1/*
2 * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23package org.graalvm.compiler.asm;
24
25import java.util.ArrayList;
26
27/**
28 * This class represents a label within assembly code.
29 */
30public final class Label {
31
32    private int position = -1;
33    private int blockId = -1;
34
35    /**
36     * References to instructions that jump to this unresolved label. These instructions need to be
37     * patched when the label is bound using the {@link #patchInstructions(Assembler)} method.
38     */
39    private ArrayList<Integer> patchPositions = null;
40
41    /**
42     * Returns the position of this label in the code buffer.
43     *
44     * @return the position
45     */
46    public int position() {
47        assert position >= 0 : "Unbound label is being referenced";
48        return position;
49    }
50
51    public Label() {
52    }
53
54    public Label(int id) {
55        blockId = id;
56    }
57
58    public int getBlockId() {
59        return blockId;
60    }
61
62    /**
63     * Binds the label to the specified position.
64     *
65     * @param pos the position
66     */
67    protected void bind(int pos) {
68        this.position = pos;
69        assert isBound();
70    }
71
72    public boolean isBound() {
73        return position >= 0;
74    }
75
76    public void addPatchAt(int branchLocation) {
77        assert !isBound() : "Label is already bound " + this + " " + branchLocation + " at position " + position;
78        if (patchPositions == null) {
79            patchPositions = new ArrayList<>(2);
80        }
81        patchPositions.add(branchLocation);
82    }
83
84    protected void patchInstructions(Assembler masm) {
85        assert isBound() : "Label should be bound";
86        if (patchPositions != null) {
87            int target = position;
88            for (int i = 0; i < patchPositions.size(); ++i) {
89                int pos = patchPositions.get(i);
90                masm.patchJumpTarget(pos, target);
91            }
92        }
93    }
94
95    public void reset() {
96        if (this.patchPositions != null) {
97            this.patchPositions.clear();
98        }
99        this.position = -1;
100    }
101
102    @Override
103    public String toString() {
104        return isBound() ? String.valueOf(position()) : "?";
105    }
106}
107