1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_COMPILER_OPTIMIZING_ESCAPE_H_
18#define ART_COMPILER_OPTIMIZING_ESCAPE_H_
19
20namespace art {
21
22class HInstruction;
23
24/*
25 * Methods related to escape analysis, i.e. determining whether an object
26 * allocation is visible outside ('escapes') its immediate method context.
27 */
28
29/*
30 * Performs escape analysis on the given instruction, typically a reference to an
31 * allocation. The method assigns true to parameter 'is_singleton' if the reference
32 * is the only name that can refer to its value during the lifetime of the method,
33 * meaning that the reference is not aliased with something else, is not stored to
34 * heap memory, and not passed to another method. In addition, the method assigns
35 * true to parameter 'is_singleton_and_not_returned' if the reference is a singleton
36 * and not returned to the caller and to parameter 'is_singleton_and_not_deopt_visible'
37 * if the reference is a singleton and not used as an environment local of an
38 * HDeoptimize instruction (clients of the final value must run after BCE to ensure
39 * all such instructions have been introduced already).
40 *
41 * Note that being visible to a HDeoptimize instruction does not count for ordinary
42 * escape analysis, since switching between compiled code and interpreted code keeps
43 * non escaping references restricted to the lifetime of the method and the thread
44 * executing it. This property only concerns optimizations that are interested in
45 * escape analysis with respect to the *compiled* code (such as LSE).
46 *
47 * When set, the no_escape function is applied to any use of the allocation instruction
48 * prior to any built-in escape analysis. This allows clients to define better escape
49 * analysis in certain case-specific circumstances. If 'no_escape(reference, user)'
50 * returns true, the user is assumed *not* to cause any escape right away. The return
51 * value false means the client cannot provide a definite answer and built-in escape
52 * analysis is applied to the user instead.
53 */
54void CalculateEscape(HInstruction* reference,
55                     bool (*no_escape)(HInstruction*, HInstruction*),
56                     /*out*/ bool* is_singleton,
57                     /*out*/ bool* is_singleton_and_not_returned,
58                     /*out*/ bool* is_singleton_and_not_deopt_visible);
59
60/*
61 * Convenience method for testing the singleton and not returned properties at once.
62 * Callers should be aware that this method invokes the full analysis at each call.
63 */
64bool DoesNotEscape(HInstruction* reference, bool (*no_escape)(HInstruction*, HInstruction*));
65
66}  // namespace art
67
68#endif  // ART_COMPILER_OPTIMIZING_ESCAPE_H_
69