llvm/IR/PassManagerInternal.h

//===- PassManager internal APIs and implementation details -----*- 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
///
/// This header provides internal APIs and implementation details used by the
/// pass management interfaces exposed in PassManager.h. To understand more
/// context of why these particular interfaces are needed, see that header
/// file. None of these APIs should be used elsewhere.
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_IR_PASSMANAGERINTERNAL_H
#define LLVM_IR_PASSMANAGERINTERNAL_H

#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include <memory>
#include <utility>

namespace llvm {

template <typename IRUnitT> class AllAnalysesOn;
template <typename IRUnitT, typename... ExtraArgTs> class AnalysisManager;
class PreservedAnalyses;

// Implementation details of the pass manager interfaces.
namespace detail {

/// Template for the abstract base class used to dispatch
/// polymorphically over pass objects.
template <typename IRUnitT, typename AnalysisManagerT, typename... ExtraArgTs>
struct PassConcept {
  // Boiler plate necessary for the container of derived classes.
  virtual ~PassConcept() = default;

  /// The polymorphic API which runs the pass over a given IR entity.
  ///
  /// Note that actual pass object can omit the analysis manager argument if
  /// desired. Also that the analysis manager may be null if there is no
  /// analysis manager in the pass pipeline.
  virtual PreservedAnalyses run(IRUnitT &IR, AnalysisManagerT &AM,
                                ExtraArgTs... ExtraArgs) = 0;

  /// Polymorphic method to access the name of a pass.
  virtual StringRef name() const = 0;

  /// Polymorphic method to to let a pass optionally exempted from skipping by
  /// PassInstrumentation.
  /// To opt-in, pass should implement `static bool isRequired()`. It's no-op
  /// to have `isRequired` always return false since that is the default.
  virtual bool isRequired() const = 0;
};

/// A template wrapper used to implement the polymorphic API.
///
/// Can be instantiated for any object which provides a \c run method accepting
/// an \c IRUnitT& and an \c AnalysisManager<IRUnit>&. It requires the pass to
/// be a copyable object.
template <typename IRUnitT, typename PassT, typename PreservedAnalysesT,
          typename AnalysisManagerT, typename... ExtraArgTs>
struct PassModel : PassConcept<IRUnitT, AnalysisManagerT, ExtraArgTs...> {
  explicit PassModel(PassT Pass) : Pass(std::move(Pass)) {}
  // We have to explicitly define all the special member functions because MSVC
  // refuses to generate them.
  PassModel(const PassModel &Arg) : Pass(Arg.Pass) {}
  PassModel(PassModel &&Arg) : Pass(std::move(Arg.Pass)) {}

  friend void swap(PassModel &LHS, PassModel &RHS) {
    using std::swap;
    swap(LHS.Pass, RHS.Pass);
  }

  PassModel &operator=(PassModel RHS) {
    swap(*this, RHS);
    return *this;
  }

  PreservedAnalysesT run(IRUnitT &IR, AnalysisManagerT &AM,
                         ExtraArgTs... ExtraArgs) override {
    return Pass.run(IR, AM, ExtraArgs...);
  }

  StringRef name() const override { return PassT::name(); }

  template <typename T>
  using has_required_t = decltype(std::declval<T &>().isRequired());

  template <typename T>
  static std::enable_if_t<is_detected<has_required_t, T>::value, bool>
  passIsRequiredImpl() {
    return T::isRequired();
  }
  template <typename T>
  static std::enable_if_t<!is_detected<has_required_t, T>::value, bool>
  passIsRequiredImpl() {
    return false;
  }

  bool isRequired() const override { return passIsRequiredImpl<PassT>(); }

  PassT Pass;
};

/// Abstract concept of an analysis result.
///
/// This concept is parameterized over the IR unit that this result pertains
/// to.
template <typename IRUnitT, typename PreservedAnalysesT, typename InvalidatorT>
struct AnalysisResultConcept {
  virtual ~AnalysisResultConcept() = default;

  /// Method to try and mark a result as invalid.
  ///
  /// When the outer analysis manager detects a change in some underlying
  /// unit of the IR, it will call this method on all of the results cached.
  ///
  /// \p PA is a set of preserved analyses which can be used to avoid
  /// invalidation because the pass which changed the underlying IR took care
  /// to update or preserve the analysis result in some way.
  ///
  /// \p Inv is typically a \c AnalysisManager::Invalidator object that can be
  /// used by a particular analysis result to discover if other analyses
  /// results are also invalidated in the event that this result depends on
  /// them. See the documentation in the \c AnalysisManager for more details.
  ///
  /// \returns true if the result is indeed invalid (the default).
  virtual bool invalidate(IRUnitT &IR, const PreservedAnalysesT &PA,
                          InvalidatorT &Inv) = 0;
};

