1 /*
2 * Copyright (c) 2010, 2014, 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
26 package jdk.nashorn.internal.codegen;
27
28 import static jdk.nashorn.internal.runtime.Property.NOT_CONFIGURABLE;
29 import static jdk.nashorn.internal.runtime.Property.NOT_ENUMERABLE;
30 import static jdk.nashorn.internal.runtime.Property.NOT_WRITABLE;
31
32 import java.lang.invoke.MethodType;
33 import jdk.nashorn.internal.codegen.types.Type;
34 import jdk.nashorn.internal.ir.AccessNode;
35 import jdk.nashorn.internal.ir.CallNode;
36 import jdk.nashorn.internal.ir.Expression;
37 import jdk.nashorn.internal.ir.FunctionNode;
38 import jdk.nashorn.internal.ir.IdentNode;
39 import jdk.nashorn.internal.ir.IndexNode;
40 import jdk.nashorn.internal.ir.Optimistic;
41 import jdk.nashorn.internal.objects.ArrayBufferView;
42 import jdk.nashorn.internal.objects.NativeArray;
43 import jdk.nashorn.internal.runtime.FindProperty;
44 import jdk.nashorn.internal.runtime.JSType;
45 import jdk.nashorn.internal.runtime.Property;
46 import jdk.nashorn.internal.runtime.RecompilableScriptFunctionData;
47 import jdk.nashorn.internal.runtime.ScriptFunction;
48 import jdk.nashorn.internal.runtime.ScriptObject;
49 import jdk.nashorn.internal.runtime.ScriptRuntime;
50
51 /**
52 * Functionality for using a runtime scope to look up value types.
53 * Used during recompilation.
54 */
55 final class TypeEvaluator {
56 /**
57 * Type signature for invocation of functions without parameters: we must pass (callee, this) of type
58 * (ScriptFunction, Object) respectively. We also use Object as the return type (we must pass something,
59 * but it'll be ignored; it can't be void, though).
60 */
61 private static final MethodType EMPTY_INVOCATION_TYPE = MethodType.methodType(Object.class, ScriptFunction.class, Object.class);
62
63 private final Compiler compiler;
64 private final ScriptObject runtimeScope;
65
66 TypeEvaluator(final Compiler compiler, final ScriptObject runtimeScope) {
67 this.compiler = compiler;
68 this.runtimeScope = runtimeScope;
69 }
70
71 /**
72 * Returns true if the expression can be safely evaluated, and its value is an object known to always use
73 * String as the type of its property names retrieved through
74 * {@link ScriptRuntime#toPropertyIterator(Object)}. It is used to avoid optimistic assumptions about its
75 * property name types.
76 * @param expr the expression to test
77 * @return true if the expression can be safely evaluated, and its value is an object known to always use
78 * String as the type of its property iterators.
79 */
80 boolean hasStringPropertyIterator(final Expression expr) {
81 return evaluateSafely(expr) instanceof ScriptObject;
82 }
83
84 Type getOptimisticType(final Optimistic node) {
85 assert compiler.useOptimisticTypes();
86
87 final int programPoint = node.getProgramPoint();
88 final Type validType = compiler.getInvalidatedProgramPointType(programPoint);
89
90 if (validType != null) {
91 return validType;
92 }
93
94 final Type mostOptimisticType = node.getMostOptimisticType();
95 final Type evaluatedType = getEvaluatedType(node);
96
97 if (evaluatedType != null) {
98 if (evaluatedType.widerThan(mostOptimisticType)) {
99 final Type newValidType = evaluatedType.isObject() || evaluatedType.isBoolean() ? Type.OBJECT : evaluatedType;
100 // Update invalidatedProgramPoints so we don't re-evaluate the expression next time. This is a heuristic
101 // as we're doing a tradeoff. Re-evaluating expressions on each recompile takes time, but it might
102 // notice a widening in the type of the expression and thus prevent an unnecessary deoptimization later.
103 // We'll presume though that the types of expressions are mostly stable, so if we evaluated it in one
104 // compilation, we'll keep to that and risk a low-probability deoptimization if its type gets widened
105 // in the future.
106 compiler.addInvalidatedProgramPoint(node.getProgramPoint(), newValidType);
107 }
108 return evaluatedType;
109 }
110 return mostOptimisticType;
111 }
112
113 private static Type getPropertyType(final ScriptObject sobj, final String name) {
114 final FindProperty find = sobj.findProperty(name, true);
115 if (find == null) {
116 return null;
117 }
118
119 final Property property = find.getProperty();
120 final Class<?> propertyClass = property.getType();
121 if (propertyClass == null) {
122 // propertyClass == null means its value is Undefined. It is probably not initialized yet, so we won't make
123 // a type assumption yet.
124 return null;
125 } else if (propertyClass.isPrimitive()) {
126 return Type.typeFor(propertyClass);
127 }
128
129 final ScriptObject owner = find.getOwner();
130 if (property.hasGetterFunction(owner)) {
131 // Can have side effects, so we can't safely evaluate it; since !propertyClass.isPrimitive(), it's Object.
132 return Type.OBJECT;
133 }
134
135 // Safely evaluate the property, and return the narrowest type for the actual value (e.g. Type.INT for a boxed
136 // integer).
