OpDefinition.h

//===- OpDefinition.h - Classes for defining concrete Op types --*- 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
//
//===----------------------------------------------------------------------===//
//
// This file implements helper classes for implementing the "Op" types.  This
// includes the Op type, which is the base class for Op class definitions,
// as well as number of traits in the OpTrait namespace that provide a
// declarative way to specify properties of Ops.
//
// The purpose of these types are to allow light-weight implementation of
// concrete ops (like DimOp) with very little boilerplate.
//
//===----------------------------------------------------------------------===//

#ifndef MLIR_IR_OPDEFINITION_H
#define MLIR_IR_OPDEFINITION_H

#include "mlir/IR/Operation.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
#include <type_traits>

namespace mlir {
class Builder;
class OpBuilder;

namespace OpTrait {
template <typename ConcreteType> class OneResult;
}

/// This class represents success/failure for operation parsing. It is
/// essentially a simple wrapper class around LogicalResult that allows for
/// explicit conversion to bool. This allows for the parser to chain together
/// parse rules without the clutter of "failed/succeeded".
class ParseResult : public LogicalResult {
public:
  ParseResult(LogicalResult result = success()) : LogicalResult(result) {}

  // Allow diagnostics emitted during parsing to be converted to failure.
  ParseResult(const InFlightDiagnostic &) : LogicalResult(failure()) {}
  ParseResult(const Diagnostic &) : LogicalResult(failure()) {}

  /// Failure is true in a boolean context.
  explicit operator bool() const { return failed(*this); }
};
/// This class implements `Optional` functionality for ParseResult. We don't
/// directly use Optional here, because it provides an implicit conversion
/// to 'bool' which we want to avoid. This class is used to implement tri-state
/// 'parseOptional' functions that may have a failure mode when parsing that
/// shouldn't be attributed to "not present".
class OptionalParseResult {
public:
  OptionalParseResult() = default;
  OptionalParseResult(LogicalResult result) : impl(result) {}
  OptionalParseResult(ParseResult result) : impl(result) {}
  OptionalParseResult(const InFlightDiagnostic &)
      : OptionalParseResult(failure()) {}
  OptionalParseResult(llvm::NoneType) : impl(llvm::None) {}

  /// Returns true if we contain a valid ParseResult value.
  bool hasValue() const { return impl.hasValue(); }

  /// Access the internal ParseResult value.
  ParseResult getValue() const { return impl.getValue(); }
  ParseResult operator*() const { return getValue(); }

private:
  Optional<ParseResult> impl;
};

// These functions are out-of-line utilities, which avoids them being template
// instantiated/duplicated.
namespace impl {
/// Insert an operation, generated by `buildTerminatorOp`, at the end of the
/// region's only block if it does not have a terminator already. If the region
/// is empty, insert a new block first. `buildTerminatorOp` should return the
/// terminator operation to insert.
void ensureRegionTerminator(
    Region &region, OpBuilder &builder, Location loc,
    function_ref<Operation *(OpBuilder &, Location)> buildTerminatorOp);
void ensureRegionTerminator(
    Region &region, Builder &builder, Location loc,
    function_ref<Operation *(OpBuilder &, Location)> buildTerminatorOp);

} // namespace impl

/// This is the concrete base class that holds the operation pointer and has
/// non-generic methods that only depend on State (to avoid having them
/// instantiated on template types that don't affect them.
///
/// This also has the fallback implementations of customization hooks for when
/// they aren't customized.
class OpState {
public:
  /// Ops are pointer-like, so we allow implicit conversion to bool.
  operator bool() { return getOperation() != nullptr; }

  /// This implicitly converts to Operation*.
  operator Operation *() const { return state; }

  /// Return the operation that this refers to.
  Operation *getOperation() { return state; }

  /// Returns the closest surrounding operation that contains this operation
  /// or nullptr if this is a top-level operation.
  Operation *getParentOp() { return getOperation()->getParentOp(); }

  /// Return the closest surrounding parent operation that is of type 'OpTy'.
  template <typename OpTy> OpTy getParentOfType() {
    return getOperation()->getParentOfType<OpTy>();
  }

  /// Returns the closest surrounding parent operation with trait `Trait`.
  template <template <typename T> class Trait>
  Operation *getParentWithTrait() {
    return getOperation()->getParentWithTrait<Trait>();
  }

  /// Return the context this operation belongs to.
  MLIRContext *getContext() { return getOperation()->getContext(); }

  /// Print the operation to the given stream.
  void print(raw_ostream &os, OpPrintingFlags flags = llvm::None) {
    state->print(os, flags);
  }
  void print(raw_ostream &os, AsmState &asmState,
             OpPrintingFlags flags = llvm::None) {
    state->print(os, asmState, flags);
  }

  /// Dump this operation.
  void dump() { state->dump(); }

  /// The source location the operation was defined or derived from.
  Location getLoc() { return state->getLoc(); }
  void setLoc(Location loc) { state->setLoc(loc); }

  /// Return all of the attributes on this operation.
  ArrayRef<NamedAttribute> getAttrs() { return state->getAttrs(); }

  /// A utility iterator that filters out non-dialect attributes.
  using dialect_attr_iterator = Operation::dialect_attr_iterator;
  using dialect_attr_range = Operation::dialect_attr_range;

  /// Return a range corresponding to the dialect attributes for this operation.
  dialect_attr_range getDialectAttrs() { return state->getDialectAttrs(); }
  dialect_attr_iterator dialect_attr_begin() {
    return state->dialect_attr_begin();
  }
  dialect_attr_iterator dialect_attr_end() { return state->dialect_attr_end(); }

  /// Return an attribute with the specified name.
  Attribute getAttr(StringRef name) { return state->getAttr(name); }

  /// If the operation has an attribute of the specified type, return it.
  template <typename AttrClass> AttrClass getAttrOfType(StringRef name) {
    return getAttr(name).dyn_cast_or_null<AttrClass>();
  }

  /// If the an attribute exists with the specified name, change it to the new
  /// value.  Otherwise, add a new attribute with the specified name/value.
  void setAttr(Identifier name, Attribute value) {
    state->setAttr(name, value);
  }
  void setAttr(StringRef name, Attribute value) {
    setAttr(Identifier::get(name, getContext()), value);
  }

  /// Set the attributes held by this operation.
  void setAttrs(ArrayRef<NamedAttribute> attributes) {
    state->setAttrs(attributes);
  }
  void setAttrs(MutableDictionaryAttr newAttrs) { state->setAttrs(newAttrs); }

