//===- llvm/CodeGen/GlobalISel/LegalizerInfo.h ------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
/// Interface for Targets to specify which operations they can successfully
/// select and how the others should be expanded most efficiently.
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_GLOBALISEL_LEGALIZERINFO_H
#define LLVM_CODEGEN_GLOBALISEL_LEGALIZERINFO_H

#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/GlobalISel/LegacyLegalizerInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/LowLevelTypeImpl.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
#include <tuple>
#include <unordered_map>
#include <utility>

namespace llvm {

extern cl::opt<bool> DisableGISelLegalityCheck;

class LegalizerHelper;
class MachineInstr;
class MachineRegisterInfo;
class MCInstrInfo;
class GISelChangeObserver;

namespace LegalizeActions {
enum LegalizeAction : std::uint8_t {
  /// The operation is expected to be selectable directly by the target, and
  /// no transformation is necessary.
  Legal,

  /// The operation should be synthesized from multiple instructions acting on
  /// a narrower scalar base-type. For example a 64-bit add might be
  /// implemented in terms of 32-bit add-with-carry.
  NarrowScalar,

  /// The operation should be implemented in terms of a wider scalar
  /// base-type. For example a <2 x s8> add could be implemented as a <2
  /// x s32> add (ignoring the high bits).
  WidenScalar,

  /// The (vector) operation should be implemented by splitting it into
  /// sub-vectors where the operation is legal. For example a <8 x s64> add
  /// might be implemented as 4 separate <2 x s64> adds.
  FewerElements,

  /// The (vector) operation should be implemented by widening the input
  /// vector and ignoring the lanes added by doing so. For example <2 x i8> is
  /// rarely legal, but you might perform an <8 x i8> and then only look at
  /// the first two results.
  MoreElements,

  /// Perform the operation on a different, but equivalently sized type.
  Bitcast,

  /// The operation itself must be expressed in terms of simpler actions on
  /// this target. E.g. a SREM replaced by an SDIV and subtraction.
  Lower,

  /// The operation should be implemented as a call to some kind of runtime
  /// support library. For example this usually happens on machines that don't
  /// support floating-point operations natively.
  Libcall,

  /// The target wants to do something special with this combination of
  /// operand and type. A callback will be issued when it is needed.
  Custom,

  /// This operation is completely unsupported on the target. A programming
  /// error has occurred.
  Unsupported,

  /// Sentinel value for when no action was found in the specified table.
  NotFound,

  /// Fall back onto the old rules.
  /// TODO: Remove this once we've migrated
  UseLegacyRules,
};
} // end namespace LegalizeActions
raw_ostream &operator<<(raw_ostream &OS, LegalizeActions::LegalizeAction Action);

using LegalizeActions::LegalizeAction;

/// The LegalityQuery object bundles together all the information that's needed
/// to decide whether a given operation is legal or not.
/// For efficiency, it doesn't make a copy of Types so care must be taken not
/// to free it before using the query.
struct LegalityQuery {
  unsigned Opcode;
  ArrayRef<LLT> Types;

  struct MemDesc {
    LLT MemoryTy;
    uint64_t AlignInBits;
    AtomicOrdering Ordering;
  };

  /// Operations which require memory can use this to place requirements on the
  /// memory type for each MMO.
  ArrayRef<MemDesc> MMODescrs;

  constexpr LegalityQuery(unsigned Opcode, const ArrayRef<LLT> Types,
                          const ArrayRef<MemDesc> MMODescrs)
      : Opcode(Opcode), Types(Types), MMODescrs(MMODescrs) {}
  constexpr LegalityQuery(unsigned Opcode, const ArrayRef<LLT> Types)
      : LegalityQuery(Opcode, Types, {}) {}

  raw_ostream &print(raw_ostream &OS) const;
};

/// The result of a query. It either indicates a final answer of Legal or
/// Unsupported or describes an action that must be taken to make an operation
/// more legal.
struct LegalizeActionStep {
  /// The action to take or the final answer.
  LegalizeAction Action;
  /// If describing an action, the type index to change. Otherwise zero.
  unsigned TypeIdx;
  /// If describing an action, the new type for TypeIdx. Otherwise LLT{}.
  LLT NewType;

  LegalizeActionStep(LegalizeAction Action, unsigned TypeIdx,
                     const LLT NewType)
      : Action(Action), TypeIdx(TypeIdx), NewType(NewType) {}

  LegalizeActionStep(LegacyLegalizeActionStep Step)
      : TypeIdx(Step.TypeIdx), NewType(Step.NewType) {
    switch (Step.Action) {
    case LegacyLegalizeActions::Legal:
      Action = LegalizeActions::Legal;
      break;
    case LegacyLegalizeActions::NarrowScalar:
      Action = LegalizeActions::NarrowScalar;
      break;
    case LegacyLegalizeActions::WidenScalar:
      Action = LegalizeActions::WidenScalar;
      break;
    case LegacyLegalizeActions::FewerElements:
      Action = LegalizeActions::FewerElements;
      break;
    case LegacyLegalizeActions::MoreElements:
      Action = LegalizeActions::MoreElements;
      break;
    case LegacyLegalizeActions::Bitcast:
      Action = LegalizeActions::Bitcast;
      break;
    case LegacyLegalizeActions::Lower:
      Action = LegalizeActions::Lower;
      break;
    case LegacyLegalizeActions::Libcall:
      Action = LegalizeActions::Libcall;
      break;
    case LegacyLegalizeActions::Custom:
      Action = LegalizeActions::Custom;
      break;
    case LegacyLegalizeActions::Unsupported:
      Action = LegalizeActions::Unsupported;
      break;
    case LegacyLegalizeActions::NotFound:
      Action = LegalizeActions::NotFound;
      break;
    }
  }

  bool operator==(const LegalizeActionStep &RHS) const {
    return std::tie(Action, TypeIdx, NewType) ==
        std::tie(RHS.Action, RHS.TypeIdx, RHS.NewType);
  }
};

using LegalityPredicate = std::function<bool (const LegalityQuery &)>;
using LegalizeMutation =
    std::function<std::pair<unsigned, LLT>(const LegalityQuery &)>;

namespace LegalityPredicates {
struct TypePairAndMemDesc {
  LLT Type0;
  LLT Type1;
  LLT MemTy;
  uint64_t Align;

  bool operator==(const TypePairAndMemDesc &Other) const {
    return Type0 == Other.Type0 && Type1 == Other.Type1 &&
           Align == Other.Align && MemTy == Other.MemTy;
  }

