1 //===- BitstreamReader.cpp - BitstreamReader implementation ---------------===// 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 #include "llvm/Bitcode/BitstreamReader.h" 11 12 using namespace llvm; 13 14 //===----------------------------------------------------------------------===// 15 // BitstreamCursor implementation 16 //===----------------------------------------------------------------------===// 17 18 void BitstreamCursor::freeState() { 19 // Free all the Abbrevs. 20 CurAbbrevs.clear(); 21 22 // Free all the Abbrevs in the block scope. 23 BlockScope.clear(); 24 } 25 26 /// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter 27 /// the block, and return true if the block has an error. 28 bool BitstreamCursor::EnterSubBlock(unsigned BlockID, unsigned *NumWordsP) { 29 // Save the current block's state on BlockScope. 30 BlockScope.push_back(Block(CurCodeSize)); 31 BlockScope.back().PrevAbbrevs.swap(CurAbbrevs); 32 33 // Add the abbrevs specific to this block to the CurAbbrevs list. 34 if (const BitstreamReader::BlockInfo *Info = 35 BitStream->getBlockInfo(BlockID)) { 36 CurAbbrevs.insert(CurAbbrevs.end(), Info->Abbrevs.begin(), 37 Info->Abbrevs.end()); 38 } 39 40 // Get the codesize of this block. 41 CurCodeSize = ReadVBR(bitc::CodeLenWidth); 42 SkipToFourByteBoundary(); 43 unsigned NumWords = Read(bitc::BlockSizeWidth); 44 if (NumWordsP) *NumWordsP = NumWords; 45 46 // Validate that this block is sane. 47 if (CurCodeSize == 0 || AtEndOfStream()) 48 return true; 49 50 return false; 51 } 52 53 static uint64_t readAbbreviatedField(BitstreamCursor &Cursor, 54 const BitCodeAbbrevOp &Op) { 55 assert(!Op.isLiteral() && "Not to be used with literals!"); 56 57 // Decode the value as we are commanded. 58 switch (Op.getEncoding()) { 59 case BitCodeAbbrevOp::Array: 60 case BitCodeAbbrevOp::Blob: 61 llvm_unreachable("Should not reach here"); 62 case BitCodeAbbrevOp::Fixed: 63 return Cursor.Read((unsigned)Op.getEncodingData()); 64 case BitCodeAbbrevOp::VBR: 65 return Cursor.ReadVBR64((unsigned)Op.getEncodingData()); 66 case BitCodeAbbrevOp::Char6: 67 return BitCodeAbbrevOp::DecodeChar6(Cursor.Read(6)); 68 } 69 llvm_unreachable("invalid abbreviation encoding"); 70 } 71 72 static void skipAbbreviatedField(BitstreamCursor &Cursor, 73 const BitCodeAbbrevOp &Op) { 74 assert(!Op.isLiteral() && "Not to be used with literals!"); 75 76 // Decode the value as we are commanded. 77 switch (Op.getEncoding()) { 78 case BitCodeAbbrevOp::Array: 79 case BitCodeAbbrevOp::Blob: 80 llvm_unreachable("Should not reach here"); 81 case BitCodeAbbrevOp::Fixed: 82 Cursor.Read((unsigned)Op.getEncodingData()); 83 break; 84 case BitCodeAbbrevOp::VBR: 85 Cursor.ReadVBR64((unsigned)Op.getEncodingData()); 86 break; 87 case BitCodeAbbrevOp::Char6: 88 Cursor.Read(6); 89 break; 90 } 91 } 92 93 94 95 /// skipRecord - Read the current record and discard it. 96 void BitstreamCursor::skipRecord(unsigned AbbrevID) { 97 // Skip unabbreviated records by reading past their entries. 98 if (AbbrevID == bitc::UNABBREV_RECORD) { 99 unsigned Code = ReadVBR(6); 100 (void)Code; 101 unsigned NumElts = ReadVBR(6); 102 for (unsigned i = 0; i != NumElts; ++i) 103 (void)ReadVBR64(6); 104 return; 105 } 106 107 const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID); 108 109 for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) { 110 const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i); 111 if (Op.isLiteral()) 112 continue; 113 114 if (Op.getEncoding() != BitCodeAbbrevOp::Array && 115 Op.getEncoding() != BitCodeAbbrevOp::Blob) { 116 skipAbbreviatedField(*this, Op); 117 continue; 118 } 119 120 if (Op.getEncoding() == BitCodeAbbrevOp::Array) { 121 // Array case. Read the number of elements as a vbr6. 