BitcodeReader.cpp revision 9cd3ccf5065a8a139e458d016c88a8512471598b 
1//===- BitcodeReader.cpp - Internal BitcodeReader implementation ----------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by Chris Lattner and is distributed under
6// the University of Illinois Open Source License.  See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This header defines the BitcodeReader class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Bitcode/ReaderWriter.h"
15#include "BitcodeReader.h"
16#include "llvm/Bitcode/BitstreamReader.h"
17#include "llvm/Constants.h"
18#include "llvm/DerivedTypes.h"
19#include "llvm/Module.h"
20#include "llvm/ADT/SmallString.h"
21#include "llvm/Support/MathExtras.h"
22#include "llvm/Support/MemoryBuffer.h"
23using namespace llvm;
24
25BitcodeReader::~BitcodeReader() {
26  delete Buffer;
27}
28
29
30/// ConvertToString - Convert a string from a record into an std::string, return
31/// true on failure.
32template<typename StrTy>
33static bool ConvertToString(SmallVector<uint64_t, 64> &Record, unsigned Idx,
34                            StrTy &Result) {
35  if (Record.size() < Idx+1 || Record.size() < Record[Idx]+Idx+1)
36    return true;
37
38  for (unsigned i = 0, e = Record[Idx]; i != e; ++i)
39    Result += (char)Record[Idx+i+1];
40  return false;
41}
42
43static GlobalValue::LinkageTypes GetDecodedLinkage(unsigned Val) {
44  switch (Val) {
45  default: // Map unknown/new linkages to external
46  case 0: return GlobalValue::ExternalLinkage;
47  case 1: return GlobalValue::WeakLinkage;
48  case 2: return GlobalValue::AppendingLinkage;
49  case 3: return GlobalValue::InternalLinkage;
50  case 4: return GlobalValue::LinkOnceLinkage;
51  case 5: return GlobalValue::DLLImportLinkage;
52  case 6: return GlobalValue::DLLExportLinkage;
53  case 7: return GlobalValue::ExternalWeakLinkage;
54  }
55}
56
57static GlobalValue::VisibilityTypes GetDecodedVisibility(unsigned Val) {
58  switch (Val) {
59  default: // Map unknown visibilities to default.
60  case 0: return GlobalValue::DefaultVisibility;
61  case 1: return GlobalValue::HiddenVisibility;
62  case 2: return GlobalValue::ProtectedVisibility;
63  }
64}
65
66static int GetDecodedCastOpcode(unsigned Val) {
67  switch (Val) {
68  default: return -1;
69  case bitc::CAST_TRUNC   : return Instruction::Trunc;
70  case bitc::CAST_ZEXT    : return Instruction::ZExt;
71  case bitc::CAST_SEXT    : return Instruction::SExt;
72  case bitc::CAST_FPTOUI  : return Instruction::FPToUI;
73  case bitc::CAST_FPTOSI  : return Instruction::FPToSI;
74  case bitc::CAST_UITOFP  : return Instruction::UIToFP;
75  case bitc::CAST_SITOFP  : return Instruction::SIToFP;
76  case bitc::CAST_FPTRUNC : return Instruction::FPTrunc;
77  case bitc::CAST_FPEXT   : return Instruction::FPExt;
78  case bitc::CAST_PTRTOINT: return Instruction::PtrToInt;
79  case bitc::CAST_INTTOPTR: return Instruction::IntToPtr;
80  case bitc::CAST_BITCAST : return Instruction::BitCast;
81  }
82}
83static int GetDecodedBinaryOpcode(unsigned Val, const Type *Ty) {
84  switch (Val) {
85  default: return -1;
86  case bitc::BINOP_ADD:  return Instruction::Add;
87  case bitc::BINOP_SUB:  return Instruction::Sub;
88  case bitc::BINOP_MUL:  return Instruction::Mul;
89  case bitc::BINOP_UDIV: return Instruction::UDiv;
90  case bitc::BINOP_SDIV:
91    return Ty->isFPOrFPVector() ? Instruction::FDiv : Instruction::SDiv;
92  case bitc::BINOP_UREM: return Instruction::URem;
93  case bitc::BINOP_SREM:
94    return Ty->isFPOrFPVector() ? Instruction::FRem : Instruction::SRem;
95  case bitc::BINOP_SHL:  return Instruction::Shl;
96  case bitc::BINOP_LSHR: return Instruction::LShr;
97  case bitc::BINOP_ASHR: return Instruction::AShr;
98  case bitc::BINOP_AND:  return Instruction::And;
99  case bitc::BINOP_OR:   return Instruction::Or;
100  case bitc::BINOP_XOR:  return Instruction::Xor;
101  }
102}
103
104
105namespace {
106  /// @brief A class for maintaining the slot number definition
107  /// as a placeholder for the actual definition for forward constants defs.
