Changeset 172737 in webkit for trunk/Source/JavaScriptCore/dfg/DFGGraph.cpp

Timestamp:

Aug 18, 2014, 5:55:31 PM (11 years ago)

Author:

[email protected]

Message:

REGRESSION(r172129): ftlopt branch merge made performance tests flakey crash
​https://bugs.webkit.org/show_bug.cgi?id=135750

Reviewed by Mark Lam.

This was caused by a rather embarrassing oversight in how the DFG tracks structures: we
could sometimes perform an optimization that requires a structure to be alive but forget to
ensure that the structure is actually kept alive. In particular, any watchpoint-based
optimizations involve setting watchpoints even if the code that got optimized is eventually
deleted because it is unreachable. All such optimizations would leave behind something in
the IR to tell us that we are interested in the structure and that therefore it should be
kept alive. But, IR can be deleted if it is unreachable.

The solution is to ensure that as soon as the DFG is made aware of a structure, it adds it
to the set of weak references.

• JavaScriptCore.xcodeproj/project.pbxproj:
• dfg/DFGAbstractInterpreterInlines.h:

(JSC::DFG::AbstractInterpreter<AbstractStateType>::executeEffects):

• dfg/DFGAbstractValue.cpp:

(JSC::DFG::AbstractValue::setOSREntryValue):
(JSC::DFG::AbstractValue::set):
(JSC::DFG::AbstractValue::normalizeClarity):
(JSC::DFG::AbstractValue::assertIsRegistered):
(JSC::DFG::AbstractValue::assertIsWatched): Deleted.

• dfg/DFGAbstractValue.h:

(JSC::DFG::AbstractValue::assertIsRegistered):
(JSC::DFG::AbstractValue::assertIsWatched): Deleted.

• dfg/DFGCommon.h:
• dfg/DFGConstantFoldingPhase.cpp:

(JSC::DFG::ConstantFoldingPhase::addStructureTransitionCheck):

• dfg/DFGDesiredWeakReferences.cpp:

(JSC::DFG::DesiredWeakReferences::addLazily):
(JSC::DFG::DesiredWeakReferences::contains):
(JSC::DFG::DesiredWeakReferences::reallyAdd):
(JSC::DFG::DesiredWeakReferences::visitChildren):

• dfg/DFGDesiredWeakReferences.h:
• dfg/DFGFixupPhase.cpp:

(JSC::DFG::FixupPhase::canOptimizeStringObjectAccess):

• dfg/DFGGraph.cpp:

(JSC::DFG::Graph::Graph):
(JSC::DFG::Graph::registerFrozenValues):
(JSC::DFG::Graph::convertToConstant):
(JSC::DFG::Graph::registerStructure):
(JSC::DFG::Graph::assertIsRegistered):
(JSC::DFG::Graph::assertIsWatched): Deleted.

• dfg/DFGGraph.h:
• dfg/DFGPlan.cpp:

(JSC::DFG::Plan::compileInThreadImpl):

• dfg/DFGStructureAbstractValue.cpp:

(JSC::DFG::StructureAbstractValue::assertIsRegistered):
(JSC::DFG::StructureAbstractValue::assertIsWatched): Deleted.

• dfg/DFGStructureAbstractValue.h:

(JSC::DFG::StructureAbstractValue::assertIsRegistered):
(JSC::DFG::StructureAbstractValue::assertIsWatched): Deleted.

• dfg/DFGStructureRegistrationPhase.cpp: Copied from Source/JavaScriptCore/dfg/DFGWatchableStructureWatchingPhase.cpp.

(JSC::DFG::StructureRegistrationPhase::StructureRegistrationPhase):
(JSC::DFG::StructureRegistrationPhase::run):
(JSC::DFG::StructureRegistrationPhase::registerStructures):
(JSC::DFG::StructureRegistrationPhase::registerStructure):
(JSC::DFG::performStructureRegistration):
(JSC::DFG::WatchableStructureWatchingPhase::WatchableStructureWatchingPhase): Deleted.
(JSC::DFG::WatchableStructureWatchingPhase::run): Deleted.
(JSC::DFG::WatchableStructureWatchingPhase::tryWatch): Deleted.
(JSC::DFG::performWatchableStructureWatching): Deleted.

• dfg/DFGStructureRegistrationPhase.h: Copied from Source/JavaScriptCore/dfg/DFGWatchableStructureWatchingPhase.h.
• dfg/DFGWatchableStructureWatchingPhase.cpp: Removed.
• dfg/DFGWatchableStructureWatchingPhase.h: Removed.

File:

• trunk/Source/JavaScriptCore/dfg/DFGGraph.cpp (modified) (4 diffs)

trunk/Source/JavaScriptCore/dfg/DFGGraph.cpp

@@ -66 +66 @@
     , m_machineCaptureStart(std::numeric_limits<int>::max())
     , m_fixpointState(BeforeFixpoint)
-    , m_structureWatchpointState(HaveNotStartedWatching)
+    , m_structureRegistrationState(HaveNotStartedRegistering)
     , m_form(LoadStore)
     , m_unificationState(LocallyUnified)
@@ -944 +944 @@
     m_codeBlock->constants().resize(0);
     for (FrozenValue* value : m_frozenValues) {
-        if (value->structure() && value->structure()->dfgShouldWatch())
-            m_plan.weakReferences.addLazily(value->structure());
+        if (value->structure())
+            ASSERT(m_plan.weakReferences.contains(value->structure()));
         
         switch (value->strength()) {
@@ -1072 +1072 @@
 {
     if (value->structure())
-        assertIsWatched(value->structure());
+        assertIsRegistered(value->structure());
     if (m_form == ThreadedCPS) {
         if (node->op() == GetLocal)
@@ -1092 +1092 @@
 }
 
-void Graph::assertIsWatched(Structure* structure)
-{
-    if (m_structureWatchpointState == HaveNotStartedWatching)
+StructureRegistrationResult Graph::registerStructure(Structure* structure)
+{
+    m_plan.weakReferences.addLazily(structure);
+    if (m_plan.watchpoints.consider(structure))
+        return StructureRegisteredAndWatched;
+    return StructureRegisteredNormally;
+}
+
+void Graph::assertIsRegistered(Structure* structure)
+{
+    if (m_structureRegistrationState == HaveNotStartedRegistering)
         return;
+    
+    DFG_ASSERT(*this, nullptr, m_plan.weakReferences.contains(structure));
     
     if (!structure->dfgShouldWatch())