YQ Connector: support managed ClickHouse

Со стороны dqrun можно обратиться к инстансу коннектора, который работает на streaming стенде, и извлечь данные из облачного CH.

1 files changed, 629 insertions, 0 deletions

diff --git a/contrib/libs/llvm14/lib/Linker/LinkModules.cpp b/contrib/libs/llvm14/lib/Linker/LinkModules.cpp
new file mode 100644
index 0000000000..f9f51bf17d
--- /dev/null
+++ b/contrib/libs/llvm14/lib/Linker/LinkModules.cpp
@@ -0,0 +1,629 @@
+//===- lib/Linker/LinkModules.cpp - Module Linker Implementation ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the LLVM module linker.
+//
+//===----------------------------------------------------------------------===//
+
+#include "LinkDiagnosticInfo.h"
+#include "llvm-c/Linker.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/IR/Comdat.h"
+#include "llvm/IR/DiagnosticPrinter.h"
+#include "llvm/IR/GlobalValue.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Linker/Linker.h"
+#include "llvm/Support/Error.h"
+using namespace llvm;
+
+namespace {
+
+enum class LinkFrom { Dst, Src, Both };
+
+/// This is an implementation class for the LinkModules function, which is the
+/// entrypoint for this file.
+class ModuleLinker {
+  IRMover &Mover;
+  std::unique_ptr<Module> SrcM;
+
+  SetVector<GlobalValue *> ValuesToLink;
+
+  /// For symbol clashes, prefer those from Src.
+  unsigned Flags;
+
+  /// List of global value names that should be internalized.
+  StringSet<> Internalize;
+
+  /// Function that will perform the actual internalization. The reason for a
+  /// callback is that the linker cannot call internalizeModule without
+  /// creating a circular dependency between IPO and the linker.
+  std::function<void(Module &, const StringSet<> &)> InternalizeCallback;
+
+  /// Used as the callback for lazy linking.
+  /// The mover has just hit GV and we have to decide if it, and other members
+  /// of the same comdat, should be linked. Every member to be linked is passed
+  /// to Add.
+  void addLazyFor(GlobalValue &GV, const IRMover::ValueAdder &Add);
+
+  bool shouldOverrideFromSrc() { return Flags & Linker::OverrideFromSrc; }
+  bool shouldLinkOnlyNeeded() { return Flags & Linker::LinkOnlyNeeded; }
+
+  bool shouldLinkFromSource(bool &LinkFromSrc, const GlobalValue &Dest,
+                            const GlobalValue &Src);
+
+  /// Should we have mover and linker error diag info?
+  bool emitError(const Twine &Message) {
+    SrcM->getContext().diagnose(LinkDiagnosticInfo(DS_Error, Message));
+    return true;
+  }
+
+  bool getComdatLeader(Module &M, StringRef ComdatName,
+                       const GlobalVariable *&GVar);
+  bool computeResultingSelectionKind(StringRef ComdatName,
+                                     Comdat::SelectionKind Src,
+                                     Comdat::SelectionKind Dst,
+                                     Comdat::SelectionKind &Result,
+                                     LinkFrom &From);
+  DenseMap<const Comdat *, std::pair<Comdat::SelectionKind, LinkFrom>>
+      ComdatsChosen;
+  bool getComdatResult(const Comdat *SrcC, Comdat::SelectionKind &SK,
+                       LinkFrom &From);
+  // Keep track of the lazy linked global members of each comdat in source.
+  DenseMap<const Comdat *, std::vector<GlobalValue *>> LazyComdatMembers;
+
+  /// Given a global in the source module, return the global in the
+  /// destination module that is being linked to, if any.
+  GlobalValue *getLinkedToGlobal(const GlobalValue *SrcGV) {
+    Module &DstM = Mover.getModule();
+    // If the source has no name it can't link.  If it has local linkage,
+    // there is no name match-up going on.
+    if (!SrcGV->hasName() || GlobalValue::isLocalLinkage(SrcGV->getLinkage()))
+      return nullptr;
+
+    // Otherwise see if we have a match in the destination module's symtab.
+    GlobalValue *DGV = DstM.getNamedValue(SrcGV->getName());
+    if (!DGV)
+      return nullptr;
+
+    // If we found a global with the same name in the dest module, but it has
+    // internal linkage, we are really not doing any linkage here.
+    if (DGV->hasLocalLinkage())
+      return nullptr;
+
+    // Otherwise, we do in fact link to the destination global.
