compiler/optimizing/nodes.h

/*
 * 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.
 */

#ifndef ART_COMPILER_OPTIMIZING_NODES_H_
#define ART_COMPILER_OPTIMIZING_NODES_H_

#include "base/arena_containers.h"
#include "base/arena_object.h"
#include "dex/compiler_enums.h"
#include "entrypoints/quick/quick_entrypoints_enum.h"
#include "handle.h"
#include "handle_scope.h"
#include "invoke_type.h"
#include "locations.h"
#include "mirror/class.h"
#include "offsets.h"
#include "primitive.h"
#include "utils/arena_bit_vector.h"
#include "utils/growable_array.h"

namespace art {

class GraphChecker;
class HBasicBlock;
class HCurrentMethod;
class HDoubleConstant;
class HEnvironment;
class HFloatConstant;
class HGraphBuilder;
class HGraphVisitor;
class HInstruction;
class HIntConstant;
class HInvoke;
class HLongConstant;
class HNullConstant;
class HPhi;
class HSuspendCheck;
class LiveInterval;
class LocationSummary;
class SlowPathCode;
class SsaBuilder;

static const int kDefaultNumberOfBlocks = 8;
static const int kDefaultNumberOfSuccessors = 2;
static const int kDefaultNumberOfPredecessors = 2;
static const int kDefaultNumberOfDominatedBlocks = 1;
static const int kDefaultNumberOfBackEdges = 1;

static constexpr uint32_t kMaxIntShiftValue = 0x1f;
static constexpr uint64_t kMaxLongShiftValue = 0x3f;

static constexpr uint32_t kUnknownFieldIndex = static_cast<uint32_t>(-1);

static constexpr InvokeType kInvalidInvokeType = static_cast<InvokeType>(-1);

enum IfCondition {
  kCondEQ,
  kCondNE,
  kCondLT,
  kCondLE,
  kCondGT,
  kCondGE,
};

class HInstructionList {
 public:
  HInstructionList() : first_instruction_(nullptr), last_instruction_(nullptr) {}

  void AddInstruction(HInstruction* instruction);
  void RemoveInstruction(HInstruction* instruction);

  // Insert `instruction` before/after an existing instruction `cursor`.
  void InsertInstructionBefore(HInstruction* instruction, HInstruction* cursor);
  void InsertInstructionAfter(HInstruction* instruction, HInstruction* cursor);

  // Return true if this list contains `instruction`.
  bool Contains(HInstruction* instruction) const;

  // Return true if `instruction1` is found before `instruction2` in
  // this instruction list and false otherwise.  Abort if none
  // of these instructions is found.
  bool FoundBefore(const HInstruction* instruction1,
                   const HInstruction* instruction2) const;

  bool IsEmpty() const { return first_instruction_ == nullptr; }
  void Clear() { first_instruction_ = last_instruction_ = nullptr; }

  // Update the block of all instructions to be `block`.
  void SetBlockOfInstructions(HBasicBlock* block) const;

  void AddAfter(HInstruction* cursor, const HInstructionList& instruction_list);
  void Add(const HInstructionList& instruction_list);

  // Return the number of instructions in the list. This is an expensive operation.
  size_t CountSize() const;

 private:
  HInstruction* first_instruction_;
  HInstruction* last_instruction_;

  friend class HBasicBlock;
  friend class HGraph;
  friend class HInstruction;
  friend class HInstructionIterator;
  friend class HBackwardInstructionIterator;

  DISALLOW_COPY_AND_ASSIGN(HInstructionList);
};

// Control-flow graph of a method. Contains a list of basic blocks.
class HGraph : public ArenaObject<kArenaAllocMisc> {
 public:
  HGraph(ArenaAllocator* arena,
         const DexFile& dex_file,
         uint32_t method_idx,
         bool should_generate_constructor_barrier,
         InstructionSet instruction_set,
         InvokeType invoke_type = kInvalidInvokeType,
         bool debuggable = false,
         int start_instruction_id = 0)
      : arena_(arena),
        blocks_(arena, kDefaultNumberOfBlocks),
        reverse_post_order_(arena, kDefaultNumberOfBlocks),
        linear_order_(arena, kDefaultNumberOfBlocks),
        entry_block_(nullptr),
        exit_block_(nullptr),
        maximum_number_of_out_vregs_(0),
        number_of_vregs_(0),
        number_of_in_vregs_(0),
        temporaries_vreg_slots_(0),
        has_bounds_checks_(false),
        debuggable_(debuggable),
        current_instruction_id_(start_instruction_id),
        dex_file_(dex_file),
        method_idx_(method_idx),
        invoke_type_(invoke_type),
        in_ssa_form_(false),
        should_generate_constructor_barrier_(should_generate_constructor_barrier),
        instruction_set_(instruction_set),
        cached_null_constant_(nullptr),
        cached_int_constants_(std::less<int32_t>(), arena->Adapter()),
        cached_float_constants_(std::less<int32_t>(), arena->Adapter()),
        cached_long_constants_(std::less<int64_t>(), arena->Adapter()),
        cached_double_constants_(std::less<int64_t>(), arena->Adapter()),
        cached_current_method_(nullptr) {}

  ArenaAllocator* GetArena() const { return arena_; }
  const GrowableArray<HBasicBlock*>& GetBlocks() const { return blocks_; }
  HBasicBlock* GetBlock(size_t id) const { return blocks_.Get(id); }

  bool IsInSsaForm() const { return in_ssa_form_; }

  HBasicBlock* GetEntryBlock() const { return entry_block_; }
  HBasicBlock* GetExitBlock() const { return exit_block_; }
  bool HasExitBlock() const { return exit_block_ != nullptr; }

  void SetEntryBlock(HBasicBlock* block) { entry_block_ = block; }
  void SetExitBlock(HBasicBlock* block) { exit_block_ = block; }

  void AddBlock(HBasicBlock* block);

  // Try building the SSA form of this graph, with dominance computation and loop
  // recognition. Returns whether it was successful in doing all these steps.
  bool TryBuildingSsa() {
    BuildDominatorTree();
    // The SSA builder requires loops to all be natural. Specifically, the dead phi
    // elimination phase checks the consistency of the graph when doing a post-order
    // visit for eliminating dead phis: a dead phi can only have loop header phi
    // users remaining when being visited.
    if (!AnalyzeNaturalLoops()) return false;
    TransformToSsa();
    in_ssa_form_ = true;
    return true;
  }

  void ComputeDominanceInformation();
  void ClearDominanceInformation();

  void BuildDominatorTree();
  void TransformToSsa();
  void SimplifyCFG();

  // Analyze all natural loops in this graph. Returns false if one
  // loop is not natural, that is the header does not dominate the
  // back edge.
  bool AnalyzeNaturalLoops() const;

  // Inline this graph in `outer_graph`, replacing the given `invoke` instruction.
  void InlineInto(HGraph* outer_graph, HInvoke* invoke);

  // Need to add a couple of blocks to test if the loop body is entered and
  // put deoptimization instructions, etc.
  void TransformLoopHeaderForBCE(HBasicBlock* header);

  // Removes `block` from the graph.
  void DeleteDeadBlock(HBasicBlock* block);

  // Splits the edge between `block` and `successor` while preserving the
  // indices in the predecessor/successor lists. If there are multiple edges
  // between the blocks, the lowest indices are used.
  // Returns the new block which is empty and has the same dex pc as `successor`.
  HBasicBlock* SplitEdge(HBasicBlock* block, HBasicBlock* successor);

  void SplitCriticalEdge(HBasicBlock* block, HBasicBlock* successor);
  void SimplifyLoop(HBasicBlock* header);

  int32_t GetNextInstructionId() {
    DCHECK_NE(current_instruction_id_, INT32_MAX);
    return current_instruction_id_++;
  }

  int32_t GetCurrentInstructionId() const {
    return current_instruction_id_;
  }

  void SetCurrentInstructionId(int32_t id) {
    current_instruction_id_ = id;
  }

  uint16_t GetMaximumNumberOfOutVRegs() const {
    return maximum_number_of_out_vregs_;
  }

  void SetMaximumNumberOfOutVRegs(uint16_t new_value) {
    maximum_number_of_out_vregs_ = new_value;
  }

  void UpdateMaximumNumberOfOutVRegs(uint16_t other_value) {
    maximum_number_of_out_vregs_ = std::max(maximum_number_of_out_vregs_, other_value);
  }

  void UpdateTemporariesVRegSlots(size_t slots) {
    temporaries_vreg_slots_ = std::max(slots, temporaries_vreg_slots_);
  }

  size_t GetTemporariesVRegSlots() const {
    DCHECK(!in_ssa_form_);
    return temporaries_vreg_slots_;
  }

  void SetNumberOfVRegs(uint16_t number_of_vregs) {
    number_of_vregs_ = number_of_vregs;
  }

  uint16_t GetNumberOfVRegs() const {
    DCHECK(!in_ssa_form_);
    return number_of_vregs_;
  }

  void SetNumberOfInVRegs(uint16_t value) {
    number_of_in_vregs_ = value;
  }

  uint16_t GetNumberOfLocalVRegs() const {
    DCHECK(!in_ssa_form_);
    return number_of_vregs_ - number_of_in_vregs_;
  }

  const GrowableArray<HBasicBlock*>& GetReversePostOrder() const {
    return reverse_post_order_;
  }

  const GrowableArray<HBasicBlock*>& GetLinearOrder() const {
    return linear_order_;
  }

  bool HasBoundsChecks() const {
    return has_bounds_checks_;
  }

  void SetHasBoundsChecks(bool value) {
    has_bounds_checks_ = value;
  }

  bool ShouldGenerateConstructorBarrier() const {
    return should_generate_constructor_barrier_;
  }

  bool IsDebuggable() const { return debuggable_; }

  // Returns a constant of the given type and value. If it does not exist
  // already, it is created and inserted into the graph. This method is only for
  // integral types.
  HConstant* GetConstant(Primitive::Type type, int64_t value);
  HNullConstant* GetNullConstant();
  HIntConstant* GetIntConstant(int32_t value) {
    return CreateConstant(value, &cached_int_constants_);
  }
  HLongConstant* GetLongConstant(int64_t value) {
    return CreateConstant(value, &cached_long_constants_);
  }
  HFloatConstant* GetFloatConstant(float value) {
    return CreateConstant(bit_cast<int32_t, float>(value), &cached_float_constants_);
  }
  HDoubleConstant* GetDoubleConstant(double value) {
    return CreateConstant(bit_cast<int64_t, double>(value), &cached_double_constants_);
  }

  HCurrentMethod* GetCurrentMethod();

  HBasicBlock* FindCommonDominator(HBasicBlock* first, HBasicBlock* second) const;

  const DexFile& GetDexFile() const {
    return dex_file_;
  }

  uint32_t GetMethodIdx() const {
    return method_idx_;
  }

  InvokeType GetInvokeType() const {
    return invoke_type_;
  }

 private:
  void VisitBlockForDominatorTree(HBasicBlock* block,
                                  HBasicBlock* predecessor,
                                  GrowableArray<size_t>* visits);
  void FindBackEdges(ArenaBitVector* visited);
  void VisitBlockForBackEdges(HBasicBlock* block,
                              ArenaBitVector* visited,
                              ArenaBitVector* visiting);
  void RemoveInstructionsAsUsersFromDeadBlocks(const ArenaBitVector& visited) const;
  void RemoveDeadBlocks(const ArenaBitVector& visited);

  template <class InstructionType, typename ValueType>
  InstructionType* CreateConstant(ValueType value,
                                  ArenaSafeMap<ValueType, InstructionType*>* cache) {
    // Try to find an existing constant of the given value.
    InstructionType* constant = nullptr;
    auto cached_constant = cache->find(value);
    if (cached_constant != cache->end()) {
      constant = cached_constant->second;
    }

    // If not found or previously deleted, create and cache a new instruction.
    // Don't bother reviving a previously deleted instruction, for simplicity.
    if (constant == nullptr || constant->GetBlock() == nullptr) {
      constant = new (arena_) InstructionType(value);
      cache->Overwrite(value, constant);
      InsertConstant(constant);
    }
    return constant;
  }

  void InsertConstant(HConstant* instruction);

  // Cache a float constant into the graph. This method should only be
  // called by the SsaBuilder when creating "equivalent" instructions.
  void CacheFloatConstant(HFloatConstant* constant);

  // See CacheFloatConstant comment.
  void CacheDoubleConstant(HDoubleConstant* constant);

  ArenaAllocator* const arena_;

  // List of blocks in insertion order.
  GrowableArray<HBasicBlock*> blocks_;

  // List of blocks to perform a reverse post order tree traversal.
  GrowableArray<HBasicBlock*> reverse_post_order_;

  // List of blocks to perform a linear order tree traversal.
  GrowableArray<HBasicBlock*> linear_order_;

  HBasicBlock* entry_block_;
  HBasicBlock* exit_block_;

  // The maximum number of virtual registers arguments passed to a HInvoke in this graph.
  uint16_t maximum_number_of_out_vregs_;

  // The number of virtual registers in this method. Contains the parameters.
  uint16_t number_of_vregs_;

  // The number of virtual registers used by parameters of this method.
  uint16_t number_of_in_vregs_;

  // Number of vreg size slots that the temporaries use (used in baseline compiler).
  size_t temporaries_vreg_slots_;

  // Has bounds checks. We can totally skip BCE if it's false.
  bool has_bounds_checks_;

  // Indicates whether the graph should be compiled in a way that
  // ensures full debuggability. If false, we can apply more
  // aggressive optimizations that may limit the level of debugging.
  const bool debuggable_;

  // The current id to assign to a newly added instruction. See HInstruction.id_.
  int32_t current_instruction_id_;

  // The dex file from which the method is from.
  const DexFile& dex_file_;

  // The method index in the dex file.
  const uint32_t method_idx_;

  // If inlined, this encodes how the callee is being invoked.
  const InvokeType invoke_type_;

  // Whether the graph has been transformed to SSA form. Only used
  // in debug mode to ensure we are not using properties only valid
  // for non-SSA form (like the number of temporaries).
  bool in_ssa_form_;

  const bool should_generate_constructor_barrier_;

  const InstructionSet instruction_set_;

  // Cached constants.
  HNullConstant* cached_null_constant_;
  ArenaSafeMap<int32_t, HIntConstant*> cached_int_constants_;
  ArenaSafeMap<int32_t, HFloatConstant*> cached_float_constants_;
  ArenaSafeMap<int64_t, HLongConstant*> cached_long_constants_;
  ArenaSafeMap<int64_t, HDoubleConstant*> cached_double_constants_;

  HCurrentMethod* cached_current_method_;

  friend class SsaBuilder;           // For caching constants.
  friend class SsaLivenessAnalysis;  // For the linear order.
  ART_FRIEND_TEST(GraphTest, IfSuccessorSimpleJoinBlock1);
  DISALLOW_COPY_AND_ASSIGN(HGraph);
};

class HLoopInformation : public ArenaObject<kArenaAllocMisc> {
 public:
  HLoopInformation(HBasicBlock* header, HGraph* graph)
      : header_(header),
        suspend_check_(nullptr),
        back_edges_(graph->GetArena(), kDefaultNumberOfBackEdges),
        // Make bit vector growable, as the number of blocks may change.
        blocks_(graph->GetArena(), graph->GetBlocks().Size(), true) {}

  HBasicBlock* GetHeader() const {
    return header_;
  }

  void SetHeader(HBasicBlock* block) {
    header_ = block;
  }

  HSuspendCheck* GetSuspendCheck() const { return suspend_check_; }
  void SetSuspendCheck(HSuspendCheck* check) { suspend_check_ = check; }
  bool HasSuspendCheck() const { return suspend_check_ != nullptr; }

  void AddBackEdge(HBasicBlock* back_edge) {
    back_edges_.Add(back_edge);
  }

  void RemoveBackEdge(HBasicBlock* back_edge) {
    back_edges_.Delete(back_edge);
  }

  bool IsBackEdge(const HBasicBlock& block) const {
    for (size_t i = 0, e = back_edges_.Size(); i < e; ++i) {
      if (back_edges_.Get(i) == &block) return true;
    }
    return false;
  }

  size_t NumberOfBackEdges() const {
    return back_edges_.Size();
  }

  HBasicBlock* GetPreHeader() const;

  const GrowableArray<HBasicBlock*>& GetBackEdges() const {
    return back_edges_;
  }

  // Returns the lifetime position of the back edge that has the
  // greatest lifetime position.
  size_t GetLifetimeEnd() const;

  void ReplaceBackEdge(HBasicBlock* existing, HBasicBlock* new_back_edge) {
    for (size_t i = 0, e = back_edges_.Size(); i < e; ++i) {
      if (back_edges_.Get(i) == existing) {
        back_edges_.Put(i, new_back_edge);
        return;
      }
    }
    UNREACHABLE();
  }

  // Finds blocks that are part of this loop. Returns whether the loop is a natural loop,
  // that is the header dominates the back edge.
  bool Populate();

  // Reanalyzes the loop by removing loop info from its blocks and re-running
  // Populate(). If there are no back edges left, the loop info is completely
  // removed as well as its SuspendCheck instruction. It must be run on nested
  // inner loops first.
  void Update();

  // Returns whether this loop information contains `block`.
  // Note that this loop information *must* be populated before entering this function.
  bool Contains(const HBasicBlock& block) const;

  // Returns whether this loop information is an inner loop of `other`.
  // Note that `other` *must* be populated before entering this function.
  bool IsIn(const HLoopInformation& other) const;

  const ArenaBitVector& GetBlocks() const { return blocks_; }

  void Add(HBasicBlock* block);
  void Remove(HBasicBlock* block);

 private:
  // Internal recursive implementation of `Populate`.
  void PopulateRecursive(HBasicBlock* block);

  HBasicBlock* header_;
  HSuspendCheck* suspend_check_;
  GrowableArray<HBasicBlock*> back_edges_;
  ArenaBitVector blocks_;

