src/compiler/instruction.h

// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_COMPILER_INSTRUCTION_H_
#define V8_COMPILER_INSTRUCTION_H_

#include <deque>
#include <iosfwd>
#include <map>
#include <set>

#include "src/base/compiler-specific.h"
#include "src/compiler/common-operator.h"
#include "src/compiler/frame.h"
#include "src/compiler/instruction-codes.h"
#include "src/compiler/opcodes.h"
#include "src/double.h"
#include "src/globals.h"
#include "src/macro-assembler.h"
#include "src/register-configuration.h"
#include "src/source-position.h"
#include "src/zone/zone-allocator.h"

namespace v8 {
namespace internal {
namespace compiler {

class Schedule;
class SourcePositionTable;

class V8_EXPORT_PRIVATE InstructionOperand {
 public:
  static const int kInvalidVirtualRegister = -1;

  enum Kind {
    INVALID,
    UNALLOCATED,
    CONSTANT,
    IMMEDIATE,
    // Location operand kinds.
    EXPLICIT,
    ALLOCATED,
    FIRST_LOCATION_OPERAND_KIND = EXPLICIT
    // Location operand kinds must be last.
  };

  InstructionOperand() : InstructionOperand(INVALID) {}

  Kind kind() const { return KindField::decode(value_); }

#define INSTRUCTION_OPERAND_PREDICATE(name, type) \
  bool Is##name() const { return kind() == type; }
  INSTRUCTION_OPERAND_PREDICATE(Invalid, INVALID)
  // UnallocatedOperands are place-holder operands created before register
  // allocation. They later are assigned registers and become AllocatedOperands.
  INSTRUCTION_OPERAND_PREDICATE(Unallocated, UNALLOCATED)
  // Constant operands participate in register allocation. They are allocated to
  // registers but have a special "spilling" behavior. When a ConstantOperand
  // value must be rematerialized, it is loaded from an immediate constant
  // rather from an unspilled slot.
  INSTRUCTION_OPERAND_PREDICATE(Constant, CONSTANT)
  // ImmediateOperands do not participate in register allocation and are only
  // embedded directly in instructions, e.g. small integers and on some
  // platforms Objects.
  INSTRUCTION_OPERAND_PREDICATE(Immediate, IMMEDIATE)
  // ExplicitOperands do not participate in register allocation. They are
  // created by the instruction selector for direct access to registers and
  // stack slots, completely bypassing the register allocator. They are never
  // associated with a virtual register
  INSTRUCTION_OPERAND_PREDICATE(Explicit, EXPLICIT)
  // AllocatedOperands are registers or stack slots that are assigned by the
  // register allocator and are always associated with a virtual register.
  INSTRUCTION_OPERAND_PREDICATE(Allocated, ALLOCATED)
#undef INSTRUCTION_OPERAND_PREDICATE

  inline bool IsAnyLocationOperand() const;
  inline bool IsLocationOperand() const;
  inline bool IsFPLocationOperand() const;
  inline bool IsAnyRegister() const;
  inline bool IsRegister() const;
  inline bool IsFPRegister() const;
  inline bool IsFloatRegister() const;
  inline bool IsDoubleRegister() const;
  inline bool IsSimd128Register() const;
  inline bool IsAnyStackSlot() const;
  inline bool IsStackSlot() const;
  inline bool IsFPStackSlot() const;
  inline bool IsFloatStackSlot() const;
  inline bool IsDoubleStackSlot() const;
  inline bool IsSimd128StackSlot() const;

  template <typename SubKindOperand>
  static SubKindOperand* New(Zone* zone, const SubKindOperand& op) {
    void* buffer = zone->New(sizeof(op));
    return new (buffer) SubKindOperand(op);
  }

  static void ReplaceWith(InstructionOperand* dest,
                          const InstructionOperand* src) {
    *dest = *src;
  }

  bool Equals(const InstructionOperand& that) const {
    return this->value_ == that.value_;
  }

  bool Compare(const InstructionOperand& that) const {
    return this->value_ < that.value_;
  }

  bool EqualsCanonicalized(const InstructionOperand& that) const {
    return this->GetCanonicalizedValue() == that.GetCanonicalizedValue();
  }

  bool CompareCanonicalized(const InstructionOperand& that) const {
    return this->GetCanonicalizedValue() < that.GetCanonicalizedValue();
  }

  bool InterferesWith(const InstructionOperand& other) const;

  // APIs to aid debugging. For general-stream APIs, use operator<<
  void Print(const RegisterConfiguration* config) const;
  void Print() const;

 protected:
  explicit InstructionOperand(Kind kind) : value_(KindField::encode(kind)) {}

  inline uint64_t GetCanonicalizedValue() const;

  class KindField : public BitField64<Kind, 0, 3> {};

  uint64_t value_;
};


typedef ZoneVector<InstructionOperand> InstructionOperandVector;


struct PrintableInstructionOperand {
  const RegisterConfiguration* register_configuration_;
  InstructionOperand op_;
};


std::ostream& operator<<(std::ostream& os,
                         const PrintableInstructionOperand& op);


#define INSTRUCTION_OPERAND_CASTS(OperandType, OperandKind)      \
                                                                 \
  static OperandType* cast(InstructionOperand* op) {             \
    DCHECK_EQ(OperandKind, op->kind());                          \
    return static_cast<OperandType*>(op);                        \
  }                                                              \
                                                                 \
  static const OperandType* cast(const InstructionOperand* op) { \
    DCHECK_EQ(OperandKind, op->kind());                          \
    return static_cast<const OperandType*>(op);                  \
  }                                                              \
                                                                 \
  static OperandType cast(const InstructionOperand& op) {        \
    DCHECK_EQ(OperandKind, op.kind());                           \
    return *static_cast<const OperandType*>(&op);                \
  }

class UnallocatedOperand final : public InstructionOperand {
 public:
  enum BasicPolicy { FIXED_SLOT, EXTENDED_POLICY };

  enum ExtendedPolicy {
    NONE,
    REGISTER_OR_SLOT,
    REGISTER_OR_SLOT_OR_CONSTANT,
    FIXED_REGISTER,
    FIXED_FP_REGISTER,
    MUST_HAVE_REGISTER,
    MUST_HAVE_SLOT,
    SAME_AS_FIRST_INPUT
  };

  // Lifetime of operand inside the instruction.
  enum Lifetime {
    // USED_AT_START operand is guaranteed to be live only at instruction start.
    // The register allocator is free to assign the same register to some other
    // operand used inside instruction (i.e. temporary or output).
    USED_AT_START,

    // USED_AT_END operand is treated as live until the end of instruction.
    // This means that register allocator will not reuse its register for any
    // other operand inside instruction.
    USED_AT_END
  };

  UnallocatedOperand(ExtendedPolicy policy, int virtual_register)
      : UnallocatedOperand(virtual_register) {
    value_ |= BasicPolicyField::encode(EXTENDED_POLICY);
    value_ |= ExtendedPolicyField::encode(policy);
    value_ |= LifetimeField::encode(USED_AT_END);
  }

  UnallocatedOperand(BasicPolicy policy, int index, int virtual_register)
      : UnallocatedOperand(virtual_register) {
    DCHECK(policy == FIXED_SLOT);
    value_ |= BasicPolicyField::encode(policy);
    value_ |= static_cast<int64_t>(index) << FixedSlotIndexField::kShift;
    DCHECK(this->fixed_slot_index() == index);
  }

