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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Unnecessary vxorps instructions"
href="http://llvm.org/bugs/show_bug.cgi?id=22024">22024</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Unnecessary vxorps instructions
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>tobias@grosser.es
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=13590" name="attach_13590" title="Test case">attachment 13590</a> <a href="attachment.cgi?id=13590&action=edit" title="Test case">[details]</a></span>
Test case
For the following code:
void foo(float *A, float *B, long x, long y) {
*B = y;
*A = x;
}
gcc -S -o - /tmp/test.c -O3 -mavx
vcvtsi2ssq %rcx, %xmm0, %xmm0
vmovss %xmm0, (%rsi)
vcvtsi2ssq %rdx, %xmm0, %xmm0
vmovss %xmm0, (%rdi)
ret
clang -S -o - /tmp/test.c -O3 -mavx
vcvtsi2ssq %rcx, %xmm0, %xmm0
vmovss %xmm0, (%rsi)
vxorps %xmm0, %xmm0, %xmm0
vcvtsi2ssq %rdx, %xmm0, %xmm0
vmovss %xmm0, (%rdi)
retq
The vxorps instruction is unnecessary.</pre>
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