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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - An integer overflow bug in InstructionSimplify.cpp:SimplifyICmpInst introduced in r208999: sdiv const, value"
href="http://llvm.org/bugs/show_bug.cgi?id=20199">20199</a>
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<th>Summary</th>
<td>An integer overflow bug in InstructionSimplify.cpp:SimplifyICmpInst introduced in r208999: sdiv const, value
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
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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>Global Analyses
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>vslugovsky@gmail.com
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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>If a first sdiv argument + 1 overflows, a wrong range is calculated.
A test case (should be compiled with clang with -O1):
extern void abort(void);
int main (void)
{
volatile long int n;
n = -2;
if ((-2147483647L - 1L) / (-n) != -1073741824L)
abort ();
return 0;
}
A simple overflow check at around the following lines should fix the issue:
} else if (match(LHS, m_SDiv(m_ConstantInt(CI2), m_Value()))) {
// 'sdiv CI2, x' produces [-|CI2|, |CI2|].
Upper = CI2->getValue().abs() + 1;
Lower = (-Upper) + 1;</pre>
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