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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/197491">197491</a></dd>
<dt>Author</dt> <dd>commit-queue@webkit.org</dd>
<dt>Date</dt> <dd>2016-03-02 21:29:16 -0800 (Wed, 02 Mar 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>[JSC] JSCell_freeListNext and JSCell_structureID are considered not overlapping
https://bugs.webkit.org/show_bug.cgi?id=154947
Patch by Benjamin Poulain <bpoulain@apple.com> on 2016-03-02
Reviewed by Filip Pizlo.
This bug was discovered while testing https://bugs.webkit.org/show_bug.cgi?id=154894.
The problem was that JSCell_freeListNext and JSCell_structureID were
considered as disjoint. When reordering instructions, the scheduler
could move the write of the StructureID first to reduce dependencies.
This would erase half of JSCell_freeListNext before we get a chance
to load the value.
This patch changes the hierarchy to make sure nothing is written
until JSCell_freeListNext is processed.
All credits for this patch go to Filip.
* ftl/FTLAbstractHeapRepository.cpp:
(JSC::FTL::AbstractHeapRepository::AbstractHeapRepository):
* ftl/FTLAbstractHeapRepository.h:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreftlFTLAbstractHeapRepositorycpp">trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreftlFTLAbstractHeapRepositoryh">trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.h</a></li>
</ul>
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<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (197490 => 197491)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-03-03 05:19:02 UTC (rev 197490)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-03-03 05:29:16 UTC (rev 197491)
</span><span class="lines">@@ -1,5 +1,29 @@
</span><span class="cx"> 2016-03-02 Benjamin Poulain <bpoulain@apple.com>
</span><span class="cx">
</span><ins>+ [JSC] JSCell_freeListNext and JSCell_structureID are considered not overlapping
+ https://bugs.webkit.org/show_bug.cgi?id=154947
+
+ Reviewed by Filip Pizlo.
+
+ This bug was discovered while testing https://bugs.webkit.org/show_bug.cgi?id=154894.
+
+ The problem was that JSCell_freeListNext and JSCell_structureID were
+ considered as disjoint. When reordering instructions, the scheduler
+ could move the write of the StructureID first to reduce dependencies.
+ This would erase half of JSCell_freeListNext before we get a chance
+ to load the value.
+
+ This patch changes the hierarchy to make sure nothing is written
+ until JSCell_freeListNext is processed.
+
+ All credits for this patch go to Filip.
+
+ * ftl/FTLAbstractHeapRepository.cpp:
+ (JSC::FTL::AbstractHeapRepository::AbstractHeapRepository):
+ * ftl/FTLAbstractHeapRepository.h:
+
+2016-03-02 Benjamin Poulain <bpoulain@apple.com>
+
</ins><span class="cx"> [JSC] Improve Select of Doubles based on Double condition
</span><span class="cx"> https://bugs.webkit.org/show_bug.cgi?id=154572
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreftlFTLAbstractHeapRepositorycpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.cpp (197490 => 197491)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.cpp 2016-03-03 05:19:02 UTC (rev 197490)
+++ trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.cpp 2016-03-03 05:29:16 UTC (rev 197491)
</span><span class="lines">@@ -57,7 +57,7 @@
</span><span class="cx"> FOR_EACH_ABSTRACT_FIELD(ABSTRACT_FIELD_INITIALIZATION)
</span><span class="cx"> #undef ABSTRACT_FIELD_INITIALIZATION
</span><span class="cx">
</span><del>- , JSCell_freeListNext(JSCell_structureID)
</del><ins>+ , JSCell_freeListNext(JSCell_header)
</ins><span class="cx">
</span><span class="cx"> #define INDEXED_ABSTRACT_HEAP_INITIALIZATION(name, offset, size) , name(&root, #name, offset, size)
</span><span class="cx"> FOR_EACH_INDEXED_ABSTRACT_HEAP(INDEXED_ABSTRACT_HEAP_INITIALIZATION)
</span><span class="lines">@@ -75,6 +75,8 @@
</span><span class="cx"> RELEASE_ASSERT(JSCell_indexingType.offset() + 2 == JSCell_typeInfoFlags.offset());
</span><span class="cx"> RELEASE_ASSERT(JSCell_indexingType.offset() + 3 == JSCell_cellState.offset());
</span><span class="cx">
</span><ins>+ JSCell_structureID.changeParent(&JSCell_header);
+ JSCell_usefulBytes.changeParent(&JSCell_header);
</ins><span class="cx"> JSCell_indexingType.changeParent(&JSCell_usefulBytes);
</span><span class="cx"> JSCell_typeInfoType.changeParent(&JSCell_usefulBytes);
</span><span class="cx"> JSCell_typeInfoFlags.changeParent(&JSCell_usefulBytes);
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreftlFTLAbstractHeapRepositoryh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.h (197490 => 197491)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.h 2016-03-03 05:19:02 UTC (rev 197490)
+++ trunk/Source/JavaScriptCore/ftl/FTLAbstractHeapRepository.h 2016-03-03 05:29:16 UTC (rev 197491)
</span><span class="lines">@@ -54,6 +54,7 @@
</span><span class="cx"> macro(JSArrayBufferView_mode, JSArrayBufferView::offsetOfMode()) \
</span><span class="cx"> macro(JSArrayBufferView_vector, JSArrayBufferView::offsetOfVector()) \
</span><span class="cx"> macro(JSCell_cellState, JSCell::cellStateOffset()) \
</span><ins>+ macro(JSCell_header, 0) \
</ins><span class="cx"> macro(JSCell_indexingType, JSCell::indexingTypeOffset()) \
</span><span class="cx"> macro(JSCell_structureID, JSCell::structureIDOffset()) \
</span><span class="cx"> macro(JSCell_typeInfoFlags, JSCell::typeInfoFlagsOffset()) \
</span></span></pre>
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