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<div class="moz-cite-prefix">On 9/25/2017 5:35 AM, Martin J.
O'Riordan via llvm-dev wrote:<br>
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<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">I am seeing failures in two tests after
migrating to v5.0 final, these are:<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span
style="font-family:"Courier New";color:black">std/language.support/support.limits/limits/numeric.limits.members/quiet_NaN.pass.cpp</span><span
style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">and:<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:36.0pt"><span
style="font-family:"Courier New";color:black">std/language.support/support.limits/limits/numeric.limits.members/signaling_NaN.pass.cpp</span><span
style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">However, these are new tests and it
turns out that the underlying problem is that the builtin ‘</span><span
style="font-size:12.0pt;font-family:"Courier New"">__builtin_nanl(“”)</span><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">’ is returning the value </span><span
style="font-size:12.0pt;font-family:"Courier New"">0x0000000000000000</span><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">. I tested this builtin with our v4.0
compiler and it has the same problem, so this is not a
regression but rather an existing bug exposed by the new
LibC++ implementation of ‘</span><span
style="font-size:12.0pt;font-family:"Courier New""><limits></span><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">’.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">But our implementation of FP64 is a
software only implementation using the FP64 support
functions in ‘</span><span
style="font-size:12.0pt;font-family:"Courier New"">compiler-rt</span><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">’ and we have no lowering actions of
our own.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif">Where should I be looking to find out
how to fix this? Is it a CLang issue of an LLVM issue?<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Book
Antiqua",serif"><o:p> </o:p></span></p>
</div>
</blockquote>
<br>
__builtin_nanl("") gets constant-folded by clang; if you look at the
LLVM IR, you should see something like "double 0x7FF8000000000000".
Where exactly is 0x0000000000000000 showing up?<br>
<br>
-Eli<br>
<pre class="moz-signature" cols="72">--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project</pre>
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