Changeset 153763 in webkit for trunk/Source/JavaScriptCore/bytecompiler

Timestamp:

Aug 6, 2013, 2:20:10 PM (12 years ago)

Author:

[email protected]

Message:

Delay Arguments creation in strict mode
​https://bugs.webkit.org/show_bug.cgi?id=119505

Reviewed by Geoffrey Garen.

Source/JavaScriptCore:

Make use of the write tracking performed by the parser to
allow us to know if we're modifying the parameters to a function.
Then use that information to make strict mode function opt out
of eager arguments creation.

• bytecompiler/BytecodeGenerator.cpp:

(JSC::BytecodeGenerator::BytecodeGenerator):
(JSC::BytecodeGenerator::createArgumentsIfNecessary):
(JSC::BytecodeGenerator::emitReturn):

• bytecompiler/BytecodeGenerator.h:

(JSC::BytecodeGenerator::shouldTearOffArgumentsEagerly):

• parser/Nodes.h:

(JSC::ScopeNode::modifiesParameter):

• parser/Parser.cpp:

(JSC::::parseInner):

• parser/Parser.h:

(JSC::Scope::declareParameter):
(JSC::Scope::getCapturedVariables):
(JSC::Parser::declareWrite):

• parser/ParserModes.h:

LayoutTests:

Add performance testcase for lazy creation of arguments in strict mode

• fast/js/regress/delay-tear-off-arguments-strictmode-expected.txt: Added.
• fast/js/regress/delay-tear-off-arguments-strictmode.html: Added.
• fast/js/regress/script-tests/delay-tear-off-arguments-strictmode.js: Added.

(bar):

Location:

trunk/Source/JavaScriptCore/bytecompiler

Files:

• BytecodeGenerator.cpp (modified) (4 diffs)
• BytecodeGenerator.h (modified) (1 diff)

trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp

@@ -239 +239 @@
         emitInitLazyRegister(unmodifiedArgumentsRegister);
         
-        if (m_codeBlock->isStrictMode()) {
+        if (shouldTearOffArgumentsEagerly()) {
             emitOpcode(op_create_arguments);
             instructions().append(argumentsRegister->index());
@@ -269 +269 @@
     }
 
-    if (capturesAnyArgumentByName && !codeBlock->isStrictMode()) {
+    if (capturesAnyArgumentByName && !shouldTearOffArgumentsEagerly()) {
         size_t parameterCount = m_symbolTable->parameterCount();
         OwnArrayPtr<SlowArgument> slowArguments = adoptArrayPtr(new SlowArgument[parameterCount]);
@@ -1560 +1560 @@
         return;
 
-    // If we're in strict mode we tear off the arguments on function
-    // entry, so there's no need to check if we need to create them
-    // now
-    if (m_codeBlock->isStrictMode())
+    if (shouldTearOffArgumentsEagerly())
         return;
 
@@ -1750 +1747 @@
     }
 
-    if (m_codeBlock->usesArguments() && m_codeBlock->numParameters() != 1 && !m_codeBlock->isStrictMode()) {
+    if (m_codeBlock->usesArguments() && m_codeBlock->numParameters() != 1 && !isStrictMode()) {
         emitOpcode(op_tear_off_arguments);
         instructions().append(m_codeBlock->argumentsRegister());

trunk/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h

@@ -555 +555 @@
         }
 
+        bool shouldTearOffArgumentsEagerly()
+        {
+            return m_codeType == FunctionCode && isStrictMode() && m_scopeNode->modifiesParameter();
+        }
+
         RegisterID* emitThrowExpressionTooDeepException();