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 24 25 package org.graalvm.compiler.asm; 26 27 import java.util.ArrayList; 28 29 /** 30 * This class represents a label within assembly code. 31 */ 32 public final class Label { 33 34 private int position = -1; 35 private int blockId = -1; 36 37 /** 38 * References to instructions that jump to this unresolved label. These instructions need to be 39 * patched when the label is bound using the {@link #patchInstructions(Assembler)} method. 40 */ 41 private ArrayList<Integer> patchPositions = null; 42 43 /** 44 * Returns the position of this label in the code buffer. 45 * 46 * @return the position 47 */ 48 public int position() { 49 assert position >= 0 : "Unbound label is being referenced"; 50 return position; 51 } 52 53 public Label() { 54 } 55 56 public Label(int id) { 57 blockId = id; 58 } 59 60 public int getBlockId() { 61 return blockId; 62 } 63 64 /** 65 * Binds the label to the specified position. 66 * 67 * @param pos the position 68 */ 69 protected void bind(int pos) { 70 this.position = pos; 71 assert isBound(); 72 } 73 74 public boolean isBound() { 75 return position >= 0; 76 } 77 78 public void addPatchAt(int branchLocation) { 79 assert !isBound() : "Label is already bound " + this + " " + branchLocation + " at position " + position; 80 if (patchPositions == null) { 81 patchPositions = new ArrayList<>(2); 82 } 83 patchPositions.add(branchLocation); 84 } 85 86 protected void patchInstructions(Assembler masm) { 87 assert isBound() : "Label should be bound"; 88 if (patchPositions != null) { 89 int target = position; 90 for (int i = 0; i < patchPositions.size(); ++i) { 91 int pos = patchPositions.get(i); 92 masm.patchJumpTarget(pos, target); 93 } 94 } 95 } 96 97 public void reset() { 98 if (this.patchPositions != null) { 99 this.patchPositions.clear(); 100 } 101 this.position = -1; 102 } 103 104 @Override 105 public String toString() { 106 return isBound() ? String.valueOf(position()) : "?"; 107 } 108 }