text: //===- ValueEnumerator.cpp - Number values and types for bitcode writer ---===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the ValueEnumerator class.
  //
  //===----------------------------------------------------------------------===//
  
  #include "ValueEnumerator.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/Config/llvm-config.h"
  #include "llvm/IR/Argument.h"
  #include "llvm/IR/Attributes.h"
  #include "llvm/IR/BasicBlock.h"
  #include "llvm/IR/Constant.h"
  #include "llvm/IR/DebugInfoMetadata.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Function.h"
  #include "llvm/IR/GlobalAlias.h"
  #include "llvm/IR/GlobalIFunc.h"
  #include "llvm/IR/GlobalObject.h"
  #include "llvm/IR/GlobalValue.h"
  #include "llvm/IR/GlobalVariable.h"
  #include "llvm/IR/Instruction.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/Metadata.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/Type.h"
  #include "llvm/IR/Use.h"
  #include "llvm/IR/UseListOrder.h"
  #include "llvm/IR/User.h"
  #include "llvm/IR/Value.h"
  #include "llvm/IR/ValueSymbolTable.h"
  #include "llvm/Support/Casting.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/raw_ostream.h"
  #include <algorithm>
  #include <cassert>
  #include <cstddef>
  #include <iterator>
  #include <tuple>
  #include <utility>
  #include <vector>
  
  using namespace llvm;
  
  namespace {
  
  struct OrderMap {
    DenseMap<const Value *, std::pair<unsigned, bool>> IDs;
    unsigned LastGlobalConstantID = 0;
    unsigned LastGlobalValueID = 0;
  
    OrderMap() = default;
  
    bool isGlobalConstant(unsigned ID) const {
      return ID <= LastGlobalConstantID;
    }
  
    bool isGlobalValue(unsigned ID) const {
      return ID <= LastGlobalValueID && !isGlobalConstant(ID);
    }
  
    unsigned size() const { return IDs.size(); }
    std::pair<unsigned, bool> &operator[](const Value *V) { return IDs[V]; }
  
    std::pair<unsigned, bool> lookup(const Value *V) const {
      return IDs.lookup(V);
    }
  
    void index(const Value *V) {
      // Explicitly sequence get-size and insert-value operations to avoid UB.
      unsigned ID = IDs.size() + 1;
      IDs[V].first = ID;
    }
  };
  
  } // end anonymous namespace
  
  static void orderValue(const Value *V, OrderMap &OM) {
    if (OM.lookup(V).first)
      return;
  
    if (const Constant *C = dyn_cast<Constant>(V))
      if (C->getNumOperands() && !isa<GlobalValue>(C))
        for (const Value *Op : C->operands())
          if (!isa<BasicBlock>(Op) && !isa<GlobalValue>(Op))
            orderValue(Op, OM);
  
    // Note: we cannot cache this lookup above, since inserting into the map
    // changes the map's size, and thus affects the other IDs.
    OM.index(V);
  }
  
  static OrderMap orderModule(const Module &M) {
    // This needs to match the order used by ValueEnumerator::ValueEnumerator()
    // and ValueEnumerator::incorporateFunction().
    OrderMap OM;
  
    // In the reader, initializers of GlobalValues are set *after* all the
    // globals have been read.  Rather than awkwardly modeling this behaviour
    // directly in predictValueUseListOrderImpl(), just assign IDs to
    // initializers of GlobalValues before GlobalValues themselves to model this
    // implicitly.
    for (const GlobalVariable &G : M.globals())
      if (G.hasInitializer())
        if (!isa<GlobalValue>(G.getInitializer()))
          orderValue(G.getInitializer(), OM);
    for (const GlobalAlias &A : M.aliases())
      if (!isa<GlobalValue>(A.getAliasee()))
        orderValue(A.getAliasee(), OM);
    for (const GlobalIFunc &I : M.ifuncs())
      if (!isa<GlobalValue>(I.getResolver()))
        orderValue(I.getResolver(), OM);
    for (const Function &F : M) {
      for (const Use &U : F.operands())
        if (!isa<GlobalValue>(U.get()))
          orderValue(U.get(), OM);
    }
    OM.LastGlobalConstantID = OM.size();
  
