BitcodeWriter.cpp

//===--- Bitcode/Writer/BitcodeWriter.cpp - Bitcode Writer ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Bitcode writer implementation.
//
//===----------------------------------------------------------------------===//

#include "llvm/Bitcode/ReaderWriter.h"
#include "ValueEnumerator.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Bitcode/BitstreamWriter.h"
#include "llvm/Bitcode/LLVMBitCodes.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/UseListOrder.h"
#include "llvm/IR/ValueSymbolTable.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/raw_ostream.h"
#include <cctype>
#include <map>
using namespace llvm;

/// These are manifest constants used by the bitcode writer. They do not need to
/// be kept in sync with the reader, but need to be consistent within this file.
enum {
  // VALUE_SYMTAB_BLOCK abbrev id's.
  VST_ENTRY_8_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  VST_ENTRY_7_ABBREV,
  VST_ENTRY_6_ABBREV,
  VST_BBENTRY_6_ABBREV,

  // CONSTANTS_BLOCK abbrev id's.
  CONSTANTS_SETTYPE_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  CONSTANTS_INTEGER_ABBREV,
  CONSTANTS_CE_CAST_Abbrev,
  CONSTANTS_NULL_Abbrev,

  // FUNCTION_BLOCK abbrev id's.
  FUNCTION_INST_LOAD_ABBREV = bitc::FIRST_APPLICATION_ABBREV,
  FUNCTION_INST_BINOP_ABBREV,
  FUNCTION_INST_BINOP_FLAGS_ABBREV,
  FUNCTION_INST_CAST_ABBREV,
  FUNCTION_INST_RET_VOID_ABBREV,
  FUNCTION_INST_RET_VAL_ABBREV,
  FUNCTION_INST_UNREACHABLE_ABBREV
};

static unsigned GetEncodedCastOpcode(unsigned Opcode) {
  switch (Opcode) {
  default: llvm_unreachable("Unknown cast instruction!");
  case Instruction::Trunc   : return bitc::CAST_TRUNC;
  case Instruction::ZExt    : return bitc::CAST_ZEXT;
  case Instruction::SExt    : return bitc::CAST_SEXT;
  case Instruction::FPToUI  : return bitc::CAST_FPTOUI;
  case Instruction::FPToSI  : return bitc::CAST_FPTOSI;
  case Instruction::UIToFP  : return bitc::CAST_UITOFP;
  case Instruction::SIToFP  : return bitc::CAST_SITOFP;
  case Instruction::FPTrunc : return bitc::CAST_FPTRUNC;
  case Instruction::FPExt   : return bitc::CAST_FPEXT;
  case Instruction::PtrToInt: return bitc::CAST_PTRTOINT;
  case Instruction::IntToPtr: return bitc::CAST_INTTOPTR;
  case Instruction::BitCast : return bitc::CAST_BITCAST;
  case Instruction::AddrSpaceCast: return bitc::CAST_ADDRSPACECAST;
  }
}

static unsigned GetEncodedBinaryOpcode(unsigned Opcode) {
  switch (Opcode) {
  default: llvm_unreachable("Unknown binary instruction!");
  case Instruction::Add:
  case Instruction::FAdd: return bitc::BINOP_ADD;
  case Instruction::Sub:
  case Instruction::FSub: return bitc::BINOP_SUB;
  case Instruction::Mul:
  case Instruction::FMul: return bitc::BINOP_MUL;
  case Instruction::UDiv: return bitc::BINOP_UDIV;
  case Instruction::FDiv:
  case Instruction::SDiv: return bitc::BINOP_SDIV;
  case Instruction::URem: return bitc::BINOP_UREM;
  case Instruction::FRem:
  case Instruction::SRem: return bitc::BINOP_SREM;
  case Instruction::Shl:  return bitc::BINOP_SHL;
  case Instruction::LShr: return bitc::BINOP_LSHR;
  case Instruction::AShr: return bitc::BINOP_ASHR;
  case Instruction::And:  return bitc::BINOP_AND;
  case Instruction::Or:   return bitc::BINOP_OR;
  case Instruction::Xor:  return bitc::BINOP_XOR;
  }
}

static unsigned GetEncodedRMWOperation(AtomicRMWInst::BinOp Op) {
  switch (Op) {
  default: llvm_unreachable("Unknown RMW operation!");
  case AtomicRMWInst::Xchg: return bitc::RMW_XCHG;
  case AtomicRMWInst::Add: return bitc::RMW_ADD;
  case AtomicRMWInst::Sub: return bitc::RMW_SUB;
  case AtomicRMWInst::And: return bitc::RMW_AND;
  case AtomicRMWInst::Nand: return bitc::RMW_NAND;
  case AtomicRMWInst::Or: return bitc::RMW_OR;
  case AtomicRMWInst::Xor: return bitc::RMW_XOR;
  case AtomicRMWInst::Max: return bitc::RMW_MAX;
  case AtomicRMWInst::Min: return bitc::RMW_MIN;
  case AtomicRMWInst::UMax: return bitc::RMW_UMAX;
  case AtomicRMWInst::UMin: return bitc::RMW_UMIN;
  }
}

