1 /* 2 * Copyright (c) 2009, 2018, 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 import org.graalvm.compiler.debug.GraalError; 30 31 /** 32 * This class represents a label within assembly code. 33 */ 34 public final class Label { 35 36 private int position = -1; 37 private int blockId = -1; 38 39 /** 40 * Positions of instructions that jump to this unresolved label. These instructions are patched 41 * when the label is bound. 42 */ 43 ArrayList<Integer> patchPositions; 44 45 /** 46 * Link in list of labels with instructions to be patched. 47 */ 48 Label nextWithPatches; 49 50 /** 51 * Returns the position of this label in the code buffer. 52 * 53 * @return the position 54 */ 55 public int position() { 56 assert position >= 0 : "Unbound label is being referenced"; 57 return position; 58 } 59 60 public Label() { 61 } 62 63 public Label(int id) { 64 blockId = id; 65 } 66 67 public int getBlockId() { 68 return blockId; 69 } 70 71 /** 72 * Binds the label to {@code pos} and patches all instructions added by 73 * {@link #addPatchAt(int, Assembler)}. 74 */ 75 protected void bind(int pos, Assembler asm) { 76 if (pos < 0) { 77 throw new GraalError("Cannot bind label to negative position %d", pos); 78 } 79 this.position = pos; 80 if (patchPositions != null) { 81 for (int i = 0; i < patchPositions.size(); ++i) { 82 asm.patchJumpTarget(patchPositions.get(i), position); 83 } 84 patchPositions = null; 85 } 86 } 87 88 public boolean isBound() { 89 return position >= 0; 90 } 91 92 public void addPatchAt(int branchLocation, Assembler asm) { 93 assert !isBound() : "Label is already bound " + this + " " + branchLocation + " at position " + position; 94 if (patchPositions == null) { 95 patchPositions = new ArrayList<>(2); 96 nextWithPatches = asm.labelsWithPatches; 97 asm.labelsWithPatches = this; 98 } 99 patchPositions.add(branchLocation); 100 101 } 102 103 public void reset() { 104 if (this.patchPositions != null) { 105 this.patchPositions.clear(); 106 } 107 this.position = -1; 108 } 109 110 @Override 111 public String toString() { 112 return isBound() ? String.valueOf(position()) : "?"; 113 } 114 }