/*

 * Copyright (c) 2009, 2019, 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 org.graalvm.compiler.asm;

import java.util.ArrayList;

import org.graalvm.compiler.debug.GraalError;

/**

 * This class represents a label within assembly code.

 */

public final class Label {

    private int position = -1;

    private int blockId = -1;

    /**

     * Positions of instructions that jump to this unresolved label. These instructions are patched

     * when the label is bound.

     */

    ArrayList<Integer> patchPositions;

    /**

     * Link in list of labels with instructions to be patched.

     */

    Label nextWithPatches;

    /**

     * Returns the position of this label in the code buffer.

     *

     * @return the position

     */

    public int position() {

        assert position >= 0 : "Unbound label is being referenced";

        return position;

    }

    public Label() {

    }

    public Label(int id) {

        blockId = id;

    }

    public int getBlockId() {

        return blockId;

    }

    /**

     * Binds the label to {@code pos} and patches all instructions added by

     * {@link #addPatchAt(int, Assembler)}.

     */

    protected void bind(int pos, Assembler asm) {

        if (pos < 0) {

            throw new GraalError("Cannot bind label to negative position %d", pos);

        }

        this.position = pos;

        if (patchPositions != null) {

            for (int i = 0; i < patchPositions.size(); ++i) {

                asm.patchJumpTarget(patchPositions.get(i), position);

            }

            patchPositions = null;

        }

    }

    public boolean isBound() {

        return position >= 0;

    }

    public void addPatchAt(int branchLocation, Assembler asm) {

        assert !isBound() : "Label is already bound " + this + " " + branchLocation + " at position " + position;

        if (patchPositions == null) {

            patchPositions = new ArrayList<>(2);

            nextWithPatches = asm.labelsWithPatches;

            asm.labelsWithPatches = this;

        }

        patchPositions.add(branchLocation);

    }

    public void reset() {

        if (this.patchPositions != null) {

            this.patchPositions.clear();

        }

        this.position = -1;

    }

    @Override

    public String toString() {

        return isBound() ? String.valueOf(position()) : "?";

    }

}