  /// Set the dialect attributes for this operation, and preserve all dependent.
  template <typename DialectAttrs> void setDialectAttrs(DialectAttrs &&attrs) {
    state->setDialectAttrs(std::move(attrs));
  }

  /// Remove the attribute with the specified name if it exists.  The return
  /// value indicates whether the attribute was present or not.
  MutableDictionaryAttr::RemoveResult removeAttr(Identifier name) {
    return state->removeAttr(name);
  }
  MutableDictionaryAttr::RemoveResult removeAttr(StringRef name) {
    return state->removeAttr(Identifier::get(name, getContext()));
  }

  /// Return true if there are no users of any results of this operation.
  bool use_empty() { return state->use_empty(); }

  /// Remove this operation from its parent block and delete it.
  void erase() { state->erase(); }

  /// Emit an error with the op name prefixed, like "'dim' op " which is
  /// convenient for verifiers.
  InFlightDiagnostic emitOpError(const Twine &message = {});

  /// Emit an error about fatal conditions with this operation, reporting up to
  /// any diagnostic handlers that may be listening.
  InFlightDiagnostic emitError(const Twine &message = {});

  /// Emit a warning about this operation, reporting up to any diagnostic
  /// handlers that may be listening.
  InFlightDiagnostic emitWarning(const Twine &message = {});

  /// Emit a remark about this operation, reporting up to any diagnostic
  /// handlers that may be listening.
  InFlightDiagnostic emitRemark(const Twine &message = {});

  /// Walk the operation in postorder, calling the callback for each nested
  /// operation(including this one).
  /// See Operation::walk for more details.
  template <typename FnT, typename RetT = detail::walkResultType<FnT>>
  RetT walk(FnT &&callback) {
    return state->walk(std::forward<FnT>(callback));
  }

  // These are default implementations of customization hooks.
public:
  /// This hook returns any canonicalization pattern rewrites that the operation
  /// supports, for use by the canonicalization pass.
  static void getCanonicalizationPatterns(OwningRewritePatternList &results,
                                          MLIRContext *context) {}

protected:
  /// If the concrete type didn't implement a custom verifier hook, just fall
  /// back to this one which accepts everything.
  LogicalResult verify() { return success(); }

  /// Unless overridden, the custom assembly form of an op is always rejected.
  /// Op implementations should implement this to return failure.
  /// On success, they should fill in result with the fields to use.
  static ParseResult parse(OpAsmParser &parser, OperationState &result);

  // The fallback for the printer is to print it the generic assembly form.
  void print(OpAsmPrinter &p);

  /// Mutability management is handled by the OpWrapper/OpConstWrapper classes,
  /// so we can cast it away here.
  explicit OpState(Operation *state) : state(state) {}

private:
  Operation *state;
};

// Allow comparing operators.
inline bool operator==(OpState lhs, OpState rhs) {
  return lhs.getOperation() == rhs.getOperation();
}
inline bool operator!=(OpState lhs, OpState rhs) {
  return lhs.getOperation() != rhs.getOperation();
}

/// This class represents a single result from folding an operation.
class OpFoldResult : public PointerUnion<Attribute, Value> {
  using PointerUnion<Attribute, Value>::PointerUnion;
};

/// Allow printing to a stream.
inline raw_ostream &operator<<(raw_ostream &os, OpState &op) {
  op.print(os, OpPrintingFlags().useLocalScope());
  return os;
}

/// This template defines the foldHook as used by AbstractOperation.
///
/// The default implementation uses a general fold method that can be defined on
/// custom ops which can return multiple results.
template <typename ConcreteType, bool isSingleResult, typename = void>
class FoldingHook {
public:
  /// This is an implementation detail of the constant folder hook for
  /// AbstractOperation.
  static LogicalResult foldHook(Operation *op, ArrayRef<Attribute> operands,
                                SmallVectorImpl<OpFoldResult> &results) {
    return cast<ConcreteType>(op).fold(operands, results);
  }

  /// This hook implements a generalized folder for this operation.  Operations
  /// can implement this to provide simplifications rules that are applied by
  /// the Builder::createOrFold API and the canonicalization pass.
  ///
  /// This is an intentionally limited interface - implementations of this hook
  /// can only perform the following changes to the operation:
  ///
  ///  1. They can leave the operation alone and without changing the IR, and
  ///     return failure.
  ///  2. They can mutate the operation in place, without changing anything else
  ///     in the IR.  In this case, return success.
  ///  3. They can return a list of existing values that can be used instead of
  ///     the operation.  In this case, fill in the results list and return
  ///     success.  The caller will remove the operation and use those results
  ///     instead.
  ///
  /// This allows expression of some simple in-place canonicalizations (e.g.
  /// "x+0 -> x", "min(x,y,x,z) -> min(x,y,z)", "x+y-x -> y", etc), as well as
  /// generalized constant folding.
  ///
  /// If not overridden, this fallback implementation always fails to fold.
  ///
  LogicalResult fold(ArrayRef<Attribute> operands,
                     SmallVectorImpl<OpFoldResult> &results) {
    return failure();
  }
};

/// This template specialization defines the foldHook as used by
/// AbstractOperation for single-result operations.  This gives the hook a nicer
/// signature that is easier to implement.
template <typename ConcreteType, bool isSingleResult>
class FoldingHook<ConcreteType, isSingleResult,
                  typename std::enable_if<isSingleResult>::type> {
public:
  /// If the operation returns a single value, then the Op can be implicitly
  /// converted to an Value.  This yields the value of the only result.
  operator Value() {
    return static_cast<ConcreteType *>(this)->getOperation()->getResult(0);
  }

  /// This is an implementation detail of the constant folder hook for
  /// AbstractOperation.
  static LogicalResult foldHook(Operation *op, ArrayRef<Attribute> operands,
                                SmallVectorImpl<OpFoldResult> &results) {
    auto result = cast<ConcreteType>(op).fold(operands);
    if (!result)
      return failure();

    // Check if the operation was folded in place. In this case, the operation
    // returns itself.
    if (result.template dyn_cast<Value>() != op->getResult(0))
      results.push_back(result);
    return success();
  }

