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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - @llvm.maxnum.* does not handle signaling NaNs the same way as IEEE 754-2008"
href="https://llvm.org/bugs/show_bug.cgi?id=27363">27363</a>
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<th>Summary</th>
<td>@llvm.maxnum.* does not handle signaling NaNs the same way as IEEE 754-2008
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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
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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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>Backend: AArch64
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>stoklund@2pi.dk
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>The @llvm.maxnum.* intrinsic is documented like this:
<span class="quote">> Follows the IEEE-754 semantics for maxNum, which also match for libm’s fmax.</span >
>
<span class="quote">> If either operand is a NaN, returns the other non-NaN operand.
> Returns NaN only if both operands are NaN.</span >
If one operand is a signaling NaN, this behavior doesn't match IEEE 754-2008:
@llvm.maxnum.f64(1.0, qNaN) -> 1.0
@llvm.maxnum.f64(1.0, sNaN) -> 1.0
IEEE 754-2008:
maxNum(1.0, qNaN) -> 1.0
maxNum(1.0, sNaN) -> qNaN
I wonder if this changed in the 2008 revision?
The Aarch64 backend translates an fmax() library call to an fmaxnm instruction
which has the 754-2008 semantics for signaling NaNs.</pre>
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