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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Poor codegen for char loads/compares on arm64"
href="https://bugs.llvm.org/show_bug.cgi?id=48555">48555</a>
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<th>Summary</th>
<td>Poor codegen for char loads/compares on arm64
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>Macintosh
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<th>OS</th>
<td>MacOS X
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>per.vognsen@gmail.com
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>Here is a repro with a .c file and the corresponding .s file built with clang
-O3 -c -S: <a href="https://gist.github.com/pervognsen/e1a5ba99ede4b630ed08df8ded87f27e">https://gist.github.com/pervognsen/e1a5ba99ede4b630ed08df8ded87f27e</a>
These redundant instructions are the issue:
and w9, w9, #0xff
The defs for w9 are ldrb instructions, so there is no need for these masking
operations before the compares.
(This issue was first discovered with Apple's build of clang that ships in the
latest Xcode toolchain, but I reproduced it with a self-built version from
trunk.)</pre>
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