+    return DGV;
+  }
+
+  /// Drop GV if it is a member of a comdat that we are dropping.
+  /// This can happen with COFF's largest selection kind.
+  void dropReplacedComdat(GlobalValue &GV,
+                          const DenseSet<const Comdat *> &ReplacedDstComdats);
+
+  bool linkIfNeeded(GlobalValue &GV, SmallVectorImpl<GlobalValue *> &GVToClone);
+
+public:
+  ModuleLinker(IRMover &Mover, std::unique_ptr<Module> SrcM, unsigned Flags,
+               std::function<void(Module &, const StringSet<> &)>
+                   InternalizeCallback = {})
+      : Mover(Mover), SrcM(std::move(SrcM)), Flags(Flags),
+        InternalizeCallback(std::move(InternalizeCallback)) {}
+
+  bool run();
+};
+} // namespace
+
+static GlobalValue::VisibilityTypes
+getMinVisibility(GlobalValue::VisibilityTypes A,
+                 GlobalValue::VisibilityTypes B) {
+  if (A == GlobalValue::HiddenVisibility || B == GlobalValue::HiddenVisibility)
+    return GlobalValue::HiddenVisibility;
+  if (A == GlobalValue::ProtectedVisibility ||
+      B == GlobalValue::ProtectedVisibility)
+    return GlobalValue::ProtectedVisibility;
+  return GlobalValue::DefaultVisibility;
+}
+
+bool ModuleLinker::getComdatLeader(Module &M, StringRef ComdatName,
+                                   const GlobalVariable *&GVar) {
+  const GlobalValue *GVal = M.getNamedValue(ComdatName);
+  if (const auto *GA = dyn_cast_or_null<GlobalAlias>(GVal)) {
+    GVal = GA->getAliaseeObject();
+    if (!GVal)
+      // We cannot resolve the size of the aliasee yet.
+      return emitError("Linking COMDATs named '" + ComdatName +
+                       "': COMDAT key involves incomputable alias size.");
+  }
+
+  GVar = dyn_cast_or_null<GlobalVariable>(GVal);
+  if (!GVar)
+    return emitError(
+        "Linking COMDATs named '" + ComdatName +
+        "': GlobalVariable required for data dependent selection!");
+
+  return false;
+}
+
+bool ModuleLinker::computeResultingSelectionKind(StringRef ComdatName,
+                                                 Comdat::SelectionKind Src,
+                                                 Comdat::SelectionKind Dst,
+                                                 Comdat::SelectionKind &Result,
+                                                 LinkFrom &From) {
+  Module &DstM = Mover.getModule();
+  // The ability to mix Comdat::SelectionKind::Any with
+  // Comdat::SelectionKind::Largest is a behavior that comes from COFF.
+  bool DstAnyOrLargest = Dst == Comdat::SelectionKind::Any ||
+                         Dst == Comdat::SelectionKind::Largest;
+  bool SrcAnyOrLargest = Src == Comdat::SelectionKind::Any ||
+                         Src == Comdat::SelectionKind::Largest;
+  if (DstAnyOrLargest && SrcAnyOrLargest) {
+    if (Dst == Comdat::SelectionKind::Largest ||
+        Src == Comdat::SelectionKind::Largest)
+      Result = Comdat::SelectionKind::Largest;
+    else
+      Result = Comdat::SelectionKind::Any;
+  } else if (Src == Dst) {
+    Result = Dst;
+  } else {
+    return emitError("Linking COMDATs named '" + ComdatName +
+                     "': invalid selection kinds!");
+  }
+
+  switch (Result) {
+  case Comdat::SelectionKind::Any:
+    // Go with Dst.
