MachineOptimizationRemarkEmitter.h

///===- MachineOptimizationRemarkEmitter.h - Opt Diagnostics -*- C++ -*----===//
///
///                     The LLVM Compiler Infrastructure
///
/// This file is distributed under the University of Illinois Open Source
/// License. See LICENSE.TXT for details.
///
///===---------------------------------------------------------------------===//
/// \file
/// Optimization diagnostic interfaces for machine passes.  It's packaged as an
/// analysis pass so that by using this service passes become dependent on MBFI
/// as well.  MBFI is used to compute the "hotness" of the diagnostic message.
///
///===---------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_MACHINEOPTIMIZATIONREMARKEMITTER_H
#define LLVM_CODEGEN_MACHINEOPTIMIZATIONREMARKEMITTER_H

#include "llvm/Analysis/OptimizationDiagnosticInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"

namespace llvm {
class MachineBasicBlock;
class MachineBlockFrequencyInfo;

/// \brief Common features for diagnostics dealing with optimization remarks
/// that are used by machine passes.
class DiagnosticInfoMIROptimization : public DiagnosticInfoOptimizationBase {
public:
  DiagnosticInfoMIROptimization(enum DiagnosticKind Kind, const char *PassName,
                                StringRef RemarkName, const DebugLoc &DLoc,
                                MachineBasicBlock *MBB)
      : DiagnosticInfoOptimizationBase(Kind, DS_Remark, PassName, RemarkName,
                                       *MBB->getParent()->getFunction(), DLoc),
        MBB(MBB) {}

  static bool classof(const DiagnosticInfo *DI) {
    return DI->getKind() >= DK_FirstMachineRemark &&
           DI->getKind() <= DK_LastMachineRemark;
  }

  const MachineBasicBlock *getBlock() const { return MBB; }

private:
  MachineBasicBlock *MBB;
};

/// Diagnostic information for applied optimization remarks.
class MachineOptimizationRemark : public DiagnosticInfoMIROptimization {
public:
  /// \p PassName is the name of the pass emitting this diagnostic. If this name
  /// matches the regular expression given in -Rpass=, then the diagnostic will
  /// be emitted.  \p RemarkName is a textual identifier for the remark.  \p
  /// DLoc is the debug location and \p MBB is the block that the optimization
  /// operates in.
  MachineOptimizationRemark(const char *PassName, StringRef RemarkName,
                            const DebugLoc &DLoc, MachineBasicBlock *MBB)
      : DiagnosticInfoMIROptimization(DK_MachineOptimizationRemark, PassName,
                                      RemarkName, DLoc, MBB) {}

  static bool classof(const DiagnosticInfo *DI) {
    return DI->getKind() == DK_MachineOptimizationRemark;
  }

  /// \see DiagnosticInfoOptimizationBase::isEnabled.
  bool isEnabled() const override {
    return OptimizationRemark::isEnabled(getPassName());
  }
};

/// Diagnostic information for missed-optimization remarks.
class MachineOptimizationRemarkMissed : public DiagnosticInfoMIROptimization {
public:
  /// \p PassName is the name of the pass emitting this diagnostic. If this name
  /// matches the regular expression given in -Rpass-missed=, then the
  /// diagnostic will be emitted.  \p RemarkName is a textual identifier for the
  /// remark.  \p DLoc is the debug location and \p MBB is the block that the
  /// optimization operates in.
  MachineOptimizationRemarkMissed(const char *PassName, StringRef RemarkName,
                                  const DebugLoc &DLoc, MachineBasicBlock *MBB)
      : DiagnosticInfoMIROptimization(DK_MachineOptimizationRemarkMissed,
                                      PassName, RemarkName, DLoc, MBB) {}

  static bool classof(const DiagnosticInfo *DI) {
    return DI->getKind() == DK_MachineOptimizationRemarkMissed;
  }

