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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - UBSan breaks compilation of inline asm"
href="http://llvm.org/bugs/show_bug.cgi?id=20535">20535</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>UBSan breaks compilation of inline asm
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>vonosmas@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, richard-llvm@metafoo.co.uk
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>$ cat tmp/ubsan/asm.c
void clear_blocks_sse() {
__asm__ volatile (
"" : : "i"(128 * 6)
);
}
$ ./bin/clang -c -fsanitize=undefined tmp/ubsan/asm.c -o asm.o
tmp/ubsan/asm.c:3:9: error: invalid operand for inline asm constraint 'i'
"" : : "i"(128 * 6)
^
1 error generated.
This happens because 128 * 6 is not a compiled-time constant anymore - it is
instead a regular Value calculated by @llvm.smul.with.overflow.i32 intrinsic.
I'm not sure what is the best approach for fixing this. Should we check for
overflow statically if both operands of the checked binary op are constants?</pre>
</div>
</p>
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