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 class MachineFrameInfo;
22 
23 class WebAssemblyFrameLowering final : public TargetFrameLowering {
24 public:
25   /// Size of the red zone for the user stack (leaf functions can use this much
26   /// space below the stack pointer without writing it back to __stack_pointer
27   /// global).
28   // TODO: (ABI) Revisit and decide how large it should be.
29   static const size_t RedZoneSize = 128;
30 
31   WebAssemblyFrameLowering()
32       : TargetFrameLowering(StackGrowsDown, /*StackAlignment=*/Align(16),
33                             /*LocalAreaOffset=*/0,
34                             /*TransientStackAlignment=*/Align(16),
35                             /*StackRealignable=*/true) {}
36 
37   MachineBasicBlock::iterator
38   eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
39                                 MachineBasicBlock::iterator I) const override;
40 
41   /// These methods insert prolog and epilog code into the function.
42   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
43   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
44 
45   bool hasFP(const MachineFunction &MF) const override;
46   bool hasReservedCallFrame(const MachineFunction &MF) 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 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