  UnallocatedOperand(ExtendedPolicy policy, int index, int virtual_register)
      : UnallocatedOperand(virtual_register) {
    DCHECK(policy == FIXED_REGISTER || policy == FIXED_FP_REGISTER);
    value_ |= BasicPolicyField::encode(EXTENDED_POLICY);
    value_ |= ExtendedPolicyField::encode(policy);
    value_ |= LifetimeField::encode(USED_AT_END);
    value_ |= FixedRegisterField::encode(index);
  }

  UnallocatedOperand(ExtendedPolicy policy, Lifetime lifetime,
                     int virtual_register)
      : UnallocatedOperand(virtual_register) {
    value_ |= BasicPolicyField::encode(EXTENDED_POLICY);
    value_ |= ExtendedPolicyField::encode(policy);
    value_ |= LifetimeField::encode(lifetime);
  }

  UnallocatedOperand(int reg_id, int slot_id, int virtual_register)
      : UnallocatedOperand(FIXED_REGISTER, reg_id, virtual_register) {
    value_ |= HasSecondaryStorageField::encode(true);
    value_ |= SecondaryStorageField::encode(slot_id);
  }

  UnallocatedOperand(const UnallocatedOperand& other, int virtual_register) {
    DCHECK_NE(kInvalidVirtualRegister, virtual_register);
    value_ = VirtualRegisterField::update(
        other.value_, static_cast<uint32_t>(virtual_register));
  }

  // Predicates for the operand policy.
  bool HasRegisterOrSlotPolicy() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == REGISTER_OR_SLOT;
  }
  bool HasRegisterOrSlotOrConstantPolicy() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == REGISTER_OR_SLOT_OR_CONSTANT;
  }
  bool HasFixedPolicy() const {
    return basic_policy() == FIXED_SLOT ||
           extended_policy() == FIXED_REGISTER ||
           extended_policy() == FIXED_FP_REGISTER;
  }
  bool HasRegisterPolicy() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == MUST_HAVE_REGISTER;
  }
  bool HasSlotPolicy() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == MUST_HAVE_SLOT;
  }
  bool HasSameAsInputPolicy() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == SAME_AS_FIRST_INPUT;
  }
  bool HasFixedSlotPolicy() const { return basic_policy() == FIXED_SLOT; }
  bool HasFixedRegisterPolicy() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == FIXED_REGISTER;
  }
  bool HasFixedFPRegisterPolicy() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == FIXED_FP_REGISTER;
  }
  bool HasSecondaryStorage() const {
    return basic_policy() == EXTENDED_POLICY &&
           extended_policy() == FIXED_REGISTER &&
           HasSecondaryStorageField::decode(value_);
  }
  int GetSecondaryStorage() const {
    DCHECK(HasSecondaryStorage());
    return SecondaryStorageField::decode(value_);
  }

  // [basic_policy]: Distinguish between FIXED_SLOT and all other policies.
  BasicPolicy basic_policy() const {
    return BasicPolicyField::decode(value_);
  }

  // [extended_policy]: Only for non-FIXED_SLOT. The finer-grained policy.
  ExtendedPolicy extended_policy() const {
    DCHECK(basic_policy() == EXTENDED_POLICY);
    return ExtendedPolicyField::decode(value_);
  }

  // [fixed_slot_index]: Only for FIXED_SLOT.
  int fixed_slot_index() const {
    DCHECK(HasFixedSlotPolicy());
    return static_cast<int>(static_cast<int64_t>(value_) >>
                            FixedSlotIndexField::kShift);
  }

  // [fixed_register_index]: Only for FIXED_REGISTER or FIXED_FP_REGISTER.
  int fixed_register_index() const {
    DCHECK(HasFixedRegisterPolicy() || HasFixedFPRegisterPolicy());
    return FixedRegisterField::decode(value_);
  }

  // [virtual_register]: The virtual register ID for this operand.
  int32_t virtual_register() const {
    return static_cast<int32_t>(VirtualRegisterField::decode(value_));
  }

  // [lifetime]: Only for non-FIXED_SLOT.
  bool IsUsedAtStart() const {
    DCHECK(basic_policy() == EXTENDED_POLICY);
    return LifetimeField::decode(value_) == USED_AT_START;
  }

  INSTRUCTION_OPERAND_CASTS(UnallocatedOperand, UNALLOCATED);

  // The encoding used for UnallocatedOperand operands depends on the policy
  // that is
  // stored within the operand. The FIXED_SLOT policy uses a compact encoding
  // because it accommodates a larger pay-load.
  //
  // For FIXED_SLOT policy:
  //     +------------------------------------------------+
  //     |      slot_index   | 0 | virtual_register | 001 |
  //     +------------------------------------------------+
  //
  // For all other (extended) policies:
  //     +-----------------------------------------------------+
  //     |  reg_index  | L | PPP |  1 | virtual_register | 001 |
  //     +-----------------------------------------------------+
  //     L ... Lifetime
  //     P ... Policy
  //
  // The slot index is a signed value which requires us to decode it manually
  // instead of using the BitField utility class.

  STATIC_ASSERT(KindField::kSize == 3);

  class VirtualRegisterField : public BitField64<uint32_t, 3, 32> {};

  // BitFields for all unallocated operands.
  class BasicPolicyField : public BitField64<BasicPolicy, 35, 1> {};

  // BitFields specific to BasicPolicy::FIXED_SLOT.
  class FixedSlotIndexField : public BitField64<int, 36, 28> {};

  // BitFields specific to BasicPolicy::EXTENDED_POLICY.
  class ExtendedPolicyField : public BitField64<ExtendedPolicy, 36, 3> {};
  class LifetimeField : public BitField64<Lifetime, 39, 1> {};
  class HasSecondaryStorageField : public BitField64<bool, 40, 1> {};
  class FixedRegisterField : public BitField64<int, 41, 6> {};
  class SecondaryStorageField : public BitField64<int, 47, 3> {};

 private:
  explicit UnallocatedOperand(int virtual_register)
      : InstructionOperand(UNALLOCATED) {
    value_ |=
        VirtualRegisterField::encode(static_cast<uint32_t>(virtual_register));
  }
};


class ConstantOperand : public InstructionOperand {
 public:
  explicit ConstantOperand(int virtual_register)
      : InstructionOperand(CONSTANT) {
    value_ |=
        VirtualRegisterField::encode(static_cast<uint32_t>(virtual_register));
  }

  int32_t virtual_register() const {
    return static_cast<int32_t>(VirtualRegisterField::decode(value_));
  }

  static ConstantOperand* New(Zone* zone, int virtual_register) {
    return InstructionOperand::New(zone, ConstantOperand(virtual_register));
  }

  INSTRUCTION_OPERAND_CASTS(ConstantOperand, CONSTANT);

  STATIC_ASSERT(KindField::kSize == 3);
  class VirtualRegisterField : public BitField64<uint32_t, 3, 32> {};
};


class ImmediateOperand : public InstructionOperand {
 public:
  enum ImmediateType { INLINE, INDEXED };

  explicit ImmediateOperand(ImmediateType type, int32_t value)
      : InstructionOperand(IMMEDIATE) {
    value_ |= TypeField::encode(type);
    value_ |= static_cast<int64_t>(value) << ValueField::kShift;
  }

  ImmediateType type() const { return TypeField::decode(value_); }

  int32_t inline_value() const {
    DCHECK_EQ(INLINE, type());
    return static_cast<int64_t>(value_) >> ValueField::kShift;
  }

  int32_t indexed_value() const {
    DCHECK_EQ(INDEXED, type());
    return static_cast<int64_t>(value_) >> ValueField::kShift;
  }

  static ImmediateOperand* New(Zone* zone, ImmediateType type, int32_t value) {
    return InstructionOperand::New(zone, ImmediateOperand(type, value));
  }

