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 "InstPrinter/BPFInstPrinter.h"
20 #include "llvm/CodeGen/AsmPrinter.h"
21 #include "llvm/CodeGen/MachineConstantPool.h"
22 #include "llvm/CodeGen/MachineFunctionPass.h"
23 #include "llvm/CodeGen/MachineInstr.h"
24 #include "llvm/CodeGen/MachineModuleInfo.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/MC/MCInst.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSymbol.h"
29 #include "llvm/Support/TargetRegistry.h"
30 #include "llvm/Support/raw_ostream.h"
31 using namespace llvm;
32 
33 #define DEBUG_TYPE "asm-printer"
34 
35 namespace {
36 class BPFAsmPrinter : public AsmPrinter {
37 public:
38   explicit BPFAsmPrinter(TargetMachine &TM,
39                          std::unique_ptr<MCStreamer> Streamer)
40       : AsmPrinter(TM, std::move(Streamer)) {}
41 
42   StringRef getPassName() const override { return "BPF Assembly Printer"; }
43   void printOperand(const MachineInstr *MI, int OpNum, raw_ostream &O);
44   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
45                        unsigned AsmVariant, const char *ExtraCode,
46                        raw_ostream &O) override;
47   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNum,
48                              unsigned AsmVariant, const char *ExtraCode,
49                              raw_ostream &O) override;
50 
51   void EmitInstruction(const MachineInstr *MI) override;
52 };
53 } // namespace
54 
55 void BPFAsmPrinter::printOperand(const MachineInstr *MI, int OpNum,
56                                  raw_ostream &O) {
57   const MachineOperand &MO = MI->getOperand(OpNum);
58 
59   switch (MO.getType()) {
60   case MachineOperand::MO_Register:
61     O << BPFInstPrinter::getRegisterName(MO.getReg());
62     break;
63 
64   case MachineOperand::MO_Immediate:
65     O << MO.getImm();
66     break;
67 
68   case MachineOperand::MO_MachineBasicBlock:
69     O << *MO.getMBB()->getSymbol();
70     break;
71 
72   case MachineOperand::MO_GlobalAddress:
73     O << *getSymbol(MO.getGlobal());
74     break;
75 
76   case MachineOperand::MO_BlockAddress: {
77     MCSymbol *BA = GetBlockAddressSymbol(MO.getBlockAddress());
78     O << BA->getName();
79     break;
80   }
81 
82   case MachineOperand::MO_ExternalSymbol:
83     O << *GetExternalSymbolSymbol(MO.getSymbolName());
84     break;
85 
86   case MachineOperand::MO_JumpTableIndex:
87   case MachineOperand::MO_ConstantPoolIndex:
88   default:
89     llvm_unreachable("<unknown operand type>");
90   }
91 }
92 
93 bool BPFAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
94                                     unsigned /*AsmVariant*/,
95                                     const char *ExtraCode, raw_ostream &O) {
96   if (ExtraCode && ExtraCode[0])
97     return true; // BPF does not have special modifiers
98 
99   printOperand(MI, OpNo, O);
100   return false;
101 }
102 
103 bool BPFAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
104                                           unsigned OpNum, unsigned AsmVariant,
105                                           const char *ExtraCode,
106                                           raw_ostream &O) {
107   assert(OpNum + 1 < MI->getNumOperands() && "Insufficient operands");
108   const MachineOperand &BaseMO = MI->getOperand(OpNum);
109   const MachineOperand &OffsetMO = MI->getOperand(OpNum + 1);
110   assert(BaseMO.isReg() && "Unexpected base pointer for inline asm memory operand.");
111   assert(OffsetMO.isImm() && "Unexpected offset for inline asm memory operand.");
112   int Offset = OffsetMO.getImm();
113 
114   if (ExtraCode)
115     return true; // Unknown modifier.
116 
117   if (Offset < 0)
118     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " - " << -Offset << ")";
119   else
120     O << "(" << BPFInstPrinter::getRegisterName(BaseMO.getReg()) << " + " << Offset << ")";
121 
122   return false;
123 }
124 
125 void BPFAsmPrinter::EmitInstruction(const MachineInstr *MI) {
126 
127   BPFMCInstLower MCInstLowering(OutContext, *this);
128 
129   MCInst TmpInst;
130   MCInstLowering.Lower(MI, TmpInst);
131   EmitToStreamer(*OutStreamer, TmpInst);
132 }
133 
134 // Force static initialization.
135 extern "C" void LLVMInitializeBPFAsmPrinter() {
136   RegisterAsmPrinter<BPFAsmPrinter> X(getTheBPFleTarget());
137   RegisterAsmPrinter<BPFAsmPrinter> Y(getTheBPFbeTarget());
138   RegisterAsmPrinter<BPFAsmPrinter> Z(getTheBPFTarget());
139 }
140