108  class ConstantPlaceHolder : public ConstantExpr {
109    ConstantPlaceHolder();                       // DO NOT IMPLEMENT
110    void operator=(const ConstantPlaceHolder &); // DO NOT IMPLEMENT
111  public:
112    Use Op;
113    ConstantPlaceHolder(const Type *Ty)
114      : ConstantExpr(Ty, Instruction::UserOp1, &Op, 1),
115        Op(UndefValue::get(Type::Int32Ty), this) {
116    }
117  };
118}
119
120Constant *BitcodeReaderValueList::getConstantFwdRef(unsigned Idx,
121                                                    const Type *Ty) {
122  if (Idx >= size()) {
123    // Insert a bunch of null values.
124    Uses.resize(Idx+1);
125    OperandList = &Uses[0];
126    NumOperands = Idx+1;
127  }
128
129  if (Uses[Idx]) {
130    assert(Ty == getOperand(Idx)->getType() &&
131           "Type mismatch in constant table!");
132    return cast<Constant>(getOperand(Idx));
133  }
134
135  // Create and return a placeholder, which will later be RAUW'd.
136  Constant *C = new ConstantPlaceHolder(Ty);
137  Uses[Idx].init(C, this);
138  return C;
139}
140
141
142const Type *BitcodeReader::getTypeByID(unsigned ID, bool isTypeTable) {
143  // If the TypeID is in range, return it.
144  if (ID < TypeList.size())
145    return TypeList[ID].get();
146  if (!isTypeTable) return 0;
147
148  // The type table allows forward references.  Push as many Opaque types as
149  // needed to get up to ID.
150  while (TypeList.size() <= ID)
151    TypeList.push_back(OpaqueType::get());
152  return TypeList.back().get();
153}
154
155
156bool BitcodeReader::ParseTypeTable(BitstreamReader &Stream) {
157  if (Stream.EnterSubBlock())
158    return Error("Malformed block record");
159
160  if (!TypeList.empty())
161    return Error("Multiple TYPE_BLOCKs found!");
162
163  SmallVector<uint64_t, 64> Record;
164  unsigned NumRecords = 0;
165
166  // Read all the records for this type table.
167  while (1) {
168    unsigned Code = Stream.ReadCode();
169    if (Code == bitc::END_BLOCK) {
170      if (NumRecords != TypeList.size())
171        return Error("Invalid type forward reference in TYPE_BLOCK");
172      if (Stream.ReadBlockEnd())
173        return Error("Error at end of type table block");
174      return false;
175    }
176
177    if (Code == bitc::ENTER_SUBBLOCK) {
178      // No known subblocks, always skip them.
179      Stream.ReadSubBlockID();
180      if (Stream.SkipBlock())
181        return Error("Malformed block record");
182      continue;
183    }
184
185    if (Code == bitc::DEFINE_ABBREV) {
186      Stream.ReadAbbrevRecord();
187      continue;
188    }
189
190    // Read a record.
191    Record.clear();
192    const Type *ResultTy = 0;
193    switch (Stream.ReadRecord(Code, Record)) {
194    default:  // Default behavior: unknown type.
195      ResultTy = 0;
196      break;
197    case bitc::TYPE_CODE_NUMENTRY: // TYPE_CODE_NUMENTRY: [numentries]
198      // TYPE_CODE_NUMENTRY contains a count of the number of types in the
199      // type list.  This allows us to reserve space.
200      if (Record.size() < 1)
201        return Error("Invalid TYPE_CODE_NUMENTRY record");
202      TypeList.reserve(Record[0]);
203      continue;
204    case bitc::TYPE_CODE_META:      // TYPE_CODE_META: [metacode]...
205      // No metadata supported yet.
206      if (Record.size() < 1)
207        return Error("Invalid TYPE_CODE_META record");
208      continue;
209
210    case bitc::TYPE_CODE_VOID:      // VOID
211      ResultTy = Type::VoidTy;
212      break;
213    case bitc::TYPE_CODE_FLOAT:     // FLOAT
214      ResultTy = Type::FloatTy;
215      break;
216    case bitc::TYPE_CODE_DOUBLE:    // DOUBLE
217      ResultTy = Type::DoubleTy;
218      break;
219    case bitc::TYPE_CODE_LABEL:     // LABEL
220      ResultTy = Type::LabelTy;
221      break;
222    case bitc::TYPE_CODE_OPAQUE:    // OPAQUE
223      ResultTy = 0;
224      break;
225    case bitc::TYPE_CODE_INTEGER:   // INTEGER: [width]
226      if (Record.size() < 1)
227        return Error("Invalid Integer type record");
228
229      ResultTy = IntegerType::get(Record[0]);
230      break;
231    case bitc::TYPE_CODE_POINTER:   // POINTER: [pointee type]
232      if (Record.size() < 1)
233        return Error("Invalid POINTER type record");
234      ResultTy = PointerType::get(getTypeByID(Record[0], true));
235      break;
236    case bitc::TYPE_CODE_FUNCTION: {
237      // FUNCTION: [vararg, retty, #pararms, paramty N]
238      if (Record.size() < 3 || Record.size() < Record[2]+3)
239        return Error("Invalid FUNCTION type record");
240      std::vector<const Type*> ArgTys;
241      for (unsigned i = 0, e = Record[2]; i != e; ++i)
242        ArgTys.push_back(getTypeByID(Record[3+i], true));
243
244      // FIXME: PARAM TYS.
