Changeset 144131 in webkit for trunk/Source/JavaScriptCore/dfg/DFGVariableAccessData.h

Timestamp:

Feb 26, 2013, 5:45:28 PM (12 years ago)

Author:

[email protected]

Message:

The DFG backend's and OSR's decision to unbox a variable should be based on whether it's used in a typed context
​https://bugs.webkit.org/show_bug.cgi?id=110433

Reviewed by Oliver Hunt and Mark Hahnenberg.

This introduces the equivalent of a liveness analysis, except for type checking.
A variable is said to be "profitable for unboxing" (i.e. live at a type check)
if there exists a type check on a GetLocal of that variable, and the type check
is consistent with the variable's prediction. Variables that are not profitable
for unboxing aren't unboxed. Previously they would have been.

This is a slight speed-up on some things but mostly neutral.

• dfg/DFGArgumentPosition.h:

(JSC::DFG::ArgumentPosition::ArgumentPosition):
(JSC::DFG::ArgumentPosition::mergeShouldNeverUnbox):
(JSC::DFG::ArgumentPosition::mergeArgumentPredictionAwareness):
(JSC::DFG::ArgumentPosition::mergeArgumentUnboxingAwareness):
(ArgumentPosition):
(JSC::DFG::ArgumentPosition::isProfitableToUnbox):
(JSC::DFG::ArgumentPosition::shouldUseDoubleFormat):

• dfg/DFGCommon.h:

(JSC::DFG::checkAndSet):
(DFG):

• dfg/DFGFixupPhase.cpp:

(JSC::DFG::FixupPhase::run):
(JSC::DFG::FixupPhase::fixupNode):
(JSC::DFG::FixupPhase::fixupSetLocalsInBlock):
(FixupPhase):
(JSC::DFG::FixupPhase::alwaysUnboxSimplePrimitives):
(JSC::DFG::FixupPhase::setUseKindAndUnboxIfProfitable):

• dfg/DFGPredictionPropagationPhase.cpp:

(JSC::DFG::PredictionPropagationPhase::doRoundOfDoubleVoting):

• dfg/DFGSpeculativeJIT.cpp:

(JSC::DFG::SpeculativeJIT::checkArgumentTypes):

• dfg/DFGVariableAccessData.h:

(JSC::DFG::VariableAccessData::VariableAccessData):
(JSC::DFG::VariableAccessData::mergeIsCaptured):
(JSC::DFG::VariableAccessData::mergeIsProfitableToUnbox):
(VariableAccessData):
(JSC::DFG::VariableAccessData::isProfitableToUnbox):
(JSC::DFG::VariableAccessData::shouldUnboxIfPossible):
(JSC::DFG::VariableAccessData::mergeStructureCheckHoistingFailed):
(JSC::DFG::VariableAccessData::mergeIsArgumentsAlias):
(JSC::DFG::VariableAccessData::shouldUseDoubleFormat):
(JSC::DFG::VariableAccessData::mergeFlags):

File:

• trunk/Source/JavaScriptCore/dfg/DFGVariableAccessData.h (modified) (10 diffs)

trunk/Source/JavaScriptCore/dfg/DFGVariableAccessData.h

@@ -1 +1 @@
 /*
- * Copyright (C) 2011, 2012 Apple Inc. All rights reserved.
+ * Copyright (C) 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -51 +51 @@
         , m_isArgumentsAlias(false)
         , m_structureCheckHoistingFailed(false)
+        , m_isProfitableToUnbox(false)
         , m_doubleFormatState(EmptyDoubleFormatState)
     {
@@ -65 +66 @@
         , m_isArgumentsAlias(false)
         , m_structureCheckHoistingFailed(false)
+        , m_isProfitableToUnbox(false)
         , m_doubleFormatState(EmptyDoubleFormatState)
     {
@@ -83 +85 @@
     bool mergeIsCaptured(bool isCaptured)
     {
-        m_shouldNeverUnbox |= isCaptured;
-        bool newIsCaptured = m_isCaptured | isCaptured;
-        if (newIsCaptured == m_isCaptured)
-            return false;
-        m_isCaptured = newIsCaptured;
-        return true;
+        return checkAndSet(m_shouldNeverUnbox, m_shouldNeverUnbox | isCaptured)
+            | checkAndSet(m_isCaptured, m_isCaptured | isCaptured);
     }
     
@@ -94 +92 @@
     {
         return m_isCaptured;
+    }
+    
+    bool mergeIsProfitableToUnbox(bool isProfitableToUnbox)
+    {
+        return checkAndSet(m_isProfitableToUnbox, m_isProfitableToUnbox | isProfitableToUnbox);
+    }
+    
+    bool isProfitableToUnbox()
+    {
+        return m_isProfitableToUnbox;
     }
     
@@ -119 +127 @@
     bool shouldUnboxIfPossible()
     {
-        return !shouldNeverUnbox();
-    }
-    
+        return !shouldNeverUnbox() && isProfitableToUnbox();
+    }
+
     bool mergeStructureCheckHoistingFailed(bool failed)
     {
-        bool newFailed = m_structureCheckHoistingFailed | failed;
-        if (newFailed == m_structureCheckHoistingFailed)
-            return false;
-        m_structureCheckHoistingFailed = newFailed;
-        return true;
+        return checkAndSet(m_structureCheckHoistingFailed, m_structureCheckHoistingFailed | failed);
     }
     
@@ -138 +142 @@
     bool mergeIsArgumentsAlias(bool isArgumentsAlias)
     {
-        bool newIsArgumentsAlias = m_isArgumentsAlias | isArgumentsAlias;
-        if (newIsArgumentsAlias == m_isArgumentsAlias)
-            return false;
-        m_isArgumentsAlias = newIsArgumentsAlias;
-        return true;
+        return checkAndSet(m_isArgumentsAlias, m_isArgumentsAlias | isArgumentsAlias);
     }
     
@@ -240 +240 @@
     {
         ASSERT(isRoot());
-        bool result = m_doubleFormatState == UsingDoubleFormat;
-        ASSERT(!(result && shouldNeverUnbox()));
-        ASSERT(!(result && isCaptured()));
-        return result;
+        bool doubleState = m_doubleFormatState == UsingDoubleFormat;
+        ASSERT(!(doubleState && shouldNeverUnbox()));
+        ASSERT(!(doubleState && isCaptured()));
+        return doubleState && isProfitableToUnbox();
     }
     
@@ -288 +288 @@
     bool mergeFlags(NodeFlags newFlags)
     {
-        newFlags |= m_flags;
-        if (newFlags == m_flags)
-            return false;
-        m_flags = newFlags;
-        return true;
+        return checkAndSet(m_flags, m_flags | newFlags);
     }
     
@@ -305 +301 @@
     SpeculatedType m_argumentAwarePrediction;
     NodeFlags m_flags;
-    
+
     bool m_isCaptured;
     bool m_shouldNeverUnbox;
     bool m_isArgumentsAlias;
     bool m_structureCheckHoistingFailed;
+    bool m_isProfitableToUnbox;
 
     float m_votes[2]; // Used primarily for double voting but may be reused for other purposes.