| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| #pragma once |
| |
| #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(WeakValue) |
| { |
| } |
| |
| FrozenValue(JSValue value) |
| : m_value(value) |
| , m_structure(nullptr) |
| , m_strength(WeakValue) |
| { |
| 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(*value.asCell()->vm()) == structure->classInfo()); |
| ASSERT(!!structure || (strength == WeakValue)); |
| } |
| |
| static FrozenValue* emptySingleton(); |
| |
| bool operator!() const { return !m_value; } |
| |
| JSValue value() const { return m_value; } |
| JSCell* cell() const { return m_value.asCell(); } |
| |
| template<typename T> |
| T dynamicCast(VM& vm) |
| { |
| JSValue theValue = value(); |
| if (!theValue) |
| return nullptr; |
| return jsDynamicCast<T>(vm, theValue); |
| } |
| template<typename T> |
| T cast() |
| { |
| return jsCast<T>(value()); |
| } |
| |
| Structure* structure() const { return m_structure; } |
| |
| void strengthenTo(ValueStrength strength) |
| { |
| if (!!m_value && m_value.isCell()) |
| m_strength = merge(m_strength, strength); |
| } |
| |
| bool pointsToHeap() const { return !!value() && value().isCell(); } |
| |
| // The strength of the value itself. The structure is almost always weak. |
| ValueStrength strength() const { return m_strength; } |
| |
| String tryGetString(Graph&); |
| |
| 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, |
| WeakValue); |
| } |
| |
| JSValue m_value; |
| Structure* m_structure; |
| ValueStrength m_strength; |
| }; |
| |
| } } // namespace JSC::DFG |
| |
| #endif // ENABLE(DFG_JIT) |