245      ResultTy = FunctionType::get(getTypeByID(Record[1], true), ArgTys,
246                                   Record[0]);
247      break;
248    }
249    case bitc::TYPE_CODE_STRUCT: {  // STRUCT: [ispacked, #elts, eltty x N]
250      if (Record.size() < 2 || Record.size() < Record[1]+2)
251        return Error("Invalid STRUCT type record");
252      std::vector<const Type*> EltTys;
253      for (unsigned i = 0, e = Record[1]; i != e; ++i)
254        EltTys.push_back(getTypeByID(Record[2+i], true));
255      ResultTy = StructType::get(EltTys, Record[0]);
256      break;
257    }
258    case bitc::TYPE_CODE_ARRAY:     // ARRAY: [numelts, eltty]
259      if (Record.size() < 2)
260        return Error("Invalid ARRAY type record");
261      ResultTy = ArrayType::get(getTypeByID(Record[1], true), Record[0]);
262      break;
263    case bitc::TYPE_CODE_VECTOR:    // VECTOR: [numelts, eltty]
264      if (Record.size() < 2)
265        return Error("Invalid VECTOR type record");
266      ResultTy = VectorType::get(getTypeByID(Record[1], true), Record[0]);
267      break;
268    }
269
270    if (NumRecords == TypeList.size()) {
271      // If this is a new type slot, just append it.
272      TypeList.push_back(ResultTy ? ResultTy : OpaqueType::get());
273      ++NumRecords;
274    } else if (ResultTy == 0) {
275      // Otherwise, this was forward referenced, so an opaque type was created,
276      // but the result type is actually just an opaque.  Leave the one we
277      // created previously.
278      ++NumRecords;
279    } else {
280      // Otherwise, this was forward referenced, so an opaque type was created.
281      // Resolve the opaque type to the real type now.
282      assert(NumRecords < TypeList.size() && "Typelist imbalance");
283      const OpaqueType *OldTy = cast<OpaqueType>(TypeList[NumRecords++].get());
284
285      // Don't directly push the new type on the Tab. Instead we want to replace
286      // the opaque type we previously inserted with the new concrete value. The
287      // refinement from the abstract (opaque) type to the new type causes all
288      // uses of the abstract type to use the concrete type (NewTy). This will
289      // also cause the opaque type to be deleted.
290      const_cast<OpaqueType*>(OldTy)->refineAbstractTypeTo(ResultTy);
291
292      // This should have replaced the old opaque type with the new type in the
293      // value table... or with a preexisting type that was already in the
294      // system.  Let's just make sure it did.
295      assert(TypeList[NumRecords-1].get() != OldTy &&
296             "refineAbstractType didn't work!");
297    }
298  }
299}
300
301
302bool BitcodeReader::ParseTypeSymbolTable(BitstreamReader &Stream) {
303  if (Stream.EnterSubBlock())
304    return Error("Malformed block record");
305
306  SmallVector<uint64_t, 64> Record;
307
308  // Read all the records for this type table.
309  std::string TypeName;
310  while (1) {
311    unsigned Code = Stream.ReadCode();
312    if (Code == bitc::END_BLOCK) {
313      if (Stream.ReadBlockEnd())
314        return Error("Error at end of type symbol table block");
315      return false;
316    }
317
318    if (Code == bitc::ENTER_SUBBLOCK) {
319      // No known subblocks, always skip them.
320      Stream.ReadSubBlockID();
321      if (Stream.SkipBlock())
322        return Error("Malformed block record");
323      continue;
324    }
325
326    if (Code == bitc::DEFINE_ABBREV) {
327      Stream.ReadAbbrevRecord();
328      continue;
329    }
330
331    // Read a record.
332    Record.clear();
333    switch (Stream.ReadRecord(Code, Record)) {
334    default:  // Default behavior: unknown type.
335      break;
336    case bitc::TST_CODE_ENTRY:    // TST_ENTRY: [typeid, namelen, namechar x N]
337      if (ConvertToString(Record, 1, TypeName))
338        return Error("Invalid TST_ENTRY record");
339      unsigned TypeID = Record[0];
340      if (TypeID >= TypeList.size())
341        return Error("Invalid Type ID in TST_ENTRY record");
342
343      TheModule->addTypeName(TypeName, TypeList[TypeID].get());
344      TypeName.clear();
345      break;
346    }
347  }
348}
349
350bool BitcodeReader::ParseValueSymbolTable(BitstreamReader &Stream) {
351  if (Stream.EnterSubBlock())
352    return Error("Malformed block record");
353
354  SmallVector<uint64_t, 64> Record;
355
356  // Read all the records for this value table.
357  SmallString<128> ValueName;
358  while (1) {
359    unsigned Code = Stream.ReadCode();
360    if (Code == bitc::END_BLOCK) {
361      if (Stream.ReadBlockEnd())
362        return Error("Error at end of value symbol table block");
363      return false;
364    }
365    if (Code == bitc::ENTER_SUBBLOCK) {
366      // No known subblocks, always skip them.
