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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - very slow compilation at -O2 and -O3"
href="https://bugs.llvm.org/show_bug.cgi?id=44518">44518</a>
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<th>Summary</th>
<td>very slow compilation at -O2 and -O3
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>-New Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>hehaochen13@nudt.edu.cn
</td>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>Created <span class=""><a href="attachment.cgi?id=23010" name="attach_23010" title="Test case for linux">attachment 23010</a> <a href="attachment.cgi?id=23010&action=edit" title="Test case for linux">[details]</a></span>
Test case for linux
clang 3.4.2:
g++ -O0 -c t2.cc 1.1s
g++ -O1 -c t2.cc 5.0s
g++ -O2 -c t2.cc 1m 21s
g++ -O3 -c t2.cc 1m 25s
---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name
---
42.2165 ( 51.7%) 2.5971 ( 48.9%) 44.8135 (51.6%) 44.8155 (51.6%) Value
Propagation
27.8303 ( 34.1%) 1.8011 ( 33.9%) 29.6314 (34.1%) 29.6327 (34.1%) Value
Propagation
apple clang 11.0:
g++ -O0 -c t2.cc 1.0s
g++ -O1 -c t2.cc 2.9s
g++ -O2 -c t2.cc 36.5s
g++ -O3 -c t2.cc 35.8s
---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name ---
23.6581 (64.7%) 0.1341 (19.8%) 23.7922 (63.9%) 23.9388 (64.0%) Global Value
Numbering
5.8555 (16.0%) 0.0067 ( 1.0%) 5.8622 (15.7%) 5.8636 (15.7%) Hot Cold
Splitting
But in gcc-4.8.5:
g++ -O0 -c t2.cc 1.7s
g++ -O1 -c t2.cc 3.0s
g++ -O2 -c t2.cc 3.8s
g++ -O3 -c t2.cc 3.9s</pre>
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