Home | History | Annotate | Line # | Download | only in CodeGen 
      1 //=- MachineLoopUtils.h - Helper functions for manipulating loops -*- C++ -*-=//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #ifndef LLVM_CODEGEN_MACHINELOOPUTILS_H
     10 #define LLVM_CODEGEN_MACHINELOOPUTILS_H
     11 
     12 namespace llvm {
     13 class MachineLoop;
     14 class MachineBasicBlock;
     15 class MachineRegisterInfo;
     16 class TargetInstrInfo;
     17 
     18 enum LoopPeelDirection {
     19   LPD_Front, ///< Peel the first iteration of the loop.
     20   LPD_Back   ///< Peel the last iteration of the loop.
     21 };
     22 
     23 /// Peels a single block loop. Loop must have two successors, one of which
     24 /// must be itself. Similarly it must have two predecessors, one of which must
     25 /// be itself.
     26 ///
     27 /// The loop block is copied and inserted into the CFG such that two copies of
     28 /// the loop follow on from each other. The copy is inserted either before or
     29 /// after the loop based on Direction.
     30 ///
     31 /// Phis are updated and an unconditional branch inserted at the end of the
     32 /// clone so as to execute a single iteration.
     33 ///
     34 /// The trip count of Loop is not updated.
     35 MachineBasicBlock *PeelSingleBlockLoop(LoopPeelDirection Direction,
     36                                        MachineBasicBlock *Loop,
     37                                        MachineRegisterInfo &MRI,
     38                                        const TargetInstrInfo *TII);
     39 
     40 } // namespace llvm
     41 
     42 #endif // LLVM_CODEGEN_MACHINELOOPUTILS_H
     43