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 90