367      Stream.ReadSubBlockID();
368      if (Stream.SkipBlock())
369        return Error("Malformed block record");
370      continue;
371    }
372
373    if (Code == bitc::DEFINE_ABBREV) {
374      Stream.ReadAbbrevRecord();
375      continue;
376    }
377
378    // Read a record.
379    Record.clear();
380    switch (Stream.ReadRecord(Code, Record)) {
381    default:  // Default behavior: unknown type.
382      break;
383    case bitc::TST_CODE_ENTRY:    // VST_ENTRY: [valueid, namelen, namechar x N]
384      if (ConvertToString(Record, 1, ValueName))
385        return Error("Invalid TST_ENTRY record");
386      unsigned ValueID = Record[0];
387      if (ValueID >= ValueList.size())
388        return Error("Invalid Value ID in VST_ENTRY record");
389      Value *V = ValueList[ValueID];
390
391      V->setName(&ValueName[0], ValueName.size());
392      ValueName.clear();
393      break;
394    }
395  }
396}
397
398/// DecodeSignRotatedValue - Decode a signed value stored with the sign bit in
399/// the LSB for dense VBR encoding.
400static uint64_t DecodeSignRotatedValue(uint64_t V) {
401  if ((V & 1) == 0)
402    return V >> 1;
403  if (V != 1)
404    return -(V >> 1);
405  // There is no such thing as -0 with integers.  "-0" really means MININT.
406  return 1ULL << 63;
407}
408
409/// ResolveGlobalAndAliasInits - Resolve all of the initializers for global
410/// values and aliases that we can.
411bool BitcodeReader::ResolveGlobalAndAliasInits() {
412  std::vector<std::pair<GlobalVariable*, unsigned> > GlobalInitWorklist;
413  std::vector<std::pair<GlobalAlias*, unsigned> > AliasInitWorklist;
414
415  GlobalInitWorklist.swap(GlobalInits);
416  AliasInitWorklist.swap(AliasInits);
417
418  while (!GlobalInitWorklist.empty()) {
419    unsigned ValID = GlobalInitWorklist.back().second;
420    if (ValID >= ValueList.size()) {
421      // Not ready to resolve this yet, it requires something later in the file.
422      GlobalInits.push_back(GlobalInitWorklist.back());
423    } else {
424      if (Constant *C = dyn_cast<Constant>(ValueList[ValID]))
425        GlobalInitWorklist.back().first->setInitializer(C);
426      else
427        return Error("Global variable initializer is not a constant!");
428    }
429    GlobalInitWorklist.pop_back();
430  }
431
432  while (!AliasInitWorklist.empty()) {
433    unsigned ValID = AliasInitWorklist.back().second;
434    if (ValID >= ValueList.size()) {
435      AliasInits.push_back(AliasInitWorklist.back());
436    } else {
437      if (Constant *C = dyn_cast<Constant>(ValueList[ValID]))
438        AliasInitWorklist.back().first->setAliasee(C);
439      else
440        return Error("Alias initializer is not a constant!");
441    }
442    AliasInitWorklist.pop_back();
443  }
444  return false;
445}
446
447
448bool BitcodeReader::ParseConstants(BitstreamReader &Stream) {
449  if (Stream.EnterSubBlock())
450    return Error("Malformed block record");
451
452  SmallVector<uint64_t, 64> Record;
453
454  // Read all the records for this value table.
455  const Type *CurTy = Type::Int32Ty;
456  unsigned NextCstNo = ValueList.size();
457  while (1) {
458    unsigned Code = Stream.ReadCode();
459    if (Code == bitc::END_BLOCK) {
460      if (NextCstNo != ValueList.size())
461        return Error("Invalid constant reference!");
462
463      if (Stream.ReadBlockEnd())
464        return Error("Error at end of constants block");
465      return false;
466    }
467
468    if (Code == bitc::ENTER_SUBBLOCK) {
469      // No known subblocks, always skip them.
470      Stream.ReadSubBlockID();
471      if (Stream.SkipBlock())
472        return Error("Malformed block record");
473      continue;
474    }
475
476    if (Code == bitc::DEFINE_ABBREV) {
477      Stream.ReadAbbrevRecord();
478      continue;
479    }
480
481    // Read a record.
482    Record.clear();
483    Value *V = 0;
484    switch (Stream.ReadRecord(Code, Record)) {
485    default:  // Default behavior: unknown constant
486    case bitc::CST_CODE_UNDEF:     // UNDEF
487      V = UndefValue::get(CurTy);
488      break;
489    case bitc::CST_CODE_SETTYPE:   // SETTYPE: [typeid]
490      if (Record.empty())
491        return Error("Malformed CST_SETTYPE record");
492      if (Record[0] >= TypeList.size())
493        return Error("Invalid Type ID in CST_SETTYPE record");
494      CurTy = TypeList[Record[0]];
495      continue;  // Skip the ValueList manipulation.