    // Initializers of GlobalValues are processed in
    // BitcodeReader::ResolveGlobalAndAliasInits().  Match the order there rather
    // than ValueEnumerator, and match the code in predictValueUseListOrderImpl()
    // by giving IDs in reverse order.
    //
    // Since GlobalValues never reference each other directly (just through
    // initializers), their relative IDs only matter for determining order of
    // uses in their initializers.
    for (const Function &F : M)
      orderValue(&F, OM);
    for (const GlobalAlias &A : M.aliases())
      orderValue(&A, OM);
    for (const GlobalIFunc &I : M.ifuncs())
      orderValue(&I, OM);
    for (const GlobalVariable &G : M.globals())
      orderValue(&G, OM);
    OM.LastGlobalValueID = OM.size();
  
    for (const Function &F : M) {
      if (F.isDeclaration())
        continue;
      // Here we need to match the union of ValueEnumerator::incorporateFunction()
      // and WriteFunction().  Basic blocks are implicitly declared before
      // anything else (by declaring their size).
      for (const BasicBlock &BB : F)
        orderValue(&BB, OM);
      for (const Argument &A : F.args())
        orderValue(&A, OM);
      for (const BasicBlock &BB : F)
        for (const Instruction &I : BB)
          for (const Value *Op : I.operands())
            if ((isa<Constant>(*Op) && !isa<GlobalValue>(*Op)) ||
                isa<InlineAsm>(*Op))
              orderValue(Op, OM);
      for (const BasicBlock &BB : F)
        for (const Instruction &I : BB)
          orderValue(&I, OM);
    }
    return OM;
  }
  
  static void predictValueUseListOrderImpl(const Value *V, const Function *F,
                                           unsigned ID, const OrderMap &OM,
                                           UseListOrderStack &Stack) {
    // Predict use-list order for this one.
    using Entry = std::pair<const Use *, unsigned>;
    SmallVector<Entry, 64> List;
    for (const Use &U : V->uses())
      // Check if this user will be serialized.
      if (OM.lookup(U.getUser()).first)
        List.push_back(std::make_pair(&U, List.size()));
  
    if (List.size() < 2)
      // We may have lost some users.
      return;
  
    bool IsGlobalValue = OM.isGlobalValue(ID);
    llvm::sort(List.begin(), List.end(), [&](const Entry &L, const Entry &R) {
      const Use *LU = L.first;
      const Use *RU = R.first;
      if (LU == RU)
        return false;
  
      auto LID = OM.lookup(LU->getUser()).first;
      auto RID = OM.lookup(RU->getUser()).first;
  
      // Global values are processed in reverse order.
      //
      // Moreover, initializers of GlobalValues are set *after* all the globals
      // have been read (despite having earlier IDs).  Rather than awkwardly
      // modeling this behaviour here, orderModule() has assigned IDs to
      // initializers of GlobalValues before GlobalValues themselves.
      if (OM.isGlobalValue(LID) && OM.isGlobalValue(RID))
        return LID < RID;
  
      // If ID is 4, then expect: 7 6 5 1 2 3.
      if (LID < RID) {
        if (RID <= ID)
          if (!IsGlobalValue) // GlobalValue uses don't get reversed.
            return true;
        return false;
      }
      if (RID < LID) {
        if (LID <= ID)
          if (!IsGlobalValue) // GlobalValue uses don't get reversed.
            return false;
        return true;
      }
  
      // LID and RID are equal, so we have different operands of the same user.
      // Assume operands are added in order for all instructions.
      if (LID <= ID)
        if (!IsGlobalValue) // GlobalValue uses don't get reversed.
          return LU->getOperandNo() < RU->getOperandNo();
      return LU->getOperandNo() > RU->getOperandNo();
    });
  
    if (std::is_sorted(
            List.begin(), List.end(),
            [](const Entry &L, const Entry &R) { return L.second < R.second; }))
      // Order is already correct.
      return;
  
    // Store the shuffle.
    Stack.emplace_back(V, F, List.size());
    assert(List.size() == Stack.back().Shuffle.size() && "Wrong size");
    for (size_t I = 0, E = List.size(); I != E; ++I)
      Stack.back().Shuffle[I] = List[I].second;
  }
  
  static void predictValueUseListOrder(const Value *V, const Function *F,
                                       OrderMap &OM, UseListOrderStack &Stack) {
    auto &IDPair = OM[V];
    assert(IDPair.first && "Unmapped value");
    if (IDPair.second)
      // Already predicted.
      return;
  
    // Do the actual prediction.
    IDPair.second = true;
    if (!V->use_empty() && std::next(V->use_begin()) != V->use_end())
      predictValueUseListOrderImpl(V, F, IDPair.first, OM, Stack);
  
    // Recursive descent into constants.
    if (const Constant *C = dyn_cast<Constant>(V))
      if (C->getNumOperands()) // Visit GlobalValues.
        for (const Value *Op : C->operands())
          if (isa<Constant>(Op)) // Visit GlobalValues.
            predictValueUseListOrder(Op, F, OM, Stack);
  }
  
  static UseListOrderStack predictUseListOrder(const Module &M) {
    OrderMap OM = orderModule(M);
  
    // Use-list orders need to be serialized after all the users have been added
    // to a value, or else the shuffles will be incomplete.  Store them per
    // function in a stack.
    //
    // Aside from function order, the order of values doesn't matter much here.
    UseListOrderStack Stack;
  
