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 12using namespace llvm; 13 14//===----------------------------------------------------------------------===// 15// BitstreamCursor implementation 16//===----------------------------------------------------------------------===// 17 18void 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. 28bool 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 53static 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 72static 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. 96void 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 154unsigned 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 if (CodeOp.getEncoding() == BitCodeAbbrevOp::Array || 175 CodeOp.getEncoding() == BitCodeAbbrevOp::Blob) 176 report_fatal_error("Abbreviation starts with an Array or a Blob"); 177 Code = readAbbreviatedField(*this, CodeOp); 178 } 179 180 for (unsigned i = 1, e = Abbv->getNumOperandInfos(); i != e; ++i) { 181 const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i); 182 if (Op.isLiteral()) { 183 Vals.push_back(Op.getLiteralValue()); 184 continue; 185 } 186 187 if (Op.getEncoding() != BitCodeAbbrevOp::Array && 188 Op.getEncoding() != BitCodeAbbrevOp::Blob) { 189 Vals.push_back(readAbbreviatedField(*this, Op)); 190 continue; 191 } 192 193 if (Op.getEncoding() == BitCodeAbbrevOp::Array) { 194 // Array case. Read the number of elements as a vbr6. 195 unsigned NumElts = ReadVBR(6); 196 197 // Get the element encoding. 198 assert(i+2 == e && "array op not second to last?"); 199 const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i); 200 201 // Read all the elements. 202 for (; NumElts; --NumElts) 203 Vals.push_back(readAbbreviatedField(*this, EltEnc)); 204 continue; 205 } 206 207 assert(Op.getEncoding() == BitCodeAbbrevOp::Blob); 208 // Blob case. Read the number of bytes as a vbr6. 209 unsigned NumElts = ReadVBR(6); 210 SkipToFourByteBoundary(); // 32-bit alignment 211 212 // Figure out where the end of this blob will be including tail padding. 213 size_t CurBitPos = GetCurrentBitNo(); 214 size_t NewEnd = CurBitPos+((NumElts+3)&~3)*8; 215 216 // If this would read off the end of the bitcode file, just set the 217 // record to empty and return. 218 if (!canSkipToPos(NewEnd/8)) { 219 Vals.append(NumElts, 0); 220 NextChar = BitStream->getBitcodeBytes().getExtent(); 221 break; 222 } 223 224 // Otherwise, inform the streamer that we need these bytes in memory. 225 const char *Ptr = (const char*) 226 BitStream->getBitcodeBytes().getPointer(CurBitPos/8, NumElts); 227 228 // If we can return a reference to the data, do so to avoid copying it. 229 if (Blob) { 230 *Blob = StringRef(Ptr, NumElts); 231 } else { 232 // Otherwise, unpack into Vals with zero extension. 233 for (; NumElts; --NumElts) 234 Vals.push_back((unsigned char)*Ptr++); 235 } 236 // Skip over tail padding. 237 JumpToBit(NewEnd); 238 } 239 240 return Code; 241} 242 243 244void BitstreamCursor::ReadAbbrevRecord() { 245 BitCodeAbbrev *Abbv = new BitCodeAbbrev(); 246 unsigned NumOpInfo = ReadVBR(5); 247 for (unsigned i = 0; i != NumOpInfo; ++i) { 248 bool IsLiteral = Read(1); 249 if (IsLiteral) { 250 Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8))); 251 continue; 252 } 253 254 BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3); 255 if (BitCodeAbbrevOp::hasEncodingData(E)) { 256 uint64_t Data = ReadVBR64(5); 257 258 // As a special case, handle fixed(0) (i.e., a fixed field with zero bits) 259 // and vbr(0) as a literal zero. This is decoded the same way, and avoids 260 // a slow path in Read() to have to handle reading zero bits. 261 if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) && 262 Data == 0) { 263 Abbv->Add(BitCodeAbbrevOp(0)); 264 continue; 265 } 266 267 Abbv->Add(BitCodeAbbrevOp(E, Data)); 268 } else 269 Abbv->Add(BitCodeAbbrevOp(E)); 270 } 271 CurAbbrevs.push_back(Abbv); 272} 273 274bool BitstreamCursor::ReadBlockInfoBlock() { 275 // If this is the second stream to get to the block info block, skip it. 276 if (BitStream->hasBlockInfoRecords()) 277 return SkipBlock(); 278 279 if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true; 280 281 SmallVector<uint64_t, 64> Record; 282 BitstreamReader::BlockInfo *CurBlockInfo = nullptr; 283 284 // Read all the records for this module. 285 while (1) { 286 BitstreamEntry Entry = advanceSkippingSubblocks(AF_DontAutoprocessAbbrevs); 287 288 switch (Entry.Kind) { 289 case llvm::BitstreamEntry::SubBlock: // Handled for us already. 290 case llvm::BitstreamEntry::Error: 291 return true; 292 case llvm::BitstreamEntry::EndBlock: 293 return false; 294 case llvm::BitstreamEntry::Record: 295 // The interesting case. 296 break; 297 } 298 299 // Read abbrev records, associate them with CurBID. 300 if (Entry.ID == bitc::DEFINE_ABBREV) { 301 if (!CurBlockInfo) return true; 302 ReadAbbrevRecord(); 303 304 // ReadAbbrevRecord installs the abbrev in CurAbbrevs. Move it to the 305 // appropriate BlockInfo. 306 CurBlockInfo->Abbrevs.push_back(std::move(CurAbbrevs.back())); 307 CurAbbrevs.pop_back(); 308 continue; 309 } 310 311 // Read a record. 312 Record.clear(); 313 switch (readRecord(Entry.ID, Record)) { 314 default: break; // Default behavior, ignore unknown content. 315 case bitc::BLOCKINFO_CODE_SETBID: 316 if (Record.size() < 1) return true; 317 CurBlockInfo = &BitStream->getOrCreateBlockInfo((unsigned)Record[0]); 318 break; 319 case bitc::BLOCKINFO_CODE_BLOCKNAME: { 320 if (!CurBlockInfo) return true; 321 if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name. 322 std::string Name; 323 for (unsigned i = 0, e = Record.size(); i != e; ++i) 324 Name += (char)Record[i]; 325 CurBlockInfo->Name = Name; 326 break; 327 } 328 case bitc::BLOCKINFO_CODE_SETRECORDNAME: { 329 if (!CurBlockInfo) return true; 330 if (BitStream->isIgnoringBlockInfoNames()) break; // Ignore name. 331 std::string Name; 332 for (unsigned i = 1, e = Record.size(); i != e; ++i) 333 Name += (char)Record[i]; 334 CurBlockInfo->RecordNames.push_back(std::make_pair((unsigned)Record[0], 335 Name)); 336 break; 337 } 338 } 339 } 340} 341 342