BitstreamReader.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f 
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::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
41void 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.
58bool 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
85void 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
92void 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
113void 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.
136void 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
194unsigned 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  // Read the record code first.
208  assert(Abbv->getNumOperandInfos() != 0 && "no record code in abbreviation?");
209  const BitCodeAbbrevOp &CodeOp = Abbv->getOperandInfo(0);
210  if (CodeOp.isLiteral())
211    readAbbreviatedLiteral(CodeOp, Vals);
212  else
213    readAbbreviatedField(CodeOp, Vals);
214  unsigned Code = (unsigned)Vals.pop_back_val();
215
216  for (unsigned i = 1, e = Abbv->getNumOperandInfos(); i != e; ++i) {
217    const BitCodeAbbrevOp &Op = Abbv->getOperandInfo(i);
218    if (Op.isLiteral()) {
219      readAbbreviatedLiteral(Op, Vals);
220      continue;
221    }
222
223    if (Op.getEncoding() != BitCodeAbbrevOp::Array &&
224        Op.getEncoding() != BitCodeAbbrevOp::Blob) {
225      readAbbreviatedField(Op, Vals);
226      continue;
227    }
228
229    if (Op.getEncoding() == BitCodeAbbrevOp::Array) {
230      // Array case.  Read the number of elements as a vbr6.
231      unsigned NumElts = ReadVBR(6);
232
233      // Get the element encoding.
234      assert(i+2 == e && "array op not second to last?");
235      const BitCodeAbbrevOp &EltEnc = Abbv->getOperandInfo(++i);
236
237      // Read all the elements.
238      for (; NumElts; --NumElts)
239        readAbbreviatedField(EltEnc, Vals);
240      continue;
241    }
242
243    assert(Op.getEncoding() == BitCodeAbbrevOp::Blob);
244    // Blob case.  Read the number of bytes as a vbr6.
245    unsigned NumElts = ReadVBR(6);
246    SkipToFourByteBoundary();  // 32-bit alignment
247
248    // Figure out where the end of this blob will be including tail padding.
249    size_t CurBitPos = GetCurrentBitNo();
250    size_t NewEnd = CurBitPos+((NumElts+3)&~3)*8;
251
252    // If this would read off the end of the bitcode file, just set the
253    // record to empty and return.
254    if (!canSkipToPos(NewEnd/8)) {
255      Vals.append(NumElts, 0);
256      NextChar = BitStream->getBitcodeBytes().getExtent();
257      break;
258    }
259
260    // Otherwise, inform the streamer that we need these bytes in memory.
261    const char *Ptr = (const char*)
262      BitStream->getBitcodeBytes().getPointer(CurBitPos/8, NumElts);
263
264    // If we can return a reference to the data, do so to avoid copying it.
265    if (Blob) {
266      *Blob = StringRef(Ptr, NumElts);
267    } else {
268      // Otherwise, unpack into Vals with zero extension.
269      for (; NumElts; --NumElts)
270        Vals.push_back((unsigned char)*Ptr++);
271    }
272    // Skip over tail padding.
273    JumpToBit(NewEnd);
274  }
275
276  return Code;
277}
278
279
280void BitstreamCursor::ReadAbbrevRecord() {
281  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
282  unsigned NumOpInfo = ReadVBR(5);
283  for (unsigned i = 0; i != NumOpInfo; ++i) {
284    bool IsLiteral = Read(1) ? true : false;
285    if (IsLiteral) {
286      Abbv->Add(BitCodeAbbrevOp(ReadVBR64(8)));
287      continue;
288    }
289
290    BitCodeAbbrevOp::Encoding E = (BitCodeAbbrevOp::Encoding)Read(3);
291    if (BitCodeAbbrevOp::hasEncodingData(E)) {
292      unsigned Data = ReadVBR64(5);
293
294      // As a special case, handle fixed(0) (i.e., a fixed field with zero bits)
295      // and vbr(0) as a literal zero.  This is decoded the same way, and avoids
296      // a slow path in Read() to have to handle reading zero bits.
297      if ((E == BitCodeAbbrevOp::Fixed || E == BitCodeAbbrevOp::VBR) &&
298          Data == 0) {
299        Abbv->Add(BitCodeAbbrevOp(0));
300        continue;
301      }
302
303      Abbv->Add(BitCodeAbbrevOp(E, Data));
304    } else
305      Abbv->Add(BitCodeAbbrevOp(E));
306  }
307  CurAbbrevs.push_back(Abbv);
308}
309
310bool BitstreamCursor::ReadBlockInfoBlock() {
311  // If this is the second stream to get to the block info block, skip it.
312  if (BitStream->hasBlockInfoRecords())
313    return SkipBlock();
314
315  if (EnterSubBlock(bitc::BLOCKINFO_BLOCK_ID)) return true;
316
317  SmallVector<uint64_t, 64> Record;
318  BitstreamReader::BlockInfo *CurBlockInfo = nullptr;
319
320  // Read all the records for this module.
321  while (1) {
322    BitstreamEntry Entry = advanceSkippingSubblocks(AF_DontAutoprocessAbbrevs);
323
324    switch (Entry.Kind) {
325    case llvm::BitstreamEntry::SubBlock: // Handled for us already.
326    case llvm::BitstreamEntry::Error:
327      return true;
328    case llvm::BitstreamEntry::EndBlock:
329      return false;
330    case llvm::BitstreamEntry::Record:
331      // The interesting case.
332      break;
333    }
334
335    // Read abbrev records, associate them with CurBID.
336    if (Entry.ID == bitc::DEFINE_ABBREV) {
337      if (!CurBlockInfo) return true;
338      ReadAbbrevRecord();
339
340      // ReadAbbrevRecord installs the abbrev in CurAbbrevs.  Move it to the
341      // appropriate BlockInfo.
342      BitCodeAbbrev *Abbv = CurAbbrevs.back();
343      CurAbbrevs.pop_back();
344      CurBlockInfo->Abbrevs.push_back(Abbv);
345      continue;
346    }
347
348    // Read a record.
349    Record.clear();
350    switch (readRecord(Entry.ID, Record)) {
351      default: break;  // Default behavior, ignore unknown content.
352      case bitc::BLOCKINFO_CODE_SETBID:
353        if (Record.size() < 1) return true;
354        CurBlockInfo = &BitStream->getOrCreateBlockInfo((unsigned)Record[0]);
355        break;
356      case bitc::BLOCKINFO_CODE_BLOCKNAME: {
357        if (!CurBlockInfo) return true;
358        if (BitStream->isIgnoringBlockInfoNames()) break;  // Ignore name.
359        std::string Name;
360        for (unsigned i = 0, e = Record.size(); i != e; ++i)
361          Name += (char)Record[i];
362        CurBlockInfo->Name = Name;
363        break;
364      }
365      case bitc::BLOCKINFO_CODE_SETRECORDNAME: {
366        if (!CurBlockInfo) return true;
367        if (BitStream->isIgnoringBlockInfoNames()) break;  // Ignore name.
368        std::string Name;
369        for (unsigned i = 1, e = Record.size(); i != e; ++i)
370          Name += (char)Record[i];
371        CurBlockInfo->RecordNames.push_back(std::make_pair((unsigned)Record[0],
372                                                           Name));
373        break;
374      }
375    }
376  }
377}
378
379