1 //===--- Bitcode/Writer/BitcodeWriter.cpp - Bitcode Writer ----------------===//
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 // Bitcode writer implementation.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/Bitcode/ReaderWriter.h"
15 #include "ValueEnumerator.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/Bitcode/BitstreamWriter.h"
18 #include "llvm/Bitcode/LLVMBitCodes.h"
19 #include "llvm/IR/Constants.h"
20 #include "llvm/IR/DerivedTypes.h"
21 #include "llvm/IR/InlineAsm.h"
22 #include "llvm/IR/Instructions.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/IR/Operator.h"
25 #include "llvm/IR/ValueSymbolTable.h"
26 #include "llvm/Support/CommandLine.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/MathExtras.h"
29 #include "llvm/Support/Program.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include <cctype>
32 #include <map>
33 using namespace llvm;
34 
35 static cl::opt<bool>
36 EnablePreserveUseListOrdering("enable-bc-uselist-preserve",
37                               cl::desc("Turn on experimental support for "
38                                        "use-list order preservation."),
39                               cl::init(false), cl::Hidden);
40 
41 /// These are manifest constants used by the bitcode writer. They do not need to
42 /// be kept in sync with the reader, but need to be consistent within this file.
43 enum {
44   // VALUE_SYMTAB_BLOCK abbrev id's.
45   VST_ENTRY_8_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
46   VST_ENTRY_7_ABBREV,
47   VST_ENTRY_6_ABBREV,
48   VST_BBENTRY_6_ABBREV,
49 
50   // CONSTANTS_BLOCK abbrev id's.
51   CONSTANTS_SETTYPE_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
52   CONSTANTS_INTEGER_ABBREV,
53   CONSTANTS_CE_CAST_Abbrev,
54   CONSTANTS_NULL_Abbrev,
55 
56   // FUNCTION_BLOCK abbrev id's.
57   FUNCTION_INST_LOAD_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
58   FUNCTION_INST_BINOP_ABBREV,
59   FUNCTION_INST_BINOP_FLAGS_ABBREV,
60   FUNCTION_INST_CAST_ABBREV,
61   FUNCTION_INST_RET_VOID_ABBREV,
62   FUNCTION_INST_RET_VAL_ABBREV,
63   FUNCTION_INST_UNREACHABLE_ABBREV
64 };
65 
66 static unsigned GetEncodedCastOpcode(unsigned Opcode) {
67   switch (Opcode) {
68   default: llvm_unreachable("Unknown cast instruction!");
69   case Instruction::Trunc   : return bitc::CAST_TRUNC;
70   case Instruction::ZExt    : return bitc::CAST_ZEXT;
71   case Instruction::SExt    : return bitc::CAST_SEXT;
72   case Instruction::FPToUI  : return bitc::CAST_FPTOUI;
73   case Instruction::FPToSI  : return bitc::CAST_FPTOSI;
74   case Instruction::UIToFP  : return bitc::CAST_UITOFP;
75   case Instruction::SIToFP  : return bitc::CAST_SITOFP;
76   case Instruction::FPTrunc : return bitc::CAST_FPTRUNC;
77   case Instruction::FPExt   : return bitc::CAST_FPEXT;
78   case Instruction::PtrToInt: return bitc::CAST_PTRTOINT;
79   case Instruction::IntToPtr: return bitc::CAST_INTTOPTR;
80   case Instruction::BitCast : return bitc::CAST_BITCAST;
81   case Instruction::AddrSpaceCast: return bitc::CAST_ADDRSPACECAST;
82   }
83 }
84 
85 static unsigned GetEncodedBinaryOpcode(unsigned Opcode) {
86   switch (Opcode) {
87   default: llvm_unreachable("Unknown binary instruction!");
88   case Instruction::Add:
89   case Instruction::FAdd: return bitc::BINOP_ADD;
90   case Instruction::Sub:
91   case Instruction::FSub: return bitc::BINOP_SUB;
92   case Instruction::Mul:
93   case Instruction::FMul: return bitc::BINOP_MUL;
94   case Instruction::UDiv: return bitc::BINOP_UDIV;
95   case Instruction::FDiv:
96   case Instruction::SDiv: return bitc::BINOP_SDIV;
97   case Instruction::URem: return bitc::BINOP_UREM;
98   case Instruction::FRem:
99   case Instruction::SRem: return bitc::BINOP_SREM;
100   case Instruction::Shl:  return bitc::BINOP_SHL;
101   case Instruction::LShr: return bitc::BINOP_LSHR;
102   case Instruction::AShr: return bitc::BINOP_ASHR;
103   case Instruction::And:  return bitc::BINOP_AND;
104   case Instruction::Or:   return bitc::BINOP_OR;
105   case Instruction::Xor:  return bitc::BINOP_XOR;
106   }
107 }
108 
109 static unsigned GetEncodedRMWOperation(AtomicRMWInst::BinOp Op) {
110   switch (Op) {
111   default: llvm_unreachable("Unknown RMW operation!");
112   case AtomicRMWInst::Xchg: return bitc::RMW_XCHG;
113   case AtomicRMWInst::Add: return bitc::RMW_ADD;
114   case AtomicRMWInst::Sub: return bitc::RMW_SUB;
115   case AtomicRMWInst::And: return bitc::RMW_AND;
116   case AtomicRMWInst::Nand: return bitc::RMW_NAND;
117   case AtomicRMWInst::Or: return bitc::RMW_OR;
118   case AtomicRMWInst::Xor: return bitc::RMW_XOR;
119   case AtomicRMWInst::Max: return bitc::RMW_MAX;
120   case AtomicRMWInst::Min: return bitc::RMW_MIN;
121   case AtomicRMWInst::UMax: return bitc::RMW_UMAX;
122   case AtomicRMWInst::UMin: return bitc::RMW_UMIN;
123   }
124 }
125 
126 static unsigned GetEncodedOrdering(AtomicOrdering Ordering) {
127   switch (Ordering) {
128   case NotAtomic: return bitc::ORDERING_NOTATOMIC;
129   case Unordered: return bitc::ORDERING_UNORDERED;
130   case Monotonic: return bitc::ORDERING_MONOTONIC;
131   case Acquire: return bitc::ORDERING_ACQUIRE;
132   case Release: return bitc::ORDERING_RELEASE;
133   case AcquireRelease: return bitc::ORDERING_ACQREL;
134   case SequentiallyConsistent: return bitc::ORDERING_SEQCST;
135   }
136   llvm_unreachable("Invalid ordering");
137 }
138 
139 static unsigned GetEncodedSynchScope(SynchronizationScope SynchScope) {
140   switch (SynchScope) {
141   case SingleThread: return bitc::SYNCHSCOPE_SINGLETHREAD;
142   case CrossThread: return bitc::SYNCHSCOPE_CROSSTHREAD;
143   }
144   llvm_unreachable("Invalid synch scope");
145 }
146 
147 static void WriteStringRecord(unsigned Code, StringRef Str,
148                               unsigned AbbrevToUse, BitstreamWriter &Stream) {
149   SmallVector<unsigned, 64> Vals;
150 
151   // Code: [strchar x N]
152   for (unsigned i = 0, e = Str.size(); i != e; ++i) {
153     if (AbbrevToUse && !BitCodeAbbrevOp::isChar6(Str[i]))
154       AbbrevToUse = 0;
155     Vals.push_back(Str[i]);
156   }
157 
158   // Emit the finished record.
159   Stream.EmitRecord(Code, Vals, AbbrevToUse);
160 }
161 
162 static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
163   switch (Kind) {
164   case Attribute::Alignment:
165     return bitc::ATTR_KIND_ALIGNMENT;
166   case Attribute::AlwaysInline:
167     return bitc::ATTR_KIND_ALWAYS_INLINE;
168   case Attribute::Builtin:
169     return bitc::ATTR_KIND_BUILTIN;
170   case Attribute::ByVal:
171     return bitc::ATTR_KIND_BY_VAL;
172   case Attribute::InAlloca:
173     return bitc::ATTR_KIND_IN_ALLOCA;
174   case Attribute::Cold:
175     return bitc::ATTR_KIND_COLD;
176   case Attribute::InlineHint:
177     return bitc::ATTR_KIND_INLINE_HINT;
178   case Attribute::InReg:
179     return bitc::ATTR_KIND_IN_REG;
180   case Attribute::JumpTable:
181     return bitc::ATTR_KIND_JUMP_TABLE;
182   case Attribute::MinSize:
183     return bitc::ATTR_KIND_MIN_SIZE;
184   case Attribute::Naked:
185     return bitc::ATTR_KIND_NAKED;
186   case Attribute::Nest:
187     return bitc::ATTR_KIND_NEST;
188   case Attribute::NoAlias:
189     return bitc::ATTR_KIND_NO_ALIAS;
190   case Attribute::NoBuiltin:
191     return bitc::ATTR_KIND_NO_BUILTIN;
192   case Attribute::NoCapture:
193     return bitc::ATTR_KIND_NO_CAPTURE;
194   case Attribute::NoDuplicate:
195     return bitc::ATTR_KIND_NO_DUPLICATE;
196   case Attribute::NoImplicitFloat:
197     return bitc::ATTR_KIND_NO_IMPLICIT_FLOAT;
198   case Attribute::NoInline:
199     return bitc::ATTR_KIND_NO_INLINE;
200   case Attribute::NonLazyBind:
201     return bitc::ATTR_KIND_NON_LAZY_BIND;
202   case Attribute::NonNull:
203     return bitc::ATTR_KIND_NON_NULL;
204   case Attribute::Dereferenceable:
205     return bitc::ATTR_KIND_DEREFERENCEABLE;
206   case Attribute::NoRedZone:
207     return bitc::ATTR_KIND_NO_RED_ZONE;
208   case Attribute::NoReturn:
209     return bitc::ATTR_KIND_NO_RETURN;
210   case Attribute::NoUnwind:
211     return bitc::ATTR_KIND_NO_UNWIND;
212   case Attribute::OptimizeForSize:
213     return bitc::ATTR_KIND_OPTIMIZE_FOR_SIZE;
214   case Attribute::OptimizeNone:
215     return bitc::ATTR_KIND_OPTIMIZE_NONE;
216   case Attribute::ReadNone:
217     return bitc::ATTR_KIND_READ_NONE;
218   case Attribute::ReadOnly:
219     return bitc::ATTR_KIND_READ_ONLY;
220   case Attribute::Returned:
221     return bitc::ATTR_KIND_RETURNED;
222   case Attribute::ReturnsTwice:
223     return bitc::ATTR_KIND_RETURNS_TWICE;
224   case Attribute::SExt:
225     return bitc::ATTR_KIND_S_EXT;
226   case Attribute::StackAlignment:
227     return bitc::ATTR_KIND_STACK_ALIGNMENT;
228   case Attribute::StackProtect:
229     return bitc::ATTR_KIND_STACK_PROTECT;
230   case Attribute::StackProtectReq:
231     return bitc::ATTR_KIND_STACK_PROTECT_REQ;
232   case Attribute::StackProtectStrong:
233     return bitc::ATTR_KIND_STACK_PROTECT_STRONG;
234   case Attribute::StructRet:
235     return bitc::ATTR_KIND_STRUCT_RET;
236   case Attribute::SanitizeAddress:
237     return bitc::ATTR_KIND_SANITIZE_ADDRESS;
238   case Attribute::SanitizeThread:
239     return bitc::ATTR_KIND_SANITIZE_THREAD;
240   case Attribute::SanitizeMemory:
241     return bitc::ATTR_KIND_SANITIZE_MEMORY;
242   case Attribute::UWTable:
243     return bitc::ATTR_KIND_UW_TABLE;
244   case Attribute::ZExt:
245     return bitc::ATTR_KIND_Z_EXT;
246   case Attribute::EndAttrKinds:
247     llvm_unreachable("Can not encode end-attribute kinds marker.");
248   case Attribute::None:
249     llvm_unreachable("Can not encode none-attribute.");
250   }
251 
252   llvm_unreachable("Trying to encode unknown attribute");
253 }
254 
255 static void WriteAttributeGroupTable(const ValueEnumerator &VE,
256                                      BitstreamWriter &Stream) {
257   const std::vector<AttributeSet> &AttrGrps = VE.getAttributeGroups();
258   if (AttrGrps.empty()) return;
259 
260   Stream.EnterSubblock(bitc::PARAMATTR_GROUP_BLOCK_ID, 3);
261 
262   SmallVector<uint64_t, 64> Record;
263   for (unsigned i = 0, e = AttrGrps.size(); i != e; ++i) {
264     AttributeSet AS = AttrGrps[i];
265     for (unsigned i = 0, e = AS.getNumSlots(); i != e; ++i) {
266       AttributeSet A = AS.getSlotAttributes(i);
267 
268       Record.push_back(VE.getAttributeGroupID(A));
269       Record.push_back(AS.getSlotIndex(i));
270 
271       for (AttributeSet::iterator I = AS.begin(0), E = AS.end(0);
272            I != E; ++I) {
273         Attribute Attr = *I;
274         if (Attr.isEnumAttribute()) {
275           Record.push_back(0);
276           Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
277         } else if (Attr.isIntAttribute()) {
278           Record.push_back(1);
279           Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
280           Record.push_back(Attr.getValueAsInt());
281         } else {
282           StringRef Kind = Attr.getKindAsString();
283           StringRef Val = Attr.getValueAsString();
284 
285           Record.push_back(Val.empty() ? 3 : 4);
286           Record.append(Kind.begin(), Kind.end());
287           Record.push_back(0);
288           if (!Val.empty()) {
289             Record.append(Val.begin(), Val.end());
290             Record.push_back(0);
291           }
292         }
293       }
294 
295       Stream.EmitRecord(bitc::PARAMATTR_GRP_CODE_ENTRY, Record);
296       Record.clear();
297     }
298   }
299 
300   Stream.ExitBlock();
301 }
302 
303 static void WriteAttributeTable(const ValueEnumerator &VE,
304                                 BitstreamWriter &Stream) {
305   const std::vector<AttributeSet> &Attrs = VE.getAttributes();
306   if (Attrs.empty()) return;
307 
308   Stream.EnterSubblock(bitc::PARAMATTR_BLOCK_ID, 3);
309 
310   SmallVector<uint64_t, 64> Record;
311   for (unsigned i = 0, e = Attrs.size(); i != e; ++i) {
312     const AttributeSet &A = Attrs[i];
313     for (unsigned i = 0, e = A.getNumSlots(); i != e; ++i)
314       Record.push_back(VE.getAttributeGroupID(A.getSlotAttributes(i)));
315 
316     Stream.EmitRecord(bitc::PARAMATTR_CODE_ENTRY, Record);
317     Record.clear();
318   }
319 
320   Stream.ExitBlock();
321 }
322 
323 /// WriteTypeTable - Write out the type table for a module.