/// SFINAE metafunction for computing whether \c ResultT provides an
/// \c invalidate member function.
template <typename IRUnitT, typename ResultT> class ResultHasInvalidateMethod {
  using EnabledType = char;
  struct DisabledType {
    char a, b;
  };

  // Purely to help out MSVC which fails to disable the below specialization,
  // explicitly enable using the result type's invalidate routine if we can
  // successfully call that routine.
  template <typename T> struct Nonce { using Type = EnabledType; };
  template <typename T>
  static typename Nonce<decltype(std::declval<T>().invalidate(
      std::declval<IRUnitT &>(), std::declval<PreservedAnalyses>()))>::Type
      check(rank<2>);

  // First we define an overload that can only be taken if there is no
  // invalidate member. We do this by taking the address of an invalidate
  // member in an adjacent base class of a derived class. This would be
  // ambiguous if there were an invalidate member in the result type.
  template <typename T, typename U> static DisabledType NonceFunction(T U::*);
  struct CheckerBase { int invalidate; };
  template <typename T> struct Checker : CheckerBase, T {};
  template <typename T>
  static decltype(NonceFunction(&Checker<T>::invalidate)) check(rank<1>);

  // Now we have the fallback that will only be reached when there is an
  // invalidate member, and enables the trait.
  template <typename T>
  static EnabledType check(rank<0>);

public:
  enum { Value = sizeof(check<ResultT>(rank<2>())) == sizeof(EnabledType) };
};

/// Wrapper to model the analysis result concept.
///
/// By default, this will implement the invalidate method with a trivial
/// implementation so that the actual analysis result doesn't need to provide
/// an invalidation handler. It is only selected when the invalidation handler
/// is not part of the ResultT's interface.
template <typename IRUnitT, typename PassT, typename ResultT,
          typename PreservedAnalysesT, typename InvalidatorT,
          bool HasInvalidateHandler =
              ResultHasInvalidateMethod<IRUnitT, ResultT>::Value>
struct AnalysisResultModel;

/// Specialization of \c AnalysisResultModel which provides the default
/// invalidate functionality.
template <typename IRUnitT, typename PassT, typename ResultT,
          typename PreservedAnalysesT, typename InvalidatorT>
struct AnalysisResultModel<IRUnitT, PassT, ResultT, PreservedAnalysesT,
                           InvalidatorT, false>
    : AnalysisResultConcept<IRUnitT, PreservedAnalysesT, InvalidatorT> {
  explicit AnalysisResultModel(ResultT Result) : Result(std::move(Result)) {}
  // We have to explicitly define all the special member functions because MSVC
  // refuses to generate them.
  AnalysisResultModel(const AnalysisResultModel &Arg) : Result(Arg.Result) {}
  AnalysisResultModel(AnalysisResultModel &&Arg)
      : Result(std::move(Arg.Result)) {}

  friend void swap(AnalysisResultModel &LHS, AnalysisResultModel &RHS) {
    using std::swap;
    swap(LHS.Result, RHS.Result);
  }

  AnalysisResultModel &operator=(AnalysisResultModel RHS) {
    swap(*this, RHS);
    return *this;
  }

  /// The model bases invalidation solely on being in the preserved set.
  //
  // FIXME: We should actually use two different concepts for analysis results
  // rather than two different models, and avoid the indirect function call for
  // ones that use the trivial behavior.
  bool invalidate(IRUnitT &, const PreservedAnalysesT &PA,
                  InvalidatorT &) override {
    auto PAC = PA.template getChecker<PassT>();
    return !PAC.preserved() &&
           !PAC.template preservedSet<AllAnalysesOn<IRUnitT>>();
  }

  ResultT Result;
};

