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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [JSC] The implementation of 8 bit operation in MacroAssembler should care about uint8_t / int8_t"
href="https://bugs.webkit.org/show_bug.cgi?id=164432">164432</a>
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<th>Summary</th>
<td>[JSC] The implementation of 8 bit operation in MacroAssembler should care about uint8_t / int8_t
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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>Unspecified
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<th>OS</th>
<td>Unspecified
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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>utatane.tea@gmail.com
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<p>
<div>
<pre>In r203331, we fixed some bugs.
But the behavior is not changed. We just drop the meaningless assertions.
However, MacroAssembler still has a bug.
In ARM, ARM64 assemblers, 8bit operations are implementation like this.
Jump branch8(RelationCondition cord, Address left, TrustedImm32 right)
{
TrustedImm32 right8(static_cast<int8_t>(right.m_value));
load8(left, getCachedMemoryTempRegisterIDAndInvalidate());
return branch32(cone, memoryTempRegister, right8);
}
The problem is, load8 does not perform sign extension. So if you pass signed 8bit value in |right|, the above code has a bad time. 32bit extended values becomes different. One is sign extended, another is not.</pre>
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