  /// This hook implements a generalized folder for this operation.  Operations
  /// can implement this to provide simplifications rules that are applied by
  /// the Builder::createOrFold API and the canonicalization pass.
  ///
  /// This is an intentionally limited interface - implementations of this hook
  /// can only perform the following changes to the operation:
  ///
  ///  1. They can leave the operation alone and without changing the IR, and
  ///     return nullptr.
  ///  2. They can mutate the operation in place, without changing anything else
  ///     in the IR.  In this case, return the operation itself.
  ///  3. They can return an existing SSA value that can be used instead of
  ///     the operation.  In this case, return that value.  The caller will
  ///     remove the operation and use that result instead.
  ///
  /// This allows expression of some simple in-place canonicalizations (e.g.
  /// "x+0 -> x", "min(x,y,x,z) -> min(x,y,z)", "x+y-x -> y", etc), as well as
  /// generalized constant folding.
  ///
  /// If not overridden, this fallback implementation always fails to fold.
  ///
  OpFoldResult fold(ArrayRef<Attribute> operands) { return {}; }
};

//===----------------------------------------------------------------------===//
// Operation Trait Types
//===----------------------------------------------------------------------===//

namespace OpTrait {

// These functions are out-of-line implementations of the methods in the
// corresponding trait classes.  This avoids them being template
// instantiated/duplicated.
namespace impl {
LogicalResult verifyZeroOperands(Operation *op);
LogicalResult verifyOneOperand(Operation *op);
LogicalResult verifyNOperands(Operation *op, unsigned numOperands);
LogicalResult verifyAtLeastNOperands(Operation *op, unsigned numOperands);
LogicalResult verifyOperandsAreFloatLike(Operation *op);
LogicalResult verifyOperandsAreSignlessIntegerLike(Operation *op);
LogicalResult verifySameTypeOperands(Operation *op);
LogicalResult verifyZeroRegion(Operation *op);
LogicalResult verifyOneRegion(Operation *op);
LogicalResult verifyNRegions(Operation *op, unsigned numRegions);
LogicalResult verifyAtLeastNRegions(Operation *op, unsigned numRegions);
LogicalResult verifyZeroResult(Operation *op);
LogicalResult verifyOneResult(Operation *op);
LogicalResult verifyNResults(Operation *op, unsigned numOperands);
LogicalResult verifyAtLeastNResults(Operation *op, unsigned numOperands);
LogicalResult verifySameOperandsShape(Operation *op);
LogicalResult verifySameOperandsAndResultShape(Operation *op);
LogicalResult verifySameOperandsElementType(Operation *op);
LogicalResult verifySameOperandsAndResultElementType(Operation *op);
LogicalResult verifySameOperandsAndResultType(Operation *op);
LogicalResult verifyResultsAreBoolLike(Operation *op);
LogicalResult verifyResultsAreFloatLike(Operation *op);
LogicalResult verifyResultsAreSignlessIntegerLike(Operation *op);
LogicalResult verifyIsTerminator(Operation *op);
LogicalResult verifyZeroSuccessor(Operation *op);
LogicalResult verifyOneSuccessor(Operation *op);
LogicalResult verifyNSuccessors(Operation *op, unsigned numSuccessors);
LogicalResult verifyAtLeastNSuccessors(Operation *op, unsigned numSuccessors);
LogicalResult verifyOperandSizeAttr(Operation *op, StringRef sizeAttrName);
LogicalResult verifyResultSizeAttr(Operation *op, StringRef sizeAttrName);
} // namespace impl

/// Helper class for implementing traits.  Clients are not expected to interact
/// with this directly, so its members are all protected.
template <typename ConcreteType, template <typename> class TraitType>
class TraitBase {
protected:
  /// Return the ultimate Operation being worked on.
  Operation *getOperation() {
    // We have to cast up to the trait type, then to the concrete type, then to
    // the BaseState class in explicit hops because the concrete type will
    // multiply derive from the (content free) TraitBase class, and we need to
    // be able to disambiguate the path for the C++ compiler.
    auto *trait = static_cast<TraitType<ConcreteType> *>(this);
    auto *concrete = static_cast<ConcreteType *>(trait);
    auto *base = static_cast<OpState *>(concrete);
    return base->getOperation();
  }

  /// Provide default implementations of trait hooks.  This allows traits to
  /// provide exactly the overrides they care about.
  static LogicalResult verifyTrait(Operation *op) { return success(); }
  static AbstractOperation::OperationProperties getTraitProperties() {
    return 0;
  }
};

//===----------------------------------------------------------------------===//
// Operand Traits

namespace detail {
/// Utility trait base that provides accessors for derived traits that have
/// multiple operands.
template <typename ConcreteType, template <typename> class TraitType>
struct MultiOperandTraitBase : public TraitBase<ConcreteType, TraitType> {
  using operand_iterator = Operation::operand_iterator;
  using operand_range = Operation::operand_range;
  using operand_type_iterator = Operation::operand_type_iterator;
  using operand_type_range = Operation::operand_type_range;

  /// Return the number of operands.
  unsigned getNumOperands() { return this->getOperation()->getNumOperands(); }

  /// Return the operand at index 'i'.
  Value getOperand(unsigned i) { return this->getOperation()->getOperand(i); }

  /// Set the operand at index 'i' to 'value'.
  void setOperand(unsigned i, Value value) {
    this->getOperation()->setOperand(i, value);
  }

  /// Operand iterator access.
  operand_iterator operand_begin() {
    return this->getOperation()->operand_begin();
  }
  operand_iterator operand_end() { return this->getOperation()->operand_end(); }
  operand_range getOperands() { return this->getOperation()->getOperands(); }

  /// Operand type access.
  operand_type_iterator operand_type_begin() {
    return this->getOperation()->operand_type_begin();
  }
  operand_type_iterator operand_type_end() {
    return this->getOperation()->operand_type_end();
  }
  operand_type_range getOperandTypes() {
    return this->getOperation()->getOperandTypes();
  }
};
} // end namespace detail

/// This class provides the API for ops that are known to have no
/// SSA operand.
template <typename ConcreteType>
class ZeroOperands : public TraitBase<ConcreteType, ZeroOperands> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyZeroOperands(op);
  }

private:
  // Disable these.
  void getOperand() {}
  void setOperand() {}
};

/// This class provides the API for ops that are known to have exactly one
/// SSA operand.
template <typename ConcreteType>
class OneOperand : public TraitBase<ConcreteType, OneOperand> {
public:
  Value getOperand() { return this->getOperation()->getOperand(0); }

  void setOperand(Value value) { this->getOperation()->setOperand(0, value); }

  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyOneOperand(op);
  }
};