static unsigned GetEncodedOrdering(AtomicOrdering Ordering) {
  switch (Ordering) {
  case NotAtomic: return bitc::ORDERING_NOTATOMIC;
  case Unordered: return bitc::ORDERING_UNORDERED;
  case Monotonic: return bitc::ORDERING_MONOTONIC;
  case Acquire: return bitc::ORDERING_ACQUIRE;
  case Release: return bitc::ORDERING_RELEASE;
  case AcquireRelease: return bitc::ORDERING_ACQREL;
  case SequentiallyConsistent: return bitc::ORDERING_SEQCST;
  }
  llvm_unreachable("Invalid ordering");
}

static unsigned GetEncodedSynchScope(SynchronizationScope SynchScope) {
  switch (SynchScope) {
  case SingleThread: return bitc::SYNCHSCOPE_SINGLETHREAD;
  case CrossThread: return bitc::SYNCHSCOPE_CROSSTHREAD;
  }
  llvm_unreachable("Invalid synch scope");
}

static void WriteStringRecord(unsigned Code, StringRef Str,
                              unsigned AbbrevToUse, BitstreamWriter &Stream) {
  SmallVector<unsigned, 64> Vals;

  // Code: [strchar x N]
  for (unsigned i = 0, e = Str.size(); i != e; ++i) {
    if (AbbrevToUse && !BitCodeAbbrevOp::isChar6(Str[i]))
      AbbrevToUse = 0;
    Vals.push_back(Str[i]);
  }

  // Emit the finished record.
  Stream.EmitRecord(Code, Vals, AbbrevToUse);
}

static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
  switch (Kind) {
  case Attribute::Alignment:
    return bitc::ATTR_KIND_ALIGNMENT;
  case Attribute::AlwaysInline:
    return bitc::ATTR_KIND_ALWAYS_INLINE;
  case Attribute::Builtin:
    return bitc::ATTR_KIND_BUILTIN;
  case Attribute::ByVal:
    return bitc::ATTR_KIND_BY_VAL;
  case Attribute::InAlloca:
    return bitc::ATTR_KIND_IN_ALLOCA;
  case Attribute::Cold:
    return bitc::ATTR_KIND_COLD;
  case Attribute::InlineHint:
    return bitc::ATTR_KIND_INLINE_HINT;
  case Attribute::InReg:
    return bitc::ATTR_KIND_IN_REG;
  case Attribute::JumpTable:
    return bitc::ATTR_KIND_JUMP_TABLE;
  case Attribute::MinSize:
    return bitc::ATTR_KIND_MIN_SIZE;
  case Attribute::Naked:
    return bitc::ATTR_KIND_NAKED;
  case Attribute::Nest:
    return bitc::ATTR_KIND_NEST;
  case Attribute::NoAlias:
    return bitc::ATTR_KIND_NO_ALIAS;
  case Attribute::NoBuiltin:
    return bitc::ATTR_KIND_NO_BUILTIN;
  case Attribute::NoCapture:
    return bitc::ATTR_KIND_NO_CAPTURE;
  case Attribute::NoDuplicate:
    return bitc::ATTR_KIND_NO_DUPLICATE;
  case Attribute::NoImplicitFloat:
    return bitc::ATTR_KIND_NO_IMPLICIT_FLOAT;
  case Attribute::NoInline:
    return bitc::ATTR_KIND_NO_INLINE;
  case Attribute::NonLazyBind:
    return bitc::ATTR_KIND_NON_LAZY_BIND;
  case Attribute::NonNull:
    return bitc::ATTR_KIND_NON_NULL;
  case Attribute::Dereferenceable:
    return bitc::ATTR_KIND_DEREFERENCEABLE;
  case Attribute::NoRedZone:
    return bitc::ATTR_KIND_NO_RED_ZONE;
  case Attribute::NoReturn:
    return bitc::ATTR_KIND_NO_RETURN;
  case Attribute::NoUnwind:
    return bitc::ATTR_KIND_NO_UNWIND;
  case Attribute::OptimizeForSize:
    return bitc::ATTR_KIND_OPTIMIZE_FOR_SIZE;
  case Attribute::OptimizeNone:
    return bitc::ATTR_KIND_OPTIMIZE_NONE;
  case Attribute::ReadNone:
    return bitc::ATTR_KIND_READ_NONE;
  case Attribute::ReadOnly:
    return bitc::ATTR_KIND_READ_ONLY;
  case Attribute::Returned:
    return bitc::ATTR_KIND_RETURNED;
  case Attribute::ReturnsTwice:
    return bitc::ATTR_KIND_RETURNS_TWICE;
  case Attribute::SExt:
    return bitc::ATTR_KIND_S_EXT;
  case Attribute::StackAlignment:
    return bitc::ATTR_KIND_STACK_ALIGNMENT;
  case Attribute::StackProtect:
    return bitc::ATTR_KIND_STACK_PROTECT;
  case Attribute::StackProtectReq:
    return bitc::ATTR_KIND_STACK_PROTECT_REQ;
  case Attribute::StackProtectStrong:
    return bitc::ATTR_KIND_STACK_PROTECT_STRONG;
  case Attribute::StructRet:
    return bitc::ATTR_KIND_STRUCT_RET;
  case Attribute::SanitizeAddress:
    return bitc::ATTR_KIND_SANITIZE_ADDRESS;
  case Attribute::SanitizeThread:
    return bitc::ATTR_KIND_SANITIZE_THREAD;
  case Attribute::SanitizeMemory:
    return bitc::ATTR_KIND_SANITIZE_MEMORY;
  case Attribute::UWTable:
    return bitc::ATTR_KIND_UW_TABLE;
  case Attribute::ZExt:
    return bitc::ATTR_KIND_Z_EXT;
  case Attribute::EndAttrKinds:
    llvm_unreachable("Can not encode end-attribute kinds marker.");
  case Attribute::None:
    llvm_unreachable("Can not encode none-attribute.");
  }

