llvm/lib/Target/ARM/Thumb1FrameLowering.h

   1 //===- Thumb1FrameLowering.h - Thumb1-specific frame info stuff ---*- 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_TARGET_ARM_THUMB1FRAMELOWERING_H
  10 #define LLVM_LIB_TARGET_ARM_THUMB1FRAMELOWERING_H
  11
  12 #include "ARMFrameLowering.h"
  13
  14 namespace llvm {
  15
  16 class ARMSubtarget;
  17 class MachineFunction;
  18
  19 class Thumb1FrameLowering : public ARMFrameLowering {
  20 public:
  21   explicit Thumb1FrameLowering(const ARMSubtarget &sti);
  22
  23   /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
  24   /// the function.
  25   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
  26   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
  27
  28   bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
  29                                  MachineBasicBlock::iterator MI,
  30                                  ArrayRef<CalleeSavedInfo> CSI,
  31                                  const TargetRegisterInfo *TRI) const override;
  32   bool
  33   restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
  34                               MachineBasicBlock::iterator MI,
  35                               MutableArrayRef<CalleeSavedInfo> CSI,
  36                               const TargetRegisterInfo *TRI) const override;
  37
  38   bool hasReservedCallFrame(const MachineFunction &MF) const override;
  39
  40   MachineBasicBlock::iterator
  41   eliminateCallFramePseudoInstr(MachineFunction &MF,
  42                                 MachineBasicBlock &MBB,
  43                                 MachineBasicBlock::iterator MI) const override;
  44
  45   /// Check whether or not the given \p MBB can be used as a epilogue
  46   /// for the target.
  47   /// The epilogue will be inserted before the first terminator of that block.
  48   /// This method is used by the shrink-wrapping pass to decide if
  49   /// \p MBB will be correctly handled by the target.
  50   bool canUseAsEpilogue(const MachineBasicBlock &MBB) const override;
  51
  52   /// Disable shrink wrap as tBfar/BL will be used to adjust for long jumps.
  53   bool enableShrinkWrapping(const MachineFunction &MF) const override {
  54     return false;
  55   }
  56
  57 private:
  58   /// Check if the frame lowering of \p MF needs a special fixup
  59   /// code sequence for the epilogue.
  60   /// Unlike T2 and ARM mode, the T1 pop instruction cannot restore
  61   /// to LR, and we can't pop the value directly to the PC when
  62   /// we need to update the SP after popping the value. So instead
  63   /// we have to emit:
  64   ///   POP {r3}
  65   ///   ADD sp, #offset
  66   ///   BX r3
  67   /// If this would clobber a return value, then generate this sequence instead:
  68   ///   MOV ip, r3
  69   ///   POP {r3}
  70   ///   ADD sp, #offset
  71   ///   MOV lr, r3
  72   ///   MOV r3, ip
  73   ///   BX lr
  74   bool needPopSpecialFixUp(const MachineFunction &MF) const;
  75
  76   /// Emit the special fixup code sequence for the epilogue.
  77   /// \see needPopSpecialFixUp for more details.
  78   /// \p DoIt, tells this method whether or not to actually insert
  79   /// the code sequence in \p MBB. I.e., when \p DoIt is false,
  80   /// \p MBB is left untouched.
  81   /// \returns For \p DoIt == true: True when the emission succeeded
  82   /// false otherwise. For \p DoIt == false: True when the emission
  83   /// would have been possible, false otherwise.
  84   bool emitPopSpecialFixUp(MachineBasicBlock &MBB, bool DoIt) const;
  85 };
  86
  87 } // end namespace llvm
  88
  89 #endif // LLVM_LIB_TARGET_ARM_THUMB1FRAMELOWERING_H