    // We want to visit the functions backward now so we can list function-local
    // constants in the last Function they're used in.  Module-level constants
    // have already been visited above.
    for (auto I = M.rbegin(), E = M.rend(); I != E; ++I) {
      const Function &F = *I;
      if (F.isDeclaration())
        continue;
      for (const BasicBlock &BB : F)
        predictValueUseListOrder(&BB, &F, OM, Stack);
      for (const Argument &A : F.args())
        predictValueUseListOrder(&A, &F, OM, Stack);
      for (const BasicBlock &BB : F)
        for (const Instruction &I : BB)
          for (const Value *Op : I.operands())
            if (isa<Constant>(*Op) || isa<InlineAsm>(*Op)) // Visit GlobalValues.
              predictValueUseListOrder(Op, &F, OM, Stack);
      for (const BasicBlock &BB : F)
        for (const Instruction &I : BB)
          predictValueUseListOrder(&I, &F, OM, Stack);
    }
  
    // Visit globals last, since the module-level use-list block will be seen
    // before the function bodies are processed.
    for (const GlobalVariable &G : M.globals())
      predictValueUseListOrder(&G, nullptr, OM, Stack);
    for (const Function &F : M)
      predictValueUseListOrder(&F, nullptr, OM, Stack);
    for (const GlobalAlias &A : M.aliases())
      predictValueUseListOrder(&A, nullptr, OM, Stack);
    for (const GlobalIFunc &I : M.ifuncs())
      predictValueUseListOrder(&I, nullptr, OM, Stack);
    for (const GlobalVariable &G : M.globals())
      if (G.hasInitializer())
        predictValueUseListOrder(G.getInitializer(), nullptr, OM, Stack);
    for (const GlobalAlias &A : M.aliases())
      predictValueUseListOrder(A.getAliasee(), nullptr, OM, Stack);
    for (const GlobalIFunc &I : M.ifuncs())
      predictValueUseListOrder(I.getResolver(), nullptr, OM, Stack);
    for (const Function &F : M) {
      for (const Use &U : F.operands())
        predictValueUseListOrder(U.get(), nullptr, OM, Stack);
    }
  
    return Stack;
  }
  
  static bool isIntOrIntVectorValue(const std::pair<const Value*, unsigned> &V) {
    return V.first->getType()->isIntOrIntVectorTy();
  }
  
  ValueEnumerator::ValueEnumerator(const Module &M,
                                   bool ShouldPreserveUseListOrder)
      : ShouldPreserveUseListOrder(ShouldPreserveUseListOrder) {
    if (ShouldPreserveUseListOrder)
      UseListOrders = predictUseListOrder(M);
  
    // Enumerate the global variables.
    for (const GlobalVariable &GV : M.globals())
      EnumerateValue(&GV);
  
    // Enumerate the functions.
    for (const Function & F : M) {
      EnumerateValue(&F);
      EnumerateAttributes(F.getAttributes());
    }
  
    // Enumerate the aliases.
    for (const GlobalAlias &GA : M.aliases())
      EnumerateValue(&GA);
  
    // Enumerate the ifuncs.
    for (const GlobalIFunc &GIF : M.ifuncs())
      EnumerateValue(&GIF);
  
    // Remember what is the cutoff between globalvalue's and other constants.
    unsigned FirstConstant = Values.size();
  
    // Enumerate the global variable initializers and attributes.
    for (const GlobalVariable &GV : M.globals()) {
      if (GV.hasInitializer())
        EnumerateValue(GV.getInitializer());
      if (GV.hasAttributes())
        EnumerateAttributes(GV.getAttributesAsList(AttributeList::FunctionIndex));
    }
  
    // Enumerate the aliasees.
    for (const GlobalAlias &GA : M.aliases())
      EnumerateValue(GA.getAliasee());
  
    // Enumerate the ifunc resolvers.
    for (const GlobalIFunc &GIF : M.ifuncs())
      EnumerateValue(GIF.getResolver());
  
    // Enumerate any optional Function data.
    for (const Function &F : M)
      for (const Use &U : F.operands())
        EnumerateValue(U.get());
  
    // Enumerate the metadata type.
    //
    // TODO: Move this to ValueEnumerator::EnumerateOperandType() once bitcode
    // only encodes the metadata type when it's used as a value.
    EnumerateType(Type::getMetadataTy(M.getContext()));
  
    // Insert constants and metadata that are named at module level into the slot
    // pool so that the module symbol table can refer to them...
    EnumerateValueSymbolTable(M.getValueSymbolTable());
    EnumerateNamedMetadata(M);
  
    SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
    for (const GlobalVariable &GV : M.globals()) {
      MDs.clear();
      GV.getAllMetadata(MDs);
      for (const auto &I : MDs)
        // FIXME: Pass GV to EnumerateMetadata and arrange for the bitcode writer
        // to write metadata to the global variable's own metadata block
        // (PR28134).
        EnumerateMetadata(nullptr, I.second);
    }
  
    // Enumerate types used by function bodies and argument lists.
    for (const Function &F : M) {
      for (const Argument &A : F.args())
        EnumerateType(A.getType());
  
