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 jdk.nashorn.internal.codegen.types.Type;
  28 
  29 /**
  30  * Is this a node that can be optimistically typed? This means that it
  31  * has a probable type but it's not available through static analysis
  32  *
  33  * The follow nodes are optimistic, with reasons therefore given within
  34  * parenthesis
  35  *
  36  * @see IndexNode  (dynamicGetIndex)
  37  * @see BinaryNode (local calculations to strongly typed bytecode)
  38  * @see UnaryNode  (local calculations to strongly typed bytecode)
  39  * @see CallNode   (dynamicCall)
  40  * @see AccessNode (dynamicGet)
  41  * @see IdentNode  (dynamicGet)
  42  */
  43 public interface Optimistic {
  44     /**
  45      * Unique node ID that is associated with an invokedynamic call that mail
  46      * fail and its callsite. This is so that nodes can be regenerated less
  47      * pessimistically the next generation if an assumption failed
  48      *
  49      * @return unique node id
  50      */
  51     public int getProgramPoint();
  52 
  53     /**
  54      * Set the node number for this node, associating with a unique per-function
  55      * program point
  56      * @param programPoint the node number
  57      * @return new node, or same if unchanged
  58      */
  59     public Optimistic setProgramPoint(final int programPoint);
  60 
  61     /**
  62      * Is it possible for this particular implementor to actually have any optimism?
  63      * SHIFT operators for instance are binary nodes, but never optimistic. Multiply
  64      * operators are. We might want to refurbish the type hierarchy to fix this.
  65      * @return true if theoretically optimistic
  66      */
  67     public boolean canBeOptimistic();
  68 
  69     /**
  70      * Get the most optimistic type for this node. Typically we start out as
  71      * an int, and then at runtime we bump this up to number and then Object
  72      *
  73      * @return optimistic type to be used in code generation
  74      */
  75     public Type getMostOptimisticType();
  76 
  77     /**
  78      * Most pessimistic type that is guaranteed to be safe.  Typically this is
  79      * number for arithmetic operations that can overflow, or Object for an add
  80      *
  81      * @return pessimistic type guaranteed to never overflow
  82      */
  83     public Type getMostPessimisticType();
  84 
  85     /**
  86      * Set the override type
  87      *
  88      * @param type the type
  89      * @return a node equivalent to this one except for the requested change.
  90      */
  91     public Optimistic setType(final Type type);
  92 }