compiler/optimizing/builder.cc - platform/art - Gitiles

 /*
  *
  * 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_file.h"
 #include "dex_file-inl.h"
 #include "dex_instruction.h"
 #include "dex_instruction-inl.h"
 #include "builder.h"
 #include "nodes.h"
 #include "primitive.h"

 namespace art {

 void HGraphBuilder::InitializeLocals(uint16_t count) {
   graph_->SetNumberOfVRegs(count);
   locals_.SetSize(count);
   for (int i = 0; i < count; i++) {
     HLocal* local = new (arena_) HLocal(i);
     entry_block_->AddInstruction(local);
     locals_.Put(i, local);
   }
 }

 bool HGraphBuilder::InitializeParameters(uint16_t number_of_parameters) {
   // dex_compilation_unit_ is null only when unit testing.
   if (dex_compilation_unit_ == nullptr) {
     return true;
   }

   graph_->SetNumberOfInVRegs(number_of_parameters);
   const char* shorty = dex_compilation_unit_->GetShorty();
   int locals_index = locals_.Size() - number_of_parameters;
   int parameter_index = 0;

   if (!dex_compilation_unit_->IsStatic()) {
     // Add the implicit 'this' argument, not expressed in the signature.
     HParameterValue* parameter =
         new (arena_) HParameterValue(parameter_index++, Primitive::kPrimNot);
     entry_block_->AddInstruction(parameter);
     HLocal* local = GetLocalAt(locals_index++);
     entry_block_->AddInstruction(new (arena_) HStoreLocal(local, parameter));
     number_of_parameters--;
   }

   uint32_t pos = 1;
   for (int i = 0; i < number_of_parameters; i++) {
     switch (shorty[pos++]) {
       case 'F':
       case 'D': {
         return false;
       }

       default: {
         // integer and reference parameters.
         HParameterValue* parameter =
             new (arena_) HParameterValue(parameter_index++, Primitive::GetType(shorty[pos - 1]));
         entry_block_->AddInstruction(parameter);
         HLocal* local = GetLocalAt(locals_index++);
         // Store the parameter value in the local that the dex code will use
         // to reference that parameter.
         entry_block_->AddInstruction(new (arena_) HStoreLocal(local, parameter));
         if (parameter->GetType() == Primitive::kPrimLong) {
           i++;
           locals_index++;
           parameter_index++;
         }
         break;
       }
     }
   }
   return true;
 }

 static bool CanHandleCodeItem(const DexFile::CodeItem& code_item) {
   if (code_item.tries_size_ > 0) {
     return false;
   }
   return true;
 }

 template<typename T>
 void HGraphBuilder::If_22t(const Instruction& instruction, int32_t dex_offset, bool is_not) {
   HInstruction* first = LoadLocal(instruction.VRegA(), Primitive::kPrimInt);
   HInstruction* second = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
   current_block_->AddInstruction(new (arena_) T(first, second));
   if (is_not) {
     current_block_->AddInstruction(new (arena_) HNot(current_block_->GetLastInstruction()));
   }
   current_block_->AddInstruction(new (arena_) HIf(current_block_->GetLastInstruction()));
   HBasicBlock* target = FindBlockStartingAt(instruction.GetTargetOffset() + dex_offset);
   DCHECK(target != nullptr);
   current_block_->AddSuccessor(target);
   target = FindBlockStartingAt(dex_offset + instruction.SizeInCodeUnits());
   DCHECK(target != nullptr);
   current_block_->AddSuccessor(target);
   current_block_ = nullptr;
 }

 HGraph* HGraphBuilder::BuildGraph(const DexFile::CodeItem& code_item) {
   if (!CanHandleCodeItem(code_item)) {
     return nullptr;
   }

   const uint16_t* code_ptr = code_item.insns_;
   const uint16_t* code_end = code_item.insns_ + code_item.insns_size_in_code_units_;

   // 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_);
   exit_block_ = new (arena_) HBasicBlock(graph_);
   graph_->SetEntryBlock(entry_block_);
   graph_->SetExitBlock(exit_block_);

