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| 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 | + | |
| 26 | +package sun.tools.asm; | |
| 27 | + | |
| 28 | +import sun.tools.java.MemberDefinition; | |
| 29 | +import 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 | + */ | |
| 39 | +public final | |
| 40 | +class 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 | +} | |