324 static void WriteTypeTable(const ValueEnumerator &VE, BitstreamWriter &Stream) {
325   const ValueEnumerator::TypeList &TypeList = VE.getTypes();
326 
327   Stream.EnterSubblock(bitc::TYPE_BLOCK_ID_NEW, 4 /*count from # abbrevs */);
328   SmallVector<uint64_t, 64> TypeVals;
329 
330   uint64_t NumBits = Log2_32_Ceil(VE.getTypes().size()+1);
331 
332   // Abbrev for TYPE_CODE_POINTER.
333   BitCodeAbbrev *Abbv = new BitCodeAbbrev();
334   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_POINTER));
335   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
336   Abbv->Add(BitCodeAbbrevOp(0));  // Addrspace = 0
337   unsigned PtrAbbrev = Stream.EmitAbbrev(Abbv);
338 
339   // Abbrev for TYPE_CODE_FUNCTION.
340   Abbv = new BitCodeAbbrev();
341   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_FUNCTION));
342   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // isvararg
343   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
344   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
345 
346   unsigned FunctionAbbrev = Stream.EmitAbbrev(Abbv);
347 
348   // Abbrev for TYPE_CODE_STRUCT_ANON.
349   Abbv = new BitCodeAbbrev();
350   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_ANON));
351   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
352   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
353   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
354 
355   unsigned StructAnonAbbrev = Stream.EmitAbbrev(Abbv);
356 
357   // Abbrev for TYPE_CODE_STRUCT_NAME.
358   Abbv = new BitCodeAbbrev();
359   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAME));
360   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
361   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
362   unsigned StructNameAbbrev = Stream.EmitAbbrev(Abbv);
363 
364   // Abbrev for TYPE_CODE_STRUCT_NAMED.
365   Abbv = new BitCodeAbbrev();
366   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAMED));
367   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
368   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
369   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
370 
371   unsigned StructNamedAbbrev = Stream.EmitAbbrev(Abbv);
372 
373   // Abbrev for TYPE_CODE_ARRAY.
374   Abbv = new BitCodeAbbrev();
375   Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_ARRAY));
376   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // size
377   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
378 
379   unsigned ArrayAbbrev = Stream.EmitAbbrev(Abbv);
380 
381   // Emit an entry count so the reader can reserve space.
382   TypeVals.push_back(TypeList.size());
383   Stream.EmitRecord(bitc::TYPE_CODE_NUMENTRY, TypeVals);
384   TypeVals.clear();
385 
386   // Loop over all of the types, emitting each in turn.
387   for (unsigned i = 0, e = TypeList.size(); i != e; ++i) {
388     Type *T = TypeList[i];
389     int AbbrevToUse = 0;
390     unsigned Code = 0;
391 
392     switch (T->getTypeID()) {
393     case Type::VoidTyID:      Code = bitc::TYPE_CODE_VOID;      break;
394     case Type::HalfTyID:      Code = bitc::TYPE_CODE_HALF;      break;
395     case Type::FloatTyID:     Code = bitc::TYPE_CODE_FLOAT;     break;
396     case Type::DoubleTyID:    Code = bitc::TYPE_CODE_DOUBLE;    break;
397     case Type::X86_FP80TyID:  Code = bitc::TYPE_CODE_X86_FP80;  break;
398     case Type::FP128TyID:     Code = bitc::TYPE_CODE_FP128;     break;
399     case Type::PPC_FP128TyID: Code = bitc::TYPE_CODE_PPC_FP128; break;
400     case Type::LabelTyID:     Code = bitc::TYPE_CODE_LABEL;     break;
401     case Type::MetadataTyID:  Code = bitc::TYPE_CODE_METADATA;  break;
402     case Type::X86_MMXTyID:   Code = bitc::TYPE_CODE_X86_MMX;   break;
403     case Type::IntegerTyID:
404       // INTEGER: [width]
405       Code = bitc::TYPE_CODE_INTEGER;
406       TypeVals.push_back(cast<IntegerType>(T)->getBitWidth());
407       break;
408     case Type::PointerTyID: {
409       PointerType *PTy = cast<PointerType>(T);
410       // POINTER: [pointee type, address space]
411       Code = bitc::TYPE_CODE_POINTER;
412       TypeVals.push_back(VE.getTypeID(PTy->getElementType()));
413       unsigned AddressSpace = PTy->getAddressSpace();
414       TypeVals.push_back(AddressSpace);
415       if (AddressSpace == 0) AbbrevToUse = PtrAbbrev;
416       break;
417     }
418     case Type::FunctionTyID: {
419       FunctionType *FT = cast<FunctionType>(T);
420       // FUNCTION: [isvararg, retty, paramty x N]
421       Code = bitc::TYPE_CODE_FUNCTION;
422       TypeVals.push_back(FT->isVarArg());
423       TypeVals.push_back(VE.getTypeID(FT->getReturnType()));
424       for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i)
425         TypeVals.push_back(VE.getTypeID(FT->getParamType(i)));
426       AbbrevToUse = FunctionAbbrev;
427       break;
428     }
429     case Type::StructTyID: {
430       StructType *ST = cast<StructType>(T);
431       // STRUCT: [ispacked, eltty x N]
432       TypeVals.push_back(ST->isPacked());
433       // Output all of the element types.
434       for (StructType::element_iterator I = ST->element_begin(),
435            E = ST->element_end(); I != E; ++I)
436         TypeVals.push_back(VE.getTypeID(*I));
437 
438       if (ST->isLiteral()) {
439         Code = bitc::TYPE_CODE_STRUCT_ANON;
440         AbbrevToUse = StructAnonAbbrev;
441       } else {
442         if (ST->isOpaque()) {
443           Code = bitc::TYPE_CODE_OPAQUE;
444         } else {
445           Code = bitc::TYPE_CODE_STRUCT_NAMED;
446           AbbrevToUse = StructNamedAbbrev;
447         }
448 
449         // Emit the name if it is present.
450         if (!ST->getName().empty())
451           WriteStringRecord(bitc::TYPE_CODE_STRUCT_NAME, ST->getName(),
452                             StructNameAbbrev, Stream);
453       }
454       break;
455     }
456     case Type::ArrayTyID: {
457       ArrayType *AT = cast<ArrayType>(T);
458       // ARRAY: [numelts, eltty]
459       Code = bitc::TYPE_CODE_ARRAY;
460       TypeVals.push_back(AT->getNumElements());
461       TypeVals.push_back(VE.getTypeID(AT->getElementType()));
462       AbbrevToUse = ArrayAbbrev;
463       break;
464     }
465     case Type::VectorTyID: {
466       VectorType *VT = cast<VectorType>(T);
467       // VECTOR [numelts, eltty]
468       Code = bitc::TYPE_CODE_VECTOR;
469       TypeVals.push_back(VT->getNumElements());
470       TypeVals.push_back(VE.getTypeID(VT->getElementType()));
471       break;
472     }
473     }
474 
475     // Emit the finished record.