  DISALLOW_COPY_AND_ASSIGN(HLoopInformation);
};

static constexpr size_t kNoLifetime = -1;
static constexpr uint32_t kNoDexPc = -1;

// A block in a method. Contains the list of instructions represented
// as a double linked list. Each block knows its predecessors and
// successors.

class HBasicBlock : public ArenaObject<kArenaAllocMisc> {
 public:
  explicit HBasicBlock(HGraph* graph, uint32_t dex_pc = kNoDexPc)
      : graph_(graph),
        predecessors_(graph->GetArena(), kDefaultNumberOfPredecessors),
        successors_(graph->GetArena(), kDefaultNumberOfSuccessors),
        loop_information_(nullptr),
        dominator_(nullptr),
        dominated_blocks_(graph->GetArena(), kDefaultNumberOfDominatedBlocks),
        block_id_(-1),
        dex_pc_(dex_pc),
        lifetime_start_(kNoLifetime),
        lifetime_end_(kNoLifetime),
        is_catch_block_(false) {}

  const GrowableArray<HBasicBlock*>& GetPredecessors() const {
    return predecessors_;
  }

  const GrowableArray<HBasicBlock*>& GetSuccessors() const {
    return successors_;
  }

  const GrowableArray<HBasicBlock*>& GetDominatedBlocks() const {
    return dominated_blocks_;
  }

  bool IsEntryBlock() const {
    return graph_->GetEntryBlock() == this;
  }

  bool IsExitBlock() const {
    return graph_->GetExitBlock() == this;
  }

  bool IsSingleGoto() const;
  bool IsSingleTryBoundary() const;

  // Returns true if this block emits nothing but a jump.
  bool IsSingleJump() const {
    HLoopInformation* loop_info = GetLoopInformation();
    return (IsSingleGoto() || IsSingleTryBoundary())
           // Back edges generate a suspend check.
           && (loop_info == nullptr || !loop_info->IsBackEdge(*this));
  }

  void AddBackEdge(HBasicBlock* back_edge) {
    if (loop_information_ == nullptr) {
      loop_information_ = new (graph_->GetArena()) HLoopInformation(this, graph_);
    }
    DCHECK_EQ(loop_information_->GetHeader(), this);
    loop_information_->AddBackEdge(back_edge);
  }

  HGraph* GetGraph() const { return graph_; }
  void SetGraph(HGraph* graph) { graph_ = graph; }

  int GetBlockId() const { return block_id_; }
  void SetBlockId(int id) { block_id_ = id; }

  HBasicBlock* GetDominator() const { return dominator_; }
  void SetDominator(HBasicBlock* dominator) { dominator_ = dominator; }
  void AddDominatedBlock(HBasicBlock* block) { dominated_blocks_.Add(block); }
  void RemoveDominatedBlock(HBasicBlock* block) { dominated_blocks_.Delete(block); }
  void ReplaceDominatedBlock(HBasicBlock* existing, HBasicBlock* new_block) {
    for (size_t i = 0, e = dominated_blocks_.Size(); i < e; ++i) {
      if (dominated_blocks_.Get(i) == existing) {
        dominated_blocks_.Put(i, new_block);
        return;
      }
    }
    LOG(FATAL) << "Unreachable";
    UNREACHABLE();
  }
  void ClearDominanceInformation();

  int NumberOfBackEdges() const {
    return IsLoopHeader() ? loop_information_->NumberOfBackEdges() : 0;
  }

  HInstruction* GetFirstInstruction() const { return instructions_.first_instruction_; }
  HInstruction* GetLastInstruction() const { return instructions_.last_instruction_; }
  const HInstructionList& GetInstructions() const { return instructions_; }
  HInstruction* GetFirstPhi() const { return phis_.first_instruction_; }
  HInstruction* GetLastPhi() const { return phis_.last_instruction_; }
  const HInstructionList& GetPhis() const { return phis_; }

  void AddSuccessor(HBasicBlock* block) {
    successors_.Add(block);
    block->predecessors_.Add(this);
  }

  void ReplaceSuccessor(HBasicBlock* existing, HBasicBlock* new_block) {
    size_t successor_index = GetSuccessorIndexOf(existing);
    DCHECK_NE(successor_index, static_cast<size_t>(-1));
    existing->RemovePredecessor(this);
    new_block->predecessors_.Add(this);
    successors_.Put(successor_index, new_block);
  }

  void ReplacePredecessor(HBasicBlock* existing, HBasicBlock* new_block) {
    size_t predecessor_index = GetPredecessorIndexOf(existing);
    DCHECK_NE(predecessor_index, static_cast<size_t>(-1));
    existing->RemoveSuccessor(this);
    new_block->successors_.Add(this);
    predecessors_.Put(predecessor_index, new_block);
  }

  // Insert `this` between `predecessor` and `successor. This method
  // preserves the indicies, and will update the first edge found between
  // `predecessor` and `successor`.
  void InsertBetween(HBasicBlock* predecessor, HBasicBlock* successor) {
    size_t predecessor_index = successor->GetPredecessorIndexOf(predecessor);
    DCHECK_NE(predecessor_index, static_cast<size_t>(-1));
    size_t successor_index = predecessor->GetSuccessorIndexOf(successor);
    DCHECK_NE(successor_index, static_cast<size_t>(-1));
    successor->predecessors_.Put(predecessor_index, this);
    predecessor->successors_.Put(successor_index, this);
    successors_.Add(successor);
    predecessors_.Add(predecessor);
  }

  void RemovePredecessor(HBasicBlock* block) {
    predecessors_.Delete(block);
  }

  void RemoveSuccessor(HBasicBlock* block) {
    successors_.Delete(block);
  }

  void ClearAllPredecessors() {
    predecessors_.Reset();
  }

  void AddPredecessor(HBasicBlock* block) {
    predecessors_.Add(block);
    block->successors_.Add(this);
  }

  void SwapPredecessors() {
    DCHECK_EQ(predecessors_.Size(), 2u);
    HBasicBlock* temp = predecessors_.Get(0);
    predecessors_.Put(0, predecessors_.Get(1));
    predecessors_.Put(1, temp);
  }

  void SwapSuccessors() {
    DCHECK_EQ(successors_.Size(), 2u);
    HBasicBlock* temp = successors_.Get(0);
    successors_.Put(0, successors_.Get(1));
    successors_.Put(1, temp);
  }

  size_t GetPredecessorIndexOf(HBasicBlock* predecessor) const {
    for (size_t i = 0, e = predecessors_.Size(); i < e; ++i) {
      if (predecessors_.Get(i) == predecessor) {
        return i;
      }
    }
    return -1;
  }

  size_t GetSuccessorIndexOf(HBasicBlock* successor) const {
    for (size_t i = 0, e = successors_.Size(); i < e; ++i) {
      if (successors_.Get(i) == successor) {
        return i;
      }
    }
    return -1;
  }

  HBasicBlock* GetSinglePredecessor() const {
    DCHECK_EQ(GetPredecessors().Size(), 1u);
    return GetPredecessors().Get(0);
  }

  HBasicBlock* GetSingleSuccessor() const {
    DCHECK_EQ(GetSuccessors().Size(), 1u);
    return GetSuccessors().Get(0);
  }

  // Returns whether the first occurrence of `predecessor` in the list of
  // predecessors is at index `idx`.
  bool IsFirstIndexOfPredecessor(HBasicBlock* predecessor, size_t idx) const {
    DCHECK_EQ(GetPredecessors().Get(idx), predecessor);
    return GetPredecessorIndexOf(predecessor) == idx;
  }

  // Returns whether successor at index `idx` is an exception handler.
  bool IsExceptionalSuccessor(size_t idx) const;

  // Split the block into two blocks just before `cursor`. Returns the newly
  // created, latter block. Note that this method will add the block to the
  // graph, create a Goto at the end of the former block and will create an edge
  // between the blocks. It will not, however, update the reverse post order or
  // loop information.
  HBasicBlock* SplitBefore(HInstruction* cursor);

  // Split the block into two blocks just after `cursor`. Returns the newly
  // created block. Note that this method just updates raw block information,
  // like predecessors, successors, dominators, and instruction list. It does not
  // update the graph, reverse post order, loop information, nor make sure the
  // blocks are consistent (for example ending with a control flow instruction).
  HBasicBlock* SplitAfter(HInstruction* cursor);

  // Merge `other` at the end of `this`. Successors and dominated blocks of
  // `other` are changed to be successors and dominated blocks of `this`. Note
  // that this method does not update the graph, reverse post order, loop
  // information, nor make sure the blocks are consistent (for example ending
  // with a control flow instruction).
  void MergeWithInlined(HBasicBlock* other);

  // Replace `this` with `other`. Predecessors, successors, and dominated blocks
  // of `this` are moved to `other`.
  // Note that this method does not update the graph, reverse post order, loop
  // information, nor make sure the blocks are consistent (for example ending
  // with a control flow instruction).
  void ReplaceWith(HBasicBlock* other);

  // Merge `other` at the end of `this`. This method updates loops, reverse post
  // order, links to predecessors, successors, dominators and deletes the block
  // from the graph. The two blocks must be successive, i.e. `this` the only
  // predecessor of `other` and vice versa.
  void MergeWith(HBasicBlock* other);

  // Disconnects `this` from all its predecessors, successors and dominator,
  // removes it from all loops it is included in and eventually from the graph.
  // The block must not dominate any other block. Predecessors and successors
  // are safely updated.
  void DisconnectAndDelete();

  void AddInstruction(HInstruction* instruction);
  // Insert `instruction` before/after an existing instruction `cursor`.
  void InsertInstructionBefore(HInstruction* instruction, HInstruction* cursor);
  void InsertInstructionAfter(HInstruction* instruction, HInstruction* cursor);
  // Replace instruction `initial` with `replacement` within this block.
  void ReplaceAndRemoveInstructionWith(HInstruction* initial,
                                       HInstruction* replacement);
  void AddPhi(HPhi* phi);
  void InsertPhiAfter(HPhi* instruction, HPhi* cursor);
  // RemoveInstruction and RemovePhi delete a given instruction from the respective
  // instruction list. With 'ensure_safety' set to true, it verifies that the
  // instruction is not in use and removes it from the use lists of its inputs.
  void RemoveInstruction(HInstruction* instruction, bool ensure_safety = true);
  void RemovePhi(HPhi* phi, bool ensure_safety = true);
  void RemoveInstructionOrPhi(HInstruction* instruction, bool ensure_safety = true);

  bool IsLoopHeader() const {
    return IsInLoop() && (loop_information_->GetHeader() == this);
  }

  bool IsLoopPreHeaderFirstPredecessor() const {
    DCHECK(IsLoopHeader());
    DCHECK(!GetPredecessors().IsEmpty());
    return GetPredecessors().Get(0) == GetLoopInformation()->GetPreHeader();
  }

  HLoopInformation* GetLoopInformation() const {
    return loop_information_;
  }

  // Set the loop_information_ on this block. Overrides the current
  // loop_information if it is an outer loop of the passed loop information.
  // Note that this method is called while creating the loop information.
  void SetInLoop(HLoopInformation* info) {
    if (IsLoopHeader()) {
      // Nothing to do. This just means `info` is an outer loop.
    } else if (!IsInLoop()) {
      loop_information_ = info;
    } else if (loop_information_->Contains(*info->GetHeader())) {
      // Block is currently part of an outer loop. Make it part of this inner loop.
      // Note that a non loop header having a loop information means this loop information
      // has already been populated
      loop_information_ = info;
    } else {
      // Block is part of an inner loop. Do not update the loop information.
      // Note that we cannot do the check `info->Contains(loop_information_)->GetHeader()`
      // at this point, because this method is being called while populating `info`.
    }
  }

  // Raw update of the loop information.
  void SetLoopInformation(HLoopInformation* info) {
    loop_information_ = info;
  }

  bool IsInLoop() const { return loop_information_ != nullptr; }

  // Returns whether this block dominates the blocked passed as parameter.
  bool Dominates(HBasicBlock* block) const;

  size_t GetLifetimeStart() const { return lifetime_start_; }
  size_t GetLifetimeEnd() const { return lifetime_end_; }

  void SetLifetimeStart(size_t start) { lifetime_start_ = start; }
  void SetLifetimeEnd(size_t end) { lifetime_end_ = end; }

  uint32_t GetDexPc() const { return dex_pc_; }

  bool IsCatchBlock() const { return is_catch_block_; }
  void SetIsCatchBlock() { is_catch_block_ = true; }

  bool EndsWithControlFlowInstruction() const;
  bool EndsWithIf() const;
  bool HasSinglePhi() const;

 private:
  HGraph* graph_;
  GrowableArray<HBasicBlock*> predecessors_;
  GrowableArray<HBasicBlock*> successors_;
  HInstructionList instructions_;
  HInstructionList phis_;
  HLoopInformation* loop_information_;
  HBasicBlock* dominator_;
  GrowableArray<HBasicBlock*> dominated_blocks_;
  int block_id_;
  // The dex program counter of the first instruction of this block.
  const uint32_t dex_pc_;
  size_t lifetime_start_;
  size_t lifetime_end_;
  bool is_catch_block_;

  friend class HGraph;
  friend class HInstruction;

  DISALLOW_COPY_AND_ASSIGN(HBasicBlock);
};

// Iterates over the LoopInformation of all loops which contain 'block'
// from the innermost to the outermost.
class HLoopInformationOutwardIterator : public ValueObject {
 public:
  explicit HLoopInformationOutwardIterator(const HBasicBlock& block)
      : current_(block.GetLoopInformation()) {}

  bool Done() const { return current_ == nullptr; }

  void Advance() {
    DCHECK(!Done());
    current_ = current_->GetPreHeader()->GetLoopInformation();
  }

  HLoopInformation* Current() const {
    DCHECK(!Done());
    return current_;
  }

 private:
  HLoopInformation* current_;

  DISALLOW_COPY_AND_ASSIGN(HLoopInformationOutwardIterator);
};

#define FOR_EACH_CONCRETE_INSTRUCTION_COMMON(M)                         \
  M(Add, BinaryOperation)                                               \
  M(And, BinaryOperation)                                               \
  M(ArrayGet, Instruction)                                              \
  M(ArrayLength, Instruction)                                           \
  M(ArraySet, Instruction)                                              \
  M(BooleanNot, UnaryOperation)                                         \
  M(BoundsCheck, Instruction)                                           \
  M(BoundType, Instruction)                                             \
  M(CheckCast, Instruction)                                             \
  M(ClinitCheck, Instruction)                                           \
  M(Compare, BinaryOperation)                                           \
  M(Condition, BinaryOperation)                                         \
  M(CurrentMethod, Instruction)                                         \
  M(Deoptimize, Instruction)                                            \
  M(Div, BinaryOperation)                                               \
  M(DivZeroCheck, Instruction)                                          \
  M(DoubleConstant, Constant)                                           \
  M(Equal, Condition)                                                   \
  M(Exit, Instruction)                                                  \
  M(FloatConstant, Constant)                                            \
  M(Goto, Instruction)                                                  \
  M(GreaterThan, Condition)                                             \
  M(GreaterThanOrEqual, Condition)                                      \
  M(If, Instruction)                                                    \
  M(InstanceFieldGet, Instruction)                                      \
  M(InstanceFieldSet, Instruction)                                      \
  M(InstanceOf, Instruction)                                            \
  M(IntConstant, Constant)                                              \
  M(InvokeInterface, Invoke)                                            \
  M(InvokeStaticOrDirect, Invoke)                                       \
  M(InvokeVirtual, Invoke)                                              \
  M(LessThan, Condition)                                                \
  M(LessThanOrEqual, Condition)                                         \
  M(LoadClass, Instruction)                                             \
  M(LoadException, Instruction)                                         \
  M(LoadLocal, Instruction)                                             \
  M(LoadString, Instruction)                                            \
  M(Local, Instruction)                                                 \
  M(LongConstant, Constant)                                             \
  M(MemoryBarrier, Instruction)                                         \
  M(MonitorOperation, Instruction)                                      \
  M(Mul, BinaryOperation)                                               \
  M(Neg, UnaryOperation)                                                \
  M(NewArray, Instruction)                                              \
  M(NewInstance, Instruction)                                           \
  M(Not, UnaryOperation)                                                \
  M(NotEqual, Condition)                                                \
  M(NullConstant, Instruction)                                          \
  M(NullCheck, Instruction)                                             \
  M(Or, BinaryOperation)                                                \
  M(ParallelMove, Instruction)                                          \
  M(ParameterValue, Instruction)                                        \
  M(Phi, Instruction)                                                   \
  M(Rem, BinaryOperation)                                               \
  M(Return, Instruction)                                                \
  M(ReturnVoid, Instruction)                                            \
  M(Shl, BinaryOperation)                                               \
  M(Shr, BinaryOperation)                                               \
  M(StaticFieldGet, Instruction)                                        \
  M(StaticFieldSet, Instruction)                                        \
  M(StoreLocal, Instruction)                                            \
  M(Sub, BinaryOperation)                                               \
  M(SuspendCheck, Instruction)                                          \
  M(Temporary, Instruction)                                             \
  M(Throw, Instruction)                                                 \
  M(TryBoundary, Instruction)                                           \
  M(TypeConversion, Instruction)                                        \
  M(UShr, BinaryOperation)                                              \
  M(Xor, BinaryOperation)                                               \

#define FOR_EACH_CONCRETE_INSTRUCTION_ARM(M)

#define FOR_EACH_CONCRETE_INSTRUCTION_ARM64(M)

#define FOR_EACH_CONCRETE_INSTRUCTION_MIPS64(M)

#define FOR_EACH_CONCRETE_INSTRUCTION_X86(M)

#define FOR_EACH_CONCRETE_INSTRUCTION_X86_64(M)

