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 jdk.vm.ci.code;
  24 
  25 import java.util.Objects;
  26 
  27 import jdk.vm.ci.meta.ResolvedJavaMethod;
  28 
  29 /**
  30  * Represents a code position, that is, a chain of inlined methods with bytecode locations, that is
  31  * communicated from the compiler to the runtime system. A code position can be used by the runtime
  32  * system to reconstruct a source-level stack trace for exceptions and to create
  33  * {@linkplain BytecodeFrame frames} for deoptimization.
  34  */
  35 public class BytecodePosition {
  36 
  37     private final BytecodePosition caller;
  38     private final ResolvedJavaMethod method;
  39     private final int bci;
  40 
  41     /**
  42      * Constructs a new object representing a given parent/caller, a given method, and a given BCI.
  43      *
  44      * @param caller the parent position
  45      * @param method the method
  46      * @param bci a BCI within the method
  47      */
  48     public BytecodePosition(BytecodePosition caller, ResolvedJavaMethod method, int bci) {
  49         assert method != null;
  50         this.caller = caller;
  51         this.method = method;
  52         this.bci = bci;
  53     }
  54 
  55     /**
  56      * Converts this code position to a string representation.
  57      *
  58      * @return a string representation of this code position
  59      */
  60     @Override
  61     public String toString() {
  62         return CodeUtil.append(new StringBuilder(100), this).toString();
  63     }
  64 
  65     /**
  66      * Deep equality test.
  67      */
  68     @Override
  69     public boolean equals(Object obj) {
  70         if (obj == this) {
  71             return true;
  72         }
  73         if (obj != null && getClass() == obj.getClass()) {
  74             BytecodePosition that = (BytecodePosition) obj;
  75             if (this.bci == that.bci && Objects.equals(this.getMethod(), that.getMethod()) && Objects.equals(this.caller, that.caller)) {
  76                 return true;
  77             }
  78         }
  79         return false;
  80     }
  81 
  82     @Override
  83     public int hashCode() {
  84         return getBCI();
  85     }
  86 
  87     /**
  88      * @return The location within the method, as a bytecode index. The constant {@code -1} may be
  89      *         used to indicate the location is unknown, for example within code synthesized by the
  90      *         compiler.
  91      */
  92     public int getBCI() {
  93         return bci;
  94     }
  95 
  96     /**
  97      * @return The runtime interface method for this position.
  98      */
  99     public ResolvedJavaMethod getMethod() {
 100         return method;
 101     }
 102 
 103     /**
 104      * The position where this position has been called, {@code null} if none.
 105      */
 106     public BytecodePosition getCaller() {
 107         return caller;
 108     }
 109 
 110     /**
 111      * Adds a caller to the current position returning the new position.
 112      */
 113     public BytecodePosition addCaller(BytecodePosition link) {
 114         if (getCaller() == null) {
 115             return new BytecodePosition(link, getMethod(), getBCI());
 116         } else {
 117             return new BytecodePosition(getCaller().addCaller(link), getMethod(), getBCI());
 118         }
 119     }
 120 }