  INSTRUCTION_OPERAND_CASTS(ImmediateOperand, IMMEDIATE);

  STATIC_ASSERT(KindField::kSize == 3);
  class TypeField : public BitField64<ImmediateType, 3, 1> {};
  class ValueField : public BitField64<int32_t, 32, 32> {};
};


class LocationOperand : public InstructionOperand {
 public:
  enum LocationKind { REGISTER, STACK_SLOT };

  LocationOperand(InstructionOperand::Kind operand_kind,
                  LocationOperand::LocationKind location_kind,
                  MachineRepresentation rep, int index)
      : InstructionOperand(operand_kind) {
    DCHECK_IMPLIES(location_kind == REGISTER, index >= 0);
    DCHECK(IsSupportedRepresentation(rep));
    value_ |= LocationKindField::encode(location_kind);
    value_ |= RepresentationField::encode(rep);
    value_ |= static_cast<int64_t>(index) << IndexField::kShift;
  }

  int index() const {
    DCHECK(IsStackSlot() || IsFPStackSlot());
    return static_cast<int64_t>(value_) >> IndexField::kShift;
  }

  int register_code() const {
    DCHECK(IsRegister() || IsFPRegister());
    return static_cast<int64_t>(value_) >> IndexField::kShift;
  }

  Register GetRegister() const {
    DCHECK(IsRegister());
    return Register::from_code(register_code());
  }

  FloatRegister GetFloatRegister() const {
    DCHECK(IsFloatRegister());
    return FloatRegister::from_code(register_code());
  }

  DoubleRegister GetDoubleRegister() const {
    // On platforms where FloatRegister, DoubleRegister, and Simd128Register
    // are all the same type, it's convenient to treat everything as a
    // DoubleRegister, so be lax about type checking here.
    DCHECK(IsFPRegister());
    return DoubleRegister::from_code(register_code());
  }

  Simd128Register GetSimd128Register() const {
    DCHECK(IsSimd128Register());
    return Simd128Register::from_code(register_code());
  }

  LocationKind location_kind() const {
    return LocationKindField::decode(value_);
  }

  MachineRepresentation representation() const {
    return RepresentationField::decode(value_);
  }

  static bool IsSupportedRepresentation(MachineRepresentation rep) {
    switch (rep) {
      case MachineRepresentation::kWord32:
      case MachineRepresentation::kWord64:
      case MachineRepresentation::kFloat32:
      case MachineRepresentation::kFloat64:
      case MachineRepresentation::kSimd128:
      case MachineRepresentation::kTaggedSigned:
      case MachineRepresentation::kTaggedPointer:
      case MachineRepresentation::kTagged:
        return true;
      case MachineRepresentation::kBit:
      case MachineRepresentation::kWord8:
      case MachineRepresentation::kWord16:
      case MachineRepresentation::kNone:
        return false;
    }
    UNREACHABLE();
  }

  // Return true if the locations can be moved to one another.
  bool IsCompatible(LocationOperand* op);

  static LocationOperand* cast(InstructionOperand* op) {
    DCHECK(op->IsAnyLocationOperand());
    return static_cast<LocationOperand*>(op);
  }

  static const LocationOperand* cast(const InstructionOperand* op) {
    DCHECK(op->IsAnyLocationOperand());
    return static_cast<const LocationOperand*>(op);
  }

  static LocationOperand cast(const InstructionOperand& op) {
    DCHECK(op.IsAnyLocationOperand());
    return *static_cast<const LocationOperand*>(&op);
  }

  STATIC_ASSERT(KindField::kSize == 3);
  class LocationKindField : public BitField64<LocationKind, 3, 2> {};
  class RepresentationField : public BitField64<MachineRepresentation, 5, 8> {};
  class IndexField : public BitField64<int32_t, 35, 29> {};
};

class V8_EXPORT_PRIVATE ExplicitOperand
    : public NON_EXPORTED_BASE(LocationOperand) {
 public:
  ExplicitOperand(LocationKind kind, MachineRepresentation rep, int index);

  static ExplicitOperand* New(Zone* zone, LocationKind kind,
                              MachineRepresentation rep, int index) {
    return InstructionOperand::New(zone, ExplicitOperand(kind, rep, index));
  }

  INSTRUCTION_OPERAND_CASTS(ExplicitOperand, EXPLICIT);
};


class AllocatedOperand : public LocationOperand {
 public:
  AllocatedOperand(LocationKind kind, MachineRepresentation rep, int index)
      : LocationOperand(ALLOCATED, kind, rep, index) {}

  static AllocatedOperand* New(Zone* zone, LocationKind kind,
                               MachineRepresentation rep, int index) {
    return InstructionOperand::New(zone, AllocatedOperand(kind, rep, index));
  }

  INSTRUCTION_OPERAND_CASTS(AllocatedOperand, ALLOCATED);
};


#undef INSTRUCTION_OPERAND_CASTS

bool InstructionOperand::IsAnyLocationOperand() const {
  return this->kind() >= FIRST_LOCATION_OPERAND_KIND;
}

bool InstructionOperand::IsLocationOperand() const {
  return IsAnyLocationOperand() &&
         !IsFloatingPoint(LocationOperand::cast(this)->representation());
}

bool InstructionOperand::IsFPLocationOperand() const {
  return IsAnyLocationOperand() &&
         IsFloatingPoint(LocationOperand::cast(this)->representation());
}

bool InstructionOperand::IsAnyRegister() const {
  return IsAnyLocationOperand() &&
         LocationOperand::cast(this)->location_kind() ==
             LocationOperand::REGISTER;
}


bool InstructionOperand::IsRegister() const {
  return IsAnyRegister() &&
         !IsFloatingPoint(LocationOperand::cast(this)->representation());
}

bool InstructionOperand::IsFPRegister() const {
  return IsAnyRegister() &&
         IsFloatingPoint(LocationOperand::cast(this)->representation());
}

bool InstructionOperand::IsFloatRegister() const {
  return IsAnyRegister() &&
         LocationOperand::cast(this)->representation() ==
             MachineRepresentation::kFloat32;
}

bool InstructionOperand::IsDoubleRegister() const {
  return IsAnyRegister() &&
         LocationOperand::cast(this)->representation() ==
             MachineRepresentation::kFloat64;
}

bool InstructionOperand::IsSimd128Register() const {
  return IsAnyRegister() && LocationOperand::cast(this)->representation() ==
                                MachineRepresentation::kSimd128;
}

bool InstructionOperand::IsAnyStackSlot() const {
  return IsAnyLocationOperand() &&
         LocationOperand::cast(this)->location_kind() ==
             LocationOperand::STACK_SLOT;
}

bool InstructionOperand::IsStackSlot() const {
  return IsAnyStackSlot() &&
         !IsFloatingPoint(LocationOperand::cast(this)->representation());
}

bool InstructionOperand::IsFPStackSlot() const {
  return IsAnyStackSlot() &&
         IsFloatingPoint(LocationOperand::cast(this)->representation());
}

bool InstructionOperand::IsFloatStackSlot() const {
  return IsAnyLocationOperand() &&
         LocationOperand::cast(this)->location_kind() ==
             LocationOperand::STACK_SLOT &&
         LocationOperand::cast(this)->representation() ==
             MachineRepresentation::kFloat32;
}