#define FOR_EACH_CONCRETE_INSTRUCTION(M)                                \
  FOR_EACH_CONCRETE_INSTRUCTION_COMMON(M)                               \
  FOR_EACH_CONCRETE_INSTRUCTION_ARM(M)                                  \
  FOR_EACH_CONCRETE_INSTRUCTION_ARM64(M)                                \
  FOR_EACH_CONCRETE_INSTRUCTION_MIPS64(M)                               \
  FOR_EACH_CONCRETE_INSTRUCTION_X86(M)                                  \
  FOR_EACH_CONCRETE_INSTRUCTION_X86_64(M)

#define FOR_EACH_INSTRUCTION(M)                                         \
  FOR_EACH_CONCRETE_INSTRUCTION(M)                                      \
  M(Constant, Instruction)                                              \
  M(UnaryOperation, Instruction)                                        \
  M(BinaryOperation, Instruction)                                       \
  M(Invoke, Instruction)

#define FORWARD_DECLARATION(type, super) class H##type;
FOR_EACH_INSTRUCTION(FORWARD_DECLARATION)
#undef FORWARD_DECLARATION

#define DECLARE_INSTRUCTION(type)                                       \
  InstructionKind GetKind() const OVERRIDE { return k##type; }          \
  const char* DebugName() const OVERRIDE { return #type; }              \
  const H##type* As##type() const OVERRIDE { return this; }             \
  H##type* As##type() OVERRIDE { return this; }                         \
  bool InstructionTypeEquals(HInstruction* other) const OVERRIDE {      \
    return other->Is##type();                                           \
  }                                                                     \
  void Accept(HGraphVisitor* visitor) OVERRIDE

template <typename T> class HUseList;

template <typename T>
class HUseListNode : public ArenaObject<kArenaAllocMisc> {
 public:
  HUseListNode* GetPrevious() const { return prev_; }
  HUseListNode* GetNext() const { return next_; }
  T GetUser() const { return user_; }
  size_t GetIndex() const { return index_; }
  void SetIndex(size_t index) { index_ = index; }

 private:
  HUseListNode(T user, size_t index)
      : user_(user), index_(index), prev_(nullptr), next_(nullptr) {}

  T const user_;
  size_t index_;
  HUseListNode<T>* prev_;
  HUseListNode<T>* next_;

  friend class HUseList<T>;

  DISALLOW_COPY_AND_ASSIGN(HUseListNode);
};

template <typename T>
class HUseList : public ValueObject {
 public:
  HUseList() : first_(nullptr) {}

  void Clear() {
    first_ = nullptr;
  }

  // Adds a new entry at the beginning of the use list and returns
  // the newly created node.
  HUseListNode<T>* AddUse(T user, size_t index, ArenaAllocator* arena) {
    HUseListNode<T>* new_node = new (arena) HUseListNode<T>(user, index);
    if (IsEmpty()) {
      first_ = new_node;
    } else {
      first_->prev_ = new_node;
      new_node->next_ = first_;
      first_ = new_node;
    }
    return new_node;
  }

  HUseListNode<T>* GetFirst() const {
    return first_;
  }

  void Remove(HUseListNode<T>* node) {
    DCHECK(node != nullptr);
    DCHECK(Contains(node));

    if (node->prev_ != nullptr) {
      node->prev_->next_ = node->next_;
    }
    if (node->next_ != nullptr) {
      node->next_->prev_ = node->prev_;
    }
    if (node == first_) {
      first_ = node->next_;
    }
  }

  bool Contains(const HUseListNode<T>* node) const {
    if (node == nullptr) {
      return false;
    }
    for (HUseListNode<T>* current = first_; current != nullptr; current = current->GetNext()) {
      if (current == node) {
        return true;
      }
    }
    return false;
  }

  bool IsEmpty() const {
    return first_ == nullptr;
  }

  bool HasOnlyOneUse() const {
    return first_ != nullptr && first_->next_ == nullptr;
  }

  size_t SizeSlow() const {
    size_t count = 0;
    for (HUseListNode<T>* current = first_; current != nullptr; current = current->GetNext()) {
      ++count;
    }
    return count;
  }

 private:
  HUseListNode<T>* first_;
};

template<typename T>
class HUseIterator : public ValueObject {
 public:
  explicit HUseIterator(const HUseList<T>& uses) : current_(uses.GetFirst()) {}

  bool Done() const { return current_ == nullptr; }

  void Advance() {
    DCHECK(!Done());
    current_ = current_->GetNext();
  }

  HUseListNode<T>* Current() const {
    DCHECK(!Done());
    return current_;
  }

 private:
  HUseListNode<T>* current_;

  friend class HValue;
};

// This class is used by HEnvironment and HInstruction classes to record the
// instructions they use and pointers to the corresponding HUseListNodes kept
// by the used instructions.
template <typename T>
class HUserRecord : public ValueObject {
 public:
  HUserRecord() : instruction_(nullptr), use_node_(nullptr) {}
  explicit HUserRecord(HInstruction* instruction) : instruction_(instruction), use_node_(nullptr) {}

  HUserRecord(const HUserRecord<T>& old_record, HUseListNode<T>* use_node)
    : instruction_(old_record.instruction_), use_node_(use_node) {
    DCHECK(instruction_ != nullptr);
    DCHECK(use_node_ != nullptr);
    DCHECK(old_record.use_node_ == nullptr);
  }

  HInstruction* GetInstruction() const { return instruction_; }
  HUseListNode<T>* GetUseNode() const { return use_node_; }

 private:
  // Instruction used by the user.
  HInstruction* instruction_;

  // Corresponding entry in the use list kept by 'instruction_'.
  HUseListNode<T>* use_node_;
};

// TODO: Add better documentation to this class and maybe refactor with more suggestive names.
// - Has(All)SideEffects suggests that all the side effects are present but only ChangesSomething
//   flag is consider.
// - DependsOn suggests that there is a real dependency between side effects but it only
//   checks DependendsOnSomething flag.
//
// Represents the side effects an instruction may have.
class SideEffects : public ValueObject {
 public:
  SideEffects() : flags_(0) {}

  static SideEffects None() {
    return SideEffects(0);
  }

  static SideEffects All() {
    return SideEffects(ChangesSomething().flags_ | DependsOnSomething().flags_);
  }

  static SideEffects ChangesSomething() {
    return SideEffects((1 << kFlagChangesCount) - 1);
  }

  static SideEffects DependsOnSomething() {
    int count = kFlagDependsOnCount - kFlagChangesCount;
    return SideEffects(((1 << count) - 1) << kFlagChangesCount);
  }

  SideEffects Union(SideEffects other) const {
    return SideEffects(flags_ | other.flags_);
  }

  bool HasSideEffects() const {
    size_t all_bits_set = (1 << kFlagChangesCount) - 1;
    return (flags_ & all_bits_set) != 0;
  }

  bool HasAllSideEffects() const {
    size_t all_bits_set = (1 << kFlagChangesCount) - 1;
    return all_bits_set == (flags_ & all_bits_set);
  }

  bool DependsOn(SideEffects other) const {
    size_t depends_flags = other.ComputeDependsFlags();
    return (flags_ & depends_flags) != 0;
  }

  bool HasDependencies() const {
    int count = kFlagDependsOnCount - kFlagChangesCount;
    size_t all_bits_set = (1 << count) - 1;
    return ((flags_ >> kFlagChangesCount) & all_bits_set) != 0;
  }

 private:
  static constexpr int kFlagChangesSomething = 0;
  static constexpr int kFlagChangesCount = kFlagChangesSomething + 1;

  static constexpr int kFlagDependsOnSomething = kFlagChangesCount;
  static constexpr int kFlagDependsOnCount = kFlagDependsOnSomething + 1;

  explicit SideEffects(size_t flags) : flags_(flags) {}

  size_t ComputeDependsFlags() const {
    return flags_ << kFlagChangesCount;
  }

  size_t flags_;
};

// A HEnvironment object contains the values of virtual registers at a given location.
class HEnvironment : public ArenaObject<kArenaAllocMisc> {
 public:
  HEnvironment(ArenaAllocator* arena,
               size_t number_of_vregs,
               const DexFile& dex_file,
               uint32_t method_idx,
               uint32_t dex_pc,
               InvokeType invoke_type,
               HInstruction* holder)
     : vregs_(arena, number_of_vregs),
       locations_(arena, number_of_vregs),
       parent_(nullptr),
       dex_file_(dex_file),
       method_idx_(method_idx),
       dex_pc_(dex_pc),
       invoke_type_(invoke_type),
       holder_(holder) {
    vregs_.SetSize(number_of_vregs);
    for (size_t i = 0; i < number_of_vregs; i++) {
      vregs_.Put(i, HUserRecord<HEnvironment*>());
    }

    locations_.SetSize(number_of_vregs);
    for (size_t i = 0; i < number_of_vregs; ++i) {
      locations_.Put(i, Location());
    }
  }

  HEnvironment(ArenaAllocator* arena, const HEnvironment& to_copy, HInstruction* holder)
      : HEnvironment(arena,
                     to_copy.Size(),
                     to_copy.GetDexFile(),
                     to_copy.GetMethodIdx(),
                     to_copy.GetDexPc(),
                     to_copy.GetInvokeType(),
                     holder) {}

  void SetAndCopyParentChain(ArenaAllocator* allocator, HEnvironment* parent) {
    if (parent_ != nullptr) {
      parent_->SetAndCopyParentChain(allocator, parent);
    } else {
      parent_ = new (allocator) HEnvironment(allocator, *parent, holder_);
      parent_->CopyFrom(parent);
      if (parent->GetParent() != nullptr) {
        parent_->SetAndCopyParentChain(allocator, parent->GetParent());
      }
    }
  }

  void CopyFrom(const GrowableArray<HInstruction*>& locals);
  void CopyFrom(HEnvironment* environment);

  // Copy from `env`. If it's a loop phi for `loop_header`, copy the first
  // input to the loop phi instead. This is for inserting instructions that
  // require an environment (like HDeoptimization) in the loop pre-header.
  void CopyFromWithLoopPhiAdjustment(HEnvironment* env, HBasicBlock* loop_header);

  void SetRawEnvAt(size_t index, HInstruction* instruction) {
    vregs_.Put(index, HUserRecord<HEnvironment*>(instruction));
  }

  HInstruction* GetInstructionAt(size_t index) const {
    return vregs_.Get(index).GetInstruction();
  }

  void RemoveAsUserOfInput(size_t index) const;

  size_t Size() const { return vregs_.Size(); }

  HEnvironment* GetParent() const { return parent_; }

  void SetLocationAt(size_t index, Location location) {
    locations_.Put(index, location);
  }

  Location GetLocationAt(size_t index) const {
    return locations_.Get(index);
  }

  uint32_t GetDexPc() const {
    return dex_pc_;
  }

  uint32_t GetMethodIdx() const {
    return method_idx_;
  }

  InvokeType GetInvokeType() const {
    return invoke_type_;
  }

  const DexFile& GetDexFile() const {
    return dex_file_;
  }

  HInstruction* GetHolder() const {
    return holder_;
  }

 private:
  // Record instructions' use entries of this environment for constant-time removal.
  // It should only be called by HInstruction when a new environment use is added.
  void RecordEnvUse(HUseListNode<HEnvironment*>* env_use) {
    DCHECK(env_use->GetUser() == this);
    size_t index = env_use->GetIndex();
    vregs_.Put(index, HUserRecord<HEnvironment*>(vregs_.Get(index), env_use));
  }

  GrowableArray<HUserRecord<HEnvironment*> > vregs_;
  GrowableArray<Location> locations_;
  HEnvironment* parent_;
  const DexFile& dex_file_;
  const uint32_t method_idx_;
  const uint32_t dex_pc_;
  const InvokeType invoke_type_;

  // The instruction that holds this environment. Only used in debug mode
  // to ensure the graph is consistent.
  HInstruction* const holder_;

  friend class HInstruction;

  DISALLOW_COPY_AND_ASSIGN(HEnvironment);
};

class ReferenceTypeInfo : ValueObject {
 public:
  typedef Handle<mirror::Class> TypeHandle;

  static ReferenceTypeInfo Create(TypeHandle type_handle, bool is_exact)
      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    if (type_handle->IsObjectClass()) {
      // Override the type handle to be consistent with the case when we get to
      // Top but don't have the Object class available. It avoids having to guess
      // what value the type_handle has when it's Top.
      return ReferenceTypeInfo(TypeHandle(), is_exact, true);
    } else {
      return ReferenceTypeInfo(type_handle, is_exact, false);
    }
  }

  static ReferenceTypeInfo CreateTop(bool is_exact) {
    return ReferenceTypeInfo(TypeHandle(), is_exact, true);
  }

  bool IsExact() const { return is_exact_; }
  bool IsTop() const { return is_top_; }
  bool IsInterface() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    return !IsTop() && GetTypeHandle()->IsInterface();
  }

  Handle<mirror::Class> GetTypeHandle() const { return type_handle_; }

  bool IsSupertypeOf(ReferenceTypeInfo rti) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    if (IsTop()) {
      // Top (equivalent for java.lang.Object) is supertype of anything.
      return true;
    }
    if (rti.IsTop()) {
      // If we get here `this` is not Top() so it can't be a supertype.
      return false;
    }
    return GetTypeHandle()->IsAssignableFrom(rti.GetTypeHandle().Get());
  }

  // Returns true if the type information provide the same amount of details.
  // Note that it does not mean that the instructions have the same actual type
  // (e.g. tops are equal but they can be the result of a merge).
  bool IsEqual(ReferenceTypeInfo rti) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
    if (IsExact() != rti.IsExact()) {
      return false;
    }
    if (IsTop() && rti.IsTop()) {
      // `Top` means java.lang.Object, so the types are equivalent.
      return true;
    }
    if (IsTop() || rti.IsTop()) {
      // If only one is top or object than they are not equivalent.
      // NB: We need this extra check because the type_handle of `Top` is invalid
      // and we cannot inspect its reference.
      return false;
    }

    // Finally check the types.
    return GetTypeHandle().Get() == rti.GetTypeHandle().Get();
  }

 private:
  ReferenceTypeInfo() : ReferenceTypeInfo(TypeHandle(), false, true) {}
  ReferenceTypeInfo(TypeHandle type_handle, bool is_exact, bool is_top)
      : type_handle_(type_handle), is_exact_(is_exact), is_top_(is_top) {}

  // The class of the object.
  TypeHandle type_handle_;
  // Whether or not the type is exact or a superclass of the actual type.
  // Whether or not we have any information about this type.
  bool is_exact_;
  // A true value here means that the object type should be java.lang.Object.
  // We don't have access to the corresponding mirror object every time so this
  // flag acts as a substitute. When true, the TypeHandle refers to a null
  // pointer and should not be used.
  bool is_top_;
};

std::ostream& operator<<(std::ostream& os, const ReferenceTypeInfo& rhs);

class HInstruction : public ArenaObject<kArenaAllocMisc> {
 public:
  explicit HInstruction(SideEffects side_effects)
      : previous_(nullptr),
        next_(nullptr),
        block_(nullptr),
        id_(-1),
        ssa_index_(-1),
        environment_(nullptr),
        locations_(nullptr),
        live_interval_(nullptr),
        lifetime_position_(kNoLifetime),
        side_effects_(side_effects),
        reference_type_info_(ReferenceTypeInfo::CreateTop(/* is_exact */ false)) {}

  virtual ~HInstruction() {}

#define DECLARE_KIND(type, super) k##type,
  enum InstructionKind {
    FOR_EACH_INSTRUCTION(DECLARE_KIND)
  };
#undef DECLARE_KIND

  HInstruction* GetNext() const { return next_; }
  HInstruction* GetPrevious() const { return previous_; }

  HInstruction* GetNextDisregardingMoves() const;
  HInstruction* GetPreviousDisregardingMoves() const;

  HBasicBlock* GetBlock() const { return block_; }
  void SetBlock(HBasicBlock* block) { block_ = block; }
  bool IsInBlock() const { return block_ != nullptr; }
  bool IsInLoop() const { return block_->IsInLoop(); }
  bool IsLoopHeaderPhi() { return IsPhi() && block_->IsLoopHeader(); }

  virtual size_t InputCount() const = 0;
  HInstruction* InputAt(size_t i) const { return InputRecordAt(i).GetInstruction(); }

  virtual void Accept(HGraphVisitor* visitor) = 0;
  virtual const char* DebugName() const = 0;

  virtual Primitive::Type GetType() const { return Primitive::kPrimVoid; }
  void SetRawInputAt(size_t index, HInstruction* input) {
    SetRawInputRecordAt(index, HUserRecord<HInstruction*>(input));
  }

  virtual bool NeedsEnvironment() const { return false; }
  virtual uint32_t GetDexPc() const {
    LOG(FATAL) << "GetDexPc() cannot be called on an instruction that"
                  " does not need an environment";
    UNREACHABLE();
  }
  virtual bool IsControlFlow() const { return false; }
  virtual bool CanThrow() const { return false; }
  bool HasSideEffects() const { return side_effects_.HasSideEffects(); }

  // Does not apply for all instructions, but having this at top level greatly
  // simplifies the null check elimination.
  virtual bool CanBeNull() const {
    DCHECK_EQ(GetType(), Primitive::kPrimNot) << "CanBeNull only applies to reference types";
    return true;
  }

  virtual bool CanDoImplicitNullCheckOn(HInstruction* obj) const {
    UNUSED(obj);
    return false;
  }

  void SetReferenceTypeInfo(ReferenceTypeInfo reference_type_info) {
    DCHECK_EQ(GetType(), Primitive::kPrimNot);
    reference_type_info_ = reference_type_info;
  }

