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/*
* Copyright (C) 2014 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 INC. OR
* 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 DFGFrozenValue_h
#define DFGFrozenValue_h
#if ENABLE(DFG_JIT)
#include "DFGValueStrength.h"
#include "JSCell.h"
#include "JSCJSValue.h"
#include "Structure.h"
namespace JSC { namespace DFG {
class Graph;
class FrozenValue {
public:
FrozenValue()
: m_structure(nullptr)
, m_strength(FragileValue)
{
}
FrozenValue(JSValue value)
: m_value(value)
, m_structure(nullptr)
, m_strength(FragileValue)
{
RELEASE_ASSERT(!value || !value.isCell());
}
FrozenValue(JSValue value, Structure* structure, ValueStrength strength)
: m_value(value)
, m_structure(structure)
, m_strength(strength)
{
ASSERT((!!value && value.isCell()) == !!structure);
ASSERT(!value || !value.isCell() || value.asCell()->classInfo() == structure->classInfo());
ASSERT(!!structure || (strength == FragileValue));
}
static FrozenValue* emptySingleton();
bool operator!() const { return !m_value; }
JSValue value() const { return m_value; }
Structure* structure() const { return m_structure; }
void strengthenTo(ValueStrength strength)
{
if (!!m_value && m_value.isCell())
m_strength = merge(m_strength, strength);
}
// The strength of the value itself. The structure should be viewed as fragile
// except if it is watched, in which case it's weak. Note that currently we
// watch all watchable structures indiscriminantly, and so we also mark them
// weakly. We could improve on this: any optimization that makes use of a
// structure could signal that it has done so, and we could avoid watching
// watchable structures that we had never marked in such a way.
ValueStrength strength() const { return m_strength; }
void dumpInContext(PrintStream& out, DumpContext* context) const;
void dump(PrintStream& out) const;
private:
friend class Graph;
// This is a utility method for DFG::Graph::freeze(). You should almost always call
// Graph::freeze() directly. Calling this instead of Graph::freeze() can result in
// the same constant being viewed as having different structures during the course
// of compilation, which can sometimes cause bad things to happen. For example, we
// may observe that one version of the constant has an unwatchable structure but
// then a later version may start to have a watchable structure due to a transition.
// The point of freezing is to ensure that we generally only see one version of
// constants, but that requires freezing through the Graph.
static FrozenValue freeze(JSValue value)
{
return FrozenValue(
value,
(!!value && value.isCell()) ? value.asCell()->structure() : nullptr,
FragileValue);
}
JSValue m_value;
Structure* m_structure;
ValueStrength m_strength;
};
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)
#endif // DFGFrozenValue_h
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