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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Backward copy propagation failed w/ -g"
href="https://bugs.llvm.org/show_bug.cgi?id=49446">49446</a>
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<th>Summary</th>
<td>Backward copy propagation failed w/ -g
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>chenzhiwei03@kuaishou.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=24590" name="attach_24590" title="The hot.cc is generated by creduce">attachment 24590</a> <a href="attachment.cgi?id=24590&action=edit" title="The hot.cc is generated by creduce">[details]</a></span>
The hot.cc is generated by creduce
To reproduce
<span class="quote">> clang++ -c hot.cc -o dbg.o -O3 -g
> clang++ -c hot.cc -o rel.o -O3</span >
Then diff the objdump outputs.
- c2: 48 8d 6c 24 28 lea 0x28(%rsp),%rbp
- c7: 48 89 eb mov %rbp,%rbx
- ca: 0f 11 45 00 movups %xmm0,0x0(%rbp)
+ c2: 48 8d 5c 24 28 lea 0x28(%rsp),%rbx
+ c7: 0f 11 03 movups %xmm0,(%rbx)
+ ca: 8b 44 24 20 mov 0x20(%rsp),%eax
For those two instructions:
lea 0x28(%rsp), %rbp
mov %rbp, %rbx
can be applied with backward copy propagation to eliminate the rbp register.</pre>
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