476     Stream.EmitRecord(Code, TypeVals, AbbrevToUse);
477     TypeVals.clear();
478   }
479 
480   Stream.ExitBlock();
481 }
482 
483 static unsigned getEncodedLinkage(const GlobalValue &GV) {
484   switch (GV.getLinkage()) {
485   case GlobalValue::ExternalLinkage:                 return 0;
486   case GlobalValue::WeakAnyLinkage:                  return 1;
487   case GlobalValue::AppendingLinkage:                return 2;
488   case GlobalValue::InternalLinkage:                 return 3;
489   case GlobalValue::LinkOnceAnyLinkage:              return 4;
490   case GlobalValue::ExternalWeakLinkage:             return 7;
491   case GlobalValue::CommonLinkage:                   return 8;
492   case GlobalValue::PrivateLinkage:                  return 9;
493   case GlobalValue::WeakODRLinkage:                  return 10;
494   case GlobalValue::LinkOnceODRLinkage:              return 11;
495   case GlobalValue::AvailableExternallyLinkage:      return 12;
496   }
497   llvm_unreachable("Invalid linkage");
498 }
499 
500 static unsigned getEncodedVisibility(const GlobalValue &GV) {
501   switch (GV.getVisibility()) {
502   case GlobalValue::DefaultVisibility:   return 0;
503   case GlobalValue::HiddenVisibility:    return 1;
504   case GlobalValue::ProtectedVisibility: return 2;
505   }
506   llvm_unreachable("Invalid visibility");
507 }
508 
509 static unsigned getEncodedDLLStorageClass(const GlobalValue &GV) {
510   switch (GV.getDLLStorageClass()) {
511   case GlobalValue::DefaultStorageClass:   return 0;
512   case GlobalValue::DLLImportStorageClass: return 1;
513   case GlobalValue::DLLExportStorageClass: return 2;
514   }
515   llvm_unreachable("Invalid DLL storage class");
516 }
517 
518 static unsigned getEncodedThreadLocalMode(const GlobalValue &GV) {
519   switch (GV.getThreadLocalMode()) {
520     case GlobalVariable::NotThreadLocal:         return 0;
521     case GlobalVariable::GeneralDynamicTLSModel: return 1;
522     case GlobalVariable::LocalDynamicTLSModel:   return 2;
523     case GlobalVariable::InitialExecTLSModel:    return 3;
524     case GlobalVariable::LocalExecTLSModel:      return 4;
525   }
526   llvm_unreachable("Invalid TLS model");
527 }
528 
529 static unsigned getEncodedComdatSelectionKind(const Comdat &C) {
530   switch (C.getSelectionKind()) {
531   case Comdat::Any:
532     return bitc::COMDAT_SELECTION_KIND_ANY;
533   case Comdat::ExactMatch:
534     return bitc::COMDAT_SELECTION_KIND_EXACT_MATCH;
535   case Comdat::Largest:
536     return bitc::COMDAT_SELECTION_KIND_LARGEST;
537   case Comdat::NoDuplicates:
538     return bitc::COMDAT_SELECTION_KIND_NO_DUPLICATES;
539   case Comdat::SameSize:
540     return bitc::COMDAT_SELECTION_KIND_SAME_SIZE;
541   }
542   llvm_unreachable("Invalid selection kind");
543 }
544 
545 static void writeComdats(const ValueEnumerator &VE, BitstreamWriter &Stream) {
546   SmallVector<uint8_t, 64> Vals;
547   for (const Comdat *C : VE.getComdats()) {
548     // COMDAT: [selection_kind, name]
549     Vals.push_back(getEncodedComdatSelectionKind(*C));
550     Vals.push_back(C->getName().size());
551     for (char Chr : C->getName())
552       Vals.push_back((unsigned char)Chr);
553     Stream.EmitRecord(bitc::MODULE_CODE_COMDAT, Vals, /*AbbrevToUse=*/0);
554     Vals.clear();
555   }
556 }
557 
558 // Emit top-level description of module, including target triple, inline asm,
559 // descriptors for global variables, and function prototype info.
560 static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
561                             BitstreamWriter &Stream) {
562   // Emit various pieces of data attached to a module.
563   if (!M->getTargetTriple().empty())
564     WriteStringRecord(bitc::MODULE_CODE_TRIPLE, M->getTargetTriple(),
565                       0/*TODO*/, Stream);
566   const std::string &DL = M->getDataLayoutStr();
567   if (!DL.empty())
568     WriteStringRecord(bitc::MODULE_CODE_DATALAYOUT, DL, 0 /*TODO*/, Stream);
569   if (!M->getModuleInlineAsm().empty())
570     WriteStringRecord(bitc::MODULE_CODE_ASM, M->getModuleInlineAsm(),
571                       0/*TODO*/, Stream);
572 
573   // Emit information about sections and GC, computing how many there are. Also
574   // compute the maximum alignment value.
575   std::map<std::string, unsigned> SectionMap;
576   std::map<std::string, unsigned> GCMap;
577   unsigned MaxAlignment = 0;
578   unsigned MaxGlobalType = 0;
579   for (const GlobalValue &GV : M->globals()) {
580     MaxAlignment = std::max(MaxAlignment, GV.getAlignment());
581     MaxGlobalType = std::max(MaxGlobalType, VE.getTypeID(GV.getType()));
582     if (GV.hasSection()) {
583       // Give section names unique ID's.
584       unsigned &Entry = SectionMap[GV.getSection()];
585       if (!Entry) {
586         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, GV.getSection(),
587                           0/*TODO*/, Stream);
588         Entry = SectionMap.size();
589       }
590     }
591   }
592   for (const Function &F : *M) {
593     MaxAlignment = std::max(MaxAlignment, F.getAlignment());
594     if (F.hasSection()) {
595       // Give section names unique ID's.
596       unsigned &Entry = SectionMap[F.getSection()];
597       if (!Entry) {
598         WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, F.getSection(),
599                           0/*TODO*/, Stream);
600         Entry = SectionMap.size();
601       }
602     }
603     if (F.hasGC()) {
604       // Same for GC names.
605       unsigned &Entry = GCMap[F.getGC()];
606       if (!Entry) {
607         WriteStringRecord(bitc::MODULE_CODE_GCNAME, F.getGC(),
608                           0/*TODO*/, Stream);
609         Entry = GCMap.size();
610       }
611     }
612   }
613 
614   // Emit abbrev for globals, now that we know # sections and max alignment.
615   unsigned SimpleGVarAbbrev = 0;
616   if (!M->global_empty()) {
617     // Add an abbrev for common globals with no visibility or thread localness.
618     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
619     Abbv->Add(BitCodeAbbrevOp(bitc::MODULE_CODE_GLOBALVAR));
620     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
621                               Log2_32_Ceil(MaxGlobalType+1)));
622     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));      // Constant.
623     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));        // Initializer.
624     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));      // Linkage.
625     if (MaxAlignment == 0)                                      // Alignment.
626       Abbv->Add(BitCodeAbbrevOp(0));
627     else {
628       unsigned MaxEncAlignment = Log2_32(MaxAlignment)+1;
629       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
630                                Log2_32_Ceil(MaxEncAlignment+1)));
631     }
632     if (SectionMap.empty())                                    // Section.
633       Abbv->Add(BitCodeAbbrevOp(0));
634     else
635       Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
636                                Log2_32_Ceil(SectionMap.size()+1)));
637     // Don't bother emitting vis + thread local.
638     SimpleGVarAbbrev = Stream.EmitAbbrev(Abbv);
639   }
640 
641   // Emit the global variable information.
642   SmallVector<unsigned, 64> Vals;
643   for (const GlobalVariable &GV : M->globals()) {
644     unsigned AbbrevToUse = 0;
645 
646     // GLOBALVAR: [type, isconst, initid,
647     //             linkage, alignment, section, visibility, threadlocal,
648     //             unnamed_addr, externally_initialized, dllstorageclass]
649     Vals.push_back(VE.getTypeID(GV.getType()));
650     Vals.push_back(GV.isConstant());
651     Vals.push_back(GV.isDeclaration() ? 0 :
652                    (VE.getValueID(GV.getInitializer()) + 1));
653     Vals.push_back(getEncodedLinkage(GV));
654     Vals.push_back(Log2_32(GV.getAlignment())+1);
655     Vals.push_back(GV.hasSection() ? SectionMap[GV.getSection()] : 0);
656     if (GV.isThreadLocal() ||
657         GV.getVisibility() != GlobalValue::DefaultVisibility ||
658         GV.hasUnnamedAddr() || GV.isExternallyInitialized() ||
659         GV.getDLLStorageClass() != GlobalValue::DefaultStorageClass ||
660         GV.hasComdat()) {
661       Vals.push_back(getEncodedVisibility(GV));
662       Vals.push_back(getEncodedThreadLocalMode(GV));
663       Vals.push_back(GV.hasUnnamedAddr());
664       Vals.push_back(GV.isExternallyInitialized());
665       Vals.push_back(getEncodedDLLStorageClass(GV));
666       Vals.push_back(GV.hasComdat() ? VE.getComdatID(GV.getComdat()) : 0);
667     } else {
668       AbbrevToUse = SimpleGVarAbbrev;
669     }
670 
671     Stream.EmitRecord(bitc::MODULE_CODE_GLOBALVAR, Vals, AbbrevToUse);
672     Vals.clear();
673   }
674 
675   // Emit the function proto information.
676   for (const Function &F : *M) {
677     // FUNCTION:  [type, callingconv, isproto, linkage, paramattrs, alignment,
678     //             section, visibility, gc, unnamed_addr, prefix]
679     Vals.push_back(VE.getTypeID(F.getType()));
680     Vals.push_back(F.getCallingConv());
681     Vals.push_back(F.isDeclaration());
682     Vals.push_back(getEncodedLinkage(F));
683     Vals.push_back(VE.getAttributeID(F.getAttributes()));
684     Vals.push_back(Log2_32(F.getAlignment())+1);
685     Vals.push_back(F.hasSection() ? SectionMap[F.getSection()] : 0);
686     Vals.push_back(getEncodedVisibility(F));
687     Vals.push_back(F.hasGC() ? GCMap[F.getGC()] : 0);
688     Vals.push_back(F.hasUnnamedAddr());
689     Vals.push_back(F.hasPrefixData() ? (VE.getValueID(F.getPrefixData()) + 1)
690                                       : 0);
691     Vals.push_back(getEncodedDLLStorageClass(F));
692     Vals.push_back(F.hasComdat() ? VE.getComdatID(F.getComdat()) : 0);
693 
694     unsigned AbbrevToUse = 0;
695     Stream.EmitRecord(bitc::MODULE_CODE_FUNCTION, Vals, AbbrevToUse);
696     Vals.clear();
697   }
698 
699   // Emit the alias information.
700   for (const GlobalAlias &A : M->aliases()) {
701     // ALIAS: [alias type, aliasee val#, linkage, visibility]
702     Vals.push_back(VE.getTypeID(A.getType()));
703     Vals.push_back(VE.getValueID(A.getAliasee()));
704     Vals.push_back(getEncodedLinkage(A));
705     Vals.push_back(getEncodedVisibility(A));
706     Vals.push_back(getEncodedDLLStorageClass(A));
707     Vals.push_back(getEncodedThreadLocalMode(A));
708     Vals.push_back(A.hasUnnamedAddr());
709     unsigned AbbrevToUse = 0;
710     Stream.EmitRecord(bitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
711     Vals.clear();
712   }
713 }
714 
715 static uint64_t GetOptimizationFlags(const Value *V) {
716   uint64_t Flags = 0;
717 
718   if (const OverflowingBinaryOperator *OBO =
719         dyn_cast<OverflowingBinaryOperator>(V)) {
720     if (OBO->hasNoSignedWrap())
721       Flags |= 1 << bitc::OBO_NO_SIGNED_WRAP;
722     if (OBO->hasNoUnsignedWrap())
723       Flags |= 1 << bitc::OBO_NO_UNSIGNED_WRAP;
724   } else if (const PossiblyExactOperator *PEO =
725                dyn_cast<PossiblyExactOperator>(V)) {
726     if (PEO->isExact())
727       Flags |= 1 << bitc::PEO_EXACT;
728   } else if (const FPMathOperator *FPMO =
729              dyn_cast<const FPMathOperator>(V)) {
730     if (FPMO->hasUnsafeAlgebra())
731       Flags |= FastMathFlags::UnsafeAlgebra;
732     if (FPMO->hasNoNaNs())
733       Flags |= FastMathFlags::NoNaNs;
734     if (FPMO->hasNoInfs())
735       Flags |= FastMathFlags::NoInfs;
736     if (FPMO->hasNoSignedZeros())
737       Flags |= FastMathFlags::NoSignedZeros;
738     if (FPMO->hasAllowReciprocal())
739       Flags |= FastMathFlags::AllowReciprocal;
740   }
741 
742   return Flags;
743 }
744 
745 static void WriteMDNode(const MDNode *N,
746                         const ValueEnumerator &VE,
747                         BitstreamWriter &Stream,
748                         SmallVectorImpl<uint64_t> &Record) {
749   for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
750     if (N->getOperand(i)) {
751       Record.push_back(VE.getTypeID(N->getOperand(i)->getType()));
752       Record.push_back(VE.getValueID(N->getOperand(i)));
753     } else {
754       Record.push_back(VE.getTypeID(Type::getVoidTy(N->getContext())));
755       Record.push_back(0);
756     }
757   }
758   unsigned MDCode = N->isFunctionLocal() ? bitc::METADATA_FN_NODE :
759                                            bitc::METADATA_NODE;
760   Stream.EmitRecord(MDCode, Record, 0);
761   Record.clear();
762 }
763 
764 static void WriteModuleMetadata(const Module *M,
765                                 const ValueEnumerator &VE,
766                                 BitstreamWriter &Stream) {
767   const ValueEnumerator::ValueList &Vals = VE.getMDValues();
768   bool StartedMetadataBlock = false;
769   unsigned MDSAbbrev = 0;
770   SmallVector<uint64_t, 64> Record;
771   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
772 
773     if (const MDNode *N = dyn_cast<MDNode>(Vals[i].first)) {
774       if (!N->isFunctionLocal() || !N->getFunction()) {
775         if (!StartedMetadataBlock) {
776           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
777           StartedMetadataBlock = true;
778         }
779         WriteMDNode(N, VE, Stream, Record);
780       }
781     } else if (const MDString *MDS = dyn_cast<MDString>(Vals[i].first)) {
782       if (!StartedMetadataBlock)  {
783         Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
784 
785         // Abbrev for METADATA_STRING.