   InitializeLocals(code_item.registers_size_);
   graph_->UpdateMaximumNumberOfOutVRegs(code_item.outs_size_);

   // 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);

   if (!InitializeParameters(code_item.ins_size_)) {
     return nullptr;
   }

   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_);
   exit_block_->AddInstruction(new (arena_) HExit());
   entry_block_->AddInstruction(new (arena_) HGoto());
   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);
 }

 template<typename T>
 void HGraphBuilder::Binop_32x(const Instruction& instruction, Primitive::Type type) {
   HInstruction* first = LoadLocal(instruction.VRegB(), type);
   HInstruction* second = LoadLocal(instruction.VRegC(), type);
   current_block_->AddInstruction(new (arena_) T(type, first, second));
   UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
 }

 template<typename T>
 void HGraphBuilder::Binop_12x(const Instruction& instruction, Primitive::Type type) {
   HInstruction* first = LoadLocal(instruction.VRegA(), type);
   HInstruction* second = LoadLocal(instruction.VRegB(), type);
   current_block_->AddInstruction(new (arena_) T(type, first, second));
   UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
 }

 template<typename T>
 void HGraphBuilder::Binop_22s(const Instruction& instruction, bool reverse) {
   HInstruction* first = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
   HInstruction* second = GetIntConstant(instruction.VRegC_22s());
   if (reverse) {
     std::swap(first, second);
   }
   current_block_->AddInstruction(new (arena_) T(Primitive::kPrimInt, first, second));
   UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
 }

 template<typename T>
 void HGraphBuilder::Binop_22b(const Instruction& instruction, bool reverse) {
   HInstruction* first = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
   HInstruction* second = GetIntConstant(instruction.VRegC_22b());
   if (reverse) {
     std::swap(first, second);
   }
   current_block_->AddInstruction(new (arena_) T(Primitive::kPrimInt, first, second));
   UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
 }

 void HGraphBuilder::BuildReturn(const Instruction& instruction, Primitive::Type type) {
   if (type == Primitive::kPrimVoid) {
     current_block_->AddInstruction(new (arena_) HReturnVoid());
   } else {
     HInstruction* value = LoadLocal(instruction.VRegA(), type);
     current_block_->AddInstruction(new (arena_) HReturn(value));
   }
   current_block_->AddSuccessor(exit_block_);
   current_block_ = nullptr;
 }

 bool HGraphBuilder::BuildInvoke(const Instruction& instruction,
                                 uint32_t dex_offset,
                                 uint32_t method_idx,
                                 uint32_t number_of_vreg_arguments,
                                 bool is_range,
                                 uint32_t* args,
                                 uint32_t register_index) {
   const DexFile::MethodId& method_id = dex_file_->GetMethodId(method_idx);
   const DexFile::ProtoId& proto_id = dex_file_->GetProtoId(method_id.proto_idx_);
   const char* descriptor = dex_file_->StringDataByIdx(proto_id.shorty_idx_);
   Primitive::Type return_type = Primitive::GetType(descriptor[0]);
   bool is_instance_call =
       instruction.Opcode() != Instruction::INVOKE_STATIC
       && instruction.Opcode() != Instruction::INVOKE_STATIC_RANGE;
   const size_t number_of_arguments = strlen(descriptor) - (is_instance_call ? 0 : 1);

   // Treat invoke-direct like static calls for now.
   HInvoke* invoke = new (arena_) HInvokeStatic(
       arena_, number_of_arguments, return_type, dex_offset, method_idx);

   size_t start_index = 0;
   if (is_instance_call) {
     HInstruction* arg = LoadLocal(is_range ? register_index : args[0], Primitive::kPrimNot);
     invoke->SetArgumentAt(0, arg);
     start_index = 1;
   }

