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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [x86] __builtin_writeeflags_u32/__builtin_readeflags_u32 should not be available in 64-bit mode"
href="https://bugs.llvm.org/show_bug.cgi?id=37225">37225</a>
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<th>Summary</th>
<td>[x86] __builtin_writeeflags_u32/__builtin_readeflags_u32 should not be available in 64-bit mode
</td>
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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>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>LLVM Codegen
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>craig.topper@gmail.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<pre>The backend cannot isel these correctly and probably shouldn't try. For the
writeeflags we won't have enough input data to write the whole 64-bit RFLAGS
register. This would fine in CPL 3 where the upper bits aren't writable. But in
CPL 0 the bits are writable so we need to ensure the user provided enough bits.</pre>
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