1 /* Copyright (C) 2018 The Android Open Source Project
2 *
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15
16 #include "instruction_simplifier_x86_shared.h"
17 #include "nodes_x86.h"
18
19 namespace art {
20
TryCombineAndNot(HAnd * instruction)21 bool TryCombineAndNot(HAnd* instruction) {
22 DataType::Type type = instruction->GetType();
23 if (!DataType::IsIntOrLongType(type)) {
24 return false;
25 }
26 // Replace code looking like
27 // Not tmp, y
28 // And dst, x, tmp
29 // with
30 // AndNot dst, x, y
31 HInstruction* left = instruction->GetLeft();
32 HInstruction* right = instruction->GetRight();
33 // Perform simplication only when either left or right
34 // is Not. When both are Not, instruction should be simplified with
35 // DeMorgan's Laws.
36 if (left->IsNot() ^ right->IsNot()) {
37 bool left_is_not = left->IsNot();
38 HInstruction* other_ins = (left_is_not ? right : left);
39 HNot* not_ins = (left_is_not ? left : right)->AsNot();
40 // Only do the simplification if instruction has only one use
41 // and thus can be safely removed.
42 if (not_ins->HasOnlyOneNonEnvironmentUse()) {
43 ArenaAllocator* arena = instruction->GetBlock()->GetGraph()->GetAllocator();
44 HX86AndNot* and_not = new (arena) HX86AndNot(type,
45 not_ins->GetInput(),
46 other_ins,
47 instruction->GetDexPc());
48 instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, and_not);
49 DCHECK(!not_ins->HasUses());
50 not_ins->GetBlock()->RemoveInstruction(not_ins);
51 return true;
52 }
53 }
54 return false;
55 }
56
TryGenerateResetLeastSetBit(HAnd * instruction)57 bool TryGenerateResetLeastSetBit(HAnd* instruction) {
58 DataType::Type type = instruction->GetType();
59 if (!DataType::IsIntOrLongType(type)) {
60 return false;
61 }
62 // Replace code looking like
63 // Add tmp, x, -1 or Sub tmp, x, 1
64 // And dest x, tmp
65 // with
66 // MaskOrResetLeastSetBit dest, x
67 HInstruction* candidate = nullptr;
68 HInstruction* other = nullptr;
69 HInstruction* left = instruction->GetLeft();
70 HInstruction* right = instruction->GetRight();
71 if (AreLeastSetBitInputs(left, right)) {
72 candidate = left;
73 other = right;
74 } else if (AreLeastSetBitInputs(right, left)) {
75 candidate = right;
76 other = left;
77 }
78 if (candidate != nullptr && candidate->HasOnlyOneNonEnvironmentUse()) {
79 ArenaAllocator* arena = instruction->GetBlock()->GetGraph()->GetAllocator();
80 HX86MaskOrResetLeastSetBit* lsb = new (arena) HX86MaskOrResetLeastSetBit(
81 type, HInstruction::kAnd, other, instruction->GetDexPc());
82 instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, lsb);
83 DCHECK(!candidate->HasUses());
84 candidate->GetBlock()->RemoveInstruction(candidate);
85 return true;
86 }
87 return false;
88 }
89
TryGenerateMaskUptoLeastSetBit(HXor * instruction)90 bool TryGenerateMaskUptoLeastSetBit(HXor* instruction) {
91 DataType::Type type = instruction->GetType();
92 if (!DataType::IsIntOrLongType(type)) {
93 return false;
94 }
95 // Replace code looking like
96 // Add tmp, x, -1 or Sub tmp, x, 1
97 // Xor dest x, tmp
98 // with
99 // MaskOrResetLeastSetBit dest, x
100 HInstruction* left = instruction->GetLeft();
101 HInstruction* right = instruction->GetRight();
102 HInstruction* other = nullptr;
103 HInstruction* candidate = nullptr;
104 if (AreLeastSetBitInputs(left, right)) {
105 candidate = left;
106 other = right;
107 } else if (AreLeastSetBitInputs(right, left)) {
108 candidate = right;
109 other = left;
110 }
111 if (candidate != nullptr && candidate->HasOnlyOneNonEnvironmentUse()) {
112 ArenaAllocator* arena = instruction->GetBlock()->GetGraph()->GetAllocator();
113 HX86MaskOrResetLeastSetBit* lsb = new (arena) HX86MaskOrResetLeastSetBit(
114 type, HInstruction::kXor, other, instruction->GetDexPc());
115 instruction->GetBlock()->ReplaceAndRemoveInstructionWith(instruction, lsb);
116 DCHECK(!candidate->HasUses());
117 candidate->GetBlock()->RemoveInstruction(candidate);
118 return true;
119 }
120 return false;
121 }
122
AreLeastSetBitInputs(HInstruction * to_test,HInstruction * other)123 bool AreLeastSetBitInputs(HInstruction* to_test, HInstruction* other) {
124 if (to_test->IsAdd()) {
125 HAdd* add = to_test->AsAdd();
126 HConstant* cst = add->GetConstantRight();
127 return cst != nullptr && cst->IsMinusOne() && other == add->GetLeastConstantLeft();
128 }
129 if (to_test->IsSub()) {
130 HSub* sub = to_test->AsSub();
131 HConstant* cst = sub->GetConstantRight();
132 return cst != nullptr && cst->IsOne() && other == sub->GetLeastConstantLeft();
133 }
134 return false;
135 }
136
137 } // namespace art
138