  /// \returns true if this memory access is legal with for the access described
  /// by \p Other (The alignment is sufficient for the size and result type).
  bool isCompatible(const TypePairAndMemDesc &Other) const {
    return Type0 == Other.Type0 && Type1 == Other.Type1 &&
           Align >= Other.Align &&
           // FIXME: This perhaps should be stricter, but the current legality
           // rules are written only considering the size.
           MemTy.getSizeInBits() == Other.MemTy.getSizeInBits();
  }
};

/// True iff P0 and P1 are true.
template<typename Predicate>
Predicate all(Predicate P0, Predicate P1) {
  return [=](const LegalityQuery &Query) {
    return P0(Query) && P1(Query);
  };
}
/// True iff all given predicates are true.
template<typename Predicate, typename... Args>
Predicate all(Predicate P0, Predicate P1, Args... args) {
  return all(all(P0, P1), args...);
}

/// True iff P0 or P1 are true.
template<typename Predicate>
Predicate any(Predicate P0, Predicate P1) {
  return [=](const LegalityQuery &Query) {
    return P0(Query) || P1(Query);
  };
}
/// True iff any given predicates are true.
template<typename Predicate, typename... Args>
Predicate any(Predicate P0, Predicate P1, Args... args) {
  return any(any(P0, P1), args...);
}

/// True iff the given type index is the specified type.
LegalityPredicate typeIs(unsigned TypeIdx, LLT TypesInit);
/// True iff the given type index is one of the specified types.
LegalityPredicate typeInSet(unsigned TypeIdx,
                            std::initializer_list<LLT> TypesInit);

/// True iff the given type index is not the specified type.
inline LegalityPredicate typeIsNot(unsigned TypeIdx, LLT Type) {
  return [=](const LegalityQuery &Query) {
           return Query.Types[TypeIdx] != Type;
         };
}

/// True iff the given types for the given pair of type indexes is one of the
/// specified type pairs.
LegalityPredicate
typePairInSet(unsigned TypeIdx0, unsigned TypeIdx1,
              std::initializer_list<std::pair<LLT, LLT>> TypesInit);
/// True iff the given types for the given pair of type indexes is one of the
/// specified type pairs.
LegalityPredicate typePairAndMemDescInSet(
    unsigned TypeIdx0, unsigned TypeIdx1, unsigned MMOIdx,
    std::initializer_list<TypePairAndMemDesc> TypesAndMemDescInit);
/// True iff the specified type index is a scalar.
LegalityPredicate isScalar(unsigned TypeIdx);
/// True iff the specified type index is a vector.
LegalityPredicate isVector(unsigned TypeIdx);
/// True iff the specified type index is a pointer (with any address space).
LegalityPredicate isPointer(unsigned TypeIdx);
/// True iff the specified type index is a pointer with the specified address
/// space.
LegalityPredicate isPointer(unsigned TypeIdx, unsigned AddrSpace);

/// True if the type index is a vector with element type \p EltTy
LegalityPredicate elementTypeIs(unsigned TypeIdx, LLT EltTy);

/// True iff the specified type index is a scalar that's narrower than the given
/// size.
LegalityPredicate scalarNarrowerThan(unsigned TypeIdx, unsigned Size);

/// True iff the specified type index is a scalar that's wider than the given
/// size.
LegalityPredicate scalarWiderThan(unsigned TypeIdx, unsigned Size);

/// True iff the specified type index is a scalar or vector with an element type
/// that's narrower than the given size.
LegalityPredicate scalarOrEltNarrowerThan(unsigned TypeIdx, unsigned Size);

/// True iff the specified type index is a scalar or a vector with an element
/// type that's wider than the given size.
LegalityPredicate scalarOrEltWiderThan(unsigned TypeIdx, unsigned Size);

/// True iff the specified type index is a scalar whose size is not a power of
/// 2.
LegalityPredicate sizeNotPow2(unsigned TypeIdx);

/// True iff the specified type index is a scalar or vector whose element size
/// is not a power of 2.
LegalityPredicate scalarOrEltSizeNotPow2(unsigned TypeIdx);

/// True if the total bitwidth of the specified type index is \p Size bits.
LegalityPredicate sizeIs(unsigned TypeIdx, unsigned Size);

/// True iff the specified type indices are both the same bit size.
LegalityPredicate sameSize(unsigned TypeIdx0, unsigned TypeIdx1);

/// True iff the first type index has a larger total bit size than second type
/// index.
LegalityPredicate largerThan(unsigned TypeIdx0, unsigned TypeIdx1);

/// True iff the first type index has a smaller total bit size than second type
/// index.
LegalityPredicate smallerThan(unsigned TypeIdx0, unsigned TypeIdx1);

/// True iff the specified MMO index has a size that is not a power of 2
LegalityPredicate memSizeInBytesNotPow2(unsigned MMOIdx);
/// True iff the specified type index is a vector whose element count is not a
/// power of 2.
LegalityPredicate numElementsNotPow2(unsigned TypeIdx);
/// True iff the specified MMO index has at an atomic ordering of at Ordering or
/// stronger.
LegalityPredicate atomicOrderingAtLeastOrStrongerThan(unsigned MMOIdx,
                                                      AtomicOrdering Ordering);
} // end namespace LegalityPredicates

namespace LegalizeMutations {
/// Select this specific type for the given type index.
LegalizeMutation changeTo(unsigned TypeIdx, LLT Ty);

/// Keep the same type as the given type index.
LegalizeMutation changeTo(unsigned TypeIdx, unsigned FromTypeIdx);

/// Keep the same scalar or element type as the given type index.
LegalizeMutation changeElementTo(unsigned TypeIdx, unsigned FromTypeIdx);

/// Keep the same scalar or element type as the given type.
LegalizeMutation changeElementTo(unsigned TypeIdx, LLT Ty);