786         BitCodeAbbrev *Abbv = new BitCodeAbbrev();
787         Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_STRING));
788         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
789         Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
790         MDSAbbrev = Stream.EmitAbbrev(Abbv);
791         StartedMetadataBlock = true;
792       }
793 
794       // Code: [strchar x N]
795       Record.append(MDS->begin(), MDS->end());
796 
797       // Emit the finished record.
798       Stream.EmitRecord(bitc::METADATA_STRING, Record, MDSAbbrev);
799       Record.clear();
800     }
801   }
802 
803   // Write named metadata.
804   for (Module::const_named_metadata_iterator I = M->named_metadata_begin(),
805        E = M->named_metadata_end(); I != E; ++I) {
806     const NamedMDNode *NMD = I;
807     if (!StartedMetadataBlock)  {
808       Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
809       StartedMetadataBlock = true;
810     }
811 
812     // Write name.
813     StringRef Str = NMD->getName();
814     for (unsigned i = 0, e = Str.size(); i != e; ++i)
815       Record.push_back(Str[i]);
816     Stream.EmitRecord(bitc::METADATA_NAME, Record, 0/*TODO*/);
817     Record.clear();
818 
819     // Write named metadata operands.
820     for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
821       Record.push_back(VE.getValueID(NMD->getOperand(i)));
822     Stream.EmitRecord(bitc::METADATA_NAMED_NODE, Record, 0);
823     Record.clear();
824   }
825 
826   if (StartedMetadataBlock)
827     Stream.ExitBlock();
828 }
829 
830 static void WriteFunctionLocalMetadata(const Function &F,
831                                        const ValueEnumerator &VE,
832                                        BitstreamWriter &Stream) {
833   bool StartedMetadataBlock = false;
834   SmallVector<uint64_t, 64> Record;
835   const SmallVectorImpl<const MDNode *> &Vals = VE.getFunctionLocalMDValues();
836   for (unsigned i = 0, e = Vals.size(); i != e; ++i)
837     if (const MDNode *N = Vals[i])
838       if (N->isFunctionLocal() && N->getFunction() == &F) {
839         if (!StartedMetadataBlock) {
840           Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
841           StartedMetadataBlock = true;
842         }
843         WriteMDNode(N, VE, Stream, Record);
844       }
845 
846   if (StartedMetadataBlock)
847     Stream.ExitBlock();
848 }
849 
850 static void WriteMetadataAttachment(const Function &F,
851                                     const ValueEnumerator &VE,
852                                     BitstreamWriter &Stream) {
853   Stream.EnterSubblock(bitc::METADATA_ATTACHMENT_ID, 3);
854 
855   SmallVector<uint64_t, 64> Record;
856 
857   // Write metadata attachments
858   // METADATA_ATTACHMENT - [m x [value, [n x [id, mdnode]]]
859   SmallVector<std::pair<unsigned, MDNode*>, 4> MDs;
860 
861   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
862     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
863          I != E; ++I) {
864       MDs.clear();
865       I->getAllMetadataOtherThanDebugLoc(MDs);
866 
867       // If no metadata, ignore instruction.
868       if (MDs.empty()) continue;
869 
870       Record.push_back(VE.getInstructionID(I));
871 
872       for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
873         Record.push_back(MDs[i].first);
874         Record.push_back(VE.getValueID(MDs[i].second));
875       }
876       Stream.EmitRecord(bitc::METADATA_ATTACHMENT, Record, 0);
877       Record.clear();
878     }
879 
880   Stream.ExitBlock();
881 }
882 
883 static void WriteModuleMetadataStore(const Module *M, BitstreamWriter &Stream) {
884   SmallVector<uint64_t, 64> Record;
885 
886   // Write metadata kinds
887   // METADATA_KIND - [n x [id, name]]
888   SmallVector<StringRef, 8> Names;
889   M->getMDKindNames(Names);
890 
891   if (Names.empty()) return;
892 
893   Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
894 
895   for (unsigned MDKindID = 0, e = Names.size(); MDKindID != e; ++MDKindID) {
896     Record.push_back(MDKindID);
897     StringRef KName = Names[MDKindID];
898     Record.append(KName.begin(), KName.end());
899 
900     Stream.EmitRecord(bitc::METADATA_KIND, Record, 0);
901     Record.clear();
902   }
903 
904   Stream.ExitBlock();
905 }
906 
907 static void emitSignedInt64(SmallVectorImpl<uint64_t> &Vals, uint64_t V) {
908   if ((int64_t)V >= 0)
909     Vals.push_back(V << 1);
910   else
911     Vals.push_back((-V << 1) | 1);
912 }
913 
914 static void WriteConstants(unsigned FirstVal, unsigned LastVal,
915                            const ValueEnumerator &VE,
916                            BitstreamWriter &Stream, bool isGlobal) {
917   if (FirstVal == LastVal) return;
918 
919   Stream.EnterSubblock(bitc::CONSTANTS_BLOCK_ID, 4);
920 
921   unsigned AggregateAbbrev = 0;
922   unsigned String8Abbrev = 0;
923   unsigned CString7Abbrev = 0;
924   unsigned CString6Abbrev = 0;
925   // If this is a constant pool for the module, emit module-specific abbrevs.
926   if (isGlobal) {
927     // Abbrev for CST_CODE_AGGREGATE.
928     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
929     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_AGGREGATE));
930     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
931     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, Log2_32_Ceil(LastVal+1)));
932     AggregateAbbrev = Stream.EmitAbbrev(Abbv);
933 
934     // Abbrev for CST_CODE_STRING.
935     Abbv = new BitCodeAbbrev();
936     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_STRING));
937     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
938     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
939     String8Abbrev = Stream.EmitAbbrev(Abbv);
940     // Abbrev for CST_CODE_CSTRING.
941     Abbv = new BitCodeAbbrev();
942     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
943     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
944     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
945     CString7Abbrev = Stream.EmitAbbrev(Abbv);
946     // Abbrev for CST_CODE_CSTRING.
947     Abbv = new BitCodeAbbrev();
948     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CSTRING));
949     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
950     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
951     CString6Abbrev = Stream.EmitAbbrev(Abbv);
952   }
953 
954   SmallVector<uint64_t, 64> Record;
955 
956   const ValueEnumerator::ValueList &Vals = VE.getValues();
957   Type *LastTy = nullptr;
958   for (unsigned i = FirstVal; i != LastVal; ++i) {
959     const Value *V = Vals[i].first;
960     // If we need to switch types, do so now.
961     if (V->getType() != LastTy) {
962       LastTy = V->getType();
963       Record.push_back(VE.getTypeID(LastTy));
964       Stream.EmitRecord(bitc::CST_CODE_SETTYPE, Record,
965                         CONSTANTS_SETTYPE_ABBREV);
966       Record.clear();
967     }
968 
969     if (const InlineAsm *IA = dyn_cast<InlineAsm>(V)) {
970       Record.push_back(unsigned(IA->hasSideEffects()) |
971                        unsigned(IA->isAlignStack()) << 1 |
972                        unsigned(IA->getDialect()&1) << 2);
973 
974       // Add the asm string.
975       const std::string &AsmStr = IA->getAsmString();
976       Record.push_back(AsmStr.size());
977       for (unsigned i = 0, e = AsmStr.size(); i != e; ++i)
978         Record.push_back(AsmStr[i]);
979 
980       // Add the constraint string.
981       const std::string &ConstraintStr = IA->getConstraintString();
982       Record.push_back(ConstraintStr.size());
983       for (unsigned i = 0, e = ConstraintStr.size(); i != e; ++i)
984         Record.push_back(ConstraintStr[i]);
985       Stream.EmitRecord(bitc::CST_CODE_INLINEASM, Record);
986       Record.clear();
987       continue;
988     }
989     const Constant *C = cast<Constant>(V);
990     unsigned Code = -1U;
991     unsigned AbbrevToUse = 0;
992     if (C->isNullValue()) {
993       Code = bitc::CST_CODE_NULL;
994     } else if (isa<UndefValue>(C)) {
995       Code = bitc::CST_CODE_UNDEF;
996     } else if (const ConstantInt *IV = dyn_cast<ConstantInt>(C)) {
997       if (IV->getBitWidth() <= 64) {
998         uint64_t V = IV->getSExtValue();
999         emitSignedInt64(Record, V);
1000         Code = bitc::CST_CODE_INTEGER;
1001         AbbrevToUse = CONSTANTS_INTEGER_ABBREV;
1002       } else {                             // Wide integers, > 64 bits in size.
1003         // We have an arbitrary precision integer value to write whose
1004         // bit width is > 64. However, in canonical unsigned integer
1005         // format it is likely that the high bits are going to be zero.
1006         // So, we only write the number of active words.
1007         unsigned NWords = IV->getValue().getActiveWords();
1008         const uint64_t *RawWords = IV->getValue().getRawData();
1009         for (unsigned i = 0; i != NWords; ++i) {
1010           emitSignedInt64(Record, RawWords[i]);
1011         }
1012         Code = bitc::CST_CODE_WIDE_INTEGER;
1013       }
1014     } else if (const ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
1015       Code = bitc::CST_CODE_FLOAT;
1016       Type *Ty = CFP->getType();
1017       if (Ty->isHalfTy() || Ty->isFloatTy() || Ty->isDoubleTy()) {
1018         Record.push_back(CFP->getValueAPF().bitcastToAPInt().getZExtValue());
1019       } else if (Ty->isX86_FP80Ty()) {
1020         // api needed to prevent premature destruction
1021         // bits are not in the same order as a normal i80 APInt, compensate.
1022         APInt api = CFP->getValueAPF().bitcastToAPInt();
1023         const uint64_t *p = api.getRawData();
1024         Record.push_back((p[1] << 48) | (p[0] >> 16));
1025         Record.push_back(p[0] & 0xffffLL);
1026       } else if (Ty->isFP128Ty() || Ty->isPPC_FP128Ty()) {
1027         APInt api = CFP->getValueAPF().bitcastToAPInt();
1028         const uint64_t *p = api.getRawData();
1029         Record.push_back(p[0]);
1030         Record.push_back(p[1]);
1031       } else {
1032         assert (0 && "Unknown FP type!");
1033       }
1034     } else if (isa<ConstantDataSequential>(C) &&
1035                cast<ConstantDataSequential>(C)->isString()) {
1036       const ConstantDataSequential *Str = cast<ConstantDataSequential>(C);
1037       // Emit constant strings specially.
1038       unsigned NumElts = Str->getNumElements();
1039       // If this is a null-terminated string, use the denser CSTRING encoding.
1040       if (Str->isCString()) {
1041         Code = bitc::CST_CODE_CSTRING;
1042         --NumElts;  // Don't encode the null, which isn't allowed by char6.
