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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - InstCombine - extend matchRotate to handle funnel shifts"
href="https://bugs.llvm.org/show_bug.cgi?id=46896">46896</a>
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<th>Summary</th>
<td>InstCombine - extend matchRotate to handle funnel shifts
</td>
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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>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
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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<p>
<div>
<pre>matchRotate currently only matches rotations, but should be able to handle
funnel shifts as well with minimal effort:
define i64 @rotvar(i64 %a0, i64 %a1, i64 %a2) {
%m = and i64 %a2, 63
%n = sub i64 0, %m
%s = and i64 %n, 63
%1 = shl i64 %a0, %m
%2 = lshr i64 %a0, %s
%3 = or i64 %1, %2
ret i64 %3
}
define i64 @fshvar(i64 %a0, i64 %a1, i64 %a2) {
%m = and i64 %a2, 63
%n = sub i64 0, %m
%s = and i64 %n, 63
%1 = shl i64 %a0, %m
%2 = lshr i64 %a1, %s
%3 = or i64 %1, %2
ret i64 %3
}
opt -instcombine
define i64 @rotvar(i64 %a0, i64 %a1, i64 %a2) {
%1 = tail call i64 @llvm.fshl.i64(i64 %a0, i64 %a0, i64 %a2)
ret i64 %1
}
define i64 @fshvar(i64 %a0, i64 %a1, i64 %a2) {
%m = and i64 %a2, 63
%n = sub i64 0, %a2
%s = and i64 %n, 63
%1 = shl i64 %a0, %m
%2 = lshr i64 %a1, %s
%3 = or i64 %1, %2
ret i64 %3
}</pre>
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