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<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Infinite loop in llvm::MachineBlockFrequencyInfo::getBlockFreq"
href="http://llvm.org/bugs/show_bug.cgi?id=21913">21913</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Infinite loop in llvm::MachineBlockFrequencyInfo::getBlockFreq
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>email@piotr-stefaniak.me
</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>I seem to have found a case where Clang (rev. 224219) gets stuck in
llvm::BranchProbability::scale(unsigned long) and/or
llvm::MachineBlockFrequencyInfo::getBlockFreq(llvm::MachineBasicBlock const*).
This is how I reproduce it:
pstef@gentoo /tmp $ git clone --depth 1 <a href="https://github.com/libtom/libtomcrypt">https://github.com/libtom/libtomcrypt</a>
Cloning into 'libtomcrypt'...
remote: Counting objects: 546, done.
remote: Compressing objects: 100% (468/468), done.
remote: Total 546 (delta 155), reused 190 (delta 74)
Receiving objects: 100% (546/546), 2.64 MiB | 851.00 KiB/s, done.
Resolving deltas: 100% (155/155), done.
Checking connectivity... done.
pstef@gentoo /tmp $ cd libtomcrypt
pstef@gentoo /tmp/libtomcrypt $ clang -fsanitize=undefined -I./src/headers/ -O1
-c -o src/ciphers/safer/saferp.o src/ciphers/safer/saferp.c
^C
pstef@gentoo /tmp/libtomcrypt $ \time clang -fsanitize=undefined
-I./src/headers/ -O1 -c -o src/ciphers/safer/saferp.o
src/ciphers/safer/saferp.c
^CCommand terminated by signal 2
0.00user 0.00system 8:17.20elapsed 0%CPU (0avgtext+0avgdata 52784maxresident)k
0inputs+0outputs (0major+330minor)pagefaults 0swaps
pstef@gentoo /tmp/libtomcrypt $ uname -a
Linux gentoo 3.16.5-gentoo #1 SMP Sun Nov 23 12:08:11 CET 2014 x86_64 Intel
Core 2 Duo P9xxx (Penryn Class Core 2) GenuineIntel GNU/Linux
pstef@gentoo /tmp/libtomcrypt $ clang --version
clang version 3.6.0 (trunk 224219)
Target: x86_64-unknown-linux-gnu
Thread model: posix
And this is the most relevant (slightly edited) part of PerfTop's output:
PerfTop: 3856 irqs/sec kernel: 0.4% exact: 0.0% [4000Hz cpu-clock],
(all, 1 CPU)
------------------------------------------------------------------------------------------
36.76% clang [.] llvm::BranchProbability::scale(unsigned long)
const
23.85% clang [.]
llvm::MachineBlockFrequencyInfo::getBlockFreq(llvm::MachineBasicBlock const*)
const
9.37% clang [.]
llvm::BlockFrequencyInfoImplBase::getBlockFreq(llvm::BlockFrequencyInfoImplBase::BlockNode
const&) const
1.52% clang [.] 0x000000000198ea5c
1.20% libc-2.19.so [.] 0x000000000008b65b
As requested from nicholas, I'm adding the post-optimized llvm IR as an
attachment to this report. It's created with:
clang -fsanitize=undefined -I./src/headers/ -O1 -flto -c -o file.bc
src/ciphers/safer/saferp.c</pre>
</div>
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