Expression.java revision 953:221a84ef44c0
1183873Sraj/* 2183873Sraj * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. 3183873Sraj * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4183873Sraj * 5183873Sraj * This code is free software; you can redistribute it and/or modify it 6183873Sraj * under the terms of the GNU General Public License version 2 only, as 7183873Sraj * published by the Free Software Foundation. Oracle designates this 8183873Sraj * particular file as subject to the "Classpath" exception as provided 9183873Sraj * by Oracle in the LICENSE file that accompanied this code. 10191954Skuriyama * 11185478Ssam * This code is distributed in the hope that it will be useful, but WITHOUT 12183873Sraj * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13183873Sraj * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14183873Sraj * version 2 for more details (a copy is included in the LICENSE file that 15183873Sraj * accompanied this code). 16183873Sraj * 17183873Sraj * You should have received a copy of the GNU General Public License version 18183873Sraj * 2 along with this work; if not, write to the Free Software Foundation, 19183873Sraj * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20183873Sraj * 21191954Skuriyama * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22183873Sraj * or visit www.oracle.com if you need additional information or have any 23191954Skuriyama * questions. 24191954Skuriyama */ 25191954Skuriyama 26191954Skuriyamapackage jdk.nashorn.internal.ir; 27183873Sraj 28191954Skuriyamaimport java.util.function.Function; 29183873Srajimport jdk.nashorn.internal.codegen.types.Type; 30183873Srajimport jdk.nashorn.internal.runtime.UnwarrantedOptimismException; 31183873Sraj 32183873Sraj/** 33183873Sraj * Common superclass for all expression nodes. Expression nodes can have 34183873Sraj * an associated symbol as well as a type. 35191954Skuriyama * 36183873Sraj */ 37183873Srajpublic abstract class Expression extends Node { 38183873Sraj static final String OPT_IDENTIFIER = "%"; 39183873Sraj 40191954Skuriyama private static final Function<Symbol, Type> UNKNOWN_LOCALS = new Function<Symbol, Type>() { 41191954Skuriyama @Override 42191954Skuriyama public Type apply(final Symbol t) { 43183873Sraj return null; 44183873Sraj } 45191954Skuriyama }; 46183873Sraj 47183873Sraj Expression(final long token, final int start, final int finish) { 48191954Skuriyama super(token, start, finish); 49183873Sraj } 50185090Sraj 51185090Sraj Expression(final long token, final int finish) { 52183873Sraj super(token, finish); 53183873Sraj } 54183873Sraj 55183873Sraj Expression(final Expression expr) { 56183873Sraj super(expr); 57183873Sraj } 58183873Sraj 59183873Sraj /** 60183873Sraj * Returns the type of the expression. 61183873Sraj * 62183873Sraj * @return the type of the expression. 63183873Sraj */ 64183873Sraj public final Type getType() { 65183873Sraj return getType(UNKNOWN_LOCALS); 66183873Sraj } 67183873Sraj 68183873Sraj /** 69183873Sraj * Returns the type of the expression under the specified symbol-to-type mapping. By default delegates to 70183873Sraj * {@link #getType()} but expressions whose type depends on their subexpressions' types and expressions whose type 71183873Sraj * depends on symbol type ({@link IdentNode}) will have a special implementation. 72183873Sraj * @param localVariableTypes a mapping from symbols to their types, used for type calculation. 73183873Sraj * @return the type of the expression under the specified symbol-to-type mapping. 74183873Sraj */ 75183873Sraj public abstract Type getType(final Function<Symbol, Type> localVariableTypes); 76183873Sraj 77183873Sraj /** 78183873Sraj * Returns {@code true} if this expression depends exclusively on state that is constant 79 * or local to the currently running function and thus inaccessible to other functions. 80 * This implies that a local expression must not call any other functions (neither directly 81 * nor implicitly through a getter, setter, or object-to-primitive type conversion). 82 * 83 * @return true if this expression does not depend on state shared with other functions. 84 */ 85 public boolean isLocal() { 86 return false; 87 } 88 89 /** 90 * Is this a self modifying assignment? 91 * @return true if self modifying, e.g. a++, or a*= 17 92 */ 93 public boolean isSelfModifying() { 94 return false; 95 } 96 97 /** 98 * Returns widest operation type of this operation. 99 * 100 * @return the widest type for this operation 101 */ 102 public Type getWidestOperationType() { 103 return Type.OBJECT; 104 } 105 106 /** 107 * Returns true if the type of this expression is narrower than its widest operation type (thus, it is 108 * optimistically typed). 109 * @return true if this expression is optimistically typed. 110 */ 111 public final boolean isOptimistic() { 112 return getType().narrowerThan(getWidestOperationType()); 113 } 114 115 void optimisticTypeToString(final StringBuilder sb) { 116 optimisticTypeToString(sb, isOptimistic()); 117 } 118 119 void optimisticTypeToString(final StringBuilder sb, final boolean optimistic) { 120 sb.append('{'); 121 final Type type = getType(); 122 final String desc = type == Type.UNDEFINED ? "U" : type.getDescriptor(); 123 124 sb.append(desc.charAt(desc.length() - 1) == ';' ? "O" : desc); 125 if (isOptimistic() && optimistic) { 126 sb.append(OPT_IDENTIFIER); 127 final int pp = ((Optimistic)this).getProgramPoint(); 128 if (UnwarrantedOptimismException.isValid(pp)) { 129 sb.append('_').append(pp); 130 } 131 } 132 sb.append('}'); 133 } 134 135 /** 136 * Returns true if the runtime value of this expression is always false when converted to boolean as per ECMAScript 137 * ToBoolean conversion. Used in control flow calculations. 138 * @return true if this expression's runtime value converted to boolean is always false. 139 */ 140 public boolean isAlwaysFalse() { 141 return false; 142 } 143 144 /** 145 * Returns true if the runtime value of this expression is always true when converted to boolean as per ECMAScript 146 * ToBoolean conversion. Used in control flow calculations. 147 * @return true if this expression's runtime value converted to boolean is always true. 148 */ 149 public boolean isAlwaysTrue() { 150 return false; 151 } 152 153 /** 154 * Returns true if the expression is not null and {@link #isAlwaysFalse()}. 155 * @param test a test expression used as a predicate of a branch or a loop. 156 * @return true if the expression is not null and {@link #isAlwaysFalse()}. 157 */ 158 public static boolean isAlwaysFalse(final Expression test) { 159 return test != null && test.isAlwaysFalse(); 160 } 161 162 163 /** 164 * Returns true if the expression is null or {@link #isAlwaysTrue()}. Null is considered to be always true as a 165 * for loop with no test is equivalent to a for loop with always-true test. 166 * @param test a test expression used as a predicate of a branch or a loop. 167 * @return true if the expression is null or {@link #isAlwaysFalse()}. 168 */ 169 public static boolean isAlwaysTrue(final Expression test) { 170 return test == null || test.isAlwaysTrue(); 171 } 172} 173