1 // WebAssemblyFrameLowering.h - TargetFrameLowering for WebAssembly -*- 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 /// \file
11 /// This class implements WebAssembly-specific bits of
12 /// TargetFrameLowering class.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYFRAMELOWERING_H
17 #define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYFRAMELOWERING_H
18 
19 #include "llvm/CodeGen/TargetFrameLowering.h"
20 
21 namespace llvm {
22 class MachineFrameInfo;
23 
24 class WebAssemblyFrameLowering final : public TargetFrameLowering {
25 public:
26   /// Size of the red zone for the user stack (leaf functions can use this much
27   /// space below the stack pointer without writing it back to __stack_pointer
28   /// global).
29   // TODO: (ABI) Revisit and decide how large it should be.
30   static const size_t RedZoneSize = 128;
31 
WebAssemblyFrameLowering()32   WebAssemblyFrameLowering()
33       : TargetFrameLowering(StackGrowsDown, /*StackAlignment=*/16,
34                             /*LocalAreaOffset=*/0,
35                             /*TransientStackAlignment=*/16,
36                             /*StackRealignable=*/true) {}
37 
38   MachineBasicBlock::iterator
39   eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
40                                 MachineBasicBlock::iterator I) const override;
41 
42   /// These methods insert prolog and epilog code into the function.
43   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
44   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
45 
46   bool hasFP(const MachineFunction &MF) const override;
47   bool hasReservedCallFrame(const MachineFunction &MF) const override;
48 
49   bool needsPrologForEH(const MachineFunction &MF) const;
50 
51   /// Write SP back to __stack_pointer global.
52   void writeSPToGlobal(unsigned SrcReg, MachineFunction &MF,
53                        MachineBasicBlock &MBB,
54                        MachineBasicBlock::iterator &InsertStore,
55                        const DebugLoc &DL) const;
56 
57 private:
58   bool hasBP(const MachineFunction &MF) const;
59   bool needsSPForLocalFrame(const MachineFunction &MF) const;
60   bool needsSP(const MachineFunction &MF) const;
61   bool needsSPWriteback(const MachineFunction &MF) const;
62 };
63 
64 } // end namespace llvm
65 
66 #endif
67