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<body><span class="vcard"><a class="email" href="mailto:david.majnemer@gmail.com" title="David Majnemer <david.majnemer@gmail.com>"> <span class="fn">David Majnemer</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED INVALID - Constant folding disagrees with GCC and FPU on result of 0./0."
href="https://llvm.org/bugs/show_bug.cgi?id=24585">bug 24585</a>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>RESOLVED
</td>
</tr>
<tr>
<td style="text-align:right;">CC</td>
<td>
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<td>david.majnemer@gmail.com
</td>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>INVALID
</td>
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<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED INVALID - Constant folding disagrees with GCC and FPU on result of 0./0."
href="https://llvm.org/bugs/show_bug.cgi?id=24585#c1">Comment # 1</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED INVALID - Constant folding disagrees with GCC and FPU on result of 0./0."
href="https://llvm.org/bugs/show_bug.cgi?id=24585">bug 24585</a>
from <span class="vcard"><a class="email" href="mailto:david.majnemer@gmail.com" title="David Majnemer <david.majnemer@gmail.com>"> <span class="fn">David Majnemer</span></a>
</span></b>
<pre>We constant fold 0/0 to a NaN without the sign bit while your processor
generates a NaN with the sign bit.
After consulting the C++ standard, there doesn't appear to be a restriction on
what sorts of NaNs we are permitted to give back for such expressions.
For example, consider:
#include <cmath>
#include <stdio.h>
int main() {
volatile double zerov = 0.0;
printf("%d %d\n", (int)std::signbit(zerov/zerov), (int)std::signbit(NAN));
}
This program prints out "1 0" for clang and GCC but "1 1" for MSVC 2015.</pre>
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