Pass.h

Go to the documentation of this file.

//===- Pass.h - Base classes for compiler passes ----------------*- 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
//
//===----------------------------------------------------------------------===//
 
#ifndef MLIR_PASS_PASS_H
#define MLIR_PASS_PASS_H
 
#include "mlir/IR/Action.h"
#include "mlir/Pass/AnalysisManager.h"
#include "mlir/Pass/PassRegistry.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/Statistic.h"
#include <optional>
 
namespace mlir {
class PassInstrumentation;
namespace detail {
class OpToOpPassAdaptor;
struct OpPassManagerImpl;
 
/// The state for a single execution of a pass. This provides a unified
/// interface for accessing and initializing necessary state for pass execution.
struct PassExecutionState {
  PassExecutionState(Operation *ir, AnalysisManager analysisManager,
                     function_ref<LogicalResult(OpPassManager &, Operation *)>
                         pipelineExecutor)
      : irAndPassFailed(ir, false), analysisManager(analysisManager),
        pipelineExecutor(pipelineExecutor) {}
 
  /// The current operation being transformed and a bool for if the pass
  /// signaled a failure.
  llvm::PointerIntPair<Operation *, 1, bool> irAndPassFailed;
 
  /// The analysis manager for the operation.
  AnalysisManager analysisManager;
 
  /// The set of preserved analyses for the current execution.
  detail::PreservedAnalyses preservedAnalyses;
 
  /// This is a callback in the PassManager that allows to schedule dynamic
  /// pipelines that will be rooted at the provided operation.
  function_ref<LogicalResult(OpPassManager &, Operation *)> pipelineExecutor;
};
} // namespace detail
 
/// The abstract base pass class. This class contains information describing the
/// derived pass object, e.g its kind and abstract TypeID.
class Pass {
public:
  virtual ~Pass() = default;
 
  /// Returns the unique identifier that corresponds to this pass.
  TypeID getTypeID() const { return passID; }
 
  /// Returns the pass info for this pass, or null if unknown.
  const PassInfo *lookupPassInfo() const {
    return PassInfo::lookup(getArgument());
  }
 
  /// Returns the derived pass name.
  virtual StringRef getName() const = 0;
 
  /// Register dependent dialects for the current pass.
  /// A pass is expected to register the dialects it will create entities for
  /// (Operations, Types, Attributes), other than dialect that exists in the
  /// input. For example, a pass that converts from Linalg to Affine would
  /// register the Affine dialect but does not need to register Linalg.
  virtual void getDependentDialects(DialectRegistry &registry) const {}
 
  /// Return the command line argument used when registering this pass. Return
  /// an empty string if one does not exist.
  virtual StringRef getArgument() const { return ""; }
 
  /// Return the command line description used when registering this pass.
  /// Return an empty string if one does not exist.
  virtual StringRef getDescription() const { return ""; }
 
  /// Returns the name of the operation that this pass operates on, or
  /// std::nullopt if this is a generic OperationPass.
  std::optional<StringRef> getOpName() const { return opName; }
 
  //===--------------------------------------------------------------------===//
  // Options
  //===--------------------------------------------------------------------===//
 
  /// This class represents a specific pass option, with a provided data type.
  template <typename DataType,
            typename OptionParser = detail::PassOptions::OptionParser<DataType>>
  struct Option : public detail::PassOptions::Option<DataType, OptionParser> {
    template <typename... Args>
    Option(Pass &parent, StringRef arg, Args &&...args)
        : detail::PassOptions::Option<DataType, OptionParser>(
              parent.passOptions, arg, std::forward<Args>(args)...) {}
    using detail::PassOptions::Option<DataType, OptionParser>::operator=;
  };
  /// This class represents a specific pass option that contains a list of
  /// values of the provided data type.
  template <typename DataType,
            typename OptionParser = detail::PassOptions::OptionParser<DataType>>
  struct ListOption
      : public detail::PassOptions::ListOption<DataType, OptionParser> {
    template <typename... Args>
    ListOption(Pass &parent, StringRef arg, Args &&...args)
        : detail::PassOptions::ListOption<DataType, OptionParser>(
              parent.passOptions, arg, std::forward<Args>(args)...) {}
    using detail::PassOptions::ListOption<DataType, OptionParser>::operator=;
  };
 
