dex_to_dex_compiler.cc revision 1ebe2173d9c6144da16fd6c8790d14bcc9b38fa0 
1/*
2 * Copyright (C) 2011 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 "base/logging.h"
18#include "base/mutex.h"
19#include "dex_file-inl.h"
20#include "dex_instruction-inl.h"
21#include "driver/compiler_driver.h"
22#include "driver/dex_compilation_unit.h"
23#include "mirror/art_field-inl.h"
24#include "mirror/art_method-inl.h"
25#include "mirror/class-inl.h"
26#include "mirror/dex_cache.h"
27#include "thread-inl.h"
28
29namespace art {
30namespace optimizer {
31
32// Controls quickening activation.
33const bool kEnableQuickening = true;
34// Control check-cast elision.
35const bool kEnableCheckCastEllision = true;
36
37class DexCompiler {
38 public:
39  DexCompiler(art::CompilerDriver& compiler,
40              const DexCompilationUnit& unit,
41              DexToDexCompilationLevel dex_to_dex_compilation_level)
42    : driver_(compiler),
43      unit_(unit),
44      dex_to_dex_compilation_level_(dex_to_dex_compilation_level) {}
45
46  ~DexCompiler() {}
47
48  void Compile();
49
50 private:
51  const DexFile& GetDexFile() const {
52    return *unit_.GetDexFile();
53  }
54
55  bool PerformOptimizations() const {
56    return dex_to_dex_compilation_level_ >= kOptimize;
57  }
58
59  // Compiles a RETURN-VOID into a RETURN-VOID-BARRIER within a constructor where
60  // a barrier is required.
61  void CompileReturnVoid(Instruction* inst, uint32_t dex_pc);
62
63  // Compiles a CHECK-CAST into 2 NOP instructions if it is known to be safe. In
64  // this case, returns the second NOP instruction pointer. Otherwise, returns
65  // the given "inst".
66  Instruction* CompileCheckCast(Instruction* inst, uint32_t dex_pc);
67
68  // Compiles a field access into a quick field access.
69  // The field index is replaced by an offset within an Object where we can read
70  // from / write to this field. Therefore, this does not involve any resolution
71  // at runtime.
72  // Since the field index is encoded with 16 bits, we can replace it only if the
73  // field offset can be encoded with 16 bits too.
74  void CompileInstanceFieldAccess(Instruction* inst, uint32_t dex_pc,
75                                  Instruction::Code new_opcode, bool is_put);
76
77  // Compiles a virtual method invocation into a quick virtual method invocation.
78  // The method index is replaced by the vtable index where the corresponding
79  // AbstractMethod can be found. Therefore, this does not involve any resolution
80  // at runtime.
81  // Since the method index is encoded with 16 bits, we can replace it only if the
82  // vtable index can be encoded with 16 bits too.
83  void CompileInvokeVirtual(Instruction* inst, uint32_t dex_pc,
84                            Instruction::Code new_opcode, bool is_range);
85
86  CompilerDriver& driver_;
87  const DexCompilationUnit& unit_;
88  const DexToDexCompilationLevel dex_to_dex_compilation_level_;
89
90  DISALLOW_COPY_AND_ASSIGN(DexCompiler);
91};
92
93void DexCompiler::Compile() {
94  DCHECK_GE(dex_to_dex_compilation_level_, kRequired);
95  const DexFile::CodeItem* code_item = unit_.GetCodeItem();
96  const uint16_t* insns = code_item->insns_;
97  const uint32_t insns_size = code_item->insns_size_in_code_units_;
98  Instruction* inst = const_cast<Instruction*>(Instruction::At(insns));
99
100  for (uint32_t dex_pc = 0; dex_pc < insns_size;
101       inst = const_cast<Instruction*>(inst->Next()), dex_pc = inst->GetDexPc(insns)) {
102    switch (inst->Opcode()) {
103      case Instruction::RETURN_VOID:
104        CompileReturnVoid(inst, dex_pc);
105        break;
106
107      case Instruction::CHECK_CAST:
108        inst = CompileCheckCast(inst, dex_pc);
109        break;
110
111      case Instruction::IGET:
112        CompileInstanceFieldAccess(inst, dex_pc, Instruction::IGET_QUICK, false);
113        break;
114
115      case Instruction::IGET_WIDE:
116        CompileInstanceFieldAccess(inst, dex_pc, Instruction::IGET_WIDE_QUICK, false);
117        break;
118
119      case Instruction::IGET_OBJECT:
120        CompileInstanceFieldAccess(inst, dex_pc, Instruction::IGET_OBJECT_QUICK, false);
121        break;
122
123      case Instruction::IPUT:
124      case Instruction::IPUT_BOOLEAN:
125      case Instruction::IPUT_BYTE:
126      case Instruction::IPUT_CHAR:
127      case Instruction::IPUT_SHORT:
128        // These opcodes have the same implementation in interpreter so group
129        // them under IPUT_QUICK.
