mirror of
https://github.com/darlinghq/darling-JavaScriptCore.git
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107 lines
4.6 KiB
C++
107 lines
4.6 KiB
C++
/*
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* Copyright (C) 2012-2019 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of Apple Inc. ("Apple") nor the names of
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* its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "ConcurrentJSLock.h"
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#include "JSObject.h"
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#include "JSSymbolTableObject.h"
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#include "SymbolTable.h"
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#include <wtf/SegmentedVector.h>
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namespace JSC {
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class LLIntOffsetsExtractor;
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// This is a mostly drop-in replacement for JSLexicalEnvironment, except that it preserves
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// the invariant that after a variable is created, its address in memory will not change
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// so long as the JSSegmentedVariableObject is alive. This allows optimizations based
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// on getting the address of the variable and remembering it. As well, unlike a
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// JSLexicalEnvironment, this will manage the memory for the registers itself and neither
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// requires nor allows for the subclasses to manage that memory. Finally,
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// JSSegmentedVariableObject has its own GC tracing functionality, since it knows the
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// exact dimensions of the variables array at all times.
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class JSSegmentedVariableObject : public JSSymbolTableObject {
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friend class JIT;
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friend class LLIntOffsetsExtractor;
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public:
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using Base = JSSymbolTableObject;
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DECLARE_INFO;
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static constexpr bool needsDestruction = true;
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template<typename CellType, SubspaceAccess>
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static void subspaceFor(VM&) { RELEASE_ASSERT_NOT_REACHED(); }
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bool isValidScopeOffset(ScopeOffset offset)
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{
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return !!offset && offset.offset() < m_variables.size();
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}
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// This is not thread-safe, since m_variables is a segmented vector, and its spine can resize with
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// malloc/free if new variables - unrelated to the one you are accessing - are added. You can get
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// around this by grabbing m_lock, or finding some other way to get to the variable pointer (global
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// variable access bytecode instructions will have a direct pointer already).
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WriteBarrier<Unknown>& variableAt(ScopeOffset offset) { return m_variables[offset.offset()]; }
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// This is a slow method call, which searches the register bank to find the index
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// given a pointer. It will CRASH() if it does not find the register. Only use this
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// in debug code (like bytecode dumping).
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JS_EXPORT_PRIVATE ScopeOffset findVariableIndex(void*);
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WriteBarrier<Unknown>* assertVariableIsInThisObject(WriteBarrier<Unknown>* variablePointer)
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{
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if (ASSERT_ENABLED)
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findVariableIndex(variablePointer);
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return variablePointer;
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}
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// Adds numberOfRegistersToAdd registers, initializes them to Undefined, and returns
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// the index of the first one added.
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JS_EXPORT_PRIVATE ScopeOffset addVariables(unsigned numberOfVariablesToAdd, JSValue);
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JS_EXPORT_PRIVATE static void visitChildren(JSCell*, SlotVisitor&);
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JS_EXPORT_PRIVATE static void analyzeHeap(JSCell*, HeapAnalyzer&);
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protected:
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JSSegmentedVariableObject(VM&, Structure*, JSScope*);
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~JSSegmentedVariableObject();
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void finishCreation(VM&);
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private:
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SegmentedVector<WriteBarrier<Unknown>, 16> m_variables;
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#ifndef NDEBUG
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bool m_alreadyDestroyed { false }; // We use these assertions to check that we aren't doing ancient hacks that result in this being destroyed more than once.
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#endif
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};
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} // namespace JSC
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