  /// Attempt to initialize the options of this pass from the given string.
  /// Derived classes may override this method to hook into the point at which
  /// options are initialized, but should generally always invoke this base
  /// class variant.
  virtual LogicalResult
  initializeOptions(StringRef options,
                    function_ref<LogicalResult(const Twine &)> errorHandler);
 
  /// Prints out the pass in the textual representation of pipelines. If this is
  /// an adaptor pass, print its pass managers. When `pretty` is true, the
  /// printed pipeline is formatted for readability.
  void printAsTextualPipeline(raw_ostream &os, bool pretty = false);
 
  //===--------------------------------------------------------------------===//
  // Statistics
  //===--------------------------------------------------------------------===//
 
  /// This class represents a single pass statistic. This statistic functions
  /// similarly to an unsigned integer value, and may be updated and incremented
  /// accordingly. This class can be used to provide additional information
  /// about the transformations and analyses performed by a pass.
  class Statistic : public llvm::Statistic {
  public:
    /// The statistic is initialized by the pass owner, a name, and a
    /// description.
    Statistic(Pass *owner, const char *name, const char *description);
 
    /// Assign the statistic to the given value.
    Statistic &operator=(unsigned value);
  };
 
  /// Returns the main statistics for this pass instance.
  ArrayRef<Statistic *> getStatistics() const { return statistics; }
  MutableArrayRef<Statistic *> getStatistics() { return statistics; }
 
  /// Returns the thread sibling of this pass.
  ///
  /// If this pass was cloned by the pass manager for the sake of
  /// multi-threading, this function returns the original pass it was cloned
  /// from. This is useful for diagnostic purposes to distinguish passes that
  /// were replicated for threading purposes from passes instantiated by the
  /// user. Used to collapse passes in timing statistics.
  const Pass *getThreadingSibling() const { return threadingSibling; }
 
  /// Returns the thread sibling of this pass, or the pass itself it has no
  /// sibling. See `getThreadingSibling()` for details.
  const Pass *getThreadingSiblingOrThis() const {
    return threadingSibling ? threadingSibling : this;
  }
 
protected:
  explicit Pass(TypeID passID, std::optional<StringRef> opName = std::nullopt)
      : passID(passID), opName(opName) {}
  Pass(const Pass &other) : Pass(other.passID, other.opName) {}
  Pass &operator=(const Pass &) = delete;
  Pass(Pass &&) = delete;
  Pass &operator=(Pass &&) = delete;
 
  /// Returns the current pass state.
  detail::PassExecutionState &getPassState() {
    assert(passState && "pass state was never initialized");
    return *passState;
  }
 
  /// Return the MLIR context for the current operation being transformed.
  MLIRContext &getContext() { return *getOperation()->getContext(); }
 
  /// The polymorphic API that runs the pass over the currently held operation.
  virtual void runOnOperation() = 0;
 
  /// Initialize any complex state necessary for running this pass. This hook
  /// should not rely on any state accessible during the execution of a pass.
  /// For example, `getContext`/`getOperation`/`getAnalysis`/etc. should not be
  /// invoked within this hook.
  /// This method is invoked after all dependent dialects for the pipeline are
  /// loaded, and is not allowed to load any further dialects (override the
  /// `getDependentDialects()` for this purpose instead). Returns a LogicalResult
  /// to indicate failure, in which case the pass pipeline won't execute.
  virtual LogicalResult initialize(MLIRContext *context) { return success(); }
 
  /// Indicate if the current pass can be scheduled on the given operation type.
  /// This is useful for generic operation passes to add restrictions on the
  /// operations they operate on.
  virtual bool canScheduleOn(RegisteredOperationName opName) const = 0;
  virtual bool canScheduleOn(Operation *op) const {
    std::optional<RegisteredOperationName> registeredInfo =
        op->getName().getRegisteredInfo();
    if (!registeredInfo)
      return false;
    return canScheduleOn(*registeredInfo);
  }
 