  ReferenceTypeInfo GetReferenceTypeInfo() const {
    DCHECK_EQ(GetType(), Primitive::kPrimNot);
    return reference_type_info_;
  }

  void AddUseAt(HInstruction* user, size_t index) {
    DCHECK(user != nullptr);
    HUseListNode<HInstruction*>* use =
        uses_.AddUse(user, index, GetBlock()->GetGraph()->GetArena());
    user->SetRawInputRecordAt(index, HUserRecord<HInstruction*>(user->InputRecordAt(index), use));
  }

  void AddEnvUseAt(HEnvironment* user, size_t index) {
    DCHECK(user != nullptr);
    HUseListNode<HEnvironment*>* env_use =
        env_uses_.AddUse(user, index, GetBlock()->GetGraph()->GetArena());
    user->RecordEnvUse(env_use);
  }

  void RemoveAsUserOfInput(size_t input) {
    HUserRecord<HInstruction*> input_use = InputRecordAt(input);
    input_use.GetInstruction()->uses_.Remove(input_use.GetUseNode());
  }

  const HUseList<HInstruction*>& GetUses() const { return uses_; }
  const HUseList<HEnvironment*>& GetEnvUses() const { return env_uses_; }

  bool HasUses() const { return !uses_.IsEmpty() || !env_uses_.IsEmpty(); }
  bool HasEnvironmentUses() const { return !env_uses_.IsEmpty(); }
  bool HasNonEnvironmentUses() const { return !uses_.IsEmpty(); }
  bool HasOnlyOneNonEnvironmentUse() const {
    return !HasEnvironmentUses() && GetUses().HasOnlyOneUse();
  }

  // Does this instruction strictly dominate `other_instruction`?
  // Returns false if this instruction and `other_instruction` are the same.
  // Aborts if this instruction and `other_instruction` are both phis.
  bool StrictlyDominates(HInstruction* other_instruction) const;

  int GetId() const { return id_; }
  void SetId(int id) { id_ = id; }

  int GetSsaIndex() const { return ssa_index_; }
  void SetSsaIndex(int ssa_index) { ssa_index_ = ssa_index; }
  bool HasSsaIndex() const { return ssa_index_ != -1; }

  bool HasEnvironment() const { return environment_ != nullptr; }
  HEnvironment* GetEnvironment() const { return environment_; }
  // Set the `environment_` field. Raw because this method does not
  // update the uses lists.
  void SetRawEnvironment(HEnvironment* environment) {
    DCHECK(environment_ == nullptr);
    DCHECK_EQ(environment->GetHolder(), this);
    environment_ = environment;
  }

  // Set the environment of this instruction, copying it from `environment`. While
  // copying, the uses lists are being updated.
  void CopyEnvironmentFrom(HEnvironment* environment) {
    DCHECK(environment_ == nullptr);
    ArenaAllocator* allocator = GetBlock()->GetGraph()->GetArena();
    environment_ = new (allocator) HEnvironment(allocator, *environment, this);
    environment_->CopyFrom(environment);
    if (environment->GetParent() != nullptr) {
      environment_->SetAndCopyParentChain(allocator, environment->GetParent());
    }
  }

  void CopyEnvironmentFromWithLoopPhiAdjustment(HEnvironment* environment,
                                                HBasicBlock* block) {
    DCHECK(environment_ == nullptr);
    ArenaAllocator* allocator = GetBlock()->GetGraph()->GetArena();
    environment_ = new (allocator) HEnvironment(allocator, *environment, this);
    environment_->CopyFromWithLoopPhiAdjustment(environment, block);
    if (environment->GetParent() != nullptr) {
      environment_->SetAndCopyParentChain(allocator, environment->GetParent());
    }
  }

  // Returns the number of entries in the environment. Typically, that is the
  // number of dex registers in a method. It could be more in case of inlining.
  size_t EnvironmentSize() const;

  LocationSummary* GetLocations() const { return locations_; }
  void SetLocations(LocationSummary* locations) { locations_ = locations; }

  void ReplaceWith(HInstruction* instruction);
  void ReplaceInput(HInstruction* replacement, size_t index);

  // This is almost the same as doing `ReplaceWith()`. But in this helper, the
  // uses of this instruction by `other` are *not* updated.
  void ReplaceWithExceptInReplacementAtIndex(HInstruction* other, size_t use_index) {
    ReplaceWith(other);
    other->ReplaceInput(this, use_index);
  }

  // Move `this` instruction before `cursor`.
  void MoveBefore(HInstruction* cursor);

#define INSTRUCTION_TYPE_CHECK(type, super)                                    \
  bool Is##type() const { return (As##type() != nullptr); }                    \
  virtual const H##type* As##type() const { return nullptr; }                  \
  virtual H##type* As##type() { return nullptr; }

  FOR_EACH_INSTRUCTION(INSTRUCTION_TYPE_CHECK)
#undef INSTRUCTION_TYPE_CHECK

  // Returns whether the instruction can be moved within the graph.
  virtual bool CanBeMoved() const { return false; }

  // Returns whether the two instructions are of the same kind.
  virtual bool InstructionTypeEquals(HInstruction* other) const {
    UNUSED(other);
    return false;
  }

  // Returns whether any data encoded in the two instructions is equal.
  // This method does not look at the inputs. Both instructions must be
  // of the same type, otherwise the method has undefined behavior.
  virtual bool InstructionDataEquals(HInstruction* other) const {
    UNUSED(other);
    return false;
  }

  // Returns whether two instructions are equal, that is:
  // 1) They have the same type and contain the same data (InstructionDataEquals).
  // 2) Their inputs are identical.
  bool Equals(HInstruction* other) const;

  virtual InstructionKind GetKind() const = 0;

  virtual size_t ComputeHashCode() const {
    size_t result = GetKind();
    for (size_t i = 0, e = InputCount(); i < e; ++i) {
      result = (result * 31) + InputAt(i)->GetId();
    }
    return result;
  }

  SideEffects GetSideEffects() const { return side_effects_; }

  size_t GetLifetimePosition() const { return lifetime_position_; }
  void SetLifetimePosition(size_t position) { lifetime_position_ = position; }
  LiveInterval* GetLiveInterval() const { return live_interval_; }
  void SetLiveInterval(LiveInterval* interval) { live_interval_ = interval; }
  bool HasLiveInterval() const { return live_interval_ != nullptr; }

  bool IsSuspendCheckEntry() const { return IsSuspendCheck() && GetBlock()->IsEntryBlock(); }

  // Returns whether the code generation of the instruction will require to have access
  // to the current method. Such instructions are:
  // (1): Instructions that require an environment, as calling the runtime requires
  //      to walk the stack and have the current method stored at a specific stack address.
  // (2): Object literals like classes and strings, that are loaded from the dex cache
  //      fields of the current method.
  bool NeedsCurrentMethod() const {
    return NeedsEnvironment() || IsLoadClass() || IsLoadString();
  }

  virtual bool NeedsDexCache() const { return false; }

 protected:
  virtual const HUserRecord<HInstruction*> InputRecordAt(size_t i) const = 0;
  virtual void SetRawInputRecordAt(size_t index, const HUserRecord<HInstruction*>& input) = 0;

 private:
  void RemoveEnvironmentUser(HUseListNode<HEnvironment*>* use_node) { env_uses_.Remove(use_node); }

  HInstruction* previous_;
  HInstruction* next_;
  HBasicBlock* block_;

  // An instruction gets an id when it is added to the graph.
  // It reflects creation order. A negative id means the instruction
  // has not been added to the graph.
  int id_;

  // When doing liveness analysis, instructions that have uses get an SSA index.
  int ssa_index_;

  // List of instructions that have this instruction as input.
  HUseList<HInstruction*> uses_;

  // List of environments that contain this instruction.
  HUseList<HEnvironment*> env_uses_;

  // The environment associated with this instruction. Not null if the instruction
  // might jump out of the method.
  HEnvironment* environment_;

  // Set by the code generator.
  LocationSummary* locations_;

  // Set by the liveness analysis.
  LiveInterval* live_interval_;

  // Set by the liveness analysis, this is the position in a linear
  // order of blocks where this instruction's live interval start.
  size_t lifetime_position_;

  const SideEffects side_effects_;

  // TODO: for primitive types this should be marked as invalid.
  ReferenceTypeInfo reference_type_info_;

  friend class GraphChecker;
  friend class HBasicBlock;
  friend class HEnvironment;
  friend class HGraph;
  friend class HInstructionList;

  DISALLOW_COPY_AND_ASSIGN(HInstruction);
};
std::ostream& operator<<(std::ostream& os, const HInstruction::InstructionKind& rhs);

class HInputIterator : public ValueObject {
 public:
  explicit HInputIterator(HInstruction* instruction) : instruction_(instruction), index_(0) {}

  bool Done() const { return index_ == instruction_->InputCount(); }
  HInstruction* Current() const { return instruction_->InputAt(index_); }
  void Advance() { index_++; }

 private:
  HInstruction* instruction_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HInputIterator);
};

class HInstructionIterator : public ValueObject {
 public:
  explicit HInstructionIterator(const HInstructionList& instructions)
      : instruction_(instructions.first_instruction_) {
    next_ = Done() ? nullptr : instruction_->GetNext();
  }

  bool Done() const { return instruction_ == nullptr; }
  HInstruction* Current() const { return instruction_; }
  void Advance() {
    instruction_ = next_;
    next_ = Done() ? nullptr : instruction_->GetNext();
  }

 private:
  HInstruction* instruction_;
  HInstruction* next_;

  DISALLOW_COPY_AND_ASSIGN(HInstructionIterator);
};

class HBackwardInstructionIterator : public ValueObject {
 public:
  explicit HBackwardInstructionIterator(const HInstructionList& instructions)
      : instruction_(instructions.last_instruction_) {
    next_ = Done() ? nullptr : instruction_->GetPrevious();
  }

  bool Done() const { return instruction_ == nullptr; }
  HInstruction* Current() const { return instruction_; }
  void Advance() {
    instruction_ = next_;
    next_ = Done() ? nullptr : instruction_->GetPrevious();
  }

 private:
  HInstruction* instruction_;
  HInstruction* next_;

  DISALLOW_COPY_AND_ASSIGN(HBackwardInstructionIterator);
};

// An embedded container with N elements of type T.  Used (with partial
// specialization for N=0) because embedded arrays cannot have size 0.
template<typename T, intptr_t N>
class EmbeddedArray {
 public:
  EmbeddedArray() : elements_() {}

  intptr_t GetLength() const { return N; }

  const T& operator[](intptr_t i) const {
    DCHECK_LT(i, GetLength());
    return elements_[i];
  }

  T& operator[](intptr_t i) {
    DCHECK_LT(i, GetLength());
    return elements_[i];
  }

  const T& At(intptr_t i) const {
    return (*this)[i];
  }

  void SetAt(intptr_t i, const T& val) {
    (*this)[i] = val;
  }

 private:
  T elements_[N];
};

template<typename T>
class EmbeddedArray<T, 0> {
 public:
  intptr_t length() const { return 0; }
  const T& operator[](intptr_t i) const {
    UNUSED(i);
    LOG(FATAL) << "Unreachable";
    UNREACHABLE();
  }
  T& operator[](intptr_t i) {
    UNUSED(i);
    LOG(FATAL) << "Unreachable";
    UNREACHABLE();
  }
};

template<intptr_t N>
class HTemplateInstruction: public HInstruction {
 public:
  HTemplateInstruction<N>(SideEffects side_effects)
      : HInstruction(side_effects), inputs_() {}
  virtual ~HTemplateInstruction() {}

  size_t InputCount() const OVERRIDE { return N; }

 protected:
  const HUserRecord<HInstruction*> InputRecordAt(size_t i) const OVERRIDE { return inputs_[i]; }

  void SetRawInputRecordAt(size_t i, const HUserRecord<HInstruction*>& input) OVERRIDE {
    inputs_[i] = input;
  }

 private:
  EmbeddedArray<HUserRecord<HInstruction*>, N> inputs_;

  friend class SsaBuilder;
};

template<intptr_t N>
class HExpression : public HTemplateInstruction<N> {
 public:
  HExpression<N>(Primitive::Type type, SideEffects side_effects)
      : HTemplateInstruction<N>(side_effects), type_(type) {}
  virtual ~HExpression() {}

  Primitive::Type GetType() const OVERRIDE { return type_; }

 protected:
  Primitive::Type type_;
};

// Represents dex's RETURN_VOID opcode. A HReturnVoid is a control flow
// instruction that branches to the exit block.
class HReturnVoid : public HTemplateInstruction<0> {
 public:
  HReturnVoid() : HTemplateInstruction(SideEffects::None()) {}

  bool IsControlFlow() const OVERRIDE { return true; }

  DECLARE_INSTRUCTION(ReturnVoid);

 private:
  DISALLOW_COPY_AND_ASSIGN(HReturnVoid);
};

// Represents dex's RETURN opcodes. A HReturn is a control flow
// instruction that branches to the exit block.
class HReturn : public HTemplateInstruction<1> {
 public:
  explicit HReturn(HInstruction* value) : HTemplateInstruction(SideEffects::None()) {
    SetRawInputAt(0, value);
  }

  bool IsControlFlow() const OVERRIDE { return true; }

  DECLARE_INSTRUCTION(Return);

 private:
  DISALLOW_COPY_AND_ASSIGN(HReturn);
};

// The exit instruction is the only instruction of the exit block.
// Instructions aborting the method (HThrow and HReturn) must branch to the
// exit block.
class HExit : public HTemplateInstruction<0> {
 public:
  HExit() : HTemplateInstruction(SideEffects::None()) {}

  bool IsControlFlow() const OVERRIDE { return true; }

  DECLARE_INSTRUCTION(Exit);

 private:
  DISALLOW_COPY_AND_ASSIGN(HExit);
};

// Jumps from one block to another.
class HGoto : public HTemplateInstruction<0> {
 public:
  HGoto() : HTemplateInstruction(SideEffects::None()) {}

  bool IsControlFlow() const OVERRIDE { return true; }

  HBasicBlock* GetSuccessor() const {
    return GetBlock()->GetSingleSuccessor();
  }

  DECLARE_INSTRUCTION(Goto);

 private:
  DISALLOW_COPY_AND_ASSIGN(HGoto);
};


// Conditional branch. A block ending with an HIf instruction must have
// two successors.
class HIf : public HTemplateInstruction<1> {
 public:
  explicit HIf(HInstruction* input) : HTemplateInstruction(SideEffects::None()) {
    SetRawInputAt(0, input);
  }

  bool IsControlFlow() const OVERRIDE { return true; }

  HBasicBlock* IfTrueSuccessor() const {
    return GetBlock()->GetSuccessors().Get(0);
  }

  HBasicBlock* IfFalseSuccessor() const {
    return GetBlock()->GetSuccessors().Get(1);
  }

  DECLARE_INSTRUCTION(If);

 private:
  DISALLOW_COPY_AND_ASSIGN(HIf);
};


// Abstract instruction which marks the beginning and/or end of a try block and
// links it to the respective exception handlers. Behaves the same as a Goto in
// non-exceptional control flow.
// Normal-flow successor is stored at index zero, exception handlers under
// higher indices in no particular order.
class HTryBoundary : public HTemplateInstruction<0> {
 public:
  enum BoundaryKind {
    kEntry,
    kExit,
  };

  explicit HTryBoundary(BoundaryKind kind)
      : HTemplateInstruction(SideEffects::None()), kind_(kind) {}

  bool IsControlFlow() const OVERRIDE { return true; }

  bool CanThrow() const OVERRIDE { return true; }

  // Returns the block's non-exceptional successor (index zero).
  HBasicBlock* GetNormalFlowSuccessor() const { return GetBlock()->GetSuccessors().Get(0); }

  // Returns whether `handler` is among its exception handlers (non-zero index
  // successors).
  bool HasExceptionHandler(HBasicBlock* handler) const {
    DCHECK(handler->IsCatchBlock());
    return GetBlock()->GetSuccessors().Contains(handler, /* start_from */ 1);
  }

  // Returns whether successor at index `idx` is an exception handler.
  bool IsExceptionalSuccessor(size_t idx) const {
    DCHECK_LT(idx, GetBlock()->GetSuccessors().Size());
    bool is_handler = (idx != 0);
    DCHECK(!is_handler || GetBlock()->GetSuccessors().Get(idx)->IsCatchBlock());
    return is_handler;
  }

  // If not present already, adds `handler` to its block's list of exception
  // handlers.
  void AddExceptionHandler(HBasicBlock* handler) {
    if (!HasExceptionHandler(handler)) {
      GetBlock()->AddSuccessor(handler);
    }
  }

  bool IsEntry() const { return kind_ == BoundaryKind::kEntry; }

  DECLARE_INSTRUCTION(TryBoundary);

 private:
  const BoundaryKind kind_;

  DISALLOW_COPY_AND_ASSIGN(HTryBoundary);
};


// Deoptimize to interpreter, upon checking a condition.
class HDeoptimize : public HTemplateInstruction<1> {
 public:
  HDeoptimize(HInstruction* cond, uint32_t dex_pc)
      : HTemplateInstruction(SideEffects::None()),
        dex_pc_(dex_pc) {
    SetRawInputAt(0, cond);
  }

  bool NeedsEnvironment() const OVERRIDE { return true; }
  bool CanThrow() const OVERRIDE { return true; }
  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  DECLARE_INSTRUCTION(Deoptimize);

 private:
  uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HDeoptimize);
};

// Represents the ArtMethod that was passed as a first argument to
// the method. It is used by instructions that depend on it, like
// instructions that work with the dex cache.
class HCurrentMethod : public HExpression<0> {
 public:
  explicit HCurrentMethod(Primitive::Type type) : HExpression(type, SideEffects::None()) {}

  DECLARE_INSTRUCTION(CurrentMethod);

 private:
  DISALLOW_COPY_AND_ASSIGN(HCurrentMethod);
};

class HUnaryOperation : public HExpression<1> {
 public:
  HUnaryOperation(Primitive::Type result_type, HInstruction* input)
      : HExpression(result_type, SideEffects::None()) {
    SetRawInputAt(0, input);
  }

  HInstruction* GetInput() const { return InputAt(0); }
  Primitive::Type GetResultType() const { return GetType(); }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  // Try to statically evaluate `operation` and return a HConstant
  // containing the result of this evaluation.  If `operation` cannot
  // be evaluated as a constant, return null.
  HConstant* TryStaticEvaluation() const;

