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      */
BytecodePosition(BytecodePosition caller, ResolvedJavaMethod method, int bci)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
toString()61     public String toString() {
62         return CodeUtil.append(new StringBuilder(100), this).toString();
63     }
64 
65     /**
66      * Deep equality test.
67      */
68     @Override
equals(Object obj)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
hashCode()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      */
getBCI()92     public int getBCI() {
93         return bci;
94     }
95 
96     /**
97      * @return The runtime interface method for this position.
98      */
getMethod()99     public ResolvedJavaMethod getMethod() {
100         return method;
101     }
102 
103     /**
104      * The position where this position has been called, {@code null} if none.
105      */
getCaller()106     public BytecodePosition getCaller() {
107         return caller;
108     }
109 
110     /**
111      * Adds a caller to the current position returning the new position.
112      */
addCaller(BytecodePosition link)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 }
121