1 //===-- RISCVDisassembler.cpp - Disassembler for RISCV --------------------===//
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 implements the RISCVDisassembler class.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "MCTargetDesc/RISCVMCTargetDesc.h"
14 #include "Utils/RISCVBaseInfo.h"
15 #include "llvm/MC/MCContext.h"
16 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
17 #include "llvm/MC/MCFixedLenDisassembler.h"
18 #include "llvm/MC/MCInst.h"
19 #include "llvm/MC/MCRegisterInfo.h"
20 #include "llvm/MC/MCSubtargetInfo.h"
21 #include "llvm/Support/Endian.h"
22 #include "llvm/Support/TargetRegistry.h"
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "riscv-disassembler"
27 
28 typedef MCDisassembler::DecodeStatus DecodeStatus;
29 
30 namespace {
31 class RISCVDisassembler : public MCDisassembler {
32 
33 public:
34   RISCVDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx)
35       : MCDisassembler(STI, Ctx) {}
36 
37   DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size,
38                               ArrayRef<uint8_t> Bytes, uint64_t Address,
39                               raw_ostream &VStream,
40                               raw_ostream &CStream) const override;
41 };
42 } // end anonymous namespace
43 
44 static MCDisassembler *createRISCVDisassembler(const Target &T,
45                                                const MCSubtargetInfo &STI,
46                                                MCContext &Ctx) {
47   return new RISCVDisassembler(STI, Ctx);
48 }
49 
50 extern "C" void LLVMInitializeRISCVDisassembler() {
51   // Register the disassembler for each target.
52   TargetRegistry::RegisterMCDisassembler(getTheRISCV32Target(),
53                                          createRISCVDisassembler);
54   TargetRegistry::RegisterMCDisassembler(getTheRISCV64Target(),
55                                          createRISCVDisassembler);
56 }
57 
58 static const unsigned GPRDecoderTable[] = {
59   RISCV::X0,  RISCV::X1,  RISCV::X2,  RISCV::X3,
60   RISCV::X4,  RISCV::X5,  RISCV::X6,  RISCV::X7,
61   RISCV::X8,  RISCV::X9,  RISCV::X10, RISCV::X11,
62   RISCV::X12, RISCV::X13, RISCV::X14, RISCV::X15,
63   RISCV::X16, RISCV::X17, RISCV::X18, RISCV::X19,
64   RISCV::X20, RISCV::X21, RISCV::X22, RISCV::X23,
65   RISCV::X24, RISCV::X25, RISCV::X26, RISCV::X27,
66   RISCV::X28, RISCV::X29, RISCV::X30, RISCV::X31
67 };
68 
69 static DecodeStatus DecodeGPRRegisterClass(MCInst &Inst, uint64_t RegNo,
70                                            uint64_t Address,
71                                            const void *Decoder) {
72   if (RegNo > sizeof(GPRDecoderTable))
73     return MCDisassembler::Fail;
74 
75   // We must define our own mapping from RegNo to register identifier.
76   // Accessing index RegNo in the register class will work in the case that
77   // registers were added in ascending order, but not in general.
78   unsigned Reg = GPRDecoderTable[RegNo];
79   Inst.addOperand(MCOperand::createReg(Reg));
80   return MCDisassembler::Success;
81 }
82 
83 static const unsigned FPR32DecoderTable[] = {
84   RISCV::F0_32,  RISCV::F1_32,  RISCV::F2_32,  RISCV::F3_32,
85   RISCV::F4_32,  RISCV::F5_32,  RISCV::F6_32,  RISCV::F7_32,
86   RISCV::F8_32,  RISCV::F9_32,  RISCV::F10_32, RISCV::F11_32,
87   RISCV::F12_32, RISCV::F13_32, RISCV::F14_32, RISCV::F15_32,
88   RISCV::F16_32, RISCV::F17_32, RISCV::F18_32, RISCV::F19_32,
89   RISCV::F20_32, RISCV::F21_32, RISCV::F22_32, RISCV::F23_32,
90   RISCV::F24_32, RISCV::F25_32, RISCV::F26_32, RISCV::F27_32,
91   RISCV::F28_32, RISCV::F29_32, RISCV::F30_32, RISCV::F31_32
92 };
93 
94 static DecodeStatus DecodeFPR32RegisterClass(MCInst &Inst, uint64_t RegNo,
95                                              uint64_t Address,
96                                              const void *Decoder) {
97   if (RegNo > sizeof(FPR32DecoderTable))
98     return MCDisassembler::Fail;
99 
100   // We must define our own mapping from RegNo to register identifier.
101   // Accessing index RegNo in the register class will work in the case that
102   // registers were added in ascending order, but not in general.
