/*
 * Copyright (C) 2015-2016 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 AirTmpWidth_h
#define AirTmpWidth_h

#if ENABLE(B3_JIT)

#include "AirArg.h"
#include <wtf/HashSet.h>

namespace JSC { namespace B3 { namespace Air {

class Code;

class TmpWidth {
public:
    TmpWidth();
    TmpWidth(Code&);
    ~TmpWidth();

    void recompute(Code&);

    // The width of a Tmp is the number of bits that you need to be able to track without some trivial
    // recovery. A Tmp may have a "subwidth" (say, Width32 on a 64-bit system) if either of the following
    // is true:
    //
    // - The high bits are never read.
    // - The high bits are always zero.
    //
    // This doesn't tell you which of those properties holds, but you can query that using the other
    // methods.
    Arg::Width width(Tmp tmp) const
    {
        auto iter = m_width.find(tmp);
        if (iter == m_width.end())
            return Arg::minimumWidth(Arg(tmp).type());
        return std::min(iter->value.use, iter->value.def);
    }

    // Return the minimum required width for all defs/uses of this Tmp.
    Arg::Width requiredWidth(Tmp tmp)
    {
        auto iter = m_width.find(tmp);
        if (iter == m_width.end())
            return Arg::minimumWidth(Arg(tmp).type());
        return std::max(iter->value.use, iter->value.def);
    }

    // This indirectly tells you how much of the tmp's high bits are guaranteed to be zero. The number of
    // high bits that are zero are:
    //
    //     TotalBits - defWidth(tmp)
    //
    // Where TotalBits are the total number of bits in the register, so 64 on a 64-bit system.
    Arg::Width defWidth(Tmp tmp) const
    {
        auto iter = m_width.find(tmp);
        if (iter == m_width.end())
            return Arg::minimumWidth(Arg(tmp).type());
        return iter->value.def;
    }

    // This tells you how much of Tmp is going to be read.
    Arg::Width useWidth(Tmp tmp) const
    {
        auto iter = m_width.find(tmp);
        if (iter == m_width.end())
            return Arg::minimumWidth(Arg(tmp).type());
        return iter->value.use;
    }
    
private:
    struct Widths {
        Widths() { }

        Widths(Arg::Type type)
        {
            use = Arg::minimumWidth(type);
            def = Arg::minimumWidth(type);
        }

        void dump(PrintStream& out) const;
        
        Arg::Width use;
        Arg::Width def;
    };
    
    HashMap<Tmp, Widths> m_width;
};

} } } // namespace JSC::B3::Air

#endif // ENABLE(B3_JIT)

#endif // AirTmpWidth_h