/*
 * Copyright (c) 2007, 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.sun.max.vm.runtime;

import static com.sun.max.vm.intrinsics.MaxineIntrinsicIDs.*;

import com.sun.max.annotate.*;
import com.sun.max.unsafe.*;
import com.sun.max.vm.intrinsics.*;
import com.sun.max.vm.thread.*;

/**
 * Direct access to certain CPU registers of the current thread, directed by ABI-managed register roles.
 */
public final class VMRegister {

    private VMRegister() {
    }

    /**
     * The register that is customarily used as "the stack pointer" on the target CPU.
     * Typically this register is not flexibly allocatable for other uses.
     * AMD64: RSP
     */
    public static final int CPU_SP = 0;

    /**
     * The register that is customarily used as "frame pointer" on the target CPU.
     * AMD64: RBP
     */
    public static final int CPU_FP = 1;

    /**
     * The register that the current target ABI actually uses as stack pointer,
     * i.e. for code sequences that call, push, pop etc.
     * Typically this is the same as {@link #CPU_SP}.
     */
    public static final int ABI_SP = 2;

    /**
     * The register that the current target ABI actually uses as frame pointer,
     * i.e. for code sequences that access local variables, spill slots, stack parameters, etc.
     * This may or may not be the same as {@link #CPU_FP}.
     * For the baseline compiler it is, but the optimizing compiler uses {@link #CPU_SP} instead.
     */
    public static final int ABI_FP = 3;

    /**
     * The register denoting the currently active {@link VmThreadLocal thread locals}.
     * AMD64: R14
     */
    public static final int LATCH = 7;

    /**
     * @see MaxineIntrinsicIDs#READREG
     */
    @INTRINSIC(READREG)
    public static native Pointer getRegister(@INTRINSIC.Constant int registerId);

    /**
     * @see MaxineIntrinsicIDs#WRITEREG
     */
    @INTRINSIC(WRITEREG)
    public static native void setRegister(@INTRINSIC.Constant int registerId, Word value);

    @INLINE
    public static Pointer getCpuStackPointer() {
        return getRegister(CPU_SP);
    }

    @INLINE
    public static Pointer getCpuFramePointer() {
        return getRegister(CPU_FP);
    }

    @INLINE
    public static Pointer getAbiStackPointer() {
        return getRegister(ABI_SP);
    }

    @INLINE
    public static Pointer getAbiFramePointer() {
        return getRegister(ABI_FP);
    }

    @INLINE
    public static Pointer getSafepointLatchRegister() {
        return getRegister(LATCH);
    }

    @INLINE
    public static void setSafepointLatchRegister(Word value) {
        setRegister(LATCH, value);
    }
}