darling-JavaScriptCore/dfg/DFGInPlaceAbstractState.h

/*
 * Copyright (C) 2013-2018 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
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 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#pragma once

#if ENABLE(DFG_JIT)

#include "DFGAbstractInterpreterClobberState.h"
#include "DFGAbstractValue.h"
#include "DFGBranchDirection.h"
#include "DFGFlowMap.h"
#include "DFGGraph.h"
#include "DFGNode.h"

namespace JSC { namespace DFG {

class InPlaceAbstractState {
    WTF_MAKE_FAST_ALLOCATED;
public:
    InPlaceAbstractState(Graph&);
    
    ~InPlaceAbstractState();
    
    explicit operator bool() const { return true; }
    
    void createValueForNode(NodeFlowProjection) { }
    
    ALWAYS_INLINE AbstractValue& fastForward(AbstractValue& value)
    {
        value.fastForwardTo(m_effectEpoch);
        return value;
    }
    
    ALWAYS_INLINE void fastForwardAndFilterUnproven(AbstractValue& value, SpeculatedType type)
    {
        value.fastForwardToAndFilterUnproven(m_effectEpoch, type);
    }
    
    ALWAYS_INLINE AbstractValue& forNodeWithoutFastForward(NodeFlowProjection node)
    {
        return m_abstractValues.at(node);
    }
    
    ALWAYS_INLINE AbstractValue& forNodeWithoutFastForward(Edge edge)
    {
        return forNodeWithoutFastForward(edge.node());
    }
    
    ALWAYS_INLINE AbstractValue& forNode(NodeFlowProjection node)
    {
        return fastForward(m_abstractValues.at(node));
    }
    
    ALWAYS_INLINE AbstractValue& forNode(Edge edge)
    {
        return forNode(edge.node());
    }
    
    ALWAYS_INLINE void clearForNode(NodeFlowProjection node)
    {
        AbstractValue& value = m_abstractValues.at(node);
        value.clear();
        value.m_effectEpoch = m_effectEpoch;
    }
    
    ALWAYS_INLINE void clearForNode(Edge edge)
    {
        clearForNode(edge.node());
    }
    
    template<typename... Arguments>
    ALWAYS_INLINE void setForNode(NodeFlowProjection node, Arguments&&... arguments)
    {
        AbstractValue& value = m_abstractValues.at(node);
        value.set(m_graph, std::forward<Arguments>(arguments)...);
        value.m_effectEpoch = m_effectEpoch;
    }

    template<typename... Arguments>
    ALWAYS_INLINE void setForNode(Edge edge, Arguments&&... arguments)
    {
        setForNode(edge.node(), std::forward<Arguments>(arguments)...);
    }
    
    template<typename... Arguments>
    ALWAYS_INLINE void setTypeForNode(NodeFlowProjection node, Arguments&&... arguments)
    {
        AbstractValue& value = m_abstractValues.at(node);
        value.setType(m_graph, std::forward<Arguments>(arguments)...);
        value.m_effectEpoch = m_effectEpoch;
    }

    template<typename... Arguments>
    ALWAYS_INLINE void setTypeForNode(Edge edge, Arguments&&... arguments)
    {
        setTypeForNode(edge.node(), std::forward<Arguments>(arguments)...);
    }
    
    template<typename... Arguments>
    ALWAYS_INLINE void setNonCellTypeForNode(NodeFlowProjection node, Arguments&&... arguments)
    {
        AbstractValue& value = m_abstractValues.at(node);
        value.setNonCellType(std::forward<Arguments>(arguments)...);
        value.m_effectEpoch = m_effectEpoch;
    }

    template<typename... Arguments>
    ALWAYS_INLINE void setNonCellTypeForNode(Edge edge, Arguments&&... arguments)
    {
        setNonCellTypeForNode(edge.node(), std::forward<Arguments>(arguments)...);
    }
    
    ALWAYS_INLINE void makeBytecodeTopForNode(NodeFlowProjection node)
    {
        AbstractValue& value = m_abstractValues.at(node);
        value.makeBytecodeTop();
        value.m_effectEpoch = m_effectEpoch;
    }
    
    ALWAYS_INLINE void makeBytecodeTopForNode(Edge edge)
    {
        makeBytecodeTopForNode(edge.node());
    }
    
    ALWAYS_INLINE void makeHeapTopForNode(NodeFlowProjection node)
    {
        AbstractValue& value = m_abstractValues.at(node);
        value.makeHeapTop();
        value.m_effectEpoch = m_effectEpoch;
    }
    
    ALWAYS_INLINE void makeHeapTopForNode(Edge edge)
    {
        makeHeapTopForNode(edge.node());
    }
    
    Operands<AbstractValue>& variablesForDebugging();

    unsigned size() const { return m_variables.size(); }
    unsigned numberOfArguments() const { return m_variables.numberOfArguments(); }
    unsigned numberOfLocals() const { return m_variables.numberOfLocals(); }
    unsigned numberOfTmps() const { return m_variables.numberOfTmps(); }
    
    AbstractValue& atIndex(size_t index)
    {
        activateVariableIfNecessary(index);
        return fastForward(m_variables[index]);
    }