  /// Schedule an arbitrary pass pipeline on the provided operation.
  /// This can be invoke any time in a pass to dynamic schedule more passes.
  /// The provided operation must be the current one or one nested below.
  LogicalResult runPipeline(OpPassManager &pipeline, Operation *op) {
    return passState->pipelineExecutor(pipeline, op);
  }
 
  /// A clone method to create a copy of this pass.
  std::unique_ptr<Pass> clone() const {
    auto newInst = clonePass();
    newInst->copyOptionValuesFrom(this);
    return newInst;
  }
 
  /// Return the current operation being transformed.
  Operation *getOperation() {
    return getPassState().irAndPassFailed.getPointer();
  }
 
  /// Signal that some invariant was broken when running. The IR is allowed to
  /// be in an invalid state.
  void signalPassFailure() { getPassState().irAndPassFailed.setInt(true); }
 
  /// Query an analysis for the current ir unit.
  template <typename AnalysisT>
  AnalysisT &getAnalysis() {
    return getAnalysisManager().getAnalysis<AnalysisT>();
  }
 
  /// Query an analysis for the current ir unit of a specific derived operation
  /// type.
  template <typename AnalysisT, typename OpT>
  AnalysisT &getAnalysis() {
    return getAnalysisManager().getAnalysis<AnalysisT, OpT>();
  }
 
  /// Query a cached instance of an analysis for the current ir unit if one
  /// exists.
  template <typename AnalysisT>
  std::optional<std::reference_wrapper<AnalysisT>> getCachedAnalysis() {
    return getAnalysisManager().getCachedAnalysis<AnalysisT>();
  }
 
  /// Mark all analyses as preserved.
  void markAllAnalysesPreserved() {
    getPassState().preservedAnalyses.preserveAll();
  }
 
  /// Mark the provided analyses as preserved.
  template <typename... AnalysesT>
  void markAnalysesPreserved() {
    getPassState().preservedAnalyses.preserve<AnalysesT...>();
  }
  void markAnalysesPreserved(TypeID id) {
    getPassState().preservedAnalyses.preserve(id);
  }
 
  /// Returns the analysis for the given parent operation if it exists.
  template <typename AnalysisT>
  std::optional<std::reference_wrapper<AnalysisT>>
  getCachedParentAnalysis(Operation *parent) {
    return getAnalysisManager().getCachedParentAnalysis<AnalysisT>(parent);
  }
 
  /// Returns the analysis for the parent operation if it exists.
  template <typename AnalysisT>
  std::optional<std::reference_wrapper<AnalysisT>> getCachedParentAnalysis() {
    return getAnalysisManager().getCachedParentAnalysis<AnalysisT>(
        getOperation()->getParentOp());
  }
 
  /// Returns the analysis for the given child operation if it exists.
  template <typename AnalysisT>
  std::optional<std::reference_wrapper<AnalysisT>>
  getCachedChildAnalysis(Operation *child) {
    return getAnalysisManager().getCachedChildAnalysis<AnalysisT>(child);
  }
 
  /// Returns the analysis for the given child operation, or creates it if it
  /// doesn't exist.
  template <typename AnalysisT>
  AnalysisT &getChildAnalysis(Operation *child) {
    return getAnalysisManager().getChildAnalysis<AnalysisT>(child);
  }
 
  /// Returns the analysis for the given child operation of specific derived
  /// operation type, or creates it if it doesn't exist.
  template <typename AnalysisT, typename OpTy>
  AnalysisT &getChildAnalysis(OpTy child) {
    return getAnalysisManager().getChildAnalysis<AnalysisT>(child);
  }
 
  /// Returns the current analysis manager.
  AnalysisManager getAnalysisManager() {
    return getPassState().analysisManager;
  }
 
  /// Create a copy of this pass, ignoring statistics and options.
  virtual std::unique_ptr<Pass> clonePass() const = 0;
 
  /// Copy the option values from 'other', which is another instance of this
  /// pass.
  void copyOptionValuesFrom(const Pass *other);
 
private:
  /// Out of line virtual method to ensure vtables and metadata are emitted to a
  /// single .o file.
  virtual void anchor();
 
  /// Represents a unique identifier for the pass.
  TypeID passID;
 