/// This class provides the API for ops that are known to have a specified
/// number of operands.  This is used as a trait like this:
///
///   class FooOp : public Op<FooOp, OpTrait::NOperands<2>::Impl> {
///
template <unsigned N> class NOperands {
public:
  static_assert(N > 1, "use ZeroOperands/OneOperand for N < 2");

  template <typename ConcreteType>
  class Impl
      : public detail::MultiOperandTraitBase<ConcreteType, NOperands<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyNOperands(op, N);
    }
  };
};

/// This class provides the API for ops that are known to have a at least a
/// specified number of operands.  This is used as a trait like this:
///
///   class FooOp : public Op<FooOp, OpTrait::AtLeastNOperands<2>::Impl> {
///
template <unsigned N> class AtLeastNOperands {
public:
  template <typename ConcreteType>
  class Impl : public detail::MultiOperandTraitBase<ConcreteType,
                                                    AtLeastNOperands<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyAtLeastNOperands(op, N);
    }
  };
};

/// This class provides the API for ops which have an unknown number of
/// SSA operands.
template <typename ConcreteType>
class VariadicOperands
    : public detail::MultiOperandTraitBase<ConcreteType, VariadicOperands> {};

//===----------------------------------------------------------------------===//
// Region Traits

/// This class provides verification for ops that are known to have zero
/// regions.
template <typename ConcreteType>
class ZeroRegion : public TraitBase<ConcreteType, ZeroRegion> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyZeroRegion(op);
  }
};

namespace detail {
/// Utility trait base that provides accessors for derived traits that have
/// multiple regions.
template <typename ConcreteType, template <typename> class TraitType>
struct MultiRegionTraitBase : public TraitBase<ConcreteType, TraitType> {
  using region_iterator = MutableArrayRef<Region>;
  using region_range = RegionRange;

  /// Return the number of regions.
  unsigned getNumRegions() { return this->getOperation()->getNumRegions(); }

  /// Return the region at `index`.
  Region &getRegion(unsigned i) { return this->getOperation()->getRegion(i); }

  /// Region iterator access.
  region_iterator region_begin() {
    return this->getOperation()->region_begin();
  }
  region_iterator region_end() { return this->getOperation()->region_end(); }
  region_range getRegions() { return this->getOperation()->getRegions(); }
};
} // end namespace detail

/// This class provides APIs for ops that are known to have a single region.
template <typename ConcreteType>
class OneRegion : public TraitBase<ConcreteType, OneRegion> {
public:
  Region &getRegion() { return this->getOperation()->getRegion(0); }

  /// Returns a range of operations within the region of this operation.
  auto getOps() { return getRegion().getOps(); }
  template <typename OpT>
  auto getOps() {
    return getRegion().template getOps<OpT>();
  }

  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyOneRegion(op);
  }
};

/// This class provides the API for ops that are known to have a specified
/// number of regions.
template <unsigned N> class NRegions {
public:
  static_assert(N > 1, "use ZeroRegion/OneRegion for N < 2");

  template <typename ConcreteType>
  class Impl
      : public detail::MultiRegionTraitBase<ConcreteType, NRegions<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyNRegions(op, N);
    }
  };
};

/// This class provides APIs for ops that are known to have at least a specified
/// number of regions.
template <unsigned N> class AtLeastNRegions {
public:
  template <typename ConcreteType>
  class Impl : public detail::MultiRegionTraitBase<ConcreteType,
                                                   AtLeastNRegions<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyAtLeastNRegions(op, N);
    }
  };
};

/// This class provides the API for ops which have an unknown number of
/// regions.
template <typename ConcreteType>
class VariadicRegions
    : public detail::MultiRegionTraitBase<ConcreteType, VariadicRegions> {};

//===----------------------------------------------------------------------===//
// Result Traits

/// This class provides return value APIs for ops that are known to have
/// zero results.
template <typename ConcreteType>
class ZeroResult : public TraitBase<ConcreteType, ZeroResult> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyZeroResult(op);
  }
};

namespace detail {
/// Utility trait base that provides accessors for derived traits that have
/// multiple results.
template <typename ConcreteType, template <typename> class TraitType>
struct MultiResultTraitBase : public TraitBase<ConcreteType, TraitType> {
  using result_iterator = Operation::result_iterator;
  using result_range = Operation::result_range;
  using result_type_iterator = Operation::result_type_iterator;
  using result_type_range = Operation::result_type_range;

  /// Return the number of results.
  unsigned getNumResults() { return this->getOperation()->getNumResults(); }

  /// Return the result at index 'i'.
  Value getResult(unsigned i) { return this->getOperation()->getResult(i); }

  /// Replace all uses of results of this operation with the provided 'values'.
  /// 'values' may correspond to an existing operation, or a range of 'Value'.
  template <typename ValuesT> void replaceAllUsesWith(ValuesT &&values) {
    this->getOperation()->replaceAllUsesWith(std::forward<ValuesT>(values));
  }

  /// Return the type of the `i`-th result.
  Type getType(unsigned i) { return getResult(i).getType(); }

  /// Result iterator access.
  result_iterator result_begin() {
    return this->getOperation()->result_begin();
  }
  result_iterator result_end() { return this->getOperation()->result_end(); }
  result_range getResults() { return this->getOperation()->getResults(); }

  /// Result type access.
  result_type_iterator result_type_begin() {
    return this->getOperation()->result_type_begin();
  }
  result_type_iterator result_type_end() {
    return this->getOperation()->result_type_end();
  }
  result_type_range getResultTypes() {
    return this->getOperation()->getResultTypes();
  }
};
} // end namespace detail

/// This class provides return value APIs for ops that are known to have a
/// single result.
template <typename ConcreteType>
class OneResult : public TraitBase<ConcreteType, OneResult> {
public:
  Value getResult() { return this->getOperation()->getResult(0); }
  Type getType() { return getResult().getType(); }

  /// Replace all uses of 'this' value with the new value, updating anything in
  /// the IR that uses 'this' to use the other value instead.  When this returns
  /// there are zero uses of 'this'.
  void replaceAllUsesWith(Value newValue) {
    getResult().replaceAllUsesWith(newValue);
  }

  /// Replace all uses of 'this' value with the result of 'op'.
  void replaceAllUsesWith(Operation *op) {
    this->getOperation()->replaceAllUsesWith(op);
  }

  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyOneResult(op);
  }
};