  llvm_unreachable("Trying to encode unknown attribute");
}

static void WriteAttributeGroupTable(const ValueEnumerator &VE,
                                     BitstreamWriter &Stream) {
  const std::vector<AttributeSet> &AttrGrps = VE.getAttributeGroups();
  if (AttrGrps.empty()) return;

  Stream.EnterSubblock(bitc::PARAMATTR_GROUP_BLOCK_ID, 3);

  SmallVector<uint64_t, 64> Record;
  for (unsigned i = 0, e = AttrGrps.size(); i != e; ++i) {
    AttributeSet AS = AttrGrps[i];
    for (unsigned i = 0, e = AS.getNumSlots(); i != e; ++i) {
      AttributeSet A = AS.getSlotAttributes(i);

      Record.push_back(VE.getAttributeGroupID(A));
      Record.push_back(AS.getSlotIndex(i));

      for (AttributeSet::iterator I = AS.begin(0), E = AS.end(0);
           I != E; ++I) {
        Attribute Attr = *I;
        if (Attr.isEnumAttribute()) {
          Record.push_back(0);
          Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
        } else if (Attr.isIntAttribute()) {
          Record.push_back(1);
          Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
          Record.push_back(Attr.getValueAsInt());
        } else {
          StringRef Kind = Attr.getKindAsString();
          StringRef Val = Attr.getValueAsString();

          Record.push_back(Val.empty() ? 3 : 4);
          Record.append(Kind.begin(), Kind.end());
          Record.push_back(0);
          if (!Val.empty()) {
            Record.append(Val.begin(), Val.end());
            Record.push_back(0);
          }
        }
      }

      Stream.EmitRecord(bitc::PARAMATTR_GRP_CODE_ENTRY, Record);
      Record.clear();
    }
  }

  Stream.ExitBlock();
}

static void WriteAttributeTable(const ValueEnumerator &VE,
                                BitstreamWriter &Stream) {
  const std::vector<AttributeSet> &Attrs = VE.getAttributes();
  if (Attrs.empty()) return;

  Stream.EnterSubblock(bitc::PARAMATTR_BLOCK_ID, 3);

  SmallVector<uint64_t, 64> Record;
  for (unsigned i = 0, e = Attrs.size(); i != e; ++i) {
    const AttributeSet &A = Attrs[i];
    for (unsigned i = 0, e = A.getNumSlots(); i != e; ++i)
      Record.push_back(VE.getAttributeGroupID(A.getSlotAttributes(i)));

    Stream.EmitRecord(bitc::PARAMATTR_CODE_ENTRY, Record);
    Record.clear();
  }

  Stream.ExitBlock();
}

/// WriteTypeTable - Write out the type table for a module.
static void WriteTypeTable(const ValueEnumerator &VE, BitstreamWriter &Stream) {
  const ValueEnumerator::TypeList &TypeList = VE.getTypes();

  Stream.EnterSubblock(bitc::TYPE_BLOCK_ID_NEW, 4 /*count from # abbrevs */);
  SmallVector<uint64_t, 64> TypeVals;

  uint64_t NumBits = Log2_32_Ceil(VE.getTypes().size()+1);

  // Abbrev for TYPE_CODE_POINTER.
  BitCodeAbbrev *Abbv = new BitCodeAbbrev();
  Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_POINTER));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));
  Abbv->Add(BitCodeAbbrevOp(0));  // Addrspace = 0
  unsigned PtrAbbrev = Stream.EmitAbbrev(Abbv);

  // Abbrev for TYPE_CODE_FUNCTION.
  Abbv = new BitCodeAbbrev();
  Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_FUNCTION));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // isvararg
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));

  unsigned FunctionAbbrev = Stream.EmitAbbrev(Abbv);

  // Abbrev for TYPE_CODE_STRUCT_ANON.
  Abbv = new BitCodeAbbrev();
  Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_ANON));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));

  unsigned StructAnonAbbrev = Stream.EmitAbbrev(Abbv);

  // Abbrev for TYPE_CODE_STRUCT_NAME.
  Abbv = new BitCodeAbbrev();
  Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAME));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Char6));
  unsigned StructNameAbbrev = Stream.EmitAbbrev(Abbv);

  // Abbrev for TYPE_CODE_STRUCT_NAMED.
  Abbv = new BitCodeAbbrev();
  Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_STRUCT_NAMED));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));  // ispacked
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));

  unsigned StructNamedAbbrev = Stream.EmitAbbrev(Abbv);

  // Abbrev for TYPE_CODE_ARRAY.
  Abbv = new BitCodeAbbrev();
  Abbv->Add(BitCodeAbbrevOp(bitc::TYPE_CODE_ARRAY));
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));   // size
  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, NumBits));

  unsigned ArrayAbbrev = Stream.EmitAbbrev(Abbv);

