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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - multiple isnan() checks enhancement"
href="https://bugs.llvm.org/show_bug.cgi?id=41069">41069</a>
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<th>Summary</th>
<td>multiple isnan() checks enhancement
</td>
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<th>Product</th>
<td>clang
</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>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>-New Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>kobalicek.petr@gmail.com
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</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>It would be nice if clang/LLVM can merge multiple isnan checks into `ucomisd a,
b`. Consider the following C++ Code:
#include <cmath>
#include <algorithm>
bool isNaN(double a, double b, double c, double d) {
return std::isnan(a) |
std::isnan(b) |
std::isnan(c) |
std::isnan(d) ;
}
Clang Output
------------
isNaN(double, double, double, double):
ucomisd xmm0, xmm1 ## THIS IS OKAY
setp al
ucomisd xmm2, xmm2 ## HERE IS SOME PROBLEM
setp cl
or cl, al
ucomisd xmm3, xmm3
setp al
or al, cl
ret
GCC Output
----------
isNaN(double, double, double, double):
ucomisd xmm0, xmm1
setp al
ucomisd xmm2, xmm3
setp dl
or eax, edx
ret
It seems that the pattern is already recognized but not applied to second and
third isnan checks.</pre>
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</p>
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