+    From = LinkFrom::Dst;
+    break;
+  case Comdat::SelectionKind::NoDeduplicate:
+    From = LinkFrom::Both;
+    break;
+  case Comdat::SelectionKind::ExactMatch:
+  case Comdat::SelectionKind::Largest:
+  case Comdat::SelectionKind::SameSize: {
+    const GlobalVariable *DstGV;
+    const GlobalVariable *SrcGV;
+    if (getComdatLeader(DstM, ComdatName, DstGV) ||
+        getComdatLeader(*SrcM, ComdatName, SrcGV))
+      return true;
+
+    const DataLayout &DstDL = DstM.getDataLayout();
+    const DataLayout &SrcDL = SrcM->getDataLayout();
+    uint64_t DstSize = DstDL.getTypeAllocSize(DstGV->getValueType());
+    uint64_t SrcSize = SrcDL.getTypeAllocSize(SrcGV->getValueType());
+    if (Result == Comdat::SelectionKind::ExactMatch) {
+      if (SrcGV->getInitializer() != DstGV->getInitializer())
+        return emitError("Linking COMDATs named '" + ComdatName +
+                         "': ExactMatch violated!");
+      From = LinkFrom::Dst;
+    } else if (Result == Comdat::SelectionKind::Largest) {
+      From = SrcSize > DstSize ? LinkFrom::Src : LinkFrom::Dst;
+    } else if (Result == Comdat::SelectionKind::SameSize) {
+      if (SrcSize != DstSize)
+        return emitError("Linking COMDATs named '" + ComdatName +
+                         "': SameSize violated!");
+      From = LinkFrom::Dst;
+    } else {
+      llvm_unreachable("unknown selection kind");
+    }
+    break;
+  }
+  }
+
+  return false;
+}
+
+bool ModuleLinker::getComdatResult(const Comdat *SrcC,
+                                   Comdat::SelectionKind &Result,
+                                   LinkFrom &From) {
+  Module &DstM = Mover.getModule();
+  Comdat::SelectionKind SSK = SrcC->getSelectionKind();
+  StringRef ComdatName = SrcC->getName();
+  Module::ComdatSymTabType &ComdatSymTab = DstM.getComdatSymbolTable();
+  Module::ComdatSymTabType::iterator DstCI = ComdatSymTab.find(ComdatName);
+
+  if (DstCI == ComdatSymTab.end()) {
+    // Use the comdat if it is only available in one of the modules.
+    From = LinkFrom::Src;
+    Result = SSK;
+    return false;
+  }
+
+  const Comdat *DstC = &DstCI->second;
+  Comdat::SelectionKind DSK = DstC->getSelectionKind();
+  return computeResultingSelectionKind(ComdatName, SSK, DSK, Result, From);
+}
+
+bool ModuleLinker::shouldLinkFromSource(bool &LinkFromSrc,
+                                        const GlobalValue &Dest,
+                                        const GlobalValue &Src) {
+
+  // Should we unconditionally use the Src?
+  if (shouldOverrideFromSrc()) {
+    LinkFromSrc = true;
+    return false;
+  }
+
+  // We always have to add Src if it has appending linkage.
+  if (Src.hasAppendingLinkage() || Dest.hasAppendingLinkage()) {
+    LinkFromSrc = true;
+    return false;
+  }
+
+  bool SrcIsDeclaration = Src.isDeclarationForLinker();
+  bool DestIsDeclaration = Dest.isDeclarationForLinker();
+
+  if (SrcIsDeclaration) {
+    // If Src is external or if both Src & Dest are external..  Just link the
+    // external globals, we aren't adding anything.
+    if (Src.hasDLLImportStorageClass()) {
+      // If one of GVs is marked as DLLImport, result should be dllimport'ed.
+      LinkFromSrc = DestIsDeclaration;
+      return false;
+    }
+    // If the Dest is weak, use the source linkage.
+    if (Dest.hasExternalWeakLinkage()) {
+      LinkFromSrc = true;
+      return false;
+    }
+    // Link an available_externally over a declaration.
+    LinkFromSrc = !Src.isDeclaration() && Dest.isDeclaration();
+    return false;
+  }
+
+  if (DestIsDeclaration) {
+    // If Dest is external but Src is not:
+    LinkFromSrc = true;
+    return false;
+  }
+
+  if (Src.hasCommonLinkage()) {
+    if (Dest.hasLinkOnceLinkage() || Dest.hasWeakLinkage()) {
+      LinkFromSrc = true;
+      return false;
+    }
+
+    if (!Dest.hasCommonLinkage()) {
+      LinkFromSrc = false;
+      return false;
+    }
+
+    const DataLayout &DL = Dest.getParent()->getDataLayout();
+    uint64_t DestSize = DL.getTypeAllocSize(Dest.getValueType());
+    uint64_t SrcSize = DL.getTypeAllocSize(Src.getValueType());
+    LinkFromSrc = SrcSize > DestSize;
+    return false;
+  }
+
+  if (Src.isWeakForLinker()) {
+    assert(!Dest.hasExternalWeakLinkage());
+    assert(!Dest.hasAvailableExternallyLinkage());
+
+    if (Dest.hasLinkOnceLinkage() && Src.hasWeakLinkage()) {
+      LinkFromSrc = true;
+      return false;
+    }
+
+    LinkFromSrc = false;
+    return false;
+  }
+
+  if (Dest.isWeakForLinker()) {
+    assert(Src.hasExternalLinkage());
+    LinkFromSrc = true;
+    return false;
+  }
+
+  assert(!Src.hasExternalWeakLinkage());
+  assert(!Dest.hasExternalWeakLinkage());
+  assert(Dest.hasExternalLinkage() && Src.hasExternalLinkage() &&
+         "Unexpected linkage type!");
+  return emitError("Linking globals named '" + Src.getName() +
+                   "': symbol multiply defined!");
+}
+
+bool ModuleLinker::linkIfNeeded(GlobalValue &GV,
+                                SmallVectorImpl<GlobalValue *> &GVToClone) {
+  GlobalValue *DGV = getLinkedToGlobal(&GV);
+
+  if (shouldLinkOnlyNeeded()) {
+    // Always import variables with appending linkage.