/// Change the scalar size or element size to have the same scalar size as type
/// index \p FromIndex. Unlike changeElementTo, this discards pointer types and
/// only changes the size.
LegalizeMutation changeElementSizeTo(unsigned TypeIdx, unsigned FromTypeIdx);

/// Widen the scalar type or vector element type for the given type index to the
/// next power of 2.
LegalizeMutation widenScalarOrEltToNextPow2(unsigned TypeIdx, unsigned Min = 0);

/// Add more elements to the type for the given type index to the next power of
/// 2.
LegalizeMutation moreElementsToNextPow2(unsigned TypeIdx, unsigned Min = 0);
/// Break up the vector type for the given type index into the element type.
LegalizeMutation scalarize(unsigned TypeIdx);
} // end namespace LegalizeMutations

/// A single rule in a legalizer info ruleset.
/// The specified action is chosen when the predicate is true. Where appropriate
/// for the action (e.g. for WidenScalar) the new type is selected using the
/// given mutator.
class LegalizeRule {
  LegalityPredicate Predicate;
  LegalizeAction Action;
  LegalizeMutation Mutation;

public:
  LegalizeRule(LegalityPredicate Predicate, LegalizeAction Action,
               LegalizeMutation Mutation = nullptr)
      : Predicate(Predicate), Action(Action), Mutation(Mutation) {}

  /// Test whether the LegalityQuery matches.
  bool match(const LegalityQuery &Query) const {
    return Predicate(Query);
  }

  LegalizeAction getAction() const { return Action; }

  /// Determine the change to make.
  std::pair<unsigned, LLT> determineMutation(const LegalityQuery &Query) const {
    if (Mutation)
      return Mutation(Query);
    return std::make_pair(0, LLT{});
  }
};

class LegalizeRuleSet {
  /// When non-zero, the opcode we are an alias of
  unsigned AliasOf;
  /// If true, there is another opcode that aliases this one
  bool IsAliasedByAnother;
  SmallVector<LegalizeRule, 2> Rules;

#ifndef NDEBUG
  /// If bit I is set, this rule set contains a rule that may handle (predicate
  /// or perform an action upon (or both)) the type index I. The uncertainty
  /// comes from free-form rules executing user-provided lambda functions. We
  /// conservatively assume such rules do the right thing and cover all type
  /// indices. The bitset is intentionally 1 bit wider than it absolutely needs
  /// to be to distinguish such cases from the cases where all type indices are
  /// individually handled.
  SmallBitVector TypeIdxsCovered{MCOI::OPERAND_LAST_GENERIC -
                                 MCOI::OPERAND_FIRST_GENERIC + 2};
  SmallBitVector ImmIdxsCovered{MCOI::OPERAND_LAST_GENERIC_IMM -
                                MCOI::OPERAND_FIRST_GENERIC_IMM + 2};
#endif

  unsigned typeIdx(unsigned TypeIdx) {
    assert(TypeIdx <=
               (MCOI::OPERAND_LAST_GENERIC - MCOI::OPERAND_FIRST_GENERIC) &&
           "Type Index is out of bounds");
#ifndef NDEBUG
    TypeIdxsCovered.set(TypeIdx);
#endif
    return TypeIdx;
  }

  unsigned immIdx(unsigned ImmIdx) {
    assert(ImmIdx <= (MCOI::OPERAND_LAST_GENERIC_IMM -
                      MCOI::OPERAND_FIRST_GENERIC_IMM) &&
           "Imm Index is out of bounds");
#ifndef NDEBUG
    ImmIdxsCovered.set(ImmIdx);
#endif
    return ImmIdx;
  }

  void markAllIdxsAsCovered() {
#ifndef NDEBUG
    TypeIdxsCovered.set();
    ImmIdxsCovered.set();
#endif
  }

  void add(const LegalizeRule &Rule) {
    assert(AliasOf == 0 &&
           "RuleSet is aliased, change the representative opcode instead");
    Rules.push_back(Rule);
  }

  static bool always(const LegalityQuery &) { return true; }

  /// Use the given action when the predicate is true.
  /// Action should not be an action that requires mutation.
  LegalizeRuleSet &actionIf(LegalizeAction Action,
                            LegalityPredicate Predicate) {
    add({Predicate, Action});
    return *this;
  }
  /// Use the given action when the predicate is true.
  /// Action should be an action that requires mutation.
  LegalizeRuleSet &actionIf(LegalizeAction Action, LegalityPredicate Predicate,
                            LegalizeMutation Mutation) {
    add({Predicate, Action, Mutation});
    return *this;
  }
  /// Use the given action when type index 0 is any type in the given list.
  /// Action should not be an action that requires mutation.
  LegalizeRuleSet &actionFor(LegalizeAction Action,
                             std::initializer_list<LLT> Types) {
    using namespace LegalityPredicates;
    return actionIf(Action, typeInSet(typeIdx(0), Types));
  }
  /// Use the given action when type index 0 is any type in the given list.
  /// Action should be an action that requires mutation.
  LegalizeRuleSet &actionFor(LegalizeAction Action,
                             std::initializer_list<LLT> Types,
                             LegalizeMutation Mutation) {
    using namespace LegalityPredicates;
    return actionIf(Action, typeInSet(typeIdx(0), Types), Mutation);
  }
  /// Use the given action when type indexes 0 and 1 is any type pair in the
  /// given list.
  /// Action should not be an action that requires mutation.
  LegalizeRuleSet &actionFor(LegalizeAction Action,
                             std::initializer_list<std::pair<LLT, LLT>> Types) {
    using namespace LegalityPredicates;
    return actionIf(Action, typePairInSet(typeIdx(0), typeIdx(1), Types));
  }
  /// Use the given action when type indexes 0 and 1 is any type pair in the
  /// given list.
  /// Action should be an action that requires mutation.
  LegalizeRuleSet &actionFor(LegalizeAction Action,
                             std::initializer_list<std::pair<LLT, LLT>> Types,
                             LegalizeMutation Mutation) {
    using namespace LegalityPredicates;
    return actionIf(Action, typePairInSet(typeIdx(0), typeIdx(1), Types),
                    Mutation);
  }
  /// Use the given action when type index 0 is any type in the given list and
  /// imm index 0 is anything. Action should not be an action that requires
  /// mutation.
  LegalizeRuleSet &actionForTypeWithAnyImm(LegalizeAction Action,
                                           std::initializer_list<LLT> Types) {
    using namespace LegalityPredicates;
    immIdx(0); // Inform verifier imm idx 0 is handled.
    return actionIf(Action, typeInSet(typeIdx(0), Types));
  }

