TypeEvaluator.java revision 971:c93b6091b11e 
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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.
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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).
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24 */
25
26package jdk.nashorn.internal.codegen;
27
28import static jdk.nashorn.internal.runtime.Property.NOT_CONFIGURABLE;
29import static jdk.nashorn.internal.runtime.Property.NOT_ENUMERABLE;
30import static jdk.nashorn.internal.runtime.Property.NOT_WRITABLE;
31
32import jdk.nashorn.internal.codegen.types.Type;
33import jdk.nashorn.internal.ir.AccessNode;
34import jdk.nashorn.internal.ir.Expression;
35import jdk.nashorn.internal.ir.IdentNode;
36import jdk.nashorn.internal.ir.IndexNode;
37import jdk.nashorn.internal.ir.Optimistic;
38import jdk.nashorn.internal.objects.NativeArray;
39import jdk.nashorn.internal.runtime.FindProperty;
40import jdk.nashorn.internal.runtime.JSType;
41import jdk.nashorn.internal.runtime.Property;
42import jdk.nashorn.internal.runtime.ScriptObject;
43import jdk.nashorn.internal.runtime.ScriptRuntime;
44
45/**
46 * Functionality for using a runtime scope to look up value types.
47 * Used during recompilation.
48 */
49final class TypeEvaluator {
50    private final Compiler compiler;
51    private final ScriptObject runtimeScope;
52
53    TypeEvaluator(final Compiler compiler, final ScriptObject runtimeScope) {
54        this.compiler = compiler;
55        this.runtimeScope = runtimeScope;
56    }
57
58    Type getOptimisticType(final Optimistic node) {
59        assert compiler.useOptimisticTypes();
60
61        final int  programPoint = node.getProgramPoint();
62        final Type validType    = compiler.getInvalidatedProgramPointType(programPoint);
63
64        if (validType != null) {
65            return validType;
66        }
67
68        final Type mostOptimisticType = node.getMostOptimisticType();
69        final Type evaluatedType      = getEvaluatedType(node);
70
71        if (evaluatedType != null) {
72            if (evaluatedType.widerThan(mostOptimisticType)) {
73                final Type newValidType = evaluatedType.isObject() || evaluatedType.isBoolean() ? Type.OBJECT : evaluatedType;
74                // Update invalidatedProgramPoints so we don't re-evaluate the expression next time. This is a heuristic
75                // as we're doing a tradeoff. Re-evaluating expressions on each recompile takes time, but it might
76                // notice a widening in the type of the expression and thus prevent an unnecessary deoptimization later.
77                // We'll presume though that the types of expressions are mostly stable, so if we evaluated it in one
78                // compilation, we'll keep to that and risk a low-probability deoptimization if its type gets widened
79                // in the future.
80                compiler.addInvalidatedProgramPoint(node.getProgramPoint(), newValidType);
81            }
82            return evaluatedType;
83        }
84        return mostOptimisticType;
85    }
86
87    private static Type getPropertyType(final ScriptObject sobj, final String name) {
88        final FindProperty find = sobj.findProperty(name, true);
89        if (find == null) {
90            return null;
91        }
92
93        final Property property      = find.getProperty();
94        final Class<?> propertyClass = property.getCurrentType();
95        if (propertyClass == null) {
96            // propertyClass == null means its value is Undefined. It is probably not initialized yet, so we won't make
97            // a type assumption yet.
98            return null;
99        } else if (propertyClass.isPrimitive()) {
100            return Type.typeFor(propertyClass);
101        }
102
103        final ScriptObject owner = find.getOwner();
104        if (property.hasGetterFunction(owner)) {
105            // Can have side effects, so we can't safely evaluate it; since !propertyClass.isPrimitive(), it's Object.
106            return Type.OBJECT;
107        }
108
109        // Safely evaluate the property, and return the narrowest type for the actual value (e.g. Type.INT for a boxed
110        // integer).
