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
20namespace llvm {
21
22class WebAssemblyFrameLowering final : public TargetFrameLowering {
23public:
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 hasReservedCallFrame(const MachineFunction &MF) const override;
45 bool isSupportedStackID(TargetStackID::Value ID) const override;
46 DwarfFrameBase getDwarfFrameBase(const MachineFunction &MF) const override;
47
48 bool needsPrologForEH(const MachineFunction &MF) const;
49
50 /// Write SP back to __stack_pointer global.
51 void writeSPToGlobal(unsigned SrcReg, MachineFunction &MF,
52 MachineBasicBlock &MBB,
53 MachineBasicBlock::iterator &InsertStore,
54 const DebugLoc &DL) const;
55
56 // Returns the index of the WebAssembly local to which the stack object
57 // FrameIndex in MF should be allocated, or std::nullopt.
58 static std::optional<unsigned> getLocalForStackObject(MachineFunction &MF,
59 int FrameIndex);
60
61 static unsigned getSPReg(const MachineFunction &MF);
62 static unsigned getFPReg(const MachineFunction &MF);
63 static unsigned getOpcConst(const MachineFunction &MF);
64 static unsigned getOpcAdd(const MachineFunction &MF);
65 static unsigned getOpcSub(const MachineFunction &MF);
66 static unsigned getOpcAnd(const MachineFunction &MF);
67 static unsigned getOpcGlobGet(const MachineFunction &MF);
68 static unsigned getOpcGlobSet(const MachineFunction &MF);
69
70protected:
71 bool hasFPImpl(const MachineFunction &MF) const override;
72
73private:
74 bool hasBP(const MachineFunction &MF) const;
75 bool needsSPForLocalFrame(const MachineFunction &MF) const;
76 bool needsSP(const MachineFunction &MF) const;
77 bool needsSPWriteback(const MachineFunction &MF) const;
78};
79
80} // end namespace llvm
81
82#endif
83