122 unsigned NumElts = ReadVBR(6); 123 124 // Get the element encoding. 125 assert(i+2 == e && "array op not second to last?"); 126 const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i); 127 128 // Read all the elements. 129 for (; NumElts; --NumElts) 130 skipAbbreviatedField(*this, EltEnc); 131 continue; 132 } 133 134 assert(Op.getEncoding() == BitCodeAbbrevOp::Blob); 135 // Blob case. Read the number of bytes as a vbr6. 136 unsigned NumElts = ReadVBR(6); 137 SkipToFourByteBoundary(); // 32-bit alignment 138 139 // Figure out where the end of this blob will be including tail padding. 140 size_t NewEnd = GetCurrentBitNo()+((NumElts+3)&~3)*8; 141 142 // If this would read off the end of the bitcode file, just set the 143 // record to empty and return. 144 if (!canSkipToPos(NewEnd/8)) { 145 NextChar = BitStream->getBitcodeBytes().getExtent(); 146 break; 147 } 148 149 // Skip over the blob. 150 JumpToBit(NewEnd); 151 } 152 } 153 154 unsigned BitstreamCursor::readRecord(unsigned AbbrevID, 155 SmallVectorImpl<uint64_t> &Vals, 156 StringRef *Blob) { 157 if (AbbrevID == bitc::UNABBREV_RECORD) { 158 unsigned Code = ReadVBR(6); 159 unsigned NumElts = ReadVBR(6); 160 for (unsigned i = 0; i != NumElts; ++i) 161 Vals.push_back(ReadVBR64(6)); 162 return Code; 163 } 164 165 const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID); 166 167 // Read the record code first. 168 assert(Abbv->getNumOperandInfos() != 0 && "no record code in abbreviation?"); 169 const BitCodeAbbrevOp &CodeOp = Abbv->getOperandInfo(0); 170 unsigned Code; 171 if (CodeOp.isLiteral()) 172 Code = CodeOp.getLiteralValue(); 173 else 174 Code = readAbbreviatedField(*this, CodeOp); 175 176 for (unsigned i = 1, e = Abbv->getNumOperandInfos(); i != e; ++i) { 177 const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i); 178 if (Op.isLiteral()) { 179 Vals.push_back(Op.getLiteralValue()); 180 continue; 181 } 182 183 if (Op.getEncoding() != BitCodeAbbrevOp::Array && 184 Op.getEncoding() != BitCodeAbbrevOp::Blob) { 185 Vals.push_back(readAbbreviatedField(*this, Op)); 186 continue; 187 } 188 189 if (Op.getEncoding() == BitCodeAbbrevOp::Array) { 190 // Array case. Read the number of elements as a vbr6. 191 unsigned NumElts = ReadVBR(6); 192 193 // Get the element encoding. 194 assert(i+2 == e && "array op not second to last?"); 195 const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i); 196 197 // Read all the elements. 198 for (; NumElts; --NumElts) 199 Vals.push_back(readAbbreviatedField(*this, EltEnc)); 200 continue; 201 } 202 203 assert(Op.getEncoding() == BitCodeAbbrevOp::Blob); 204 // Blob case. Read the number of bytes as a vbr6. 205 unsigned NumElts = ReadVBR(6); 206 SkipToFourByteBoundary(); // 32-bit alignment 207 208 // Figure out where the end of this blob will be including tail padding. 209 size_t CurBitPos = GetCurrentBitNo(); 210 size_t NewEnd = CurBitPos+((NumElts+3)&~3)*8; 211 212 // If this would read off the end of the bitcode file, just set the 213 // record to empty and return. 214 if (!canSkipToPos(NewEnd/8)) { 215 Vals.append(NumElts, 0); 216 NextChar = BitStream->getBitcodeBytes().getExtent(); 217 break; 218 } 219 220 // Otherwise, inform the streamer that we need these bytes in memory. 