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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 --- - Multiplying vector type by a floating point constant results in an invalid result"
href="http://llvm.org/bugs/show_bug.cgi?id=16063">16063</a>
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<th>Summary</th>
<td>Multiplying vector type by a floating point constant results in an invalid result
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>LLVM Codegen
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>georgellvmb@oss3d.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Please check the code below. A float vector is multiplied by a double constant.
When the vector size is changed to 4, the code even fails to compile. However
for size 2 it compiles and gives the following wrong results.
>From my analysis of the code, a bitcast instruction is used in LLVM code
generator, which (I presume) simply reinterprets double constant instead of
converting it.
===== EXPECTED OUTPUT:
ORIGINAL: 1.00,1.00
MULTIPLIED: 0.50,0.50
===== ACTUAL OUTPUT:
ORIGINAL: 1.00,1.00
MULTIPLIED: 0.00,1.75
===== CODE:
#include <stdio.h>
#include <math.h>
typedef float tfloat __attribute__((ext_vector_type(2)))
__attribute__((aligned(8))) ;
int main()
{
tfloat orig=1.0;
printf("ORIGINAL: %.2lf,%.2lf\n",(double)orig[0],(double)orig[1]);
orig = orig*0.5;
printf("MULTIPLIED: %.2lf,%.2lf\n",(double)orig[0],(double)orig[1]);
return 0;
}</pre>
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