   uint32_t descriptor_index = 1;
   uint32_t argument_index = start_index;
   for (size_t i = start_index; i < number_of_vreg_arguments; i++, argument_index++) {
     Primitive::Type type = Primitive::GetType(descriptor[descriptor_index++]);
     switch (type) {
       case Primitive::kPrimFloat:
       case Primitive::kPrimDouble:
         return false;

       default: {
         if (!is_range && type == Primitive::kPrimLong && args[i] + 1 != args[i + 1]) {
           LOG(WARNING) << "Non sequential register pair in " << dex_compilation_unit_->GetSymbol()
                        << " at " << dex_offset;
           // We do not implement non sequential register pair.
           return false;
         }
         HInstruction* arg = LoadLocal(is_range ? register_index + i : args[i], type);
         invoke->SetArgumentAt(argument_index, arg);
         if (type == Primitive::kPrimLong) {
           i++;
         }
       }
     }
   }

   DCHECK_EQ(argument_index, number_of_arguments);
   current_block_->AddInstruction(invoke);
   return true;
 }

 bool HGraphBuilder::AnalyzeDexInstruction(const Instruction& instruction, int32_t dex_offset) {
   if (current_block_ == nullptr) {
     return true;  // Dead code
   }

   switch (instruction.Opcode()) {
     case Instruction::CONST_4: {
       int32_t register_index = instruction.VRegA();
       HIntConstant* constant = GetIntConstant(instruction.VRegB_11n());
       UpdateLocal(register_index, constant);
       break;
     }

     case Instruction::CONST_16: {
       int32_t register_index = instruction.VRegA();
       HIntConstant* constant = GetIntConstant(instruction.VRegB_21s());
       UpdateLocal(register_index, constant);
       break;
     }

     case Instruction::CONST_WIDE_16: {
       int32_t register_index = instruction.VRegA();
       HLongConstant* constant = GetLongConstant(instruction.VRegB_21s());
       UpdateLocal(register_index, constant);
       break;
     }

     case Instruction::CONST_WIDE_32: {
       int32_t register_index = instruction.VRegA();
       HLongConstant* constant = GetLongConstant(instruction.VRegB_31i());
       UpdateLocal(register_index, constant);
       break;
     }

     case Instruction::CONST_WIDE: {
       int32_t register_index = instruction.VRegA();
       HLongConstant* constant = GetLongConstant(instruction.VRegB_51l());
       UpdateLocal(register_index, constant);
       break;
     }

     case Instruction::MOVE: {
       HInstruction* value = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
       UpdateLocal(instruction.VRegA(), value);
       break;
     }

     case Instruction::RETURN_VOID: {
       BuildReturn(instruction, Primitive::kPrimVoid);
       break;
     }

     case Instruction::IF_EQ: {
       If_22t<HEqual>(instruction, dex_offset, false);
       break;
     }

     case Instruction::IF_NE: {
       If_22t<HEqual>(instruction, dex_offset, true);
       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::RETURN: {
       BuildReturn(instruction, Primitive::kPrimInt);
       break;
     }

     case Instruction::RETURN_OBJECT: {
       BuildReturn(instruction, Primitive::kPrimNot);
       break;
     }

     case Instruction::RETURN_WIDE: {
       BuildReturn(instruction, Primitive::kPrimLong);
       break;
     }

     case Instruction::INVOKE_STATIC:
     case Instruction::INVOKE_DIRECT: {
       uint32_t method_idx = instruction.VRegB_35c();
       uint32_t number_of_vreg_arguments = instruction.VRegA_35c();
       uint32_t args[5];
       instruction.GetArgs(args);
       if (!BuildInvoke(instruction, dex_offset, method_idx, number_of_vreg_arguments, false, args, -1)) {
         return false;
       }
       break;
     }

     case Instruction::INVOKE_STATIC_RANGE:
     case Instruction::INVOKE_DIRECT_RANGE: {
       uint32_t method_idx = instruction.VRegB_3rc();
       uint32_t number_of_vreg_arguments = instruction.VRegA_3rc();
       uint32_t register_index = instruction.VRegC();
       if (!BuildInvoke(instruction, dex_offset, method_idx,
                        number_of_vreg_arguments, true, nullptr, register_index)) {
         return false;
       }
       break;
     }