      // Enumerate metadata attached to this function.
      MDs.clear();
      F.getAllMetadata(MDs);
      for (const auto &I : MDs)
        EnumerateMetadata(F.isDeclaration() ? nullptr : &F, I.second);
  
      for (const BasicBlock &BB : F)
        for (const Instruction &I : BB) {
          for (const Use &Op : I.operands()) {
            auto *MD = dyn_cast<MetadataAsValue>(&Op);
            if (!MD) {
              EnumerateOperandType(Op);
              continue;
            }
  
            // Local metadata is enumerated during function-incorporation.
            if (isa<LocalAsMetadata>(MD->getMetadata()))
              continue;
  
            EnumerateMetadata(&F, MD->getMetadata());
          }
          EnumerateType(I.getType());
          if (const CallInst *CI = dyn_cast<CallInst>(&I))
            EnumerateAttributes(CI->getAttributes());
          else if (const InvokeInst *II = dyn_cast<InvokeInst>(&I))
            EnumerateAttributes(II->getAttributes());
  
          // Enumerate metadata attached with this instruction.
          MDs.clear();
          I.getAllMetadataOtherThanDebugLoc(MDs);
          for (unsigned i = 0, e = MDs.size(); i != e; ++i)
            EnumerateMetadata(&F, MDs[i].second);
  
          // Don't enumerate the location directly -- it has a special record
          // type -- but enumerate its operands.
          if (DILocation *L = I.getDebugLoc())
            for (const Metadata *Op : L->operands())
              EnumerateMetadata(&F, Op);
        }
    }
  
    // Optimize constant ordering.
    OptimizeConstants(FirstConstant, Values.size());
  
    // Organize metadata ordering.
    organizeMetadata();
  }
  
  unsigned ValueEnumerator::getInstructionID(const Instruction *Inst) const {
    InstructionMapType::const_iterator I = InstructionMap.find(Inst);
    assert(I != InstructionMap.end() && "Instruction is not mapped!");
    return I->second;
  }
  
  unsigned ValueEnumerator::getComdatID(const Comdat *C) const {
    unsigned ComdatID = Comdats.idFor(C);
    assert(ComdatID && "Comdat not found!");
    return ComdatID;
  }
  
  void ValueEnumerator::setInstructionID(const Instruction *I) {
    InstructionMap[I] = InstructionCount++;
  }
  
  unsigned ValueEnumerator::getValueID(const Value *V) const {
    if (auto *MD = dyn_cast<MetadataAsValue>(V))
      return getMetadataID(MD->getMetadata());
  
    ValueMapType::const_iterator I = ValueMap.find(V);
    assert(I != ValueMap.end() && "Value not in slotcalculator!");
    return I->second-1;
  }
  
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  LLVM_DUMP_METHOD void ValueEnumerator::dump() const {
    print(dbgs(), ValueMap, "Default");
    dbgs() << '\n';
    print(dbgs(), MetadataMap, "MetaData");
    dbgs() << '\n';
  }
  #endif
  
  void ValueEnumerator::print(raw_ostream &OS, const ValueMapType &Map,
                              const char *Name) const {
    OS << "Map Name: " << Name << "\n";
    OS << "Size: " << Map.size() << "\n";
    for (ValueMapType::const_iterator I = Map.begin(),
           E = Map.end(); I != E; ++I) {
      const Value *V = I->first;
      if (V->hasName())
        OS << "Value: " << V->getName();
      else
        OS << "Value: [null]\n";
      V->print(errs());
      errs() << '\n';
  
      OS << " Uses(" << V->getNumUses() << "):";
      for (const Use &U : V->uses()) {
        if (&U != &*V->use_begin())
          OS << ",";
        if(U->hasName())
          OS << " " << U->getName();
        else
          OS << " [null]";
  
      }
      OS <<  "\n\n";
    }
  }
  
  void ValueEnumerator::print(raw_ostream &OS, const MetadataMapType &Map,
                              const char *Name) const {
    OS << "Map Name: " << Name << "\n";
    OS << "Size: " << Map.size() << "\n";
    for (auto I = Map.begin(), E = Map.end(); I != E; ++I) {
      const Metadata *MD = I->first;
      OS << "Metadata: slot = " << I->second.ID << "\n";
      OS << "Metadata: function = " << I->second.F << "\n";
      MD->print(OS);
      OS << "\n";
    }
  }
  
  /// OptimizeConstants - Reorder constant pool for denser encoding.
  void ValueEnumerator::OptimizeConstants(unsigned CstStart, unsigned CstEnd) {
    if (CstStart == CstEnd || CstStart+1 == CstEnd) return;
  
    if (ShouldPreserveUseListOrder)
      // Optimizing constants makes the use-list order difficult to predict.
      // Disable it for now when trying to preserve the order.
      return;
  
    std::stable_sort(Values.begin() + CstStart, Values.begin() + CstEnd,
                     [this](const std::pair<const Value *, unsigned> &LHS,
                            const std::pair<const Value *, unsigned> &RHS) {
      // Sort by plane.
      if (LHS.first->getType() != RHS.first->getType())
        return getTypeID(LHS.first->getType()) < getTypeID(RHS.first->getType());
      // Then by frequency.
      return LHS.second > RHS.second;
    });
  