496    case bitc::CST_CODE_NULL:      // NULL
497      V = Constant::getNullValue(CurTy);
498      break;
499    case bitc::CST_CODE_INTEGER:   // INTEGER: [intval]
500      if (!isa<IntegerType>(CurTy) || Record.empty())
501        return Error("Invalid CST_INTEGER record");
502      V = ConstantInt::get(CurTy, DecodeSignRotatedValue(Record[0]));
503      break;
504    case bitc::CST_CODE_WIDE_INTEGER: {// WIDE_INTEGER: [n, n x intval]
505      if (!isa<IntegerType>(CurTy) || Record.empty() ||
506          Record.size() < Record[0]+1)
507        return Error("Invalid WIDE_INTEGER record");
508
509      unsigned NumWords = Record[0];
510      SmallVector<uint64_t, 8> Words;
511      Words.resize(NumWords);
512      for (unsigned i = 0; i != NumWords; ++i)
513        Words[i] = DecodeSignRotatedValue(Record[i+1]);
514      V = ConstantInt::get(APInt(cast<IntegerType>(CurTy)->getBitWidth(),
515                                 NumWords, &Words[0]));
516      break;
517    }
518    case bitc::CST_CODE_FLOAT:     // FLOAT: [fpval]
519      if (Record.empty())
520        return Error("Invalid FLOAT record");
521      if (CurTy == Type::FloatTy)
522        V = ConstantFP::get(CurTy, BitsToFloat(Record[0]));
523      else if (CurTy == Type::DoubleTy)
524        V = ConstantFP::get(CurTy, BitsToDouble(Record[0]));
525      else
526        V = UndefValue::get(CurTy);
527      break;
528
529    case bitc::CST_CODE_AGGREGATE: {// AGGREGATE: [n, n x value number]
530      if (Record.empty() || Record.size() < Record[0]+1)
531        return Error("Invalid CST_AGGREGATE record");
532
533      unsigned Size = Record[0];
534      std::vector<Constant*> Elts;
535
536      if (const StructType *STy = dyn_cast<StructType>(CurTy)) {
537        for (unsigned i = 0; i != Size; ++i)
538          Elts.push_back(ValueList.getConstantFwdRef(Record[i+1],
539                                                     STy->getElementType(i)));
540        V = ConstantStruct::get(STy, Elts);
541      } else if (const ArrayType *ATy = dyn_cast<ArrayType>(CurTy)) {
542        const Type *EltTy = ATy->getElementType();
543        for (unsigned i = 0; i != Size; ++i)
544          Elts.push_back(ValueList.getConstantFwdRef(Record[i+1], EltTy));
545        V = ConstantArray::get(ATy, Elts);
546      } else if (const VectorType *VTy = dyn_cast<VectorType>(CurTy)) {
547        const Type *EltTy = VTy->getElementType();
548        for (unsigned i = 0; i != Size; ++i)
549          Elts.push_back(ValueList.getConstantFwdRef(Record[i+1], EltTy));
550        V = ConstantVector::get(Elts);
551      } else {
552        V = UndefValue::get(CurTy);
553      }
554      break;
555    }
556
557    case bitc::CST_CODE_CE_BINOP: {  // CE_BINOP: [opcode, opval, opval]
558      if (Record.size() < 3) return Error("Invalid CE_BINOP record");
559      int Opc = GetDecodedBinaryOpcode(Record[0], CurTy);
560      if (Opc < 0) {
561        V = UndefValue::get(CurTy);  // Unknown binop.
562      } else {
563        Constant *LHS = ValueList.getConstantFwdRef(Record[1], CurTy);
564        Constant *RHS = ValueList.getConstantFwdRef(Record[2], CurTy);
565        V = ConstantExpr::get(Opc, LHS, RHS);
566      }
567      break;
568    }
569    case bitc::CST_CODE_CE_CAST: {  // CE_CAST: [opcode, opty, opval]
570      if (Record.size() < 3) return Error("Invalid CE_CAST record");
571      int Opc = GetDecodedCastOpcode(Record[0]);
