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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Extremely slow compilation due to greedy register allocator"
href="http://llvm.org/bugs/show_bug.cgi?id=19217">19217</a>
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<th>Summary</th>
<td>Extremely slow compilation due to greedy register allocator
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>3.4
</td>
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<th>Hardware</th>
<td>Macintosh
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<th>OS</th>
<td>MacOS X
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>LLVM Codegen
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>feeley@iro.umontreal.ca
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>The compilation of a large C file (generated by the Gambit Scheme to C
compiler) is very slow at -O1 and a time-report indicates that 97% of the time
is spent in the greedy register allocator. The file takes 3000 times longer to
compile with -O1 than with -O0 (35 minutes vs. 0.7 seconds).
The issue can be reproduced with this invocation of clang:
clang -O1 -c -D___SINGLE_HOST _x86.c
Note that gcc-4.8.2 takes 5 seconds to compile with the same options.
The clang I use is Apple's LLVM version 5.1 in the latest Xcode:
% clang -v
Apple LLVM version 5.1 (clang-503.0.38) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.1.0
Thread model: posix</pre>
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</p>
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