001/*
002 * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package com.oracle.graal.asm;
024
025import java.util.*;
026
027/**
028 * This class represents a label within assembly code.
029 */
030public final class Label {
031
032    private int position = -1;
033    private int blockId = -1;
034
035    /**
036     * References to instructions that jump to this unresolved label. These instructions need to be
037     * patched when the label is bound using the {@link #patchInstructions(Assembler)} method.
038     */
039    private ArrayList<Integer> patchPositions = null;
040
041    /**
042     * Returns the position of this label in the code buffer.
043     *
044     * @return the position
045     */
046    public int position() {
047        assert position >= 0 : "Unbound label is being referenced";
048        return position;
049    }
050
051    public Label() {
052    }
053
054    public Label(int id) {
055        blockId = id;
056    }
057
058    public int getBlockId() {
059        return blockId;
060    }
061
062    /**
063     * Binds the label to the specified position.
064     *
065     * @param pos the position
066     */
067    protected void bind(int pos) {
068        this.position = pos;
069        assert isBound();
070    }
071
072    public boolean isBound() {
073        return position >= 0;
074    }
075
076    public void addPatchAt(int branchLocation) {
077        assert !isBound() : "Label is already bound " + this + " " + branchLocation + " at position " + position;
078        if (patchPositions == null) {
079            patchPositions = new ArrayList<>(2);
080        }
081        patchPositions.add(branchLocation);
082    }
083
084    protected void patchInstructions(Assembler masm) {
085        assert isBound() : "Label should be bound";
086        if (patchPositions != null) {
087            int target = position;
088            for (int i = 0; i < patchPositions.size(); ++i) {
089                int pos = patchPositions.get(i);
090                masm.patchJumpTarget(pos, target);
091            }
092        }
093    }
094
095    public void reset() {
096        if (this.patchPositions != null) {
097            this.patchPositions.clear();
098        }
099        this.position = -1;
100    }
101
102    @Override
103    public String toString() {
104        return isBound() ? String.valueOf(position()) : "?";
105    }
106}