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::operator=(const BitstreamCursor &RHS) { 19 freeState(); 20 21 BitStream = RHS.BitStream; 22 NextChar = RHS.NextChar; 23 CurWord = RHS.CurWord; 24 BitsInCurWord = RHS.BitsInCurWord; 25 CurCodeSize = RHS.CurCodeSize; 26 27 // Copy abbreviations, and bump ref counts. 28 CurAbbrevs = RHS.CurAbbrevs; 29 for (size_t i = 0, e = CurAbbrevs.size(); i != e; ++i) 30 CurAbbrevs[i]->addRef(); 31 32 // Copy block scope and bump ref counts. 33 BlockScope = RHS.BlockScope; 34 for (size_t S = 0, e = BlockScope.size(); S != e; ++S) { 35 std::vector<BitCodeAbbrev*> &Abbrevs = BlockScope[S].PrevAbbrevs; 36 for (size_t i = 0, e = Abbrevs.size(); i != e; ++i) 37 Abbrevs[i]->addRef(); 38 } 39 } 40 41 void BitstreamCursor::freeState() { 42 // Free all the Abbrevs. 43 for (size_t i = 0, e = CurAbbrevs.size(); i != e; ++i) 44 CurAbbrevs[i]->dropRef(); 45 CurAbbrevs.clear(); 46 47 // Free all the Abbrevs in the block scope. 48 for (size_t S = 0, e = BlockScope.size(); S != e; ++S) { 49 std::vector<BitCodeAbbrev*> &Abbrevs = BlockScope[S].PrevAbbrevs; 50 for (size_t i = 0, e = Abbrevs.size(); i != e; ++i) 51 Abbrevs[i]->dropRef(); 52 } 53 BlockScope.clear(); 54 } 55 56 /// EnterSubBlock - Having read the ENTER_SUBBLOCK abbrevid, enter 57 /// the block, and return true if the block has an error. 58 bool BitstreamCursor::EnterSubBlock(unsigned BlockID, unsigned *NumWordsP) { 59 // Save the current block's state on BlockScope. 60 BlockScope.push_back(Block(CurCodeSize)); 61 BlockScope.back().PrevAbbrevs.swap(CurAbbrevs); 62 63 // Add the abbrevs specific to this block to the CurAbbrevs list. 64 if (const BitstreamReader::BlockInfo *Info = 65 BitStream->getBlockInfo(BlockID)) { 66 for (size_t i = 0, e = Info->Abbrevs.size(); i != e; ++i) { 67 CurAbbrevs.push_back(Info->Abbrevs[i]); 68 CurAbbrevs.back()->addRef(); 69 } 70 } 71 72 // Get the codesize of this block. 73 CurCodeSize = ReadVBR(bitc::CodeLenWidth); 74 SkipToFourByteBoundary(); 75 unsigned NumWords = Read(bitc::BlockSizeWidth); 76 if (NumWordsP) *NumWordsP = NumWords; 77 78 // Validate that this block is sane. 79 if (CurCodeSize == 0 || AtEndOfStream()) 80 return true; 81 82 return false; 83 } 84 85 void BitstreamCursor::readAbbreviatedLiteral(const BitCodeAbbrevOp &Op, 86 SmallVectorImpl<uint64_t> &Vals) { 87 assert(Op.isLiteral() && "Not a literal"); 88 // If the abbrev specifies the literal value to use, use it. 89 Vals.push_back(Op.getLiteralValue()); 90 } 91 92 void BitstreamCursor::readAbbreviatedField(const BitCodeAbbrevOp &Op, 93 SmallVectorImpl<uint64_t> &Vals) { 94 assert(!Op.isLiteral() && "Use ReadAbbreviatedLiteral for literals!"); 95 96 // Decode the value as we are commanded. 97 switch (Op.getEncoding()) { 98 case BitCodeAbbrevOp::Array: 99 case BitCodeAbbrevOp::Blob: 100 assert(0 && "Should not reach here"); 101 case BitCodeAbbrevOp::Fixed: 102 Vals.push_back(Read((unsigned)Op.getEncodingData())); 103 break; 104 case BitCodeAbbrevOp::VBR: 105 Vals.push_back(ReadVBR64((unsigned)Op.getEncodingData())); 106 break; 107 case BitCodeAbbrevOp::Char6: 108 Vals.push_back(BitCodeAbbrevOp::DecodeChar6(Read(6))); 109 break; 110 } 111 } 112 113 void BitstreamCursor::skipAbbreviatedField(const BitCodeAbbrevOp &Op) { 114 assert(!Op.isLiteral() && "Use ReadAbbreviatedLiteral for literals!"); 115 116 // Decode the value as we are commanded. 117 switch (Op.getEncoding()) { 118 case BitCodeAbbrevOp::Array: 119 case BitCodeAbbrevOp::Blob: 120 assert(0 && "Should not reach here"); 121 case BitCodeAbbrevOp::Fixed: 122 (void)Read((unsigned)Op.getEncodingData()); 123 break; 124 case BitCodeAbbrevOp::VBR: 125 (void)ReadVBR64((unsigned)Op.getEncodingData()); 126 break; 127 case BitCodeAbbrevOp::Char6: 128 (void)Read(6); 129 break; 130 } 131 } 132 133 134 135 /// skipRecord - Read the current record and discard it. 136 void BitstreamCursor::skipRecord(unsigned AbbrevID) { 137 // Skip unabbreviated records by reading past their entries. 