1//===-- BPFMCCodeEmitter.cpp - Convert BPF code to machine code -----------===//
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 implements the BPFMCCodeEmitter class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "MCTargetDesc/BPFMCTargetDesc.h"
15#include "llvm/MC/MCCodeEmitter.h"
16#include "llvm/MC/MCFixup.h"
17#include "llvm/MC/MCInst.h"
18#include "llvm/MC/MCInstrInfo.h"
19#include "llvm/MC/MCRegisterInfo.h"
20#include "llvm/MC/MCSubtargetInfo.h"
21#include "llvm/MC/MCSymbol.h"
22#include "llvm/ADT/Statistic.h"
23#include "llvm/Support/raw_ostream.h"
24using namespace llvm;
25
26#define DEBUG_TYPE "mccodeemitter"
27
28namespace {
29class BPFMCCodeEmitter : public MCCodeEmitter {
30  BPFMCCodeEmitter(const BPFMCCodeEmitter &) = delete;
31  void operator=(const BPFMCCodeEmitter &) = delete;
32  const MCRegisterInfo &MRI;
33
34public:
35  BPFMCCodeEmitter(const MCRegisterInfo &mri) : MRI(mri) {}
36
37  ~BPFMCCodeEmitter() {}
38
39  // getBinaryCodeForInstr - TableGen'erated function for getting the
40  // binary encoding for an instruction.
41  uint64_t getBinaryCodeForInstr(const MCInst &MI,
42                                 SmallVectorImpl<MCFixup> &Fixups,
43                                 const MCSubtargetInfo &STI) const;
44
45  // getMachineOpValue - Return binary encoding of operand. If the machin
46  // operand requires relocation, record the relocation and return zero.
47  unsigned getMachineOpValue(const MCInst &MI, const MCOperand &MO,
48                             SmallVectorImpl<MCFixup> &Fixups,
49                             const MCSubtargetInfo &STI) const;
50
51  uint64_t getMemoryOpValue(const MCInst &MI, unsigned Op,
52                            SmallVectorImpl<MCFixup> &Fixups,
53                            const MCSubtargetInfo &STI) const;
54
55  void EncodeInstruction(const MCInst &MI, raw_ostream &OS,
56                         SmallVectorImpl<MCFixup> &Fixups,
57                         const MCSubtargetInfo &STI) const override;
58};
59}
60
61MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII,
62                                            const MCRegisterInfo &MRI,
63                                            MCContext &Ctx) {
64  return new BPFMCCodeEmitter(MRI);
65}
66
67unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI,
68                                             const MCOperand &MO,
69                                             SmallVectorImpl<MCFixup> &Fixups,
70                                             const MCSubtargetInfo &STI) const {
71  if (MO.isReg())
72    return MRI.getEncodingValue(MO.getReg());
73  if (MO.isImm())
74    return static_cast<unsigned>(MO.getImm());
75
76  assert(MO.isExpr());
77
78  const MCExpr *Expr = MO.getExpr();
79
80  assert(Expr->getKind() == MCExpr::SymbolRef);
81
82  if (MI.getOpcode() == BPF::JAL)
83    // func call name
84    Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_4));
85  else if (MI.getOpcode() == BPF::LD_imm64)
86    Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_8));
87  else
88    // bb label
89    Fixups.push_back(MCFixup::Create(0, Expr, FK_PCRel_2));
90
91  return 0;
92}
93
94// Emit one byte through output stream
95void EmitByte(unsigned char C, unsigned &CurByte, raw_ostream &OS) {
96  OS << (char)C;
97  ++CurByte;
98}
99
100// Emit a series of bytes (little endian)
101void EmitLEConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
102                    raw_ostream &OS) {
103  assert(Size <= 8 && "size too big in emit constant");
104
105  for (unsigned i = 0; i != Size; ++i) {
106    EmitByte(Val & 255, CurByte, OS);
107    Val >>= 8;
108  }
109}
110
111// Emit a series of bytes (big endian)
112void EmitBEConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
113                    raw_ostream &OS) {
114  assert(Size <= 8 && "size too big in emit constant");
115
116  for (int i = (Size - 1) * 8; i >= 0; i -= 8)
117    EmitByte((Val >> i) & 255, CurByte, OS);
118}
119
120void BPFMCCodeEmitter::EncodeInstruction(const MCInst &MI, raw_ostream &OS,
121                                         SmallVectorImpl<MCFixup> &Fixups,
122                                         const MCSubtargetInfo &STI) const {
123  unsigned Opcode = MI.getOpcode();
124  // Keep track of the current byte being emitted
125  unsigned CurByte = 0;
126
127  if (Opcode == BPF::LD_imm64 || Opcode == BPF::LD_pseudo) {
128    uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
129    EmitByte(Value >> 56, CurByte, OS);
130    EmitByte(((Value >> 48) & 0xff), CurByte, OS);
131    EmitLEConstant(0, 2, CurByte, OS);
132    EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS);
133
134    const MCOperand &MO = MI.getOperand(1);
135    uint64_t Imm = MO.isImm() ? MO.getImm() : 0;
136    EmitByte(0, CurByte, OS);
137    EmitByte(0, CurByte, OS);
138    EmitLEConstant(0, 2, CurByte, OS);
139    EmitLEConstant(Imm >> 32, 4, CurByte, OS);
140  } else {
141    // Get instruction encoding and emit it
142    uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
143    EmitByte(Value >> 56, CurByte, OS);
144    EmitByte((Value >> 48) & 0xff, CurByte, OS);
145    EmitLEConstant((Value >> 32) & 0xffff, 2, CurByte, OS);
146    EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS);
147  }
148}
149
150// Encode BPF Memory Operand
151uint64_t BPFMCCodeEmitter::getMemoryOpValue(const MCInst &MI, unsigned Op,
152                                            SmallVectorImpl<MCFixup> &Fixups,
153                                            const MCSubtargetInfo &STI) const {
154  uint64_t Encoding;
155  const MCOperand Op1 = MI.getOperand(1);
156  assert(Op1.isReg() && "First operand is not register.");
157  Encoding = MRI.getEncodingValue(Op1.getReg());
158  Encoding <<= 16;
159  MCOperand Op2 = MI.getOperand(2);
160  assert(Op2.isImm() && "Second operand is not immediate.");
161  Encoding |= Op2.getImm() & 0xffff;
162  return Encoding;
163}
164
165#include "BPFGenMCCodeEmitter.inc"
166