/// Specialization of \c AnalysisResultModel which delegates invalidate
/// handling to \c ResultT.
template <typename IRUnitT, typename PassT, typename ResultT,
          typename PreservedAnalysesT, typename InvalidatorT>
struct AnalysisResultModel<IRUnitT, PassT, ResultT, PreservedAnalysesT,
                           InvalidatorT, true>
    : AnalysisResultConcept<IRUnitT, PreservedAnalysesT, InvalidatorT> {
  explicit AnalysisResultModel(ResultT Result) : Result(std::move(Result)) {}
  // We have to explicitly define all the special member functions because MSVC
  // refuses to generate them.
  AnalysisResultModel(const AnalysisResultModel &Arg) : Result(Arg.Result) {}
  AnalysisResultModel(AnalysisResultModel &&Arg)
      : Result(std::move(Arg.Result)) {}

  friend void swap(AnalysisResultModel &LHS, AnalysisResultModel &RHS) {
    using std::swap;
    swap(LHS.Result, RHS.Result);
  }

  AnalysisResultModel &operator=(AnalysisResultModel RHS) {
    swap(*this, RHS);
    return *this;
  }

  /// The model delegates to the \c ResultT method.
  bool invalidate(IRUnitT &IR, const PreservedAnalysesT &PA,
                  InvalidatorT &Inv) override {
    return Result.invalidate(IR, PA, Inv);
  }

  ResultT Result;
};

/// Abstract concept of an analysis pass.
///
/// This concept is parameterized over the IR unit that it can run over and
/// produce an analysis result.
template <typename IRUnitT, typename PreservedAnalysesT, typename InvalidatorT,
          typename... ExtraArgTs>
struct AnalysisPassConcept {
  virtual ~AnalysisPassConcept() = default;

  /// Method to run this analysis over a unit of IR.
  /// \returns A unique_ptr to the analysis result object to be queried by
  /// users.
  virtual std::unique_ptr<
      AnalysisResultConcept<IRUnitT, PreservedAnalysesT, InvalidatorT>>
  run(IRUnitT &IR, AnalysisManager<IRUnitT, ExtraArgTs...> &AM,
      ExtraArgTs... ExtraArgs) = 0;

  /// Polymorphic method to access the name of a pass.
  virtual StringRef name() const = 0;
};

/// Wrapper to model the analysis pass concept.
///
/// Can wrap any type which implements a suitable \c run method. The method
/// must accept an \c IRUnitT& and an \c AnalysisManager<IRUnitT>& as arguments
/// and produce an object which can be wrapped in a \c AnalysisResultModel.
template <typename IRUnitT, typename PassT, typename PreservedAnalysesT,
          typename InvalidatorT, typename... ExtraArgTs>
struct AnalysisPassModel : AnalysisPassConcept<IRUnitT, PreservedAnalysesT,
                                               InvalidatorT, ExtraArgTs...> {
  explicit AnalysisPassModel(PassT Pass) : Pass(std::move(Pass)) {}
  // We have to explicitly define all the special member functions because MSVC
  // refuses to generate them.
  AnalysisPassModel(const AnalysisPassModel &Arg) : Pass(Arg.Pass) {}
  AnalysisPassModel(AnalysisPassModel &&Arg) : Pass(std::move(Arg.Pass)) {}

  friend void swap(AnalysisPassModel &LHS, AnalysisPassModel &RHS) {
    using std::swap;
    swap(LHS.Pass, RHS.Pass);
  }

  AnalysisPassModel &operator=(AnalysisPassModel RHS) {
    swap(*this, RHS);
    return *this;
  }

  // FIXME: Replace PassT::Result with type traits when we use C++11.
  using ResultModelT =
      AnalysisResultModel<IRUnitT, PassT, typename PassT::Result,
                          PreservedAnalysesT, InvalidatorT>;

  /// The model delegates to the \c PassT::run method.
  ///
  /// The return is wrapped in an \c AnalysisResultModel.
  std::unique_ptr<
      AnalysisResultConcept<IRUnitT, PreservedAnalysesT, InvalidatorT>>
  run(IRUnitT &IR, AnalysisManager<IRUnitT, ExtraArgTs...> &AM,
      ExtraArgTs... ExtraArgs) override {
    return std::make_unique<ResultModelT>(
        Pass.run(IR, AM, std::forward<ExtraArgTs>(ExtraArgs)...));
  }

  /// The model delegates to a static \c PassT::name method.
  ///
  /// The returned string ref must point to constant immutable data!
  StringRef name() const override { return PassT::name(); }

  PassT Pass;
};

} // end namespace detail

} // end namespace llvm

#endif // LLVM_IR_PASSMANAGERINTERNAL_H