    // Ensure that integer and vector of integer constants are at the start of the
    // constant pool.  This is important so that GEP structure indices come before
    // gep constant exprs.
    std::stable_partition(Values.begin() + CstStart, Values.begin() + CstEnd,
                          isIntOrIntVectorValue);
  
    // Rebuild the modified portion of ValueMap.
    for (; CstStart != CstEnd; ++CstStart)
      ValueMap[Values[CstStart].first] = CstStart+1;
  }
  
  /// EnumerateValueSymbolTable - Insert all of the values in the specified symbol
  /// table into the values table.
  void ValueEnumerator::EnumerateValueSymbolTable(const ValueSymbolTable &VST) {
    for (ValueSymbolTable::const_iterator VI = VST.begin(), VE = VST.end();
         VI != VE; ++VI)
      EnumerateValue(VI->getValue());
  }
  
  /// Insert all of the values referenced by named metadata in the specified
  /// module.
  void ValueEnumerator::EnumerateNamedMetadata(const Module &M) {
    for (const auto &I : M.named_metadata())
      EnumerateNamedMDNode(&I);
  }
  
  void ValueEnumerator::EnumerateNamedMDNode(const NamedMDNode *MD) {
    for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i)
      EnumerateMetadata(nullptr, MD->getOperand(i));
  }
  
  unsigned ValueEnumerator::getMetadataFunctionID(const Function *F) const {
    return F ? getValueID(F) + 1 : 0;
  }
  
  void ValueEnumerator::EnumerateMetadata(const Function *F, const Metadata *MD) {
    EnumerateMetadata(getMetadataFunctionID(F), MD);
  }
  
  void ValueEnumerator::EnumerateFunctionLocalMetadata(
      const Function &F, const LocalAsMetadata *Local) {
    EnumerateFunctionLocalMetadata(getMetadataFunctionID(&F), Local);
  }
  
  void ValueEnumerator::dropFunctionFromMetadata(
      MetadataMapType::value_type &FirstMD) {
    SmallVector<const MDNode *, 64> Worklist;
    auto push = [&Worklist](MetadataMapType::value_type &MD) {
      auto &Entry = MD.second;
  
      // Nothing to do if this metadata isn't tagged.
      if (!Entry.F)
        return;
  
      // Drop the function tag.
      Entry.F = 0;
  
      // If this is has an ID and is an MDNode, then its operands have entries as
      // well.  We need to drop the function from them too.
      if (Entry.ID)
        if (auto *N = dyn_cast<MDNode>(MD.first))
          Worklist.push_back(N);
    };
    push(FirstMD);
    while (!Worklist.empty())
      for (const Metadata *Op : Worklist.pop_back_val()->operands()) {
        if (!Op)
          continue;
        auto MD = MetadataMap.find(Op);
        if (MD != MetadataMap.end())
          push(*MD);
      }
  }
  
  void ValueEnumerator::EnumerateMetadata(unsigned F, const Metadata *MD) {
    // It's vital for reader efficiency that uniqued subgraphs are done in
    // post-order; it's expensive when their operands have forward references.
    // If a distinct node is referenced from a uniqued node, it'll be delayed
    // until the uniqued subgraph has been completely traversed.
    SmallVector<const MDNode *, 32> DelayedDistinctNodes;
  
    // Start by enumerating MD, and then work through its transitive operands in
    // post-order.  This requires a depth-first search.
    SmallVector<std::pair<const MDNode *, MDNode::op_iterator>, 32> Worklist;
    if (const MDNode *N = enumerateMetadataImpl(F, MD))
      Worklist.push_back(std::make_pair(N, N->op_begin()));
  
    while (!Worklist.empty()) {
      const MDNode *N = Worklist.back().first;
  
      // Enumerate operands until we hit a new node.  We need to traverse these
      // nodes' operands before visiting the rest of N's operands.
      MDNode::op_iterator I = std::find_if(
          Worklist.back().second, N->op_end(),
          [&](const Metadata *MD) { return enumerateMetadataImpl(F, MD); });
      if (I != N->op_end()) {
        auto *Op = cast<MDNode>(*I);
        Worklist.back().second = ++I;
  
        // Delay traversing Op if it's a distinct node and N is uniqued.
        if (Op->isDistinct() && !N->isDistinct())
          DelayedDistinctNodes.push_back(Op);
        else
          Worklist.push_back(std::make_pair(Op, Op->op_begin()));
        continue;
      }
  
