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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Incorrect transformation of fabs with nnan flag"
href="https://bugs.llvm.org/show_bug.cgi?id=47960">47960</a>
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<th>Summary</th>
<td>Incorrect transformation of fabs with nnan flag
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
<tr>
<th>Reporter</th>
<td>juneyoung.lee@sf.snu.ac.kr
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>// llvm/test/Transforms/InstCombine/fabs.ll
```
define double @select_fcmp_nnan_ole_zero(double %x) {
%0:
%lezero = fcmp ole double %x, 0.000000
%negx = fsub nnan double 0.000000, %x
%fabs = select i1 %lezero, double %negx, double %x
ret double %fabs
}
=>
define double @select_fcmp_nnan_ole_zero(double %x) {
%0:
%1 = fabs nnan double %x
ret double %1
}
Transformation doesn't verify!
ERROR: Target is more poisonous than source
Example:
double %x = NaN
Source:
i1 %lezero = #x0 (0)
double %negx = poison
double %fabs = NaN
Target:
double %1 = poison
Source value: NaN
Target value: poison
```
After the transformation, nnan flag should be dropped because %x can be NaN.</pre>
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