Mercurial > hg > truffle
diff graal/com.oracle.truffle.api/src/com/oracle/truffle/api/utilities/AssumedValue.java @ 13322:f28ea693056f
New assumption utilities.
author | Chris Seaton <chris.seaton@oracle.com> |
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date | Fri, 13 Dec 2013 15:53:30 +0000 |
parents | |
children | 0e7894989f37 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/utilities/AssumedValue.java Fri Dec 13 15:53:30 2013 +0000 @@ -0,0 +1,68 @@ +/* + * Copyright (c) 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 com.oracle.truffle.api.utilities; + +import com.oracle.truffle.api.*; +import com.oracle.truffle.api.CompilerDirectives.CompilationFinal; +import com.oracle.truffle.api.nodes.*; + +/** + * A {@link CompilationFinal} value combined with an {@link Assumption} to notify when it changes. + * Note that you should be careful that modifications to this value do not cause deoptimization + * loops. This could be by using a value that is monotonic. + */ +public class AssumedValue<T> { + + @CompilationFinal private T value; + private final CyclicAssumption assumption; + + public AssumedValue(String name, T initialValue) { + assumption = new CyclicAssumption(name); + value = initialValue; + } + + /** + * Get the current value, updating it if it has been {@link #set}. The compiler may be able to + * make this method return a constant value, but still accommodate mutation. + */ + public T get() { + try { + assumption.getAssumption().check(); + } catch (InvalidAssumptionException e) { + // No need to rewrite anything - just pick up the new value + } + + return value; + } + + /** + * Set a new value, which will be picked up the next time {@link #get} is called. + */ + public void set(T newValue) { + value = newValue; + assumption.invalidate(); + } + +}