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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - LowerToAir should recognize subwidth variants of Equal(StrongCAS...)"
href="https://bugs.webkit.org/show_bug.cgi?id=169250">169250</a>
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<th>Summary</th>
<td>LowerToAir should recognize subwidth variants of Equal(StrongCAS...)
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<th>Classification</th>
<td>Unclassified
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<th>Product</th>
<td>WebKit
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<th>Version</th>
<td>WebKit Nightly Build
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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
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<th>Severity</th>
<td>Normal
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>JavaScriptCore
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>fpizlo@apple.com
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<pre>We currently don't turn Equal(StrongCAS...) into a direct branch on the CAS result for Width8 and Width16. We can do it. We'd have to match patterns like:
Equal(SExt8(StrongCAS(@exp, ...)), SExt8(@exp))
and
Equal(SExt8(StrongCAS(BitAnd(@exp, 0xff), ...)), SExt8(@exp))
Where the right-hand SExt8 is matched with sharing.
It's not super obvious how profitable this optimization will be, particularly if we have any optimizations that turn strong CAS into weak CAS.</pre>
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