Mercurial > jdk8-mips64-public > nashorn / file revision

 /*

  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  */

 package jdk.nashorn.internal.runtime;

 import java.lang.invoke.MethodHandle;

 import java.lang.invoke.MethodType;

 import jdk.nashorn.internal.codegen.types.Type;

 /**

  * An version of a JavaScript function, native or JavaScript.

  * Supports lazily generating a constructor version of the invocation.

  */

 final class CompiledFunction implements Comparable<CompiledFunction> {

     private final MethodHandle invoker;

     private MethodHandle constructor;

     CompiledFunction(final MethodHandle invoker) {

         this(invoker, null);

     }

     CompiledFunction(final MethodHandle invoker, final MethodHandle constructor) {

         this.invoker = invoker;

         this.constructor = constructor; //isConstructor

     }

     @Override

     public String toString() {

         return "<invoker=" + invoker + " ctor=" + constructor + ">";

     }

     MethodHandle getInvoker() {

         return invoker;

     }

     MethodHandle getConstructor() {

         return constructor;

     }

     void setConstructor(final MethodHandle constructor) {

         this.constructor = constructor;

     }

     boolean hasConstructor() {

         return constructor != null;

     }

     MethodType type() {

         return invoker.type();

     }

     @Override

     public int compareTo(final CompiledFunction o) {

         return weight() - o.weight();

     }

     private int weight() {

         return weight(type());

     }

     private static int weight(final MethodType type) {

         if (isVarArgsType(type)) {

             return Integer.MAX_VALUE; //if there is a varargs it should be the heavist and last fallback

         }

         int weight = Type.typeFor(type.returnType()).getWeight();

         for (final Class<?> paramType : type.parameterArray()) {

             final int pweight = Type.typeFor(paramType).getWeight();

             weight += pweight;

         }

         return weight;

     }

     private static boolean isVarArgsType(final MethodType type) {

         assert type.parameterCount() >= 1 : type;

         return type.parameterType(type.parameterCount() - 1) == Object[].class;

     }

     boolean moreGenericThan(final CompiledFunction o) {

         return weight() > o.weight();

     }

     boolean moreGenericThan(final MethodType type) {

         return weight() > weight(type);

     }

     /**

      * Check whether a given method descriptor is compatible with this invocation.

      * It is compatible if the types are narrower than the invocation type so that

      * a semantically equivalent linkage can be performed.

      *

      * @param typesc

      * @return

      */

     boolean typeCompatible(final MethodType type) {

         final Class<?>[] wantedParams   = type.parameterArray();

         final Class<?>[] existingParams = type().parameterArray();

         //if we are not examining a varargs type, the number of parameters must be the same

         if (wantedParams.length != existingParams.length && !isVarArgsType(type)) {

             return false;

         }

         //we only go as far as the shortest array. the only chance to make this work if

         //parameters lengths do not match is if our type ends with a varargs argument.

         //then every trailing parameter in the given callsite can be folded into it, making

         //us compatible (albeit slower than a direct specialization)

         final int lastParamIndex = Math.min(wantedParams.length, existingParams.length);

         for (int i = 0; i < lastParamIndex; i++) {

             final Type w = Type.typeFor(wantedParams[i]);

             final Type e = Type.typeFor(existingParams[i]);

             //don't specialize on booleans, we have the "true" vs int 1 ambiguity in resolution

             //we also currently don't support boolean as a javascript function callsite type.

             //it will always box.

             if (w.isBoolean()) {

                 return false;

             }

             //This callsite type has a vararg here. it will swallow all remaining args.

             //for consistency, check that it's the last argument

             if (e.isArray()) {

                 return true;

             }

             //Our arguments must be at least as wide as the wanted one, if not wider

             if (Type.widest(w, e) != e) {

                 //e.g. this invocation takes double and callsite says "object". reject. won't fit

                 //but if invocation takes a double and callsite says "int" or "long" or "double", that's fine

                 return false;

             }

         }

         return true; // anything goes for return type, take the convenient one and it will be upcasted thru dynalink magic.

     }

 }