  LegalizeRuleSet &actionForTypeWithAnyImm(
    LegalizeAction Action, std::initializer_list<std::pair<LLT, LLT>> Types) {
    using namespace LegalityPredicates;
    immIdx(0); // Inform verifier imm idx 0 is handled.
    return actionIf(Action, typePairInSet(typeIdx(0), typeIdx(1), Types));
  }

  /// Use the given action when type indexes 0 and 1 are both in the given list.
  /// That is, the type pair is in the cartesian product of the list.
  /// Action should not be an action that requires mutation.
  LegalizeRuleSet &actionForCartesianProduct(LegalizeAction Action,
                                             std::initializer_list<LLT> Types) {
    using namespace LegalityPredicates;
    return actionIf(Action, all(typeInSet(typeIdx(0), Types),
                                typeInSet(typeIdx(1), Types)));
  }
  /// Use the given action when type indexes 0 and 1 are both in their
  /// respective lists.
  /// That is, the type pair is in the cartesian product of the lists
  /// Action should not be an action that requires mutation.
  LegalizeRuleSet &
  actionForCartesianProduct(LegalizeAction Action,
                            std::initializer_list<LLT> Types0,
                            std::initializer_list<LLT> Types1) {
    using namespace LegalityPredicates;
    return actionIf(Action, all(typeInSet(typeIdx(0), Types0),
                                typeInSet(typeIdx(1), Types1)));
  }
  /// Use the given action when type indexes 0, 1, and 2 are all in their
  /// respective lists.
  /// That is, the type triple is in the cartesian product of the lists
  /// Action should not be an action that requires mutation.
  LegalizeRuleSet &actionForCartesianProduct(
      LegalizeAction Action, std::initializer_list<LLT> Types0,
      std::initializer_list<LLT> Types1, std::initializer_list<LLT> Types2) {
    using namespace LegalityPredicates;
    return actionIf(Action, all(typeInSet(typeIdx(0), Types0),
                                all(typeInSet(typeIdx(1), Types1),
                                    typeInSet(typeIdx(2), Types2))));
  }

public:
  LegalizeRuleSet() : AliasOf(0), IsAliasedByAnother(false), Rules() {}

  bool isAliasedByAnother() { return IsAliasedByAnother; }
  void setIsAliasedByAnother() { IsAliasedByAnother = true; }
  void aliasTo(unsigned Opcode) {
    assert((AliasOf == 0 || AliasOf == Opcode) &&
           "Opcode is already aliased to another opcode");
    assert(Rules.empty() && "Aliasing will discard rules");
    AliasOf = Opcode;
  }
  unsigned getAlias() const { return AliasOf; }

  /// The instruction is legal if predicate is true.
  LegalizeRuleSet &legalIf(LegalityPredicate Predicate) {
    // We have no choice but conservatively assume that the free-form
    // user-provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Legal, Predicate);
  }
  /// The instruction is legal when type index 0 is any type in the given list.
  LegalizeRuleSet &legalFor(std::initializer_list<LLT> Types) {
    return actionFor(LegalizeAction::Legal, Types);
  }
  /// The instruction is legal when type indexes 0 and 1 is any type pair in the
  /// given list.
  LegalizeRuleSet &legalFor(std::initializer_list<std::pair<LLT, LLT>> Types) {
    return actionFor(LegalizeAction::Legal, Types);
  }
  /// The instruction is legal when type index 0 is any type in the given list
  /// and imm index 0 is anything.
  LegalizeRuleSet &legalForTypeWithAnyImm(std::initializer_list<LLT> Types) {
    markAllIdxsAsCovered();
    return actionForTypeWithAnyImm(LegalizeAction::Legal, Types);
  }

  LegalizeRuleSet &legalForTypeWithAnyImm(
    std::initializer_list<std::pair<LLT, LLT>> Types) {
    markAllIdxsAsCovered();
    return actionForTypeWithAnyImm(LegalizeAction::Legal, Types);
  }

  /// The instruction is legal when type indexes 0 and 1 along with the memory
  /// size and minimum alignment is any type and size tuple in the given list.
  LegalizeRuleSet &legalForTypesWithMemDesc(
      std::initializer_list<LegalityPredicates::TypePairAndMemDesc>
          TypesAndMemDesc) {
    return actionIf(LegalizeAction::Legal,
                    LegalityPredicates::typePairAndMemDescInSet(
                        typeIdx(0), typeIdx(1), /*MMOIdx*/ 0, TypesAndMemDesc));
  }
  /// The instruction is legal when type indexes 0 and 1 are both in the given
  /// list. That is, the type pair is in the cartesian product of the list.
  LegalizeRuleSet &legalForCartesianProduct(std::initializer_list<LLT> Types) {
    return actionForCartesianProduct(LegalizeAction::Legal, Types);
  }
  /// The instruction is legal when type indexes 0 and 1 are both their
  /// respective lists.
  LegalizeRuleSet &legalForCartesianProduct(std::initializer_list<LLT> Types0,
                                            std::initializer_list<LLT> Types1) {
    return actionForCartesianProduct(LegalizeAction::Legal, Types0, Types1);
  }
  /// The instruction is legal when type indexes 0, 1, and 2 are both their
  /// respective lists.
  LegalizeRuleSet &legalForCartesianProduct(std::initializer_list<LLT> Types0,
                                            std::initializer_list<LLT> Types1,
                                            std::initializer_list<LLT> Types2) {
    return actionForCartesianProduct(LegalizeAction::Legal, Types0, Types1,
                                     Types2);
  }

  LegalizeRuleSet &alwaysLegal() {
    using namespace LegalizeMutations;
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Legal, always);
  }

  /// The specified type index is coerced if predicate is true.
  LegalizeRuleSet &bitcastIf(LegalityPredicate Predicate,
                             LegalizeMutation Mutation) {
    // We have no choice but conservatively assume that lowering with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Bitcast, Predicate, Mutation);
  }

