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/*
* Copyright (C) 2012 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef JSSegmentedVariableObject_h
#define JSSegmentedVariableObject_h
#include "JSObject.h"
#include "JSSymbolTableObject.h"
#include "Register.h"
#include "SymbolTable.h"
#include <wtf/OwnArrayPtr.h>
#include <wtf/SegmentedVector.h>
#include <wtf/UnusedParam.h>
namespace JSC {
class LLIntOffsetsExtractor;
class Register;
// This is a mostly drop-in replacement for JSVariableObject, except that it preserves
// the invariant that after a variable is created, its address in memory will not change
// so long as the JSSegmentedVariableObject is alive. This allows optimizations based
// on getting the address of the variable and remembering it. As well, unlike a
// JSVariableObject, this will manage the memory for the registers itself and neither
// requires nor allows for the subclasses to manage that memory. Finally,
// JSSegmentedVariableObject has its own GC tracing functionality, since it knows the
// exact dimensions of the variables array at all times.
class JSSegmentedVariableObject : public JSSymbolTableObject {
friend class JIT;
friend class LLIntOffsetsExtractor;
public:
typedef JSSymbolTableObject Base;
WriteBarrier<Unknown>& registerAt(int index) { return m_registers[index]; }
// This is a slow method call, which searches the register bank to find the index
// given a pointer. It will CRASH() if it does not find the register. Only use this
// in debug code (like bytecode dumping).
JS_EXPORT_PRIVATE int findRegisterIndex(void*);
WriteBarrier<Unknown>* assertRegisterIsInThisObject(WriteBarrier<Unknown>* registerPointer)
{
#if !ASSERT_DISABLED
findRegisterIndex(registerPointer);
#endif
return registerPointer;
}
// Adds numberOfRegistersToAdd registers, initializes them to Undefined, and returns
// the index of the first one added.
JS_EXPORT_PRIVATE int addRegisters(int numberOfRegistersToAdd);
JS_EXPORT_PRIVATE static void visitChildren(JSCell*, SlotVisitor&);
protected:
static const unsigned StructureFlags = OverridesVisitChildren | JSSymbolTableObject::StructureFlags;
JSSegmentedVariableObject(JSGlobalData& globalData, Structure* structure, JSScope* scope)
: JSSymbolTableObject(globalData, structure, scope)
{
}
void finishCreation(JSGlobalData& globalData)
{
Base::finishCreation(globalData);
}
SegmentedVector<WriteBarrier<Unknown>, 16> m_registers;
};
} // namespace JSC
#endif // JSSegmentedVariableObject_h