      // All the operands have been visited.  Now assign an ID.
      Worklist.pop_back();
      MDs.push_back(N);
      MetadataMap[N].ID = MDs.size();
  
      // Flush out any delayed distinct nodes; these are all the distinct nodes
      // that are leaves in last uniqued subgraph.
      if (Worklist.empty() || Worklist.back().first->isDistinct()) {
        for (const MDNode *N : DelayedDistinctNodes)
          Worklist.push_back(std::make_pair(N, N->op_begin()));
        DelayedDistinctNodes.clear();
      }
    }
  }
  
  const MDNode *ValueEnumerator::enumerateMetadataImpl(unsigned F, const Metadata *MD) {
    if (!MD)
      return nullptr;
  
    assert(
        (isa<MDNode>(MD) || isa<MDString>(MD) || isa<ConstantAsMetadata>(MD)) &&
        "Invalid metadata kind");
  
    auto Insertion = MetadataMap.insert(std::make_pair(MD, MDIndex(F)));
    MDIndex &Entry = Insertion.first->second;
    if (!Insertion.second) {
      // Already mapped.  If F doesn't match the function tag, drop it.
      if (Entry.hasDifferentFunction(F))
        dropFunctionFromMetadata(*Insertion.first);
      return nullptr;
    }
  
    // Don't assign IDs to metadata nodes.
    if (auto *N = dyn_cast<MDNode>(MD))
      return N;
  
    // Save the metadata.
    MDs.push_back(MD);
    Entry.ID = MDs.size();
  
    // Enumerate the constant, if any.
    if (auto *C = dyn_cast<ConstantAsMetadata>(MD))
      EnumerateValue(C->getValue());
  
    return nullptr;
  }
  
  /// EnumerateFunctionLocalMetadataa - Incorporate function-local metadata
  /// information reachable from the metadata.
  void ValueEnumerator::EnumerateFunctionLocalMetadata(
      unsigned F, const LocalAsMetadata *Local) {
    assert(F && "Expected a function");
  
    // Check to see if it's already in!
    MDIndex &Index = MetadataMap[Local];
    if (Index.ID) {
      assert(Index.F == F && "Expected the same function");
      return;
    }
  
    MDs.push_back(Local);
    Index.F = F;
    Index.ID = MDs.size();
  
    EnumerateValue(Local->getValue());
  }
  
  static unsigned getMetadataTypeOrder(const Metadata *MD) {
    // Strings are emitted in bulk and must come first.
    if (isa<MDString>(MD))
      return 0;
  
    // ConstantAsMetadata doesn't reference anything.  We may as well shuffle it
    // to the front since we can detect it.
    auto *N = dyn_cast<MDNode>(MD);
    if (!N)
      return 1;
  
    // The reader is fast forward references for distinct node operands, but slow
    // when uniqued operands are unresolved.
    return N->isDistinct() ? 2 : 3;
  }
  
  void ValueEnumerator::organizeMetadata() {
    assert(MetadataMap.size() == MDs.size() &&
           "Metadata map and vector out of sync");
  
    if (MDs.empty())
      return;
  
    // Copy out the index information from MetadataMap in order to choose a new
    // order.
    SmallVector<MDIndex, 64> Order;
    Order.reserve(MetadataMap.size());
    for (const Metadata *MD : MDs)
      Order.push_back(MetadataMap.lookup(MD));
  
    // Partition:
    //   - by function, then
    //   - by isa<MDString>
    // and then sort by the original/current ID.  Since the IDs are guaranteed to
    // be unique, the result of std::sort will be deterministic.  There's no need
    // for std::stable_sort.
    llvm::sort(Order.begin(), Order.end(), [this](MDIndex LHS, MDIndex RHS) {
      return std::make_tuple(LHS.F, getMetadataTypeOrder(LHS.get(MDs)), LHS.ID) <
             std::make_tuple(RHS.F, getMetadataTypeOrder(RHS.get(MDs)), RHS.ID);
    });
  
    // Rebuild MDs, index the metadata ranges for each function in FunctionMDs,
    // and fix up MetadataMap.
    std::vector<const Metadata *> OldMDs = std::move(MDs);
    MDs.reserve(OldMDs.size());
    for (unsigned I = 0, E = Order.size(); I != E && !Order[I].F; ++I) {
      auto *MD = Order[I].get(OldMDs);
      MDs.push_back(MD);
      MetadataMap[MD].ID = I + 1;
      if (isa<MDString>(MD))
        ++NumMDStrings;
    }
  
    // Return early if there's nothing for the functions.
    if (MDs.size() == Order.size())
      return;
  
    // Build the function metadata ranges.
    MDRange R;
    FunctionMDs.reserve(OldMDs.size());
    unsigned PrevF = 0;
    for (unsigned I = MDs.size(), E = Order.size(), ID = MDs.size(); I != E;
         ++I) {
      unsigned F = Order[I].F;
      if (!PrevF) {
        PrevF = F;
      } else if (PrevF != F) {
        R.Last = FunctionMDs.size();
        std::swap(R, FunctionMDInfo[PrevF]);
        R.First = FunctionMDs.size();
  