  // Emit an entry count so the reader can reserve space.
  TypeVals.push_back(TypeList.size());
  Stream.EmitRecord(bitc::TYPE_CODE_NUMENTRY, TypeVals);
  TypeVals.clear();

  // Loop over all of the types, emitting each in turn.
  for (unsigned i = 0, e = TypeList.size(); i != e; ++i) {
    Type *T = TypeList[i];
    int AbbrevToUse = 0;
    unsigned Code = 0;

    switch (T->getTypeID()) {
    case Type::VoidTyID:      Code = bitc::TYPE_CODE_VOID;      break;
    case Type::HalfTyID:      Code = bitc::TYPE_CODE_HALF;      break;
    case Type::FloatTyID:     Code = bitc::TYPE_CODE_FLOAT;     break;
    case Type::DoubleTyID:    Code = bitc::TYPE_CODE_DOUBLE;    break;
    case Type::X86_FP80TyID:  Code = bitc::TYPE_CODE_X86_FP80;  break;
    case Type::FP128TyID:     Code = bitc::TYPE_CODE_FP128;     break;
    case Type::PPC_FP128TyID: Code = bitc::TYPE_CODE_PPC_FP128; break;
    case Type::LabelTyID:     Code = bitc::TYPE_CODE_LABEL;     break;
    case Type::MetadataTyID:  Code = bitc::TYPE_CODE_METADATA;  break;
    case Type::X86_MMXTyID:   Code = bitc::TYPE_CODE_X86_MMX;   break;
    case Type::IntegerTyID:
      // INTEGER: [width]
      Code = bitc::TYPE_CODE_INTEGER;
      TypeVals.push_back(cast<IntegerType>(T)->getBitWidth());
      break;
    case Type::PointerTyID: {
      PointerType *PTy = cast<PointerType>(T);
      // POINTER: [pointee type, address space]
      Code = bitc::TYPE_CODE_POINTER;
      TypeVals.push_back(VE.getTypeID(PTy->getElementType()));
      unsigned AddressSpace = PTy->getAddressSpace();
      TypeVals.push_back(AddressSpace);
      if (AddressSpace == 0) AbbrevToUse = PtrAbbrev;
      break;
    }
    case Type::FunctionTyID: {
      FunctionType *FT = cast<FunctionType>(T);
      // FUNCTION: [isvararg, retty, paramty x N]
      Code = bitc::TYPE_CODE_FUNCTION;
      TypeVals.push_back(FT->isVarArg());
      TypeVals.push_back(VE.getTypeID(FT->getReturnType()));
      for (unsigned i = 0, e = FT->getNumParams(); i != e; ++i)
        TypeVals.push_back(VE.getTypeID(FT->getParamType(i)));
      AbbrevToUse = FunctionAbbrev;
      break;
    }
    case Type::StructTyID: {
      StructType *ST = cast<StructType>(T);
      // STRUCT: [ispacked, eltty x N]
      TypeVals.push_back(ST->isPacked());
      // Output all of the element types.
      for (StructType::element_iterator I = ST->element_begin(),
           E = ST->element_end(); I != E; ++I)
        TypeVals.push_back(VE.getTypeID(*I));

      if (ST->isLiteral()) {
        Code = bitc::TYPE_CODE_STRUCT_ANON;
        AbbrevToUse = StructAnonAbbrev;
      } else {
        if (ST->isOpaque()) {
          Code = bitc::TYPE_CODE_OPAQUE;
        } else {
          Code = bitc::TYPE_CODE_STRUCT_NAMED;
          AbbrevToUse = StructNamedAbbrev;
        }

        // Emit the name if it is present.
        if (!ST->getName().empty())
          WriteStringRecord(bitc::TYPE_CODE_STRUCT_NAME, ST->getName(),
                            StructNameAbbrev, Stream);
      }
      break;
    }
    case Type::ArrayTyID: {
      ArrayType *AT = cast<ArrayType>(T);
      // ARRAY: [numelts, eltty]
      Code = bitc::TYPE_CODE_ARRAY;
      TypeVals.push_back(AT->getNumElements());
      TypeVals.push_back(VE.getTypeID(AT->getElementType()));
      AbbrevToUse = ArrayAbbrev;
      break;
    }
    case Type::VectorTyID: {
      VectorType *VT = cast<VectorType>(T);
      // VECTOR [numelts, eltty]
      Code = bitc::TYPE_CODE_VECTOR;
      TypeVals.push_back(VT->getNumElements());
      TypeVals.push_back(VE.getTypeID(VT->getElementType()));
      break;
    }
    }

    // Emit the finished record.
    Stream.EmitRecord(Code, TypeVals, AbbrevToUse);
    TypeVals.clear();
  }