137 final Object value = property.needsDeclaration() ? ScriptRuntime.UNDEFINED : property.getObjectValue(owner, owner);
138 if (value == ScriptRuntime.UNDEFINED) {
139 return null;
140 }
141 return Type.typeFor(JSType.unboxedFieldType(value));
142 }
143
144 /**
145 * Declares a symbol name as belonging to a non-scoped local variable during an on-demand compilation of a single
146 * function. This method will add an explicit Undefined binding for the local into the runtime scope if it's
147 * otherwise implicitly undefined so that when an expression is evaluated for the name, it won't accidentally find
148 * an unrelated value higher up the scope chain. It is only required to call this method when doing an optimistic
149 * on-demand compilation.
150 * @param symbolName the name of the symbol that is to be declared as being a non-scoped local variable.
151 */
152 void declareLocalSymbol(final String symbolName) {
153 assert
154 compiler.useOptimisticTypes() &&
155 compiler.isOnDemandCompilation() &&
156 runtimeScope != null :
157 "useOptimistic=" +
158 compiler.useOptimisticTypes() +
159 " isOnDemand=" +
160 compiler.isOnDemandCompilation() +
161 " scope="+runtimeScope;
162
163 if (runtimeScope.findProperty(symbolName, false) == null) {
164 runtimeScope.addOwnProperty(symbolName, NOT_WRITABLE | NOT_ENUMERABLE | NOT_CONFIGURABLE, ScriptRuntime.UNDEFINED);
165 }
166 }
167
168 private Object evaluateSafely(final Expression expr) {
169 if (expr instanceof IdentNode) {
170 return runtimeScope == null ? null : evaluatePropertySafely(runtimeScope, ((IdentNode)expr).getName());
171 }
172
173 if (expr instanceof AccessNode) {
174 final AccessNode accessNode = (AccessNode)expr;
175 final Object base = evaluateSafely(accessNode.getBase());
176 if (!(base instanceof ScriptObject)) {
177 return null;
178 }
179 return evaluatePropertySafely((ScriptObject)base, accessNode.getProperty());
180 }
181
182 return null;
183 }
184
185 private static Object evaluatePropertySafely(final ScriptObject sobj, final String name) {
186 final FindProperty find = sobj.findProperty(name, true);
187 if (find == null) {
188 return null;
189 }
190 final Property property = find.getProperty();
191 final ScriptObject owner = find.getOwner();
192 if (property.hasGetterFunction(owner)) {
193 // Possible side effects; can't evaluate safely
194 return null;
195 }
196 return property.getObjectValue(owner, owner);
197 }
198
199
200 private Type getEvaluatedType(final Optimistic expr) {
201 if (expr instanceof IdentNode) {
202 if (runtimeScope == null) {
203 return null;
204 }
205 return getPropertyType(runtimeScope, ((IdentNode)expr).getName());
206 } else if (expr instanceof AccessNode) {
207 final AccessNode accessNode = (AccessNode)expr;
208 final Object base = evaluateSafely(accessNode.getBase());
209 if (!(base instanceof ScriptObject)) {
210 return null;
211 }
212 return getPropertyType((ScriptObject)base, accessNode.getProperty());
213 } else if (expr instanceof IndexNode) {
214 final IndexNode indexNode = (IndexNode)expr;
215 final Object base = evaluateSafely(indexNode.getBase());
216 if(base instanceof NativeArray || base instanceof ArrayBufferView) {
217 // NOTE: optimistic array getters throw UnwarrantedOptimismException based on the type of their
218 // underlying array storage, not based on values of individual elements. Thus, a LongArrayData will
219 // throw UOE for every optimistic int linkage attempt, even if the long value being returned in the
220 // first invocation would be representable as int. That way, we can presume that the array's optimistic
221 // type is the most optimistic type for which an element getter has a chance of executing successfully.
222 return ((ScriptObject)base).getArray().getOptimisticType();
223 }
224 } else if (expr instanceof CallNode) {
225 // Currently, we'll only try to guess the return type of immediately invoked function expressions with no
226 // parameters, that is (function() { ... })(). We could do better, but these are all heuristics and we can
227 // gradually introduce them as needed. An easy one would be to do the same for .call(this) idiom.
228 final CallNode callExpr = (CallNode)expr;
229 final Expression fnExpr = callExpr.getFunction();
230 // Skip evaluation if running with eager compilation as we may violate constraints in RecompilableScriptFunctionData
231 if (fnExpr instanceof FunctionNode && compiler.getContext().getEnv()._lazy_compilation) {
232 final FunctionNode fn = (FunctionNode)fnExpr;
233 if (callExpr.getArgs().isEmpty()) {
234 final RecompilableScriptFunctionData data = compiler.getScriptFunctionData(fn.getId());
235 if (data != null) {
236 final Type returnType = Type.typeFor(data.getReturnType(EMPTY_INVOCATION_TYPE, runtimeScope));
237 if (returnType == Type.BOOLEAN) {
238 // We don't have optimistic booleans. In fact, optimistic call sites getting back boolean
239 // currently deoptimize all the way to Object.
240 return Type.OBJECT;
241 }
242 assert returnType == Type.INT || returnType == Type.NUMBER || returnType == Type.OBJECT;
243 return returnType;
244 }
245 }
246 }
247 }
248
249 return null;
250 }
251 }