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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [AArch64] Clang incorrectly warns with %wX register constraints"
href="http://llvm.org/bugs/show_bug.cgi?id=21270">21270</a>
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<th>Summary</th>
<td>[AArch64] Clang incorrectly warns with %wX register constraints
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>Other
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Frontend
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>james.molloy@arm.com
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Hi,
The following function provokes a warning on Clang trunk, 3.5, and AppleClang
based on 3.4:
void g(int one, int two) {
long wide_two = two;
asm ("%w0 %1" : "+r" (one), "+r"(wide_two));
}
/Users/jammol01/Code/test.c:3:25: warning: value size does not match register
size specified by the constraint and modifier
[-Wasm-operand-widths]
asm ("%w0 %1" : "+r" (one), "+r"(wide_two));
^
/Users/jammol01/Code/test.c:3:13: note: use constraint modifier "w"
asm ("%w0 %1" : "+r" (one), "+r"(wide_two));
^~
%w1
Obviously this warning is wrong - the second parameter is of type long
(64-bit). This spurious warning is affected by the type of "one" - if I change
"one" to "wide_one" (64-bit extended version) and remove the %w qualifier, it
compiles fine.
Cheers,
James</pre>
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