Changeset 201176 in webkit

Timestamp:

May 19, 2016, 1:09:47 PM (9 years ago)

Author:

sbarati@apple.com

Message:

arrow function lexical environment should reuse the same environment as the function's lexical environment where possible
​https://bugs.webkit.org/show_bug.cgi?id=157908

Reviewed by Filip Pizlo.

We can safely combine these two environment when we have
a simple parameter list (no default parameters, no destructring parameters).

• bytecompiler/BytecodeGenerator.cpp:

(JSC::BytecodeGenerator::BytecodeGenerator):
(JSC::BytecodeGenerator::initializeDefaultParameterValuesAndSetupFunctionScopeStack):
(JSC::BytecodeGenerator::initializeArrowFunctionContextScopeIfNeeded):

• bytecompiler/BytecodeGenerator.h:

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• bytecompiler/BytecodeGenerator.cpp (modified) (2 diffs)
• bytecompiler/BytecodeGenerator.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2016-05-19  Saam barati  <sbarati@apple.com>
+
+        arrow function lexical environment should reuse the same environment as the function's lexical environment where possible
+        https://bugs.webkit.org/show_bug.cgi?id=157908
+
+        Reviewed by Filip Pizlo.
+
+        We can safely combine these two environment when we have
+        a simple parameter list (no default parameters, no destructring parameters).
+
+        * bytecompiler/BytecodeGenerator.cpp:
+        (JSC::BytecodeGenerator::BytecodeGenerator):
+        (JSC::BytecodeGenerator::initializeDefaultParameterValuesAndSetupFunctionScopeStack):
+        (JSC::BytecodeGenerator::initializeArrowFunctionContextScopeIfNeeded):
+        * bytecompiler/BytecodeGenerator.h:
+
 2016-05-19  Michael Saboff  <msaboff@apple.com>
 

trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp

@@ -576 +576 @@
 
     if (needsToUpdateArrowFunctionContext() && !codeBlock->isArrowFunction()) {
-        initializeArrowFunctionContextScopeIfNeeded();
+        bool canReuseLexicalEnvironment = isSimpleParameterList;
+        initializeArrowFunctionContextScopeIfNeeded(functionSymbolTable, canReuseLexicalEnvironment);
         emitPutThisToArrowFunctionContextScope();
         emitPutNewTargetToArrowFunctionContextScope();
@@ -894 +895 @@
 }
 
-void BytecodeGenerator::initializeArrowFunctionContextScopeIfNeeded()
+void BytecodeGenerator::initializeArrowFunctionContextScopeIfNeeded(SymbolTable* functionSymbolTable, bool canReuseLexicalEnvironment)
 {
     ASSERT(!m_arrowFunctionContextLexicalEnvironmentRegister);
+
+    if (canReuseLexicalEnvironment && m_lexicalEnvironmentRegister) {
+        RELEASE_ASSERT(!m_codeBlock->isArrowFunction());
+        RELEASE_ASSERT(functionSymbolTable);
+
+        m_arrowFunctionContextLexicalEnvironmentRegister = m_lexicalEnvironmentRegister;
+        
+        ScopeOffset offset;
+        
+        ConcurrentJITLocker locker(ConcurrentJITLocker::NoLockingNecessary);
+        if (isThisUsedInInnerArrowFunction()) {
+            offset = functionSymbolTable->takeNextScopeOffset(locker);
+            functionSymbolTable->set(locker, propertyNames().thisIdentifier.impl(), SymbolTableEntry(VarOffset(offset)));
+        }
+
+        if (m_codeType == FunctionCode && isNewTargetUsedInInnerArrowFunction()) {
+            offset = functionSymbolTable->takeNextScopeOffset();
+            functionSymbolTable->set(locker, propertyNames().newTargetLocalPrivateName.impl(), SymbolTableEntry(VarOffset(offset)));
+        }
+        
+        if (isConstructor() && constructorKind() == ConstructorKind::Derived && isSuperUsedInInnerArrowFunction()) {
+            offset = functionSymbolTable->takeNextScopeOffset(locker);
+            functionSymbolTable->set(locker, propertyNames().derivedConstructorPrivateName.impl(), SymbolTableEntry(VarOffset(offset)));
+        }
+
+        return;
+    }
 
     VariableEnvironment environment;

trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h

@@ -859 +859 @@
         void initializeVarLexicalEnvironment(int symbolTableConstantIndex, SymbolTable* functionSymbolTable, bool hasCapturedVariables);
         void initializeDefaultParameterValuesAndSetupFunctionScopeStack(FunctionParameters&, bool isSimpleParameterList, FunctionNode*, SymbolTable*, int symbolTableConstantIndex, const std::function<bool (UniquedStringImpl*)>& captures, bool shouldCreateArgumentsVariableInParameterScope);
-        void initializeArrowFunctionContextScopeIfNeeded();
+        void initializeArrowFunctionContextScopeIfNeeded(SymbolTable* functionSymbolTable = nullptr, bool canReuseLexicalEnvironment = false);
 
     public: