Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- MachineSSAUpdater.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 MachineSSAUpdater class.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_MACHINESSAUPDATER_H

#define LLVM_CODEGEN_MACHINESSAUPDATER_H

#include "llvm/CodeGen/Register.h"

namespace llvm {

class MachineBasicBlock;

class MachineFunction;

class MachineInstr;

class MachineOperand;

class MachineRegisterInfo;

class TargetInstrInfo;

class TargetRegisterClass;

template<typename T> class SmallVectorImpl;

template<typename T> class SSAUpdaterTraits;

/// MachineSSAUpdater - This class updates SSA form for a set of virtual

/// registers defined in multiple blocks.  This is used when code duplication

/// or another unstructured transformation wants to rewrite a set of uses of one

/// vreg with uses of a set of vregs.

class MachineSSAUpdater {

  friend class SSAUpdaterTraits<MachineSSAUpdater>;

private:

  /// AvailableVals - This keeps track of which value to use on a per-block

  /// basis.  When we insert PHI nodes, we keep track of them here.

  //typedef DenseMap<MachineBasicBlock*, Register> AvailableValsTy;

  void *AV = nullptr;

  /// VRC - Register class of the current virtual register.

  const TargetRegisterClass *VRC;

  /// InsertedPHIs - If this is non-null, the MachineSSAUpdater adds all PHI

  /// nodes that it creates to the vector.

  SmallVectorImpl<MachineInstr*> *InsertedPHIs;

  const TargetInstrInfo *TII;

  MachineRegisterInfo *MRI;

public:

  /// MachineSSAUpdater constructor.  If InsertedPHIs is specified, it will be

  /// filled in with all PHI Nodes created by rewriting.

  explicit MachineSSAUpdater(MachineFunction &MF,

                        SmallVectorImpl<MachineInstr*> *NewPHI = nullptr);

  MachineSSAUpdater(const MachineSSAUpdater &) = delete;

  MachineSSAUpdater &operator=(const MachineSSAUpdater &) = delete;

  ~MachineSSAUpdater();

  /// Initialize - Reset this object to get ready for a new set of SSA

  /// updates.

  void Initialize(Register V);

  void Initialize(const TargetRegisterClass *RC);

  /// AddAvailableValue - Indicate that a rewritten value is available at the

  /// end of the specified block with the specified value.

  void AddAvailableValue(MachineBasicBlock *BB, Register V);

  /// HasValueForBlock - Return true if the MachineSSAUpdater already has a

  /// value for the specified block.

  bool HasValueForBlock(MachineBasicBlock *BB) const;

  /// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is

  /// live at the end of the specified block.

  Register GetValueAtEndOfBlock(MachineBasicBlock *BB);

  /// GetValueInMiddleOfBlock - Construct SSA form, materializing a value that

  /// is live in the middle of the specified block. If ExistingValueOnly is

  /// true then this will only return an existing value or $noreg; otherwise new

  /// instructions may be inserted to materialize a value.

  ///

  /// GetValueInMiddleOfBlock is the same as GetValueAtEndOfBlock except in one

  /// important case: if there is a definition of the rewritten value after the

  /// 'use' in BB.  Consider code like this:

  ///

  ///      X1 = ...

  ///   SomeBB:

  ///      use(X)

  ///      X2 = ...

  ///      br Cond, SomeBB, OutBB

  ///

  /// In this case, there are two values (X1 and X2) added to the AvailableVals

  /// set by the client of the rewriter, and those values are both live out of

  /// their respective blocks.  However, the use of X happens in the *middle* of

  /// a block.  Because of this, we need to insert a new PHI node in SomeBB to

  /// merge the appropriate values, and this value isn't live out of the block.

  Register GetValueInMiddleOfBlock(MachineBasicBlock *BB,

                                   bool ExistingValueOnly = false);

  /// RewriteUse - Rewrite a use of the symbolic value.  This handles PHI nodes,

  /// which use their value in the corresponding predecessor.  Note that this

  /// will not work if the use is supposed to be rewritten to a value defined in

  /// the same block as the use, but above it.  Any 'AddAvailableValue's added

  /// for the use's block will be considered to be below it.

  void RewriteUse(MachineOperand &U);

private:

  // If ExistingValueOnly is true, will not create any new instructions. Used

  // for debug values, which cannot modify Codegen.

  Register GetValueAtEndOfBlockInternal(MachineBasicBlock *BB,

                                        bool ExistingValueOnly = false);

};

} // end namespace llvm

#endif // LLVM_CODEGEN_MACHINESSAUPDATER_H