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/*
* 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;
import jdk.nashorn.internal.runtime.options.Options;
class SpecializedMethodChooser {
/** Should specialized function and specialized constructors for the builtin be used if available? */
private static final boolean DISABLE_SPECIALIZATION = Options.getBooleanProperty("nashorn.scriptfunction.specialization.disable");
static MethodHandle candidateWithLowestWeight(final MethodType descType, final MethodHandle initialCandidate, final MethodHandle[] specs) {
if (DISABLE_SPECIALIZATION || specs == null) {
return initialCandidate;
}
int minimumWeight = Integer.MAX_VALUE;
MethodHandle candidate = initialCandidate;
for (final MethodHandle spec : specs) {
final MethodType specType = spec.type();
if (!typeCompatible(descType, specType)) {
continue;
}
//return type is ok. we want a wider or equal one for our callsite.
final int specWeight = weigh(specType);
if (specWeight < minimumWeight) {
candidate = spec;
minimumWeight = specWeight;
}
}
return candidate;
}
private static boolean typeCompatible(final MethodType desc, final MethodType spec) {
//spec must fit in desc
final Class<?>[] dparray = desc.parameterArray();
final Class<?>[] sparray = spec.parameterArray();
if (dparray.length != sparray.length) {
return false;
}
for (int i = 0; i < dparray.length; i++) {
final Type dp = Type.typeFor(dparray[i]);
final Type sp = Type.typeFor(sparray[i]);
if (dp.isBoolean()) {
return false; //don't specialize on booleans, we have the "true" vs int 1 ambiguity in resolution
}
//specialization arguments must be at least as wide as dp, if not wider
if (Type.widest(dp, sp) != sp) {
//e.g. specialization takes double and callsite says "object". reject.
//but if specialization says 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.
}
private static int weigh(final MethodType t) {
int weight = Type.typeFor(t.returnType()).getWeight();
for (final Class<?> paramType : t.parameterArray()) {
final int pweight = Type.typeFor(paramType).getWeight();
weight += pweight;
}
return weight;
}
}
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