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)), BTF(nullptr) {}
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 private:
54   BTFDebug *BTF;
55 };
56 } // namespace
57 
58 bool BPFAsmPrinter::doInitialization(Module &M) {
59   AsmPrinter::doInitialization(M);
60 
61   // Only emit BTF when debuginfo available.
62   if (MAI->doesSupportDebugInformation() && !M.debug_compile_units().empty()) {
63     BTF = new BTFDebug(this);
64     Handlers.push_back(HandlerInfo(std::unique_ptr<BTFDebug>(BTF), "emit",
65                                    "Debug Info Emission", "BTF",
66                                    "BTF Emission"));
67   }
68 
69   return false;
70 }
71 
72 void BPFAsmPrinter::printOperand(const MachineInstr *MI, int OpNum,
73                                  raw_ostream &O) {
74   const MachineOperand &MO = MI->getOperand(OpNum);
75 
76   switch (MO.getType()) {
77   case MachineOperand::MO_Register:
78     O << BPFInstPrinter::getRegisterName(MO.getReg());
79     break;
80 
81   case MachineOperand::MO_Immediate:
82     O << MO.getImm();
83     break;
84 
85   case MachineOperand::MO_MachineBasicBlock:
86     O << *MO.getMBB()->getSymbol();
87     break;
88 
89   case MachineOperand::MO_GlobalAddress:
90     O << *getSymbol(MO.getGlobal());
91     break;
92 
93   case MachineOperand::MO_BlockAddress: {
94     MCSymbol *BA = GetBlockAddressSymbol(MO.getBlockAddress());
95     O << BA->getName();
96     break;
97   }
98 
99   case MachineOperand::MO_ExternalSymbol:
100     O << *GetExternalSymbolSymbol(MO.getSymbolName());
101     break;
102 
103   case MachineOperand::MO_JumpTableIndex:
104   case MachineOperand::MO_ConstantPoolIndex:
105   default:
106     llvm_unreachable("<unknown operand type>");
107   }
108 }
109 
110 bool BPFAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
111                                     const char *ExtraCode, raw_ostream &O) {
112   if (ExtraCode && ExtraCode[0])
113     return AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, O);
114 
115   printOperand(MI, OpNo, O);
116   return false;
117 }
118 
119 bool BPFAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
120                                           unsigned OpNum, const char *ExtraCode,
121                                           raw_ostream &O) {
122   assert(OpNum + 1 < MI->getNumOperands() && "Insufficient operands");
123   const MachineOperand &BaseMO = MI->getOperand(OpNum);
124   const MachineOperand &OffsetMO = MI->getOperand(OpNum + 1);
125   assert(BaseMO.isReg() && "Unexpected base pointer for inline asm memory operand.");
126   assert(OffsetMO.isImm() && "Unexpected offset for inline asm memory operand.");
127   int Offset = OffsetMO.getImm();
128 
129   if (ExtraCode)
130     return true; // Unknown modifier.
131 
132   if (Offset < 0)
133     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " - " << -Offset << ")";
134   else
135     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " + " << Offset << ")";
136 
137   return false;
138 }
139 
140 void BPFAsmPrinter::emitInstruction(const MachineInstr *MI) {
141   MCInst TmpInst;
142 
143   if (!BTF || !BTF->InstLower(MI, TmpInst)) {
144     BPFMCInstLower MCInstLowering(OutContext, *this);
145     MCInstLowering.Lower(MI, TmpInst);
146   }
147   EmitToStreamer(*OutStreamer, TmpInst);
148 }
149 
150 // Force static initialization.
151 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeBPFAsmPrinter() {
152   RegisterAsmPrinter<BPFAsmPrinter> X(getTheBPFleTarget());
153   RegisterAsmPrinter<BPFAsmPrinter> Y(getTheBPFbeTarget());
154   RegisterAsmPrinter<BPFAsmPrinter> Z(getTheBPFTarget());
155 }
156