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
|
/*
*
* Copyright (C) 2014 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 "dex_instruction.h"
#include "builder.h"
#include "nodes.h"
namespace art {
HGraph* HGraphBuilder::BuildGraph(const uint16_t* code_ptr, const uint16_t* code_end) {
// Setup the graph with the entry block and exit block.
graph_ = new (arena_) HGraph(arena_);
entry_block_ = new (arena_) HBasicBlock(graph_);
graph_->AddBlock(entry_block_);
entry_block_->AddInstruction(new (arena_) HGoto());
exit_block_ = new (arena_) HBasicBlock(graph_);
exit_block_->AddInstruction(new (arena_) HExit());
// To avoid splitting blocks, we compute ahead of time the instructions that
// start a new block, and create these blocks.
ComputeBranchTargets(code_ptr, code_end);
size_t dex_offset = 0;
while (code_ptr < code_end) {
// Update the current block if dex_offset starts a new block.
MaybeUpdateCurrentBlock(dex_offset);
const Instruction& instruction = *Instruction::At(code_ptr);
if (!AnalyzeDexInstruction(instruction, dex_offset)) return nullptr;
dex_offset += instruction.SizeInCodeUnits();
code_ptr += instruction.SizeInCodeUnits();
}
// Add the exit block at the end to give it the highest id.
graph_->AddBlock(exit_block_);
return graph_;
}
void HGraphBuilder::MaybeUpdateCurrentBlock(size_t index) {
HBasicBlock* block = FindBlockStartingAt(index);
if (block == nullptr) return;
if (current_block_ != nullptr) {
// Branching instructions clear current_block, so we know
// the last instruction of the current block is not a branching
// instruction. We add an unconditional goto to the found block.
current_block_->AddInstruction(new (arena_) HGoto());
current_block_->AddSuccessor(block);
}
graph_->AddBlock(block);
current_block_ = block;
}
void HGraphBuilder::ComputeBranchTargets(const uint16_t* code_ptr, const uint16_t* code_end) {
// TODO: Support switch instructions.
branch_targets_.SetSize(code_end - code_ptr);
// Create the first block for the dex instructions, single successor of the entry block.
HBasicBlock* block = new (arena_) HBasicBlock(graph_);
branch_targets_.Put(0, block);
entry_block_->AddSuccessor(block);
// Iterate over all instructions and find branching instructions. Create blocks for
// the locations these instructions branch to.
size_t dex_offset = 0;
while (code_ptr < code_end) {
const Instruction& instruction = *Instruction::At(code_ptr);
if (instruction.IsBranch()) {
int32_t target = instruction.GetTargetOffset() + dex_offset;
// Create a block for the target instruction.
if (FindBlockStartingAt(target) == nullptr) {
block = new (arena_) HBasicBlock(graph_);
branch_targets_.Put(target, block);
}
dex_offset += instruction.SizeInCodeUnits();
code_ptr += instruction.SizeInCodeUnits();
if ((code_ptr < code_end) && (FindBlockStartingAt(dex_offset) == nullptr)) {
block = new (arena_) HBasicBlock(graph_);
branch_targets_.Put(dex_offset, block);
}
} else {
code_ptr += instruction.SizeInCodeUnits();
dex_offset += instruction.SizeInCodeUnits();
}
}
}
HBasicBlock* HGraphBuilder::FindBlockStartingAt(int32_t index) const {
DCHECK_GE(index, 0);
return branch_targets_.Get(index);
}
bool HGraphBuilder::AnalyzeDexInstruction(const Instruction& instruction, int32_t dex_offset) {
if (current_block_ == nullptr) return true; // Dead code
switch (instruction.Opcode()) {
case Instruction::RETURN_VOID:
current_block_->AddInstruction(new (arena_) HReturnVoid());
current_block_->AddSuccessor(exit_block_);
current_block_ = nullptr;
break;
case Instruction::IF_EQ: {
// TODO: Read the dex register.
HBasicBlock* target = FindBlockStartingAt(instruction.GetTargetOffset() + dex_offset);
DCHECK(target != nullptr);
current_block_->AddInstruction(new (arena_) HIf());
current_block_->AddSuccessor(target);
target = FindBlockStartingAt(dex_offset + instruction.SizeInCodeUnits());
DCHECK(target != nullptr);
current_block_->AddSuccessor(target);
current_block_ = nullptr;
break;
}
case Instruction::GOTO:
case Instruction::GOTO_16:
case Instruction::GOTO_32: {
HBasicBlock* target = FindBlockStartingAt(instruction.GetTargetOffset() + dex_offset);
DCHECK(target != nullptr);
current_block_->AddInstruction(new (arena_) HGoto());
current_block_->AddSuccessor(target);
current_block_ = nullptr;
break;
}
case Instruction::NOP:
break;
default:
return false;
}
return true;
}
} // namespace art
|