572      if (Opc < 0) {
573        V = UndefValue::get(CurTy);  // Unknown cast.
574      } else {
575        const Type *OpTy = getTypeByID(Record[1]);
576        Constant *Op = ValueList.getConstantFwdRef(Record[2], OpTy);
577        V = ConstantExpr::getCast(Opc, Op, CurTy);
578      }
579      break;
580    }
581    case bitc::CST_CODE_CE_GEP: {  // CE_GEP:        [n x operands]
582      if ((Record.size() & 1) == 0) return Error("Invalid CE_GEP record");
583      SmallVector<Constant*, 16> Elts;
584      for (unsigned i = 1, e = Record.size(); i != e; i += 2) {
585        const Type *ElTy = getTypeByID(Record[i]);
586        if (!ElTy) return Error("Invalid CE_GEP record");
587        Elts.push_back(ValueList.getConstantFwdRef(Record[i+1], ElTy));
588      }
589      V = ConstantExpr::getGetElementPtr(Elts[0], &Elts[1], Elts.size()-1);
590      break;
591    }
592    case bitc::CST_CODE_CE_SELECT:  // CE_SELECT: [opval#, opval#, opval#]
593      if (Record.size() < 3) return Error("Invalid CE_SELECT record");
594      V = ConstantExpr::getSelect(ValueList.getConstantFwdRef(Record[0],
595                                                              Type::Int1Ty),
596                                  ValueList.getConstantFwdRef(Record[1],CurTy),
597                                  ValueList.getConstantFwdRef(Record[2],CurTy));
598      break;
599    case bitc::CST_CODE_CE_EXTRACTELT: { // CE_EXTRACTELT: [opty, opval, opval]
600      if (Record.size() < 3) return Error("Invalid CE_EXTRACTELT record");
601      const VectorType *OpTy =
602        dyn_cast_or_null<VectorType>(getTypeByID(Record[0]));
603      if (OpTy == 0) return Error("Invalid CE_EXTRACTELT record");
604      Constant *Op0 = ValueList.getConstantFwdRef(Record[1], OpTy);
605      Constant *Op1 = ValueList.getConstantFwdRef(Record[2],
606                                                  OpTy->getElementType());
607      V = ConstantExpr::getExtractElement(Op0, Op1);
608      break;
609    }
610    case bitc::CST_CODE_CE_INSERTELT: { // CE_INSERTELT: [opval, opval, opval]
611      const VectorType *OpTy = dyn_cast<VectorType>(CurTy);
612      if (Record.size() < 3 || OpTy == 0)
613        return Error("Invalid CE_INSERTELT record");
614      Constant *Op0 = ValueList.getConstantFwdRef(Record[0], OpTy);
615      Constant *Op1 = ValueList.getConstantFwdRef(Record[1],
616                                                  OpTy->getElementType());
617      Constant *Op2 = ValueList.getConstantFwdRef(Record[2], Type::Int32Ty);
618      V = ConstantExpr::getInsertElement(Op0, Op1, Op2);
619      break;
620    }
621    case bitc::CST_CODE_CE_SHUFFLEVEC: { // CE_SHUFFLEVEC: [opval, opval, opval]
622      const VectorType *OpTy = dyn_cast<VectorType>(CurTy);
623      if (Record.size() < 3 || OpTy == 0)
624        return Error("Invalid CE_INSERTELT record");
625      Constant *Op0 = ValueList.getConstantFwdRef(Record[0], OpTy);
626      Constant *Op1 = ValueList.getConstantFwdRef(Record[1], OpTy);
627      const Type *ShufTy=VectorType::get(Type::Int32Ty, OpTy->getNumElements());
628      Constant *Op2 = ValueList.getConstantFwdRef(Record[2], ShufTy);
629      V = ConstantExpr::getShuffleVector(Op0, Op1, Op2);
630      break;
631    }
632    case bitc::CST_CODE_CE_CMP: {     // CE_CMP: [opty, opval, opval, pred]
633      if (Record.size() < 4) return Error("Invalid CE_CMP record");
634      const Type *OpTy = getTypeByID(Record[0]);
635      if (OpTy == 0) return Error("Invalid CE_CMP record");
636      Constant *Op0 = ValueList.getConstantFwdRef(Record[1], OpTy);
637      Constant *Op1 = ValueList.getConstantFwdRef(Record[2], OpTy);
638
639      if (OpTy->isFloatingPoint())
640        V = ConstantExpr::getFCmp(Record[3], Op0, Op1);
641      else
642        V = ConstantExpr::getICmp(Record[3], Op0, Op1);
643      break;
644    }
645    }
646
647    if (NextCstNo == ValueList.size())
648      ValueList.push_back(V);
649    else if (ValueList[NextCstNo] == 0)
650      ValueList.initVal(NextCstNo, V);
651    else {
652      // If there was a forward reference to this constant,
653      Value *OldV = ValueList[NextCstNo];
654      ValueList.setOperand(NextCstNo, V);
655      OldV->replaceAllUsesWith(V);
656      delete OldV;
657    }
658
659    ++NextCstNo;
660  }
661}
662
663bool BitcodeReader::ParseModule(BitstreamReader &Stream,
664                                const std::string &ModuleID) {
665  // Reject multiple MODULE_BLOCK's in a single bitstream.
666  if (TheModule)
667    return Error("Multiple MODULE_BLOCKs in same stream");
668
669  if (Stream.EnterSubBlock())
670    return Error("Malformed block record");
671
672  // Otherwise, create the module.
673  TheModule = new Module(ModuleID);
674
675  SmallVector<uint64_t, 64> Record;
676  std::vector<std::string> SectionTable;
677
678  // Read all the records for this module.
679  while (!Stream.AtEndOfStream()) {
680    unsigned Code = Stream.ReadCode();
681    if (Code == bitc::END_BLOCK) {
682      ResolveGlobalAndAliasInits();
683      if (!GlobalInits.empty() || !AliasInits.empty())
684        return Error("Malformed global initializer set");
685      if (Stream.ReadBlockEnd())
686        return Error("Error at end of module block");
687      return false;
688    }
689
690    if (Code == bitc::ENTER_SUBBLOCK) {
691      switch (Stream.ReadSubBlockID()) {
692      default:  // Skip unknown content.