bool InstructionOperand::IsDoubleStackSlot() const {
  return IsAnyLocationOperand() &&
         LocationOperand::cast(this)->location_kind() ==
             LocationOperand::STACK_SLOT &&
         LocationOperand::cast(this)->representation() ==
             MachineRepresentation::kFloat64;
}

bool InstructionOperand::IsSimd128StackSlot() const {
  return IsAnyLocationOperand() &&
         LocationOperand::cast(this)->location_kind() ==
             LocationOperand::STACK_SLOT &&
         LocationOperand::cast(this)->representation() ==
             MachineRepresentation::kSimd128;
}

uint64_t InstructionOperand::GetCanonicalizedValue() const {
  if (IsAnyLocationOperand()) {
    MachineRepresentation canonical = MachineRepresentation::kNone;
    if (IsFPRegister()) {
      if (kSimpleFPAliasing) {
        // We treat all FP register operands the same for simple aliasing.
        canonical = MachineRepresentation::kFloat64;
      } else {
        // We need to distinguish FP register operands of different reps when
        // aliasing is not simple (e.g. ARM).
        canonical = LocationOperand::cast(this)->representation();
      }
    }
    return InstructionOperand::KindField::update(
        LocationOperand::RepresentationField::update(this->value_, canonical),
        LocationOperand::EXPLICIT);
  }
  return this->value_;
}

// Required for maps that don't care about machine type.
struct CompareOperandModuloType {
  bool operator()(const InstructionOperand& a,
                  const InstructionOperand& b) const {
    return a.CompareCanonicalized(b);
  }
};

class V8_EXPORT_PRIVATE MoveOperands final
    : public NON_EXPORTED_BASE(ZoneObject) {
 public:
  MoveOperands(const InstructionOperand& source,
               const InstructionOperand& destination)
      : source_(source), destination_(destination) {
    DCHECK(!source.IsInvalid() && !destination.IsInvalid());
  }

  const InstructionOperand& source() const { return source_; }
  InstructionOperand& source() { return source_; }
  void set_source(const InstructionOperand& operand) { source_ = operand; }

  const InstructionOperand& destination() const { return destination_; }
  InstructionOperand& destination() { return destination_; }
  void set_destination(const InstructionOperand& operand) {
    destination_ = operand;
  }

  // The gap resolver marks moves as "in-progress" by clearing the
  // destination (but not the source).
  bool IsPending() const {
    return destination_.IsInvalid() && !source_.IsInvalid();
  }
  void SetPending() { destination_ = InstructionOperand(); }

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

  // We clear both operands to indicate move that's been eliminated.
  void Eliminate() { source_ = destination_ = InstructionOperand(); }
  bool IsEliminated() const {
    DCHECK_IMPLIES(source_.IsInvalid(), destination_.IsInvalid());
    return source_.IsInvalid();
  }

  // APIs to aid debugging. For general-stream APIs, use operator<<
  void Print(const RegisterConfiguration* config) const;
  void Print() const;

 private:
  InstructionOperand source_;
  InstructionOperand destination_;

  DISALLOW_COPY_AND_ASSIGN(MoveOperands);
};


struct PrintableMoveOperands {
  const RegisterConfiguration* register_configuration_;
  const MoveOperands* move_operands_;
};


std::ostream& operator<<(std::ostream& os, const PrintableMoveOperands& mo);

class V8_EXPORT_PRIVATE ParallelMove final
    : public NON_EXPORTED_BASE(ZoneVector<MoveOperands *>),
      public NON_EXPORTED_BASE(ZoneObject) {
 public:
  explicit ParallelMove(Zone* zone) : ZoneVector<MoveOperands*>(zone) {
    reserve(4);
  }

  MoveOperands* AddMove(const InstructionOperand& from,
                        const InstructionOperand& to) {
    Zone* zone = get_allocator().zone();
    return AddMove(from, to, zone);
  }

  MoveOperands* AddMove(const InstructionOperand& from,
                        const InstructionOperand& to,
                        Zone* operand_allocation_zone) {
    MoveOperands* move = new (operand_allocation_zone) MoveOperands(from, to);
    push_back(move);
    return move;
  }

  bool IsRedundant() const;

  // Prepare this ParallelMove to insert move as if it happened in a subsequent
  // ParallelMove.  move->source() may be changed.  Any MoveOperands added to
  // to_eliminate must be Eliminated.
  void PrepareInsertAfter(MoveOperands* move,
                          ZoneVector<MoveOperands*>* to_eliminate) const;

 private:
  DISALLOW_COPY_AND_ASSIGN(ParallelMove);
};


struct PrintableParallelMove {
  const RegisterConfiguration* register_configuration_;
  const ParallelMove* parallel_move_;
};


std::ostream& operator<<(std::ostream& os, const PrintableParallelMove& pm);


class ReferenceMap final : public ZoneObject {
 public:
  explicit ReferenceMap(Zone* zone)
      : reference_operands_(8, zone), instruction_position_(-1) {}

  const ZoneVector<InstructionOperand>& reference_operands() const {
    return reference_operands_;
  }
  int instruction_position() const { return instruction_position_; }

  void set_instruction_position(int pos) {
    DCHECK_EQ(-1, instruction_position_);
    instruction_position_ = pos;
  }

  void RecordReference(const AllocatedOperand& op);

 private:
  friend std::ostream& operator<<(std::ostream& os, const ReferenceMap& pm);

  ZoneVector<InstructionOperand> reference_operands_;
  int instruction_position_;
};

std::ostream& operator<<(std::ostream& os, const ReferenceMap& pm);

class InstructionBlock;

class V8_EXPORT_PRIVATE Instruction final {
 public:
  size_t OutputCount() const { return OutputCountField::decode(bit_field_); }
  const InstructionOperand* OutputAt(size_t i) const {
    DCHECK(i < OutputCount());
    return &operands_[i];
  }
  InstructionOperand* OutputAt(size_t i) {
    DCHECK(i < OutputCount());
    return &operands_[i];
  }

  bool HasOutput() const { return OutputCount() > 0; }
  const InstructionOperand* Output() const { return OutputAt(0); }
  InstructionOperand* Output() { return OutputAt(0); }

  size_t InputCount() const { return InputCountField::decode(bit_field_); }
  const InstructionOperand* InputAt(size_t i) const {
    DCHECK(i < InputCount());
    return &operands_[OutputCount() + i];
  }
  InstructionOperand* InputAt(size_t i) {
    DCHECK(i < InputCount());
    return &operands_[OutputCount() + i];
  }

  size_t TempCount() const { return TempCountField::decode(bit_field_); }
  const InstructionOperand* TempAt(size_t i) const {
    DCHECK(i < TempCount());
    return &operands_[OutputCount() + InputCount() + i];
  }
  InstructionOperand* TempAt(size_t i) {
    DCHECK(i < TempCount());
    return &operands_[OutputCount() + InputCount() + i];
  }