/// This class provides the API for ops that are known to have a specified
/// number of results.  This is used as a trait like this:
///
///   class FooOp : public Op<FooOp, OpTrait::NResults<2>::Impl> {
///
template <unsigned N> class NResults {
public:
  static_assert(N > 1, "use ZeroResult/OneResult for N < 2");

  template <typename ConcreteType>
  class Impl
      : public detail::MultiResultTraitBase<ConcreteType, NResults<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyNResults(op, N);
    }
  };
};

/// This class provides the API for ops that are known to have at least a
/// specified number of results.  This is used as a trait like this:
///
///   class FooOp : public Op<FooOp, OpTrait::AtLeastNResults<2>::Impl> {
///
template <unsigned N> class AtLeastNResults {
public:
  template <typename ConcreteType>
  class Impl : public detail::MultiResultTraitBase<ConcreteType,
                                                   AtLeastNResults<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyAtLeastNResults(op, N);
    }
  };
};

/// This class provides the API for ops which have an unknown number of
/// results.
template <typename ConcreteType>
class VariadicResults
    : public detail::MultiResultTraitBase<ConcreteType, VariadicResults> {};

//===----------------------------------------------------------------------===//
// Terminator Traits

/// This class provides the API for ops that are known to be terminators.
template <typename ConcreteType>
class IsTerminator : public TraitBase<ConcreteType, IsTerminator> {
public:
  static AbstractOperation::OperationProperties getTraitProperties() {
    return static_cast<AbstractOperation::OperationProperties>(
        OperationProperty::Terminator);
  }
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyIsTerminator(op);
  }
};

/// This class provides verification for ops that are known to have zero
/// successors.
template <typename ConcreteType>
class ZeroSuccessor : public TraitBase<ConcreteType, ZeroSuccessor> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyZeroSuccessor(op);
  }
};

namespace detail {
/// Utility trait base that provides accessors for derived traits that have
/// multiple successors.
template <typename ConcreteType, template <typename> class TraitType>
struct MultiSuccessorTraitBase : public TraitBase<ConcreteType, TraitType> {
  using succ_iterator = Operation::succ_iterator;
  using succ_range = SuccessorRange;

  /// Return the number of successors.
  unsigned getNumSuccessors() {
    return this->getOperation()->getNumSuccessors();
  }

  /// Return the successor at `index`.
  Block *getSuccessor(unsigned i) {
    return this->getOperation()->getSuccessor(i);
  }

  /// Set the successor at `index`.
  void setSuccessor(Block *block, unsigned i) {
    return this->getOperation()->setSuccessor(block, i);
  }

  /// Successor iterator access.
  succ_iterator succ_begin() { return this->getOperation()->succ_begin(); }
  succ_iterator succ_end() { return this->getOperation()->succ_end(); }
  succ_range getSuccessors() { return this->getOperation()->getSuccessors(); }
};
} // end namespace detail

/// This class provides APIs for ops that are known to have a single successor.
template <typename ConcreteType>
class OneSuccessor : public TraitBase<ConcreteType, OneSuccessor> {
public:
  Block *getSuccessor() { return this->getOperation()->getSuccessor(0); }
  void setSuccessor(Block *succ) {
    this->getOperation()->setSuccessor(succ, 0);
  }

  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyOneSuccessor(op);
  }
};

/// This class provides the API for ops that are known to have a specified
/// number of successors.
template <unsigned N>
class NSuccessors {
public:
  static_assert(N > 1, "use ZeroSuccessor/OneSuccessor for N < 2");

  template <typename ConcreteType>
  class Impl : public detail::MultiSuccessorTraitBase<ConcreteType,
                                                      NSuccessors<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyNSuccessors(op, N);
    }
  };
};

/// This class provides APIs for ops that are known to have at least a specified
/// number of successors.
template <unsigned N>
class AtLeastNSuccessors {
public:
  template <typename ConcreteType>
  class Impl
      : public detail::MultiSuccessorTraitBase<ConcreteType,
                                               AtLeastNSuccessors<N>::Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      return impl::verifyAtLeastNSuccessors(op, N);
    }
  };
};

/// This class provides the API for ops which have an unknown number of
/// successors.
template <typename ConcreteType>
class VariadicSuccessors
    : public detail::MultiSuccessorTraitBase<ConcreteType, VariadicSuccessors> {
};

//===----------------------------------------------------------------------===//
// Misc Traits

/// This class provides verification for ops that are known to have the same
/// operand shape: all operands are scalars, vectors/tensors of the same
/// shape.
template <typename ConcreteType>
class SameOperandsShape : public TraitBase<ConcreteType, SameOperandsShape> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifySameOperandsShape(op);
  }
};

/// This class provides verification for ops that are known to have the same
/// operand and result shape: both are scalars, vectors/tensors of the same
/// shape.
template <typename ConcreteType>
class SameOperandsAndResultShape
    : public TraitBase<ConcreteType, SameOperandsAndResultShape> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifySameOperandsAndResultShape(op);
  }
};

/// This class provides verification for ops that are known to have the same
/// operand element type (or the type itself if it is scalar).
///
template <typename ConcreteType>
class SameOperandsElementType
    : public TraitBase<ConcreteType, SameOperandsElementType> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifySameOperandsElementType(op);
  }
};

/// This class provides verification for ops that are known to have the same
/// operand and result element type (or the type itself if it is scalar).
///
template <typename ConcreteType>
class SameOperandsAndResultElementType
    : public TraitBase<ConcreteType, SameOperandsAndResultElementType> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifySameOperandsAndResultElementType(op);
  }
};

/// This class provides verification for ops that are known to have the same
/// operand and result type.
///
/// Note: this trait subsumes the SameOperandsAndResultShape and
/// SameOperandsAndResultElementType traits.
template <typename ConcreteType>
class SameOperandsAndResultType
    : public TraitBase<ConcreteType, SameOperandsAndResultType> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifySameOperandsAndResultType(op);
  }
};

/// This class verifies that any results of the specified op have a boolean
/// type, a vector thereof, or a tensor thereof.
template <typename ConcreteType>
class ResultsAreBoolLike : public TraitBase<ConcreteType, ResultsAreBoolLike> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyResultsAreBoolLike(op);
  }
};

/// This class verifies that any results of the specified op have a floating
/// point type, a vector thereof, or a tensor thereof.
template <typename ConcreteType>
class ResultsAreFloatLike
    : public TraitBase<ConcreteType, ResultsAreFloatLike> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyResultsAreFloatLike(op);
  }
};

