1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "load_store_analysis.h"
namespace art {
// A cap for the number of heap locations to prevent pathological time/space consumption.
// The number of heap locations for most of the methods stays below this threshold.
constexpr size_t kMaxNumberOfHeapLocations = 32;
// Test if two integer ranges [l1,h1] and [l2,h2] overlap.
// Note that the ranges are inclusive on both ends.
// l1|------|h1
// l2|------|h2
static bool CanIntegerRangesOverlap(int64_t l1, int64_t h1, int64_t l2, int64_t h2) {
return std::max(l1, l2) <= std::min(h1, h2);
}
static bool IsAddOrSub(const HInstruction* instruction) {
return instruction->IsAdd() || instruction->IsSub();
}
static bool CanBinaryOpAndIndexAlias(const HBinaryOperation* idx1,
const size_t vector_length1,
const HInstruction* idx2,
const size_t vector_length2) {
if (!IsAddOrSub(idx1)) {
// We currently only support Add and Sub operations.
return true;
}
if (idx1->AsBinaryOperation()->GetLeastConstantLeft() != idx2) {
// Cannot analyze [i+CONST1] and [j].
return true;
}
if (!idx1->GetConstantRight()->IsIntConstant()) {
return true;
}
// Since 'i' are the same in [i+CONST] and [i],
// further compare [CONST] and [0].
int64_t l1 = idx1->IsAdd() ?
idx1->GetConstantRight()->AsIntConstant()->GetValue() :
-idx1->GetConstantRight()->AsIntConstant()->GetValue();
int64_t l2 = 0;
int64_t h1 = l1 + (vector_length1 - 1);
int64_t h2 = l2 + (vector_length2 - 1);
return CanIntegerRangesOverlap(l1, h1, l2, h2);
}
static bool CanBinaryOpsAlias(const HBinaryOperation* idx1,
const size_t vector_length1,
const HBinaryOperation* idx2,
const size_t vector_length2) {
if (!IsAddOrSub(idx1) || !IsAddOrSub(idx2)) {
// We currently only support Add and Sub operations.
return true;
}
if (idx1->AsBinaryOperation()->GetLeastConstantLeft() !=
idx2->AsBinaryOperation()->GetLeastConstantLeft()) {
// Cannot analyze [i+CONST1] and [j+CONST2].
return true;
}
if (!idx1->GetConstantRight()->IsIntConstant() ||
!idx2->GetConstantRight()->IsIntConstant()) {
return true;
}
// Since 'i' are the same in [i+CONST1] and [i+CONST2],
// further compare [CONST1] and [CONST2].
int64_t l1 = idx1->IsAdd() ?
idx1->GetConstantRight()->AsIntConstant()->GetValue() :
-idx1->GetConstantRight()->AsIntConstant()->GetValue();
int64_t l2 = idx2->IsAdd() ?
idx2->GetConstantRight()->AsIntConstant()->GetValue() :
-idx2->GetConstantRight()->AsIntConstant()->GetValue();
int64_t h1 = l1 + (vector_length1 - 1);
int64_t h2 = l2 + (vector_length2 - 1);
return CanIntegerRangesOverlap(l1, h1, l2, h2);
}
bool HeapLocationCollector::CanArrayElementsAlias(const HInstruction* idx1,
const size_t vector_length1,
const HInstruction* idx2,
const size_t vector_length2) const {
DCHECK(idx1 != nullptr);
DCHECK(idx2 != nullptr);
DCHECK_GE(vector_length1, HeapLocation::kScalar);
DCHECK_GE(vector_length2, HeapLocation::kScalar);
// [i] and [i].
if (idx1 == idx2) {
return true;
}
// [CONST1] and [CONST2].
if (idx1->IsIntConstant() && idx2->IsIntConstant()) {
int64_t l1 = idx1->AsIntConstant()->GetValue();
int64_t l2 = idx2->AsIntConstant()->GetValue();
// To avoid any overflow in following CONST+vector_length calculation,
// use int64_t instead of int32_t.
int64_t h1 = l1 + (vector_length1 - 1);
int64_t h2 = l2 + (vector_length2 - 1);
return CanIntegerRangesOverlap(l1, h1, l2, h2);
}
// [i+CONST] and [i].
if (idx1->IsBinaryOperation() &&
idx1->AsBinaryOperation()->GetConstantRight() != nullptr &&
idx1->AsBinaryOperation()->GetLeastConstantLeft() == idx2) {
return CanBinaryOpAndIndexAlias(idx1->AsBinaryOperation(),
vector_length1,
idx2,
vector_length2);
}
// [i] and [i+CONST].
if (idx2->IsBinaryOperation() &&
idx2->AsBinaryOperation()->GetConstantRight() != nullptr &&
idx2->AsBinaryOperation()->GetLeastConstantLeft() == idx1) {
return CanBinaryOpAndIndexAlias(idx2->AsBinaryOperation(),
vector_length2,
idx1,
vector_length1);
}
// [i+CONST1] and [i+CONST2].
if (idx1->IsBinaryOperation() &&
idx1->AsBinaryOperation()->GetConstantRight() != nullptr &&
idx2->IsBinaryOperation() &&
idx2->AsBinaryOperation()->GetConstantRight() != nullptr) {
return CanBinaryOpsAlias(idx1->AsBinaryOperation(),
vector_length1,
idx2->AsBinaryOperation(),
vector_length2);
}
// By default, MAY alias.
return true;
}
bool LoadStoreAnalysis::Run() {
for (HBasicBlock* block : graph_->GetReversePostOrder()) {
heap_location_collector_.VisitBasicBlock(block);
}
if (heap_location_collector_.GetNumberOfHeapLocations() > kMaxNumberOfHeapLocations) {
// Bail out if there are too many heap locations to deal with.
heap_location_collector_.CleanUp();
return false;
}
if (!heap_location_collector_.HasHeapStores()) {
// Without heap stores, this pass would act mostly as GVN on heap accesses.
heap_location_collector_.CleanUp();
return false;
}
if (heap_location_collector_.HasVolatile() || heap_location_collector_.HasMonitorOps()) {
// Don't do load/store elimination if the method has volatile field accesses or
// monitor operations, for now.
// TODO: do it right.
heap_location_collector_.CleanUp();
return false;
}
heap_location_collector_.BuildAliasingMatrix();
return true;
}
} // namespace art
|