        ID = MDs.size();
        PrevF = F;
      }
  
      auto *MD = Order[I].get(OldMDs);
      FunctionMDs.push_back(MD);
      MetadataMap[MD].ID = ++ID;
      if (isa<MDString>(MD))
        ++R.NumStrings;
    }
    R.Last = FunctionMDs.size();
    FunctionMDInfo[PrevF] = R;
  }
  
  void ValueEnumerator::incorporateFunctionMetadata(const Function &F) {
    NumModuleMDs = MDs.size();
  
    auto R = FunctionMDInfo.lookup(getValueID(&F) + 1);
    NumMDStrings = R.NumStrings;
    MDs.insert(MDs.end(), FunctionMDs.begin() + R.First,
               FunctionMDs.begin() + R.Last);
  }
  
  void ValueEnumerator::EnumerateValue(const Value *V) {
    assert(!V->getType()->isVoidTy() && "Can't insert void values!");
    assert(!isa<MetadataAsValue>(V) && "EnumerateValue doesn't handle Metadata!");
  
    // Check to see if it's already in!
    unsigned &ValueID = ValueMap[V];
    if (ValueID) {
      // Increment use count.
      Values[ValueID-1].second++;
      return;
    }
  
    if (auto *GO = dyn_cast<GlobalObject>(V))
      if (const Comdat *C = GO->getComdat())
        Comdats.insert(C);
  
    // Enumerate the type of this value.
    EnumerateType(V->getType());
  
    if (const Constant *C = dyn_cast<Constant>(V)) {
      if (isa<GlobalValue>(C)) {
        // Initializers for globals are handled explicitly elsewhere.
      } else if (C->getNumOperands()) {
        // If a constant has operands, enumerate them.  This makes sure that if a
        // constant has uses (for example an array of const ints), that they are
        // inserted also.
  
        // We prefer to enumerate them with values before we enumerate the user
        // itself.  This makes it more likely that we can avoid forward references
        // in the reader.  We know that there can be no cycles in the constants
        // graph that don't go through a global variable.
        for (User::const_op_iterator I = C->op_begin(), E = C->op_end();
             I != E; ++I)
          if (!isa<BasicBlock>(*I)) // Don't enumerate BB operand to BlockAddress.
            EnumerateValue(*I);
  
        // Finally, add the value.  Doing this could make the ValueID reference be
        // dangling, don't reuse it.
        Values.push_back(std::make_pair(V, 1U));
        ValueMap[V] = Values.size();
        return;
      }
    }
  
    // Add the value.
    Values.push_back(std::make_pair(V, 1U));
    ValueID = Values.size();
  }
  
  
  void ValueEnumerator::EnumerateType(Type *Ty) {
    unsigned *TypeID = &TypeMap[Ty];
  
    // We've already seen this type.
    if (*TypeID)
      return;
  
    // If it is a non-anonymous struct, mark the type as being visited so that we
    // don't recursively visit it.  This is safe because we allow forward
    // references of these in the bitcode reader.
    if (StructType *STy = dyn_cast<StructType>(Ty))
      if (!STy->isLiteral())
        *TypeID = ~0U;
  
    // Enumerate all of the subtypes before we enumerate this type.  This ensures
    // that the type will be enumerated in an order that can be directly built.
    for (Type *SubTy : Ty->subtypes())
      EnumerateType(SubTy);
  
    // Refresh the TypeID pointer in case the table rehashed.
    TypeID = &TypeMap[Ty];
  
    // Check to see if we got the pointer another way.  This can happen when
    // enumerating recursive types that hit the base case deeper than they start.
    //
    // If this is actually a struct that we are treating as forward ref'able,
    // then emit the definition now that all of its contents are available.
    if (*TypeID && *TypeID != ~0U)
      return;
  
    // Add this type now that its contents are all happily enumerated.
    Types.push_back(Ty);
  
    *TypeID = Types.size();
  }
  
  // Enumerate the types for the specified value.  If the value is a constant,
  // walk through it, enumerating the types of the constant.
  void ValueEnumerator::EnumerateOperandType(const Value *V) {
    EnumerateType(V->getType());
  
    assert(!isa<MetadataAsValue>(V) && "Unexpected metadata operand");
  
    const Constant *C = dyn_cast<Constant>(V);
    if (!C)
      return;
  
    // If this constant is already enumerated, ignore it, we know its type must
    // be enumerated.
    if (ValueMap.count(C))
      return;
  
    // This constant may have operands, make sure to enumerate the types in
    // them.
    for (const Value *Op : C->operands()) {
      // Don't enumerate basic blocks here, this happens as operands to
      // blockaddress.
      if (isa<BasicBlock>(Op))
        continue;
  
      EnumerateOperandType(Op);
    }
  }
  
  void ValueEnumerator::EnumerateAttributes(AttributeList PAL) {
    if (PAL.isEmpty()) return;  // null is always 0.
  
