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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Incorrect optimization of is_simm32 C++ function from HotSpot JVM sources"
href="http://llvm.org/bugs/show_bug.cgi?id=18591">18591</a>
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<th>Summary</th>
<td>Incorrect optimization of is_simm32 C++ function from HotSpot JVM sources
</td>
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<th>Product</th>
<td>new-bugs
</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>Linux
</td>
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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
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>mikael.gerdin@oracle.com
</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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</tr></table>
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<pre>Created <span class=""><a href="attachment.cgi?id=11924" name="attach_11924" title="test case">attachment 11924</a> <a href="attachment.cgi?id=11924&action=edit" title="test case">[details]</a></span>
test case
I tried to build the OpenJDK JVM with clang++ 3.4 and discovered that the 32
bit version seems to hit an impossible assert.
I did some digging and found out that the function Assembler::is_simm32 is
incorrectly optimized, causing us to always hit the assert.
The JVM sources in question are here:
<a href="http://hg.openjdk.java.net/jdk9/hs/hotspot/file/3e2b76368121/src/share/vm/asm/assembler.hpp">http://hg.openjdk.java.net/jdk9/hs/hotspot/file/3e2b76368121/src/share/vm/asm/assembler.hpp</a>
The bug appears on -O2 and above, both with clang-3.4 and with llvm+clang trunk
as of 2014-01-23.
I've created a reduced test case (attached)
llvm-build$ Release+Asserts/bin/clang++ -O1 -m32 ~/scratch/is_simm.cc; ./a.out;
echo "Exit code: $?"
is_simm32(1) = 1
min_simm(32) <= 1 && 1 <= max_simm(32) = 1
Exit code: 0
llvm-build$ Release+Asserts/bin/clang++ -O2 -m32 ~/scratch/is_simm.cc; ./a.out;
echo "Exit code: $?"
is_simm32(1) = 0
min_simm(32) <= 1 && 1 <= max_simm(32) = 1
Exit code: 1</pre>
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