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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Wrong optimization with ppc_fp128: 1 - 1 -> -0"
href="https://bugs.llvm.org/show_bug.cgi?id=45211">45211</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Wrong optimization with ppc_fp128: 1 - 1 -> -0
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>ch3root@openwall.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>For a PowerPC target, with the type long double (IBM extended double /
double-double / ppc_fp128) expression `1 - 1` is folded to `-0` instead of
`+0`. This type is not IEEE 754 type but for values representable in double the
results should be the same, I guess?
----------------------------------------------------------------------
#include <stdio.h>
int main()
{
long double x = 1;
printf("%Lg\n", x - 1);
}
----------------------------------------------------------------------
$ clang -target ppc64-linux-gnu -std=c11 -Weverything test.c && qemu-ppc64
/usr/powerpc-linux-gnu/lib64/ld64.so.1 --library-path
/usr/powerpc-linux-gnu/lib64 ./a.out
0
$ clang -target ppc64-linux-gnu -std=c11 -Weverything -O3 test.c && qemu-ppc64
/usr/powerpc-linux-gnu/lib64/ld64.so.1 --library-path
/usr/powerpc-linux-gnu/lib64 ./a.out
-0
----------------------------------------------------------------------
clang x86-64 version: clang version 11.0.0
(<a href="https://github.com/llvm/llvm-project">https://github.com/llvm/llvm-project</a> 429d792f23f2e72628cae763667bca60d69853e7)
----------------------------------------------------------------------</pre>
</div>
</p>
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