693        if (Stream.SkipBlock())
694          return Error("Malformed block record");
695        break;
696      case bitc::TYPE_BLOCK_ID:
697        if (ParseTypeTable(Stream))
698          return true;
699        break;
700      case bitc::TYPE_SYMTAB_BLOCK_ID:
701        if (ParseTypeSymbolTable(Stream))
702          return true;
703        break;
704      case bitc::VALUE_SYMTAB_BLOCK_ID:
705        if (ParseValueSymbolTable(Stream))
706          return true;
707        break;
708      case bitc::CONSTANTS_BLOCK_ID:
709        if (ParseConstants(Stream) || ResolveGlobalAndAliasInits())
710          return true;
711        break;
712      }
713      continue;
714    }
715
716    if (Code == bitc::DEFINE_ABBREV) {
717      Stream.ReadAbbrevRecord();
718      continue;
719    }
720
721    // Read a record.
722    switch (Stream.ReadRecord(Code, Record)) {
723    default: break;  // Default behavior, ignore unknown content.
724    case bitc::MODULE_CODE_VERSION:  // VERSION: [version#]
725      if (Record.size() < 1)
726        return Error("Malformed MODULE_CODE_VERSION");
727      // Only version #0 is supported so far.
728      if (Record[0] != 0)
729        return Error("Unknown bitstream version!");
730      break;
731    case bitc::MODULE_CODE_TRIPLE: {  // TRIPLE: [strlen, strchr x N]
732      std::string S;
733      if (ConvertToString(Record, 0, S))
734        return Error("Invalid MODULE_CODE_TRIPLE record");
735      TheModule->setTargetTriple(S);
736      break;
737    }
738    case bitc::MODULE_CODE_DATALAYOUT: {  // DATALAYOUT: [strlen, strchr x N]
739      std::string S;
740      if (ConvertToString(Record, 0, S))
741        return Error("Invalid MODULE_CODE_DATALAYOUT record");
742      TheModule->setDataLayout(S);
743      break;
744    }
745    case bitc::MODULE_CODE_ASM: {  // ASM: [strlen, strchr x N]
746      std::string S;
747      if (ConvertToString(Record, 0, S))
748        return Error("Invalid MODULE_CODE_ASM record");
749      TheModule->setModuleInlineAsm(S);
750      break;
751    }
752    case bitc::MODULE_CODE_DEPLIB: {  // DEPLIB: [strlen, strchr x N]
753      std::string S;
754      if (ConvertToString(Record, 0, S))
755        return Error("Invalid MODULE_CODE_DEPLIB record");
756      TheModule->addLibrary(S);
757      break;
758    }
759    case bitc::MODULE_CODE_SECTIONNAME: {  // SECTIONNAME: [strlen, strchr x N]
760      std::string S;
761      if (ConvertToString(Record, 0, S))
762        return Error("Invalid MODULE_CODE_SECTIONNAME record");
763      SectionTable.push_back(S);
764      break;
765    }
766    // GLOBALVAR: [type, isconst, initid,
767    //             linkage, alignment, section, visibility, threadlocal]
768    case bitc::MODULE_CODE_GLOBALVAR: {
769      if (Record.size() < 6)
770        return Error("Invalid MODULE_CODE_GLOBALVAR record");
771      const Type *Ty = getTypeByID(Record[0]);
772      if (!isa<PointerType>(Ty))
773        return Error("Global not a pointer type!");
774      Ty = cast<PointerType>(Ty)->getElementType();
775
776      bool isConstant = Record[1];
777      GlobalValue::LinkageTypes Linkage = GetDecodedLinkage(Record[3]);
778      unsigned Alignment = (1 << Record[4]) >> 1;
779      std::string Section;
780      if (Record[5]) {
781        if (Record[5]-1 >= SectionTable.size())
782          return Error("Invalid section ID");
783        Section = SectionTable[Record[5]-1];
784      }
785      GlobalValue::VisibilityTypes Visibility = GlobalValue::DefaultVisibility;
786      if (Record.size() >= 6) Visibility = GetDecodedVisibility(Record[6]);
787      bool isThreadLocal = false;
788      if (Record.size() >= 7) isThreadLocal = Record[7];
789
790      GlobalVariable *NewGV =
791        new GlobalVariable(Ty, isConstant, Linkage, 0, "", TheModule);
792      NewGV->setAlignment(Alignment);
793      if (!Section.empty())
794        NewGV->setSection(Section);
795      NewGV->setVisibility(Visibility);
796      NewGV->setThreadLocal(isThreadLocal);
797
798      ValueList.push_back(NewGV);
799
800      // Remember which value to use for the global initializer.