+    if (!GV.hasAppendingLinkage()) {
+      // Don't import globals unless they are referenced by the destination
+      // module.
+      if (!DGV)
+        return false;
+      // Don't import globals that are already defined in the destination module
+      if (!DGV->isDeclaration())
+        return false;
+    }
+  }
+
+  if (DGV && !GV.hasLocalLinkage() && !GV.hasAppendingLinkage()) {
+    auto *DGVar = dyn_cast<GlobalVariable>(DGV);
+    auto *SGVar = dyn_cast<GlobalVariable>(&GV);
+    if (DGVar && SGVar) {
+      if (DGVar->isDeclaration() && SGVar->isDeclaration() &&
+          (!DGVar->isConstant() || !SGVar->isConstant())) {
+        DGVar->setConstant(false);
+        SGVar->setConstant(false);
+      }
+      if (DGVar->hasCommonLinkage() && SGVar->hasCommonLinkage()) {
+        MaybeAlign Align(
+            std::max(DGVar->getAlignment(), SGVar->getAlignment()));
+        SGVar->setAlignment(Align);
+        DGVar->setAlignment(Align);
+      }
+    }
+
+    GlobalValue::VisibilityTypes Visibility =
+        getMinVisibility(DGV->getVisibility(), GV.getVisibility());
+    DGV->setVisibility(Visibility);
+    GV.setVisibility(Visibility);
+
+    GlobalValue::UnnamedAddr UnnamedAddr = GlobalValue::getMinUnnamedAddr(
+        DGV->getUnnamedAddr(), GV.getUnnamedAddr());
+    DGV->setUnnamedAddr(UnnamedAddr);
+    GV.setUnnamedAddr(UnnamedAddr);
+  }
+
+  if (!DGV && !shouldOverrideFromSrc() &&
+      (GV.hasLocalLinkage() || GV.hasLinkOnceLinkage() ||
+       GV.hasAvailableExternallyLinkage()))
+    return false;
+
+  if (GV.isDeclaration())
+    return false;
+
+  LinkFrom ComdatFrom = LinkFrom::Dst;
+  if (const Comdat *SC = GV.getComdat()) {
+    std::tie(std::ignore, ComdatFrom) = ComdatsChosen[SC];
+    if (ComdatFrom == LinkFrom::Dst)
+      return false;
+  }
+
+  bool LinkFromSrc = true;
+  if (DGV && shouldLinkFromSource(LinkFromSrc, *DGV, GV))
+    return true;
+  if (DGV && ComdatFrom == LinkFrom::Both)
+    GVToClone.push_back(LinkFromSrc ? DGV : &GV);
+  if (LinkFromSrc)
+    ValuesToLink.insert(&GV);
+  return false;
+}
+
+void ModuleLinker::addLazyFor(GlobalValue &GV, const IRMover::ValueAdder &Add) {
+  // Add these to the internalize list
+  if (!GV.hasLinkOnceLinkage() && !GV.hasAvailableExternallyLinkage() &&
+      !shouldLinkOnlyNeeded())
+    return;
+
+  if (InternalizeCallback)
+    Internalize.insert(GV.getName());
+  Add(GV);
+
+  const Comdat *SC = GV.getComdat();
+  if (!SC)
+    return;
+  for (GlobalValue *GV2 : LazyComdatMembers[SC]) {
+    GlobalValue *DGV = getLinkedToGlobal(GV2);
+    bool LinkFromSrc = true;
+    if (DGV && shouldLinkFromSource(LinkFromSrc, *DGV, *GV2))
+      return;
+    if (!LinkFromSrc)
+      continue;
+    if (InternalizeCallback)
+      Internalize.insert(GV2->getName());
+    Add(*GV2);
+  }
+}
+
+void ModuleLinker::dropReplacedComdat(
+    GlobalValue &GV, const DenseSet<const Comdat *> &ReplacedDstComdats) {
