/*

 * Copyright (c) 2010, 2016, 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 jdk.vm.ci.code;

import jdk.vm.ci.meta.AllocatableValue;

import jdk.vm.ci.meta.ValueKind;

/**

 * Represents a compiler spill slot or an outgoing stack-based argument in a method's frame or an

 * incoming stack-based argument in a method's {@linkplain #isInCallerFrame() caller's frame}.

 */

public final class StackSlot extends AllocatableValue {

    private final int offset;

    private final boolean addFrameSize;

    /**

     * Gets a {@link StackSlot} instance representing a stack slot at a given index holding a value

     * of a given kind.

     *

     * @param kind The kind of the value stored in the stack slot.

     * @param offset The offset of the stack slot (in bytes)

     * @param addFrameSize Specifies if the offset is relative to the stack pointer, or the

     *            beginning of the frame (stack pointer + total frame size).

     */

    public static StackSlot get(ValueKind<?> kind, int offset, boolean addFrameSize) {

        assert addFrameSize || offset >= 0;

        return new StackSlot(kind, offset, addFrameSize);

    }

    /**

     * Private constructor to enforce use of {@link #get(ValueKind, int, boolean)} so that a cache

     * can be used.

     */

    private StackSlot(ValueKind<?> kind, int offset, boolean addFrameSize) {

        super(kind);

        this.offset = offset;

        this.addFrameSize = addFrameSize;

    }

    /**

     * Gets the offset of this stack slot, relative to the stack pointer.

     *

     * @return The offset of this slot (in bytes).

     */

    public int getOffset(int totalFrameSize) {

        assert totalFrameSize > 0 || !addFrameSize;

        int result = offset + (addFrameSize ? totalFrameSize : 0);

        assert result >= 0;

        return result;

    }

    public boolean isInCallerFrame() {

        return addFrameSize && offset >= 0;

    }

    public int getRawOffset() {

        return offset;

    }

    public boolean getRawAddFrameSize() {

        return addFrameSize;

    }

    @Override

    public String toString() {

        if (!addFrameSize) {

            return "out:" + offset + getKindSuffix();

        } else if (offset >= 0) {

            return "in:" + offset + getKindSuffix();

        } else {

            return "stack:" + (-offset) + getKindSuffix();

        }

    }

    /**

     * Gets this stack slot used to pass an argument from the perspective of a caller.

     */

    public StackSlot asOutArg() {

        assert offset >= 0;

        if (addFrameSize) {

            return get(getValueKind(), offset, false);

        }

        return this;

    }

    /**

     * Gets this stack slot used to pass an argument from the perspective of a callee.

     */

    public StackSlot asInArg() {

        assert offset >= 0;

        if (!addFrameSize) {

            return get(getValueKind(), offset, true);

        }

        return this;

    }

    @Override

    public int hashCode() {

        final int prime = 37;

        int result = super.hashCode();

        result = prime * result + (addFrameSize ? 1231 : 1237);

        result = prime * result + offset;

        return result;

    }

    @Override

    public boolean equals(Object obj) {

        if (obj instanceof StackSlot) {

            StackSlot other = (StackSlot) obj;

            return super.equals(obj) && addFrameSize == other.addFrameSize && offset == other.offset;

        }

        return false;

    }

}