  /// The instruction is lowered.
  LegalizeRuleSet &lower() {
    using namespace LegalizeMutations;
    // We have no choice but conservatively assume that predicate-less lowering
    // properly handles all type indices by design:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Lower, always);
  }
  /// The instruction is lowered if predicate is true. Keep type index 0 as the
  /// same type.
  LegalizeRuleSet &lowerIf(LegalityPredicate Predicate) {
    using namespace LegalizeMutations;
    // We have no choice but conservatively assume that lowering with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Lower, Predicate);
  }
  /// The instruction is lowered if predicate is true.
  LegalizeRuleSet &lowerIf(LegalityPredicate Predicate,
                           LegalizeMutation Mutation) {
    // We have no choice but conservatively assume that lowering with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Lower, Predicate, Mutation);
  }
  /// The instruction is lowered when type index 0 is any type in the given
  /// list. Keep type index 0 as the same type.
  LegalizeRuleSet &lowerFor(std::initializer_list<LLT> Types) {
    return actionFor(LegalizeAction::Lower, Types);
  }
  /// The instruction is lowered when type index 0 is any type in the given
  /// list.
  LegalizeRuleSet &lowerFor(std::initializer_list<LLT> Types,
                            LegalizeMutation Mutation) {
    return actionFor(LegalizeAction::Lower, Types, Mutation);
  }
  /// The instruction is lowered when type indexes 0 and 1 is any type pair in
  /// the given list. Keep type index 0 as the same type.
  LegalizeRuleSet &lowerFor(std::initializer_list<std::pair<LLT, LLT>> Types) {
    return actionFor(LegalizeAction::Lower, Types);
  }
  /// The instruction is lowered when type indexes 0 and 1 is any type pair in
  /// the given list.
  LegalizeRuleSet &lowerFor(std::initializer_list<std::pair<LLT, LLT>> Types,
                            LegalizeMutation Mutation) {
    return actionFor(LegalizeAction::Lower, Types, Mutation);
  }
  /// The instruction is lowered when type indexes 0 and 1 are both in their
  /// respective lists.
  LegalizeRuleSet &lowerForCartesianProduct(std::initializer_list<LLT> Types0,
                                            std::initializer_list<LLT> Types1) {
    using namespace LegalityPredicates;
    return actionForCartesianProduct(LegalizeAction::Lower, Types0, Types1);
  }
  /// The instruction is lowered when when type indexes 0, 1, and 2 are all in
  /// their respective lists.
  LegalizeRuleSet &lowerForCartesianProduct(std::initializer_list<LLT> Types0,
                                            std::initializer_list<LLT> Types1,
                                            std::initializer_list<LLT> Types2) {
    using namespace LegalityPredicates;
    return actionForCartesianProduct(LegalizeAction::Lower, Types0, Types1,
                                     Types2);
  }

  /// The instruction is emitted as a library call.
  LegalizeRuleSet &libcall() {
    using namespace LegalizeMutations;
    // We have no choice but conservatively assume that predicate-less lowering
    // properly handles all type indices by design:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Libcall, always);
  }

  /// Like legalIf, but for the Libcall action.
  LegalizeRuleSet &libcallIf(LegalityPredicate Predicate) {
    // We have no choice but conservatively assume that a libcall with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Libcall, Predicate);
  }
  LegalizeRuleSet &libcallFor(std::initializer_list<LLT> Types) {
    return actionFor(LegalizeAction::Libcall, Types);
  }
  LegalizeRuleSet &
  libcallFor(std::initializer_list<std::pair<LLT, LLT>> Types) {
    return actionFor(LegalizeAction::Libcall, Types);
  }
  LegalizeRuleSet &
  libcallForCartesianProduct(std::initializer_list<LLT> Types) {
    return actionForCartesianProduct(LegalizeAction::Libcall, Types);
  }
  LegalizeRuleSet &
  libcallForCartesianProduct(std::initializer_list<LLT> Types0,
                             std::initializer_list<LLT> Types1) {
    return actionForCartesianProduct(LegalizeAction::Libcall, Types0, Types1);
  }

  /// Widen the scalar to the one selected by the mutation if the predicate is
  /// true.
  LegalizeRuleSet &widenScalarIf(LegalityPredicate Predicate,
                                 LegalizeMutation Mutation) {
    // We have no choice but conservatively assume that an action with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::WidenScalar, Predicate, Mutation);
  }
  /// Narrow the scalar to the one selected by the mutation if the predicate is
  /// true.
  LegalizeRuleSet &narrowScalarIf(LegalityPredicate Predicate,
                                  LegalizeMutation Mutation) {
    // We have no choice but conservatively assume that an action with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::NarrowScalar, Predicate, Mutation);
  }
  /// Narrow the scalar, specified in mutation, when type indexes 0 and 1 is any
  /// type pair in the given list.
  LegalizeRuleSet &
  narrowScalarFor(std::initializer_list<std::pair<LLT, LLT>> Types,
                  LegalizeMutation Mutation) {
    return actionFor(LegalizeAction::NarrowScalar, Types, Mutation);
  }

  /// Add more elements to reach the type selected by the mutation if the
  /// predicate is true.
  LegalizeRuleSet &moreElementsIf(LegalityPredicate Predicate,
                                  LegalizeMutation Mutation) {
    // We have no choice but conservatively assume that an action with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::MoreElements, Predicate, Mutation);
  }
  /// Remove elements to reach the type selected by the mutation if the
  /// predicate is true.
  LegalizeRuleSet &fewerElementsIf(LegalityPredicate Predicate,
                                   LegalizeMutation Mutation) {
    // We have no choice but conservatively assume that an action with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::FewerElements, Predicate, Mutation);
  }

  /// The instruction is unsupported.
  LegalizeRuleSet &unsupported() {
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Unsupported, always);
  }
  LegalizeRuleSet &unsupportedIf(LegalityPredicate Predicate) {
    return actionIf(LegalizeAction::Unsupported, Predicate);
  }

  LegalizeRuleSet &unsupportedFor(std::initializer_list<LLT> Types) {
    return actionFor(LegalizeAction::Unsupported, Types);
  }

