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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/189707">189707</a></dd>
<dt>Author</dt> <dd>carlosgc@webkit.org</dd>
<dt>Date</dt> <dd>2015-09-14 03:38:47 -0700 (Mon, 14 Sep 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/188978">r188978</a> - [JSC] StructureTransitionTable should eagerly deallocate single-transition WeakImpls.
<https://webkit.org/b/148478>
Reviewed by Geoffrey Garen.
Use a WeakHandleOwner to eagerly deallocate StructureTransitionTable's Weak pointers
when it's using the single-transition optimization and the Structure it transitioned
to has been GC'd.
This prevents Structures from keeping WeakBlocks alive longer than necessary when
they've been transitioned away from but are still in use themselves.
* runtime/Structure.cpp:
(JSC::singleSlotTransitionWeakOwner):
(JSC::StructureTransitionTable::singleTransition):
(JSC::StructureTransitionTable::setSingleTransition):
(JSC::StructureTransitionTable::add):
* runtime/StructureTransitionTable.h:
(JSC::StructureTransitionTable::singleTransition): Deleted.
(JSC::StructureTransitionTable::setSingleTransition): Deleted.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#releasesWebKitGTKwebkit210SourceJavaScriptCoreChangeLog">releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#releasesWebKitGTKwebkit210SourceJavaScriptCoreruntimeStructurecpp">releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/Structure.cpp</a></li>
<li><a href="#releasesWebKitGTKwebkit210SourceJavaScriptCoreruntimeStructureTransitionTableh">releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/StructureTransitionTable.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="releasesWebKitGTKwebkit210SourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/ChangeLog (189706 => 189707)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/ChangeLog 2015-09-14 10:10:53 UTC (rev 189706)
+++ releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/ChangeLog 2015-09-14 10:38:47 UTC (rev 189707)
</span><span class="lines">@@ -1,3 +1,26 @@
</span><ins>+2015-08-26 Andreas Kling <akling@apple.com>
+
+ [JSC] StructureTransitionTable should eagerly deallocate single-transition WeakImpls.
+ <https://webkit.org/b/148478>
+
+ Reviewed by Geoffrey Garen.
+
+ Use a WeakHandleOwner to eagerly deallocate StructureTransitionTable's Weak pointers
+ when it's using the single-transition optimization and the Structure it transitioned
+ to has been GC'd.
+
+ This prevents Structures from keeping WeakBlocks alive longer than necessary when
+ they've been transitioned away from but are still in use themselves.
+
+ * runtime/Structure.cpp:
+ (JSC::singleSlotTransitionWeakOwner):
+ (JSC::StructureTransitionTable::singleTransition):
+ (JSC::StructureTransitionTable::setSingleTransition):
+ (JSC::StructureTransitionTable::add):
+ * runtime/StructureTransitionTable.h:
+ (JSC::StructureTransitionTable::singleTransition): Deleted.
+ (JSC::StructureTransitionTable::setSingleTransition): Deleted.
