Changeset 231889 in webkit for trunk/Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp

Timestamp:

May 16, 2018, 10:21:41 PM (7 years ago)

Author:

[email protected]

Message:

UnlinkedFunctionExecutable doesn't need a parent source override field since it's only used for default class constructors
​https://bugs.webkit.org/show_bug.cgi?id=185637

Reviewed by Keith Miller.

We had this general mechanism for overriding an UnlinkedFunctionExecutable's parent
source code. However, we were only using this for default class constructors. There
are only two types of default class constructors. This patch makes it so that
we just store this information inside of a single bit, and ask for the source
code as needed instead of holding it in a nullable field that is 24 bytes in size.

This brings UnlinkedFunctionExecutable's size down from 184 bytes to 160 bytes.
This has the consequence of making it allocated out of a 160 byte size class
instead of a 224 byte size class. This should bring down its memory footprint
by ~40%.

• builtins/BuiltinExecutables.cpp:

(JSC::BuiltinExecutables::defaultConstructorSourceCode):
(JSC::BuiltinExecutables::createDefaultConstructor):
(JSC::BuiltinExecutables::createExecutable):

• builtins/BuiltinExecutables.h:
• bytecode/UnlinkedFunctionExecutable.cpp:

(JSC::UnlinkedFunctionExecutable::UnlinkedFunctionExecutable):
(JSC::UnlinkedFunctionExecutable::link):

• bytecode/UnlinkedFunctionExecutable.h:
• runtime/CodeCache.cpp:

(JSC::CodeCache::getUnlinkedGlobalFunctionExecutable):

File:

• trunk/Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp (modified) (8 diffs)

trunk/Source/JavaScriptCore/bytecode/UnlinkedFunctionExecutable.cpp

@@ -1 +1 @@
 /*
- * Copyright (C) 2012-2013, 2015-2016 Apple Inc. All Rights Reserved.
+ * Copyright (C) 2012-2018 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -27 +27 @@
 #include "UnlinkedFunctionExecutable.h"
 
+#include "BuiltinExecutables.h"
 #include "BytecodeGenerator.h"
 #include "ClassInfo.h"
@@ -41 +42 @@
 namespace JSC {
 
-static_assert(sizeof(UnlinkedFunctionExecutable) <= 256, "UnlinkedFunctionExecutable should fit in a 256-byte cell.");
+static_assert(sizeof(UnlinkedFunctionExecutable) <= 160, "UnlinkedFunctionExecutable should fit in a 160-byte cell. If you increase the size of this class, consider making a size class that perfectly fits it.");
 
 const ClassInfo UnlinkedFunctionExecutable::s_info = { "UnlinkedFunctionExecutable", nullptr, nullptr, nullptr, CREATE_METHOD_TABLE(UnlinkedFunctionExecutable) };
@@ -77 +78 @@
 }
 
-UnlinkedFunctionExecutable::UnlinkedFunctionExecutable(VM* vm, Structure* structure, const SourceCode& parentSource, SourceCode&& parentSourceOverride, FunctionMetadataNode* node, UnlinkedFunctionKind kind, ConstructAbility constructAbility, JSParserScriptMode scriptMode, VariableEnvironment& parentScopeTDZVariables, DerivedContextType derivedContextType)
+UnlinkedFunctionExecutable::UnlinkedFunctionExecutable(VM* vm, Structure* structure, const SourceCode& parentSource, FunctionMetadataNode* node, UnlinkedFunctionKind kind, ConstructAbility constructAbility, JSParserScriptMode scriptMode, VariableEnvironment& parentScopeTDZVariables, DerivedContextType derivedContextType, bool isBuiltinDefaultClassConstructor)
     : Base(*vm, structure)
     , m_firstLineOffset(node->firstLine() - parentSource.firstLine().oneBasedInt())
@@ -95 +96 @@
     , m_hasCapturedVariables(false)
     , m_isBuiltinFunction(kind == UnlinkedBuiltinFunction)
+    , m_isBuiltinDefaultClassConstructor(isBuiltinDefaultClassConstructor)
     , m_constructAbility(static_cast<unsigned>(constructAbility))
     , m_constructorKind(static_cast<unsigned>(node->constructorKind()))
@@ -104 +106 @@
     , m_ecmaName(node->ecmaName())
     , m_inferredName(node->inferredName())
-    , m_parentSourceOverride(WTFMove(parentSourceOverride))
     , m_classSource(node->classSource())
     , m_parentScopeTDZVariables(vm->m_compactVariableMap->get(parentScopeTDZVariables))
@@ -115 +116 @@
     ASSERT(m_superBinding == static_cast<unsigned>(node->superBinding()));
     ASSERT(m_derivedContextType == static_cast<unsigned>(derivedContextType));
+    ASSERT(!(m_isBuiltinDefaultClassConstructor && constructorKind() == ConstructorKind::None));
 }
 
@@ -133 +135 @@
 FunctionExecutable* UnlinkedFunctionExecutable::link(VM& vm, const SourceCode& passedParentSource, std::optional<int> overrideLineNumber, Intrinsic intrinsic)
 {
-    const SourceCode& parentSource = m_parentSourceOverride.isNull() ? passedParentSource : m_parentSourceOverride;
+    const SourceCode& parentSource = !m_isBuiltinDefaultClassConstructor ? passedParentSource : BuiltinExecutables::defaultConstructorSourceCode(constructorKind());
     unsigned firstLine = parentSource.firstLine().oneBasedInt() + m_firstLineOffset;
     unsigned startOffset = parentSource.startOffset() + m_startOffset;