103   unsigned Reg = FPR32DecoderTable[RegNo];
104   Inst.addOperand(MCOperand::createReg(Reg));
105   return MCDisassembler::Success;
106 }
107 
108 static DecodeStatus DecodeFPR32CRegisterClass(MCInst &Inst, uint64_t RegNo,
109                                               uint64_t Address,
110                                               const void *Decoder) {
111   if (RegNo > 8) {
112     return MCDisassembler::Fail;
113   }
114   unsigned Reg = FPR32DecoderTable[RegNo + 8];
115   Inst.addOperand(MCOperand::createReg(Reg));
116   return MCDisassembler::Success;
117 }
118 
119 static const unsigned FPR64DecoderTable[] = {
120   RISCV::F0_64,  RISCV::F1_64,  RISCV::F2_64,  RISCV::F3_64,
121   RISCV::F4_64,  RISCV::F5_64,  RISCV::F6_64,  RISCV::F7_64,
122   RISCV::F8_64,  RISCV::F9_64,  RISCV::F10_64, RISCV::F11_64,
123   RISCV::F12_64, RISCV::F13_64, RISCV::F14_64, RISCV::F15_64,
124   RISCV::F16_64, RISCV::F17_64, RISCV::F18_64, RISCV::F19_64,
125   RISCV::F20_64, RISCV::F21_64, RISCV::F22_64, RISCV::F23_64,
126   RISCV::F24_64, RISCV::F25_64, RISCV::F26_64, RISCV::F27_64,
127   RISCV::F28_64, RISCV::F29_64, RISCV::F30_64, RISCV::F31_64
128 };
129 
130 static DecodeStatus DecodeFPR64RegisterClass(MCInst &Inst, uint64_t RegNo,
131                                              uint64_t Address,
132                                              const void *Decoder) {
133   if (RegNo > sizeof(FPR64DecoderTable))
134     return MCDisassembler::Fail;
135 
136   // We must define our own mapping from RegNo to register identifier.
137   // Accessing index RegNo in the register class will work in the case that
138   // registers were added in ascending order, but not in general.
139   unsigned Reg = FPR64DecoderTable[RegNo];
140   Inst.addOperand(MCOperand::createReg(Reg));
141   return MCDisassembler::Success;
142 }
143 
144 static DecodeStatus DecodeFPR64CRegisterClass(MCInst &Inst, uint64_t RegNo,
145                                               uint64_t Address,
146                                               const void *Decoder) {
147   if (RegNo > 8) {
148     return MCDisassembler::Fail;
149   }
150   unsigned Reg = FPR64DecoderTable[RegNo + 8];
151   Inst.addOperand(MCOperand::createReg(Reg));
152   return MCDisassembler::Success;
153 }
154 
155 static DecodeStatus DecodeGPRNoX0RegisterClass(MCInst &Inst, uint64_t RegNo,
156                                                uint64_t Address,
157                                                const void *Decoder) {
158   if (RegNo == 0) {
159     return MCDisassembler::Fail;
160   }
161 
162   return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
163 }
164 
165 static DecodeStatus DecodeGPRNoX0X2RegisterClass(MCInst &Inst, uint64_t RegNo,
166                                                  uint64_t Address,
167                                                  const void *Decoder) {
168   if (RegNo == 2) {
169     return MCDisassembler::Fail;
170   }
171 
172   return DecodeGPRNoX0RegisterClass(Inst, RegNo, Address, Decoder);
173 }
174 
175 static DecodeStatus DecodeGPRCRegisterClass(MCInst &Inst, uint64_t RegNo,
176                                             uint64_t Address,
177                                             const void *Decoder) {
178   if (RegNo > 8)
179     return MCDisassembler::Fail;
180 
181   unsigned Reg = GPRDecoderTable[RegNo + 8];
182   Inst.addOperand(MCOperand::createReg(Reg));
183   return MCDisassembler::Success;
184 }
185 
186 // Add implied SP operand for instructions *SP compressed instructions. The SP
187 // operand isn't explicitly encoded in the instruction.