     case Instruction::ADD_INT: {
       Binop_32x<HAdd>(instruction, Primitive::kPrimInt);
       break;
     }

     case Instruction::ADD_LONG: {
       Binop_32x<HAdd>(instruction, Primitive::kPrimLong);
       break;
     }

     case Instruction::SUB_INT: {
       Binop_32x<HSub>(instruction, Primitive::kPrimInt);
       break;
     }

     case Instruction::SUB_LONG: {
       Binop_32x<HSub>(instruction, Primitive::kPrimLong);
       break;
     }

     case Instruction::ADD_INT_2ADDR: {
       Binop_12x<HAdd>(instruction, Primitive::kPrimInt);
       break;
     }

     case Instruction::ADD_LONG_2ADDR: {
       Binop_12x<HAdd>(instruction, Primitive::kPrimLong);
       break;
     }

     case Instruction::SUB_INT_2ADDR: {
       Binop_12x<HSub>(instruction, Primitive::kPrimInt);
       break;
     }

     case Instruction::SUB_LONG_2ADDR: {
       Binop_12x<HSub>(instruction, Primitive::kPrimLong);
       break;
     }

     case Instruction::ADD_INT_LIT16: {
       Binop_22s<HAdd>(instruction, false);
       break;
     }

     case Instruction::RSUB_INT: {
       Binop_22s<HSub>(instruction, true);
       break;
     }

     case Instruction::ADD_INT_LIT8: {
       Binop_22b<HAdd>(instruction, false);
       break;
     }

     case Instruction::RSUB_INT_LIT8: {
       Binop_22b<HSub>(instruction, true);
       break;
     }

     case Instruction::NEW_INSTANCE: {
       current_block_->AddInstruction(
           new (arena_) HNewInstance(dex_offset, instruction.VRegB_21c()));
       UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
       break;
     }

     case Instruction::MOVE_RESULT_WIDE: {
       UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
       break;
     }

     case Instruction::NOP:
       break;

     default:
       return false;
   }
   return true;
 }

 HIntConstant* HGraphBuilder::GetIntConstant0() {
   if (constant0_ != nullptr) {
     return constant0_;
   }
   constant0_ = new(arena_) HIntConstant(0);
   entry_block_->AddInstruction(constant0_);
   return constant0_;
 }

 HIntConstant* HGraphBuilder::GetIntConstant1() {
   if (constant1_ != nullptr) {
     return constant1_;
   }
   constant1_ = new(arena_) HIntConstant(1);
   entry_block_->AddInstruction(constant1_);
   return constant1_;
 }

 HIntConstant* HGraphBuilder::GetIntConstant(int32_t constant) {
   switch (constant) {
     case 0: return GetIntConstant0();
     case 1: return GetIntConstant1();
     default: {
       HIntConstant* instruction = new (arena_) HIntConstant(constant);
       entry_block_->AddInstruction(instruction);
       return instruction;
     }
   }
 }

 HLongConstant* HGraphBuilder::GetLongConstant(int64_t constant) {
   HLongConstant* instruction = new (arena_) HLongConstant(constant);
   entry_block_->AddInstruction(instruction);
   return instruction;
 }

 HLocal* HGraphBuilder::GetLocalAt(int register_index) const {
   return locals_.Get(register_index);
 }

 void HGraphBuilder::UpdateLocal(int register_index, HInstruction* instruction) const {
   HLocal* local = GetLocalAt(register_index);
   current_block_->AddInstruction(new (arena_) HStoreLocal(local, instruction));
 }

 HInstruction* HGraphBuilder::LoadLocal(int register_index, Primitive::Type type) const {
   HLocal* local = GetLocalAt(register_index);
   current_block_->AddInstruction(new (arena_) HLoadLocal(local, type));
   return current_block_->GetLastInstruction();
 }