111        final Object value = property.getObjectValue(owner, owner);
112        if (value == ScriptRuntime.UNDEFINED) {
113            return null;
114        }
115        return Type.typeFor(JSType.unboxedFieldType(value));
116    }
117
118    /**
119     * Declares a symbol name as belonging to a non-scoped local variable during an on-demand compilation of a single
120     * function. This method will add an explicit Undefined binding for the local into the runtime scope if it's
121     * otherwise implicitly undefined so that when an expression is evaluated for the name, it won't accidentally find
122     * an unrelated value higher up the scope chain. It is only required to call this method when doing an optimistic
123     * on-demand compilation.
124     * @param symbolName the name of the symbol that is to be declared as being a non-scoped local variable.
125     */
126    void declareLocalSymbol(final String symbolName) {
127        assert
128            compiler.useOptimisticTypes() &&
129            compiler.isOnDemandCompilation() &&
130            runtimeScope != null :
131                "useOptimistic=" +
132                    compiler.useOptimisticTypes() +
133                    " isOnDemand=" +
134                    compiler.isOnDemandCompilation() +
135                    " scope="+runtimeScope;
136
137        if (runtimeScope.findProperty(symbolName, false) == null) {
138            runtimeScope.addOwnProperty(symbolName, NOT_WRITABLE | NOT_ENUMERABLE | NOT_CONFIGURABLE, ScriptRuntime.UNDEFINED);
139        }
140    }
141
142    private Object evaluateSafely(final Expression expr) {
143        if (expr instanceof IdentNode) {
144            return runtimeScope == null ? null : evaluatePropertySafely(runtimeScope, ((IdentNode)expr).getName());
145        }
146
147        if (expr instanceof AccessNode) {
148            final AccessNode accessNode = (AccessNode)expr;
149            final Object     base       = evaluateSafely(accessNode.getBase());
150            if (!(base instanceof ScriptObject)) {
151                return null;
152            }
153            return evaluatePropertySafely((ScriptObject)base, accessNode.getProperty());
154        }
155
156        return null;
157    }
158
159    private static Object evaluatePropertySafely(final ScriptObject sobj, final String name) {
160        final FindProperty find = sobj.findProperty(name, true);
161        if (find == null) {
162            return null;
163        }
164        final Property     property = find.getProperty();
165        final ScriptObject owner    = find.getOwner();
166        if (property.hasGetterFunction(owner)) {
167            // Possible side effects; can't evaluate safely
168            return null;
169        }
170        return property.getObjectValue(owner, owner);
171    }
172
173
174    private Type getEvaluatedType(final Optimistic expr) {
175        if (expr instanceof IdentNode) {
176            if (runtimeScope == null) {
177                return null;
178            }
179            return getPropertyType(runtimeScope, ((IdentNode)expr).getName());
180        }
181
182        if (expr instanceof AccessNode) {
183            final AccessNode accessNode = (AccessNode)expr;
184            final Object base = evaluateSafely(accessNode.getBase());
185            if (!(base instanceof ScriptObject)) {
186                return null;
187            }
188            return getPropertyType((ScriptObject)base, accessNode.getProperty());
189        }
190
191        if (expr instanceof IndexNode) {
192            final IndexNode indexNode = (IndexNode)expr;
193            final Object    base = evaluateSafely(indexNode.getBase());
194            if(!(base instanceof NativeArray)) {
195                // We only know how to deal with NativeArray. TODO: maybe manage buffers too
196                return null;
197            }
198            // NOTE: optimistic array getters throw UnwarrantedOptimismException based on the type of their underlying
199            // array storage, not based on values of individual elements. Thus, a LongArrayData will throw UOE for every
200            // optimistic int linkage attempt, even if the long value being returned in the first invocation would be
201            // representable as int. That way, we can presume that the array's optimistic type is the most optimistic
202            // type for which an element getter has a chance of executing successfully.
203            return ((NativeArray)base).getArray().getOptimisticType();
204        }
205
206        return null;
207    }
208}
209