/*
 * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.graal.api.code;

import java.util.*;

import com.oracle.graal.api.code.Register.*;

/**
 * Represents a CPU architecture, including information such as its endianness, CPU registers, word
 * width, etc.
 */
public abstract class Architecture {

    /**
     * The endianness of the architecture.
     */
    public static enum ByteOrder {
        LittleEndian, BigEndian
    }

    /**
     * The number of bits required in a bit map covering all the registers that may store
     * references. The bit position of a register in the map is the register's
     * {@linkplain Register#number number}.
     */
    private final int registerReferenceMapBitCount;

    /**
     * Represents the natural size of words (typically registers and pointers) of this architecture,
     * in bytes.
     */
    private final int wordSize;

    /**
     * The name of this architecture (e.g. "AMD64", "SPARCv9").
     */
    private final String name;

    /**
     * Array of all available registers on this architecture. The index of each register in this
     * array is equal to its {@linkplain Register#number number}.
     */
    private final Register[] registers;

    /**
     * The byte ordering can be either little or big endian.
     */
    private final ByteOrder byteOrder;

    /**
     * Mask of the barrier constants denoting the barriers that are not required to be explicitly
     * inserted under this architecture.
     */
    private final int implicitMemoryBarriers;

    /**
     * Offset in bytes from the beginning of a call instruction to the displacement.
     */
    private final int machineCodeCallDisplacementOffset;

    /**
     * The size of the return address pushed to the stack by a call instruction. A value of 0
     * denotes that call linkage uses registers instead (e.g. SPARC).
     */
    private final int returnAddressSize;

    private final EnumMap<RegisterFlag, Register[]> registersByTypeAndEncoding;

    /**
     * Gets the register for a given {@linkplain Register#encoding encoding} and type.
     * 
     * @param encoding a register value as used in a machine instruction
     * @param type the type of the register
     */
    public Register registerFor(int encoding, RegisterFlag type) {
        Register[] regs = registersByTypeAndEncoding.get(type);
        assert encoding >= 0 && encoding < regs.length;
        Register reg = regs[encoding];
        assert reg != null;
        return reg;
    }

    protected Architecture(String name, int wordSize, ByteOrder byteOrder, Register[] registers, int implicitMemoryBarriers, int nativeCallDisplacementOffset, int registerReferenceMapBitCount,
                    int returnAddressSize) {
        this.name = name;
        this.registers = registers;
        this.wordSize = wordSize;
        this.byteOrder = byteOrder;
        this.implicitMemoryBarriers = implicitMemoryBarriers;
        this.machineCodeCallDisplacementOffset = nativeCallDisplacementOffset;
        this.registerReferenceMapBitCount = registerReferenceMapBitCount;
        this.returnAddressSize = returnAddressSize;

        registersByTypeAndEncoding = new EnumMap<>(RegisterFlag.class);
        EnumMap<RegisterFlag, Register[]> categorizedRegs = Register.categorize(registers);
        for (RegisterFlag type : RegisterFlag.values()) {
            Register[] regs = categorizedRegs.get(type);
            int max = Register.maxRegisterEncoding(regs);
            Register[] regsByEnc = new Register[max + 1];
            for (Register reg : regs) {
                regsByEnc[reg.encoding] = reg;
            }
            registersByTypeAndEncoding.put(type, regsByEnc);
        }
    }

    /**
     * Converts this architecture to a string.
     * 
     * @return the string representation of this architecture
     */
    @Override
    public final String toString() {
        return getName().toLowerCase();
    }

    public int getRegisterReferenceMapBitCount() {
        return registerReferenceMapBitCount;
    }

    /**
     * Gets the natural size of words (typically registers and pointers) of this architecture, in
     * bytes.
     */
    public int getWordSize() {
        return wordSize;
    }

    /**
     * Gets the name of this architecture.
     */
    public String getName() {
        return name;
    }

    /**
     * Gets an array of all available registers on this architecture. The index of each register in
     * this array is equal to its {@linkplain Register#number number}.
     */
    public Register[] getRegisters() {
        return registers.clone();
    }

    public ByteOrder getByteOrder() {
        return byteOrder;
    }

    /**
     * Gets a mask of the barrier constants denoting the barriers that are not required to be
     * explicitly inserted under this architecture.
     */
    public int getImplicitMemoryBarriers() {
        return implicitMemoryBarriers;
    }

    /**
     * Gets the size of the return address pushed to the stack by a call instruction. A value of 0
     * denotes that call linkage uses registers instead.
     */
    public int getReturnAddressSize() {
        return returnAddressSize;
    }

    /**
     * Gets the offset in bytes from the beginning of a call instruction to the displacement.
     */
    public int getMachineCodeCallDisplacementOffset() {
        return machineCodeCallDisplacementOffset;
    }

    /**
     * Determines the barriers in a given barrier mask that are explicitly required on this
     * architecture.
     * 
     * @param barriers a mask of the barrier constants
     * @return the value of {@code barriers} minus the barriers unnecessary on this architecture
     */
    public final int requiredBarriers(int barriers) {
        return barriers & ~implicitMemoryBarriers;
    }
}