 }  // namespace art
	/*
	*
	* 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_file.h"
	#include "dex_file-inl.h"
	#include "dex_instruction.h"
	#include "dex_instruction-inl.h"
	#include "builder.h"
	#include "nodes.h"
	#include "primitive.h"

	namespace art {

	void HGraphBuilder::InitializeLocals(uint16_t count) {
	graph_->SetNumberOfVRegs(count);
	locals_.SetSize(count);
	for (int i = 0; i < count; i++) {
	HLocal* local = new (arena_) HLocal(i);
	entry_block_->AddInstruction(local);
	locals_.Put(i, local);
	}
	}

	bool HGraphBuilder::InitializeParameters(uint16_t number_of_parameters) {
	// dex_compilation_unit_ is null only when unit testing.
	if (dex_compilation_unit_ == nullptr) {
	return true;
	}

	graph_->SetNumberOfInVRegs(number_of_parameters);
	const char* shorty = dex_compilation_unit_->GetShorty();
	int locals_index = locals_.Size() - number_of_parameters;
	int parameter_index = 0;

	if (!dex_compilation_unit_->IsStatic()) {
	// Add the implicit 'this' argument, not expressed in the signature.
	HParameterValue* parameter =
	new (arena_) HParameterValue(parameter_index++, Primitive::kPrimNot);
	entry_block_->AddInstruction(parameter);
	HLocal* local = GetLocalAt(locals_index++);
	entry_block_->AddInstruction(new (arena_) HStoreLocal(local, parameter));
	number_of_parameters--;
	}

	uint32_t pos = 1;
	for (int i = 0; i < number_of_parameters; i++) {
	switch (shorty[pos++]) {
	case 'F':
	case 'D': {
	return false;
	}

	default: {
	// integer and reference parameters.
	HParameterValue* parameter =
	new (arena_) HParameterValue(parameter_index++, Primitive::GetType(shorty[pos - 1]));
	entry_block_->AddInstruction(parameter);
	HLocal* local = GetLocalAt(locals_index++);
	// Store the parameter value in the local that the dex code will use
	// to reference that parameter.
	entry_block_->AddInstruction(new (arena_) HStoreLocal(local, parameter));
	if (parameter->GetType() == Primitive::kPrimLong) {
	i++;
	locals_index++;
	parameter_index++;
	}
	break;
	}
	}
	}
	return true;
	}

	static bool CanHandleCodeItem(const DexFile::CodeItem& code_item) {
	if (code_item.tries_size_ > 0) {
	return false;
	}
	return true;
	}

	template<typename T>
	void HGraphBuilder::If_22t(const Instruction& instruction, int32_t dex_offset, bool is_not) {
	HInstruction* first = LoadLocal(instruction.VRegA(), Primitive::kPrimInt);
	HInstruction* second = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
	current_block_->AddInstruction(new (arena_) T(first, second));
	if (is_not) {
	current_block_->AddInstruction(new (arena_) HNot(current_block_->GetLastInstruction()));
	}
	current_block_->AddInstruction(new (arena_) HIf(current_block_->GetLastInstruction()));
	HBasicBlock* target = FindBlockStartingAt(instruction.GetTargetOffset() + dex_offset);
	DCHECK(target != nullptr);
	current_block_->AddSuccessor(target);
	target = FindBlockStartingAt(dex_offset + instruction.SizeInCodeUnits());
	DCHECK(target != nullptr);
	current_block_->AddSuccessor(target);
	current_block_ = nullptr;
	}

	HGraph* HGraphBuilder::BuildGraph(const DexFile::CodeItem& code_item) {
	if (!CanHandleCodeItem(code_item)) {
	return nullptr;
	}

	const uint16_t* code_ptr = code_item.insns_;
	const uint16_t* code_end = code_item.insns_ + code_item.insns_size_in_code_units_;

	// 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_);
	exit_block_ = new (arena_) HBasicBlock(graph_);
	graph_->SetEntryBlock(entry_block_);
	graph_->SetExitBlock(exit_block_);

