LazyMachineBlockFrequencyInfo.h

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///===- LazyMachineBlockFrequencyInfo.h - Lazy Block Frequency -*- 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 is an alternative analysis pass to MachineBlockFrequencyInfo.  The
/// difference is that with this pass the block frequencies are not computed
/// when the analysis pass is executed but rather when the BFI result is
/// explicitly requested by the analysis client.
///
///===---------------------------------------------------------------------===//
 
#ifndef LLVM_CODEGEN_LAZYMACHINEBLOCKFREQUENCYINFO_H
#define LLVM_CODEGEN_LAZYMACHINEBLOCKFREQUENCYINFO_H
 
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
 
namespace llvm {
/// This is an alternative analysis pass to MachineBlockFrequencyInfo.
/// The difference is that with this pass, the block frequencies are not
/// computed when the analysis pass is executed but rather when the BFI result
/// is explicitly requested by the analysis client.
///
/// This works by checking querying if MBFI is available and otherwise
/// generating MBFI on the fly.  In this case the passes required for (LI, DT)
/// are also queried before being computed on the fly.
///
/// Note that it is expected that we wouldn't need this functionality for the
/// new PM since with the new PM, analyses are executed on demand.
 
class LazyMachineBlockFrequencyInfoPass : public MachineFunctionPass {
private:
  /// If generated on the fly this own the instance.
  mutable std::unique_ptr<MachineBlockFrequencyInfo> OwnedMBFI;
 
  /// If generated on the fly this own the instance.
  mutable std::unique_ptr<MachineLoopInfo> OwnedMLI;
 
  /// If generated on the fly this own the instance.
  mutable std::unique_ptr<MachineDominatorTree> OwnedMDT;
 
  /// The function.
  MachineFunction *MF = nullptr;
 
  /// Calculate MBFI and all other analyses that's not available and
  /// required by BFI.
  MachineBlockFrequencyInfo &calculateIfNotAvailable() const;
 
public:
  static char ID;
 
  LazyMachineBlockFrequencyInfoPass();
 
  /// Compute and return the block frequencies.
  MachineBlockFrequencyInfo &getBFI() { return calculateIfNotAvailable(); }
 
  /// Compute and return the block frequencies.
  const MachineBlockFrequencyInfo &getBFI() const {
    return calculateIfNotAvailable();
  }
 
  void getAnalysisUsage(AnalysisUsage &AU) const override;
 
  bool runOnMachineFunction(MachineFunction &F) override;
  void releaseMemory() override;
};
}
#endif