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  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
273void 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
303bool 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