  // Apply this operation to `x`.
  virtual int32_t Evaluate(int32_t x) const = 0;
  virtual int64_t Evaluate(int64_t x) const = 0;

  DECLARE_INSTRUCTION(UnaryOperation);

 private:
  DISALLOW_COPY_AND_ASSIGN(HUnaryOperation);
};

class HBinaryOperation : public HExpression<2> {
 public:
  HBinaryOperation(Primitive::Type result_type,
                   HInstruction* left,
                   HInstruction* right) : HExpression(result_type, SideEffects::None()) {
    SetRawInputAt(0, left);
    SetRawInputAt(1, right);
  }

  HInstruction* GetLeft() const { return InputAt(0); }
  HInstruction* GetRight() const { return InputAt(1); }
  Primitive::Type GetResultType() const { return GetType(); }

  virtual bool IsCommutative() const { return false; }

  // Put constant on the right.
  // Returns whether order is changed.
  bool OrderInputsWithConstantOnTheRight() {
    HInstruction* left = InputAt(0);
    HInstruction* right = InputAt(1);
    if (left->IsConstant() && !right->IsConstant()) {
      ReplaceInput(right, 0);
      ReplaceInput(left, 1);
      return true;
    }
    return false;
  }

  // Order inputs by instruction id, but favor constant on the right side.
  // This helps GVN for commutative ops.
  void OrderInputs() {
    DCHECK(IsCommutative());
    HInstruction* left = InputAt(0);
    HInstruction* right = InputAt(1);
    if (left == right || (!left->IsConstant() && right->IsConstant())) {
      return;
    }
    if (OrderInputsWithConstantOnTheRight()) {
      return;
    }
    // Order according to instruction id.
    if (left->GetId() > right->GetId()) {
      ReplaceInput(right, 0);
      ReplaceInput(left, 1);
    }
  }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  // Try to statically evaluate `operation` and return a HConstant
  // containing the result of this evaluation.  If `operation` cannot
  // be evaluated as a constant, return null.
  HConstant* TryStaticEvaluation() const;

  // Apply this operation to `x` and `y`.
  virtual int32_t Evaluate(int32_t x, int32_t y) const = 0;
  virtual int64_t Evaluate(int64_t x, int64_t y) const = 0;

  // Returns an input that can legally be used as the right input and is
  // constant, or null.
  HConstant* GetConstantRight() const;

  // If `GetConstantRight()` returns one of the input, this returns the other
  // one. Otherwise it returns null.
  HInstruction* GetLeastConstantLeft() const;

  DECLARE_INSTRUCTION(BinaryOperation);

 private:
  DISALLOW_COPY_AND_ASSIGN(HBinaryOperation);
};

class HCondition : public HBinaryOperation {
 public:
  HCondition(HInstruction* first, HInstruction* second)
      : HBinaryOperation(Primitive::kPrimBoolean, first, second),
        needs_materialization_(true) {}

  bool NeedsMaterialization() const { return needs_materialization_; }
  void ClearNeedsMaterialization() { needs_materialization_ = false; }

  // For code generation purposes, returns whether this instruction is just before
  // `instruction`, and disregard moves in between.
  bool IsBeforeWhenDisregardMoves(HInstruction* instruction) const;

  DECLARE_INSTRUCTION(Condition);

  virtual IfCondition GetCondition() const = 0;

 private:
  // For register allocation purposes, returns whether this instruction needs to be
  // materialized (that is, not just be in the processor flags).
  bool needs_materialization_;

  DISALLOW_COPY_AND_ASSIGN(HCondition);
};

// Instruction to check if two inputs are equal to each other.
class HEqual : public HCondition {
 public:
  HEqual(HInstruction* first, HInstruction* second)
      : HCondition(first, second) {}

  bool IsCommutative() const OVERRIDE { return true; }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x == y ? 1 : 0;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x == y ? 1 : 0;
  }

  DECLARE_INSTRUCTION(Equal);

  IfCondition GetCondition() const OVERRIDE {
    return kCondEQ;
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(HEqual);
};

class HNotEqual : public HCondition {
 public:
  HNotEqual(HInstruction* first, HInstruction* second)
      : HCondition(first, second) {}

  bool IsCommutative() const OVERRIDE { return true; }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x != y ? 1 : 0;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x != y ? 1 : 0;
  }

  DECLARE_INSTRUCTION(NotEqual);

  IfCondition GetCondition() const OVERRIDE {
    return kCondNE;
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(HNotEqual);
};

class HLessThan : public HCondition {
 public:
  HLessThan(HInstruction* first, HInstruction* second)
      : HCondition(first, second) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x < y ? 1 : 0;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x < y ? 1 : 0;
  }

  DECLARE_INSTRUCTION(LessThan);

  IfCondition GetCondition() const OVERRIDE {
    return kCondLT;
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(HLessThan);
};

class HLessThanOrEqual : public HCondition {
 public:
  HLessThanOrEqual(HInstruction* first, HInstruction* second)
      : HCondition(first, second) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x <= y ? 1 : 0;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x <= y ? 1 : 0;
  }

  DECLARE_INSTRUCTION(LessThanOrEqual);

  IfCondition GetCondition() const OVERRIDE {
    return kCondLE;
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(HLessThanOrEqual);
};

class HGreaterThan : public HCondition {
 public:
  HGreaterThan(HInstruction* first, HInstruction* second)
      : HCondition(first, second) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x > y ? 1 : 0;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x > y ? 1 : 0;
  }

  DECLARE_INSTRUCTION(GreaterThan);

  IfCondition GetCondition() const OVERRIDE {
    return kCondGT;
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(HGreaterThan);
};

class HGreaterThanOrEqual : public HCondition {
 public:
  HGreaterThanOrEqual(HInstruction* first, HInstruction* second)
      : HCondition(first, second) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x >= y ? 1 : 0;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x >= y ? 1 : 0;
  }

  DECLARE_INSTRUCTION(GreaterThanOrEqual);

  IfCondition GetCondition() const OVERRIDE {
    return kCondGE;
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(HGreaterThanOrEqual);
};


// Instruction to check how two inputs compare to each other.
// Result is 0 if input0 == input1, 1 if input0 > input1, or -1 if input0 < input1.
class HCompare : public HBinaryOperation {
 public:
  // The bias applies for floating point operations and indicates how NaN
  // comparisons are treated:
  enum Bias {
    kNoBias,  // bias is not applicable (i.e. for long operation)
    kGtBias,  // return 1 for NaN comparisons
    kLtBias,  // return -1 for NaN comparisons
  };

  HCompare(Primitive::Type type,
           HInstruction* first,
           HInstruction* second,
           Bias bias,
           uint32_t dex_pc)
      : HBinaryOperation(Primitive::kPrimInt, first, second), bias_(bias), dex_pc_(dex_pc) {
    DCHECK_EQ(type, first->GetType());
    DCHECK_EQ(type, second->GetType());
  }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return
      x == y ? 0 :
      x > y ? 1 :
      -1;
  }

  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return
      x == y ? 0 :
      x > y ? 1 :
      -1;
  }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    return bias_ == other->AsCompare()->bias_;
  }

  bool IsGtBias() { return bias_ == kGtBias; }

  uint32_t GetDexPc() const { return dex_pc_; }

  DECLARE_INSTRUCTION(Compare);

 private:
  const Bias bias_;
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HCompare);
};

// A local in the graph. Corresponds to a Dex register.
class HLocal : public HTemplateInstruction<0> {
 public:
  explicit HLocal(uint16_t reg_number)
      : HTemplateInstruction(SideEffects::None()), reg_number_(reg_number) {}

  DECLARE_INSTRUCTION(Local);

  uint16_t GetRegNumber() const { return reg_number_; }

 private:
  // The Dex register number.
  const uint16_t reg_number_;

  DISALLOW_COPY_AND_ASSIGN(HLocal);
};

// Load a given local. The local is an input of this instruction.
class HLoadLocal : public HExpression<1> {
 public:
  HLoadLocal(HLocal* local, Primitive::Type type)
      : HExpression(type, SideEffects::None()) {
    SetRawInputAt(0, local);
  }

  HLocal* GetLocal() const { return reinterpret_cast<HLocal*>(InputAt(0)); }

  DECLARE_INSTRUCTION(LoadLocal);

 private:
  DISALLOW_COPY_AND_ASSIGN(HLoadLocal);
};

// Store a value in a given local. This instruction has two inputs: the value
// and the local.
class HStoreLocal : public HTemplateInstruction<2> {
 public:
  HStoreLocal(HLocal* local, HInstruction* value) : HTemplateInstruction(SideEffects::None()) {
    SetRawInputAt(0, local);
    SetRawInputAt(1, value);
  }

  HLocal* GetLocal() const { return reinterpret_cast<HLocal*>(InputAt(0)); }

  DECLARE_INSTRUCTION(StoreLocal);

 private:
  DISALLOW_COPY_AND_ASSIGN(HStoreLocal);
};

class HConstant : public HExpression<0> {
 public:
  explicit HConstant(Primitive::Type type) : HExpression(type, SideEffects::None()) {}

  bool CanBeMoved() const OVERRIDE { return true; }

  virtual bool IsMinusOne() const { return false; }
  virtual bool IsZero() const { return false; }
  virtual bool IsOne() const { return false; }

  DECLARE_INSTRUCTION(Constant);

 private:
  DISALLOW_COPY_AND_ASSIGN(HConstant);
};

class HFloatConstant : public HConstant {
 public:
  float GetValue() const { return value_; }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    return bit_cast<uint32_t, float>(other->AsFloatConstant()->value_) ==
        bit_cast<uint32_t, float>(value_);
  }

  size_t ComputeHashCode() const OVERRIDE { return static_cast<size_t>(GetValue()); }

  bool IsMinusOne() const OVERRIDE {
    return bit_cast<uint32_t, float>(value_) == bit_cast<uint32_t, float>((-1.0f));
  }
  bool IsZero() const OVERRIDE {
    return value_ == 0.0f;
  }
  bool IsOne() const OVERRIDE {
    return bit_cast<uint32_t, float>(value_) == bit_cast<uint32_t, float>(1.0f);
  }
  bool IsNaN() const {
    return std::isnan(value_);
  }

  DECLARE_INSTRUCTION(FloatConstant);

 private:
  explicit HFloatConstant(float value) : HConstant(Primitive::kPrimFloat), value_(value) {}
  explicit HFloatConstant(int32_t value)
      : HConstant(Primitive::kPrimFloat), value_(bit_cast<float, int32_t>(value)) {}

  const float value_;

  // Only the SsaBuilder and HGraph can create floating-point constants.
  friend class SsaBuilder;
  friend class HGraph;
  DISALLOW_COPY_AND_ASSIGN(HFloatConstant);
};

class HDoubleConstant : public HConstant {
 public:
  double GetValue() const { return value_; }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    return bit_cast<uint64_t, double>(other->AsDoubleConstant()->value_) ==
        bit_cast<uint64_t, double>(value_);
  }

  size_t ComputeHashCode() const OVERRIDE { return static_cast<size_t>(GetValue()); }

  bool IsMinusOne() const OVERRIDE {
    return bit_cast<uint64_t, double>(value_) == bit_cast<uint64_t, double>((-1.0));
  }
  bool IsZero() const OVERRIDE {
    return value_ == 0.0;
  }
  bool IsOne() const OVERRIDE {
    return bit_cast<uint64_t, double>(value_) == bit_cast<uint64_t, double>(1.0);
  }
  bool IsNaN() const {
    return std::isnan(value_);
  }

  DECLARE_INSTRUCTION(DoubleConstant);

 private:
  explicit HDoubleConstant(double value) : HConstant(Primitive::kPrimDouble), value_(value) {}
  explicit HDoubleConstant(int64_t value)
      : HConstant(Primitive::kPrimDouble), value_(bit_cast<double, int64_t>(value)) {}

  const double value_;

  // Only the SsaBuilder and HGraph can create floating-point constants.
  friend class SsaBuilder;
  friend class HGraph;
  DISALLOW_COPY_AND_ASSIGN(HDoubleConstant);
};

class HNullConstant : public HConstant {
 public:
  bool InstructionDataEquals(HInstruction* other ATTRIBUTE_UNUSED) const OVERRIDE {
    return true;
  }

  size_t ComputeHashCode() const OVERRIDE { return 0; }

  DECLARE_INSTRUCTION(NullConstant);

 private:
  HNullConstant() : HConstant(Primitive::kPrimNot) {}

  friend class HGraph;
  DISALLOW_COPY_AND_ASSIGN(HNullConstant);
};

// Constants of the type int. Those can be from Dex instructions, or
// synthesized (for example with the if-eqz instruction).
class HIntConstant : public HConstant {
 public:
  int32_t GetValue() const { return value_; }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    return other->AsIntConstant()->value_ == value_;
  }

  size_t ComputeHashCode() const OVERRIDE { return GetValue(); }

  bool IsMinusOne() const OVERRIDE { return GetValue() == -1; }
  bool IsZero() const OVERRIDE { return GetValue() == 0; }
  bool IsOne() const OVERRIDE { return GetValue() == 1; }

  DECLARE_INSTRUCTION(IntConstant);

 private:
  explicit HIntConstant(int32_t value) : HConstant(Primitive::kPrimInt), value_(value) {}

  const int32_t value_;

  friend class HGraph;
  ART_FRIEND_TEST(GraphTest, InsertInstructionBefore);
  ART_FRIEND_TYPED_TEST(ParallelMoveTest, ConstantLast);
  DISALLOW_COPY_AND_ASSIGN(HIntConstant);
};

class HLongConstant : public HConstant {
 public:
  int64_t GetValue() const { return value_; }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    return other->AsLongConstant()->value_ == value_;
  }

  size_t ComputeHashCode() const OVERRIDE { return static_cast<size_t>(GetValue()); }

  bool IsMinusOne() const OVERRIDE { return GetValue() == -1; }
  bool IsZero() const OVERRIDE { return GetValue() == 0; }
  bool IsOne() const OVERRIDE { return GetValue() == 1; }

  DECLARE_INSTRUCTION(LongConstant);

 private:
  explicit HLongConstant(int64_t value) : HConstant(Primitive::kPrimLong), value_(value) {}

  const int64_t value_;

  friend class HGraph;
  DISALLOW_COPY_AND_ASSIGN(HLongConstant);
};

enum class Intrinsics {
#define OPTIMIZING_INTRINSICS(Name, IsStatic) k ## Name,
#include "intrinsics_list.h"
  kNone,
  INTRINSICS_LIST(OPTIMIZING_INTRINSICS)
#undef INTRINSICS_LIST
#undef OPTIMIZING_INTRINSICS
};
std::ostream& operator<<(std::ostream& os, const Intrinsics& intrinsic);

class HInvoke : public HInstruction {
 public:
  size_t InputCount() const OVERRIDE { return inputs_.Size(); }

  // Runtime needs to walk the stack, so Dex -> Dex calls need to
  // know their environment.
  bool NeedsEnvironment() const OVERRIDE { return true; }

  void SetArgumentAt(size_t index, HInstruction* argument) {
    SetRawInputAt(index, argument);
  }

  // Return the number of arguments.  This number can be lower than
  // the number of inputs returned by InputCount(), as some invoke
  // instructions (e.g. HInvokeStaticOrDirect) can have non-argument
  // inputs at the end of their list of inputs.
  uint32_t GetNumberOfArguments() const { return number_of_arguments_; }

  Primitive::Type GetType() const OVERRIDE { return return_type_; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  uint32_t GetDexMethodIndex() const { return dex_method_index_; }
  const DexFile& GetDexFile() const { return GetEnvironment()->GetDexFile(); }

  InvokeType GetOriginalInvokeType() const { return original_invoke_type_; }

  Intrinsics GetIntrinsic() const {
    return intrinsic_;
  }

  void SetIntrinsic(Intrinsics intrinsic) {
    intrinsic_ = intrinsic;
  }

  bool IsFromInlinedInvoke() const {
    return GetEnvironment()->GetParent() != nullptr;
  }

  bool CanThrow() const OVERRIDE { return true; }

  DECLARE_INSTRUCTION(Invoke);

 protected:
  HInvoke(ArenaAllocator* arena,
          uint32_t number_of_arguments,
          uint32_t number_of_other_inputs,
          Primitive::Type return_type,
          uint32_t dex_pc,
          uint32_t dex_method_index,
          InvokeType original_invoke_type)
    : HInstruction(SideEffects::All()),
      number_of_arguments_(number_of_arguments),
      inputs_(arena, number_of_arguments),
      return_type_(return_type),
      dex_pc_(dex_pc),
      dex_method_index_(dex_method_index),
      original_invoke_type_(original_invoke_type),
      intrinsic_(Intrinsics::kNone) {
    uint32_t number_of_inputs = number_of_arguments + number_of_other_inputs;
    inputs_.SetSize(number_of_inputs);
  }

  const HUserRecord<HInstruction*> InputRecordAt(size_t i) const OVERRIDE { return inputs_.Get(i); }
  void SetRawInputRecordAt(size_t index, const HUserRecord<HInstruction*>& input) OVERRIDE {
    inputs_.Put(index, input);
  }

  uint32_t number_of_arguments_;
  GrowableArray<HUserRecord<HInstruction*> > inputs_;
  const Primitive::Type return_type_;
  const uint32_t dex_pc_;
  const uint32_t dex_method_index_;
  const InvokeType original_invoke_type_;
  Intrinsics intrinsic_;

 private:
  DISALLOW_COPY_AND_ASSIGN(HInvoke);
};

class HInvokeStaticOrDirect : public HInvoke {
 public:
  // Requirements of this method call regarding the class
  // initialization (clinit) check of its declaring class.
  enum class ClinitCheckRequirement {
    kNone,      // Class already initialized.
    kExplicit,  // Static call having explicit clinit check as last input.
    kImplicit,  // Static call implicitly requiring a clinit check.
  };