130        CompileInstanceFieldAccess(inst, dex_pc, Instruction::IPUT_QUICK, true);
131        break;
132
133      case Instruction::IPUT_WIDE:
134        CompileInstanceFieldAccess(inst, dex_pc, Instruction::IPUT_WIDE_QUICK, true);
135        break;
136
137      case Instruction::IPUT_OBJECT:
138        CompileInstanceFieldAccess(inst, dex_pc, Instruction::IPUT_OBJECT_QUICK, true);
139        break;
140
141      case Instruction::INVOKE_VIRTUAL:
142        CompileInvokeVirtual(inst, dex_pc, Instruction::INVOKE_VIRTUAL_QUICK, false);
143        break;
144
145      case Instruction::INVOKE_VIRTUAL_RANGE:
146        CompileInvokeVirtual(inst, dex_pc, Instruction::INVOKE_VIRTUAL_RANGE_QUICK, true);
147        break;
148
149      default:
150        // Nothing to do.
151        break;
152    }
153  }
154}
155
156void DexCompiler::CompileReturnVoid(Instruction* inst, uint32_t dex_pc) {
157  DCHECK(inst->Opcode() == Instruction::RETURN_VOID);
158  // Are we compiling a non-clinit constructor?
159  if (!unit_.IsConstructor() || unit_.IsStatic()) {
160    return;
161  }
162  // Do we need a constructor barrier ?
163  if (!driver_.RequiresConstructorBarrier(Thread::Current(), unit_.GetDexFile(),
164                                         unit_.GetClassDefIndex())) {
165    return;
166  }
167  // Replace RETURN_VOID by RETURN_VOID_BARRIER.
168  VLOG(compiler) << "Replacing " << Instruction::Name(inst->Opcode())
169                 << " by " << Instruction::Name(Instruction::RETURN_VOID_BARRIER)
170                 << " at dex pc " << StringPrintf("0x%x", dex_pc) << " in method "
171                 << PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
172  inst->SetOpcode(Instruction::RETURN_VOID_BARRIER);
173}
174
175Instruction* DexCompiler::CompileCheckCast(Instruction* inst, uint32_t dex_pc) {
176  if (!kEnableCheckCastEllision || !PerformOptimizations()) {
177    return inst;
178  }
179  MethodReference referrer(&GetDexFile(), unit_.GetDexMethodIndex());
180  if (!driver_.IsSafeCast(referrer, dex_pc)) {
181    return inst;
182  }
183  // Ok, this is a safe cast. Since the "check-cast" instruction size is 2 code
184  // units and a "nop" instruction size is 1 code unit, we need to replace it by
185  // 2 consecutive NOP instructions.
186  // Because the caller loops over instructions by calling Instruction::Next onto
187  // the current instruction, we need to return the 2nd NOP instruction. Indeed,
188  // its next instruction is the former check-cast's next instruction.
189  VLOG(compiler) << "Removing " << Instruction::Name(inst->Opcode())
190                 << " by replacing it with 2 NOPs at dex pc "
191                 << StringPrintf("0x%x", dex_pc) << " in method "
192                 << PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
193  // We are modifying 4 consecutive bytes.
194  inst->SetOpcode(Instruction::NOP);
195  inst->SetVRegA_10x(0u);  // keep compliant with verifier.
196  // Get to next instruction which is the second half of check-cast and replace
197  // it by a NOP.
198  inst = const_cast<Instruction*>(inst->Next());
199  inst->SetOpcode(Instruction::NOP);
200  inst->SetVRegA_10x(0u);  // keep compliant with verifier.
