1 //===-- BPFAsmPrinter.cpp - BPF LLVM assembly writer ----------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains a printer that converts from our internal representation
11 // of machine-dependent LLVM code to the BPF assembly language.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "BPF.h"
16 #include "BPFInstrInfo.h"
17 #include "BPFMCInstLower.h"
18 #include "BPFTargetMachine.h"
19 #include "BTFDebug.h"
20 #include "InstPrinter/BPFInstPrinter.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                        unsigned AsmVariant, const char *ExtraCode,
48                        raw_ostream &O) override;
49   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,
50                              unsigned AsmVariant, const char *ExtraCode,
51                              raw_ostream &O) override;
52 
53   void EmitInstruction(const MachineInstr *MI) override;
54 };
55 } // namespace
56 
57 bool BPFAsmPrinter::doInitialization(Module &M) {
58   AsmPrinter::doInitialization(M);
59 
60   if (MAI->doesSupportDebugInformation()) {
61     Handlers.push_back(HandlerInfo(new BTFDebug(this), "emit",
62                                    "Debug Info Emission", "BTF",
63                                    "BTF Emission"));
64   }
65 
66   return false;
67 }
68 
69 void BPFAsmPrinter::printOperand(const MachineInstr *MI, int OpNum,
70                                  raw_ostream &O) {
71   const MachineOperand &MO = MI->getOperand(OpNum);
72 
73   switch (MO.getType()) {
74   case MachineOperand::MO_Register:
75     O << BPFInstPrinter::getRegisterName(MO.getReg());
76     break;
77 
78   case MachineOperand::MO_Immediate:
79     O << MO.getImm();
80     break;
81 
82   case MachineOperand::MO_MachineBasicBlock:
83     O << *MO.getMBB()->getSymbol();
84     break;
85 
86   case MachineOperand::MO_GlobalAddress:
87     O << *getSymbol(MO.getGlobal());
88     break;
89 
90   case MachineOperand::MO_BlockAddress: {
91     MCSymbol *BA = GetBlockAddressSymbol(MO.getBlockAddress());
92     O << BA->getName();
93     break;
94   }
95 
96   case MachineOperand::MO_ExternalSymbol:
97     O << *GetExternalSymbolSymbol(MO.getSymbolName());
98     break;
99 
100   case MachineOperand::MO_JumpTableIndex:
101   case MachineOperand::MO_ConstantPoolIndex:
102   default:
103     llvm_unreachable("<unknown operand type>");
104   }
105 }
106 
107 bool BPFAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
108                                     unsigned /*AsmVariant*/,
109                                     const char *ExtraCode, raw_ostream &O) {
110   if (ExtraCode && ExtraCode[0])
111     return true; // BPF does not have special modifiers
112 
113   printOperand(MI, OpNo, O);
114   return false;
115 }
116 
117 bool BPFAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
118                                           unsigned OpNum, unsigned AsmVariant,
119                                           const char *ExtraCode,
120                                           raw_ostream &O) {
121   assert(OpNum + 1 < MI->getNumOperands() && "Insufficient operands");
122   const MachineOperand &BaseMO = MI->getOperand(OpNum);
123   const MachineOperand &OffsetMO = MI->getOperand(OpNum + 1);
124   assert(BaseMO.isReg() && "Unexpected base pointer for inline asm memory operand.");
125   assert(OffsetMO.isImm() && "Unexpected offset for inline asm memory operand.");
126   int Offset = OffsetMO.getImm();
127 
128   if (ExtraCode)
129     return true; // Unknown modifier.
130 
131   if (Offset < 0)
132     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " - " << -Offset << ")";
133   else
134     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " + " << Offset << ")";
135 
136   return false;
137 }
138 
139 void BPFAsmPrinter::EmitInstruction(const MachineInstr *MI) {
140 
141   BPFMCInstLower MCInstLowering(OutContext, *this);
142 
143   MCInst TmpInst;
144   MCInstLowering.Lower(MI, TmpInst);
145   EmitToStreamer(*OutStreamer, TmpInst);
146 }
147 
148 // Force static initialization.
149 extern "C" void LLVMInitializeBPFAsmPrinter() {
150   RegisterAsmPrinter<BPFAsmPrinter> X(getTheBPFleTarget());
151   RegisterAsmPrinter<BPFAsmPrinter> Y(getTheBPFbeTarget());
152   RegisterAsmPrinter<BPFAsmPrinter> Z(getTheBPFTarget());
153 }
154