  HInvokeStaticOrDirect(ArenaAllocator* arena,
                        uint32_t number_of_arguments,
                        Primitive::Type return_type,
                        uint32_t dex_pc,
                        uint32_t dex_method_index,
                        bool is_recursive,
                        int32_t string_init_offset,
                        InvokeType original_invoke_type,
                        InvokeType invoke_type,
                        ClinitCheckRequirement clinit_check_requirement)
      : HInvoke(arena,
                number_of_arguments,
                // There is one extra argument for the  HCurrentMethod node, and
                // potentially one other if the clinit check is explicit.
                clinit_check_requirement == ClinitCheckRequirement::kExplicit ? 2u : 1u,
                return_type,
                dex_pc,
                dex_method_index,
                original_invoke_type),
        invoke_type_(invoke_type),
        is_recursive_(is_recursive),
        clinit_check_requirement_(clinit_check_requirement),
        string_init_offset_(string_init_offset) {}

  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    UNUSED(obj);
    // We access the method via the dex cache so we can't do an implicit null check.
    // TODO: for intrinsics we can generate implicit null checks.
    return false;
  }

  InvokeType GetInvokeType() const { return invoke_type_; }
  bool IsRecursive() const { return is_recursive_; }
  bool NeedsDexCache() const OVERRIDE { return !IsRecursive(); }
  bool IsStringInit() const { return string_init_offset_ != 0; }
  int32_t GetStringInitOffset() const { return string_init_offset_; }
  uint32_t GetCurrentMethodInputIndex() const { return GetNumberOfArguments(); }

  // Is this instruction a call to a static method?
  bool IsStatic() const {
    return GetInvokeType() == kStatic;
  }

  // Remove the art::HLoadClass instruction set as last input by
  // art::PrepareForRegisterAllocation::VisitClinitCheck in lieu of
  // the initial art::HClinitCheck instruction (only relevant for
  // static calls with explicit clinit check).
  void RemoveLoadClassAsLastInput() {
    DCHECK(IsStaticWithExplicitClinitCheck());
    size_t last_input_index = InputCount() - 1;
    HInstruction* last_input = InputAt(last_input_index);
    DCHECK(last_input != nullptr);
    DCHECK(last_input->IsLoadClass()) << last_input->DebugName();
    RemoveAsUserOfInput(last_input_index);
    inputs_.DeleteAt(last_input_index);
    clinit_check_requirement_ = ClinitCheckRequirement::kImplicit;
    DCHECK(IsStaticWithImplicitClinitCheck());
  }

  // Is this a call to a static method whose declaring class has an
  // explicit intialization check in the graph?
  bool IsStaticWithExplicitClinitCheck() const {
    return IsStatic() && (clinit_check_requirement_ == ClinitCheckRequirement::kExplicit);
  }

  // Is this a call to a static method whose declaring class has an
  // implicit intialization check requirement?
  bool IsStaticWithImplicitClinitCheck() const {
    return IsStatic() && (clinit_check_requirement_ == ClinitCheckRequirement::kImplicit);
  }

  DECLARE_INSTRUCTION(InvokeStaticOrDirect);

 protected:
  const HUserRecord<HInstruction*> InputRecordAt(size_t i) const OVERRIDE {
    const HUserRecord<HInstruction*> input_record = HInvoke::InputRecordAt(i);
    if (kIsDebugBuild && IsStaticWithExplicitClinitCheck() && (i == InputCount() - 1)) {
      HInstruction* input = input_record.GetInstruction();
      // `input` is the last input of a static invoke marked as having
      // an explicit clinit check. It must either be:
      // - an art::HClinitCheck instruction, set by art::HGraphBuilder; or
      // - an art::HLoadClass instruction, set by art::PrepareForRegisterAllocation.
      DCHECK(input != nullptr);
      DCHECK(input->IsClinitCheck() || input->IsLoadClass()) << input->DebugName();
    }
    return input_record;
  }

 private:
  const InvokeType invoke_type_;
  const bool is_recursive_;
  ClinitCheckRequirement clinit_check_requirement_;
  // Thread entrypoint offset for string init method if this is a string init invoke.
  // Note that there are multiple string init methods, each having its own offset.
  int32_t string_init_offset_;

  DISALLOW_COPY_AND_ASSIGN(HInvokeStaticOrDirect);
};

class HInvokeVirtual : public HInvoke {
 public:
  HInvokeVirtual(ArenaAllocator* arena,
                 uint32_t number_of_arguments,
                 Primitive::Type return_type,
                 uint32_t dex_pc,
                 uint32_t dex_method_index,
                 uint32_t vtable_index)
      : HInvoke(arena, number_of_arguments, 0u, return_type, dex_pc, dex_method_index, kVirtual),
        vtable_index_(vtable_index) {}

  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    // TODO: Add implicit null checks in intrinsics.
    return (obj == InputAt(0)) && !GetLocations()->Intrinsified();
  }

  uint32_t GetVTableIndex() const { return vtable_index_; }

  DECLARE_INSTRUCTION(InvokeVirtual);

 private:
  const uint32_t vtable_index_;

  DISALLOW_COPY_AND_ASSIGN(HInvokeVirtual);
};

class HInvokeInterface : public HInvoke {
 public:
  HInvokeInterface(ArenaAllocator* arena,
                   uint32_t number_of_arguments,
                   Primitive::Type return_type,
                   uint32_t dex_pc,
                   uint32_t dex_method_index,
                   uint32_t imt_index)
      : HInvoke(arena, number_of_arguments, 0u, return_type, dex_pc, dex_method_index, kInterface),
        imt_index_(imt_index) {}

  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    // TODO: Add implicit null checks in intrinsics.
    return (obj == InputAt(0)) && !GetLocations()->Intrinsified();
  }

  uint32_t GetImtIndex() const { return imt_index_; }
  uint32_t GetDexMethodIndex() const { return dex_method_index_; }

  DECLARE_INSTRUCTION(InvokeInterface);

 private:
  const uint32_t imt_index_;

  DISALLOW_COPY_AND_ASSIGN(HInvokeInterface);
};

class HNewInstance : public HExpression<1> {
 public:
  HNewInstance(HCurrentMethod* current_method,
               uint32_t dex_pc,
               uint16_t type_index,
               const DexFile& dex_file,
               QuickEntrypointEnum entrypoint)
      : HExpression(Primitive::kPrimNot, SideEffects::None()),
        dex_pc_(dex_pc),
        type_index_(type_index),
        dex_file_(dex_file),
        entrypoint_(entrypoint) {
    SetRawInputAt(0, current_method);
  }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }
  uint16_t GetTypeIndex() const { return type_index_; }
  const DexFile& GetDexFile() const { return dex_file_; }

  // Calls runtime so needs an environment.
  bool NeedsEnvironment() const OVERRIDE { return true; }
  // It may throw when called on:
  //   - interfaces
  //   - abstract/innaccessible/unknown classes
  // TODO: optimize when possible.
  bool CanThrow() const OVERRIDE { return true; }

  bool CanBeNull() const OVERRIDE { return false; }

  QuickEntrypointEnum GetEntrypoint() const { return entrypoint_; }

  DECLARE_INSTRUCTION(NewInstance);

 private:
  const uint32_t dex_pc_;
  const uint16_t type_index_;
  const DexFile& dex_file_;
  const QuickEntrypointEnum entrypoint_;

  DISALLOW_COPY_AND_ASSIGN(HNewInstance);
};

class HNeg : public HUnaryOperation {
 public:
  explicit HNeg(Primitive::Type result_type, HInstruction* input)
      : HUnaryOperation(result_type, input) {}

  int32_t Evaluate(int32_t x) const OVERRIDE { return -x; }
  int64_t Evaluate(int64_t x) const OVERRIDE { return -x; }

  DECLARE_INSTRUCTION(Neg);

 private:
  DISALLOW_COPY_AND_ASSIGN(HNeg);
};

class HNewArray : public HExpression<2> {
 public:
  HNewArray(HInstruction* length,
            HCurrentMethod* current_method,
            uint32_t dex_pc,
            uint16_t type_index,
            const DexFile& dex_file,
            QuickEntrypointEnum entrypoint)
      : HExpression(Primitive::kPrimNot, SideEffects::None()),
        dex_pc_(dex_pc),
        type_index_(type_index),
        dex_file_(dex_file),
        entrypoint_(entrypoint) {
    SetRawInputAt(0, length);
    SetRawInputAt(1, current_method);
  }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }
  uint16_t GetTypeIndex() const { return type_index_; }
  const DexFile& GetDexFile() const { return dex_file_; }

  // Calls runtime so needs an environment.
  bool NeedsEnvironment() const OVERRIDE { return true; }

  // May throw NegativeArraySizeException, OutOfMemoryError, etc.
  bool CanThrow() const OVERRIDE { return true; }

  bool CanBeNull() const OVERRIDE { return false; }

  QuickEntrypointEnum GetEntrypoint() const { return entrypoint_; }

  DECLARE_INSTRUCTION(NewArray);

 private:
  const uint32_t dex_pc_;
  const uint16_t type_index_;
  const DexFile& dex_file_;
  const QuickEntrypointEnum entrypoint_;

  DISALLOW_COPY_AND_ASSIGN(HNewArray);
};

class HAdd : public HBinaryOperation {
 public:
  HAdd(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  bool IsCommutative() const OVERRIDE { return true; }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x + y;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x + y;
  }

  DECLARE_INSTRUCTION(Add);

 private:
  DISALLOW_COPY_AND_ASSIGN(HAdd);
};

class HSub : public HBinaryOperation {
 public:
  HSub(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    return x - y;
  }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    return x - y;
  }

  DECLARE_INSTRUCTION(Sub);

 private:
  DISALLOW_COPY_AND_ASSIGN(HSub);
};

class HMul : public HBinaryOperation {
 public:
  HMul(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  bool IsCommutative() const OVERRIDE { return true; }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE { return x * y; }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE { return x * y; }

  DECLARE_INSTRUCTION(Mul);

 private:
  DISALLOW_COPY_AND_ASSIGN(HMul);
};

class HDiv : public HBinaryOperation {
 public:
  HDiv(Primitive::Type result_type, HInstruction* left, HInstruction* right, uint32_t dex_pc)
      : HBinaryOperation(result_type, left, right), dex_pc_(dex_pc) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    // Our graph structure ensures we never have 0 for `y` during constant folding.
    DCHECK_NE(y, 0);
    // Special case -1 to avoid getting a SIGFPE on x86(_64).
    return (y == -1) ? -x : x / y;
  }

  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    DCHECK_NE(y, 0);
    // Special case -1 to avoid getting a SIGFPE on x86(_64).
    return (y == -1) ? -x : x / y;
  }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  DECLARE_INSTRUCTION(Div);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HDiv);
};

class HRem : public HBinaryOperation {
 public:
  HRem(Primitive::Type result_type, HInstruction* left, HInstruction* right, uint32_t dex_pc)
      : HBinaryOperation(result_type, left, right), dex_pc_(dex_pc) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    DCHECK_NE(y, 0);
    // Special case -1 to avoid getting a SIGFPE on x86(_64).
    return (y == -1) ? 0 : x % y;
  }

  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    DCHECK_NE(y, 0);
    // Special case -1 to avoid getting a SIGFPE on x86(_64).
    return (y == -1) ? 0 : x % y;
  }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  DECLARE_INSTRUCTION(Rem);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HRem);
};

class HDivZeroCheck : public HExpression<1> {
 public:
  HDivZeroCheck(HInstruction* value, uint32_t dex_pc)
      : HExpression(value->GetType(), SideEffects::None()), dex_pc_(dex_pc) {
    SetRawInputAt(0, value);
  }

  bool CanBeMoved() const OVERRIDE { return true; }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  bool NeedsEnvironment() const OVERRIDE { return true; }
  bool CanThrow() const OVERRIDE { return true; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  DECLARE_INSTRUCTION(DivZeroCheck);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HDivZeroCheck);
};

class HShl : public HBinaryOperation {
 public:
  HShl(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE { return x << (y & kMaxIntShiftValue); }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE { return x << (y & kMaxLongShiftValue); }

  DECLARE_INSTRUCTION(Shl);

 private:
  DISALLOW_COPY_AND_ASSIGN(HShl);
};

class HShr : public HBinaryOperation {
 public:
  HShr(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE { return x >> (y & kMaxIntShiftValue); }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE { return x >> (y & kMaxLongShiftValue); }

  DECLARE_INSTRUCTION(Shr);

 private:
  DISALLOW_COPY_AND_ASSIGN(HShr);
};

class HUShr : public HBinaryOperation {
 public:
  HUShr(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE {
    uint32_t ux = static_cast<uint32_t>(x);
    uint32_t uy = static_cast<uint32_t>(y) & kMaxIntShiftValue;
    return static_cast<int32_t>(ux >> uy);
  }

  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE {
    uint64_t ux = static_cast<uint64_t>(x);
    uint64_t uy = static_cast<uint64_t>(y) & kMaxLongShiftValue;
    return static_cast<int64_t>(ux >> uy);
  }

  DECLARE_INSTRUCTION(UShr);

 private:
  DISALLOW_COPY_AND_ASSIGN(HUShr);
};

class HAnd : public HBinaryOperation {
 public:
  HAnd(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  bool IsCommutative() const OVERRIDE { return true; }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE { return x & y; }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE { return x & y; }

  DECLARE_INSTRUCTION(And);

 private:
  DISALLOW_COPY_AND_ASSIGN(HAnd);
};

class HOr : public HBinaryOperation {
 public:
  HOr(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  bool IsCommutative() const OVERRIDE { return true; }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE { return x | y; }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE { return x | y; }

  DECLARE_INSTRUCTION(Or);

 private:
  DISALLOW_COPY_AND_ASSIGN(HOr);
};

class HXor : public HBinaryOperation {
 public:
  HXor(Primitive::Type result_type, HInstruction* left, HInstruction* right)
      : HBinaryOperation(result_type, left, right) {}

  bool IsCommutative() const OVERRIDE { return true; }

  int32_t Evaluate(int32_t x, int32_t y) const OVERRIDE { return x ^ y; }
  int64_t Evaluate(int64_t x, int64_t y) const OVERRIDE { return x ^ y; }

  DECLARE_INSTRUCTION(Xor);

 private:
  DISALLOW_COPY_AND_ASSIGN(HXor);
};

// The value of a parameter in this method. Its location depends on
// the calling convention.
class HParameterValue : public HExpression<0> {
 public:
  HParameterValue(uint8_t index, Primitive::Type parameter_type, bool is_this = false)
      : HExpression(parameter_type, SideEffects::None()), index_(index), is_this_(is_this) {}

  uint8_t GetIndex() const { return index_; }

  bool CanBeNull() const OVERRIDE { return !is_this_; }

  bool IsThis() const { return is_this_; }

  DECLARE_INSTRUCTION(ParameterValue);

 private:
  // The index of this parameter in the parameters list. Must be less
  // than HGraph::number_of_in_vregs_.
  const uint8_t index_;

  // Whether or not the parameter value corresponds to 'this' argument.
  const bool is_this_;

  DISALLOW_COPY_AND_ASSIGN(HParameterValue);
};

class HNot : public HUnaryOperation {
 public:
  explicit HNot(Primitive::Type result_type, HInstruction* input)
      : HUnaryOperation(result_type, input) {}

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  int32_t Evaluate(int32_t x) const OVERRIDE { return ~x; }
  int64_t Evaluate(int64_t x) const OVERRIDE { return ~x; }

  DECLARE_INSTRUCTION(Not);

 private:
  DISALLOW_COPY_AND_ASSIGN(HNot);
};

class HBooleanNot : public HUnaryOperation {
 public:
  explicit HBooleanNot(HInstruction* input)
      : HUnaryOperation(Primitive::Type::kPrimBoolean, input) {}

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  int32_t Evaluate(int32_t x) const OVERRIDE {
    DCHECK(IsUint<1>(x));
    return !x;
  }

  int64_t Evaluate(int64_t x ATTRIBUTE_UNUSED) const OVERRIDE {
    LOG(FATAL) << DebugName() << " cannot be used with 64-bit values";
    UNREACHABLE();
  }

  DECLARE_INSTRUCTION(BooleanNot);

 private:
  DISALLOW_COPY_AND_ASSIGN(HBooleanNot);
};

class HTypeConversion : public HExpression<1> {
 public:
  // Instantiate a type conversion of `input` to `result_type`.
  HTypeConversion(Primitive::Type result_type, HInstruction* input, uint32_t dex_pc)
      : HExpression(result_type, SideEffects::None()), dex_pc_(dex_pc) {
    SetRawInputAt(0, input);
    DCHECK_NE(input->GetType(), result_type);
  }

  HInstruction* GetInput() const { return InputAt(0); }
  Primitive::Type GetInputType() const { return GetInput()->GetType(); }
  Primitive::Type GetResultType() const { return GetType(); }

  // Required by the x86 and ARM code generators when producing calls
  // to the runtime.
  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other ATTRIBUTE_UNUSED) const OVERRIDE { return true; }

  // Try to statically evaluate the conversion and return a HConstant
  // containing the result.  If the input cannot be converted, return nullptr.
  HConstant* TryStaticEvaluation() const;

  DECLARE_INSTRUCTION(TypeConversion);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HTypeConversion);
};

static constexpr uint32_t kNoRegNumber = -1;

class HPhi : public HInstruction {
 public:
  HPhi(ArenaAllocator* arena, uint32_t reg_number, size_t number_of_inputs, Primitive::Type type)
      : HInstruction(SideEffects::None()),
        inputs_(arena, number_of_inputs),
        reg_number_(reg_number),
        type_(type),
        is_live_(false),
        can_be_null_(true) {
    inputs_.SetSize(number_of_inputs);
  }