  /// The name of the operation that this pass operates on, or std::nullopt if
  /// this is a generic OperationPass.
  std::optional<StringRef> opName;
 
  /// The current execution state for the pass.
  std::optional<detail::PassExecutionState> passState;
 
  /// The set of statistics held by this pass.
  std::vector<Statistic *> statistics;
 
  /// The pass options registered to this pass instance.
  detail::PassOptions passOptions;
 
  /// A pointer to the pass this pass was cloned from, if the clone was made by
  /// the pass manager for the sake of multi-threading.
  const Pass *threadingSibling = nullptr;
 
  /// Allow access to 'clone'.
  friend class OpPassManager;
 
  /// Allow access to 'canScheduleOn'.
  friend detail::OpPassManagerImpl;
 
  /// Allow access to 'passState'.
  friend detail::OpToOpPassAdaptor;
 
  /// Allow access to 'passOptions'.
  friend class PassInfo;
 
  /// Allow access to 'signalPassFailure'.
  friend class PassInstrumentation;
};
 
//===----------------------------------------------------------------------===//
// Pass Model Definitions
//===----------------------------------------------------------------------===//
 
/// Pass to transform an operation of a specific type.
///
/// Operation passes must not:
///   - modify any other operations within the parent region, as other threads
///     may be manipulating them concurrently.
///   - modify any state within the parent operation, this includes adding
///     additional operations.
///
/// Derived operation passes are expected to provide the following:
///   - A 'void runOnOperation()' method.
///   - A 'StringRef getName() const' method.
///   - A 'std::unique_ptr<Pass> clonePass() const' method.
template <typename OpT = void>
class OperationPass : public Pass {
public:
  ~OperationPass() override = default;
 
protected:
  OperationPass(TypeID passID) : Pass(passID, OpT::getOperationName()) {}
  OperationPass(const OperationPass &) = default;
  OperationPass &operator=(const OperationPass &) = delete;
  OperationPass(OperationPass &&) = delete;
  OperationPass &operator=(OperationPass &&) = delete;
 
  /// Support isa/dyn_cast functionality.
  static bool classof(const Pass *pass) {
    return pass->getOpName() == OpT::getOperationName();
  }
 
  /// Indicate if the current pass can be scheduled on the given operation type.
  bool canScheduleOn(RegisteredOperationName opName) const final {
    return opName.getStringRef() == getOpName();
  }
 
  /// Return the current operation being transformed.
  OpT getOperation() { return cast<OpT>(Pass::getOperation()); }
 
  /// Query an analysis for the current operation of the specific derived
  /// operation type.
  template <typename AnalysisT>
  AnalysisT &getAnalysis() {
    return Pass::getAnalysis<AnalysisT, OpT>();
  }
};
 
/// Pass to transform an operation.
///
/// Operation passes must not:
///   - modify any other operations within the parent region, as other threads
///     may be manipulating them concurrently.
///   - modify any state within the parent operation, this includes adding
///     additional operations.
///
/// Derived operation passes are expected to provide the following:
///   - A 'void runOnOperation()' method.
///   - A 'StringRef getName() const' method.
///   - A 'std::unique_ptr<Pass> clonePass() const' method.
template <>
class OperationPass<void> : public Pass {
public:
  ~OperationPass() override = default;
 
protected:
  OperationPass(TypeID passID) : Pass(passID) {}
  OperationPass(const OperationPass &) = default;
  OperationPass &operator=(const OperationPass &) = delete;
  OperationPass(OperationPass &&) = delete;
  OperationPass &operator=(OperationPass &&) = delete;
 
  /// Indicate if the current pass can be scheduled on the given operation type.
  /// By default, generic operation passes can be scheduled on any operation.
  bool canScheduleOn(RegisteredOperationName opName) const override {
    return true;
  }
};
 
/// Pass to transform an operation that implements the given interface.
///
/// Interface passes must not:
///   - modify any other operations within the parent region, as other threads
///     may be manipulating them concurrently.
///   - modify any state within the parent operation, this includes adding
///     additional operations.
///
/// Derived interface passes are expected to provide the following:
///   - A 'void runOnOperation()' method.
///   - A 'StringRef getName() const' method.
///   - A 'std::unique_ptr<Pass> clonePass() const' method.
template <typename InterfaceT>
class InterfacePass : public OperationPass<> {
protected:
  using OperationPass::OperationPass;
 
