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 */ 23 package com.oracle.graal.asm; 24 25 import java.util.ArrayList; 26 27 /** 28 * This class represents a label within assembly code. 29 */ 30 public final class Label { 31 32 private int position = -1; 33 34 /** 35 * References to instructions that jump to this unresolved label. These instructions need to be 36 * patched when the label is bound using the {@link #patchInstructions(AbstractAssembler)} 37 * method. 38 */ 39 private ArrayList<Integer> patchPositions = new ArrayList<>(4); 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 /** 55 * Binds the label to the specified position. 56 * 57 * @param pos the position 58 */ 59 protected void bind(int pos) { 60 this.position = pos; 61 assert isBound(); 62 } 63 64 public boolean isBound() { 65 return position >= 0; 66 } 67 68 public void addPatchAt(int branchLocation) { 69 assert !isBound() : "Label is already bound"; 70 patchPositions.add(branchLocation); 71 } 72 73 protected void patchInstructions(AbstractAssembler masm) { 74 assert isBound() : "Label should be bound"; 75 int target = position; 76 for (int i = 0; i < patchPositions.size(); ++i) { 77 int pos = patchPositions.get(i); 78 masm.patchJumpTarget(pos, target); 79 } 80 } 81 82 @Override 83 public String toString() { 84 return isBound() ? String.valueOf(position()) : "?"; 85 } 86 }