BPFMCCodeEmitter.cpp revision 288943 
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  bool IsLittleEndian;
34
35public:
36  BPFMCCodeEmitter(const MCRegisterInfo &mri, bool IsLittleEndian)
37    : MRI(mri), IsLittleEndian(IsLittleEndian) {}
38
39  ~BPFMCCodeEmitter() {}
40
41  // getBinaryCodeForInstr - TableGen'erated function for getting the
42  // binary encoding for an instruction.
43  uint64_t getBinaryCodeForInstr(const MCInst &MI,
44                                 SmallVectorImpl<MCFixup> &Fixups,
45                                 const MCSubtargetInfo &STI) const;
46
47  // getMachineOpValue - Return binary encoding of operand. If the machin
48  // operand requires relocation, record the relocation and return zero.
49  unsigned getMachineOpValue(const MCInst &MI, const MCOperand &MO,
50                             SmallVectorImpl<MCFixup> &Fixups,
51                             const MCSubtargetInfo &STI) const;
52
53  uint64_t getMemoryOpValue(const MCInst &MI, unsigned Op,
54                            SmallVectorImpl<MCFixup> &Fixups,
55                            const MCSubtargetInfo &STI) const;
56
57  void encodeInstruction(const MCInst &MI, raw_ostream &OS,
58                         SmallVectorImpl<MCFixup> &Fixups,
59                         const MCSubtargetInfo &STI) const override;
60};
61}
62
63MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII,
64                                            const MCRegisterInfo &MRI,
65                                            MCContext &Ctx) {
66  return new BPFMCCodeEmitter(MRI, true);
67}
68
69MCCodeEmitter *llvm::createBPFbeMCCodeEmitter(const MCInstrInfo &MCII,
70                                              const MCRegisterInfo &MRI,
71                                              MCContext &Ctx) {
72  return new BPFMCCodeEmitter(MRI, false);
73}
74
75unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI,
76                                             const MCOperand &MO,
77                                             SmallVectorImpl<MCFixup> &Fixups,
78                                             const MCSubtargetInfo &STI) const {
79  if (MO.isReg())
80    return MRI.getEncodingValue(MO.getReg());
81  if (MO.isImm())
82    return static_cast<unsigned>(MO.getImm());
83
84  assert(MO.isExpr());
85
86  const MCExpr *Expr = MO.getExpr();
87
88  assert(Expr->getKind() == MCExpr::SymbolRef);
89
90  if (MI.getOpcode() == BPF::JAL)
91    // func call name
92    Fixups.push_back(MCFixup::create(0, Expr, FK_SecRel_4));
93  else if (MI.getOpcode() == BPF::LD_imm64)
94    Fixups.push_back(MCFixup::create(0, Expr, FK_SecRel_8));
95  else
96    // bb label
97    Fixups.push_back(MCFixup::create(0, Expr, FK_PCRel_2));
98
99  return 0;
100}
101
102static uint8_t SwapBits(uint8_t Val)
103{
104  return (Val & 0x0F) << 4 | (Val & 0xF0) >> 4;
105}
106
107void BPFMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
108                                         SmallVectorImpl<MCFixup> &Fixups,
109                                         const MCSubtargetInfo &STI) const {
110  unsigned Opcode = MI.getOpcode();
111  support::endian::Writer<support::little> LE(OS);
112  support::endian::Writer<support::big> BE(OS);
113
114  if (Opcode == BPF::LD_imm64 || Opcode == BPF::LD_pseudo) {
115    uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
116    LE.write<uint8_t>(Value >> 56);
117    if (IsLittleEndian)
118      LE.write<uint8_t>((Value >> 48) & 0xff);
119    else
120      LE.write<uint8_t>(SwapBits((Value >> 48) & 0xff));
121    LE.write<uint16_t>(0);
122    if (IsLittleEndian)
123      LE.write<uint32_t>(Value & 0xffffFFFF);
124    else
125      BE.write<uint32_t>(Value & 0xffffFFFF);
126
127    const MCOperand &MO = MI.getOperand(1);
128    uint64_t Imm = MO.isImm() ? MO.getImm() : 0;
129    LE.write<uint8_t>(0);
130    LE.write<uint8_t>(0);
131    LE.write<uint16_t>(0);
132    if (IsLittleEndian)
133      LE.write<uint32_t>(Imm >> 32);
134    else
135      BE.write<uint32_t>(Imm >> 32);
136  } else {
137    // Get instruction encoding and emit it
138    uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
139    LE.write<uint8_t>(Value >> 56);
140    if (IsLittleEndian) {
141      LE.write<uint8_t>((Value >> 48) & 0xff);
142      LE.write<uint16_t>((Value >> 32) & 0xffff);
143      LE.write<uint32_t>(Value & 0xffffFFFF);
144    } else {
145      LE.write<uint8_t>(SwapBits((Value >> 48) & 0xff));
146      BE.write<uint16_t>((Value >> 32) & 0xffff);
147      BE.write<uint32_t>(Value & 0xffffFFFF);
148    }
149  }
150}
151
152// Encode BPF Memory Operand
153uint64_t BPFMCCodeEmitter::getMemoryOpValue(const MCInst &MI, unsigned Op,
154                                            SmallVectorImpl<MCFixup> &Fixups,
155                                            const MCSubtargetInfo &STI) const {
156  uint64_t Encoding;
157  const MCOperand Op1 = MI.getOperand(1);
158  assert(Op1.isReg() && "First operand is not register.");
159  Encoding = MRI.getEncodingValue(Op1.getReg());
160  Encoding <<= 16;
161  MCOperand Op2 = MI.getOperand(2);
162  assert(Op2.isImm() && "Second operand is not immediate.");
163  Encoding |= Op2.getImm() & 0xffff;
164  return Encoding;
165}
166
167#include "BPFGenMCCodeEmitter.inc"
168