201  return inst;
202}
203
204void DexCompiler::CompileInstanceFieldAccess(Instruction* inst,
205                                             uint32_t dex_pc,
206                                             Instruction::Code new_opcode,
207                                             bool is_put) {
208  if (!kEnableQuickening || !PerformOptimizations()) {
209    return;
210  }
211  uint32_t field_idx = inst->VRegC_22c();
212  int field_offset;
213  bool is_volatile;
214  bool fast_path = driver_.ComputeInstanceFieldInfo(field_idx, &unit_, is_put,
215                                                    &field_offset, &is_volatile);
216  if (fast_path && !is_volatile && IsUint(16, field_offset)) {
217    VLOG(compiler) << "Quickening " << Instruction::Name(inst->Opcode())
218                   << " to " << Instruction::Name(new_opcode)
219                   << " by replacing field index " << field_idx
220                   << " by field offset " << field_offset
221                   << " at dex pc " << StringPrintf("0x%x", dex_pc) << " in method "
222                   << PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
223    // We are modifying 4 consecutive bytes.
224    inst->SetOpcode(new_opcode);
225    // Replace field index by field offset.
226    inst->SetVRegC_22c(static_cast<uint16_t>(field_offset));
227  }
228}
229
230void DexCompiler::CompileInvokeVirtual(Instruction* inst,
231                                uint32_t dex_pc,
232                                Instruction::Code new_opcode,
233                                bool is_range) {
234  if (!kEnableQuickening || !PerformOptimizations()) {
235    return;
236  }
237  uint32_t method_idx = is_range ? inst->VRegB_3rc() : inst->VRegB_35c();
238  MethodReference target_method(&GetDexFile(), method_idx);
239  InvokeType invoke_type = kVirtual;
240  InvokeType original_invoke_type = invoke_type;
241  int vtable_idx;
242  uintptr_t direct_code;
243  uintptr_t direct_method;
244  // TODO: support devirtualization.
245  const bool kEnableDevirtualization = false;
246  bool fast_path = driver_.ComputeInvokeInfo(&unit_, dex_pc,
247                                             false, kEnableDevirtualization,
248                                             &invoke_type,
249                                             &target_method, &vtable_idx,
250                                             &direct_code, &direct_method);
251  if (fast_path && original_invoke_type == invoke_type) {
252    if (vtable_idx >= 0 && IsUint(16, vtable_idx)) {
253      VLOG(compiler) << "Quickening " << Instruction::Name(inst->Opcode())
254                     << "(" << PrettyMethod(method_idx, GetDexFile(), true) << ")"
255                     << " to " << Instruction::Name(new_opcode)
256                     << " by replacing method index " << method_idx
257                     << " by vtable index " << vtable_idx
258                     << " at dex pc " << StringPrintf("0x%x", dex_pc) << " in method "
259                     << PrettyMethod(unit_.GetDexMethodIndex(), GetDexFile(), true);
260      // We are modifying 4 consecutive bytes.
261      inst->SetOpcode(new_opcode);
262      // Replace method index by vtable index.
263      if (is_range) {
264        inst->SetVRegB_3rc(static_cast<uint16_t>(vtable_idx));
265      } else {
266        inst->SetVRegB_35c(static_cast<uint16_t>(vtable_idx));
267      }
268    }
269  }
270}
271
272}  // namespace optimizer
273}  // namespace art
274
275extern "C" void ArtCompileDEX(art::CompilerDriver& compiler, const art::DexFile::CodeItem* code_item,
276                  uint32_t access_flags, art::InvokeType invoke_type,
277                  uint16_t class_def_idx, uint32_t method_idx, jobject class_loader,
278                  const art::DexFile& dex_file,
279                  art::DexToDexCompilationLevel dex_to_dex_compilation_level) {
280  if (dex_to_dex_compilation_level != art::kDontDexToDexCompile) {
281    art::DexCompilationUnit unit(NULL, class_loader, art::Runtime::Current()->GetClassLinker(),
282                                 dex_file, code_item, class_def_idx, method_idx, access_flags);
283    art::optimizer::DexCompiler dex_compiler(compiler, unit, dex_to_dex_compilation_level);
284    dex_compiler.Compile();
285  }
286}
287