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 const std::vector<CalleeSavedInfo> &CSI, 31 const TargetRegisterInfo *TRI) const override; 32 bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB, 33 MachineBasicBlock::iterator MI, 34 std::vector<CalleeSavedInfo> &CSI, 35 const TargetRegisterInfo *TRI) const override; 36 37 bool hasReservedCallFrame(const MachineFunction &MF) const override; 38 39 MachineBasicBlock::iterator 40 eliminateCallFramePseudoInstr(MachineFunction &MF, 41 MachineBasicBlock &MBB, 42 MachineBasicBlock::iterator MI) const override; 43 44 /// Check whether or not the given \p MBB can be used as a epilogue 45 /// for the target. 46 /// The epilogue will be inserted before the first terminator of that block. 47 /// This method is used by the shrink-wrapping pass to decide if 48 /// \p MBB will be correctly handled by the target. 49 bool canUseAsEpilogue(const MachineBasicBlock &MBB) const override; 50 51 /// Disable shrink wrap as tBfar/BL will be used to adjust for long jumps. 52 bool enableShrinkWrapping(const MachineFunction &MF) const override { 53 return false; 54 } 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 namespace llvm 87 88 #endif // LLVM_LIB_TARGET_ARM_THUMB1FRAMELOWERING_H 89