  Stream.ExitBlock();
}

static unsigned getEncodedLinkage(const GlobalValue &GV) {
  switch (GV.getLinkage()) {
  case GlobalValue::ExternalLinkage:
    return 0;
  case GlobalValue::WeakAnyLinkage:
    return 16;
  case GlobalValue::AppendingLinkage:
    return 2;
  case GlobalValue::InternalLinkage:
    return 3;
  case GlobalValue::LinkOnceAnyLinkage:
    return 18;
  case GlobalValue::ExternalWeakLinkage:
    return 7;
  case GlobalValue::CommonLinkage:
    return 8;
  case GlobalValue::PrivateLinkage:
    return 9;
  case GlobalValue::WeakODRLinkage:
    return 17;
  case GlobalValue::LinkOnceODRLinkage:
    return 19;
  case GlobalValue::AvailableExternallyLinkage:
    return 12;
  }
  llvm_unreachable("Invalid linkage");
}

static unsigned getEncodedVisibility(const GlobalValue &GV) {
  switch (GV.getVisibility()) {
  case GlobalValue::DefaultVisibility:   return 0;
  case GlobalValue::HiddenVisibility:    return 1;
  case GlobalValue::ProtectedVisibility: return 2;
  }
  llvm_unreachable("Invalid visibility");
}

static unsigned getEncodedDLLStorageClass(const GlobalValue &GV) {
  switch (GV.getDLLStorageClass()) {
  case GlobalValue::DefaultStorageClass:   return 0;
  case GlobalValue::DLLImportStorageClass: return 1;
  case GlobalValue::DLLExportStorageClass: return 2;
  }
  llvm_unreachable("Invalid DLL storage class");
}

static unsigned getEncodedThreadLocalMode(const GlobalValue &GV) {
  switch (GV.getThreadLocalMode()) {
    case GlobalVariable::NotThreadLocal:         return 0;
    case GlobalVariable::GeneralDynamicTLSModel: return 1;
    case GlobalVariable::LocalDynamicTLSModel:   return 2;
    case GlobalVariable::InitialExecTLSModel:    return 3;
    case GlobalVariable::LocalExecTLSModel:      return 4;
  }
  llvm_unreachable("Invalid TLS model");
}

static unsigned getEncodedComdatSelectionKind(const Comdat &C) {
  switch (C.getSelectionKind()) {
  case Comdat::Any:
    return bitc::COMDAT_SELECTION_KIND_ANY;
  case Comdat::ExactMatch:
    return bitc::COMDAT_SELECTION_KIND_EXACT_MATCH;
  case Comdat::Largest:
    return bitc::COMDAT_SELECTION_KIND_LARGEST;
  case Comdat::NoDuplicates:
    return bitc::COMDAT_SELECTION_KIND_NO_DUPLICATES;
  case Comdat::SameSize:
    return bitc::COMDAT_SELECTION_KIND_SAME_SIZE;
  }
  llvm_unreachable("Invalid selection kind");
}

static void writeComdats(const ValueEnumerator &VE, BitstreamWriter &Stream) {
  SmallVector<uint16_t, 64> Vals;
  for (const Comdat *C : VE.getComdats()) {
    // COMDAT: [selection_kind, name]
    Vals.push_back(getEncodedComdatSelectionKind(*C));
    size_t Size = C->getName().size();
    assert(isUInt<16>(Size));
    Vals.push_back(Size);
    for (char Chr : C->getName())
      Vals.push_back((unsigned char)Chr);
    Stream.EmitRecord(bitc::MODULE_CODE_COMDAT, Vals, /*AbbrevToUse=*/0);
    Vals.clear();
  }
}

// Emit top-level description of module, including target triple, inline asm,
// descriptors for global variables, and function prototype info.
static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
                            BitstreamWriter &Stream) {
  // Emit various pieces of data attached to a module.
  if (!M->getTargetTriple().empty())
    WriteStringRecord(bitc::MODULE_CODE_TRIPLE, M->getTargetTriple(),
                      0/*TODO*/, Stream);
  const std::string &DL = M->getDataLayoutStr();
  if (!DL.empty())
    WriteStringRecord(bitc::MODULE_CODE_DATALAYOUT, DL, 0 /*TODO*/, Stream);
  if (!M->getModuleInlineAsm().empty())
    WriteStringRecord(bitc::MODULE_CODE_ASM, M->getModuleInlineAsm(),
                      0/*TODO*/, Stream);

  // Emit information about sections and GC, computing how many there are. Also
  // compute the maximum alignment value.
  std::map<std::string, unsigned> SectionMap;
  std::map<std::string, unsigned> GCMap;
  unsigned MaxAlignment = 0;
  unsigned MaxGlobalType = 0;
  for (const GlobalValue &GV : M->globals()) {
    MaxAlignment = std::max(MaxAlignment, GV.getAlignment());
    MaxGlobalType = std::max(MaxGlobalType, VE.getTypeID(GV.getType()));
    if (GV.hasSection()) {
      // Give section names unique ID's.
      unsigned &Entry = SectionMap[GV.getSection()];
      if (!Entry) {
        WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, GV.getSection(),
                          0/*TODO*/, Stream);
        Entry = SectionMap.size();
      }
    }
  }
  for (const Function &F : *M) {
    MaxAlignment = std::max(MaxAlignment, F.getAlignment());
    if (F.hasSection()) {
      // Give section names unique ID's.
      unsigned &Entry = SectionMap[F.getSection()];
      if (!Entry) {
        WriteStringRecord(bitc::MODULE_CODE_SECTIONNAME, F.getSection(),
                          0/*TODO*/, Stream);
        Entry = SectionMap.size();
      }
    }
    if (F.hasGC()) {
      // Same for GC names.
      unsigned &Entry = GCMap[F.getGC()];
      if (!Entry) {
        WriteStringRecord(bitc::MODULE_CODE_GCNAME, F.getGC(),
                          0/*TODO*/, Stream);
        Entry = GCMap.size();
      }
    }
  }

