text: //===-- MachineFunctionPass.h - Pass for MachineFunctions --------*-C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines the MachineFunctionPass class.  MachineFunctionPass's are
  // just FunctionPass's, except they operate on machine code as part of a code
  // generator.  Because they operate on machine code, not the LLVM
  // representation, MachineFunctionPass's are not allowed to modify the LLVM
  // representation.  Due to this limitation, the MachineFunctionPass class takes
  // care of declaring that no LLVM passes are invalidated.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CODEGEN_MACHINEFUNCTIONPASS_H
  #define LLVM_CODEGEN_MACHINEFUNCTIONPASS_H
  
  #include "llvm/CodeGen/MachineFunction.h"
  #include "llvm/Pass.h"
  
  namespace llvm {
  
  /// MachineFunctionPass - This class adapts the FunctionPass interface to
  /// allow convenient creation of passes that operate on the MachineFunction
  /// representation. Instead of overriding runOnFunction, subclasses
  /// override runOnMachineFunction.
  class MachineFunctionPass : public FunctionPass {
  public:
    bool doInitialization(Module&) override {
      // Cache the properties info at module-init time so we don't have to
      // construct them for every function.
      RequiredProperties = getRequiredProperties();
      SetProperties = getSetProperties();
      ClearedProperties = getClearedProperties();
      return false;
    }
  protected:
    explicit MachineFunctionPass(char &ID) : FunctionPass(ID) {}
  
    /// runOnMachineFunction - This method must be overloaded to perform the
    /// desired machine code transformation or analysis.
    ///
    virtual bool runOnMachineFunction(MachineFunction &MF) = 0;
  
    /// getAnalysisUsage - Subclasses that override getAnalysisUsage
    /// must call this.
    ///
    /// For MachineFunctionPasses, calling AU.preservesCFG() indicates that
    /// the pass does not modify the MachineBasicBlock CFG.
    ///
    void getAnalysisUsage(AnalysisUsage &AU) const override;
  
    virtual MachineFunctionProperties getRequiredProperties() const {
      return MachineFunctionProperties();
    }
    virtual MachineFunctionProperties getSetProperties() const {
      return MachineFunctionProperties();
    }
    virtual MachineFunctionProperties getClearedProperties() const {
      return MachineFunctionProperties();
    }
  
  private:
    MachineFunctionProperties RequiredProperties;
    MachineFunctionProperties SetProperties;
    MachineFunctionProperties ClearedProperties;
  
    /// createPrinterPass - Get a machine function printer pass.
    Pass *createPrinterPass(raw_ostream &O,
                            const std::string &Banner) const override;
  
    bool runOnFunction(Function &F) override;
  };
  
  } // End llvm namespace
  
  #endif
  