138 if (AbbrevID == bitc::UNABBREV_RECORD) { 139 unsigned Code = ReadVBR(6); 140 (void)Code; 141 unsigned NumElts = ReadVBR(6); 142 for (unsigned i = 0; i != NumElts; ++i) 143 (void)ReadVBR64(6); 144 return; 145 } 146 147 const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID); 148 149 for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) { 150 const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i); 151 if (Op.isLiteral()) 152 continue; 153 154 if (Op.getEncoding() != BitCodeAbbrevOp::Array && 155 Op.getEncoding() != BitCodeAbbrevOp::Blob) { 156 skipAbbreviatedField(Op); 157 continue; 158 } 159 160 if (Op.getEncoding() == BitCodeAbbrevOp::Array) { 161 // Array case. Read the number of elements as a vbr6. 162 unsigned NumElts = ReadVBR(6); 163 164 // Get the element encoding. 165 assert(i+2 == e && "array op not second to last?"); 166 const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i); 167 168 // Read all the elements. 169 for (; NumElts; --NumElts) 170 skipAbbreviatedField(EltEnc); 171 continue; 172 } 173 174 assert(Op.getEncoding() == BitCodeAbbrevOp::Blob); 175 // Blob case. Read the number of bytes as a vbr6. 176 unsigned NumElts = ReadVBR(6); 177 SkipToFourByteBoundary(); // 32-bit alignment 178 179 // Figure out where the end of this blob will be including tail padding. 180 size_t NewEnd = GetCurrentBitNo()+((NumElts+3)&~3)*8; 181 182 // If this would read off the end of the bitcode file, just set the 183 // record to empty and return. 184 if (!canSkipToPos(NewEnd/8)) { 185 NextChar = BitStream->getBitcodeBytes().getExtent(); 186 break; 187 } 188 189 // Skip over the blob. 190 JumpToBit(NewEnd); 191 } 192 } 193 194 unsigned BitstreamCursor::readRecord(unsigned AbbrevID, 195 SmallVectorImpl<uint64_t> &Vals, 196 StringRef *Blob) { 197 if (AbbrevID == bitc::UNABBREV_RECORD) { 198 unsigned Code = ReadVBR(6); 199 unsigned NumElts = ReadVBR(6); 200 for (unsigned i = 0; i != NumElts; ++i) 201 Vals.push_back(ReadVBR64(6)); 202 return Code; 203 } 204 205 const BitCodeAbbrev *Abbv = getAbbrev(AbbrevID); 206 207 for (unsigned i = 0, e = Abbv->getNumOperandInfos(); i != e; ++i) { 208 const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i); 209 if (Op.isLiteral()) { 210 readAbbreviatedLiteral(Op, Vals); 211 continue; 212 } 213 214 if (Op.getEncoding() != BitCodeAbbrevOp::Array && 215 Op.getEncoding() != BitCodeAbbrevOp::Blob) { 216 readAbbreviatedField(Op, Vals); 217 continue; 218 } 219 220 if (Op.getEncoding() == BitCodeAbbrevOp::Array) { 221 // Array case. Read the number of elements as a vbr6. 222 unsigned NumElts = ReadVBR(6); 223 224 // Get the element encoding. 225 assert(i+2 == e && "array op not second to last?"); 226 const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i); 227 228 // Read all the elements. 229 for (; NumElts; --NumElts) 230 readAbbreviatedField(EltEnc, Vals); 231 continue; 232 } 233 234 assert(Op.getEncoding() == BitCodeAbbrevOp::Blob); 235 // Blob case. Read the number of bytes as a vbr6. 236 unsigned NumElts = ReadVBR(6); 237 SkipToFourByteBoundary(); // 32-bit alignment 238 239 // Figure out where the end of this blob will be including tail padding. 240 size_t CurBitPos = GetCurrentBitNo(); 241 size_t NewEnd = CurBitPos+((NumElts+3)&~3)*8; 242 243 // If this would read off the end of the bitcode file, just set the 244 // record to empty and return. 245 if (!canSkipToPos(NewEnd/8)) { 246 Vals.append(NumElts, 0); 247 NextChar = BitStream->getBitcodeBytes().getExtent(); 248 break; 249 } 250 251 // Otherwise, inform the streamer that we need these bytes in memory. 