  // Emit abbrev for globals, now that we know # sections and max alignment.
  unsigned SimpleGVarAbbrev = 0;
  if (!M->global_empty()) {
    // Add an abbrev for common globals with no visibility or thread localness.
    BitCodeAbbrev *Abbv = new BitCodeAbbrev();
    Abbv->Add(BitCodeAbbrevOp(bitc::MODULE_CODE_GLOBALVAR));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
                              Log2_32_Ceil(MaxGlobalType+1)));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));      // Constant.
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));        // Initializer.
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 5));      // Linkage.
    if (MaxAlignment == 0)                                      // Alignment.
      Abbv->Add(BitCodeAbbrevOp(0));
    else {
      unsigned MaxEncAlignment = Log2_32(MaxAlignment)+1;
      Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
                               Log2_32_Ceil(MaxEncAlignment+1)));
    }
    if (SectionMap.empty())                                    // Section.
      Abbv->Add(BitCodeAbbrevOp(0));
    else
      Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed,
                               Log2_32_Ceil(SectionMap.size()+1)));
    // Don't bother emitting vis + thread local.
    SimpleGVarAbbrev = Stream.EmitAbbrev(Abbv);
  }

  // Emit the global variable information.
  SmallVector<unsigned, 64> Vals;
  for (const GlobalVariable &GV : M->globals()) {
    unsigned AbbrevToUse = 0;

    // GLOBALVAR: [type, isconst, initid,
    //             linkage, alignment, section, visibility, threadlocal,
    //             unnamed_addr, externally_initialized, dllstorageclass]
    Vals.push_back(VE.getTypeID(GV.getType()));
    Vals.push_back(GV.isConstant());
    Vals.push_back(GV.isDeclaration() ? 0 :
                   (VE.getValueID(GV.getInitializer()) + 1));
    Vals.push_back(getEncodedLinkage(GV));
    Vals.push_back(Log2_32(GV.getAlignment())+1);
    Vals.push_back(GV.hasSection() ? SectionMap[GV.getSection()] : 0);
    if (GV.isThreadLocal() ||
        GV.getVisibility() != GlobalValue::DefaultVisibility ||
        GV.hasUnnamedAddr() || GV.isExternallyInitialized() ||
        GV.getDLLStorageClass() != GlobalValue::DefaultStorageClass ||
        GV.hasComdat()) {
      Vals.push_back(getEncodedVisibility(GV));
      Vals.push_back(getEncodedThreadLocalMode(GV));
      Vals.push_back(GV.hasUnnamedAddr());
      Vals.push_back(GV.isExternallyInitialized());
      Vals.push_back(getEncodedDLLStorageClass(GV));
      Vals.push_back(GV.hasComdat() ? VE.getComdatID(GV.getComdat()) : 0);
    } else {
      AbbrevToUse = SimpleGVarAbbrev;
    }

    Stream.EmitRecord(bitc::MODULE_CODE_GLOBALVAR, Vals, AbbrevToUse);
    Vals.clear();
  }

  // Emit the function proto information.
  for (const Function &F : *M) {
    // FUNCTION:  [type, callingconv, isproto, linkage, paramattrs, alignment,
    //             section, visibility, gc, unnamed_addr, prologuedata,
    //             dllstorageclass, comdat, prefixdata]
    Vals.push_back(VE.getTypeID(F.getType()));
    Vals.push_back(F.getCallingConv());
    Vals.push_back(F.isDeclaration());
    Vals.push_back(getEncodedLinkage(F));
    Vals.push_back(VE.getAttributeID(F.getAttributes()));
    Vals.push_back(Log2_32(F.getAlignment())+1);
    Vals.push_back(F.hasSection() ? SectionMap[F.getSection()] : 0);
    Vals.push_back(getEncodedVisibility(F));
    Vals.push_back(F.hasGC() ? GCMap[F.getGC()] : 0);
    Vals.push_back(F.hasUnnamedAddr());
    Vals.push_back(F.hasPrologueData() ? (VE.getValueID(F.getPrologueData()) + 1)
                                       : 0);
    Vals.push_back(getEncodedDLLStorageClass(F));
    Vals.push_back(F.hasComdat() ? VE.getComdatID(F.getComdat()) : 0);
    Vals.push_back(F.hasPrefixData() ? (VE.getValueID(F.getPrefixData()) + 1)
                                     : 0);

    unsigned AbbrevToUse = 0;
    Stream.EmitRecord(bitc::MODULE_CODE_FUNCTION, Vals, AbbrevToUse);
    Vals.clear();
  }

