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