    AbstractValue& operand(Operand operand)
    {
        return atIndex(m_variables.operandIndex(operand));
    }
    
    AbstractValue& local(size_t index)
    {
        return atIndex(m_variables.localIndex(index));
    }
    
    AbstractValue& argument(size_t index)
    {
        return atIndex(m_variables.argumentIndex(index));
    }
    
    // Call this before beginning CFA to initialize the abstract values of
    // arguments, and to indicate which blocks should be listed for CFA
    // execution.
    void initialize();

    // Start abstractly executing the given basic block. Initializes the
    // notion of abstract state to what we believe it to be at the head
    // of the basic block, according to the basic block's data structures.
    // This method also sets cfaShouldRevisit to false.
    void beginBasicBlock(BasicBlock*);
    
    BasicBlock* block() const { return m_block; }
    
    // Finish abstractly executing a basic block. If MergeToTail or
    // MergeToSuccessors is passed, then this merges everything we have
    // learned about how the state changes during this block's execution into
    // the block's data structures.
    //
    // Returns true if the state of the block at the tail was changed,
    // and, if the state at the heads of successors was changed.
    // A true return means that you must revisit (at least) the successor
    // blocks. This also sets cfaShouldRevisit to true for basic blocks
    // that must be visited next.
    bool endBasicBlock();
    
    // Reset the AbstractState. This throws away any results, and at this point
    // you can safely call beginBasicBlock() on any basic block.
    void reset();
    
    AbstractInterpreterClobberState clobberState() const { return m_clobberState; }
    
    // Would have the last executed node clobbered things had we not found a way to fold it?
    bool didClobberOrFolded() const { return clobberState() != AbstractInterpreterClobberState::NotClobbered; }
    
    // Did the last executed node clobber the world?
    bool didClobber() const { return clobberState() == AbstractInterpreterClobberState::ClobberedStructures; }
    
    // Are structures currently clobbered?
    StructureClobberState structureClobberState() const { return m_structureClobberState; }
    
    // Is the execution state still valid? This will be false if execute() has
    // returned false previously.
    bool isValid() const { return m_isValid; }
    
    // Merge the abstract state stored at the first block's tail into the second
    // block's head. Returns true if the second block's state changed. If so,
    // that block must be abstractly interpreted again. This also sets
    // to->cfaShouldRevisit to true, if it returns true, or if to has not been
    // visited yet.
    bool merge(BasicBlock* from, BasicBlock* to);
    
    // Merge the abstract state stored at the block's tail into all of its
    // successors. Returns true if any of the successors' states changed. Note
    // that this is automatically called in endBasicBlock() if MergeMode is
    // MergeToSuccessors.
    bool mergeToSuccessors(BasicBlock*);
    
    void clobberStructures() { m_effectEpoch.clobber(); }
    
    void observeInvalidationPoint() { m_effectEpoch.observeInvalidationPoint(); }
    
    // Methods intended to be called from AbstractInterpreter.
    void setClobberState(AbstractInterpreterClobberState state) { m_clobberState = state; }
    void mergeClobberState(AbstractInterpreterClobberState state) { m_clobberState = mergeClobberStates(m_clobberState, state); }
    void setStructureClobberState(StructureClobberState value) { m_structureClobberState = value; }
    void setIsValid(bool isValid) { m_isValid = isValid; }
    void setBranchDirection(BranchDirection branchDirection) { m_branchDirection = branchDirection; }
    
    // This method is evil - it causes a huge maintenance headache and there is a gross amount of
    // code devoted to it. It would be much nicer to just always run the constant folder on each
    // block. But, the last time we did it, it was a 1% SunSpider regression:
    // https://bugs.webkit.org/show_bug.cgi?id=133947
    // So, we should probably keep this method.
    void setShouldTryConstantFolding(bool tryConstantFolding) { m_shouldTryConstantFolding = tryConstantFolding; }

    void setProofStatus(Edge& edge, ProofStatus status)
    {
        edge.setProofStatus(status);
    }

private:
    ALWAYS_INLINE void activateVariableIfNecessary(size_t variableIndex)
    {
        if (!m_activeVariables[variableIndex])
            activateVariable(variableIndex);
    }
    
    void activateVariable(size_t variableIndex);
    void activateAllVariables();
    
    static bool mergeVariableBetweenBlocks(AbstractValue& destination, AbstractValue& source, Node* destinationNode, Node* sourceNode);
    
    Graph& m_graph;

    FlowMap<AbstractValue>& m_abstractValues;
    Operands<AbstractValue> m_variables;
    FastBitVector m_activeVariables;
    BasicBlock* m_block;

    bool m_shouldTryConstantFolding;

    bool m_isValid;
    AbstractInterpreterClobberState m_clobberState;
    StructureClobberState m_structureClobberState;
    AbstractValueClobberEpoch m_epochAtHead;
    AbstractValueClobberEpoch m_effectEpoch;
    
    BranchDirection m_branchDirection; // This is only set for blocks that end in Branch and that execute to completion (i.e. m_isValid == true).
};

} } // namespace JSC::DFG

#endif // ENABLE(DFG_JIT)