  InstructionCode opcode() const { return opcode_; }
  ArchOpcode arch_opcode() const { return ArchOpcodeField::decode(opcode()); }
  AddressingMode addressing_mode() const {
    return AddressingModeField::decode(opcode());
  }
  FlagsMode flags_mode() const { return FlagsModeField::decode(opcode()); }
  FlagsCondition flags_condition() const {
    return FlagsConditionField::decode(opcode());
  }

  static Instruction* New(Zone* zone, InstructionCode opcode) {
    return New(zone, opcode, 0, nullptr, 0, nullptr, 0, nullptr);
  }

  static Instruction* New(Zone* zone, InstructionCode opcode,
                          size_t output_count, InstructionOperand* outputs,
                          size_t input_count, InstructionOperand* inputs,
                          size_t temp_count, InstructionOperand* temps) {
    DCHECK_LE(0, opcode);
    DCHECK(output_count == 0 || outputs != nullptr);
    DCHECK(input_count == 0 || inputs != nullptr);
    DCHECK(temp_count == 0 || temps != nullptr);
    // TODO(jarin/mstarzinger): Handle this gracefully. See crbug.com/582702.
    CHECK(InputCountField::is_valid(input_count));

    size_t total_extra_ops = output_count + input_count + temp_count;
    if (total_extra_ops != 0) total_extra_ops--;
    int size = static_cast<int>(
        RoundUp(sizeof(Instruction), sizeof(InstructionOperand)) +
        total_extra_ops * sizeof(InstructionOperand));
    return new (zone->New(size)) Instruction(
        opcode, output_count, outputs, input_count, inputs, temp_count, temps);
  }

  Instruction* MarkAsCall() {
    bit_field_ = IsCallField::update(bit_field_, true);
    return this;
  }
  bool IsCall() const { return IsCallField::decode(bit_field_); }
  bool NeedsReferenceMap() const { return IsCall(); }
  bool HasReferenceMap() const { return reference_map_ != nullptr; }

  bool ClobbersRegisters() const { return IsCall(); }
  bool ClobbersTemps() const { return IsCall(); }
  bool ClobbersDoubleRegisters() const { return IsCall(); }
  ReferenceMap* reference_map() const { return reference_map_; }

  void set_reference_map(ReferenceMap* map) {
    DCHECK(NeedsReferenceMap());
    DCHECK(!reference_map_);
    reference_map_ = map;
  }

  void OverwriteWithNop() {
    opcode_ = ArchOpcodeField::encode(kArchNop);
    bit_field_ = 0;
    reference_map_ = nullptr;
  }

  bool IsNop() const { return arch_opcode() == kArchNop; }

  bool IsDeoptimizeCall() const {
    return arch_opcode() == ArchOpcode::kArchDeoptimize ||
           FlagsModeField::decode(opcode()) == kFlags_deoptimize ||
           FlagsModeField::decode(opcode()) == kFlags_deoptimize_and_poison;
  }

  bool IsTrap() const {
    return FlagsModeField::decode(opcode()) == kFlags_trap;
  }

  bool IsJump() const { return arch_opcode() == ArchOpcode::kArchJmp; }
  bool IsRet() const { return arch_opcode() == ArchOpcode::kArchRet; }
  bool IsTailCall() const {
    return arch_opcode() == ArchOpcode::kArchTailCallCodeObject ||
           arch_opcode() == ArchOpcode::kArchTailCallCodeObjectFromJSFunction ||
           arch_opcode() == ArchOpcode::kArchTailCallAddress ||
           arch_opcode() == ArchOpcode::kArchTailCallWasm;
  }
  bool IsThrow() const {
    return arch_opcode() == ArchOpcode::kArchThrowTerminator;
  }

  enum GapPosition {
    START,
    END,
    FIRST_GAP_POSITION = START,
    LAST_GAP_POSITION = END
  };

  ParallelMove* GetOrCreateParallelMove(GapPosition pos, Zone* zone) {
    if (parallel_moves_[pos] == nullptr) {
      parallel_moves_[pos] = new (zone) ParallelMove(zone);
    }
    return parallel_moves_[pos];
  }

  ParallelMove* GetParallelMove(GapPosition pos) {
    return parallel_moves_[pos];
  }

  const ParallelMove* GetParallelMove(GapPosition pos) const {
    return parallel_moves_[pos];
  }

  bool AreMovesRedundant() const;

  ParallelMove* const* parallel_moves() const { return &parallel_moves_[0]; }
  ParallelMove** parallel_moves() { return &parallel_moves_[0]; }

  // The block_id may be invalidated in JumpThreading. It is only important for
  // register allocation, to avoid searching for blocks from instruction
  // indexes.
  InstructionBlock* block() const { return block_; }
  void set_block(InstructionBlock* block) {
    DCHECK_NOT_NULL(block);
    block_ = block;
  }

  // APIs to aid debugging. For general-stream APIs, use operator<<
  void Print(const RegisterConfiguration* config) const;
  void Print() const;

  typedef BitField<size_t, 0, 8> OutputCountField;
  typedef BitField<size_t, 8, 16> InputCountField;
  typedef BitField<size_t, 24, 6> TempCountField;

  static const size_t kMaxOutputCount = OutputCountField::kMax;
  static const size_t kMaxInputCount = InputCountField::kMax;
  static const size_t kMaxTempCount = TempCountField::kMax;

 private:
  explicit Instruction(InstructionCode opcode);

  Instruction(InstructionCode opcode, size_t output_count,
              InstructionOperand* outputs, size_t input_count,
              InstructionOperand* inputs, size_t temp_count,
              InstructionOperand* temps);

  typedef BitField<bool, 30, 1> IsCallField;

  InstructionCode opcode_;
  uint32_t bit_field_;
  ParallelMove* parallel_moves_[2];
  ReferenceMap* reference_map_;
  InstructionBlock* block_;
  InstructionOperand operands_[1];

  DISALLOW_COPY_AND_ASSIGN(Instruction);
};


struct PrintableInstruction {
  const RegisterConfiguration* register_configuration_;
  const Instruction* instr_;
};
std::ostream& operator<<(std::ostream& os, const PrintableInstruction& instr);


class RpoNumber final {
 public:
  static const int kInvalidRpoNumber = -1;
  int ToInt() const {
    DCHECK(IsValid());
    return index_;
  }
  size_t ToSize() const {
    DCHECK(IsValid());
    return static_cast<size_t>(index_);
  }
  bool IsValid() const { return index_ >= 0; }
  static RpoNumber FromInt(int index) { return RpoNumber(index); }
  static RpoNumber Invalid() { return RpoNumber(kInvalidRpoNumber); }

  bool IsNext(const RpoNumber other) const {
    DCHECK(IsValid());
    return other.index_ == this->index_ + 1;
  }

  // Comparison operators.
  bool operator==(RpoNumber other) const { return index_ == other.index_; }
  bool operator!=(RpoNumber other) const { return index_ != other.index_; }
  bool operator>(RpoNumber other) const { return index_ > other.index_; }
  bool operator<(RpoNumber other) const { return index_ < other.index_; }
  bool operator<=(RpoNumber other) const { return index_ <= other.index_; }
  bool operator>=(RpoNumber other) const { return index_ >= other.index_; }

 private:
  explicit RpoNumber(int32_t index) : index_(index) {}
  int32_t index_;
};


std::ostream& operator<<(std::ostream&, const RpoNumber&);

class V8_EXPORT_PRIVATE Constant final {
 public:
  enum Type {
    kInt32,
    kInt64,
    kFloat32,
    kFloat64,
    kExternalReference,
    kHeapObject,
    kRpoNumber
  };

  explicit Constant(int32_t v);
  explicit Constant(int64_t v) : type_(kInt64), value_(v) {}
  explicit Constant(float v) : type_(kFloat32), value_(bit_cast<int32_t>(v)) {}
  explicit Constant(double v) : type_(kFloat64), value_(bit_cast<int64_t>(v)) {}
  explicit Constant(ExternalReference ref)
      : type_(kExternalReference), value_(bit_cast<intptr_t>(ref)) {}
  explicit Constant(Handle<HeapObject> obj)
      : type_(kHeapObject), value_(bit_cast<intptr_t>(obj)) {}
  explicit Constant(RpoNumber rpo) : type_(kRpoNumber), value_(rpo.ToInt()) {}
  explicit Constant(RelocatablePtrConstantInfo info);

