llvm-project/llvm/lib/CodeGen/AntiDepBreaker.h

//=- llvm/CodeGen/AntiDepBreaker.h - Anti-Dependence Breaking -*- C++ -*-=//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the AntiDepBreaker class, which implements
// anti-dependence breaking heuristics for post-register-allocation scheduling.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_CODEGEN_ANTIDEPBREAKER_H
#define LLVM_LIB_CODEGEN_ANTIDEPBREAKER_H

#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include <vector>

namespace llvm {

/// This class works in conjunction with the post-RA scheduler to rename
/// registers to break register anti-dependencies (WAR hazards).
class AntiDepBreaker {
public:
  typedef std::vector<std::pair<MachineInstr *, MachineInstr *> > 
    DbgValueVector;

  virtual ~AntiDepBreaker();

  /// Initialize anti-dep breaking for a new basic block.
  virtual void StartBlock(MachineBasicBlock *BB) =0;

  /// Identifiy anti-dependencies within a basic-block region and break them by
  /// renaming registers. Return the number of anti-dependencies broken.
  virtual unsigned BreakAntiDependencies(const std::vector<SUnit>& SUnits,
                                         MachineBasicBlock::iterator Begin,
                                         MachineBasicBlock::iterator End,
                                         unsigned InsertPosIndex,
                                         DbgValueVector &DbgValues) = 0;
  
  /// Update liveness information to account for the current
  /// instruction, which will not be scheduled.
  virtual void Observe(MachineInstr *MI, unsigned Count,
                       unsigned InsertPosIndex) =0;
  
  /// Finish anti-dep breaking for a basic block.
  virtual void FinishBlock() =0;

  /// Update DBG_VALUE if dependency breaker is updating
  /// other machine instruction to use NewReg.
  void UpdateDbgValue(MachineInstr *MI, unsigned OldReg, unsigned NewReg) {
    assert (MI->isDebugValue() && "MI is not DBG_VALUE!");
    if (MI && MI->getOperand(0).isReg() && MI->getOperand(0).getReg() == OldReg)
      MI->getOperand(0).setReg(NewReg);
  }
};

}

#endif