  /// \see DiagnosticInfoOptimizationBase::isEnabled.
  bool isEnabled() const override {
    return OptimizationRemarkMissed::isEnabled(getPassName());
  }
};

/// Diagnostic information for optimization analysis remarks.
class MachineOptimizationRemarkAnalysis : public DiagnosticInfoMIROptimization {
public:
  /// \p PassName is the name of the pass emitting this diagnostic. If this name
  /// matches the regular expression given in -Rpass-analysis=, then the
  /// diagnostic will be emitted.  \p RemarkName is a textual identifier for the
  /// remark.  \p DLoc is the debug location and \p MBB is the block that the
  /// optimization operates in.
  MachineOptimizationRemarkAnalysis(const char *PassName, StringRef RemarkName,
                                    const DebugLoc &DLoc,
                                    MachineBasicBlock *MBB)
      : DiagnosticInfoMIROptimization(DK_MachineOptimizationRemarkAnalysis,
                                      PassName, RemarkName, DLoc, MBB) {}

  static bool classof(const DiagnosticInfo *DI) {
    return DI->getKind() == DK_MachineOptimizationRemarkAnalysis;
  }

  /// \see DiagnosticInfoOptimizationBase::isEnabled.
  bool isEnabled() const override {
    return OptimizationRemarkAnalysis::isEnabled(getPassName());
  }
};

/// The optimization diagnostic interface.
///
/// It allows reporting when optimizations are performed and when they are not
/// along with the reasons for it.  Hotness information of the corresponding
/// code region can be included in the remark if DiagnosticHotnessRequested is
/// enabled in the LLVM context.
class MachineOptimizationRemarkEmitter {
public:
  MachineOptimizationRemarkEmitter(MachineFunction &MF,
                                   MachineBlockFrequencyInfo *MBFI)
      : MF(MF), MBFI(MBFI) {}

  /// Emit an optimization remark.
  void emit(DiagnosticInfoOptimizationBase &OptDiag);

  /// \brief Whether we allow for extra compile-time budget to perform more
  /// analysis to be more informative.
  ///
  /// This is useful to enable additional missed optimizations to be reported
  /// that are normally too noisy.  In this mode, we can use the extra analysis
  /// (1) to filter trivial false positives or (2) to provide more context so
  /// that non-trivial false positives can be quickly detected by the user.
  bool allowExtraAnalysis() const {
    // For now, only allow this with -fsave-optimization-record since the -Rpass
    // options are handled in the front-end.
    return MF.getFunction()->getContext().getDiagnosticsOutputFile();
  }

private:
  MachineFunction &MF;

  /// MBFI is only set if hotness is requested.
  MachineBlockFrequencyInfo *MBFI;

  /// Compute hotness from IR value (currently assumed to be a block) if PGO is
  /// available.
  Optional<uint64_t> computeHotness(const MachineBasicBlock &MBB);

  /// Similar but use value from \p OptDiag and update hotness there.
  void computeHotness(DiagnosticInfoMIROptimization &Remark);

  /// \brief Only allow verbose messages if we know we're filtering by hotness
  /// (BFI is only set in this case).
  bool shouldEmitVerbose() { return MBFI != nullptr; }
};

/// The analysis pass
///
/// Note that this pass shouldn't generally be marked as preserved by other
/// passes.  It's holding onto BFI, so if the pass does not preserve BFI, BFI
/// could be freed.
class MachineOptimizationRemarkEmitterPass : public MachineFunctionPass {
  std::unique_ptr<MachineOptimizationRemarkEmitter> ORE;

public:
  MachineOptimizationRemarkEmitterPass();

  bool runOnMachineFunction(MachineFunction &MF) override;

  void getAnalysisUsage(AnalysisUsage &AU) const override;

  MachineOptimizationRemarkEmitter &getORE() {
    assert(ORE && "pass not run yet");
    return *ORE;
  }

  static char ID;
};
}

#endif