  // Returns a type equivalent to the given `type`, but that a `HPhi` can hold.
  static Primitive::Type ToPhiType(Primitive::Type type) {
    switch (type) {
      case Primitive::kPrimBoolean:
      case Primitive::kPrimByte:
      case Primitive::kPrimShort:
      case Primitive::kPrimChar:
        return Primitive::kPrimInt;
      default:
        return type;
    }
  }

  size_t InputCount() const OVERRIDE { return inputs_.Size(); }

  void AddInput(HInstruction* input);
  void RemoveInputAt(size_t index);

  Primitive::Type GetType() const OVERRIDE { return type_; }
  void SetType(Primitive::Type type) { type_ = type; }

  bool CanBeNull() const OVERRIDE { return can_be_null_; }
  void SetCanBeNull(bool can_be_null) { can_be_null_ = can_be_null; }

  uint32_t GetRegNumber() const { return reg_number_; }

  void SetDead() { is_live_ = false; }
  void SetLive() { is_live_ = true; }
  bool IsDead() const { return !is_live_; }
  bool IsLive() const { return is_live_; }

  // Returns the next equivalent phi (starting from the current one) or null if there is none.
  // An equivalent phi is a phi having the same dex register and type.
  // It assumes that phis with the same dex register are adjacent.
  HPhi* GetNextEquivalentPhiWithSameType() {
    HInstruction* next = GetNext();
    while (next != nullptr && next->AsPhi()->GetRegNumber() == reg_number_) {
      if (next->GetType() == GetType()) {
        return next->AsPhi();
      }
      next = next->GetNext();
    }
    return nullptr;
  }

  DECLARE_INSTRUCTION(Phi);

 protected:
  const HUserRecord<HInstruction*> InputRecordAt(size_t i) const OVERRIDE { return inputs_.Get(i); }

  void SetRawInputRecordAt(size_t index, const HUserRecord<HInstruction*>& input) OVERRIDE {
    inputs_.Put(index, input);
  }

 private:
  GrowableArray<HUserRecord<HInstruction*> > inputs_;
  const uint32_t reg_number_;
  Primitive::Type type_;
  bool is_live_;
  bool can_be_null_;

  DISALLOW_COPY_AND_ASSIGN(HPhi);
};

class HNullCheck : public HExpression<1> {
 public:
  HNullCheck(HInstruction* value, uint32_t dex_pc)
      : HExpression(value->GetType(), SideEffects::None()), dex_pc_(dex_pc) {
    SetRawInputAt(0, value);
  }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  bool NeedsEnvironment() const OVERRIDE { return true; }

  bool CanThrow() const OVERRIDE { return true; }

  bool CanBeNull() const OVERRIDE { return false; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  DECLARE_INSTRUCTION(NullCheck);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HNullCheck);
};

class FieldInfo : public ValueObject {
 public:
  FieldInfo(MemberOffset field_offset,
            Primitive::Type field_type,
            bool is_volatile,
            uint32_t index,
            const DexFile& dex_file)
      : field_offset_(field_offset),
        field_type_(field_type),
        is_volatile_(is_volatile),
        index_(index),
        dex_file_(dex_file) {}

  MemberOffset GetFieldOffset() const { return field_offset_; }
  Primitive::Type GetFieldType() const { return field_type_; }
  uint32_t GetFieldIndex() const { return index_; }
  const DexFile& GetDexFile() const { return dex_file_; }
  bool IsVolatile() const { return is_volatile_; }

 private:
  const MemberOffset field_offset_;
  const Primitive::Type field_type_;
  const bool is_volatile_;
  uint32_t index_;
  const DexFile& dex_file_;
};

class HInstanceFieldGet : public HExpression<1> {
 public:
  HInstanceFieldGet(HInstruction* value,
                    Primitive::Type field_type,
                    MemberOffset field_offset,
                    bool is_volatile,
                    uint32_t field_idx,
                    const DexFile& dex_file)
      : HExpression(field_type, SideEffects::DependsOnSomething()),
        field_info_(field_offset, field_type, is_volatile, field_idx, dex_file) {
    SetRawInputAt(0, value);
  }

  bool CanBeMoved() const OVERRIDE { return !IsVolatile(); }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    HInstanceFieldGet* other_get = other->AsInstanceFieldGet();
    return GetFieldOffset().SizeValue() == other_get->GetFieldOffset().SizeValue();
  }

  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    return (obj == InputAt(0)) && GetFieldOffset().Uint32Value() < kPageSize;
  }

  size_t ComputeHashCode() const OVERRIDE {
    return (HInstruction::ComputeHashCode() << 7) | GetFieldOffset().SizeValue();
  }

  const FieldInfo& GetFieldInfo() const { return field_info_; }
  MemberOffset GetFieldOffset() const { return field_info_.GetFieldOffset(); }
  Primitive::Type GetFieldType() const { return field_info_.GetFieldType(); }
  bool IsVolatile() const { return field_info_.IsVolatile(); }

  DECLARE_INSTRUCTION(InstanceFieldGet);

 private:
  const FieldInfo field_info_;

  DISALLOW_COPY_AND_ASSIGN(HInstanceFieldGet);
};

class HInstanceFieldSet : public HTemplateInstruction<2> {
 public:
  HInstanceFieldSet(HInstruction* object,
                    HInstruction* value,
                    Primitive::Type field_type,
                    MemberOffset field_offset,
                    bool is_volatile,
                    uint32_t field_idx,
                    const DexFile& dex_file)
      : HTemplateInstruction(SideEffects::ChangesSomething()),
        field_info_(field_offset, field_type, is_volatile, field_idx, dex_file),
        value_can_be_null_(true) {
    SetRawInputAt(0, object);
    SetRawInputAt(1, value);
  }

  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    return (obj == InputAt(0)) && GetFieldOffset().Uint32Value() < kPageSize;
  }

  const FieldInfo& GetFieldInfo() const { return field_info_; }
  MemberOffset GetFieldOffset() const { return field_info_.GetFieldOffset(); }
  Primitive::Type GetFieldType() const { return field_info_.GetFieldType(); }
  bool IsVolatile() const { return field_info_.IsVolatile(); }
  HInstruction* GetValue() const { return InputAt(1); }
  bool GetValueCanBeNull() const { return value_can_be_null_; }
  void ClearValueCanBeNull() { value_can_be_null_ = false; }

  DECLARE_INSTRUCTION(InstanceFieldSet);

 private:
  const FieldInfo field_info_;
  bool value_can_be_null_;

  DISALLOW_COPY_AND_ASSIGN(HInstanceFieldSet);
};

class HArrayGet : public HExpression<2> {
 public:
  HArrayGet(HInstruction* array, HInstruction* index, Primitive::Type type)
      : HExpression(type, SideEffects::DependsOnSomething()) {
    SetRawInputAt(0, array);
    SetRawInputAt(1, index);
  }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }
  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    UNUSED(obj);
    // TODO: We can be smarter here.
    // Currently, the array access is always preceded by an ArrayLength or a NullCheck
    // which generates the implicit null check. There are cases when these can be removed
    // to produce better code. If we ever add optimizations to do so we should allow an
    // implicit check here (as long as the address falls in the first page).
    return false;
  }

  void SetType(Primitive::Type type) { type_ = type; }

  HInstruction* GetArray() const { return InputAt(0); }
  HInstruction* GetIndex() const { return InputAt(1); }

  DECLARE_INSTRUCTION(ArrayGet);

 private:
  DISALLOW_COPY_AND_ASSIGN(HArrayGet);
};

class HArraySet : public HTemplateInstruction<3> {
 public:
  HArraySet(HInstruction* array,
            HInstruction* index,
            HInstruction* value,
            Primitive::Type expected_component_type,
            uint32_t dex_pc)
      : HTemplateInstruction(SideEffects::ChangesSomething()),
        dex_pc_(dex_pc),
        expected_component_type_(expected_component_type),
        needs_type_check_(value->GetType() == Primitive::kPrimNot),
        value_can_be_null_(true) {
    SetRawInputAt(0, array);
    SetRawInputAt(1, index);
    SetRawInputAt(2, value);
  }

  bool NeedsEnvironment() const OVERRIDE {
    // We currently always call a runtime method to catch array store
    // exceptions.
    return needs_type_check_;
  }

  // Can throw ArrayStoreException.
  bool CanThrow() const OVERRIDE { return needs_type_check_; }

  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    UNUSED(obj);
    // TODO: Same as for ArrayGet.
    return false;
  }

  void ClearNeedsTypeCheck() {
    needs_type_check_ = false;
  }

  void ClearValueCanBeNull() {
    value_can_be_null_ = false;
  }

  bool GetValueCanBeNull() const { return value_can_be_null_; }
  bool NeedsTypeCheck() const { return needs_type_check_; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  HInstruction* GetArray() const { return InputAt(0); }
  HInstruction* GetIndex() const { return InputAt(1); }
  HInstruction* GetValue() const { return InputAt(2); }

  Primitive::Type GetComponentType() const {
    // The Dex format does not type floating point index operations. Since the
    // `expected_component_type_` is set during building and can therefore not
    // be correct, we also check what is the value type. If it is a floating
    // point type, we must use that type.
    Primitive::Type value_type = GetValue()->GetType();
    return ((value_type == Primitive::kPrimFloat) || (value_type == Primitive::kPrimDouble))
        ? value_type
        : expected_component_type_;
  }

  DECLARE_INSTRUCTION(ArraySet);

 private:
  const uint32_t dex_pc_;
  const Primitive::Type expected_component_type_;
  bool needs_type_check_;
  bool value_can_be_null_;

  DISALLOW_COPY_AND_ASSIGN(HArraySet);
};

class HArrayLength : public HExpression<1> {
 public:
  explicit HArrayLength(HInstruction* array)
      : HExpression(Primitive::kPrimInt, SideEffects::None()) {
    // Note that arrays do not change length, so the instruction does not
    // depend on any write.
    SetRawInputAt(0, array);
  }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }
  bool CanDoImplicitNullCheckOn(HInstruction* obj) const OVERRIDE {
    return obj == InputAt(0);
  }

  DECLARE_INSTRUCTION(ArrayLength);

 private:
  DISALLOW_COPY_AND_ASSIGN(HArrayLength);
};

class HBoundsCheck : public HExpression<2> {
 public:
  HBoundsCheck(HInstruction* index, HInstruction* length, uint32_t dex_pc)
      : HExpression(index->GetType(), SideEffects::None()), dex_pc_(dex_pc) {
    DCHECK(index->GetType() == Primitive::kPrimInt);
    SetRawInputAt(0, index);
    SetRawInputAt(1, length);
  }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  bool NeedsEnvironment() const OVERRIDE { return true; }

  bool CanThrow() const OVERRIDE { return true; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  DECLARE_INSTRUCTION(BoundsCheck);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HBoundsCheck);
};

/**
 * Some DEX instructions are folded into multiple HInstructions that need
 * to stay live until the last HInstruction. This class
 * is used as a marker for the baseline compiler to ensure its preceding
 * HInstruction stays live. `index` represents the stack location index of the
 * instruction (the actual offset is computed as index * vreg_size).
 */
class HTemporary : public HTemplateInstruction<0> {
 public:
  explicit HTemporary(size_t index) : HTemplateInstruction(SideEffects::None()), index_(index) {}

  size_t GetIndex() const { return index_; }

  Primitive::Type GetType() const OVERRIDE {
    // The previous instruction is the one that will be stored in the temporary location.
    DCHECK(GetPrevious() != nullptr);
    return GetPrevious()->GetType();
  }

  DECLARE_INSTRUCTION(Temporary);

 private:
  const size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HTemporary);
};

class HSuspendCheck : public HTemplateInstruction<0> {
 public:
  explicit HSuspendCheck(uint32_t dex_pc)
      : HTemplateInstruction(SideEffects::None()), dex_pc_(dex_pc), slow_path_(nullptr) {}

  bool NeedsEnvironment() const OVERRIDE {
    return true;
  }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }
  void SetSlowPath(SlowPathCode* slow_path) { slow_path_ = slow_path; }
  SlowPathCode* GetSlowPath() const { return slow_path_; }

  DECLARE_INSTRUCTION(SuspendCheck);

 private:
  const uint32_t dex_pc_;

  // Only used for code generation, in order to share the same slow path between back edges
  // of a same loop.
  SlowPathCode* slow_path_;

  DISALLOW_COPY_AND_ASSIGN(HSuspendCheck);
};

/**
 * Instruction to load a Class object.
 */
class HLoadClass : public HExpression<1> {
 public:
  HLoadClass(HCurrentMethod* current_method,
             uint16_t type_index,
             const DexFile& dex_file,
             bool is_referrers_class,
             uint32_t dex_pc)
      : HExpression(Primitive::kPrimNot, SideEffects::None()),
        type_index_(type_index),
        dex_file_(dex_file),
        is_referrers_class_(is_referrers_class),
        dex_pc_(dex_pc),
        generate_clinit_check_(false),
        loaded_class_rti_(ReferenceTypeInfo::CreateTop(/* is_exact */ false)) {
    SetRawInputAt(0, current_method);
  }

  bool CanBeMoved() const OVERRIDE { return true; }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    return other->AsLoadClass()->type_index_ == type_index_;
  }

  size_t ComputeHashCode() const OVERRIDE { return type_index_; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }
  uint16_t GetTypeIndex() const { return type_index_; }
  bool IsReferrersClass() const { return is_referrers_class_; }

  bool NeedsEnvironment() const OVERRIDE {
    // Will call runtime and load the class if the class is not loaded yet.
    // TODO: finer grain decision.
    return !is_referrers_class_;
  }

  bool MustGenerateClinitCheck() const {
    return generate_clinit_check_;
  }

  void SetMustGenerateClinitCheck(bool generate_clinit_check) {
    generate_clinit_check_ = generate_clinit_check;
  }

  bool CanCallRuntime() const {
    return MustGenerateClinitCheck() || !is_referrers_class_;
  }

  bool CanThrow() const OVERRIDE {
    // May call runtime and and therefore can throw.
    // TODO: finer grain decision.
    return CanCallRuntime();
  }

  ReferenceTypeInfo GetLoadedClassRTI() {
    return loaded_class_rti_;
  }

  void SetLoadedClassRTI(ReferenceTypeInfo rti) {
    // Make sure we only set exact types (the loaded class should never be merged).
    DCHECK(rti.IsExact());
    loaded_class_rti_ = rti;
  }

  bool IsResolved() {
    return loaded_class_rti_.IsExact();
  }

  const DexFile& GetDexFile() { return dex_file_; }

  bool NeedsDexCache() const OVERRIDE { return !is_referrers_class_; }

  DECLARE_INSTRUCTION(LoadClass);

 private:
  const uint16_t type_index_;
  const DexFile& dex_file_;
  const bool is_referrers_class_;
  const uint32_t dex_pc_;
  // Whether this instruction must generate the initialization check.
  // Used for code generation.
  bool generate_clinit_check_;

  ReferenceTypeInfo loaded_class_rti_;

  DISALLOW_COPY_AND_ASSIGN(HLoadClass);
};

class HLoadString : public HExpression<1> {
 public:
  HLoadString(HCurrentMethod* current_method, uint32_t string_index, uint32_t dex_pc)
      : HExpression(Primitive::kPrimNot, SideEffects::None()),
        string_index_(string_index),
        dex_pc_(dex_pc) {
    SetRawInputAt(0, current_method);
  }

  bool CanBeMoved() const OVERRIDE { return true; }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    return other->AsLoadString()->string_index_ == string_index_;
  }

  size_t ComputeHashCode() const OVERRIDE { return string_index_; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }
  uint32_t GetStringIndex() const { return string_index_; }

  // TODO: Can we deopt or debug when we resolve a string?
  bool NeedsEnvironment() const OVERRIDE { return false; }
  bool NeedsDexCache() const OVERRIDE { return true; }

  DECLARE_INSTRUCTION(LoadString);

 private:
  const uint32_t string_index_;
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HLoadString);
};

/**
 * Performs an initialization check on its Class object input.
 */
class HClinitCheck : public HExpression<1> {
 public:
  explicit HClinitCheck(HLoadClass* constant, uint32_t dex_pc)
      : HExpression(Primitive::kPrimNot, SideEffects::ChangesSomething()),
        dex_pc_(dex_pc) {
    SetRawInputAt(0, constant);
  }

  bool CanBeMoved() const OVERRIDE { return true; }
  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    UNUSED(other);
    return true;
  }

  bool NeedsEnvironment() const OVERRIDE {
    // May call runtime to initialize the class.
    return true;
  }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  HLoadClass* GetLoadClass() const { return InputAt(0)->AsLoadClass(); }

  DECLARE_INSTRUCTION(ClinitCheck);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HClinitCheck);
};

class HStaticFieldGet : public HExpression<1> {
 public:
  HStaticFieldGet(HInstruction* cls,
                  Primitive::Type field_type,
                  MemberOffset field_offset,
                  bool is_volatile,
                  uint32_t field_idx,
                  const DexFile& dex_file)
      : HExpression(field_type, SideEffects::DependsOnSomething()),
        field_info_(field_offset, field_type, is_volatile, field_idx, dex_file) {
    SetRawInputAt(0, cls);
  }


  bool CanBeMoved() const OVERRIDE { return !IsVolatile(); }

  bool InstructionDataEquals(HInstruction* other) const OVERRIDE {
    HStaticFieldGet* other_get = other->AsStaticFieldGet();
    return GetFieldOffset().SizeValue() == other_get->GetFieldOffset().SizeValue();
  }

  size_t ComputeHashCode() const OVERRIDE {
    return (HInstruction::ComputeHashCode() << 7) | GetFieldOffset().SizeValue();
  }

  const FieldInfo& GetFieldInfo() const { return field_info_; }
  MemberOffset GetFieldOffset() const { return field_info_.GetFieldOffset(); }
  Primitive::Type GetFieldType() const { return field_info_.GetFieldType(); }
  bool IsVolatile() const { return field_info_.IsVolatile(); }

  DECLARE_INSTRUCTION(StaticFieldGet);

 private:
  const FieldInfo field_info_;

