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 org.graalvm.compiler.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 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 }