188 static void addImplySP(MCInst &Inst, int64_t Address, const void *Decoder) {
189   if (Inst.getOpcode() == RISCV::C_LWSP || Inst.getOpcode() == RISCV::C_SWSP ||
190       Inst.getOpcode() == RISCV::C_LDSP || Inst.getOpcode() == RISCV::C_SDSP ||
191       Inst.getOpcode() == RISCV::C_FLWSP ||
192       Inst.getOpcode() == RISCV::C_FSWSP ||
193       Inst.getOpcode() == RISCV::C_FLDSP ||
194       Inst.getOpcode() == RISCV::C_FSDSP ||
195       Inst.getOpcode() == RISCV::C_ADDI4SPN) {
196     DecodeGPRRegisterClass(Inst, 2, Address, Decoder);
197   }
198   if (Inst.getOpcode() == RISCV::C_ADDI16SP) {
199     DecodeGPRRegisterClass(Inst, 2, Address, Decoder);
200     DecodeGPRRegisterClass(Inst, 2, Address, Decoder);
201   }
202 }
203 
204 template <unsigned N>
205 static DecodeStatus decodeUImmOperand(MCInst &Inst, uint64_t Imm,
206                                       int64_t Address, const void *Decoder) {
207   assert(isUInt<N>(Imm) && "Invalid immediate");
208   addImplySP(Inst, Address, Decoder);
209   Inst.addOperand(MCOperand::createImm(Imm));
210   return MCDisassembler::Success;
211 }
212 
213 template <unsigned N>
214 static DecodeStatus decodeUImmNonZeroOperand(MCInst &Inst, uint64_t Imm,
215                                              int64_t Address,
216                                              const void *Decoder) {
217   if (Imm == 0)
218     return MCDisassembler::Fail;
219   return decodeUImmOperand<N>(Inst, Imm, Address, Decoder);
220 }
221 
222 template <unsigned N>
223 static DecodeStatus decodeSImmOperand(MCInst &Inst, uint64_t Imm,
224                                       int64_t Address, const void *Decoder) {
225   assert(isUInt<N>(Imm) && "Invalid immediate");
226   addImplySP(Inst, Address, Decoder);
227   // Sign-extend the number in the bottom N bits of Imm
228   Inst.addOperand(MCOperand::createImm(SignExtend64<N>(Imm)));
229   return MCDisassembler::Success;
230 }
231 
232 template <unsigned N>
233 static DecodeStatus decodeSImmNonZeroOperand(MCInst &Inst, uint64_t Imm,
234                                              int64_t Address,
235                                              const void *Decoder) {
236   if (Imm == 0)
237     return MCDisassembler::Fail;
238   return decodeSImmOperand<N>(Inst, Imm, Address, Decoder);
239 }
240 
241 template <unsigned N>
242 static DecodeStatus decodeSImmOperandAndLsl1(MCInst &Inst, uint64_t Imm,
243                                              int64_t Address,
244                                              const void *Decoder) {
245   assert(isUInt<N>(Imm) && "Invalid immediate");
246   // Sign-extend the number in the bottom N bits of Imm after accounting for
247   // the fact that the N bit immediate is stored in N-1 bits (the LSB is
248   // always zero)
249   Inst.addOperand(MCOperand::createImm(SignExtend64<N>(Imm << 1)));
250   return MCDisassembler::Success;
251 }
252 
253 static DecodeStatus decodeCLUIImmOperand(MCInst &Inst, uint64_t Imm,
254                                          int64_t Address,
255                                          const void *Decoder) {
256   assert(isUInt<6>(Imm) && "Invalid immediate");
257   if (Imm > 31) {
258     Imm = (SignExtend64<6>(Imm) & 0xfffff);
259   }
260   Inst.addOperand(MCOperand::createImm(Imm));
261   return MCDisassembler::Success;
262 }
263 
264 static DecodeStatus decodeFRMArg(MCInst &Inst, uint64_t Imm,
265                                  int64_t Address,
266                                  const void *Decoder) {
267   assert(isUInt<3>(Imm) && "Invalid immediate");
268   if (!llvm::RISCVFPRndMode::isValidRoundingMode(Imm))
269     return MCDisassembler::Fail;
270 
271   Inst.addOperand(MCOperand::createImm(Imm));
272   return MCDisassembler::Success;
273 }
274 
275 #include "RISCVGenDisassemblerTables.inc"
276 
277 DecodeStatus RISCVDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
278                                                ArrayRef<uint8_t> Bytes,
279                                                uint64_t Address,
280                                                raw_ostream &OS,
281                                                raw_ostream &CS) const {
282   // TODO: This will need modification when supporting instruction set
283   // extensions with instructions > 32-bits (up to 176 bits wide).
284   uint32_t Insn;
285   DecodeStatus Result;
286 
287   // It's a 32 bit instruction if bit 0 and 1 are 1.
288   if ((Bytes[0] & 0x3) == 0x3) {
289     if (Bytes.size() < 4) {
290       Size = 0;
291       return MCDisassembler::Fail;
292     }
293     Insn = support::endian::read32le(Bytes.data());
294     LLVM_DEBUG(dbgs() << "Trying RISCV32 table :\n");
295     Result = decodeInstruction(DecoderTable32, MI, Insn, Address, this, STI);
296     Size = 4;
297   } else {
298     if (Bytes.size() < 2) {
299       Size = 0;
300       return MCDisassembler::Fail;
301     }
302     Insn = support::endian::read16le(Bytes.data());
303 
304     if (!STI.getFeatureBits()[RISCV::Feature64Bit]) {
305       LLVM_DEBUG(
306           dbgs() << "Trying RISCV32Only_16 table (16-bit Instruction):\n");
307       // Calling the auto-generated decoder function.
308       Result = decodeInstruction(DecoderTableRISCV32Only_16, MI, Insn, Address,
309                                  this, STI);
310       if (Result != MCDisassembler::Fail) {
311         Size = 2;
312         return Result;
313       }
314     }
315 
316     LLVM_DEBUG(dbgs() << "Trying RISCV_C table (16-bit Instruction):\n");
317     // Calling the auto-generated decoder function.
318     Result = decodeInstruction(DecoderTable16, MI, Insn, Address, this, STI);
319     Size = 2;
320   }
321 
322   return Result;
323 }
324