1043       } else {
1044         Code = bitc::CST_CODE_STRING;
1045         AbbrevToUse = String8Abbrev;
1046       }
1047       bool isCStr7 = Code == bitc::CST_CODE_CSTRING;
1048       bool isCStrChar6 = Code == bitc::CST_CODE_CSTRING;
1049       for (unsigned i = 0; i != NumElts; ++i) {
1050         unsigned char V = Str->getElementAsInteger(i);
1051         Record.push_back(V);
1052         isCStr7 &= (V & 128) == 0;
1053         if (isCStrChar6)
1054           isCStrChar6 = BitCodeAbbrevOp::isChar6(V);
1055       }
1056 
1057       if (isCStrChar6)
1058         AbbrevToUse = CString6Abbrev;
1059       else if (isCStr7)
1060         AbbrevToUse = CString7Abbrev;
1061     } else if (const ConstantDataSequential *CDS =
1062                   dyn_cast<ConstantDataSequential>(C)) {
1063       Code = bitc::CST_CODE_DATA;
1064       Type *EltTy = CDS->getType()->getElementType();
1065       if (isa<IntegerType>(EltTy)) {
1066         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i)
1067           Record.push_back(CDS->getElementAsInteger(i));
1068       } else if (EltTy->isFloatTy()) {
1069         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
1070           union { float F; uint32_t I; };
1071           F = CDS->getElementAsFloat(i);
1072           Record.push_back(I);
1073         }
1074       } else {
1075         assert(EltTy->isDoubleTy() && "Unknown ConstantData element type");
1076         for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
1077           union { double F; uint64_t I; };
1078           F = CDS->getElementAsDouble(i);
1079           Record.push_back(I);
1080         }
1081       }
1082     } else if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
1083                isa<ConstantVector>(C)) {
1084       Code = bitc::CST_CODE_AGGREGATE;
1085       for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
1086         Record.push_back(VE.getValueID(C->getOperand(i)));
1087       AbbrevToUse = AggregateAbbrev;
1088     } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
1089       switch (CE->getOpcode()) {
1090       default:
1091         if (Instruction::isCast(CE->getOpcode())) {
1092           Code = bitc::CST_CODE_CE_CAST;
1093           Record.push_back(GetEncodedCastOpcode(CE->getOpcode()));
1094           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1095           Record.push_back(VE.getValueID(C->getOperand(0)));
1096           AbbrevToUse = CONSTANTS_CE_CAST_Abbrev;
1097         } else {
1098           assert(CE->getNumOperands() == 2 && "Unknown constant expr!");
1099           Code = bitc::CST_CODE_CE_BINOP;
1100           Record.push_back(GetEncodedBinaryOpcode(CE->getOpcode()));
1101           Record.push_back(VE.getValueID(C->getOperand(0)));
1102           Record.push_back(VE.getValueID(C->getOperand(1)));
1103           uint64_t Flags = GetOptimizationFlags(CE);
1104           if (Flags != 0)
1105             Record.push_back(Flags);
1106         }
1107         break;
1108       case Instruction::GetElementPtr:
1109         Code = bitc::CST_CODE_CE_GEP;
1110         if (cast<GEPOperator>(C)->isInBounds())
1111           Code = bitc::CST_CODE_CE_INBOUNDS_GEP;
1112         for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {
1113           Record.push_back(VE.getTypeID(C->getOperand(i)->getType()));
1114           Record.push_back(VE.getValueID(C->getOperand(i)));
1115         }
1116         break;
1117       case Instruction::Select:
1118         Code = bitc::CST_CODE_CE_SELECT;
1119         Record.push_back(VE.getValueID(C->getOperand(0)));
1120         Record.push_back(VE.getValueID(C->getOperand(1)));
1121         Record.push_back(VE.getValueID(C->getOperand(2)));
1122         break;
1123       case Instruction::ExtractElement:
1124         Code = bitc::CST_CODE_CE_EXTRACTELT;
1125         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1126         Record.push_back(VE.getValueID(C->getOperand(0)));
1127         Record.push_back(VE.getTypeID(C->getOperand(1)->getType()));
1128         Record.push_back(VE.getValueID(C->getOperand(1)));
1129         break;
1130       case Instruction::InsertElement:
1131         Code = bitc::CST_CODE_CE_INSERTELT;
1132         Record.push_back(VE.getValueID(C->getOperand(0)));
1133         Record.push_back(VE.getValueID(C->getOperand(1)));
1134         Record.push_back(VE.getTypeID(C->getOperand(2)->getType()));
1135         Record.push_back(VE.getValueID(C->getOperand(2)));
1136         break;
1137       case Instruction::ShuffleVector:
1138         // If the return type and argument types are the same, this is a
1139         // standard shufflevector instruction.  If the types are different,
1140         // then the shuffle is widening or truncating the input vectors, and
1141         // the argument type must also be encoded.
1142         if (C->getType() == C->getOperand(0)->getType()) {
1143           Code = bitc::CST_CODE_CE_SHUFFLEVEC;
1144         } else {
1145           Code = bitc::CST_CODE_CE_SHUFVEC_EX;
1146           Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1147         }
1148         Record.push_back(VE.getValueID(C->getOperand(0)));
1149         Record.push_back(VE.getValueID(C->getOperand(1)));
1150         Record.push_back(VE.getValueID(C->getOperand(2)));
1151         break;
1152       case Instruction::ICmp:
1153       case Instruction::FCmp:
1154         Code = bitc::CST_CODE_CE_CMP;
1155         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));
1156         Record.push_back(VE.getValueID(C->getOperand(0)));
1157         Record.push_back(VE.getValueID(C->getOperand(1)));
1158         Record.push_back(CE->getPredicate());
1159         break;
1160       }
1161     } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
1162       Code = bitc::CST_CODE_BLOCKADDRESS;
1163       Record.push_back(VE.getTypeID(BA->getFunction()->getType()));
1164       Record.push_back(VE.getValueID(BA->getFunction()));
1165       Record.push_back(VE.getGlobalBasicBlockID(BA->getBasicBlock()));
1166     } else {
1167 #ifndef NDEBUG
1168       C->dump();
1169 #endif
1170       llvm_unreachable("Unknown constant!");
1171     }
1172     Stream.EmitRecord(Code, Record, AbbrevToUse);
1173     Record.clear();
1174   }
1175 
1176   Stream.ExitBlock();
1177 }
1178 
1179 static void WriteModuleConstants(const ValueEnumerator &VE,
1180                                  BitstreamWriter &Stream) {
1181   const ValueEnumerator::ValueList &Vals = VE.getValues();
1182 
1183   // Find the first constant to emit, which is the first non-globalvalue value.
1184   // We know globalvalues have been emitted by WriteModuleInfo.
1185   for (unsigned i = 0, e = Vals.size(); i != e; ++i) {
1186     if (!isa<GlobalValue>(Vals[i].first)) {
1187       WriteConstants(i, Vals.size(), VE, Stream, true);
1188       return;
1189     }
1190   }
1191 }
1192 
1193 /// PushValueAndType - The file has to encode both the value and type id for
1194 /// many values, because we need to know what type to create for forward
1195 /// references.  However, most operands are not forward references, so this type
1196 /// field is not needed.
1197 ///
1198 /// This function adds V's value ID to Vals.  If the value ID is higher than the
1199 /// instruction ID, then it is a forward reference, and it also includes the
1200 /// type ID.  The value ID that is written is encoded relative to the InstID.
1201 static bool PushValueAndType(const Value *V, unsigned InstID,
1202                              SmallVectorImpl<unsigned> &Vals,
1203                              ValueEnumerator &VE) {
1204   unsigned ValID = VE.getValueID(V);
1205   // Make encoding relative to the InstID.
1206   Vals.push_back(InstID - ValID);
1207   if (ValID >= InstID) {
1208     Vals.push_back(VE.getTypeID(V->getType()));
1209     return true;
1210   }
1211   return false;
1212 }
1213 
1214 /// pushValue - Like PushValueAndType, but where the type of the value is
1215 /// omitted (perhaps it was already encoded in an earlier operand).
1216 static void pushValue(const Value *V, unsigned InstID,
1217                       SmallVectorImpl<unsigned> &Vals,
1218                       ValueEnumerator &VE) {
1219   unsigned ValID = VE.getValueID(V);
1220   Vals.push_back(InstID - ValID);
1221 }
1222 
1223 static void pushValueSigned(const Value *V, unsigned InstID,
1224                             SmallVectorImpl<uint64_t> &Vals,
1225                             ValueEnumerator &VE) {
1226   unsigned ValID = VE.getValueID(V);
1227   int64_t diff = ((int32_t)InstID - (int32_t)ValID);
1228   emitSignedInt64(Vals, diff);
1229 }
1230 
1231 /// WriteInstruction - Emit an instruction to the specified stream.
1232 static void WriteInstruction(const Instruction &I, unsigned InstID,
1233                              ValueEnumerator &VE, BitstreamWriter &Stream,
1234                              SmallVectorImpl<unsigned> &Vals) {
1235   unsigned Code = 0;
1236   unsigned AbbrevToUse = 0;
1237   VE.setInstructionID(&I);
1238   switch (I.getOpcode()) {
1239   default:
1240     if (Instruction::isCast(I.getOpcode())) {
1241       Code = bitc::FUNC_CODE_INST_CAST;
1242       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1243         AbbrevToUse = FUNCTION_INST_CAST_ABBREV;
1244       Vals.push_back(VE.getTypeID(I.getType()));
1245       Vals.push_back(GetEncodedCastOpcode(I.getOpcode()));
1246     } else {
1247       assert(isa<BinaryOperator>(I) && "Unknown instruction!");
1248       Code = bitc::FUNC_CODE_INST_BINOP;
1249       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1250         AbbrevToUse = FUNCTION_INST_BINOP_ABBREV;
1251       pushValue(I.getOperand(1), InstID, Vals, VE);
1252       Vals.push_back(GetEncodedBinaryOpcode(I.getOpcode()));
1253       uint64_t Flags = GetOptimizationFlags(&I);
1254       if (Flags != 0) {
1255         if (AbbrevToUse == FUNCTION_INST_BINOP_ABBREV)
1256           AbbrevToUse = FUNCTION_INST_BINOP_FLAGS_ABBREV;
1257         Vals.push_back(Flags);
1258       }
1259     }
1260     break;
1261 
1262   case Instruction::GetElementPtr:
1263     Code = bitc::FUNC_CODE_INST_GEP;
1264     if (cast<GEPOperator>(&I)->isInBounds())
1265       Code = bitc::FUNC_CODE_INST_INBOUNDS_GEP;
1266     for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
1267       PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1268     break;
1269   case Instruction::ExtractValue: {
1270     Code = bitc::FUNC_CODE_INST_EXTRACTVAL;
1271     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1272     const ExtractValueInst *EVI = cast<ExtractValueInst>(&I);
1273     for (const unsigned *i = EVI->idx_begin(), *e = EVI->idx_end(); i != e; ++i)
1274       Vals.push_back(*i);
1275     break;
1276   }
1277   case Instruction::InsertValue: {
1278     Code = bitc::FUNC_CODE_INST_INSERTVAL;
1279     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1280     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1281     const InsertValueInst *IVI = cast<InsertValueInst>(&I);
1282     for (const unsigned *i = IVI->idx_begin(), *e = IVI->idx_end(); i != e; ++i)
1283       Vals.push_back(*i);
1284     break;
1285   }
1286   case Instruction::Select:
1287     Code = bitc::FUNC_CODE_INST_VSELECT;
1288     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1289     pushValue(I.getOperand(2), InstID, Vals, VE);
1290     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1291     break;
1292   case Instruction::ExtractElement:
1293     Code = bitc::FUNC_CODE_INST_EXTRACTELT;
1294     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1295     PushValueAndType(I.getOperand(1), InstID, Vals, VE);
1296     break;
1297   case Instruction::InsertElement:
1298     Code = bitc::FUNC_CODE_INST_INSERTELT;
1299     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1300     pushValue(I.getOperand(1), InstID, Vals, VE);
1301     PushValueAndType(I.getOperand(2), InstID, Vals, VE);
1302     break;
1303   case Instruction::ShuffleVector:
1304     Code = bitc::FUNC_CODE_INST_SHUFFLEVEC;
1305     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1306     pushValue(I.getOperand(1), InstID, Vals, VE);
1307     pushValue(I.getOperand(2), InstID, Vals, VE);
1308     break;
1309   case Instruction::ICmp:
1310   case Instruction::FCmp:
1311     // compare returning Int1Ty or vector of Int1Ty
1312     Code = bitc::FUNC_CODE_INST_CMP2;
1313     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1314     pushValue(I.getOperand(1), InstID, Vals, VE);
1315     Vals.push_back(cast<CmpInst>(I).getPredicate());
1316     break;
1317 
1318   case Instruction::Ret:
1319     {
1320       Code = bitc::FUNC_CODE_INST_RET;
1321       unsigned NumOperands = I.getNumOperands();
1322       if (NumOperands == 0)
1323         AbbrevToUse = FUNCTION_INST_RET_VOID_ABBREV;
1324       else if (NumOperands == 1) {
1325         if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))
1326           AbbrevToUse = FUNCTION_INST_RET_VAL_ABBREV;
1327       } else {
1328         for (unsigned i = 0, e = NumOperands; i != e; ++i)
1329           PushValueAndType(I.getOperand(i), InstID, Vals, VE);
1330       }
1331     }
1332     break;
1333   case Instruction::Br:
1334     {
1335       Code = bitc::FUNC_CODE_INST_BR;
1336       const BranchInst &II = cast<BranchInst>(I);
1337       Vals.push_back(VE.getValueID(II.getSuccessor(0)));
1338       if (II.isConditional()) {
1339         Vals.push_back(VE.getValueID(II.getSuccessor(1)));
1340         pushValue(II.getCondition(), InstID, Vals, VE);
1341       }
1342     }
1343     break;
1344   case Instruction::Switch:
1345     {
1346       Code = bitc::FUNC_CODE_INST_SWITCH;
1347       const SwitchInst &SI = cast<SwitchInst>(I);
1348       Vals.push_back(VE.getTypeID(SI.getCondition()->getType()));
1349       pushValue(SI.getCondition(), InstID, Vals, VE);
1350       Vals.push_back(VE.getValueID(SI.getDefaultDest()));
1351       for (SwitchInst::ConstCaseIt i = SI.case_begin(), e = SI.case_end();
1352            i != e; ++i) {
1353         Vals.push_back(VE.getValueID(i.getCaseValue()));
1354         Vals.push_back(VE.getValueID(i.getCaseSuccessor()));
1355       }
1356     }
1357     break;
1358   case Instruction::IndirectBr:
1359     Code = bitc::FUNC_CODE_INST_INDIRECTBR;
1360     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1361     // Encode the address operand as relative, but not the basic blocks.