  LegalizeRuleSet &unsupportedIfMemSizeNotPow2() {
    return actionIf(LegalizeAction::Unsupported,
                    LegalityPredicates::memSizeInBytesNotPow2(0));
  }
  LegalizeRuleSet &lowerIfMemSizeNotPow2() {
    return actionIf(LegalizeAction::Lower,
                    LegalityPredicates::memSizeInBytesNotPow2(0));
  }

  LegalizeRuleSet &customIf(LegalityPredicate Predicate) {
    // We have no choice but conservatively assume that a custom action with a
    // free-form user provided Predicate properly handles all type indices:
    markAllIdxsAsCovered();
    return actionIf(LegalizeAction::Custom, Predicate);
  }
  LegalizeRuleSet &customFor(std::initializer_list<LLT> Types) {
    return actionFor(LegalizeAction::Custom, Types);
  }

  /// The instruction is custom when type indexes 0 and 1 is any type pair in the
  /// given list.
  LegalizeRuleSet &customFor(std::initializer_list<std::pair<LLT, LLT>> Types) {
    return actionFor(LegalizeAction::Custom, Types);
  }

  LegalizeRuleSet &customForCartesianProduct(std::initializer_list<LLT> Types) {
    return actionForCartesianProduct(LegalizeAction::Custom, Types);
  }
  LegalizeRuleSet &
  customForCartesianProduct(std::initializer_list<LLT> Types0,
                            std::initializer_list<LLT> Types1) {
    return actionForCartesianProduct(LegalizeAction::Custom, Types0, Types1);
  }

  /// Unconditionally custom lower.
  LegalizeRuleSet &custom() {
    return customIf(always);
  }

  /// Widen the scalar to the next power of two that is at least MinSize.
  /// No effect if the type is not a scalar or is a power of two.
  LegalizeRuleSet &widenScalarToNextPow2(unsigned TypeIdx,
                                         unsigned MinSize = 0) {
    using namespace LegalityPredicates;
    return actionIf(
        LegalizeAction::WidenScalar, sizeNotPow2(typeIdx(TypeIdx)),
        LegalizeMutations::widenScalarOrEltToNextPow2(TypeIdx, MinSize));
  }

  /// Widen the scalar or vector element type to the next power of two that is
  /// at least MinSize.  No effect if the scalar size is a power of two.
  LegalizeRuleSet &widenScalarOrEltToNextPow2(unsigned TypeIdx,
                                              unsigned MinSize = 0) {
    using namespace LegalityPredicates;
    return actionIf(
        LegalizeAction::WidenScalar, scalarOrEltSizeNotPow2(typeIdx(TypeIdx)),
        LegalizeMutations::widenScalarOrEltToNextPow2(TypeIdx, MinSize));
  }

  LegalizeRuleSet &narrowScalar(unsigned TypeIdx, LegalizeMutation Mutation) {
    using namespace LegalityPredicates;
    return actionIf(LegalizeAction::NarrowScalar, isScalar(typeIdx(TypeIdx)),
                    Mutation);
  }

  LegalizeRuleSet &scalarize(unsigned TypeIdx) {
    using namespace LegalityPredicates;
    return actionIf(LegalizeAction::FewerElements, isVector(typeIdx(TypeIdx)),
                    LegalizeMutations::scalarize(TypeIdx));
  }

  LegalizeRuleSet &scalarizeIf(LegalityPredicate Predicate, unsigned TypeIdx) {
    using namespace LegalityPredicates;
    return actionIf(LegalizeAction::FewerElements,
                    all(Predicate, isVector(typeIdx(TypeIdx))),
                    LegalizeMutations::scalarize(TypeIdx));
  }

  /// Ensure the scalar or element is at least as wide as Ty.
  LegalizeRuleSet &minScalarOrElt(unsigned TypeIdx, const LLT Ty) {
    using namespace LegalityPredicates;
    using namespace LegalizeMutations;
    return actionIf(LegalizeAction::WidenScalar,
                    scalarOrEltNarrowerThan(TypeIdx, Ty.getScalarSizeInBits()),
                    changeElementTo(typeIdx(TypeIdx), Ty));
  }

  /// Ensure the scalar or element is at least as wide as Ty.
  LegalizeRuleSet &minScalarOrEltIf(LegalityPredicate Predicate,
                                    unsigned TypeIdx, const LLT Ty) {
    using namespace LegalityPredicates;
    using namespace LegalizeMutations;
    return actionIf(LegalizeAction::WidenScalar,
                    all(Predicate, scalarOrEltNarrowerThan(
                                       TypeIdx, Ty.getScalarSizeInBits())),
                    changeElementTo(typeIdx(TypeIdx), Ty));
  }

  /// Ensure the scalar is at least as wide as Ty.
  LegalizeRuleSet &minScalar(unsigned TypeIdx, const LLT Ty) {
    using namespace LegalityPredicates;
    using namespace LegalizeMutations;
    return actionIf(LegalizeAction::WidenScalar,
                    scalarNarrowerThan(TypeIdx, Ty.getSizeInBits()),
                    changeTo(typeIdx(TypeIdx), Ty));
  }

  /// Ensure the scalar is at most as wide as Ty.
  LegalizeRuleSet &maxScalarOrElt(unsigned TypeIdx, const LLT Ty) {
    using namespace LegalityPredicates;
    using namespace LegalizeMutations;
    return actionIf(LegalizeAction::NarrowScalar,
                    scalarOrEltWiderThan(TypeIdx, Ty.getScalarSizeInBits()),
                    changeElementTo(typeIdx(TypeIdx), Ty));
  }

  /// Ensure the scalar is at most as wide as Ty.
  LegalizeRuleSet &maxScalar(unsigned TypeIdx, const LLT Ty) {
    using namespace LegalityPredicates;
    using namespace LegalizeMutations;
    return actionIf(LegalizeAction::NarrowScalar,
                    scalarWiderThan(TypeIdx, Ty.getSizeInBits()),
                    changeTo(typeIdx(TypeIdx), Ty));
  }