  Type type() const { return type_; }

  RelocInfo::Mode rmode() const { return rmode_; }

  int32_t ToInt32() const {
    DCHECK(type() == kInt32 || type() == kInt64);
    const int32_t value = static_cast<int32_t>(value_);
    DCHECK_EQ(value_, static_cast<int64_t>(value));
    return value;
  }

  int64_t ToInt64() const {
    if (type() == kInt32) return ToInt32();
    DCHECK_EQ(kInt64, type());
    return value_;
  }

  float ToFloat32() const {
    // TODO(ahaas): We should remove this function. If value_ has the bit
    // representation of a signalling NaN, then returning it as float can cause
    // the signalling bit to flip, and value_ is returned as a quiet NaN.
    DCHECK_EQ(kFloat32, type());
    return bit_cast<float>(static_cast<int32_t>(value_));
  }

  uint32_t ToFloat32AsInt() const {
    DCHECK_EQ(kFloat32, type());
    return bit_cast<uint32_t>(static_cast<int32_t>(value_));
  }

  Double ToFloat64() const {
    DCHECK_EQ(kFloat64, type());
    return Double(bit_cast<uint64_t>(value_));
  }

  ExternalReference ToExternalReference() const {
    DCHECK_EQ(kExternalReference, type());
    return bit_cast<ExternalReference>(static_cast<intptr_t>(value_));
  }

  RpoNumber ToRpoNumber() const {
    DCHECK_EQ(kRpoNumber, type());
    return RpoNumber::FromInt(static_cast<int>(value_));
  }

  Handle<HeapObject> ToHeapObject() const;
  Handle<Code> ToCode() const;

 private:
  Type type_;
  RelocInfo::Mode rmode_ = RelocInfo::NONE;
  int64_t value_;
};


std::ostream& operator<<(std::ostream& os, const Constant& constant);


// Forward declarations.
class FrameStateDescriptor;

enum class StateValueKind : uint8_t {
  kArgumentsElements,
  kArgumentsLength,
  kPlain,
  kOptimizedOut,
  kNested,
  kDuplicate
};

class StateValueDescriptor {
 public:
  StateValueDescriptor()
      : kind_(StateValueKind::kPlain), type_(MachineType::AnyTagged()) {}

  static StateValueDescriptor ArgumentsElements(ArgumentsStateType type) {
    StateValueDescriptor descr(StateValueKind::kArgumentsElements,
                               MachineType::AnyTagged());
    descr.args_type_ = type;
    return descr;
  }
  static StateValueDescriptor ArgumentsLength(ArgumentsStateType type) {
    StateValueDescriptor descr(StateValueKind::kArgumentsLength,
                               MachineType::AnyTagged());
    descr.args_type_ = type;
    return descr;
  }
  static StateValueDescriptor Plain(MachineType type) {
    return StateValueDescriptor(StateValueKind::kPlain, type);
  }
  static StateValueDescriptor OptimizedOut() {
    return StateValueDescriptor(StateValueKind::kOptimizedOut,
                                MachineType::AnyTagged());
  }
  static StateValueDescriptor Recursive(size_t id) {
    StateValueDescriptor descr(StateValueKind::kNested,
                               MachineType::AnyTagged());
    descr.id_ = id;
    return descr;
  }
  static StateValueDescriptor Duplicate(size_t id) {
    StateValueDescriptor descr(StateValueKind::kDuplicate,
                               MachineType::AnyTagged());
    descr.id_ = id;
    return descr;
  }

  bool IsArgumentsElements() const {
    return kind_ == StateValueKind::kArgumentsElements;
  }
  bool IsArgumentsLength() const {
    return kind_ == StateValueKind::kArgumentsLength;
  }
  bool IsPlain() const { return kind_ == StateValueKind::kPlain; }
  bool IsOptimizedOut() const { return kind_ == StateValueKind::kOptimizedOut; }
  bool IsNested() const { return kind_ == StateValueKind::kNested; }
  bool IsDuplicate() const { return kind_ == StateValueKind::kDuplicate; }
  MachineType type() const { return type_; }
  size_t id() const {
    DCHECK(kind_ == StateValueKind::kDuplicate ||
           kind_ == StateValueKind::kNested);
    return id_;
  }
  ArgumentsStateType arguments_type() const {
    DCHECK(kind_ == StateValueKind::kArgumentsElements ||
           kind_ == StateValueKind::kArgumentsLength);
    return args_type_;
  }

 private:
  StateValueDescriptor(StateValueKind kind, MachineType type)
      : kind_(kind), type_(type) {}

  StateValueKind kind_;
  MachineType type_;
  union {
    size_t id_;
    ArgumentsStateType args_type_;
  };
};

class StateValueList {
 public:
  explicit StateValueList(Zone* zone) : fields_(zone), nested_(zone) {}

  size_t size() { return fields_.size(); }

  struct Value {
    StateValueDescriptor* desc;
    StateValueList* nested;

    Value(StateValueDescriptor* desc, StateValueList* nested)
        : desc(desc), nested(nested) {}
  };

  class iterator {
   public:
    // Bare minimum of operators needed for range iteration.
    bool operator!=(const iterator& other) const {
      return field_iterator != other.field_iterator;
    }
    bool operator==(const iterator& other) const {
      return field_iterator == other.field_iterator;
    }
    iterator& operator++() {
      if (field_iterator->IsNested()) {
        nested_iterator++;
      }
      ++field_iterator;
      return *this;
    }
    Value operator*() {
      StateValueDescriptor* desc = &(*field_iterator);
      StateValueList* nested = desc->IsNested() ? *nested_iterator : nullptr;
      return Value(desc, nested);
    }

   private:
    friend class StateValueList;

    iterator(ZoneVector<StateValueDescriptor>::iterator it,
             ZoneVector<StateValueList*>::iterator nested)
        : field_iterator(it), nested_iterator(nested) {}

    ZoneVector<StateValueDescriptor>::iterator field_iterator;
    ZoneVector<StateValueList*>::iterator nested_iterator;
  };

  void ReserveSize(size_t size) { fields_.reserve(size); }

  StateValueList* PushRecursiveField(Zone* zone, size_t id) {
    fields_.push_back(StateValueDescriptor::Recursive(id));
    StateValueList* nested =
        new (zone->New(sizeof(StateValueList))) StateValueList(zone);
    nested_.push_back(nested);
    return nested;
  }
  void PushArgumentsElements(ArgumentsStateType type) {
    fields_.push_back(StateValueDescriptor::ArgumentsElements(type));
  }
  void PushArgumentsLength(ArgumentsStateType type) {
    fields_.push_back(StateValueDescriptor::ArgumentsLength(type));
  }
  void PushDuplicate(size_t id) {
    fields_.push_back(StateValueDescriptor::Duplicate(id));
  }
  void PushPlain(MachineType type) {
    fields_.push_back(StateValueDescriptor::Plain(type));
  }
  void PushOptimizedOut() {
    fields_.push_back(StateValueDescriptor::OptimizedOut());
  }

  iterator begin() { return iterator(fields_.begin(), nested_.begin()); }
  iterator end() { return iterator(fields_.end(), nested_.end()); }

 private:
  ZoneVector<StateValueDescriptor> fields_;
  ZoneVector<StateValueList*> nested_;
};

class FrameStateDescriptor : public ZoneObject {
 public:
  FrameStateDescriptor(Zone* zone, FrameStateType type, BailoutId bailout_id,
                       OutputFrameStateCombine state_combine,
                       size_t parameters_count, size_t locals_count,
                       size_t stack_count,
                       MaybeHandle<SharedFunctionInfo> shared_info,
                       FrameStateDescriptor* outer_state = nullptr);

