MachineIDFSSAUpdater.h

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//===- MachineIDFSSAUpdater.h - Unstructured SSA Update Tool ----*- 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
//
//===----------------------------------------------------------------------===//
//
// This file declares the MachineIDFSSAUpdater class.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CODEGEN_MACHINEIDFSSAUPDATER_H
#define LLVM_CODEGEN_MACHINEIDFSSAUPDATER_H
 
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Register.h"
 
namespace llvm {
 
class MachineDominatorTree;
class MachineInstrBuilder;
class MachineBasicBlock;
class TargetInstrInfo;
 
class MachineIDFSSAUpdater {
  struct BBValueInfo {
    Register LiveInValue;
    Register LiveOutValue;
  };
 
  MachineDominatorTree &DT;
  MachineRegisterInfo &MRI;
  const TargetInstrInfo &TII;
  MachineRegisterInfo::VRegAttrs RegAttrs;
 
  SmallVector<std::pair<MachineBasicBlock *, Register>, 4> Defines;
  SmallVector<MachineBasicBlock *, 4> UseBlocks;
  DenseMap<MachineBasicBlock *, BBValueInfo> BBInfos;
 
  MachineInstrBuilder createInst(unsigned Opc, MachineBasicBlock *BB,
                                 MachineBasicBlock::iterator I);
 
  // IsLiveOut indicates whether we are computing live-out values (true) or
  // live-in values (false).
  Register computeValue(MachineBasicBlock *BB, bool IsLiveOut);
 
public:
  MachineIDFSSAUpdater(MachineDominatorTree &DT, MachineFunction &MF,
                       const MachineRegisterInfo::VRegAttrs &RegAttr)
      : DT(DT), MRI(MF.getRegInfo()), TII(*MF.getSubtarget().getInstrInfo()),
        RegAttrs(RegAttr) {}
 
  MachineIDFSSAUpdater(MachineDominatorTree &DT, MachineFunction &MF,
                       Register Reg)
      : MachineIDFSSAUpdater(DT, MF, MF.getRegInfo().getVRegAttrs(Reg)) {}
 
  /// Indicate that a rewritten value is available in the specified block
  /// with the specified value. Must be called before invoking Calculate().
  void addAvailableValue(MachineBasicBlock *BB, Register V) {
    Defines.emplace_back(BB, V);
  }
 
  /// Record a basic block that uses the value. This method should be called for
  /// every basic block where the value will be used. Must be called before
  /// invoking Calculate().
  void addUseBlock(MachineBasicBlock *BB) { UseBlocks.push_back(BB); }
 
  /// Calculate and insert necessary PHI nodes for SSA form.
  /// Must be called after registering all definitions and uses.
  void calculate();
 
  /// See SSAUpdater::GetValueInMiddleOfBlock description.
  Register getValueInMiddleOfBlock(MachineBasicBlock *BB);
};
 
} // end namespace llvm
 
#endif // LLVM_CODEGEN_MACHINEIDFSSAUPDATER_H