  /// Conditionally limit the maximum size of the scalar.
  /// For example, when the maximum size of one type depends on the size of
  /// another such as extracting N bits from an M bit container.
  LegalizeRuleSet &maxScalarIf(LegalityPredicate Predicate, unsigned TypeIdx,
                               const LLT Ty) {
    using namespace LegalityPredicates;
    using namespace LegalizeMutations;
    return actionIf(
        LegalizeAction::NarrowScalar,
        [=](const LegalityQuery &Query) {
          const LLT QueryTy = Query.Types[TypeIdx];
          return QueryTy.isScalar() &&
                 QueryTy.getSizeInBits() > Ty.getSizeInBits() &&
                 Predicate(Query);
        },
        changeElementTo(typeIdx(TypeIdx), Ty));
  }

  /// Limit the range of scalar sizes to MinTy and MaxTy.
  LegalizeRuleSet &clampScalar(unsigned TypeIdx, const LLT MinTy,
                               const LLT MaxTy) {
    assert(MinTy.isScalar() && MaxTy.isScalar() && "Expected scalar types");
    return minScalar(TypeIdx, MinTy).maxScalar(TypeIdx, MaxTy);
  }

  /// Limit the range of scalar sizes to MinTy and MaxTy.
  LegalizeRuleSet &clampScalarOrElt(unsigned TypeIdx, const LLT MinTy,
                                    const LLT MaxTy) {
    return minScalarOrElt(TypeIdx, MinTy).maxScalarOrElt(TypeIdx, MaxTy);
  }

  /// Widen the scalar to match the size of another.
  LegalizeRuleSet &minScalarSameAs(unsigned TypeIdx, unsigned LargeTypeIdx) {
    typeIdx(TypeIdx);
    return widenScalarIf(
        [=](const LegalityQuery &Query) {
          return Query.Types[LargeTypeIdx].getScalarSizeInBits() >
                 Query.Types[TypeIdx].getSizeInBits();
        },
        LegalizeMutations::changeElementSizeTo(TypeIdx, LargeTypeIdx));
  }

  /// Narrow the scalar to match the size of another.
  LegalizeRuleSet &maxScalarSameAs(unsigned TypeIdx, unsigned NarrowTypeIdx) {
    typeIdx(TypeIdx);
    return narrowScalarIf(
        [=](const LegalityQuery &Query) {
          return Query.Types[NarrowTypeIdx].getScalarSizeInBits() <
                 Query.Types[TypeIdx].getSizeInBits();
        },
        LegalizeMutations::changeElementSizeTo(TypeIdx, NarrowTypeIdx));
  }

  /// Change the type \p TypeIdx to have the same scalar size as type \p
  /// SameSizeIdx.
  LegalizeRuleSet &scalarSameSizeAs(unsigned TypeIdx, unsigned SameSizeIdx) {
    return minScalarSameAs(TypeIdx, SameSizeIdx)
          .maxScalarSameAs(TypeIdx, SameSizeIdx);
  }

  /// Conditionally widen the scalar or elt to match the size of another.
  LegalizeRuleSet &minScalarEltSameAsIf(LegalityPredicate Predicate,
                                   unsigned TypeIdx, unsigned LargeTypeIdx) {
    typeIdx(TypeIdx);
    return widenScalarIf(
        [=](const LegalityQuery &Query) {
          return Query.Types[LargeTypeIdx].getScalarSizeInBits() >
                     Query.Types[TypeIdx].getScalarSizeInBits() &&
                 Predicate(Query);
        },
        [=](const LegalityQuery &Query) {
          LLT T = Query.Types[LargeTypeIdx];
          return std::make_pair(TypeIdx, T);
        });
  }

  /// Conditionally narrow the scalar or elt to match the size of another.
  LegalizeRuleSet &maxScalarEltSameAsIf(LegalityPredicate Predicate,
                                        unsigned TypeIdx,
                                        unsigned SmallTypeIdx) {
    typeIdx(TypeIdx);
    return narrowScalarIf(
        [=](const LegalityQuery &Query) {
          return Query.Types[SmallTypeIdx].getScalarSizeInBits() <
                     Query.Types[TypeIdx].getScalarSizeInBits() &&
                 Predicate(Query);
        },
        [=](const LegalityQuery &Query) {
          LLT T = Query.Types[SmallTypeIdx];
          return std::make_pair(TypeIdx, T);
        });
  }

  /// Add more elements to the vector to reach the next power of two.
  /// No effect if the type is not a vector or the element count is a power of
  /// two.
  LegalizeRuleSet &moreElementsToNextPow2(unsigned TypeIdx) {
    using namespace LegalityPredicates;
    return actionIf(LegalizeAction::MoreElements,
                    numElementsNotPow2(typeIdx(TypeIdx)),
                    LegalizeMutations::moreElementsToNextPow2(TypeIdx));
  }

  /// Limit the number of elements in EltTy vectors to at least MinElements.
  LegalizeRuleSet &clampMinNumElements(unsigned TypeIdx, const LLT EltTy,
                                       unsigned MinElements) {
    // Mark the type index as covered:
    typeIdx(TypeIdx);
    return actionIf(
        LegalizeAction::MoreElements,
        [=](const LegalityQuery &Query) {
          LLT VecTy = Query.Types[TypeIdx];
          return VecTy.isVector() && VecTy.getElementType() == EltTy &&
                 VecTy.getNumElements() < MinElements;
        },
        [=](const LegalityQuery &Query) {
          LLT VecTy = Query.Types[TypeIdx];
          return std::make_pair(
              TypeIdx, LLT::fixed_vector(MinElements, VecTy.getElementType()));
        });
  }
  /// Limit the number of elements in EltTy vectors to at most MaxElements.
  LegalizeRuleSet &clampMaxNumElements(unsigned TypeIdx, const LLT EltTy,
                                       unsigned MaxElements) {
    // Mark the type index as covered:
    typeIdx(TypeIdx);
    return actionIf(
        LegalizeAction::FewerElements,
        [=](const LegalityQuery &Query) {
          LLT VecTy = Query.Types[TypeIdx];
          return VecTy.isVector() && VecTy.getElementType() == EltTy &&
                 VecTy.getNumElements() > MaxElements;
        },
        [=](const LegalityQuery &Query) {
          LLT VecTy = Query.Types[TypeIdx];
          LLT NewTy = LLT::scalarOrVector(ElementCount::getFixed(MaxElements),
                                          VecTy.getElementType());
          return std::make_pair(TypeIdx, NewTy);
        });
  }
  /// Limit the number of elements for the given vectors to at least MinTy's
  /// number of elements and at most MaxTy's number of elements.
  ///
  /// No effect if the type is not a vector or does not have the same element
  /// type as the constraints.
  /// The element type of MinTy and MaxTy must match.
  LegalizeRuleSet &clampNumElements(unsigned TypeIdx, const LLT MinTy,
                                    const LLT MaxTy) {
    assert(MinTy.getElementType() == MaxTy.getElementType() &&
           "Expected element types to agree");

    const LLT EltTy = MinTy.getElementType();
    return clampMinNumElements(TypeIdx, EltTy, MinTy.getNumElements())
        .clampMaxNumElements(TypeIdx, EltTy, MaxTy.getNumElements());
  }