801      if (unsigned InitID = Record[2])
802        GlobalInits.push_back(std::make_pair(NewGV, InitID-1));
803      break;
804    }
805    // FUNCTION:  [type, callingconv, isproto, linkage, alignment, section,
806    //             visibility]
807    case bitc::MODULE_CODE_FUNCTION: {
808      if (Record.size() < 7)
809        return Error("Invalid MODULE_CODE_FUNCTION record");
810      const Type *Ty = getTypeByID(Record[0]);
811      if (!isa<PointerType>(Ty))
812        return Error("Function not a pointer type!");
813      const FunctionType *FTy =
814        dyn_cast<FunctionType>(cast<PointerType>(Ty)->getElementType());
815      if (!FTy)
816        return Error("Function not a pointer to function type!");
817
818      Function *Func = new Function(FTy, GlobalValue::ExternalLinkage,
819                                    "", TheModule);
820
821      Func->setCallingConv(Record[1]);
822      Func->setLinkage(GetDecodedLinkage(Record[3]));
823      Func->setAlignment((1 << Record[4]) >> 1);
824      if (Record[5]) {
825        if (Record[5]-1 >= SectionTable.size())
826          return Error("Invalid section ID");
827        Func->setSection(SectionTable[Record[5]-1]);
828      }
829      Func->setVisibility(GetDecodedVisibility(Record[6]));
830
831      ValueList.push_back(Func);
832      break;
833    }
834    // ALIAS: [alias type, aliasee val#, linkage]
835    case bitc::MODULE_CODE_ALIAS: {
836      if (Record.size() < 3)
837        return Error("Invalid MODULE_ALIAS record");
838      const Type *Ty = getTypeByID(Record[0]);
839      if (!isa<PointerType>(Ty))
840        return Error("Function not a pointer type!");
841
842      GlobalAlias *NewGA = new GlobalAlias(Ty, GetDecodedLinkage(Record[2]),
843                                           "", 0, TheModule);
844      ValueList.push_back(NewGA);
845      AliasInits.push_back(std::make_pair(NewGA, Record[1]));
846      break;
847    }
848    /// MODULE_CODE_PURGEVALS: [numvals]
849    case bitc::MODULE_CODE_PURGEVALS:
850      // Trim down the value list to the specified size.
851      if (Record.size() < 1 || Record[0] > ValueList.size())
852        return Error("Invalid MODULE_PURGEVALS record");
853      ValueList.shrinkTo(Record[0]);
854      break;
855    }
856    Record.clear();
857  }
858
859  return Error("Premature end of bitstream");
860}
861
862
863bool BitcodeReader::ParseBitcode() {
864  TheModule = 0;
865
866  if (Buffer->getBufferSize() & 3)
867    return Error("Bitcode stream should be a multiple of 4 bytes in length");
868
869  unsigned char *BufPtr = (unsigned char *)Buffer->getBufferStart();
870  BitstreamReader Stream(BufPtr, BufPtr+Buffer->getBufferSize());
871
872  // Sniff for the signature.
873  if (Stream.Read(8) != 'B' ||
874      Stream.Read(8) != 'C' ||
875      Stream.Read(4) != 0x0 ||
876      Stream.Read(4) != 0xC ||
877      Stream.Read(4) != 0xE ||
878      Stream.Read(4) != 0xD)
879    return Error("Invalid bitcode signature");
880
881  // We expect a number of well-defined blocks, though we don't necessarily
882  // need to understand them all.
883  while (!Stream.AtEndOfStream()) {
884    unsigned Code = Stream.ReadCode();
885
886    if (Code != bitc::ENTER_SUBBLOCK)
887      return Error("Invalid record at top-level");
888
889    unsigned BlockID = Stream.ReadSubBlockID();
890
891    // We only know the MODULE subblock ID.
892    if (BlockID == bitc::MODULE_BLOCK_ID) {
893      if (ParseModule(Stream, Buffer->getBufferIdentifier()))
894        return true;
895    } else if (Stream.SkipBlock()) {
896      return Error("Malformed block record");
897    }
898  }
899
900  return false;
901}
902
903//===----------------------------------------------------------------------===//
904// External interface
905//===----------------------------------------------------------------------===//
906
907/// getBitcodeModuleProvider - lazy function-at-a-time loading from a file.
908///
909ModuleProvider *llvm::getBitcodeModuleProvider(MemoryBuffer *Buffer,
910                                               std::string *ErrMsg) {
911  BitcodeReader *R = new BitcodeReader(Buffer);
912  if (R->ParseBitcode()) {
913    if (ErrMsg)
914      *ErrMsg = R->getErrorString();
915
916    // Don't let the BitcodeReader dtor delete 'Buffer'.
917    R->releaseMemoryBuffer();
918    delete R;
919    return 0;
920  }
921  return R;
922}
923
924/// ParseBitcodeFile - Read the specified bitcode file, returning the module.
925/// If an error occurs, return null and fill in *ErrMsg if non-null.
926Module *llvm::ParseBitcodeFile(MemoryBuffer *Buffer, std::string *ErrMsg){
927  BitcodeReader *R;
928  R = static_cast<BitcodeReader*>(getBitcodeModuleProvider(Buffer, ErrMsg));
929  if (!R) return 0;
930
931  // Read the whole module, get a pointer to it, tell ModuleProvider not to
932  // delete it when its dtor is run.
933  Module *M = R->releaseModule(ErrMsg);
934
935  // Don't let the BitcodeReader dtor delete 'Buffer'.
936  R->releaseMemoryBuffer();
937  delete R;
938  return M;
939}
940