221 const char *Ptr = (const char*) 222 BitStream->getBitcodeBytes().getPointer(CurBitPos/8, NumElts); 223 224 // If we can return a reference to the data, do so to avoid copying it. 225 if (Blob) { 226 *Blob = StringRef(Ptr, NumElts); 227 } else { 228 // Otherwise, unpack into Vals with zero extension. 229 for (; NumElts; --NumElts) 230 Vals.push_back((unsigned char)*Ptr++); 231 } 232 // Skip over tail padding. 233 JumpToBit(NewEnd); 234 } 235 236 return Code; 237 } 238 239 240 void BitstreamCursor::ReadAbbrevRecord() { 241 BitCodeAbbrev *Abbv = new BitCodeAbbrev(); 242 unsigned NumOpInfo = ReadVBR(5); 243 for (unsigned i = 0; i != NumOpInfo; ++i) { 244 bool IsLiteral = Read(1) ? true : false; 245 if (IsLiteral) { 246 Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8))); 247 continue; 248 } 249 250 BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3); 251 if (BitCodeAbbrevOp::hasEncodingData(E)) { 252 unsigned Data = ReadVBR64(5); 253 254 // As a special case, handle fixed(0) (i.e., a fixed field with zero bits) 255 // and vbr(0) as a literal zero. This is decoded the same way, and avoids 256 // a slow path in Read() to have to handle reading zero bits. 257 if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) && 258 Data == 0) { 259 Abbv->Add(BitCodeAbbrevOp(0)); 260 continue; 261 } 262 263 Abbv->Add(BitCodeAbbrevOp(E, Data)); 264 } else 265 Abbv->Add(BitCodeAbbrevOp(E)); 266 } 267 CurAbbrevs.push_back(Abbv); 268 } 269 270 bool BitstreamCursor::ReadBlockInfoBlock() { 271 // If this is the second stream to get to the block info block, skip it. 272 if (BitStream->hasBlockInfoRecords()) 273 return SkipBlock(); 274 275 if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true; 276 277 SmallVector<uint64_t, 64> Record; 278 BitstreamReader::BlockInfo *CurBlockInfo = nullptr; 279 280 // Read all the records for this module. 281 while (1) { 282 BitstreamEntry Entry = advanceSkippingSubblocks(AF_DontAutoprocessAbbrevs); 283 284 switch (Entry.Kind) { 285 case llvm::BitstreamEntry::SubBlock: // Handled for us already. 286 case llvm::BitstreamEntry::Error: 287 return true; 288 case llvm::BitstreamEntry::EndBlock: 289 return false; 290 case llvm::BitstreamEntry::Record: 291 // The interesting case. 292 break; 293 } 294 295 // Read abbrev records, associate them with CurBID. 296 if (Entry.ID == bitc::DEFINE_ABBREV) { 297 if (!CurBlockInfo) return true; 298 ReadAbbrevRecord(); 299 300 // ReadAbbrevRecord installs the abbrev in CurAbbrevs. Move it to the 301 // appropriate BlockInfo. 302 CurBlockInfo->Abbrevs.push_back(std::move(CurAbbrevs.back())); 303 CurAbbrevs.pop_back(); 304 continue; 305 } 306 307 // Read a record. 308 Record.clear(); 309 switch (readRecord(Entry.ID, Record)) { 310 default: break; // Default behavior, ignore unknown content. 311 case bitc::BLOCKINFO_CODE_SETBID: 312 if (Record.size() < 1) return true; 313 CurBlockInfo = &BitStream->getOrCreateBlockInfo((unsigned)Record[0]); 314 break; 315 case bitc::BLOCKINFO_CODE_BLOCKNAME: { 316 if (!CurBlockInfo) return true; 317 if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name. 318 std::string Name; 319 for (unsigned i = 0, e = Record.size(); i != e; ++i) 320 Name += (char)Record[i]; 321 CurBlockInfo->Name = Name; 322 break; 323 } 324 case bitc::BLOCKINFO_CODE_SETRECORDNAME: { 325 if (!CurBlockInfo) return true; 326 if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name. 327 std::string Name; 328 for (unsigned i = 1, e = Record.size(); i != e; ++i) 329 Name += (char)Record[i]; 330 CurBlockInfo->RecordNames.push_back(std::make_pair((unsigned)Record[0], 331 Name)); 332 break; 333 } 334 } 335 } 336 } 337 338