Source/JavaScriptCore/dfg/DFGArgumentPosition.h

/*
 * Copyright (C) 2012, 2013, 2015 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 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#pragma once

#include "DFGDoubleFormatState.h"
#include "DFGVariableAccessData.h"
#include "DFGVariableAccessDataDump.h"
#include "SpeculatedType.h"

namespace JSC { namespace DFG {

class ArgumentPosition {
public:
    ArgumentPosition()
        : m_prediction(SpecNone)
        , m_doubleFormatState(EmptyDoubleFormatState)
        , m_isProfitableToUnbox(false)
        , m_shouldNeverUnbox(false)
    {
    }
    
    void addVariable(VariableAccessData* variable)
    {
        m_variables.append(variable);
        
        // We may set this early. Merging it here saves us time in prediction propagation.
        variable->mergeShouldNeverUnbox(m_shouldNeverUnbox);
    }
    
    VariableAccessData* someVariable() const
    {
        if (m_variables.isEmpty())
            return nullptr;
        return m_variables[0]->find();
    }
    
    FlushFormat flushFormat() const
    {
        if (VariableAccessData* variable = someVariable())
            return variable->flushFormat();
        return DeadFlush;
    }
    
    bool mergeShouldNeverUnbox(bool shouldNeverUnbox)
    {
        return checkAndSet(m_shouldNeverUnbox, m_shouldNeverUnbox || shouldNeverUnbox);
    }
    
    bool mergeArgumentPredictionAwareness()
    {
        bool changed = false;
        for (unsigned i = 0; i < m_variables.size(); ++i) {
            VariableAccessData* variable = m_variables[i]->find();
            changed |= mergeSpeculation(m_prediction, variable->argumentAwarePrediction());
            changed |= mergeDoubleFormatState(m_doubleFormatState, variable->doubleFormatState());
            changed |= mergeShouldNeverUnbox(variable->shouldNeverUnbox());
        }
        if (!changed)
            return false;
        changed = false;
        for (unsigned i = 0; i < m_variables.size(); ++i) {
            VariableAccessData* variable = m_variables[i]->find();
            changed |= variable->mergeArgumentAwarePrediction(m_prediction);
            changed |= variable->mergeDoubleFormatState(m_doubleFormatState);
            changed |= variable->mergeShouldNeverUnbox(m_shouldNeverUnbox);
        }
        return changed;
    }
    
    bool mergeArgumentUnboxingAwareness()
    {
        bool changed = false;
        for (unsigned i = 0; i < m_variables.size(); ++i) {
            VariableAccessData* variable = m_variables[i]->find();
            changed |= checkAndSet(m_isProfitableToUnbox, m_isProfitableToUnbox || variable->isProfitableToUnbox());
        }
        if (!changed)
            return false;
        changed = false;
        for (unsigned i = 0; i < m_variables.size(); ++i) {
            VariableAccessData* variable = m_variables[i]->find();
            changed |= variable->mergeIsProfitableToUnbox(m_isProfitableToUnbox);
        }
        return changed;
    }
    
    bool shouldUnboxIfPossible() const { return m_isProfitableToUnbox && !m_shouldNeverUnbox; }
    
    SpeculatedType prediction() const { return m_prediction; }
    DoubleFormatState doubleFormatState() const { return m_doubleFormatState; }
    bool shouldUseDoubleFormat() const
    {
        return doubleFormatState() == UsingDoubleFormat && shouldUnboxIfPossible();
    }
    
    void dump(PrintStream& out, Graph* graph)
    {
        for (unsigned i = 0; i < m_variables.size(); ++i) {
            VariableAccessData* variable = m_variables[i]->find();
            Operand operand = variable->operand();

            if (i)
                out.print(" ");

            out.print(operand, "(", VariableAccessDataDump(*graph, variable), ")");
        }
        out.print("\n");
    }
    
private:
    SpeculatedType m_prediction;
    DoubleFormatState m_doubleFormatState;
    bool m_isProfitableToUnbox;
    bool m_shouldNeverUnbox;
    
    Vector<VariableAccessData*, 2> m_variables;
};

} } // namespace JSC::DFG