation to nothrow new (mangled: _ZnwjRKSt9nothrow_t) to be emitted.
# With -O0
$ readelf -r foo.o | grep _ZnwjRK
00000018 0000840a R_ARM_THM_CALL 00000000 _ZnwjRKSt9nothrow_t
# With -Os
$ readelf -r baz.o | grep _ZnwjRK
# no output
The emitted IR shows no reference to _ZnwjRKSt9nothrow_t at -Os, but does at
-O0, so I'm assuming this is a clang codegen issue. Also checked with
-fno-assume-sane-operator-new, so I don't think this is related to the
new/delete being optimized out.
EricWF checked GCC, and said that it exhibits the correct behavior.</pre>
</div>
</p>
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