Changeset 97294 in webkit for trunk/Source/JavaScriptCore/bytecode/CodeBlock.cpp

Timestamp:

Oct 12, 2011, 1:28:49 PM (14 years ago)

Author:

[email protected]

Message:

ValueProfile::computeUpdatedPrediction doesn't merge statistics correctly
​https://bugs.webkit.org/show_bug.cgi?id=69906

Reviewed by Gavin Barraclough.

It turns out that the simplest fix is to switch computeUpdatedPredictions()
to using predictionFromValue() combined with mergePrediction(). Doing so
allowed me to kill off weakBuckets and visitWeakReferences(). Hence this
not only fixes a performance bug but kills off a lot of code that I never
liked to begin with.

This appears to be a 1% win on V8.

• bytecode/CodeBlock.cpp:

(JSC::CodeBlock::visitAggregate):

• bytecode/CodeBlock.h:
• bytecode/PredictedType.cpp:

(JSC::predictionFromValue):

• bytecode/ValueProfile.cpp:

(JSC::ValueProfile::computeStatistics):
(JSC::ValueProfile::computeUpdatedPrediction):

• bytecode/ValueProfile.h:

(JSC::ValueProfile::classInfo):
(JSC::ValueProfile::numberOfSamples):
(JSC::ValueProfile::isLive):
(JSC::ValueProfile::dump):

File:

• trunk/Source/JavaScriptCore/bytecode/CodeBlock.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/bytecode/CodeBlock.cpp

@@ -1528 +1528 @@
 void CodeBlock::visitAggregate(SlotVisitor& visitor)
 {
-    bool handleWeakReferences = false;
-    
     if (!!m_alternative)
         m_alternative->visitAggregate(visitor);
@@ -1581 +1579 @@
 
 #if ENABLE(VALUE_PROFILER)
-    for (unsigned profileIndex = 0; profileIndex < numberOfValueProfiles(); ++profileIndex) {
-        ValueProfile* profile = valueProfile(profileIndex);
-        
-        for (unsigned index = 0; index < ValueProfile::numberOfBuckets; ++index) {
-            if (!profile->m_buckets[index]) {
-                if (!!profile->m_weakBuckets[index])
-                    handleWeakReferences = true;
-                continue;
-            }
-            
-            if (!JSValue::decode(profile->m_buckets[index]).isCell()) {
-                profile->m_weakBuckets[index] = ValueProfile::WeakBucket();
-                continue;
-            }
-            
-            handleWeakReferences = true;
-        }
-    }
-#endif
-    
-    if (handleWeakReferences)
-        visitor.addWeakReferenceHarvester(this);
-}
-
-void CodeBlock::visitWeakReferences(SlotVisitor&)
-{
-#if ENABLE(VALUE_PROFILER)
-    for (unsigned profileIndex = 0; profileIndex < numberOfValueProfiles(); ++profileIndex) {
-        ValueProfile* profile = valueProfile(profileIndex);
-        
-        for (unsigned index = 0; index < ValueProfile::numberOfBuckets; ++index) {
-            if (!!profile->m_buckets[index]) {
-                JSValue value = JSValue::decode(profile->m_buckets[index]);
-                if (!value.isCell())
-                    continue;
-                
-                JSCell* cell = value.asCell();
-                if (Heap::isMarked(cell))
-                    continue;
-                
-                profile->m_buckets[index] = JSValue::encode(JSValue());
-                profile->m_weakBuckets[index] = cell->structure();
-            }
-            
-            ValueProfile::WeakBucket weak = profile->m_weakBuckets[index];
-            if (!weak || weak.isClassInfo())
-                continue;
-            
-            ASSERT(weak.isStructure());
-            if (Heap::isMarked(weak.asStructure()))
-                continue;
-            
-            profile->m_weakBuckets[index] = weak.asStructure()->classInfo();
-        }
-    }
+    for (unsigned profileIndex = 0; profileIndex < numberOfValueProfiles(); ++profileIndex)
+        valueProfile(profileIndex)->computeUpdatedPrediction();
 #endif
 }