1 /*
   2  * Copyright (c) 2009, 2019, 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 such that {@code method.codeSize() == 0 || bci < method.getCodeSize()}. That
  47      *            is, if code size is 0 then allow any value, otherwise the bci must be less than
  48      *            the code size.
  49      */
  50     public BytecodePosition(BytecodePosition caller, ResolvedJavaMethod method, int bci) {
  51         assert method != null;
  52         this.caller = caller;
  53         this.method = method;
  54         this.bci = bci;
  55         int codeSize = method.getCodeSize();
  56         if (codeSize != 0 && bci >= codeSize) {
  57             throw new IllegalArgumentException(String.format("bci %d is out of range for %s %d bytes", bci, method.format("%H.%n(%p)"), codeSize));
  58         }
  59     }
  60 
  61     /**
  62      * Converts this code position to a string representation.
  63      *
  64      * @return a string representation of this code position
  65      */
  66     @Override
  67     public String toString() {
  68         return CodeUtil.append(new StringBuilder(100), this).toString();
  69     }
  70 
  71     /**
  72      * Deep equality test.
  73      */
  74     @Override
  75     public boolean equals(Object obj) {
  76         if (obj == this) {
  77             return true;
  78         }
  79         if (obj != null && getClass() == obj.getClass()) {
  80             BytecodePosition that = (BytecodePosition) obj;
  81             if (this.bci == that.bci && Objects.equals(this.getMethod(), that.getMethod()) && Objects.equals(this.caller, that.caller)) {
  82                 return true;
  83             }
  84         }
  85         return false;
  86     }
  87 
  88     @Override
  89     public int hashCode() {
  90         int hc = method.hashCode() * 31 + bci;
  91         if (caller != null) {
  92             hc = (hc * 31) + caller.hashCode();
  93         }
  94         return hc;
  95     }
  96 
  97     /**
  98      * @return The location within the method, as a bytecode index. The constant {@code -1} may be
  99      *         used to indicate the location is unknown, for example within code synthesized by the
 100      *         compiler.
 101      */
 102     public int getBCI() {
 103         return bci;
 104     }
 105 
 106     /**
 107      * @return The runtime interface method for this position.
 108      */
 109     public ResolvedJavaMethod getMethod() {
 110         return method;
 111     }
 112 
 113     /**
 114      * The position where this position has been called, {@code null} if none.
 115      */
 116     public BytecodePosition getCaller() {
 117         return caller;
 118     }
 119 
 120     /**
 121      * Adds a caller to the current position returning the new position.
 122      */
 123     public BytecodePosition addCaller(BytecodePosition link) {
 124         if (getCaller() == null) {
 125             return new BytecodePosition(link, getMethod(), getBCI());
 126         } else {
 127             return new BytecodePosition(getCaller().addCaller(link), getMethod(), getBCI());
 128         }
 129     }
 130 }