  FrameStateType type() const { return type_; }
  BailoutId bailout_id() const { return bailout_id_; }
  OutputFrameStateCombine state_combine() const { return frame_state_combine_; }
  size_t parameters_count() const { return parameters_count_; }
  size_t locals_count() const { return locals_count_; }
  size_t stack_count() const { return stack_count_; }
  MaybeHandle<SharedFunctionInfo> shared_info() const { return shared_info_; }
  FrameStateDescriptor* outer_state() const { return outer_state_; }
  bool HasContext() const {
    return FrameStateFunctionInfo::IsJSFunctionType(type_) ||
           type_ == FrameStateType::kBuiltinContinuation;
  }

  size_t GetSize() const;
  size_t GetTotalSize() const;
  size_t GetFrameCount() const;
  size_t GetJSFrameCount() const;

  StateValueList* GetStateValueDescriptors() { return &values_; }

  static const int kImpossibleValue = 0xdead;

 private:
  FrameStateType type_;
  BailoutId bailout_id_;
  OutputFrameStateCombine frame_state_combine_;
  size_t parameters_count_;
  size_t locals_count_;
  size_t stack_count_;
  StateValueList values_;
  MaybeHandle<SharedFunctionInfo> const shared_info_;
  FrameStateDescriptor* outer_state_;
};

// A deoptimization entry is a pair of the reason why we deoptimize and the
// frame state descriptor that we have to go back to.
class DeoptimizationEntry final {
 public:
  DeoptimizationEntry() {}
  DeoptimizationEntry(FrameStateDescriptor* descriptor, DeoptimizeKind kind,
                      DeoptimizeReason reason, VectorSlotPair const& feedback)
      : descriptor_(descriptor),
        kind_(kind),
        reason_(reason),
        feedback_(feedback) {}

  FrameStateDescriptor* descriptor() const { return descriptor_; }
  DeoptimizeKind kind() const { return kind_; }
  DeoptimizeReason reason() const { return reason_; }
  VectorSlotPair const& feedback() const { return feedback_; }

 private:
  FrameStateDescriptor* descriptor_ = nullptr;
  DeoptimizeKind kind_ = DeoptimizeKind::kEager;
  DeoptimizeReason reason_ = DeoptimizeReason::kUnknown;
  VectorSlotPair feedback_ = VectorSlotPair();
};

typedef ZoneVector<DeoptimizationEntry> DeoptimizationVector;

class V8_EXPORT_PRIVATE PhiInstruction final
    : public NON_EXPORTED_BASE(ZoneObject) {
 public:
  typedef ZoneVector<InstructionOperand> Inputs;

  PhiInstruction(Zone* zone, int virtual_register, size_t input_count);

  void SetInput(size_t offset, int virtual_register);
  void RenameInput(size_t offset, int virtual_register);

  int virtual_register() const { return virtual_register_; }
  const IntVector& operands() const { return operands_; }

  // TODO(dcarney): this has no real business being here, since it's internal to
  // the register allocator, but putting it here was convenient.
  const InstructionOperand& output() const { return output_; }
  InstructionOperand& output() { return output_; }

 private:
  const int virtual_register_;
  InstructionOperand output_;
  IntVector operands_;
};


// Analogue of BasicBlock for Instructions instead of Nodes.
class V8_EXPORT_PRIVATE InstructionBlock final
    : public NON_EXPORTED_BASE(ZoneObject) {
 public:
  InstructionBlock(Zone* zone, RpoNumber rpo_number, RpoNumber loop_header,
                   RpoNumber loop_end, bool deferred, bool handler);

  // Instruction indexes (used by the register allocator).
  int first_instruction_index() const {
    DCHECK_LE(0, code_start_);
    DCHECK_LT(0, code_end_);
    DCHECK_GE(code_end_, code_start_);
    return code_start_;
  }
  int last_instruction_index() const {
    DCHECK_LE(0, code_start_);
    DCHECK_LT(0, code_end_);
    DCHECK_GE(code_end_, code_start_);
    return code_end_ - 1;
  }

  int32_t code_start() const { return code_start_; }
  void set_code_start(int32_t start) { code_start_ = start; }

  int32_t code_end() const { return code_end_; }
  void set_code_end(int32_t end) { code_end_ = end; }

  bool IsDeferred() const { return deferred_; }
  bool IsHandler() const { return handler_; }

  RpoNumber ao_number() const { return ao_number_; }
  RpoNumber rpo_number() const { return rpo_number_; }
  RpoNumber loop_header() const { return loop_header_; }
  RpoNumber loop_end() const {
    DCHECK(IsLoopHeader());
    return loop_end_;
  }
  inline bool IsLoopHeader() const { return loop_end_.IsValid(); }

  typedef ZoneVector<RpoNumber> Predecessors;
  Predecessors& predecessors() { return predecessors_; }
  const Predecessors& predecessors() const { return predecessors_; }
  size_t PredecessorCount() const { return predecessors_.size(); }
  size_t PredecessorIndexOf(RpoNumber rpo_number) const;

  typedef ZoneVector<RpoNumber> Successors;
  Successors& successors() { return successors_; }
  const Successors& successors() const { return successors_; }
  size_t SuccessorCount() const { return successors_.size(); }

  typedef ZoneVector<PhiInstruction*> PhiInstructions;
  const PhiInstructions& phis() const { return phis_; }
  PhiInstruction* PhiAt(size_t i) const { return phis_[i]; }
  void AddPhi(PhiInstruction* phi) { phis_.push_back(phi); }

  void set_ao_number(RpoNumber ao_number) { ao_number_ = ao_number; }

  bool needs_frame() const { return needs_frame_; }
  void mark_needs_frame() { needs_frame_ = true; }

  bool must_construct_frame() const { return must_construct_frame_; }
  void mark_must_construct_frame() { must_construct_frame_ = true; }

  bool must_deconstruct_frame() const { return must_deconstruct_frame_; }
  void mark_must_deconstruct_frame() { must_deconstruct_frame_ = true; }

 private:
  Successors successors_;
  Predecessors predecessors_;
  PhiInstructions phis_;
  RpoNumber ao_number_;  // Assembly order number.
  const RpoNumber rpo_number_;
  const RpoNumber loop_header_;
  const RpoNumber loop_end_;
  int32_t code_start_;   // start index of arch-specific code.
  int32_t code_end_;     // end index of arch-specific code.
  const bool deferred_;  // Block contains deferred code.
  const bool handler_;   // Block is a handler entry point.
  bool needs_frame_;
  bool must_construct_frame_;
  bool must_deconstruct_frame_;
};

class InstructionSequence;

struct PrintableInstructionBlock {
  const RegisterConfiguration* register_configuration_;
  const InstructionBlock* block_;
  const InstructionSequence* code_;
};

std::ostream& operator<<(std::ostream& os,
                         const PrintableInstructionBlock& printable_block);

typedef ZoneDeque<Constant> ConstantDeque;
typedef std::map<int, Constant, std::less<int>,
                 ZoneAllocator<std::pair<const int, Constant> > >
    ConstantMap;

typedef ZoneDeque<Instruction*> InstructionDeque;
typedef ZoneDeque<ReferenceMap*> ReferenceMapDeque;
typedef ZoneVector<InstructionBlock*> InstructionBlocks;