	InitializeLocals(code_item.registers_size_);
	graph_->UpdateMaximumNumberOfOutVRegs(code_item.outs_size_);

	// 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);

	if (!InitializeParameters(code_item.ins_size_)) {
	return nullptr;
	}

	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_);
	exit_block_->AddInstruction(new (arena_) HExit());
	entry_block_->AddInstruction(new (arena_) HGoto());
	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);
	}

	template<typename T>
	void HGraphBuilder::Binop_32x(const Instruction& instruction, Primitive::Type type) {
	HInstruction* first = LoadLocal(instruction.VRegB(), type);
	HInstruction* second = LoadLocal(instruction.VRegC(), type);
	current_block_->AddInstruction(new (arena_) T(type, first, second));
	UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
	}

	template<typename T>
	void HGraphBuilder::Binop_12x(const Instruction& instruction, Primitive::Type type) {
	HInstruction* first = LoadLocal(instruction.VRegA(), type);
	HInstruction* second = LoadLocal(instruction.VRegB(), type);
	current_block_->AddInstruction(new (arena_) T(type, first, second));
	UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
	}

	template<typename T>
	void HGraphBuilder::Binop_22s(const Instruction& instruction, bool reverse) {
	HInstruction* first = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
	HInstruction* second = GetIntConstant(instruction.VRegC_22s());
	if (reverse) {
	std::swap(first, second);
	}
	current_block_->AddInstruction(new (arena_) T(Primitive::kPrimInt, first, second));
	UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
	}

	template<typename T>
	void HGraphBuilder::Binop_22b(const Instruction& instruction, bool reverse) {
	HInstruction* first = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
	HInstruction* second = GetIntConstant(instruction.VRegC_22b());
	if (reverse) {
	std::swap(first, second);
	}
	current_block_->AddInstruction(new (arena_) T(Primitive::kPrimInt, first, second));
	UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
	}

	void HGraphBuilder::BuildReturn(const Instruction& instruction, Primitive::Type type) {
	if (type == Primitive::kPrimVoid) {
	current_block_->AddInstruction(new (arena_) HReturnVoid());
	} else {
	HInstruction* value = LoadLocal(instruction.VRegA(), type);
	current_block_->AddInstruction(new (arena_) HReturn(value));
	}
	current_block_->AddSuccessor(exit_block_);
	current_block_ = nullptr;
	}

	bool HGraphBuilder::BuildInvoke(const Instruction& instruction,
	uint32_t dex_offset,
	uint32_t method_idx,
	uint32_t number_of_vreg_arguments,
	bool is_range,
	uint32_t* args,
	uint32_t register_index) {
	const DexFile::MethodId& method_id = dex_file_->GetMethodId(method_idx);
	const DexFile::ProtoId& proto_id = dex_file_->GetProtoId(method_id.proto_idx_);
	const char* descriptor = dex_file_->StringDataByIdx(proto_id.shorty_idx_);
	Primitive::Type return_type = Primitive::GetType(descriptor[0]);
	bool is_instance_call =
	instruction.Opcode() != Instruction::INVOKE_STATIC
	&& instruction.Opcode() != Instruction::INVOKE_STATIC_RANGE;
	const size_t number_of_arguments = strlen(descriptor) - (is_instance_call ? 0 : 1);

	// Treat invoke-direct like static calls for now.
	HInvoke* invoke = new (arena_) HInvokeStatic(
	arena_, number_of_arguments, return_type, dex_offset, method_idx);

	size_t start_index = 0;
	if (is_instance_call) {
	HInstruction* arg = LoadLocal(is_range ? register_index : args[0], Primitive::kPrimNot);
	invoke->SetArgumentAt(0, arg);
	start_index = 1;
	}

	uint32_t descriptor_index = 1;
	uint32_t argument_index = start_index;
	for (size_t i = start_index; i < number_of_vreg_arguments; i++, argument_index++) {
	Primitive::Type type = Primitive::GetType(descriptor[descriptor_index++]);
	switch (type) {
	case Primitive::kPrimFloat:
	case Primitive::kPrimDouble:
	return false;