/// This class verifies that any results of the specified op have a signless
/// integer or index type, a vector thereof, or a tensor thereof.
template <typename ConcreteType>
class ResultsAreSignlessIntegerLike
    : public TraitBase<ConcreteType, ResultsAreSignlessIntegerLike> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyResultsAreSignlessIntegerLike(op);
  }
};

/// This class adds property that the operation is commutative.
template <typename ConcreteType>
class IsCommutative : public TraitBase<ConcreteType, IsCommutative> {
public:
  static AbstractOperation::OperationProperties getTraitProperties() {
    return static_cast<AbstractOperation::OperationProperties>(
        OperationProperty::Commutative);
  }
};

/// This class verifies that all operands of the specified op have a float type,
/// a vector thereof, or a tensor thereof.
template <typename ConcreteType>
class OperandsAreFloatLike
    : public TraitBase<ConcreteType, OperandsAreFloatLike> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyOperandsAreFloatLike(op);
  }
};

/// This class verifies that all operands of the specified op have a signless
/// integer or index type, a vector thereof, or a tensor thereof.
template <typename ConcreteType>
class OperandsAreSignlessIntegerLike
    : public TraitBase<ConcreteType, OperandsAreSignlessIntegerLike> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifyOperandsAreSignlessIntegerLike(op);
  }
};

/// This class verifies that all operands of the specified op have the same
/// type.
template <typename ConcreteType>
class SameTypeOperands : public TraitBase<ConcreteType, SameTypeOperands> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    return impl::verifySameTypeOperands(op);
  }
};

/// This class provides the API for a sub-set of ops that are known to be
/// constant-like. These are non-side effecting operations with one result and
/// zero operands that can always be folded to a specific attribute value.
template <typename ConcreteType>
class ConstantLike : public TraitBase<ConcreteType, ConstantLike> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    static_assert(ConcreteType::template hasTrait<OneResult>(),
                  "expected operation to produce one result");
    static_assert(ConcreteType::template hasTrait<ZeroOperands>(),
                  "expected operation to take zero operands");
    // TODO: We should verify that the operation can always be folded, but this
    // requires that the attributes of the op already be verified. We should add
    // support for verifying traits "after" the operation to enable this use
    // case.
    return success();
  }
};

/// This class provides the API for ops that are known to be isolated from
/// above.
template <typename ConcreteType>
class IsIsolatedFromAbove
    : public TraitBase<ConcreteType, IsIsolatedFromAbove> {
public:
  static AbstractOperation::OperationProperties getTraitProperties() {
    return static_cast<AbstractOperation::OperationProperties>(
        OperationProperty::IsolatedFromAbove);
  }
  static LogicalResult verifyTrait(Operation *op) {
    for (auto &region : op->getRegions())
      if (!region.isIsolatedFromAbove(op->getLoc()))
        return failure();
    return success();
  }
};

/// A trait of region holding operations that defines a new scope for polyhedral
/// optimization purposes. Any SSA values of 'index' type that either dominate
/// such an operation or are used at the top-level of such an operation
/// automatically become valid symbols for the polyhedral scope defined by that
/// operation. For more details, see `Traits.md#AffineScope`.
template <typename ConcreteType>
class AffineScope : public TraitBase<ConcreteType, AffineScope> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    static_assert(!ConcreteType::template hasTrait<ZeroRegion>(),
                  "expected operation to have one or more regions");
    return success();
  }
};

/// A trait of region holding operations that define a new scope for automatic
/// allocations, i.e., allocations that are freed when control is transferred
/// back from the operation's region. Any operations performing such allocations
/// (for eg. std.alloca) will have their allocations automatically freed at
/// their closest enclosing operation with this trait.
template <typename ConcreteType>
class AutomaticAllocationScope
    : public TraitBase<ConcreteType, AutomaticAllocationScope> {
public:
  static LogicalResult verifyTrait(Operation *op) {
    if (op->hasTrait<ZeroRegion>())
      return op->emitOpError("is expected to have regions");
    return success();
  }
};

/// This class provides APIs and verifiers for ops with regions having a single
/// block that must terminate with `TerminatorOpType`.
template <typename TerminatorOpType> struct SingleBlockImplicitTerminator {
  template <typename ConcreteType>
  class Impl : public TraitBase<ConcreteType, Impl> {
  private:
    /// Builds a terminator operation without relying on OpBuilder APIs to avoid
    /// cyclic header inclusion.
    static Operation *buildTerminator(OpBuilder &builder, Location loc) {
      OperationState state(loc, TerminatorOpType::getOperationName());
      TerminatorOpType::build(builder, state);
      return Operation::create(state);
    }

  public:
    static LogicalResult verifyTrait(Operation *op) {
      for (unsigned i = 0, e = op->getNumRegions(); i < e; ++i) {
        Region &region = op->getRegion(i);

        // Empty regions are fine.
        if (region.empty())
          continue;

        // Non-empty regions must contain a single basic block.
        if (std::next(region.begin()) != region.end())
          return op->emitOpError("expects region #")
                 << i << " to have 0 or 1 blocks";

        Block &block = region.front();
        if (block.empty())
          return op->emitOpError() << "expects a non-empty block";
        Operation &terminator = block.back();
        if (isa<TerminatorOpType>(terminator))
          continue;

        return op->emitOpError("expects regions to end with '" +
                               TerminatorOpType::getOperationName() +
                               "', found '" +
                               terminator.getName().getStringRef() + "'")
                   .attachNote()
               << "in custom textual format, the absence of terminator implies "
                  "'"
               << TerminatorOpType::getOperationName() << '\'';
      }

      return success();
    }

    /// Ensure that the given region has the terminator required by this trait.
    /// If OpBuilder is provided, use it to build the terminator and notify the
    /// OpBuilder litsteners accoridngly. If only a Builder is provided, locally
    /// construct an OpBuilder with no listeners; this should only be used if no
    /// OpBuilder is available at the call site, e.g., in the parser.
    static void ensureTerminator(Region &region, Builder &builder,
                                 Location loc) {
      ::mlir::impl::ensureRegionTerminator(region, builder, loc,
                                           buildTerminator);
    }
    static void ensureTerminator(Region &region, OpBuilder &builder,
                                 Location loc) {
      ::mlir::impl::ensureRegionTerminator(region, builder, loc,
                                           buildTerminator);
    }

    Block *getBody(unsigned idx = 0) {
      Region &region = this->getOperation()->getRegion(idx);
      assert(!region.empty() && "unexpected empty region");
      return &region.front();
    }
  };
};

