1 //===-- BPFAsmPrinter.cpp - BPF LLVM assembly writer ----------------------===//
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 // This file contains a printer that converts from our internal representation
10 // of machine-dependent LLVM code to the BPF assembly language.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "BPF.h"
15 #include "BPFInstrInfo.h"
16 #include "BPFMCInstLower.h"
17 #include "BPFTargetMachine.h"
18 #include "BTFDebug.h"
19 #include "MCTargetDesc/BPFInstPrinter.h"
20 #include "TargetInfo/BPFTargetInfo.h"
21 #include "llvm/CodeGen/AsmPrinter.h"
22 #include "llvm/CodeGen/MachineConstantPool.h"
23 #include "llvm/CodeGen/MachineFunctionPass.h"
24 #include "llvm/CodeGen/MachineInstr.h"
25 #include "llvm/CodeGen/MachineModuleInfo.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCInst.h"
28 #include "llvm/MC/MCStreamer.h"
29 #include "llvm/MC/MCSymbol.h"
30 #include "llvm/Support/TargetRegistry.h"
31 #include "llvm/Support/raw_ostream.h"
32 using namespace llvm;
33 
34 #define DEBUG_TYPE "asm-printer"
35 
36 namespace {
37 class BPFAsmPrinter : public AsmPrinter {
38 public:
39   explicit BPFAsmPrinter(TargetMachine &TM,
40                          std::unique_ptr<MCStreamer> Streamer)
41       : AsmPrinter(TM, std::move(Streamer)) {}
42 
43   StringRef getPassName() const override { return "BPF Assembly Printer"; }
44   bool doInitialization(Module &M) override;
45   void printOperand(const MachineInstr *MI, int OpNum, raw_ostream &O);
46   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
47                        const char *ExtraCode, raw_ostream &O) override;
48   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,
49                              const char *ExtraCode, raw_ostream &O) override;
50 
51   void EmitInstruction(const MachineInstr *MI) override;
52 };
53 } // namespace
54 
55 bool BPFAsmPrinter::doInitialization(Module &M) {
56   AsmPrinter::doInitialization(M);
57 
58   // Only emit BTF when debuginfo available.
59   if (MAI->doesSupportDebugInformation() && !empty(M.debug_compile_units())) {
60     Handlers.emplace_back(llvm::make_unique<BTFDebug>(this), "emit",
61                           "Debug Info Emission", "BTF", "BTF Emission");
62   }
63 
64   return false;
65 }
66 
67 void BPFAsmPrinter::printOperand(const MachineInstr *MI, int OpNum,
68                                  raw_ostream &O) {
69   const MachineOperand &MO = MI->getOperand(OpNum);
70 
71   switch (MO.getType()) {
72   case MachineOperand::MO_Register:
73     O << BPFInstPrinter::getRegisterName(MO.getReg());
74     break;
75 
76   case MachineOperand::MO_Immediate:
77     O << MO.getImm();
78     break;
79 
80   case MachineOperand::MO_MachineBasicBlock:
81     O << *MO.getMBB()->getSymbol();
82     break;
83 
84   case MachineOperand::MO_GlobalAddress:
85     O << *getSymbol(MO.getGlobal());
86     break;
87 
88   case MachineOperand::MO_BlockAddress: {
89     MCSymbol *BA = GetBlockAddressSymbol(MO.getBlockAddress());
90     O << BA->getName();
91     break;
92   }
93 
94   case MachineOperand::MO_ExternalSymbol:
95     O << *GetExternalSymbolSymbol(MO.getSymbolName());
96     break;
97 
98   case MachineOperand::MO_JumpTableIndex:
99   case MachineOperand::MO_ConstantPoolIndex:
100   default:
101     llvm_unreachable("<unknown operand type>");
102   }
103 }
104 
105 bool BPFAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
106                                     const char *ExtraCode, raw_ostream &O) {
107   if (ExtraCode && ExtraCode[0])
108     return AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, O);
109 
110   printOperand(MI, OpNo, O);
111   return false;
112 }
113 
114 bool BPFAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
115                                           unsigned OpNum, const char *ExtraCode,
116                                           raw_ostream &O) {
117   assert(OpNum + 1 < MI->getNumOperands() && "Insufficient operands");
118   const MachineOperand &BaseMO = MI->getOperand(OpNum);
119   const MachineOperand &OffsetMO = MI->getOperand(OpNum + 1);
120   assert(BaseMO.isReg() && "Unexpected base pointer for inline asm memory operand.");
121   assert(OffsetMO.isImm() && "Unexpected offset for inline asm memory operand.");
122   int Offset = OffsetMO.getImm();
123 
124   if (ExtraCode)
125     return true; // Unknown modifier.
126 
127   if (Offset < 0)
128     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " - " << -Offset << ")";
129   else
130     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " + " << Offset << ")";
131 
132   return false;
133 }
134 
135 void BPFAsmPrinter::EmitInstruction(const MachineInstr *MI) {
136 
137   BPFMCInstLower MCInstLowering(OutContext, *this);
138 
139   MCInst TmpInst;
140   MCInstLowering.Lower(MI, TmpInst);
141   EmitToStreamer(*OutStreamer, TmpInst);
142 }
143 
144 // Force static initialization.
145 extern "C" void LLVMInitializeBPFAsmPrinter() {
146   RegisterAsmPrinter<BPFAsmPrinter> X(getTheBPFleTarget());
147   RegisterAsmPrinter<BPFAsmPrinter> Y(getTheBPFbeTarget());
148   RegisterAsmPrinter<BPFAsmPrinter> Z(getTheBPFTarget());
149 }
150