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comparison truffle/com.oracle.truffle.api/src/com/oracle/truffle/api/Assumption.java @ 21951:9c8c0937da41

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Moving all sources into truffle subdirectory
author Jaroslav Tulach <jaroslav.tulach@oracle.com>
date Wed, 17 Jun 2015 10:58:08 +0200
parents graal/com.oracle.truffle.api/src/com/oracle/truffle/api/Assumption.java@db090a8d3705
children dc83cc1f94f2
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21950:2a5011c7e641 21951:9c8c0937da41
1 /*
2 * Copyright (c) 2012, 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 package com.oracle.truffle.api;
26
27 import com.oracle.truffle.api.nodes.*;
28
29 /**
30 * An assumption is a global boolean flag that starts with the value true (i.e., the assumption is
31 * valid) and can subsequently be invalidated (using {@link Assumption#invalidate()}). Once
32 * invalidated, an assumption can never get valid again. Assumptions can be created using the
33 * {@link TruffleRuntime#createAssumption()} or the {@link TruffleRuntime#createAssumption(String)}
34 * method. The Truffle compiler has special knowledge of this class in order to produce efficient
35 * machine code for checking an assumption in case the assumption object is a compile time constant.
36 * Therefore, assumptions should be stored in final fields in Truffle nodes.
37 *
38 * All instances of classes implementing {@code Assumption} must be held in {@code final} fields for
39 * compiler optimizations to take effect.
40 */
41 public interface Assumption {
42
43 /**
44 * Checks that this assumption is still valid. The method throws an exception, if this is no
45 * longer the case. This method is preferred over the {@link #isValid()} method when writing
46 * guest language interpreter code. The catch block should perform a node rewrite (see
47 * {@link Node#replace(Node)}) with a node that no longer relies on the assumption.
48 *
49 * @throws InvalidAssumptionException If the assumption is no longer valid.
50 */
51 void check() throws InvalidAssumptionException;
52
53 /**
54 * Checks whether the assumption is still valid.
55 *
56 * @return a boolean value indicating the validity of the assumption
57 */
58 boolean isValid();
59
60 /**
61 * Invalidates this assumption. Performs no operation, if the assumption is already invalid.
62 */
63 void invalidate();
64
65 /**
66 * A name for the assumption that is used for debug output.
67 *
68 * @return the name of the assumption
69 */
70 String getName();
71 }