Changeset 189516 in webkit for trunk/Source/JavaScriptCore/dfg/DFGPlan.h

Timestamp:

Sep 8, 2015, 5:07:51 PM (10 years ago)

Author:

[email protected]

Message:

GC should be able to discover new strong CodeBlock references during marking
​https://bugs.webkit.org/show_bug.cgi?id=148981

Reviewed by Mark Lam.

Previously, we required a strong reference to register itself before the
first visit to a CodeBlock. Now, we can discover a strong reference at
any time during the marking phase.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::CodeBlock): Remove the two strong reference state
variables from CodeBlock. Now, a strong reference immediately marks
the CodeBlock and its references at the moment of its discovery, and no
separate state is required.

(JSC::CodeBlock::visitStrongly): New helper function for establishing
a strong reference to a CodeBlock.

(JSC::CodeBlock::visitAggregate): Adopt helper function above.

(JSC::CodeBlock::shouldImmediatelyAssumeLivenessDuringScan): Updated
for state removal.

(JSC::CodeBlock::isKnownToBeLiveDuringGC): Ditto.

(JSC::CodeBlock::stronglyVisitWeakReferences): Be sure to record that
we have proven liveness (by virtue of marking all the references the
proof would check). This is required so that the CodeBlock knows itself
to be live, and it is also an optimization to avoid testing weak references
after we have already visited them.

• bytecode/CodeBlock.h:

(JSC::CodeBlock::clearMarks):
(JSC::CodeBlockSet::mark):
(JSC::CodeBlockSet::clearMarks): Deleted. Updated for state removal.

• dfg/DFGPlan.cpp:

(JSC::DFG::Plan::clearCodeBlockMarks):
(JSC::DFG::Plan::checkLivenessAndVisitChildren):

• dfg/DFGPlan.h: No need to use a CodeBlockSet in order to mark anymore.

• dfg/DFGWorklist.cpp:

(JSC::DFG::Worklist::completeAllPlansForVM):
(JSC::DFG::Worklist::clearCodeBlockMarks):
(JSC::DFG::Worklist::resumeAllThreads):
(JSC::DFG::Worklist::visitWeakReferences):
(JSC::DFG::completeAllPlansForVM):
(JSC::DFG::clearCodeBlockMarks):

• dfg/DFGWorklist.h:

(JSC::DFG::worklistForIndexOrNull): No need to use a CodeBlockSet in order
to mark anymore.

• heap/CodeBlockSet.cpp:

(JSC::CodeBlockSet::clearMarksForFullCollection):
(JSC::CodeBlockSet::clearMarksForEdenCollection):
(JSC::CodeBlockSet::deleteUnmarkedAndUnreferenced):
(JSC::CodeBlockSet::traceMarked):
(JSC::CodeBlockSet::rememberCurrentlyExecutingCodeBlocks):
(JSC::CodeBlockSet::dump):

• heap/CodeBlockSet.h: Keep the currently executing CodeBlocks in RefPtrs

since we can no longer rely on the m_currentlyExecuting bit to keep them
alive. (A currently executing CodeBlock may not be referenced by its
Executable because it may since have been replaced by another CodeBlock.
This is common in the cases of OSR entry and exit.)

• heap/Heap.cpp:

(JSC::Heap::markRoots):
(JSC::Heap::visitCompilerWorklistWeakReferences):
(JSC::Heap::visitWeakHandles): No need to trace the list of CodeBlocks
on the stack in the weak reference fixpoint because we no longer overload
"on the stack" to include CodeBlocks referenced by the compiler.

File:

• trunk/Source/JavaScriptCore/dfg/DFGPlan.h (modified) (2 diffs)

trunk/Source/JavaScriptCore/dfg/DFGPlan.h

@@ -45 +45 @@
 
 class CodeBlock;
-class CodeBlockSet;
 class SlotVisitor;
 
@@ -73 +72 @@
     CompilationKey key();
     
-    void clearCodeBlockMarks(CodeBlockSet&);
-    void checkLivenessAndVisitChildren(SlotVisitor&, CodeBlockSet&);
+    void clearCodeBlockMarks();
+    void checkLivenessAndVisitChildren(SlotVisitor&);
     bool isKnownToBeLiveDuringGC();
     void cancel();