	default: {
	if (!is_range && type == Primitive::kPrimLong && args[i] + 1 != args[i + 1]) {
	LOG(WARNING) << "Non sequential register pair in " << dex_compilation_unit_->GetSymbol()
	<< " at " << dex_offset;
	// We do not implement non sequential register pair.
	return false;
	}
	HInstruction* arg = LoadLocal(is_range ? register_index + i : args[i], type);
	invoke->SetArgumentAt(argument_index, arg);
	if (type == Primitive::kPrimLong) {
	i++;
	}
	}
	}
	}

	DCHECK_EQ(argument_index, number_of_arguments);
	current_block_->AddInstruction(invoke);
	return true;
	}

	bool HGraphBuilder::AnalyzeDexInstruction(const Instruction& instruction, int32_t dex_offset) {
	if (current_block_ == nullptr) {
	return true; // Dead code
	}

	switch (instruction.Opcode()) {
	case Instruction::CONST_4: {
	int32_t register_index = instruction.VRegA();
	HIntConstant* constant = GetIntConstant(instruction.VRegB_11n());
	UpdateLocal(register_index, constant);
	break;
	}

	case Instruction::CONST_16: {
	int32_t register_index = instruction.VRegA();
	HIntConstant* constant = GetIntConstant(instruction.VRegB_21s());
	UpdateLocal(register_index, constant);
	break;
	}

	case Instruction::CONST_WIDE_16: {
	int32_t register_index = instruction.VRegA();
	HLongConstant* constant = GetLongConstant(instruction.VRegB_21s());
	UpdateLocal(register_index, constant);
	break;
	}

	case Instruction::CONST_WIDE_32: {
	int32_t register_index = instruction.VRegA();
	HLongConstant* constant = GetLongConstant(instruction.VRegB_31i());
	UpdateLocal(register_index, constant);
	break;
	}

	case Instruction::CONST_WIDE: {
	int32_t register_index = instruction.VRegA();
	HLongConstant* constant = GetLongConstant(instruction.VRegB_51l());
	UpdateLocal(register_index, constant);
	break;
	}

	case Instruction::MOVE: {
	HInstruction* value = LoadLocal(instruction.VRegB(), Primitive::kPrimInt);
	UpdateLocal(instruction.VRegA(), value);
	break;
	}

	case Instruction::RETURN_VOID: {
	BuildReturn(instruction, Primitive::kPrimVoid);
	break;
	}

	case Instruction::IF_EQ: {
	If_22t<HEqual>(instruction, dex_offset, false);
	break;
	}

	case Instruction::IF_NE: {
	If_22t<HEqual>(instruction, dex_offset, true);
	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::RETURN: {
	BuildReturn(instruction, Primitive::kPrimInt);
	break;
	}

	case Instruction::RETURN_OBJECT: {
	BuildReturn(instruction, Primitive::kPrimNot);
	break;
	}

	case Instruction::RETURN_WIDE: {
	BuildReturn(instruction, Primitive::kPrimLong);
	break;
	}

	case Instruction::INVOKE_STATIC:
	case Instruction::INVOKE_DIRECT: {
	uint32_t method_idx = instruction.VRegB_35c();
	uint32_t number_of_vreg_arguments = instruction.VRegA_35c();
	uint32_t args[5];
	instruction.GetArgs(args);
	if (!BuildInvoke(instruction, dex_offset, method_idx, number_of_vreg_arguments, false, args, -1)) {
	return false;
	}
	break;
	}

	case Instruction::INVOKE_STATIC_RANGE:
	case Instruction::INVOKE_DIRECT_RANGE: {
	uint32_t method_idx = instruction.VRegB_3rc();
	uint32_t number_of_vreg_arguments = instruction.VRegA_3rc();
	uint32_t register_index = instruction.VRegC();
	if (!BuildInvoke(instruction, dex_offset, method_idx,
	number_of_vreg_arguments, true, nullptr, register_index)) {
	return false;
	}
	break;
	}

