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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - instcombine incorrectly turns unsigned pointer comparision into signed comparison"
href="http://llvm.org/bugs/show_bug.cgi?id=16483">16483</a>
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<th>Summary</th>
<td>instcombine incorrectly turns unsigned pointer comparision into signed comparison
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Scalar Optimizations
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>richard@xmos.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 I give instcombine the following IR:
define i1 @f([1 x i8]* %a, [1 x i8]* %b) {
%c = getelementptr [1 x i8]* %a, i32 0, i32 0
%d = getelementptr [1 x i8]* %b, i32 0, i32 0
%cmp = icmp ult i8* %c, %d
ret i1 %cmp
}
opt -instcombine turns it into:
define i1 @f([1 x i8]* %a, [1 x i8]* %b) {
%cmp = icmp slt [1 x i8]* %a, %b
ret i1 %cmp
}
i.e it has turned an unsigned pointer comparision into a signed comparision
that will give different results with some inputs.</pre>
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