  /// Fallback on the previous implementation. This should only be used while
  /// porting a rule.
  LegalizeRuleSet &fallback() {
    add({always, LegalizeAction::UseLegacyRules});
    return *this;
  }

  /// Check if there is no type index which is obviously not handled by the
  /// LegalizeRuleSet in any way at all.
  /// \pre Type indices of the opcode form a dense [0, \p NumTypeIdxs) set.
  bool verifyTypeIdxsCoverage(unsigned NumTypeIdxs) const;
  /// Check if there is no imm index which is obviously not handled by the
  /// LegalizeRuleSet in any way at all.
  /// \pre Type indices of the opcode form a dense [0, \p NumTypeIdxs) set.
  bool verifyImmIdxsCoverage(unsigned NumImmIdxs) const;

  /// Apply the ruleset to the given LegalityQuery.
  LegalizeActionStep apply(const LegalityQuery &Query) const;
};

class LegalizerInfo {
public:
  virtual ~LegalizerInfo() = default;

  const LegacyLegalizerInfo &getLegacyLegalizerInfo() const {
    return LegacyInfo;
  }
  LegacyLegalizerInfo &getLegacyLegalizerInfo() { return LegacyInfo; }

  unsigned getOpcodeIdxForOpcode(unsigned Opcode) const;
  unsigned getActionDefinitionsIdx(unsigned Opcode) const;

  /// Perform simple self-diagnostic and assert if there is anything obviously
  /// wrong with the actions set up.
  void verify(const MCInstrInfo &MII) const;

  /// Get the action definitions for the given opcode. Use this to run a
  /// LegalityQuery through the definitions.
  const LegalizeRuleSet &getActionDefinitions(unsigned Opcode) const;

  /// Get the action definition builder for the given opcode. Use this to define
  /// the action definitions.
  ///
  /// It is an error to request an opcode that has already been requested by the
  /// multiple-opcode variant.
  LegalizeRuleSet &getActionDefinitionsBuilder(unsigned Opcode);

  /// Get the action definition builder for the given set of opcodes. Use this
  /// to define the action definitions for multiple opcodes at once. The first
  /// opcode given will be considered the representative opcode and will hold
  /// the definitions whereas the other opcodes will be configured to refer to
  /// the representative opcode. This lowers memory requirements and very
  /// slightly improves performance.
  ///
  /// It would be very easy to introduce unexpected side-effects as a result of
  /// this aliasing if it were permitted to request different but intersecting
  /// sets of opcodes but that is difficult to keep track of. It is therefore an
  /// error to request the same opcode twice using this API, to request an
  /// opcode that already has definitions, or to use the single-opcode API on an
  /// opcode that has already been requested by this API.
  LegalizeRuleSet &
  getActionDefinitionsBuilder(std::initializer_list<unsigned> Opcodes);
  void aliasActionDefinitions(unsigned OpcodeTo, unsigned OpcodeFrom);

  /// Determine what action should be taken to legalize the described
  /// instruction. Requires computeTables to have been called.
  ///
  /// \returns a description of the next legalization step to perform.
  LegalizeActionStep getAction(const LegalityQuery &Query) const;

  /// Determine what action should be taken to legalize the given generic
  /// instruction.
  ///
  /// \returns a description of the next legalization step to perform.
  LegalizeActionStep getAction(const MachineInstr &MI,
                               const MachineRegisterInfo &MRI) const;

  bool isLegal(const LegalityQuery &Query) const {
    return getAction(Query).Action == LegalizeAction::Legal;
  }

  bool isLegalOrCustom(const LegalityQuery &Query) const {
    auto Action = getAction(Query).Action;
    return Action == LegalizeAction::Legal || Action == LegalizeAction::Custom;
  }

  bool isLegal(const MachineInstr &MI, const MachineRegisterInfo &MRI) const;
  bool isLegalOrCustom(const MachineInstr &MI,
                       const MachineRegisterInfo &MRI) const;

  /// Called for instructions with the Custom LegalizationAction.
  virtual bool legalizeCustom(LegalizerHelper &Helper,
                              MachineInstr &MI) const {
    llvm_unreachable("must implement this if custom action is used");
  }

  /// \returns true if MI is either legal or has been legalized and false if not
  /// legal.
  /// Return true if MI is either legal or has been legalized and false
  /// if not legal.
  virtual bool legalizeIntrinsic(LegalizerHelper &Helper,
                                 MachineInstr &MI) const {
    return true;
  }

  /// Return the opcode (SEXT/ZEXT/ANYEXT) that should be performed while
  /// widening a constant of type SmallTy which targets can override.
  /// For eg, the DAG does (SmallTy.isByteSized() ? G_SEXT : G_ZEXT) which
  /// will be the default.
  virtual unsigned getExtOpcodeForWideningConstant(LLT SmallTy) const;

private:
  static const int FirstOp = TargetOpcode::PRE_ISEL_GENERIC_OPCODE_START;
  static const int LastOp = TargetOpcode::PRE_ISEL_GENERIC_OPCODE_END;

  LegalizeRuleSet RulesForOpcode[LastOp - FirstOp + 1];
  LegacyLegalizerInfo LegacyInfo;
};

#ifndef NDEBUG
/// Checks that MIR is fully legal, returns an illegal instruction if it's not,
/// nullptr otherwise
const MachineInstr *machineFunctionIsIllegal(const MachineFunction &MF);
#endif

} // end namespace llvm.

#endif // LLVM_CODEGEN_GLOBALISEL_LEGALIZERINFO_H