Source/JavaScriptCore/bytecode/UnlinkedInstructionStream.cpp

/*
 * 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.
 */

#include "config.h"
#include "UnlinkedInstructionStream.h"

#include "Opcode.h"

namespace JSC {

static void append8(unsigned char*& ptr, unsigned char value)
{
    *(ptr++) = value;
}

static void append32(unsigned char*& ptr, unsigned value)
{
    if (!(value & 0xffffffe0)) {
        *(ptr++) = value;
        return;
    }

    if ((value & 0xffffffe0) == 0xffffffe0) {
        *(ptr++) = (Negative5Bit << 5) | (value & 0x1f);
        return;
    }

    if ((value & 0xffffffe0) == 0x40000000) {
        *(ptr++) = (ConstantRegister5Bit << 5) | (value & 0x1f);
        return;
    }

    if (!(value & 0xffffe000)) {
        *(ptr++) = (Positive13Bit << 5) | ((value >> 8) & 0x1f);
        *(ptr++) = value & 0xff;
        return;
    }

    if ((value & 0xffffe000) == 0xffffe000) {
        *(ptr++) = (Negative13Bit << 5) | ((value >> 8) & 0x1f);
        *(ptr++) = value & 0xff;
        return;
    }

    if ((value & 0xffffe000) == 0x40000000) {
        *(ptr++) = (ConstantRegister13Bit << 5) | ((value >> 8) & 0x1f);
        *(ptr++) = value & 0xff;
        return;
    }

    *(ptr++) = Full32Bit << 5;
    *(ptr++) = value & 0xff;
    *(ptr++) = (value >> 8) & 0xff;
    *(ptr++) = (value >> 16) & 0xff;
    *(ptr++) = (value >> 24) & 0xff;
}

UnlinkedInstructionStream::UnlinkedInstructionStream(const Vector<UnlinkedInstruction, 0, UnsafeVectorOverflow>& instructions)
    : m_instructionCount(instructions.size())
{
    Vector<unsigned char> buffer;

    // Reserve enough space up front so we never have to reallocate when appending.
    buffer.resizeToFit(m_instructionCount * 5);
    unsigned char* ptr = buffer.data();

    const UnlinkedInstruction* instructionsData = instructions.data();
    for (unsigned i = 0; i < m_instructionCount;) {
        const UnlinkedInstruction* pc = &instructionsData[i];
        OpcodeID opcode = pc[0].u.opcode;
        append8(ptr, opcode);

        unsigned opLength = opcodeLength(opcode);

        for (unsigned j = 1; j < opLength; ++j)
            append32(ptr, pc[j].u.index);

        i += opLength;
    }

    buffer.shrink(ptr - buffer.data());
    m_data = RefCountedArray<unsigned char>(buffer);
}

size_t UnlinkedInstructionStream::sizeInBytes() const
{
    return m_data.size() * sizeof(unsigned char);
}

#ifndef NDEBUG
const RefCountedArray<UnlinkedInstruction>& UnlinkedInstructionStream::unpackForDebugging() const
{
    if (!m_unpackedInstructionsForDebugging.size()) {
        m_unpackedInstructionsForDebugging = RefCountedArray<UnlinkedInstruction>(m_instructionCount);

        Reader instructionReader(*this);
        for (unsigned i = 0; !instructionReader.atEnd(); ) {
            const UnlinkedInstruction* pc = instructionReader.next();
            unsigned opLength = opcodeLength(pc[0].u.opcode);
            for (unsigned j = 0; j < opLength; ++j)
                m_unpackedInstructionsForDebugging[i++] = pc[j];
        }
    }

    return m_unpackedInstructionsForDebugging;
}
#endif

}