1362     pushValue(I.getOperand(0), InstID, Vals, VE);
1363     for (unsigned i = 1, e = I.getNumOperands(); i != e; ++i)
1364       Vals.push_back(VE.getValueID(I.getOperand(i)));
1365     break;
1366 
1367   case Instruction::Invoke: {
1368     const InvokeInst *II = cast<InvokeInst>(&I);
1369     const Value *Callee(II->getCalledValue());
1370     PointerType *PTy = cast<PointerType>(Callee->getType());
1371     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1372     Code = bitc::FUNC_CODE_INST_INVOKE;
1373 
1374     Vals.push_back(VE.getAttributeID(II->getAttributes()));
1375     Vals.push_back(II->getCallingConv());
1376     Vals.push_back(VE.getValueID(II->getNormalDest()));
1377     Vals.push_back(VE.getValueID(II->getUnwindDest()));
1378     PushValueAndType(Callee, InstID, Vals, VE);
1379 
1380     // Emit value #'s for the fixed parameters.
1381     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
1382       pushValue(I.getOperand(i), InstID, Vals, VE);  // fixed param.
1383 
1384     // Emit type/value pairs for varargs params.
1385     if (FTy->isVarArg()) {
1386       for (unsigned i = FTy->getNumParams(), e = I.getNumOperands()-3;
1387            i != e; ++i)
1388         PushValueAndType(I.getOperand(i), InstID, Vals, VE); // vararg
1389     }
1390     break;
1391   }
1392   case Instruction::Resume:
1393     Code = bitc::FUNC_CODE_INST_RESUME;
1394     PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1395     break;
1396   case Instruction::Unreachable:
1397     Code = bitc::FUNC_CODE_INST_UNREACHABLE;
1398     AbbrevToUse = FUNCTION_INST_UNREACHABLE_ABBREV;
1399     break;
1400 
1401   case Instruction::PHI: {
1402     const PHINode &PN = cast<PHINode>(I);
1403     Code = bitc::FUNC_CODE_INST_PHI;
1404     // With the newer instruction encoding, forward references could give
1405     // negative valued IDs.  This is most common for PHIs, so we use
1406     // signed VBRs.
1407     SmallVector<uint64_t, 128> Vals64;
1408     Vals64.push_back(VE.getTypeID(PN.getType()));
1409     for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
1410       pushValueSigned(PN.getIncomingValue(i), InstID, Vals64, VE);
1411       Vals64.push_back(VE.getValueID(PN.getIncomingBlock(i)));
1412     }
1413     // Emit a Vals64 vector and exit.
1414     Stream.EmitRecord(Code, Vals64, AbbrevToUse);
1415     Vals64.clear();
1416     return;
1417   }
1418 
1419   case Instruction::LandingPad: {
1420     const LandingPadInst &LP = cast<LandingPadInst>(I);
1421     Code = bitc::FUNC_CODE_INST_LANDINGPAD;
1422     Vals.push_back(VE.getTypeID(LP.getType()));
1423     PushValueAndType(LP.getPersonalityFn(), InstID, Vals, VE);
1424     Vals.push_back(LP.isCleanup());
1425     Vals.push_back(LP.getNumClauses());
1426     for (unsigned I = 0, E = LP.getNumClauses(); I != E; ++I) {
1427       if (LP.isCatch(I))
1428         Vals.push_back(LandingPadInst::Catch);
1429       else
1430         Vals.push_back(LandingPadInst::Filter);
1431       PushValueAndType(LP.getClause(I), InstID, Vals, VE);
1432     }
1433     break;
1434   }
1435 
1436   case Instruction::Alloca: {
1437     Code = bitc::FUNC_CODE_INST_ALLOCA;
1438     Vals.push_back(VE.getTypeID(I.getType()));
1439     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));
1440     Vals.push_back(VE.getValueID(I.getOperand(0))); // size.
1441     const AllocaInst &AI = cast<AllocaInst>(I);
1442     unsigned AlignRecord = Log2_32(AI.getAlignment()) + 1;
1443     assert(Log2_32(Value::MaximumAlignment) + 1 < 1 << 5 &&
1444            "not enough bits for maximum alignment");
1445     assert(AlignRecord < 1 << 5 && "alignment greater than 1 << 64");
1446     AlignRecord |= AI.isUsedWithInAlloca() << 5;
1447     Vals.push_back(AlignRecord);
1448     break;
1449   }
1450 
1451   case Instruction::Load:
1452     if (cast<LoadInst>(I).isAtomic()) {
1453       Code = bitc::FUNC_CODE_INST_LOADATOMIC;
1454       PushValueAndType(I.getOperand(0), InstID, Vals, VE);
1455     } else {
1456       Code = bitc::FUNC_CODE_INST_LOAD;
1457       if (!PushValueAndType(I.getOperand(0), InstID, Vals, VE))  // ptr
1458         AbbrevToUse = FUNCTION_INST_LOAD_ABBREV;
1459     }
1460     Vals.push_back(Log2_32(cast<LoadInst>(I).getAlignment())+1);
1461     Vals.push_back(cast<LoadInst>(I).isVolatile());
1462     if (cast<LoadInst>(I).isAtomic()) {
1463       Vals.push_back(GetEncodedOrdering(cast<LoadInst>(I).getOrdering()));
1464       Vals.push_back(GetEncodedSynchScope(cast<LoadInst>(I).getSynchScope()));
1465     }
1466     break;
1467   case Instruction::Store:
1468     if (cast<StoreInst>(I).isAtomic())
1469       Code = bitc::FUNC_CODE_INST_STOREATOMIC;
1470     else
1471       Code = bitc::FUNC_CODE_INST_STORE;
1472     PushValueAndType(I.getOperand(1), InstID, Vals, VE);  // ptrty + ptr
1473     pushValue(I.getOperand(0), InstID, Vals, VE);         // val.
1474     Vals.push_back(Log2_32(cast<StoreInst>(I).getAlignment())+1);
1475     Vals.push_back(cast<StoreInst>(I).isVolatile());
1476     if (cast<StoreInst>(I).isAtomic()) {
1477       Vals.push_back(GetEncodedOrdering(cast<StoreInst>(I).getOrdering()));
1478       Vals.push_back(GetEncodedSynchScope(cast<StoreInst>(I).getSynchScope()));
1479     }
1480     break;
1481   case Instruction::AtomicCmpXchg:
1482     Code = bitc::FUNC_CODE_INST_CMPXCHG;
1483     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1484     pushValue(I.getOperand(1), InstID, Vals, VE);         // cmp.
1485     pushValue(I.getOperand(2), InstID, Vals, VE);         // newval.
1486     Vals.push_back(cast<AtomicCmpXchgInst>(I).isVolatile());
1487     Vals.push_back(GetEncodedOrdering(
1488                      cast<AtomicCmpXchgInst>(I).getSuccessOrdering()));
1489     Vals.push_back(GetEncodedSynchScope(
1490                      cast<AtomicCmpXchgInst>(I).getSynchScope()));
1491     Vals.push_back(GetEncodedOrdering(
1492                      cast<AtomicCmpXchgInst>(I).getFailureOrdering()));
1493     Vals.push_back(cast<AtomicCmpXchgInst>(I).isWeak());
1494     break;
1495   case Instruction::AtomicRMW:
1496     Code = bitc::FUNC_CODE_INST_ATOMICRMW;
1497     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
1498     pushValue(I.getOperand(1), InstID, Vals, VE);         // val.
1499     Vals.push_back(GetEncodedRMWOperation(
1500                      cast<AtomicRMWInst>(I).getOperation()));
1501     Vals.push_back(cast<AtomicRMWInst>(I).isVolatile());
1502     Vals.push_back(GetEncodedOrdering(cast<AtomicRMWInst>(I).getOrdering()));
1503     Vals.push_back(GetEncodedSynchScope(
1504                      cast<AtomicRMWInst>(I).getSynchScope()));
1505     break;
1506   case Instruction::Fence:
1507     Code = bitc::FUNC_CODE_INST_FENCE;
1508     Vals.push_back(GetEncodedOrdering(cast<FenceInst>(I).getOrdering()));
1509     Vals.push_back(GetEncodedSynchScope(cast<FenceInst>(I).getSynchScope()));
1510     break;
1511   case Instruction::Call: {
1512     const CallInst &CI = cast<CallInst>(I);
1513     PointerType *PTy = cast<PointerType>(CI.getCalledValue()->getType());
1514     FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1515 
1516     Code = bitc::FUNC_CODE_INST_CALL;
1517 
1518     Vals.push_back(VE.getAttributeID(CI.getAttributes()));
1519     Vals.push_back((CI.getCallingConv() << 1) | unsigned(CI.isTailCall()) |
1520                    unsigned(CI.isMustTailCall()) << 14);
1521     PushValueAndType(CI.getCalledValue(), InstID, Vals, VE);  // Callee
1522 
1523     // Emit value #'s for the fixed parameters.
1524     for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) {
1525       // Check for labels (can happen with asm labels).
1526       if (FTy->getParamType(i)->isLabelTy())
1527         Vals.push_back(VE.getValueID(CI.getArgOperand(i)));
1528       else
1529         pushValue(CI.getArgOperand(i), InstID, Vals, VE);  // fixed param.