  // Emit the alias information.
  for (const GlobalAlias &A : M->aliases()) {
    // ALIAS: [alias type, aliasee val#, linkage, visibility]
    Vals.push_back(VE.getTypeID(A.getType()));
    Vals.push_back(VE.getValueID(A.getAliasee()));
    Vals.push_back(getEncodedLinkage(A));
    Vals.push_back(getEncodedVisibility(A));
    Vals.push_back(getEncodedDLLStorageClass(A));
    Vals.push_back(getEncodedThreadLocalMode(A));
    Vals.push_back(A.hasUnnamedAddr());
    unsigned AbbrevToUse = 0;
    Stream.EmitRecord(bitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
    Vals.clear();
  }
}

static uint64_t GetOptimizationFlags(const Value *V) {
  uint64_t Flags = 0;

  if (const auto *OBO = dyn_cast<OverflowingBinaryOperator>(V)) {
    if (OBO->hasNoSignedWrap())
      Flags |= 1 << bitc::OBO_NO_SIGNED_WRAP;
    if (OBO->hasNoUnsignedWrap())
      Flags |= 1 << bitc::OBO_NO_UNSIGNED_WRAP;
  } else if (const auto *PEO = dyn_cast<PossiblyExactOperator>(V)) {
    if (PEO->isExact())
      Flags |= 1 << bitc::PEO_EXACT;
  } else if (const auto *FPMO = dyn_cast<FPMathOperator>(V)) {
    if (FPMO->hasUnsafeAlgebra())
      Flags |= FastMathFlags::UnsafeAlgebra;
    if (FPMO->hasNoNaNs())
      Flags |= FastMathFlags::NoNaNs;
    if (FPMO->hasNoInfs())
      Flags |= FastMathFlags::NoInfs;
    if (FPMO->hasNoSignedZeros())
      Flags |= FastMathFlags::NoSignedZeros;
    if (FPMO->hasAllowReciprocal())
      Flags |= FastMathFlags::AllowReciprocal;
  }

  return Flags;
}

static void WriteValueAsMetadata(const ValueAsMetadata *MD,
                                 const ValueEnumerator &VE,
                                 BitstreamWriter &Stream,
                                 SmallVectorImpl<uint64_t> &Record) {
  // Mimic an MDNode with a value as one operand.
  Value *V = MD->getValue();
  Record.push_back(VE.getTypeID(V->getType()));
  Record.push_back(VE.getValueID(V));
  Stream.EmitRecord(bitc::METADATA_VALUE, Record, 0);
  Record.clear();
}

static void WriteMDTuple(const MDTuple *N, const ValueEnumerator &VE,
                         BitstreamWriter &Stream,
                         SmallVectorImpl<uint64_t> &Record, unsigned Abbrev) {
  for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
    Metadata *MD = N->getOperand(i);
    assert(!(MD && isa<LocalAsMetadata>(MD)) &&
           "Unexpected function-local metadata");
    Record.push_back(VE.getMetadataOrNullID(MD));
  }
  Stream.EmitRecord(N->isDistinct() ? bitc::METADATA_DISTINCT_NODE
                                    : bitc::METADATA_NODE,
                    Record, Abbrev);
  Record.clear();
}

static void WriteMDLocation(const MDLocation *N, const ValueEnumerator &VE,
                            BitstreamWriter &Stream,
                            SmallVectorImpl<uint64_t> &Record,
                            unsigned Abbrev) {
  Record.push_back(N->isDistinct());
  Record.push_back(N->getLine());
  Record.push_back(N->getColumn());
  Record.push_back(VE.getMetadataID(N->getScope()));
  Record.push_back(VE.getMetadataOrNullID(N->getInlinedAt()));

  Stream.EmitRecord(bitc::METADATA_LOCATION, Record, Abbrev);
  Record.clear();
}

static void WriteGenericDebugNode(const GenericDebugNode *,
                                  const ValueEnumerator &, BitstreamWriter &,
                                  SmallVectorImpl<uint64_t> &, unsigned) {
  llvm_unreachable("unimplemented");
}

static void WriteModuleMetadata(const Module *M,
                                const ValueEnumerator &VE,
                                BitstreamWriter &Stream) {
  const auto &MDs = VE.getMDs();
  if (MDs.empty() && M->named_metadata_empty())
    return;

  Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);

  unsigned MDSAbbrev = 0;
  if (VE.hasMDString()) {
    // Abbrev for METADATA_STRING.
    BitCodeAbbrev *Abbv = new BitCodeAbbrev();
    Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_STRING));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
    MDSAbbrev = Stream.EmitAbbrev(Abbv);
  }

  unsigned MDLocationAbbrev = 0;
  if (VE.hasMDLocation()) {
    // Abbrev for METADATA_LOCATION.
    //
    // Assume the column is usually under 128, and always output the inlined-at
    // location (it's never more expensive than building an array size 1).
    BitCodeAbbrev *Abbv = new BitCodeAbbrev();
    Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_LOCATION));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));
    MDLocationAbbrev = Stream.EmitAbbrev(Abbv);
  }

  unsigned NameAbbrev = 0;
  if (!M->named_metadata_empty()) {
    // Abbrev for METADATA_NAME.
    BitCodeAbbrev *Abbv = new BitCodeAbbrev();
    Abbv->Add(BitCodeAbbrevOp(bitc::METADATA_NAME));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
    NameAbbrev = Stream.EmitAbbrev(Abbv);
  }

  unsigned MDTupleAbbrev = 0;
  unsigned GenericDebugNodeAbbrev = 0;
  SmallVector<uint64_t, 64> Record;
  for (const Metadata *MD : MDs) {
    if (const MDNode *N = dyn_cast<MDNode>(MD)) {
      switch (N->getMetadataID()) {
      default:
        llvm_unreachable("Invalid MDNode subclass");
#define HANDLE_MDNODE_LEAF(CLASS)                                              \
  case Metadata::CLASS##Kind:                                                  \
    Write##CLASS(cast<CLASS>(N), VE, Stream, Record, CLASS##Abbrev);           \
    continue;
#include "llvm/IR/Metadata.def"
      }
    }
    if (const auto *MDC = dyn_cast<ConstantAsMetadata>(MD)) {
      WriteValueAsMetadata(MDC, VE, Stream, Record);
      continue;
    }
    const MDString *MDS = cast<MDString>(MD);
    // Code: [strchar x N]
    Record.append(MDS->bytes_begin(), MDS->bytes_end());

