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_LIB_CODEGEN_MACHINELOOPUTILS_H
10 #define LLVM_LIB_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 /// Return true if PhysReg is live outside the loop, i.e. determine if it
41 /// is live in the loop exit blocks, and false otherwise.
42 bool isRegLiveInExitBlocks(MachineLoop *Loop, int PhysReg);
43 
44 } // namespace llvm
45 
46 #endif // LLVM_LIB_CODEGEN_MACHINELOOPUTILS_H
47