  /// Indicate if the current pass can be scheduled on the given operation type.
  /// For an InterfacePass, this checks if the operation implements the given
  /// interface.
  bool canScheduleOn(Operation *op) const final { return isa<InterfaceT>(op); }
  bool canScheduleOn(RegisteredOperationName opName) const final {
    return opName.hasInterface<InterfaceT>();
  }
 
  /// Return the current operation being transformed.
  InterfaceT getOperation() { return cast<InterfaceT>(Pass::getOperation()); }
 
  /// Query an analysis for the current operation.
  template <typename AnalysisT>
  AnalysisT &getAnalysis() {
    return Pass::getAnalysis<AnalysisT, InterfaceT>();
  }
};
 
/// This class provides a CRTP wrapper around a base pass class to define
/// several necessary utility methods. This should only be used for passes that
/// are not suitably represented using the declarative pass specification(i.e.
/// tablegen backend).
template <typename PassT, typename BaseT>
class PassWrapper : public BaseT {
public:
  /// Support isa/dyn_cast functionality for the derived pass class.
  static bool classof(const Pass *pass) {
    return pass->getTypeID() == TypeID::get<PassT>();
  }
  ~PassWrapper() override = default;
 
protected:
  PassWrapper() : BaseT(TypeID::get<PassT>()) {}
  PassWrapper(const PassWrapper &) = default;
  PassWrapper &operator=(const PassWrapper &) = delete;
  PassWrapper(PassWrapper &&) = delete;
  PassWrapper &operator=(PassWrapper &&) = delete;
 
  /// Returns the derived pass name.
  StringRef getName() const override { return llvm::getTypeName<PassT>(); }
 
  /// A clone method to create a copy of this pass.
  std::unique_ptr<Pass> clonePass() const override {
    return std::make_unique<PassT>(*static_cast<const PassT *>(this));
  }
};
 
/// This class encapsulates the "action" of executing a single pass. This allows
/// a user of the Action infrastructure to query information about an action in
/// (for example) a breakpoint context. You could use it like this:
///
///  auto onBreakpoint = [&](const ActionActiveStack *backtrace) {
///    if (auto passExec = dyn_cast<PassExecutionAction>(anAction))
///      record(passExec.getPass());
///    return ExecutionContext::Apply;
///  };
///  ExecutionContext exeCtx(onBreakpoint);
///
class PassExecutionAction : public tracing::ActionImpl<PassExecutionAction> {
  using Base = tracing::ActionImpl<PassExecutionAction>;
 
public:
  /// Construct a PassExecutionAction. This is called by the OpToOpPassAdaptor
  /// when it calls `executeAction`.
  PassExecutionAction(ArrayRef<IRUnit> irUnits, const Pass &pass);
 
  /// The tag required by ActionImpl to identify this action.
  static constexpr StringLiteral tag = "pass-execution";
 
  /// Print a textual version of this action to `os`.
  void print(raw_ostream &os) const override;
 
  /// Get the pass that will be executed by this action. This is not a class of
  /// passes, or all instances of a pass kind, this is a single pass.
  const Pass &getPass() const { return pass; }
 
  /// Get the operation that is the base of this pass. For example, an
  /// OperationPass<ModuleOp> would return a ModuleOp.
  Operation *getOp() const;
 
public:
  /// Reference to the pass being run. Notice that this will *not* extend the
  /// lifetime of the pass, and so this class is therefore unsafe to keep past
  /// the lifetime of the `executeAction` call.
  const Pass &pass;
 
  /// The base op for this pass. For an OperationPass<ModuleOp>, we would have a
  /// ModuleOp here.
  Operation *op;
};
 
} // namespace mlir
 
/// Define a TypeID for this PassExecutionAction.
MLIR_DECLARE_EXPLICIT_TYPE_ID(::mlir::PassExecutionAction)
 
#endif // MLIR_PASS_PASS_H