1530     }
1531 
1532     // Emit type/value pairs for varargs params.
1533     if (FTy->isVarArg()) {
1534       for (unsigned i = FTy->getNumParams(), e = CI.getNumArgOperands();
1535            i != e; ++i)
1536         PushValueAndType(CI.getArgOperand(i), InstID, Vals, VE);  // varargs
1537     }
1538     break;
1539   }
1540   case Instruction::VAArg:
1541     Code = bitc::FUNC_CODE_INST_VAARG;
1542     Vals.push_back(VE.getTypeID(I.getOperand(0)->getType()));   // valistty
1543     pushValue(I.getOperand(0), InstID, Vals, VE); // valist.
1544     Vals.push_back(VE.getTypeID(I.getType())); // restype.
1545     break;
1546   }
1547 
1548   Stream.EmitRecord(Code, Vals, AbbrevToUse);
1549   Vals.clear();
1550 }
1551 
1552 // Emit names for globals/functions etc.
1553 static void WriteValueSymbolTable(const ValueSymbolTable &VST,
1554                                   const ValueEnumerator &VE,
1555                                   BitstreamWriter &Stream) {
1556   if (VST.empty()) return;
1557   Stream.EnterSubblock(bitc::VALUE_SYMTAB_BLOCK_ID, 4);
1558 
1559   // FIXME: Set up the abbrev, we know how many values there are!
1560   // FIXME: We know if the type names can use 7-bit ascii.
1561   SmallVector<unsigned, 64> NameVals;
1562 
1563   for (ValueSymbolTable::const_iterator SI = VST.begin(), SE = VST.end();
1564        SI != SE; ++SI) {
1565 
1566     const ValueName &Name = *SI;
1567 
1568     // Figure out the encoding to use for the name.
1569     bool is7Bit = true;
1570     bool isChar6 = true;
1571     for (const char *C = Name.getKeyData(), *E = C+Name.getKeyLength();
1572          C != E; ++C) {
1573       if (isChar6)
1574         isChar6 = BitCodeAbbrevOp::isChar6(*C);
1575       if ((unsigned char)*C & 128) {
1576         is7Bit = false;
1577         break;  // don't bother scanning the rest.
1578       }
1579     }
1580 
1581     unsigned AbbrevToUse = VST_ENTRY_8_ABBREV;
1582 
1583     // VST_ENTRY:   [valueid, namechar x N]
1584     // VST_BBENTRY: [bbid, namechar x N]
1585     unsigned Code;
1586     if (isa<BasicBlock>(SI->getValue())) {
1587       Code = bitc::VST_CODE_BBENTRY;
1588       if (isChar6)
1589         AbbrevToUse = VST_BBENTRY_6_ABBREV;
1590     } else {
1591       Code = bitc::VST_CODE_ENTRY;
1592       if (isChar6)
1593         AbbrevToUse = VST_ENTRY_6_ABBREV;
1594       else if (is7Bit)
1595         AbbrevToUse = VST_ENTRY_7_ABBREV;
1596     }
1597 
1598     NameVals.push_back(VE.getValueID(SI->getValue()));
1599     for (const char *P = Name.getKeyData(),
1600          *E = Name.getKeyData()+Name.getKeyLength(); P != E; ++P)
1601       NameVals.push_back((unsigned char)*P);
1602 
1603     // Emit the finished record.
1604     Stream.EmitRecord(Code, NameVals, AbbrevToUse);
1605     NameVals.clear();
1606   }
1607   Stream.ExitBlock();
1608 }
1609 
1610 /// WriteFunction - Emit a function body to the module stream.
1611 static void WriteFunction(const Function &F, ValueEnumerator &VE,
1612                           BitstreamWriter &Stream) {
1613   Stream.EnterSubblock(bitc::FUNCTION_BLOCK_ID, 4);
1614   VE.incorporateFunction(F);
1615 
1616   SmallVector<unsigned, 64> Vals;
1617 
1618   // Emit the number of basic blocks, so the reader can create them ahead of
1619   // time.
1620   Vals.push_back(VE.getBasicBlocks().size());
1621   Stream.EmitRecord(bitc::FUNC_CODE_DECLAREBLOCKS, Vals);
1622   Vals.clear();
1623 
1624   // If there are function-local constants, emit them now.
1625   unsigned CstStart, CstEnd;
1626   VE.getFunctionConstantRange(CstStart, CstEnd);
1627   WriteConstants(CstStart, CstEnd, VE, Stream, false);
1628 
1629   // If there is function-local metadata, emit it now.
1630   WriteFunctionLocalMetadata(F, VE, Stream);
1631 
1632   // Keep a running idea of what the instruction ID is.
1633   unsigned InstID = CstEnd;
1634 
1635   bool NeedsMetadataAttachment = false;
1636 
1637   DebugLoc LastDL;
1638 
1639   // Finally, emit all the instructions, in order.
1640   for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
1641     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
1642          I != E; ++I) {
1643       WriteInstruction(*I, InstID, VE, Stream, Vals);
1644 
1645       if (!I->getType()->isVoidTy())
1646         ++InstID;
1647 
1648       // If the instruction has metadata, write a metadata attachment later.
1649       NeedsMetadataAttachment |= I->hasMetadataOtherThanDebugLoc();
1650 
1651       // If the instruction has a debug location, emit it.
1652       DebugLoc DL = I->getDebugLoc();
1653       if (DL.isUnknown()) {
1654         // nothing todo.
1655       } else if (DL == LastDL) {
1656         // Just repeat the same debug loc as last time.
1657         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC_AGAIN, Vals);
1658       } else {
1659         MDNode *Scope, *IA;
1660         DL.getScopeAndInlinedAt(Scope, IA, I->getContext());
1661 
1662         Vals.push_back(DL.getLine());
1663         Vals.push_back(DL.getCol());
1664         Vals.push_back(Scope ? VE.getValueID(Scope)+1 : 0);
1665         Vals.push_back(IA ? VE.getValueID(IA)+1 : 0);
1666         Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
1667         Vals.clear();
1668 
1669         LastDL = DL;
1670       }
1671     }
1672 
1673   // Emit names for all the instructions etc.
1674   WriteValueSymbolTable(F.getValueSymbolTable(), VE, Stream);
1675 
1676   if (NeedsMetadataAttachment)
1677     WriteMetadataAttachment(F, VE, Stream);
1678   VE.purgeFunction();
1679   Stream.ExitBlock();
1680 }
1681 
1682 // Emit blockinfo, which defines the standard abbreviations etc.
1683 static void WriteBlockInfo(const ValueEnumerator &VE, BitstreamWriter &Stream) {
1684   // We only want to emit block info records for blocks that have multiple
1685   // instances: CONSTANTS_BLOCK, FUNCTION_BLOCK and VALUE_SYMTAB_BLOCK.
1686   // Other blocks can define their abbrevs inline.
1687   Stream.EnterBlockInfoBlock(2);
1688 
1689   { // 8-bit fixed-width VST_ENTRY/VST_BBENTRY strings.
1690     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1691     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3));
1692     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1693     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1694     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
1695     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1696                                    Abbv) != VST_ENTRY_8_ABBREV)
1697       llvm_unreachable("Unexpected abbrev ordering!");
1698   }
1699 
1700   { // 7-bit fixed width VST_ENTRY strings.
1701     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1702     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1703     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1704     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1705     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7));
1706     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1707                                    Abbv) != VST_ENTRY_7_ABBREV)
1708       llvm_unreachable("Unexpected abbrev ordering!");
1709   }
1710   { // 6-bit char6 VST_ENTRY strings.
1711     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1712     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_ENTRY));
1713     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1714     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1715     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1716     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1717                                    Abbv) != VST_ENTRY_6_ABBREV)
1718       llvm_unreachable("Unexpected abbrev ordering!");
1719   }
1720   { // 6-bit char6 VST_BBENTRY strings.
1721     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1722     Abbv->Add(BitCodeAbbrevOp(bitc::VST_CODE_BBENTRY));
1723     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1724     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
1725     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
1726     if (Stream.EmitBlockInfoAbbrev(bitc::VALUE_SYMTAB_BLOCK_ID,
1727                                    Abbv) != VST_BBENTRY_6_ABBREV)
1728       llvm_unreachable("Unexpected abbrev ordering!");
1729   }
1730 
1731 
1732 
1733   { // SETTYPE abbrev for CONSTANTS_BLOCK.
1734     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1735     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_SETTYPE));
1736     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
1737                               Log2_32_Ceil(VE.getTypes().size()+1)));
1738     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1739                                    Abbv) != CONSTANTS_SETTYPE_ABBREV)
1740       llvm_unreachable("Unexpected abbrev ordering!");
1741   }
1742 
1743   { // INTEGER abbrev for CONSTANTS_BLOCK.
1744     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1745     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_INTEGER));
1746     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
1747     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1748                                    Abbv) != CONSTANTS_INTEGER_ABBREV)
1749       llvm_unreachable("Unexpected abbrev ordering!");
1750   }
1751 
1752   { // CE_CAST abbrev for CONSTANTS_BLOCK.
1753     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1754     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_CE_CAST));
1755     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // cast opc
1756     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // typeid
1757                               Log2_32_Ceil(VE.getTypes().size()+1)));
1758     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));    // value id
1759 
1760     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1761                                    Abbv) != CONSTANTS_CE_CAST_Abbrev)
1762       llvm_unreachable("Unexpected abbrev ordering!");
1763   }
1764   { // NULL abbrev for CONSTANTS_BLOCK.
1765     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1766     Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_NULL));
1767     if (Stream.EmitBlockInfoAbbrev(bitc::CONSTANTS_BLOCK_ID,
1768                                    Abbv) != CONSTANTS_NULL_Abbrev)
1769       llvm_unreachable("Unexpected abbrev ordering!");
1770   }
1771 
1772   // FIXME: This should only use space for first class types!
1773 
1774   { // INST_LOAD abbrev for FUNCTION_BLOCK.
1775     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1776     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_LOAD));
1777     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // Ptr
1778     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // Align
1779     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // volatile
1780     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1781                                    Abbv) != FUNCTION_INST_LOAD_ABBREV)
1782       llvm_unreachable("Unexpected abbrev ordering!");
1783   }
1784   { // INST_BINOP abbrev for FUNCTION_BLOCK.
1785     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1786     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1787     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1788     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1789     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1790     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1791                                    Abbv) != FUNCTION_INST_BINOP_ABBREV)
1792       llvm_unreachable("Unexpected abbrev ordering!");
1793   }
1794   { // INST_BINOP_FLAGS abbrev for FUNCTION_BLOCK.
1795     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1796     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_BINOP));
1797     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // LHS
1798     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // RHS
1799     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4)); // opc
1800     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 7)); // flags
1801     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1802                                    Abbv) != FUNCTION_INST_BINOP_FLAGS_ABBREV)
1803       llvm_unreachable("Unexpected abbrev ordering!");
1804   }
1805   { // INST_CAST abbrev for FUNCTION_BLOCK.
1806     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1807     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_CAST));
1808     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));    // OpVal
1809     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,       // dest ty
1810                               Log2_32_Ceil(VE.getTypes().size()+1)));
1811     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 4));  // opc
1812     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1813                                    Abbv) != FUNCTION_INST_CAST_ABBREV)
1814       llvm_unreachable("Unexpected abbrev ordering!");
1815   }
1816 
1817   { // INST_RET abbrev for FUNCTION_BLOCK.
1818     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1819     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1820     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1821                                    Abbv) != FUNCTION_INST_RET_VOID_ABBREV)
1822       llvm_unreachable("Unexpected abbrev ordering!");
1823   }
1824   { // INST_RET abbrev for FUNCTION_BLOCK.