    // Do a lookup.
    unsigned &Entry = AttributeListMap[PAL];
    if (Entry == 0) {
      // Never saw this before, add it.
      AttributeLists.push_back(PAL);
      Entry = AttributeLists.size();
    }
  
    // Do lookups for all attribute groups.
    for (unsigned i = PAL.index_begin(), e = PAL.index_end(); i != e; ++i) {
      AttributeSet AS = PAL.getAttributes(i);
      if (!AS.hasAttributes())
        continue;
      IndexAndAttrSet Pair = {i, AS};
      unsigned &Entry = AttributeGroupMap[Pair];
      if (Entry == 0) {
        AttributeGroups.push_back(Pair);
        Entry = AttributeGroups.size();
      }
    }
  }
  
  void ValueEnumerator::incorporateFunction(const Function &F) {
    InstructionCount = 0;
    NumModuleValues = Values.size();
  
    // Add global metadata to the function block.  This doesn't include
    // LocalAsMetadata.
    incorporateFunctionMetadata(F);
  
    // Adding function arguments to the value table.
    for (const auto &I : F.args())
      EnumerateValue(&I);
  
    FirstFuncConstantID = Values.size();
  
    // Add all function-level constants to the value table.
    for (const BasicBlock &BB : F) {
      for (const Instruction &I : BB)
        for (const Use &OI : I.operands()) {
          if ((isa<Constant>(OI) && !isa<GlobalValue>(OI)) || isa<InlineAsm>(OI))
            EnumerateValue(OI);
        }
      BasicBlocks.push_back(&BB);
      ValueMap[&BB] = BasicBlocks.size();
    }
  
    // Optimize the constant layout.
    OptimizeConstants(FirstFuncConstantID, Values.size());
  
    // Add the function's parameter attributes so they are available for use in
    // the function's instruction.
    EnumerateAttributes(F.getAttributes());
  
    FirstInstID = Values.size();
  
    SmallVector<LocalAsMetadata *, 8> FnLocalMDVector;
    // Add all of the instructions.
    for (const BasicBlock &BB : F) {
      for (const Instruction &I : BB) {
        for (const Use &OI : I.operands()) {
          if (auto *MD = dyn_cast<MetadataAsValue>(&OI))
            if (auto *Local = dyn_cast<LocalAsMetadata>(MD->getMetadata()))
              // Enumerate metadata after the instructions they might refer to.
              FnLocalMDVector.push_back(Local);
        }
  
        if (!I.getType()->isVoidTy())
          EnumerateValue(&I);
      }
    }
  
    // Add all of the function-local metadata.
    for (unsigned i = 0, e = FnLocalMDVector.size(); i != e; ++i) {
      // At this point, every local values have been incorporated, we shouldn't
      // have a metadata operand that references a value that hasn't been seen.
      assert(ValueMap.count(FnLocalMDVector[i]->getValue()) &&
             "Missing value for metadata operand");
      EnumerateFunctionLocalMetadata(F, FnLocalMDVector[i]);
    }
  }
  
  void ValueEnumerator::purgeFunction() {
    /// Remove purged values from the ValueMap.
    for (unsigned i = NumModuleValues, e = Values.size(); i != e; ++i)
      ValueMap.erase(Values[i].first);
    for (unsigned i = NumModuleMDs, e = MDs.size(); i != e; ++i)
      MetadataMap.erase(MDs[i]);
    for (unsigned i = 0, e = BasicBlocks.size(); i != e; ++i)
      ValueMap.erase(BasicBlocks[i]);
  
    Values.resize(NumModuleValues);
    MDs.resize(NumModuleMDs);
    BasicBlocks.clear();
    NumMDStrings = 0;
  }
  
  static void IncorporateFunctionInfoGlobalBBIDs(const Function *F,
                                   DenseMap<const BasicBlock*, unsigned> &IDMap) {
    unsigned Counter = 0;
    for (const BasicBlock &BB : *F)
      IDMap[&BB] = ++Counter;
  }
  
  /// getGlobalBasicBlockID - This returns the function-specific ID for the
  /// specified basic block.  This is relatively expensive information, so it
  /// should only be used by rare constructs such as address-of-label.
  unsigned ValueEnumerator::getGlobalBasicBlockID(const BasicBlock *BB) const {
    unsigned &Idx = GlobalBasicBlockIDs[BB];
    if (Idx != 0)
      return Idx-1;
  
    IncorporateFunctionInfoGlobalBBIDs(BB->getParent(), GlobalBasicBlockIDs);
    return getGlobalBasicBlockID(BB);
  }
  
  uint64_t ValueEnumerator::computeBitsRequiredForTypeIndicies() const {
    return Log2_32_Ceil(getTypes().size() + 1);
  }
  