+
</ins><span class="cx"> 2015-08-23 Benjamin Poulain <bpoulain@apple.com>
</span><span class="cx">
</span><span class="cx"> [JSC] Reduce the memory usage of BytecodeLivenessAnalysis
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit210SourceJavaScriptCoreruntimeStructurecpp"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/Structure.cpp (189706 => 189707)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/Structure.cpp 2015-09-14 10:10:53 UTC (rev 189706)
+++ releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/Structure.cpp 2015-09-14 10:38:47 UTC (rev 189707)
</span><span class="lines">@@ -38,6 +38,7 @@
</span><span class="cx"> #include "StructureRareDataInlines.h"
</span><span class="cx"> #include "WeakGCMapInlines.h"
</span><span class="cx"> #include <wtf/CommaPrinter.h>
</span><ins>+#include <wtf/NeverDestroyed.h>
</ins><span class="cx"> #include <wtf/ProcessID.h>
</span><span class="cx"> #include <wtf/RefCountedLeakCounter.h>
</span><span class="cx"> #include <wtf/RefPtr.h>
</span><span class="lines">@@ -60,6 +61,41 @@
</span><span class="cx"> static HashSet<Structure*>& liveStructureSet = *(new HashSet<Structure*>);
</span><span class="cx"> #endif
</span><span class="cx">
</span><ins>+class SingleSlotTransitionWeakOwner final : public WeakHandleOwner {
+ void finalize(Handle<Unknown>, void* context) override
+ {
+ StructureTransitionTable* table = reinterpret_cast<StructureTransitionTable*>(context);
+ ASSERT(table->isUsingSingleSlot());
+ WeakSet::deallocate(table->weakImpl());
+ table->m_data = StructureTransitionTable::UsingSingleSlotFlag;
+ }
+};
+
+static SingleSlotTransitionWeakOwner& singleSlotTransitionWeakOwner()
+{
+ static NeverDestroyed<SingleSlotTransitionWeakOwner> owner;
+ return owner;
+}
+
+inline Structure* StructureTransitionTable::singleTransition() const
+{
+ ASSERT(isUsingSingleSlot());
+ if (WeakImpl* impl = this->weakImpl()) {
+ if (impl->state() == WeakImpl::Live)
+ return jsCast<Structure*>(impl->jsValue().asCell());
+ }
+ return nullptr;
+}
+
+inline void StructureTransitionTable::setSingleTransition(Structure* structure)
+{
+ ASSERT(isUsingSingleSlot());
+ if (WeakImpl* impl = this->weakImpl())
+ WeakSet::deallocate(impl);
+ WeakImpl* impl = WeakSet::allocate(structure, &singleSlotTransitionWeakOwner(), this);
+ m_data = reinterpret_cast<intptr_t>(impl) | UsingSingleSlotFlag;
+}
+
</ins><span class="cx"> bool StructureTransitionTable::contains(UniquedStringImpl* rep, unsigned attributes) const
</span><span class="cx"> {
</span><span class="cx"> if (isUsingSingleSlot()) {
</span><span class="lines">@@ -85,7 +121,7 @@
</span><span class="cx">
</span><span class="cx"> // This handles the first transition being added.
</span><span class="cx"> if (!existingTransition) {
</span><del>- setSingleTransition(vm, structure);
</del><ins>+ setSingleTransition(structure);
</ins><span class="cx"> return;
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit210SourceJavaScriptCoreruntimeStructureTransitionTableh"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/StructureTransitionTable.h (189706 => 189707)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/StructureTransitionTable.h 2015-09-14 10:10:53 UTC (rev 189706)
+++ releases/WebKitGTK/webkit-2.10/Source/JavaScriptCore/runtime/StructureTransitionTable.h 2015-09-14 10:38:47 UTC (rev 189707)
</span><span class="lines">@@ -134,6 +134,8 @@
</span><span class="cx"> Structure* get(UniquedStringImpl*, unsigned attributes) const;
</span><span class="cx">
</span><span class="cx"> private:
</span><ins>+ friend class SingleSlotTransitionWeakOwner;
+
</ins><span class="cx"> bool isUsingSingleSlot() const
</span><span class="cx"> {
</span><span class="cx"> return m_data & UsingSingleSlotFlag;
</span><span class="lines">@@ -164,24 +166,8 @@
</span><span class="cx"> ASSERT(!isUsingSingleSlot());
</span><span class="cx"> }
</span><span class="cx">
</span><del>- Structure* singleTransition() const
- {
- ASSERT(isUsingSingleSlot());
- if (WeakImpl* impl = this->weakImpl()) {
- if (impl->state() == WeakImpl::Live)
- return reinterpret_cast<Structure*>(impl->jsValue().asCell());
- }
- return 0;
- }
-
- void setSingleTransition(VM&, Structure* structure)
- {
- ASSERT(isUsingSingleSlot());
- if (WeakImpl* impl = this->weakImpl())
- WeakSet::deallocate(impl);
- WeakImpl* impl = WeakSet::allocate(reinterpret_cast<JSCell*>(structure));
- m_data = reinterpret_cast<intptr_t>(impl) | UsingSingleSlotFlag;
- }
</del><ins>+ Structure* singleTransition() const;
+ void setSingleTransition(Structure*);
</ins><span class="cx">
</span><span class="cx"> intptr_t m_data;
</span><span class="cx"> };
</span></span></pre>
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