1825     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1826     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_RET));
1827     Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // ValID
1828     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1829                                    Abbv) != FUNCTION_INST_RET_VAL_ABBREV)
1830       llvm_unreachable("Unexpected abbrev ordering!");
1831   }
1832   { // INST_UNREACHABLE abbrev for FUNCTION_BLOCK.
1833     BitCodeAbbrev *Abbv = new BitCodeAbbrev();
1834     Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_INST_UNREACHABLE));
1835     if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID,
1836                                    Abbv) != FUNCTION_INST_UNREACHABLE_ABBREV)
1837       llvm_unreachable("Unexpected abbrev ordering!");
1838   }
1839 
1840   Stream.ExitBlock();
1841 }
1842 
1843 // Sort the Users based on the order in which the reader parses the bitcode
1844 // file.
1845 static bool bitcodereader_order(const User *lhs, const User *rhs) {
1846   // TODO: Implement.
1847   return true;
1848 }
1849 
1850 static void WriteUseList(const Value *V, const ValueEnumerator &VE,
1851                          BitstreamWriter &Stream) {
1852 
1853   // One or zero uses can't get out of order.
1854   if (V->use_empty() || V->hasNUses(1))
1855     return;
1856 
1857   // Make a copy of the in-memory use-list for sorting.
1858   SmallVector<const User*, 8> UserList(V->user_begin(), V->user_end());
1859 
1860   // Sort the copy based on the order read by the BitcodeReader.
1861   std::sort(UserList.begin(), UserList.end(), bitcodereader_order);
1862 
1863   // TODO: Generate a diff between the BitcodeWriter in-memory use-list and the
1864   // sorted list (i.e., the expected BitcodeReader in-memory use-list).
1865 
1866   // TODO: Emit the USELIST_CODE_ENTRYs.
1867 }
1868 
1869 static void WriteFunctionUseList(const Function *F, ValueEnumerator &VE,
1870                                  BitstreamWriter &Stream) {
1871   VE.incorporateFunction(*F);
1872 
1873   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
1874        AI != AE; ++AI)
1875     WriteUseList(AI, VE, Stream);
1876   for (Function::const_iterator BB = F->begin(), FE = F->end(); BB != FE;
1877        ++BB) {
1878     WriteUseList(BB, VE, Stream);
1879     for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); II != IE;
1880          ++II) {
1881       WriteUseList(II, VE, Stream);
1882       for (User::const_op_iterator OI = II->op_begin(), E = II->op_end();
1883            OI != E; ++OI) {
1884         if ((isa<Constant>(*OI) && !isa<GlobalValue>(*OI)) ||
1885             isa<InlineAsm>(*OI))
1886           WriteUseList(*OI, VE, Stream);
1887       }
1888     }
1889   }
1890   VE.purgeFunction();
1891 }
1892 
1893 // Emit use-lists.
1894 static void WriteModuleUseLists(const Module *M, ValueEnumerator &VE,
1895                                 BitstreamWriter &Stream) {
1896   Stream.EnterSubblock(bitc::USELIST_BLOCK_ID, 3);
1897 
1898   // XXX: this modifies the module, but in a way that should never change the
1899   // behavior of any pass or codegen in LLVM. The problem is that GVs may
1900   // contain entries in the use_list that do not exist in the Module and are
1901   // not stored in the .bc file.
1902   for (Module::const_global_iterator I = M->global_begin(), E = M->global_end();
1903        I != E; ++I)
1904     I->removeDeadConstantUsers();
1905 
1906   // Write the global variables.
1907   for (Module::const_global_iterator GI = M->global_begin(),
1908          GE = M->global_end(); GI != GE; ++GI) {
1909     WriteUseList(GI, VE, Stream);
1910 
1911     // Write the global variable initializers.
1912     if (GI->hasInitializer())
1913       WriteUseList(GI->getInitializer(), VE, Stream);
1914   }
1915 
1916   // Write the functions.
1917   for (Module::const_iterator FI = M->begin(), FE = M->end(); FI != FE; ++FI) {
1918     WriteUseList(FI, VE, Stream);
1919     if (!FI->isDeclaration())
1920       WriteFunctionUseList(FI, VE, Stream);
1921     if (FI->hasPrefixData())
1922       WriteUseList(FI->getPrefixData(), VE, Stream);
1923   }
1924 
1925   // Write the aliases.
1926   for (Module::const_alias_iterator AI = M->alias_begin(), AE = M->alias_end();
1927        AI != AE; ++AI) {
1928     WriteUseList(AI, VE, Stream);
1929     WriteUseList(AI->getAliasee(), VE, Stream);
1930   }
1931 
1932   Stream.ExitBlock();
1933 }
1934 
1935 /// WriteModule - Emit the specified module to the bitstream.
1936 static void WriteModule(const Module *M, BitstreamWriter &Stream) {
1937   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
1938 
1939   SmallVector<unsigned, 1> Vals;
1940   unsigned CurVersion = 1;
1941   Vals.push_back(CurVersion);
1942   Stream.EmitRecord(bitc::MODULE_CODE_VERSION, Vals);
1943 
1944   // Analyze the module, enumerating globals, functions, etc.
1945   ValueEnumerator VE(M);
1946 
1947   // Emit blockinfo, which defines the standard abbreviations etc.
1948   WriteBlockInfo(VE, Stream);
1949 
1950   // Emit information about attribute groups.
1951   WriteAttributeGroupTable(VE, Stream);
1952 
1953   // Emit information about parameter attributes.
1954   WriteAttributeTable(VE, Stream);
1955 
1956   // Emit information describing all of the types in the module.
1957   WriteTypeTable(VE, Stream);
1958 
1959   writeComdats(VE, Stream);
1960 
1961   // Emit top-level description of module, including target triple, inline asm,
1962   // descriptors for global variables, and function prototype info.
1963   WriteModuleInfo(M, VE, Stream);
1964 
1965   // Emit constants.
1966   WriteModuleConstants(VE, Stream);
1967 
1968   // Emit metadata.
1969   WriteModuleMetadata(M, VE, Stream);
1970 
1971   // Emit metadata.
1972   WriteModuleMetadataStore(M, Stream);
1973 
1974   // Emit names for globals/functions etc.
1975   WriteValueSymbolTable(M->getValueSymbolTable(), VE, Stream);
1976 
1977   // Emit use-lists.
1978   if (EnablePreserveUseListOrdering)
1979     WriteModuleUseLists(M, VE, Stream);
1980 
1981   // Emit function bodies.
1982   for (Module::const_iterator F = M->begin(), E = M->end(); F != E; ++F)
1983     if (!F->isDeclaration())
1984       WriteFunction(*F, VE, Stream);
1985 
1986   Stream.ExitBlock();
1987 }
1988 
1989 /// EmitDarwinBCHeader - If generating a bc file on darwin, we have to emit a
1990 /// header and trailer to make it compatible with the system archiver.  To do
1991 /// this we emit the following header, and then emit a trailer that pads the
1992 /// file out to be a multiple of 16 bytes.
1993 ///
1994 /// struct bc_header {
1995 ///   uint32_t Magic;         // 0x0B17C0DE
1996 ///   uint32_t Version;       // Version, currently always 0.
1997 ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
1998 ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
1999 ///   uint32_t CPUType;       // CPU specifier.
2000 ///   ... potentially more later ...
2001 /// };
2002 enum {
2003   DarwinBCSizeFieldOffset = 3*4, // Offset to bitcode_size.
2004   DarwinBCHeaderSize = 5*4
2005 };
2006 
2007 static void WriteInt32ToBuffer(uint32_t Value, SmallVectorImpl<char> &Buffer,
2008                                uint32_t &Position) {
2009   Buffer[Position + 0] = (unsigned char) (Value >>  0);
2010   Buffer[Position + 1] = (unsigned char) (Value >>  8);
2011   Buffer[Position + 2] = (unsigned char) (Value >> 16);
2012   Buffer[Position + 3] = (unsigned char) (Value >> 24);
2013   Position += 4;
2014 }
2015 
2016 static void EmitDarwinBCHeaderAndTrailer(SmallVectorImpl<char> &Buffer,
2017                                          const Triple &TT) {
2018   unsigned CPUType = ~0U;
2019 
2020   // Match x86_64-*, i[3-9]86-*, powerpc-*, powerpc64-*, arm-*, thumb-*,
2021   // armv[0-9]-*, thumbv[0-9]-*, armv5te-*, or armv6t2-*. The CPUType is a magic
2022   // number from /usr/include/mach/machine.h.  It is ok to reproduce the
2023   // specific constants here because they are implicitly part of the Darwin ABI.
2024   enum {
2025     DARWIN_CPU_ARCH_ABI64      = 0x01000000,
2026     DARWIN_CPU_TYPE_X86        = 7,
2027     DARWIN_CPU_TYPE_ARM        = 12,
2028     DARWIN_CPU_TYPE_POWERPC    = 18
2029   };
2030 
2031   Triple::ArchType Arch = TT.getArch();
2032   if (Arch == Triple::x86_64)
2033     CPUType = DARWIN_CPU_TYPE_X86 | DARWIN_CPU_ARCH_ABI64;
2034   else if (Arch == Triple::x86)
2035     CPUType = DARWIN_CPU_TYPE_X86;
2036   else if (Arch == Triple::ppc)
2037     CPUType = DARWIN_CPU_TYPE_POWERPC;
2038   else if (Arch == Triple::ppc64)
2039     CPUType = DARWIN_CPU_TYPE_POWERPC | DARWIN_CPU_ARCH_ABI64;
2040   else if (Arch == Triple::arm || Arch == Triple::thumb)
2041     CPUType = DARWIN_CPU_TYPE_ARM;
2042 
2043   // Traditional Bitcode starts after header.
2044   assert(Buffer.size() >= DarwinBCHeaderSize &&
2045          "Expected header size to be reserved");
2046   unsigned BCOffset = DarwinBCHeaderSize;
2047   unsigned BCSize = Buffer.size()-DarwinBCHeaderSize;
2048 
2049   // Write the magic and version.
2050   unsigned Position = 0;
2051   WriteInt32ToBuffer(0x0B17C0DE , Buffer, Position);
2052   WriteInt32ToBuffer(0          , Buffer, Position); // Version.
2053   WriteInt32ToBuffer(BCOffset   , Buffer, Position);
2054   WriteInt32ToBuffer(BCSize     , Buffer, Position);
2055   WriteInt32ToBuffer(CPUType    , Buffer, Position);
2056 
2057   // If the file is not a multiple of 16 bytes, insert dummy padding.
2058   while (Buffer.size() & 15)
2059     Buffer.push_back(0);
2060 }
2061 
2062 /// WriteBitcodeToFile - Write the specified module to the specified output
2063 /// stream.
2064 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out) {
2065   SmallVector<char, 0> Buffer;
2066   Buffer.reserve(256*1024);
2067 
2068   // If this is darwin or another generic macho target, reserve space for the
2069   // header.
2070   Triple TT(M->getTargetTriple());
2071   if (TT.isOSDarwin())
2072     Buffer.insert(Buffer.begin(), DarwinBCHeaderSize, 0);
2073 
2074   // Emit the module into the buffer.
2075   {
2076     BitstreamWriter Stream(Buffer);
2077 
2078     // Emit the file header.
2079     Stream.Emit((unsigned)'B', 8);
2080     Stream.Emit((unsigned)'C', 8);
2081     Stream.Emit(0x0, 4);
2082     Stream.Emit(0xC, 4);
2083     Stream.Emit(0xE, 4);
2084     Stream.Emit(0xD, 4);
2085 
2086     // Emit the module.
2087     WriteModule(M, Stream);
2088   }
2089 
2090   if (TT.isOSDarwin())
2091     EmitDarwinBCHeaderAndTrailer(Buffer, TT);
2092 
2093   // Write the generated bitstream to "Out".
2094   Out.write((char*)&Buffer.front(), Buffer.size());
2095 }
2096