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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - __attribute__((preserve_most)) saves 64-bit registers on 32-bit builds."
href="https://bugs.llvm.org/show_bug.cgi?id=40413">40413</a>
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<th>Summary</th>
<td>__attribute__((preserve_most)) saves 64-bit registers on 32-bit builds.
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
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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>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>brian.peter.ledger@gmail.com
</td>
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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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<p>
<div>
<pre>Building
```
void foo();
__attribute__((preserve_most))
int bar(int num) {
foo();
return 0;
}
```
produces the expected pushl and popl commands for saving registers. However,
they are ranging over the set of 64-bit registers, even when -m32 is passed.
If you inspect at line 290 of llvm/lib/Target/X86/X86RegisterInfo.cpp in the
repository, you will see it is referring to the constant
CSR_64_RT_MostRegs_SaveList, which is the set of 64-bit registers.
This will cause the assembler to fail, citing invalid registers, for all 32-bit
targets that use __attribute__((preserve_most)).</pre>
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