  DISALLOW_COPY_AND_ASSIGN(HStaticFieldGet);
};

class HStaticFieldSet : public HTemplateInstruction<2> {
 public:
  HStaticFieldSet(HInstruction* cls,
                  HInstruction* value,
                  Primitive::Type field_type,
                  MemberOffset field_offset,
                  bool is_volatile,
                  uint32_t field_idx,
                  const DexFile& dex_file)
      : HTemplateInstruction(SideEffects::ChangesSomething()),
        field_info_(field_offset, field_type, is_volatile, field_idx, dex_file),
        value_can_be_null_(true) {
    SetRawInputAt(0, cls);
    SetRawInputAt(1, value);
  }

  const FieldInfo& GetFieldInfo() const { return field_info_; }
  MemberOffset GetFieldOffset() const { return field_info_.GetFieldOffset(); }
  Primitive::Type GetFieldType() const { return field_info_.GetFieldType(); }
  bool IsVolatile() const { return field_info_.IsVolatile(); }

  HInstruction* GetValue() const { return InputAt(1); }
  bool GetValueCanBeNull() const { return value_can_be_null_; }
  void ClearValueCanBeNull() { value_can_be_null_ = false; }

  DECLARE_INSTRUCTION(StaticFieldSet);

 private:
  const FieldInfo field_info_;
  bool value_can_be_null_;

  DISALLOW_COPY_AND_ASSIGN(HStaticFieldSet);
};

// Implement the move-exception DEX instruction.
class HLoadException : public HExpression<0> {
 public:
  HLoadException() : HExpression(Primitive::kPrimNot, SideEffects::None()) {}

  DECLARE_INSTRUCTION(LoadException);

 private:
  DISALLOW_COPY_AND_ASSIGN(HLoadException);
};

class HThrow : public HTemplateInstruction<1> {
 public:
  HThrow(HInstruction* exception, uint32_t dex_pc)
      : HTemplateInstruction(SideEffects::None()), dex_pc_(dex_pc) {
    SetRawInputAt(0, exception);
  }

  bool IsControlFlow() const OVERRIDE { return true; }

  bool NeedsEnvironment() const OVERRIDE { return true; }

  bool CanThrow() const OVERRIDE { return true; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  DECLARE_INSTRUCTION(Throw);

 private:
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HThrow);
};

class HInstanceOf : public HExpression<2> {
 public:
  HInstanceOf(HInstruction* object,
              HLoadClass* constant,
              bool class_is_final,
              uint32_t dex_pc)
      : HExpression(Primitive::kPrimBoolean, SideEffects::None()),
        class_is_final_(class_is_final),
        must_do_null_check_(true),
        dex_pc_(dex_pc) {
    SetRawInputAt(0, object);
    SetRawInputAt(1, constant);
  }

  bool CanBeMoved() const OVERRIDE { return true; }

  bool InstructionDataEquals(HInstruction* other ATTRIBUTE_UNUSED) const OVERRIDE {
    return true;
  }

  bool NeedsEnvironment() const OVERRIDE {
    return false;
  }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  bool IsClassFinal() const { return class_is_final_; }

  // Used only in code generation.
  bool MustDoNullCheck() const { return must_do_null_check_; }
  void ClearMustDoNullCheck() { must_do_null_check_ = false; }

  DECLARE_INSTRUCTION(InstanceOf);

 private:
  const bool class_is_final_;
  bool must_do_null_check_;
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HInstanceOf);
};

class HBoundType : public HExpression<1> {
 public:
  HBoundType(HInstruction* input, ReferenceTypeInfo bound_type)
      : HExpression(Primitive::kPrimNot, SideEffects::None()),
        bound_type_(bound_type) {
    DCHECK_EQ(input->GetType(), Primitive::kPrimNot);
    SetRawInputAt(0, input);
  }

  const ReferenceTypeInfo& GetBoundType() const { return bound_type_; }

  bool CanBeNull() const OVERRIDE {
    // `null instanceof ClassX` always return false so we can't be null.
    return false;
  }

  DECLARE_INSTRUCTION(BoundType);

 private:
  // Encodes the most upper class that this instruction can have. In other words
  // it is always the case that GetBoundType().IsSupertypeOf(GetReferenceType()).
  // It is used to bound the type in cases like `if (x instanceof ClassX) {}`
  const ReferenceTypeInfo bound_type_;

  DISALLOW_COPY_AND_ASSIGN(HBoundType);
};

class HCheckCast : public HTemplateInstruction<2> {
 public:
  HCheckCast(HInstruction* object,
             HLoadClass* constant,
             bool class_is_final,
             uint32_t dex_pc)
      : HTemplateInstruction(SideEffects::None()),
        class_is_final_(class_is_final),
        must_do_null_check_(true),
        dex_pc_(dex_pc) {
    SetRawInputAt(0, object);
    SetRawInputAt(1, constant);
  }

  bool CanBeMoved() const OVERRIDE { return true; }

  bool InstructionDataEquals(HInstruction* other ATTRIBUTE_UNUSED) const OVERRIDE {
    return true;
  }

  bool NeedsEnvironment() const OVERRIDE {
    // Instruction may throw a CheckCastError.
    return true;
  }

  bool CanThrow() const OVERRIDE { return true; }

  bool MustDoNullCheck() const { return must_do_null_check_; }
  void ClearMustDoNullCheck() { must_do_null_check_ = false; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  bool IsClassFinal() const { return class_is_final_; }

  DECLARE_INSTRUCTION(CheckCast);

 private:
  const bool class_is_final_;
  bool must_do_null_check_;
  const uint32_t dex_pc_;

  DISALLOW_COPY_AND_ASSIGN(HCheckCast);
};

class HMemoryBarrier : public HTemplateInstruction<0> {
 public:
  explicit HMemoryBarrier(MemBarrierKind barrier_kind)
      : HTemplateInstruction(SideEffects::None()),
        barrier_kind_(barrier_kind) {}

  MemBarrierKind GetBarrierKind() { return barrier_kind_; }

  DECLARE_INSTRUCTION(MemoryBarrier);

 private:
  const MemBarrierKind barrier_kind_;

  DISALLOW_COPY_AND_ASSIGN(HMemoryBarrier);
};

class HMonitorOperation : public HTemplateInstruction<1> {
 public:
  enum OperationKind {
    kEnter,
    kExit,
  };

  HMonitorOperation(HInstruction* object, OperationKind kind, uint32_t dex_pc)
    : HTemplateInstruction(SideEffects::None()), kind_(kind), dex_pc_(dex_pc) {
    SetRawInputAt(0, object);
  }

  // Instruction may throw a Java exception, so we need an environment.
  bool NeedsEnvironment() const OVERRIDE { return true; }
  bool CanThrow() const OVERRIDE { return true; }

  uint32_t GetDexPc() const OVERRIDE { return dex_pc_; }

  bool IsEnter() const { return kind_ == kEnter; }

  DECLARE_INSTRUCTION(MonitorOperation);

 private:
  const OperationKind kind_;
  const uint32_t dex_pc_;

 private:
  DISALLOW_COPY_AND_ASSIGN(HMonitorOperation);
};

class MoveOperands : public ArenaObject<kArenaAllocMisc> {
 public:
  MoveOperands(Location source,
               Location destination,
               Primitive::Type type,
               HInstruction* instruction)
      : source_(source), destination_(destination), type_(type), instruction_(instruction) {}

  Location GetSource() const { return source_; }
  Location GetDestination() const { return destination_; }

  void SetSource(Location value) { source_ = value; }
  void SetDestination(Location value) { destination_ = value; }

  // The parallel move resolver marks moves as "in-progress" by clearing the
  // destination (but not the source).
  Location MarkPending() {
    DCHECK(!IsPending());
    Location dest = destination_;
    destination_ = Location::NoLocation();
    return dest;
  }

  void ClearPending(Location dest) {
    DCHECK(IsPending());
    destination_ = dest;
  }

  bool IsPending() const {
    DCHECK(!source_.IsInvalid() || destination_.IsInvalid());
    return destination_.IsInvalid() && !source_.IsInvalid();
  }

  // True if this blocks a move from the given location.
  bool Blocks(Location loc) const {
    return !IsEliminated() && source_.OverlapsWith(loc);
  }

  // A move is redundant if it's been eliminated, if its source and
  // destination are the same, or if its destination is unneeded.
  bool IsRedundant() const {
    return IsEliminated() || destination_.IsInvalid() || source_.Equals(destination_);
  }

  // We clear both operands to indicate move that's been eliminated.
  void Eliminate() {
    source_ = destination_ = Location::NoLocation();
  }

  bool IsEliminated() const {
    DCHECK(!source_.IsInvalid() || destination_.IsInvalid());
    return source_.IsInvalid();
  }

  Primitive::Type GetType() const { return type_; }

  bool Is64BitMove() const {
    return Primitive::Is64BitType(type_);
  }

  HInstruction* GetInstruction() const { return instruction_; }

 private:
  Location source_;
  Location destination_;
  // The type this move is for.
  Primitive::Type type_;
  // The instruction this move is assocatied with. Null when this move is
  // for moving an input in the expected locations of user (including a phi user).
  // This is only used in debug mode, to ensure we do not connect interval siblings
  // in the same parallel move.
  HInstruction* instruction_;
};

static constexpr size_t kDefaultNumberOfMoves = 4;

class HParallelMove : public HTemplateInstruction<0> {
 public:
  explicit HParallelMove(ArenaAllocator* arena)
      : HTemplateInstruction(SideEffects::None()), moves_(arena, kDefaultNumberOfMoves) {}

  void AddMove(Location source,
               Location destination,
               Primitive::Type type,
               HInstruction* instruction) {
    DCHECK(source.IsValid());
    DCHECK(destination.IsValid());
    if (kIsDebugBuild) {
      if (instruction != nullptr) {
        for (size_t i = 0, e = moves_.Size(); i < e; ++i) {
          if (moves_.Get(i).GetInstruction() == instruction) {
            // Special case the situation where the move is for the spill slot
            // of the instruction.
            if ((GetPrevious() == instruction)
                || ((GetPrevious() == nullptr)
                    && instruction->IsPhi()
                    && instruction->GetBlock() == GetBlock())) {
              DCHECK_NE(destination.GetKind(), moves_.Get(i).GetDestination().GetKind())
                  << "Doing parallel moves for the same instruction.";
            } else {
              DCHECK(false) << "Doing parallel moves for the same instruction.";
            }
          }
        }
      }
      for (size_t i = 0, e = moves_.Size(); i < e; ++i) {
        DCHECK(!destination.OverlapsWith(moves_.Get(i).GetDestination()))
            << "Overlapped destination for two moves in a parallel move: "
            << moves_.Get(i).GetSource() << " ==> " << moves_.Get(i).GetDestination() << " and "
            << source << " ==> " << destination;
      }
    }
    moves_.Add(MoveOperands(source, destination, type, instruction));
  }

  MoveOperands* MoveOperandsAt(size_t index) const {
    return moves_.GetRawStorage() + index;
  }

  size_t NumMoves() const { return moves_.Size(); }

  DECLARE_INSTRUCTION(ParallelMove);

 private:
  GrowableArray<MoveOperands> moves_;

  DISALLOW_COPY_AND_ASSIGN(HParallelMove);
};

class HGraphVisitor : public ValueObject {
 public:
  explicit HGraphVisitor(HGraph* graph) : graph_(graph) {}
  virtual ~HGraphVisitor() {}

  virtual void VisitInstruction(HInstruction* instruction) { UNUSED(instruction); }
  virtual void VisitBasicBlock(HBasicBlock* block);

  // Visit the graph following basic block insertion order.
  void VisitInsertionOrder();

  // Visit the graph following dominator tree reverse post-order.
  void VisitReversePostOrder();

  HGraph* GetGraph() const { return graph_; }

  // Visit functions for instruction classes.
#define DECLARE_VISIT_INSTRUCTION(name, super)                                        \
  virtual void Visit##name(H##name* instr) { VisitInstruction(instr); }

  FOR_EACH_INSTRUCTION(DECLARE_VISIT_INSTRUCTION)

#undef DECLARE_VISIT_INSTRUCTION

 private:
  HGraph* const graph_;

  DISALLOW_COPY_AND_ASSIGN(HGraphVisitor);
};

class HGraphDelegateVisitor : public HGraphVisitor {
 public:
  explicit HGraphDelegateVisitor(HGraph* graph) : HGraphVisitor(graph) {}
  virtual ~HGraphDelegateVisitor() {}

  // Visit functions that delegate to to super class.
#define DECLARE_VISIT_INSTRUCTION(name, super)                                        \
  void Visit##name(H##name* instr) OVERRIDE { Visit##super(instr); }

  FOR_EACH_INSTRUCTION(DECLARE_VISIT_INSTRUCTION)

#undef DECLARE_VISIT_INSTRUCTION

 private:
  DISALLOW_COPY_AND_ASSIGN(HGraphDelegateVisitor);
};

class HInsertionOrderIterator : public ValueObject {
 public:
  explicit HInsertionOrderIterator(const HGraph& graph) : graph_(graph), index_(0) {}

  bool Done() const { return index_ == graph_.GetBlocks().Size(); }
  HBasicBlock* Current() const { return graph_.GetBlocks().Get(index_); }
  void Advance() { ++index_; }

 private:
  const HGraph& graph_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HInsertionOrderIterator);
};

class HReversePostOrderIterator : public ValueObject {
 public:
  explicit HReversePostOrderIterator(const HGraph& graph) : graph_(graph), index_(0) {
    // Check that reverse post order of the graph has been built.
    DCHECK(!graph.GetReversePostOrder().IsEmpty());
  }

  bool Done() const { return index_ == graph_.GetReversePostOrder().Size(); }
  HBasicBlock* Current() const { return graph_.GetReversePostOrder().Get(index_); }
  void Advance() { ++index_; }

 private:
  const HGraph& graph_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HReversePostOrderIterator);
};

class HPostOrderIterator : public ValueObject {
 public:
  explicit HPostOrderIterator(const HGraph& graph)
      : graph_(graph), index_(graph_.GetReversePostOrder().Size()) {
    // Check that reverse post order of the graph has been built.
    DCHECK(!graph.GetReversePostOrder().IsEmpty());
  }

  bool Done() const { return index_ == 0; }
  HBasicBlock* Current() const { return graph_.GetReversePostOrder().Get(index_ - 1); }
  void Advance() { --index_; }

 private:
  const HGraph& graph_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HPostOrderIterator);
};

class HLinearPostOrderIterator : public ValueObject {
 public:
  explicit HLinearPostOrderIterator(const HGraph& graph)
      : order_(graph.GetLinearOrder()), index_(graph.GetLinearOrder().Size()) {}

  bool Done() const { return index_ == 0; }

  HBasicBlock* Current() const { return order_.Get(index_ -1); }

  void Advance() {
    --index_;
    DCHECK_GE(index_, 0U);
  }

 private:
  const GrowableArray<HBasicBlock*>& order_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HLinearPostOrderIterator);
};

class HLinearOrderIterator : public ValueObject {
 public:
  explicit HLinearOrderIterator(const HGraph& graph)
      : order_(graph.GetLinearOrder()), index_(0) {}

  bool Done() const { return index_ == order_.Size(); }
  HBasicBlock* Current() const { return order_.Get(index_); }
  void Advance() { ++index_; }

 private:
  const GrowableArray<HBasicBlock*>& order_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HLinearOrderIterator);
};

// Iterator over the blocks that art part of the loop. Includes blocks part
// of an inner loop. The order in which the blocks are iterated is on their
// block id.
class HBlocksInLoopIterator : public ValueObject {
 public:
  explicit HBlocksInLoopIterator(const HLoopInformation& info)
      : blocks_in_loop_(info.GetBlocks()),
        blocks_(info.GetHeader()->GetGraph()->GetBlocks()),
        index_(0) {
    if (!blocks_in_loop_.IsBitSet(index_)) {
      Advance();
    }
  }

  bool Done() const { return index_ == blocks_.Size(); }
  HBasicBlock* Current() const { return blocks_.Get(index_); }
  void Advance() {
    ++index_;
    for (size_t e = blocks_.Size(); index_ < e; ++index_) {
      if (blocks_in_loop_.IsBitSet(index_)) {
        break;
      }
    }
  }

 private:
  const BitVector& blocks_in_loop_;
  const GrowableArray<HBasicBlock*>& blocks_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HBlocksInLoopIterator);
};

// Iterator over the blocks that art part of the loop. Includes blocks part
// of an inner loop. The order in which the blocks are iterated is reverse
// post order.
class HBlocksInLoopReversePostOrderIterator : public ValueObject {
 public:
  explicit HBlocksInLoopReversePostOrderIterator(const HLoopInformation& info)
      : blocks_in_loop_(info.GetBlocks()),
        blocks_(info.GetHeader()->GetGraph()->GetReversePostOrder()),
        index_(0) {
    if (!blocks_in_loop_.IsBitSet(blocks_.Get(index_)->GetBlockId())) {
      Advance();
    }
  }

  bool Done() const { return index_ == blocks_.Size(); }
  HBasicBlock* Current() const { return blocks_.Get(index_); }
  void Advance() {
    ++index_;
    for (size_t e = blocks_.Size(); index_ < e; ++index_) {
      if (blocks_in_loop_.IsBitSet(blocks_.Get(index_)->GetBlockId())) {
        break;
      }
    }
  }

 private:
  const BitVector& blocks_in_loop_;
  const GrowableArray<HBasicBlock*>& blocks_;
  size_t index_;

  DISALLOW_COPY_AND_ASSIGN(HBlocksInLoopReversePostOrderIterator);
};

inline int64_t Int64FromConstant(HConstant* constant) {
  DCHECK(constant->IsIntConstant() || constant->IsLongConstant());
  return constant->IsIntConstant() ? constant->AsIntConstant()->GetValue()
                                   : constant->AsLongConstant()->GetValue();
}

}  // namespace art

#endif  // ART_COMPILER_OPTIMIZING_NODES_H_