	case Instruction::ADD_INT: {
	Binop_32x<HAdd>(instruction, Primitive::kPrimInt);
	break;
	}

	case Instruction::ADD_LONG: {
	Binop_32x<HAdd>(instruction, Primitive::kPrimLong);
	break;
	}

	case Instruction::SUB_INT: {
	Binop_32x<HSub>(instruction, Primitive::kPrimInt);
	break;
	}

	case Instruction::SUB_LONG: {
	Binop_32x<HSub>(instruction, Primitive::kPrimLong);
	break;
	}

	case Instruction::ADD_INT_2ADDR: {
	Binop_12x<HAdd>(instruction, Primitive::kPrimInt);
	break;
	}

	case Instruction::ADD_LONG_2ADDR: {
	Binop_12x<HAdd>(instruction, Primitive::kPrimLong);
	break;
	}

	case Instruction::SUB_INT_2ADDR: {
	Binop_12x<HSub>(instruction, Primitive::kPrimInt);
	break;
	}

	case Instruction::SUB_LONG_2ADDR: {
	Binop_12x<HSub>(instruction, Primitive::kPrimLong);
	break;
	}

	case Instruction::ADD_INT_LIT16: {
	Binop_22s<HAdd>(instruction, false);
	break;
	}

	case Instruction::RSUB_INT: {
	Binop_22s<HSub>(instruction, true);
	break;
	}

	case Instruction::ADD_INT_LIT8: {
	Binop_22b<HAdd>(instruction, false);
	break;
	}

	case Instruction::RSUB_INT_LIT8: {
	Binop_22b<HSub>(instruction, true);
	break;
	}

	case Instruction::NEW_INSTANCE: {
	current_block_->AddInstruction(
	new (arena_) HNewInstance(dex_offset, instruction.VRegB_21c()));
	UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
	break;
	}

	case Instruction::MOVE_RESULT_WIDE: {
	UpdateLocal(instruction.VRegA(), current_block_->GetLastInstruction());
	break;
	}

	case Instruction::NOP:
	break;

	default:
	return false;
	}
	return true;
	}

	HIntConstant* HGraphBuilder::GetIntConstant0() {
	if (constant0_ != nullptr) {
	return constant0_;
	}
	constant0_ = new(arena_) HIntConstant(0);
	entry_block_->AddInstruction(constant0_);
	return constant0_;
	}

	HIntConstant* HGraphBuilder::GetIntConstant1() {
	if (constant1_ != nullptr) {
	return constant1_;
	}
	constant1_ = new(arena_) HIntConstant(1);
	entry_block_->AddInstruction(constant1_);
	return constant1_;
	}

	HIntConstant* HGraphBuilder::GetIntConstant(int32_t constant) {
	switch (constant) {
	case 0: return GetIntConstant0();
	case 1: return GetIntConstant1();
	default: {
	HIntConstant* instruction = new (arena_) HIntConstant(constant);
	entry_block_->AddInstruction(instruction);
	return instruction;
	}
	}
	}

	HLongConstant* HGraphBuilder::GetLongConstant(int64_t constant) {
	HLongConstant* instruction = new (arena_) HLongConstant(constant);
	entry_block_->AddInstruction(instruction);
	return instruction;
	}

	HLocal* HGraphBuilder::GetLocalAt(int register_index) const {
	return locals_.Get(register_index);
	}

	void HGraphBuilder::UpdateLocal(int register_index, HInstruction* instruction) const {
	HLocal* local = GetLocalAt(register_index);
	current_block_->AddInstruction(new (arena_) HStoreLocal(local, instruction));
	}

	HInstruction* HGraphBuilder::LoadLocal(int register_index, Primitive::Type type) const {
	HLocal* local = GetLocalAt(register_index);
	current_block_->AddInstruction(new (arena_) HLoadLocal(local, type));
	return current_block_->GetLastInstruction();
	}

	} // namespace art