/// This class provides a verifier for ops that are expecting their parent
/// to be one of the given parent ops
template <typename... ParentOpTypes>
struct HasParent {
  template <typename ConcreteType>
  class Impl : public TraitBase<ConcreteType, Impl> {
  public:
    static LogicalResult verifyTrait(Operation *op) {
      if (llvm::isa<ParentOpTypes...>(op->getParentOp()))
        return success();

      return op->emitOpError()
             << "expects parent op "
             << (sizeof...(ParentOpTypes) != 1 ? "to be one of '" : "'")
             << llvm::makeArrayRef({ParentOpTypes::getOperationName()...})
             << "'";
    }
  };
};

/// A trait for operations that have an attribute specifying operand segments.
///
/// Certain operations can have multiple variadic operands and their size
/// relationship is not always known statically. For such cases, we need
/// a per-op-instance specification to divide the operands into logical groups
/// or segments. This can be modeled by attributes. The attribute will be named
/// as `operand_segment_sizes`.
///
/// This trait verifies the attribute for specifying operand segments has
/// the correct type (1D vector) and values (non-negative), etc.
template <typename ConcreteType>
class AttrSizedOperandSegments
    : public TraitBase<ConcreteType, AttrSizedOperandSegments> {
public:
  static StringRef getOperandSegmentSizeAttr() {
    return "operand_segment_sizes";
  }

  static LogicalResult verifyTrait(Operation *op) {
    return ::mlir::OpTrait::impl::verifyOperandSizeAttr(
        op, getOperandSegmentSizeAttr());
  }
};

/// Similar to AttrSizedOperandSegments but used for results.
template <typename ConcreteType>
class AttrSizedResultSegments
    : public TraitBase<ConcreteType, AttrSizedResultSegments> {
public:
  static StringRef getResultSegmentSizeAttr() { return "result_segment_sizes"; }

  static LogicalResult verifyTrait(Operation *op) {
    return ::mlir::OpTrait::impl::verifyResultSizeAttr(
        op, getResultSegmentSizeAttr());
  }
};

} // end namespace OpTrait

//===----------------------------------------------------------------------===//
// Operation Definition classes
//===----------------------------------------------------------------------===//

/// This provides public APIs that all operations should have.  The template
/// argument 'ConcreteType' should be the concrete type by CRTP and the others
/// are base classes by the policy pattern.
template <typename ConcreteType, template <typename T> class... Traits>
class Op : public OpState,
           public Traits<ConcreteType>...,
           public FoldingHook<ConcreteType,
                              llvm::is_one_of<OpTrait::OneResult<ConcreteType>,
                                              Traits<ConcreteType>...>::value> {
public:
  /// Return if this operation contains the provided trait.
  template <template <typename T> class Trait>
  static constexpr bool hasTrait() {
    return llvm::is_one_of<Trait<ConcreteType>, Traits<ConcreteType>...>::value;
  }

  /// Return the operation that this refers to.
  Operation *getOperation() { return OpState::getOperation(); }

  /// Create a deep copy of this operation.
  ConcreteType clone() { return cast<ConcreteType>(getOperation()->clone()); }

  /// Create a partial copy of this operation without traversing into attached
  /// regions. The new operation will have the same number of regions as the
  /// original one, but they will be left empty.
  ConcreteType cloneWithoutRegions() {
    return cast<ConcreteType>(getOperation()->cloneWithoutRegions());
  }

  /// Return the dialect that this refers to.
  Dialect *getDialect() { return getOperation()->getDialect(); }

  /// Return the parent Region of this operation.
  Region *getParentRegion() { return getOperation()->getParentRegion(); }

  /// Return true if this "op class" can match against the specified operation.
  static bool classof(Operation *op) {
    if (auto *abstractOp = op->getAbstractOperation())
      return TypeID::get<ConcreteType>() == abstractOp->typeID;
    assert(op->getContext()->isOperationRegistered(
               ConcreteType::getOperationName()) &&
           "Casting attempt to an unregistered operation");
    return false;
  }

  /// This is the hook used by the AsmParser to parse the custom form of this
  /// op from an .mlir file.  Op implementations should provide a parse method,
  /// which returns failure.  On success, they should return fill in result with
  /// the fields to use.
  static ParseResult parseAssembly(OpAsmParser &parser,
                                   OperationState &result) {
    return ConcreteType::parse(parser, result);
  }

  /// This is the hook used by the AsmPrinter to emit this to the .mlir file.
  /// Op implementations should provide a print method.
  static void printAssembly(Operation *op, OpAsmPrinter &p) {
    auto opPointer = dyn_cast<ConcreteType>(op);
    assert(opPointer &&
           "op's name does not match name of concrete type instantiated with");
    opPointer.print(p);
  }

  /// This is the hook that checks whether or not this operation is well
  /// formed according to the invariants of its opcode.  It delegates to the
  /// Traits for their policy implementations, and allows the user to specify
  /// their own verify() method.
  ///
  /// On success this returns false; on failure it emits an error to the
  /// diagnostic subsystem and returns true.
  static LogicalResult verifyInvariants(Operation *op) {
    return failure(
        failed(BaseVerifier<Traits<ConcreteType>...>::verifyTrait(op)) ||
        failed(cast<ConcreteType>(op).verify()));
  }

  // Returns the properties of an operation by combining the properties of the
  // traits of the op.
  static AbstractOperation::OperationProperties getOperationProperties() {
    return BaseProperties<Traits<ConcreteType>...>::getTraitProperties();
  }

  /// Expose the type we are instantiated on to template machinery that may want
  /// to introspect traits on this operation.
  using ConcreteOpType = ConcreteType;

  /// This is a public constructor.  Any op can be initialized to null.
  explicit Op() : OpState(nullptr) {}
  Op(std::nullptr_t) : OpState(nullptr) {}

  /// This is a public constructor to enable access via the llvm::cast family of
  /// methods. This should not be used directly.
  explicit Op(Operation *state) : OpState(state) {}