252 const char *Ptr = (const char*) 253 BitStream->getBitcodeBytes().getPointer(CurBitPos/8, NumElts); 254 255 // If we can return a reference to the data, do so to avoid copying it. 256 if (Blob) { 257 *Blob = StringRef(Ptr, NumElts); 258 } else { 259 // Otherwise, unpack into Vals with zero extension. 260 for (; NumElts; --NumElts) 261 Vals.push_back((unsigned char)*Ptr++); 262 } 263 // Skip over tail padding. 264 JumpToBit(NewEnd); 265 } 266 267 unsigned Code = (unsigned)Vals[0]; 268 Vals.erase(Vals.begin()); 269 return Code; 270 } 271 272 273 void BitstreamCursor::ReadAbbrevRecord() { 274 BitCodeAbbrev *Abbv = new BitCodeAbbrev(); 275 unsigned NumOpInfo = ReadVBR(5); 276 for (unsigned i = 0; i != NumOpInfo; ++i) { 277 bool IsLiteral = Read(1) ? true : false; 278 if (IsLiteral) { 279 Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8))); 280 continue; 281 } 282 283 BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3); 284 if (BitCodeAbbrevOp::hasEncodingData(E)) { 285 unsigned Data = ReadVBR64(5); 286 287 // As a special case, handle fixed(0) (i.e., a fixed field with zero bits) 288 // and vbr(0) as a literal zero. This is decoded the same way, and avoids 289 // a slow path in Read() to have to handle reading zero bits. 290 if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) && 291 Data == 0) { 292 Abbv->Add(BitCodeAbbrevOp(0)); 293 continue; 294 } 295 296 Abbv->Add(BitCodeAbbrevOp(E, Data)); 297 } else 298 Abbv->Add(BitCodeAbbrevOp(E)); 299 } 300 CurAbbrevs.push_back(Abbv); 301 } 302 303 bool BitstreamCursor::ReadBlockInfoBlock() { 304 // If this is the second stream to get to the block info block, skip it. 305 if (BitStream->hasBlockInfoRecords()) 306 return SkipBlock(); 307 308 if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true; 309 310 SmallVector<uint64_t, 64> Record; 311 BitstreamReader::BlockInfo *CurBlockInfo = 0; 312 313 // Read all the records for this module. 314 while (1) { 315 BitstreamEntry Entry = advanceSkippingSubblocks(AF_DontAutoprocessAbbrevs); 316 317 switch (Entry.Kind) { 318 case llvm::BitstreamEntry::SubBlock: // Handled for us already. 319 case llvm::BitstreamEntry::Error: 320 return true; 321 case llvm::BitstreamEntry::EndBlock: 322 return false; 323 case llvm::BitstreamEntry::Record: 324 // The interesting case. 325 break; 326 } 327 328 // Read abbrev records, associate them with CurBID. 329 if (Entry.ID == bitc::DEFINE_ABBREV) { 330 if (!CurBlockInfo) return true; 331 ReadAbbrevRecord(); 332 333 // ReadAbbrevRecord installs the abbrev in CurAbbrevs. Move it to the 334 // appropriate BlockInfo. 335 BitCodeAbbrev *Abbv = CurAbbrevs.back(); 336 CurAbbrevs.pop_back(); 337 CurBlockInfo->Abbrevs.push_back(Abbv); 338 continue; 339 } 340 341 // Read a record. 342 Record.clear(); 343 switch (readRecord(Entry.ID, Record)) { 344 default: break; // Default behavior, ignore unknown content. 345 case bitc::BLOCKINFO_CODE_SETBID: 346 if (Record.size() < 1) return true; 347 CurBlockInfo = &BitStream->getOrCreateBlockInfo((unsigned)Record[0]); 348 break; 349 case bitc::BLOCKINFO_CODE_BLOCKNAME: { 350 if (!CurBlockInfo) return true; 351 if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name. 352 std::string Name; 353 for (unsigned i = 0, e = Record.size(); i != e; ++i) 354 Name += (char)Record[i]; 355 CurBlockInfo->Name = Name; 356 break; 357 } 358 case bitc::BLOCKINFO_CODE_SETRECORDNAME: { 359 if (!CurBlockInfo) return true; 360 if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name. 361 std::string Name; 362 for (unsigned i = 1, e = Record.size(); i != e; ++i) 363 Name += (char)Record[i]; 364 CurBlockInfo->RecordNames.push_back(std::make_pair((unsigned)Record[0], 365 Name)); 366 break; 367 } 368 } 369 } 370 } 371 372