// Forward declarations.
struct PrintableInstructionSequence;


// Represents architecture-specific generated code before, during, and after
// register allocation.
class V8_EXPORT_PRIVATE InstructionSequence final
    : public NON_EXPORTED_BASE(ZoneObject) {
 public:
  static InstructionBlocks* InstructionBlocksFor(Zone* zone,
                                                 const Schedule* schedule);
  // Puts the deferred blocks last.
  static void ComputeAssemblyOrder(InstructionBlocks* blocks);

  InstructionSequence(Isolate* isolate, Zone* zone,
                      InstructionBlocks* instruction_blocks);

  int NextVirtualRegister();
  int VirtualRegisterCount() const { return next_virtual_register_; }

  const InstructionBlocks& instruction_blocks() const {
    return *instruction_blocks_;
  }

  int InstructionBlockCount() const {
    return static_cast<int>(instruction_blocks_->size());
  }

  InstructionBlock* InstructionBlockAt(RpoNumber rpo_number) {
    return instruction_blocks_->at(rpo_number.ToSize());
  }

  int LastLoopInstructionIndex(const InstructionBlock* block) {
    return instruction_blocks_->at(block->loop_end().ToSize() - 1)
        ->last_instruction_index();
  }

  const InstructionBlock* InstructionBlockAt(RpoNumber rpo_number) const {
    return instruction_blocks_->at(rpo_number.ToSize());
  }

  InstructionBlock* GetInstructionBlock(int instruction_index) const;

  static MachineRepresentation DefaultRepresentation() {
    return MachineType::PointerRepresentation();
  }
  MachineRepresentation GetRepresentation(int virtual_register) const;
  void MarkAsRepresentation(MachineRepresentation rep, int virtual_register);
  int representation_mask() const { return representation_mask_; }

  bool IsReference(int virtual_register) const {
    return CanBeTaggedPointer(GetRepresentation(virtual_register));
  }
  bool IsFP(int virtual_register) const {
    return IsFloatingPoint(GetRepresentation(virtual_register));
  }

  Instruction* GetBlockStart(RpoNumber rpo) const;

  typedef InstructionDeque::const_iterator const_iterator;
  const_iterator begin() const { return instructions_.begin(); }
  const_iterator end() const { return instructions_.end(); }
  const InstructionDeque& instructions() const { return instructions_; }
  int LastInstructionIndex() const {
    return static_cast<int>(instructions().size()) - 1;
  }

  Instruction* InstructionAt(int index) const {
    DCHECK_LE(0, index);
    DCHECK_GT(instructions_.size(), index);
    return instructions_[index];
  }

  Isolate* isolate() const { return isolate_; }
  const ReferenceMapDeque* reference_maps() const { return &reference_maps_; }
  Zone* zone() const { return zone_; }

  // Used by the instruction selector while adding instructions.
  int AddInstruction(Instruction* instr);
  void StartBlock(RpoNumber rpo);
  void EndBlock(RpoNumber rpo);

  int AddConstant(int virtual_register, Constant constant) {
    // TODO(titzer): allow RPO numbers as constants?
    DCHECK_NE(Constant::kRpoNumber, constant.type());
    DCHECK(virtual_register >= 0 && virtual_register < next_virtual_register_);
    DCHECK(constants_.find(virtual_register) == constants_.end());
    constants_.insert(std::make_pair(virtual_register, constant));
    return virtual_register;
  }
  Constant GetConstant(int virtual_register) const {
    ConstantMap::const_iterator it = constants_.find(virtual_register);
    DCHECK(it != constants_.end());
    DCHECK_EQ(virtual_register, it->first);
    return it->second;
  }

  typedef ZoneVector<Constant> Immediates;
  Immediates& immediates() { return immediates_; }

  ImmediateOperand AddImmediate(const Constant& constant) {
    if (constant.type() == Constant::kInt32 &&
        RelocInfo::IsNone(constant.rmode())) {
      return ImmediateOperand(ImmediateOperand::INLINE, constant.ToInt32());
    }
    int index = static_cast<int>(immediates_.size());
    immediates_.push_back(constant);
    return ImmediateOperand(ImmediateOperand::INDEXED, index);
  }

  Constant GetImmediate(const ImmediateOperand* op) const {
    switch (op->type()) {
      case ImmediateOperand::INLINE:
        return Constant(op->inline_value());
      case ImmediateOperand::INDEXED: {
        int index = op->indexed_value();
        DCHECK_LE(0, index);
        DCHECK_GT(immediates_.size(), index);
        return immediates_[index];
      }
    }
    UNREACHABLE();
  }

  int AddDeoptimizationEntry(FrameStateDescriptor* descriptor,
                             DeoptimizeKind kind, DeoptimizeReason reason,
                             VectorSlotPair const& feedback);
  DeoptimizationEntry const& GetDeoptimizationEntry(int deoptimization_id);
  int GetDeoptimizationEntryCount() const {
    return static_cast<int>(deoptimization_entries_.size());
  }

  RpoNumber InputRpo(Instruction* instr, size_t index);

  bool GetSourcePosition(const Instruction* instr,
                         SourcePosition* result) const;
  void SetSourcePosition(const Instruction* instr, SourcePosition value);

  bool ContainsCall() const {
    for (Instruction* instr : instructions_) {
      if (instr->IsCall()) return true;
    }
    return false;
  }

  // APIs to aid debugging. For general-stream APIs, use operator<<
  void Print(const RegisterConfiguration* config) const;
  void Print() const;

  void PrintBlock(const RegisterConfiguration* config, int block_id) const;
  void PrintBlock(int block_id) const;

  void ValidateEdgeSplitForm() const;
  void ValidateDeferredBlockExitPaths() const;
  void ValidateDeferredBlockEntryPaths() const;
  void ValidateSSA() const;

  static void SetRegisterConfigurationForTesting(
      const RegisterConfiguration* regConfig);
  static void ClearRegisterConfigurationForTesting();

 private:
  friend V8_EXPORT_PRIVATE std::ostream& operator<<(
      std::ostream& os, const PrintableInstructionSequence& code);

  typedef ZoneMap<const Instruction*, SourcePosition> SourcePositionMap;

  static const RegisterConfiguration* RegisterConfigurationForTesting();
  static const RegisterConfiguration* registerConfigurationForTesting_;

  Isolate* isolate_;
  Zone* const zone_;
  InstructionBlocks* const instruction_blocks_;
  SourcePositionMap source_positions_;
  ConstantMap constants_;
  Immediates immediates_;
  InstructionDeque instructions_;
  int next_virtual_register_;
  ReferenceMapDeque reference_maps_;
  ZoneVector<MachineRepresentation> representations_;
  int representation_mask_;
  DeoptimizationVector deoptimization_entries_;

  // Used at construction time
  InstructionBlock* current_block_;

  DISALLOW_COPY_AND_ASSIGN(InstructionSequence);
};


struct PrintableInstructionSequence {
  const RegisterConfiguration* register_configuration_;
  const InstructionSequence* sequence_;
};

V8_EXPORT_PRIVATE std::ostream& operator<<(
    std::ostream& os, const PrintableInstructionSequence& code);

}  // namespace compiler
}  // namespace internal
}  // namespace v8

#endif  // V8_COMPILER_INSTRUCTION_H_