+namespace {
+struct OrderMap {
+ DenseMap<const Value *, std::pair<unsigned, bool>> IDs;
+ unsigned LastGlobalConstantID;
+ unsigned LastGlobalValueID;
+
+ OrderMap() : LastGlobalConstantID(0), LastGlobalValueID(0) {}
+
+ 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;
+ }
+};
+} // 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 Function &F : M) {
+ if (F.hasPrefixData())
+ if (!isa<GlobalValue>(F.getPrefixData()))
+ orderValue(F.getPrefixData(), OM);
+ if (F.hasPrologueData())
+ if (!isa<GlobalValue>(F.getPrologueData()))
+ orderValue(F.getPrologueData(), OM);
+ if (F.hasPersonalityFn())
+ if (!isa<GlobalValue>(F.getPersonalityFn()))
+ orderValue(F.getPersonalityFn(), 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 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.
+ typedef std::pair<const Use *, unsigned> Entry;
+ 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);
+ std::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;