  /// Methods for supporting PointerLikeTypeTraits.
  const void *getAsOpaquePointer() const {
    return static_cast<const void *>((Operation *)*this);
  }
  static ConcreteOpType getFromOpaquePointer(const void *pointer) {
    return ConcreteOpType(
        reinterpret_cast<Operation *>(const_cast<void *>(pointer)));
  }

private:
  template <typename... Types> struct BaseVerifier;

  template <typename First, typename... Rest>
  struct BaseVerifier<First, Rest...> {
    static LogicalResult verifyTrait(Operation *op) {
      return failure(failed(First::verifyTrait(op)) ||
                     failed(BaseVerifier<Rest...>::verifyTrait(op)));
    }
  };

  template <typename...> struct BaseVerifier {
    static LogicalResult verifyTrait(Operation *op) { return success(); }
  };

  template <typename... Types> struct BaseProperties;

  template <typename First, typename... Rest>
  struct BaseProperties<First, Rest...> {
    static AbstractOperation::OperationProperties getTraitProperties() {
      return First::getTraitProperties() |
             BaseProperties<Rest...>::getTraitProperties();
    }
  };

  template <typename...> struct BaseProperties {
    static AbstractOperation::OperationProperties getTraitProperties() {
      return 0;
    }
  };

  /// Returns true if this operation contains the trait for the given typeID.
  static bool hasTrait(TypeID traitID) {
    return llvm::is_contained(llvm::makeArrayRef({TypeID::get<Traits>()...}),
                              traitID);
  }

  /// Returns an opaque pointer to a concept instance of the interface with the
  /// given ID if one was registered to this operation.
  static void *getRawInterface(TypeID id) {
    return InterfaceLookup::template lookup<Traits<ConcreteType>...>(id);
  }

  struct InterfaceLookup {
    /// Trait to check if T provides a static 'getInterfaceID' method.
    template <typename T, typename... Args>
    using has_get_interface_id = decltype(T::getInterfaceID());

    /// If 'T' is the same interface as 'interfaceID' return the concept
    /// instance.
    template <typename T>
    static typename std::enable_if<
        llvm::is_detected<has_get_interface_id, T>::value, void *>::type
    lookup(TypeID interfaceID) {
      return (T::getInterfaceID() == interfaceID) ? &T::instance() : nullptr;
    }

    /// 'T' is known to not be an interface, return nullptr.
    template <typename T>
    static typename std::enable_if<
        !llvm::is_detected<has_get_interface_id, T>::value, void *>::type
    lookup(TypeID) {
      return nullptr;
    }

    template <typename T, typename T2, typename... Ts>
    static void *lookup(TypeID interfaceID) {
      auto *concept = lookup<T>(interfaceID);
      return concept ? concept : lookup<T2, Ts...>(interfaceID);
    }
  };

  /// Allow access to 'hasTrait' and 'getRawInterface'.
  friend AbstractOperation;
};

/// This class represents the base of an operation interface. Operation
/// interfaces provide access to derived *Op properties through an opaquely
/// Operation instance. Derived interfaces must also provide a 'Traits' class
/// that defines a 'Concept' and a 'Model' class. The 'Concept' class defines an
/// abstract virtual interface, where as the 'Model' class implements this
/// interface for a specific derived *Op type. Both of these classes *must* not
/// contain non-static data. A simple example is shown below:
///
///  struct ExampleOpInterfaceTraits {
///    struct Concept {
///      virtual unsigned getNumInputs(Operation *op) = 0;
///    };
///    template <typename OpT> class Model {
///      unsigned getNumInputs(Operation *op) final {
///        return cast<OpT>(op).getNumInputs();
///      }
///    };
///  };
///
template <typename ConcreteType, typename Traits>
class OpInterface : public Op<ConcreteType> {
public:
  using Concept = typename Traits::Concept;
  template <typename T> using Model = typename Traits::template Model<T>;
  using Base = OpInterface<ConcreteType, Traits>;

  OpInterface(Operation *op = nullptr)
      : Op<ConcreteType>(op), impl(op ? getInterfaceFor(op) : nullptr) {
    assert((!op || impl) &&
           "instantiating an interface with an unregistered operation");
  }

  /// Support 'classof' by checking if the given operation defines the concrete
  /// interface.
  static bool classof(Operation *op) { return getInterfaceFor(op); }

  /// Define an accessor for the ID of this interface.
  static TypeID getInterfaceID() { return TypeID::get<ConcreteType>(); }

  /// This is a special trait that registers a given interface with an
  /// operation.
  template <typename ConcreteOp>
  struct Trait : public OpTrait::TraitBase<ConcreteOp, Trait> {
    /// Define an accessor for the ID of this interface.
    static TypeID getInterfaceID() { return TypeID::get<ConcreteType>(); }

    /// Provide an accessor to a static instance of the interface model for the
    /// concrete operation type.
    /// The implementation is inspired from Sean Parent's concept-based
    /// polymorphism. A key difference is that the set of classes erased is
    /// statically known, which alleviates the need for using dynamic memory
    /// allocation.
    /// We use a zero-sized templated class `Model<ConcreteOp>` to emit the
    /// virtual table and generate a singleton object for each instantiation of
    /// this class.
    static Concept &instance() {
      static Model<ConcreteOp> singleton;
      return singleton;
    }
  };

protected:
  /// Get the raw concept in the correct derived concept type.
  Concept *getImpl() { return impl; }

private:
  /// Returns the impl interface instance for the given operation.
  static Concept *getInterfaceFor(Operation *op) {
    // Access the raw interface from the abstract operation.
    auto *abstractOp = op->getAbstractOperation();
    return abstractOp ? abstractOp->getInterface<ConcreteType>() : nullptr;
  }

  /// A pointer to the impl concept object.
  Concept *impl;
};

//===----------------------------------------------------------------------===//
// Common Operation Folders/Parsers/Printers
//===----------------------------------------------------------------------===//

// These functions are out-of-line implementations of the methods in UnaryOp and
// BinaryOp, which avoids them being template instantiated/duplicated.
namespace impl {
ParseResult parseOneResultOneOperandTypeOp(OpAsmParser &parser,
                                           OperationState &result);

void buildBinaryOp(OpBuilder &builder, OperationState &result, Value lhs,
                   Value rhs);
ParseResult parseOneResultSameOperandTypeOp(OpAsmParser &parser,
                                            OperationState &result);

// Prints the given binary `op` in custom assembly form if both the two operands
// and the result have the same time. Otherwise, prints the generic assembly
// form.
void printOneResultOp(Operation *op, OpAsmPrinter &p);
} // namespace impl

// These functions are out-of-line implementations of the methods in CastOp,
// which avoids them being template instantiated/duplicated.
namespace impl {
void buildCastOp(OpBuilder &builder, OperationState &result, Value source,
                 Type destType);
ParseResult parseCastOp(OpAsmParser &parser, OperationState &result);
void printCastOp(Operation *op, OpAsmPrinter &p);
Value foldCastOp(Operation *op);
} // namespace impl
} // end namespace mlir

#endif