+  Comdat *C = GV.getComdat();
+  if (!C)
+    return;
+  if (!ReplacedDstComdats.count(C))
+    return;
+  if (GV.use_empty()) {
+    GV.eraseFromParent();
+    return;
+  }
+
+  if (auto *F = dyn_cast<Function>(&GV)) {
+    F->deleteBody();
+  } else if (auto *Var = dyn_cast<GlobalVariable>(&GV)) {
+    Var->setInitializer(nullptr);
+  } else {
+    auto &Alias = cast<GlobalAlias>(GV);
+    Module &M = *Alias.getParent();
+    GlobalValue *Declaration;
+    if (auto *FTy = dyn_cast<FunctionType>(Alias.getValueType())) {
+      Declaration = Function::Create(FTy, GlobalValue::ExternalLinkage, "", &M);
+    } else {
+      Declaration =
+          new GlobalVariable(M, Alias.getValueType(), /*isConstant*/ false,
+                             GlobalValue::ExternalLinkage,
+                             /*Initializer*/ nullptr);
+    }
+    Declaration->takeName(&Alias);
+    Alias.replaceAllUsesWith(Declaration);
+    Alias.eraseFromParent();
+  }
+}
+
+bool ModuleLinker::run() {
+  Module &DstM = Mover.getModule();
+  DenseSet<const Comdat *> ReplacedDstComdats;
+
+  for (const auto &SMEC : SrcM->getComdatSymbolTable()) {
+    const Comdat &C = SMEC.getValue();
+    if (ComdatsChosen.count(&C))
+      continue;
+    Comdat::SelectionKind SK;
+    LinkFrom From;
+    if (getComdatResult(&C, SK, From))
+      return true;
+    ComdatsChosen[&C] = std::make_pair(SK, From);
+
+    if (From != LinkFrom::Src)
+      continue;
+
+    Module::ComdatSymTabType &ComdatSymTab = DstM.getComdatSymbolTable();
+    Module::ComdatSymTabType::iterator DstCI = ComdatSymTab.find(C.getName());
+    if (DstCI == ComdatSymTab.end())
+      continue;
+
+    // The source comdat is replacing the dest one.
+    const Comdat *DstC = &DstCI->second;
+    ReplacedDstComdats.insert(DstC);
+  }
+
+  // Alias have to go first, since we are not able to find their comdats
+  // otherwise.
+  for (GlobalAlias &GV : llvm::make_early_inc_range(DstM.aliases()))
+    dropReplacedComdat(GV, ReplacedDstComdats);
+
+  for (GlobalVariable &GV : llvm::make_early_inc_range(DstM.globals()))
+    dropReplacedComdat(GV, ReplacedDstComdats);
+
+  for (Function &GV : llvm::make_early_inc_range(DstM))
+    dropReplacedComdat(GV, ReplacedDstComdats);
+
+  for (GlobalVariable &GV : SrcM->globals())
+    if (GV.hasLinkOnceLinkage())
+      if (const Comdat *SC = GV.getComdat())
+        LazyComdatMembers[SC].push_back(&GV);
+
+  for (Function &SF : *SrcM)
+    if (SF.hasLinkOnceLinkage())
+      if (const Comdat *SC = SF.getComdat())
+        LazyComdatMembers[SC].push_back(&SF);
+
+  for (GlobalAlias &GA : SrcM->aliases())
+    if (GA.hasLinkOnceLinkage())
+      if (const Comdat *SC = GA.getComdat())
+        LazyComdatMembers[SC].push_back(&GA);
+
+  // Insert all of the globals in src into the DstM module... without linking
+  // initializers (which could refer to functions not yet mapped over).
