1 // WebAssemblyFrameLowering.h - TargetFrameLowering for WebAssembly -*- 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 /// \file
10 /// This class implements WebAssembly-specific bits of
11 /// TargetFrameLowering class.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYFRAMELOWERING_H
16 #define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYFRAMELOWERING_H
17 
18 #include "llvm/CodeGen/TargetFrameLowering.h"
19 
20 namespace llvm {
21 
22 class WebAssemblyFrameLowering final : public TargetFrameLowering {
23 public:
24   /// Size of the red zone for the user stack (leaf functions can use this much
25   /// space below the stack pointer without writing it back to __stack_pointer
26   /// global).
27   // TODO: (ABI) Revisit and decide how large it should be.
28   static const size_t RedZoneSize = 128;
29 
30   WebAssemblyFrameLowering()
31       : TargetFrameLowering(StackGrowsDown, /*StackAlignment=*/Align(16),
32                             /*LocalAreaOffset=*/0,
33                             /*TransientStackAlignment=*/Align(16),
34                             /*StackRealignable=*/true) {}
35 
36   MachineBasicBlock::iterator
37   eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
38                                 MachineBasicBlock::iterator I) const override;
39 
40   /// These methods insert prolog and epilog code into the function.
41   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
42   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
43 
44   bool hasFP(const MachineFunction &MF) const override;
45   bool hasReservedCallFrame(const MachineFunction &MF) const override;
46   bool isSupportedStackID(TargetStackID::Value ID) const override;
47   DwarfFrameBase getDwarfFrameBase(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   // Returns the index of the WebAssembly local to which the stack object
58   // FrameIndex in MF should be allocated, or None.
59   static Optional<unsigned> getLocalForStackObject(MachineFunction &MF,
60                                                    int FrameIndex);
61 
62   static unsigned getSPReg(const MachineFunction &MF);
63   static unsigned getFPReg(const MachineFunction &MF);
64   static unsigned getOpcConst(const MachineFunction &MF);
65   static unsigned getOpcAdd(const MachineFunction &MF);
66   static unsigned getOpcSub(const MachineFunction &MF);
67   static unsigned getOpcAnd(const MachineFunction &MF);
68   static unsigned getOpcGlobGet(const MachineFunction &MF);
69   static unsigned getOpcGlobSet(const MachineFunction &MF);
70 
71 private:
72   bool hasBP(const MachineFunction &MF) const;
73   bool needsSPForLocalFrame(const MachineFunction &MF) const;
74   bool needsSP(const MachineFunction &MF) const;
75   bool needsSPWriteback(const MachineFunction &MF) const;
76 };
77 
78 } // end namespace llvm
79 
80 #endif
81