1 //===-- PPCFrameLowering.h - Define frame lowering for PowerPC --*- 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 #ifndef LLVM_LIB_TARGET_POWERPC_PPCFRAMELOWERING_H
14 #define LLVM_LIB_TARGET_POWERPC_PPCFRAMELOWERING_H
15 
16 #include "PPC.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/Target/TargetFrameLowering.h"
19 #include "llvm/Target/TargetMachine.h"
20 
21 namespace llvm {
22 class PPCSubtarget;
23 
24 class PPCFrameLowering: public TargetFrameLowering {
25   const PPCSubtarget &Subtarget;
26   const unsigned ReturnSaveOffset;
27   const unsigned TOCSaveOffset;
28   const unsigned FramePointerSaveOffset;
29   const unsigned LinkageSize;
30   const unsigned BasePointerSaveOffset;
31 
32   /**
33    * \brief Find a register that can be used in function prologue and epilogue
34    *
35    * Find a register that can be use as the scratch register in function
36    * prologue and epilogue to save various registers (Link Register, Base
37    * Pointer, etc.). Prefer R0, if it is available. If it is not available,
38    * then choose a different register.
39    *
40    * This method will return true if an available register was found (including
41    * R0). If no available registers are found, the method returns false and sets
42    * ScratchRegister to R0, as per the recommendation in the ABI.
43    *
44    * \param[in] MBB The machine basic block to find an available register for
45    * \param[in] UseAtEnd Specify whether the scratch register will be used at
46    *                     the end of the basic block (i.e., will the scratch
47    *                     register kill a register defined in the basic block)
48    * \param[out] ScratchRegister The scratch register to use
49    * \return true if a scratch register was found. false of a scratch register
50    *         was not found and R0 is being used as the default.
51    */
52   bool findScratchRegister(MachineBasicBlock *MBB,
53                            bool UseAtEnd,
54                            unsigned *ScratchRegister) const;
55 
56 public:
57   PPCFrameLowering(const PPCSubtarget &STI);
58 
59   unsigned determineFrameLayout(MachineFunction &MF,
60                                 bool UpdateMF = true,
61                                 bool UseEstimate = false) const;
62 
63   /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
64   /// the function.
65   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
66   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
67 
68   bool hasFP(const MachineFunction &MF) const override;
69   bool needsFP(const MachineFunction &MF) const;
70   void replaceFPWithRealFP(MachineFunction &MF) const;
71 
72   void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
73                             RegScavenger *RS = nullptr) const override;
74   void processFunctionBeforeFrameFinalized(MachineFunction &MF,
75                                      RegScavenger *RS = nullptr) const override;
76   void addScavengingSpillSlot(MachineFunction &MF, RegScavenger *RS) const;
77 
78   bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
79                                  MachineBasicBlock::iterator MI,
80                                  const std::vector<CalleeSavedInfo> &CSI,
81                                  const TargetRegisterInfo *TRI) const override;
82 
83   void eliminateCallFramePseudoInstr(MachineFunction &MF,
84                                   MachineBasicBlock &MBB,
85                                   MachineBasicBlock::iterator I) const override;
86 
87   bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
88                                   MachineBasicBlock::iterator MI,
89                                   const std::vector<CalleeSavedInfo> &CSI,
90                                   const TargetRegisterInfo *TRI) const override;
91 
92   /// targetHandlesStackFrameRounding - Returns true if the target is
93   /// responsible for rounding up the stack frame (probably at emitPrologue
94   /// time).
targetHandlesStackFrameRounding()95   bool targetHandlesStackFrameRounding() const override { return true; }
96 
97   /// getReturnSaveOffset - Return the previous frame offset to save the
98   /// return address.
getReturnSaveOffset()99   unsigned getReturnSaveOffset() const { return ReturnSaveOffset; }
100 
101   /// getTOCSaveOffset - Return the previous frame offset to save the
102   /// TOC register -- 64-bit SVR4 ABI only.
getTOCSaveOffset()103   unsigned getTOCSaveOffset() const { return TOCSaveOffset; }
104 
105   /// getFramePointerSaveOffset - Return the previous frame offset to save the
106   /// frame pointer.
getFramePointerSaveOffset()107   unsigned getFramePointerSaveOffset() const { return FramePointerSaveOffset; }
108 
109   /// getBasePointerSaveOffset - Return the previous frame offset to save the
110   /// base pointer.
getBasePointerSaveOffset()111   unsigned getBasePointerSaveOffset() const { return BasePointerSaveOffset; }
112 
113   /// getLinkageSize - Return the size of the PowerPC ABI linkage area.
114   ///
getLinkageSize()115   unsigned getLinkageSize() const { return LinkageSize; }
116 
117   const SpillSlot *
118   getCalleeSavedSpillSlots(unsigned &NumEntries) const override;
119 
120   bool enableShrinkWrapping(const MachineFunction &MF) const override;
121 
122   /// Methods used by shrink wrapping to determine if MBB can be used for the
123   /// function prologue/epilogue.
124   bool canUseAsPrologue(const MachineBasicBlock &MBB) const override;
125   bool canUseAsEpilogue(const MachineBasicBlock &MBB) const override;
126 };
127 } // End llvm namespace
128 
129 #endif
130