1 /*
   2  * Copyright (c) 2010, 2013, 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 package jdk.nashorn.internal.ir;
  26 
  27 import java.util.ArrayDeque;
  28 import java.util.ArrayList;
  29 import java.util.Collections;
  30 import java.util.Deque;
  31 import java.util.List;
  32 import jdk.nashorn.internal.codegen.types.Type;
  33 
  34 /**
  35  * Lexical context that keeps track of optimistic assumptions (if any)
  36  * made during code generation. Used from Attr and FinalizeTypes
  37  */
  38 public class OptimisticLexicalContext extends LexicalContext {
  39 
  40     private final boolean isEnabled;
  41 
  42     class Assumption {
  43         Symbol symbol;
  44         Type   type;
  45 
  46         Assumption(final Symbol symbol, final Type type) {
  47             this.symbol = symbol;
  48             this.type   = type;
  49         }
  50         @Override
  51         public String toString() {
  52             return symbol.getName() + "=" + type;
  53         }
  54     }
  55 
  56     /** Optimistic assumptions that could be made per function */
  57     private final Deque<List<Assumption>> optimisticAssumptions = new ArrayDeque<>();
  58 
  59     /**
  60      * Constructor
  61      * @param isEnabled are optimistic types enabled?
  62      */
  63     public OptimisticLexicalContext(final boolean isEnabled) {
  64         super();
  65         this.isEnabled = isEnabled;
  66     }
  67 
  68     /**
  69      * Are optimistic types enabled
  70      * @return true if optimistic types
  71      */
  72     public boolean isEnabled() {
  73         return isEnabled;
  74     }
  75 
  76     /**
  77      * Log an optimistic assumption during codegen
  78      * TODO : different parameters and more info about the assumption for future profiling
  79      * needs
  80      * @param symbol symbol
  81      * @param type   type
  82      */
  83     public void logOptimisticAssumption(final Symbol symbol, final Type type) {
  84         if (isEnabled) {
  85             final List<Assumption> peek = optimisticAssumptions.peek();
  86             peek.add(new Assumption(symbol, type));
  87         }
  88     }
  89 
  90     /**
  91      * Get the list of optimistic assumptions made
  92      * @return optimistic assumptions
  93      */
  94     public List<Assumption> getOptimisticAssumptions() {
  95         return Collections.unmodifiableList(optimisticAssumptions.peek());
  96     }
  97 
  98     /**
  99      * Does this method have optimistic assumptions made during codegen?
 100      * @return true if optimistic assumptions were made
 101      */
 102     public boolean hasOptimisticAssumptions() {
 103         return !optimisticAssumptions.isEmpty() && !getOptimisticAssumptions().isEmpty();
 104     }
 105 
 106     @Override
 107     public <T extends LexicalContextNode> T push(final T node) {
 108         if (isEnabled) {
 109             if(node instanceof FunctionNode) {
 110                 optimisticAssumptions.push(new ArrayList<Assumption>());
 111             }
 112         }
 113 
 114         return super.push(node);
 115     }
 116 
 117     @Override
 118     public <T extends Node> T pop(final T node) {
 119         final T popped = super.pop(node);
 120         if (isEnabled) {
 121             if(node instanceof FunctionNode) {
 122                 optimisticAssumptions.pop();
 123             }
 124         }
 125         return popped;
 126     }
 127 
 128 }