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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - BitXor(Comparison, 1) where canBeInternal(Comparison) should be generated as an inverted comparison"
href="https://bugs.webkit.org/show_bug.cgi?id=152367">152367</a>
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<th>Summary</th>
<td>BitXor(Comparison, 1) where canBeInternal(Comparison) should be generated as an inverted comparison
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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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<p>
<div>
<pre>This is relevant for float comparisons. Some of them will start as something like:
Equal(EqualOrUnordered(left, right), 0)
Then we will canonicalize this to:
BitXor(EqualOrUnordered(left, right), 1)
But then the code generator will emit the BitXor separately, so we'll have some nasty code to perform the comparison followed by a xor. That's goofy.
Note that this problem goes away if we also do branch fusion. For example both of these are fine:
Branch(BitXor(EqualOrUnordered(left, right), 1))
Check(BitXor(EqualOrUnordered(left, right), 1))
We won't see the Branch case because of strength reduction, but we will see the Check case, and that's OK - we'll chew through the BitXor.</pre>
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