+  SmallVector<GlobalValue *, 0> GVToClone;
+  for (GlobalVariable &GV : SrcM->globals())
+    if (linkIfNeeded(GV, GVToClone))
+      return true;
+
+  for (Function &SF : *SrcM)
+    if (linkIfNeeded(SF, GVToClone))
+      return true;
+
+  for (GlobalAlias &GA : SrcM->aliases())
+    if (linkIfNeeded(GA, GVToClone))
+      return true;
+
+  for (GlobalIFunc &GI : SrcM->ifuncs())
+    if (linkIfNeeded(GI, GVToClone))
+      return true;
+
+  // For a variable in a comdat nodeduplicate, its initializer should be
+  // preserved (its content may be implicitly used by other members) even if
+  // symbol resolution does not pick it. Clone it into an unnamed private
+  // variable.
+  for (GlobalValue *GV : GVToClone) {
+    if (auto *Var = dyn_cast<GlobalVariable>(GV)) {
+      auto *NewVar = new GlobalVariable(*Var->getParent(), Var->getValueType(),
+                                        Var->isConstant(), Var->getLinkage(),
+                                        Var->getInitializer());
+      NewVar->copyAttributesFrom(Var);
+      NewVar->setVisibility(GlobalValue::DefaultVisibility);
+      NewVar->setLinkage(GlobalValue::PrivateLinkage);
+      NewVar->setDSOLocal(true);
+      NewVar->setComdat(Var->getComdat());
+      if (Var->getParent() != &Mover.getModule())
+        ValuesToLink.insert(NewVar);
+    } else {
+      emitError("linking '" + GV->getName() +
+                "': non-variables in comdat nodeduplicate are not handled");
+    }
+  }
+
+  for (unsigned I = 0; I < ValuesToLink.size(); ++I) {
+    GlobalValue *GV = ValuesToLink[I];
+    const Comdat *SC = GV->getComdat();
+    if (!SC)
+      continue;
+    for (GlobalValue *GV2 : LazyComdatMembers[SC]) {
+      GlobalValue *DGV = getLinkedToGlobal(GV2);
+      bool LinkFromSrc = true;
+      if (DGV && shouldLinkFromSource(LinkFromSrc, *DGV, *GV2))
+        return true;
+      if (LinkFromSrc)
+        ValuesToLink.insert(GV2);
+    }
+  }
+
+  if (InternalizeCallback) {
+    for (GlobalValue *GV : ValuesToLink)
+      Internalize.insert(GV->getName());
+  }
+
+  // FIXME: Propagate Errors through to the caller instead of emitting
+  // diagnostics.
+  bool HasErrors = false;
+  if (Error E = Mover.move(std::move(SrcM), ValuesToLink.getArrayRef(),
+                           [this](GlobalValue &GV, IRMover::ValueAdder Add) {
+                             addLazyFor(GV, Add);
+                           },
+                           /* IsPerformingImport */ false)) {
+    handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
+      DstM.getContext().diagnose(LinkDiagnosticInfo(DS_Error, EIB.message()));
+      HasErrors = true;
+    });
+  }
+  if (HasErrors)
+    return true;
+
+  if (InternalizeCallback)
+    InternalizeCallback(DstM, Internalize);
+
+  return false;
+}
+
+Linker::Linker(Module &M) : Mover(M) {}
+
+bool Linker::linkInModule(
+    std::unique_ptr<Module> Src, unsigned Flags,
+    std::function<void(Module &, const StringSet<> &)> InternalizeCallback) {
+  ModuleLinker ModLinker(Mover, std::move(Src), Flags,
+                         std::move(InternalizeCallback));
+  return ModLinker.run();
+}
+
+//===----------------------------------------------------------------------===//
+// LinkModules entrypoint.
+//===----------------------------------------------------------------------===//
+
+/// This function links two modules together, with the resulting Dest module
+/// modified to be the composite of the two input modules. If an error occurs,
+/// true is returned and ErrorMsg (if not null) is set to indicate the problem.
+/// Upon failure, the Dest module could be in a modified state, and shouldn't be
+/// relied on to be consistent.
+bool Linker::linkModules(
+    Module &Dest, std::unique_ptr<Module> Src, unsigned Flags,
+    std::function<void(Module &, const StringSet<> &)> InternalizeCallback) {
+  Linker L(Dest);
+  return L.linkInModule(std::move(Src), Flags, std::move(InternalizeCallback));
+}
+
+//===----------------------------------------------------------------------===//
+// C API.
+//===----------------------------------------------------------------------===//
+
+LLVMBool LLVMLinkModules2(LLVMModuleRef Dest, LLVMModuleRef Src) {
+  Module *D = unwrap(Dest);
+  std::unique_ptr<Module> M(unwrap(Src));
+  return Linker::linkModules(*D, std::move(M));
+}