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1 //===-- Thumb1FrameLowering.h - Thumb1-specific frame info stuff --*- C++ -*-=//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_LIB_TARGET_ARM_THUMB1FRAMELOWERING_H
15 #define LLVM_LIB_TARGET_ARM_THUMB1FRAMELOWERING_H
16 
17 #include "ARMFrameLowering.h"
18 #include "Thumb1InstrInfo.h"
19 #include "ThumbRegisterInfo.h"
20 #include "llvm/Target/TargetFrameLowering.h"
21 
22 namespace llvm {
23 
24 class Thumb1FrameLowering : public ARMFrameLowering {
25 public:
26   explicit Thumb1FrameLowering(const ARMSubtarget &sti);
27 
28   /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
29   /// the function.
30   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
31   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
32 
33   bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
34                                  MachineBasicBlock::iterator MI,
35                                  const std::vector<CalleeSavedInfo> &CSI,
36                                  const TargetRegisterInfo *TRI) const override;
37   bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
38                                   MachineBasicBlock::iterator MI,
39                                   const std::vector<CalleeSavedInfo> &CSI,
40                                   const TargetRegisterInfo *TRI) const override;
41 
42   bool hasReservedCallFrame(const MachineFunction &MF) const override;
43 
44   void
45   eliminateCallFramePseudoInstr(MachineFunction &MF,
46                                 MachineBasicBlock &MBB,
47                                 MachineBasicBlock::iterator MI) const override;
48 
49   /// Check whether or not the given \p MBB can be used as a epilogue
50   /// for the target.
51   /// The epilogue will be inserted before the first terminator of that block.
52   /// This method is used by the shrink-wrapping pass to decide if
53   /// \p MBB will be correctly handled by the target.
54   bool canUseAsEpilogue(const MachineBasicBlock &MBB) const override;
55 
56 private:
57   /// Check if the frame lowering of \p MF needs a special fixup
58   /// code sequence for the epilogue.
59   /// Unlike T2 and ARM mode, the T1 pop instruction cannot restore
60   /// to LR, and we can't pop the value directly to the PC when
61   /// we need to update the SP after popping the value. So instead
62   /// we have to emit:
63   ///   POP {r3}
64   ///   ADD sp, #offset
65   ///   BX r3
66   /// If this would clobber a return value, then generate this sequence instead:
67   ///   MOV ip, r3
68   ///   POP {r3}
69   ///   ADD sp, #offset
70   ///   MOV lr, r3
71   ///   MOV r3, ip
72   ///   BX lr
73   bool needPopSpecialFixUp(const MachineFunction &MF) const;
74 
75   /// Emit the special fixup code sequence for the epilogue.
76   /// \see needPopSpecialFixUp for more details.
77   /// \p DoIt, tells this method whether or not to actually insert
78   /// the code sequence in \p MBB. I.e., when \p DoIt is false,
79   /// \p MBB is left untouched.
80   /// \returns For \p DoIt == true: True when the emission succeeded
81   /// false otherwise. For \p DoIt == false: True when the emission
82   /// would have been possible, false otherwise.
83   bool emitPopSpecialFixUp(MachineBasicBlock &MBB, bool DoIt) const;
84 };
85 
86 } // End llvm namespace
87 
88 #endif
89