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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [InstCombine] Failure to form funnel shifts for (shl ShVal, X) | (lshr ShVal, (Width - x)) when (Width - x) has multiple uses like for another funnel shift"
href="https://bugs.llvm.org/show_bug.cgi?id=47795">47795</a>
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<th>Summary</th>
<td>[InstCombine] Failure to form funnel shifts for (shl ShVal, X) | (lshr ShVal, (Width - x)) when (Width - x) has multiple uses like for another funnel shift
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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
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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>Scalar Optimizations
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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>llvm-bugs@lists.llvm.org
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</tr></table>
<p>
<div>
<pre>As shown here <a href="https://skanthak.homepage.t-online.de/llvm.html#case21">https://skanthak.homepage.t-online.de/llvm.html#case21</a> or
<a href="https://godbolt.org/z/s4bGGs">https://godbolt.org/z/s4bGGs</a>
Removing the m_OneUse here
- if (match(R, m_OneUse(m_Sub(m_SpecificInt(Width), m_Specific(L))))) {
+ if (match(R, m_Sub(m_SpecificInt(Width), m_Specific(L)))) {
Allows a funnel shift to be generated in bb.20
I suppose removing this may be bad if the target doesn't support funnel shift
natively?</pre>
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