    // Emit the finished record.
    Stream.EmitRecord(bitc::METADATA_STRING, Record, MDSAbbrev);
    Record.clear();
  }

  // Write named metadata.
  for (const NamedMDNode &NMD : M->named_metadata()) {
    // Write name.
    StringRef Str = NMD.getName();
    Record.append(Str.bytes_begin(), Str.bytes_end());
    Stream.EmitRecord(bitc::METADATA_NAME, Record, NameAbbrev);
    Record.clear();

    // Write named metadata operands.
    for (const MDNode *N : NMD.operands())
      Record.push_back(VE.getMetadataID(N));
    Stream.EmitRecord(bitc::METADATA_NAMED_NODE, Record, 0);
    Record.clear();
  }

  Stream.ExitBlock();
}

static void WriteFunctionLocalMetadata(const Function &F,
                                       const ValueEnumerator &VE,
                                       BitstreamWriter &Stream) {
  bool StartedMetadataBlock = false;
  SmallVector<uint64_t, 64> Record;
  const SmallVectorImpl<const LocalAsMetadata *> &MDs =
      VE.getFunctionLocalMDs();
  for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
    assert(MDs[i] && "Expected valid function-local metadata");
    if (!StartedMetadataBlock) {
      Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);
      StartedMetadataBlock = true;
    }
    WriteValueAsMetadata(MDs[i], VE, Stream, Record);
  }

  if (StartedMetadataBlock)
    Stream.ExitBlock();
}

static void WriteMetadataAttachment(const Function &F,
                                    const ValueEnumerator &VE,
                                    BitstreamWriter &Stream) {
  Stream.EnterSubblock(bitc::METADATA_ATTACHMENT_ID, 3);

  SmallVector<uint64_t, 64> Record;

  // Write metadata attachments
  // METADATA_ATTACHMENT - [m x [value, [n x [id, mdnode]]]
  SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;

  for (Function::const_iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
    for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
         I != E; ++I) {
      MDs.clear();
      I->getAllMetadataOtherThanDebugLoc(MDs);

      // If no metadata, ignore instruction.
      if (MDs.empty()) continue;

      Record.push_back(VE.getInstructionID(I));

      for (unsigned i = 0, e = MDs.size(); i != e; ++i) {
        Record.push_back(MDs[i].first);
        Record.push_back(VE.getMetadataID(MDs[i].second));
      }
      Stream.EmitRecord(bitc::METADATA_ATTACHMENT, Record, 0);
      Record.clear();
    }

  Stream.ExitBlock();
}

static void WriteModuleMetadataStore(const Module *M, BitstreamWriter &Stream) {
  SmallVector<uint64_t, 64> Record;

  // Write metadata kinds
  // METADATA_KIND - [n x [id, name]]
  SmallVector<StringRef, 8> Names;
  M->getMDKindNames(Names);

  if (Names.empty()) return;

  Stream.EnterSubblock(bitc::METADATA_BLOCK_ID, 3);

  for (unsigned MDKindID = 0, e = Names.size(); MDKindID != e; ++MDKindID) {
    Record.push_back(MDKindID);
    StringRef KName = Names[MDKindID];
    Record.append(KName.begin(), KName.end());

    Stream.EmitRecord(bitc::METADATA_KIND, Record, 0);
    Record.clear();
  }

  Stream.ExitBlock();
}

static void emitSignedInt64(SmallVectorImpl<uint64_t> &Vals, uint64_t V) {
  if ((int64_t)V >= 0)
    Vals.push_back(V << 1);
  else
    Vals.push_back((-V << 1) | 1);
}

static void WriteConstants(unsigned FirstVal, unsigned LastVal,
                           const ValueEnumerator &VE,
                           BitstreamWriter &Stream, bool isGlobal) {
  if (FirstVal == LastVal) return;

  Stream.EnterSubblock(bitc::CONSTANTS_BLOCK_ID, 4);

  unsigned AggregateAbbrev = 0;
  unsigned String8Abbrev = 0;
  unsigned CString7Abbrev = 0;
  unsigned CString6Abbrev = 0;
  // If this is a constant pool for the module, emit module-specific abbrevs.
  if (isGlobal) {
    // Abbrev for CST_CODE_AGGREGATE.
    BitCodeAbbrev *Abbv = new BitCodeAbbrev();
    Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_AGGREGATE));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, Log2_32_Ceil(LastVal+1)));
    AggregateAbbrev = Stream.EmitAbbrev(Abbv);

    // Abbrev for CST_CODE_STRING.
    Abbv = new BitCodeAbbrev();
    Abbv->Add(BitCodeAbbrevOp(bitc::CST_CODE_STRING));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 8));
    String8Abbrev = Stream.EmitAbbrev(Abbv);