1/* 2 * Copyright (c) 1994, 2004, 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26package sun.tools.asm; 27 28import sun.tools.java.MemberDefinition; 29import java.io.OutputStream; 30 31/** 32 * A label instruction. This is a 0 size instruction. 33 * It is the only valid target of a branch instruction. 34 * 35 * WARNING: The contents of this source file are not part of any 36 * supported API. Code that depends on them does so at its own risk: 37 * they are subject to change or removal without notice. 38 */ 39public final 40class Label extends Instruction { 41 static int labelCount = 0; 42 int ID; 43 int depth; 44 MemberDefinition locals[]; 45 46 /** 47 * Constructor 48 */ 49 public Label() { 50 super(0, opc_label, null); 51 this.ID = ++labelCount; 52 } 53 54 /** 55 * Get the final destination, eliminate jumps gotos, and jumps to 56 * labels that are immediately folowed by another label. The depth 57 * field is used to leave bread crumbs to avoid infinite loops. 58 */ 59 Label getDestination() { 60 Label lbl = this; 61 if ((next != null) && (next != this) && (depth == 0)) { 62 depth = 1; 63 64 switch (next.opc) { 65 case opc_label: 66 lbl = ((Label)next).getDestination(); 67 break; 68 69 case opc_goto: 70 lbl = ((Label)next.value).getDestination(); 71 break; 72 73 case opc_ldc: 74 case opc_ldc_w: 75 if (next.value instanceof Integer) { 76 Instruction inst = next.next; 77 if (inst.opc == opc_label) { 78 inst = ((Label)inst).getDestination().next; 79 } 80 81 if (inst.opc == opc_ifeq) { 82 if (((Integer)next.value).intValue() == 0) { 83 lbl = (Label)inst.value; 84 } else { 85 lbl = new Label(); 86 lbl.next = inst.next; 87 inst.next = lbl; 88 } 89 lbl = lbl.getDestination(); 90 break; 91 } 92 if (inst.opc == opc_ifne) { 93 if (((Integer)next.value).intValue() == 0) { 94 lbl = new Label(); 95 lbl.next = inst.next; 96 inst.next = lbl; 97 } else { 98 lbl = (Label)inst.value; 99 } 100 lbl = lbl.getDestination(); 101 break; 102 } 103 } 104 break; 105 } 106 depth = 0; 107 } 108 return lbl; 109 } 110 111 public String toString() { 112 String s = "$" + ID + ":"; 113 if (value != null) 114 s = s + " stack=" + value; 115 return s; 116 } 117} 118