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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86] __builtin_rotateright* does not use rotate by 1 instructions or rorx with bmi"
href="https://bugs.llvm.org/show_bug.cgi?id=41057">41057</a>
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<th>Summary</th>
<td>[X86] __builtin_rotateright* does not use rotate by 1 instructions or rorx with bmi
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Windows NT
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>craig.topper@gmail.com
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
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<p>
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<pre>The isel patterns for rotates by immediates are written assuming rotate by
immediate will always use a rotl operation because that's what the pattern
matching code from the shift+or pattern will do.
But the __builtin_rotateright* functions use the funnel shift intrinsics and
will be turned directly into rotr by SelectionDAGBuilder. This will miss most
of the patterns except the ror by immediate patterns.
Godbolt example showing both issues <a href="https://godbolt.org/z/7Tt1ki">https://godbolt.org/z/7Tt1ki</a></pre>
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