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 #include "escape.h"
18
19 #include "nodes.h"
20
21 namespace art {
22
CalculateEscape(HInstruction * reference,bool (* no_escape)(HInstruction *,HInstruction *),bool * is_singleton,bool * is_singleton_and_not_returned,bool * is_singleton_and_not_deopt_visible)23 void CalculateEscape(HInstruction* reference,
24 bool (*no_escape)(HInstruction*, HInstruction*),
25 /*out*/ bool* is_singleton,
26 /*out*/ bool* is_singleton_and_not_returned,
27 /*out*/ bool* is_singleton_and_not_deopt_visible) {
28 // For references not allocated in the method, don't assume anything.
29 if (!reference->IsNewInstance() && !reference->IsNewArray()) {
30 *is_singleton = false;
31 *is_singleton_and_not_returned = false;
32 *is_singleton_and_not_deopt_visible = false;
33 return;
34 }
35 // Assume the best until proven otherwise.
36 *is_singleton = true;
37 *is_singleton_and_not_returned = true;
38 *is_singleton_and_not_deopt_visible = true;
39 // Visit all uses to determine if this reference can escape into the heap,
40 // a method call, an alias, etc.
41 for (const HUseListNode<HInstruction*>& use : reference->GetUses()) {
42 HInstruction* user = use.GetUser();
43 if (no_escape != nullptr && (*no_escape)(reference, user)) {
44 // Client supplied analysis says there is no escape.
45 continue;
46 } else if (user->IsBoundType() || user->IsNullCheck()) {
47 // BoundType shouldn't normally be necessary for an allocation. Just be conservative
48 // for the uncommon cases. Similarly, null checks are eventually eliminated for explicit
49 // allocations, but if we see one before it is simplified, assume an alias.
50 *is_singleton = false;
51 *is_singleton_and_not_returned = false;
52 *is_singleton_and_not_deopt_visible = false;
53 return;
54 } else if (user->IsPhi() || user->IsSelect() || user->IsInvoke() ||
55 (user->IsInstanceFieldSet() && (reference == user->InputAt(1))) ||
56 (user->IsUnresolvedInstanceFieldSet() && (reference == user->InputAt(1))) ||
57 (user->IsStaticFieldSet() && (reference == user->InputAt(1))) ||
58 (user->IsUnresolvedStaticFieldSet() && (reference == user->InputAt(0))) ||
59 (user->IsArraySet() && (reference == user->InputAt(2)))) {
60 // The reference is merged to HPhi/HSelect, passed to a callee, or stored to heap.
61 // Hence, the reference is no longer the only name that can refer to its value.
62 *is_singleton = false;
63 *is_singleton_and_not_returned = false;
64 *is_singleton_and_not_deopt_visible = false;
65 return;
66 } else if ((user->IsUnresolvedInstanceFieldGet() && (reference == user->InputAt(0))) ||
67 (user->IsUnresolvedInstanceFieldSet() && (reference == user->InputAt(0)))) {
68 // The field is accessed in an unresolved way. We mark the object as a non-singleton.
69 // Note that we could optimize this case and still perform some optimizations until
70 // we hit the unresolved access, but the conservative assumption is the simplest.
71 *is_singleton = false;
72 *is_singleton_and_not_returned = false;
73 *is_singleton_and_not_deopt_visible = false;
74 return;
75 } else if (user->IsReturn()) {
76 *is_singleton_and_not_returned = false;
77 }
78 }
79
80 // Look at the environment uses if it's for HDeoptimize. Other environment uses are fine,
81 // as long as client optimizations that rely on this information are disabled for debuggable.
82 for (const HUseListNode<HEnvironment*>& use : reference->GetEnvUses()) {
83 HEnvironment* user = use.GetUser();
84 if (user->GetHolder()->IsDeoptimize()) {
85 *is_singleton_and_not_deopt_visible = false;
86 break;
87 }
88 }
89 }
90
DoesNotEscape(HInstruction * reference,bool (* no_escape)(HInstruction *,HInstruction *))91 bool DoesNotEscape(HInstruction* reference, bool (*no_escape)(HInstruction*, HInstruction*)) {
92 bool is_singleton = false;
93 bool is_singleton_and_not_returned = false;
94 bool is_singleton_and_not_deopt_visible = false; // not relevant for escape
95 CalculateEscape(reference,
96 no_escape,
97 &is_singleton,
98 &is_singleton_and_not_returned,
99 &is_singleton_and_not_deopt_visible);
100 return is_singleton_and_not_returned;
101 }
102
103 } // namespace art
104