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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - MCExpr evaluation shouldn't always be signed"
href="https://llvm.org/bugs/show_bug.cgi?id=23227">23227</a>
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<th>Summary</th>
<td>MCExpr evaluation shouldn't always be signed
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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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
</td>
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<th>Component</th>
<td>MC
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>ahmed.bougacha@gmail.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>Consider:
echo 'movz x1, ((0xfffffffffffffffc & 0xffff000000000000) >> 48), LSL #48' |
llvm-mc -arch aarch64
<stdin>:1:10: error: immediate must be an integer in range [0, 65535].
movz x1, ((0xfffffffffffffffc & 0xffff000000000000) >> 48), LSL #48
That's not true with a logical shift, but MCExpr evaluation works on int64_t,
and propagates the "sign" bit.
There's a FIXME for this, but, to my knowledge, no PR:
// FIXME: We need target hooks for the evaluation. It may be limited in
// width, and gas defines the result of comparisons and right shifts
// differently from Apple as.</pre>
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