[llvm] r255254 - Slit lib/Linker in two.

Rafael Espindola via llvm-commits llvm-commits at lists.llvm.org
Thu Dec 10 06:19:36 PST 2015


Author: rafael
Date: Thu Dec 10 08:19:35 2015
New Revision: 255254

URL: http://llvm.org/viewvc/llvm-project?rev=255254&view=rev
Log:
Slit lib/Linker in two.

A linker normally has two stages: symbol resolution and "moving stuff".

In lib/Linker there is the complication of lazy linking some globals,
but it was still far more mixed than it needed to.

This splits the linker into a lower level IRMover and the linker proper.
The IRMover just takes a list of globals to move and a callback that
lets the user control what is lazy linked.

The main motivation is that now tools/gold (and soon lld) can use their
own symbol resolution to instruct IRMover what to do.

Added:
    llvm/trunk/include/llvm/Linker/IRMover.h
    llvm/trunk/lib/Linker/IRMover.cpp
      - copied, changed from r255245, llvm/trunk/lib/Linker/LinkModules.cpp
    llvm/trunk/lib/Linker/LinkDiagnosticInfo.h
Modified:
    llvm/trunk/include/llvm/Linker/Linker.h
    llvm/trunk/lib/Linker/CMakeLists.txt
    llvm/trunk/lib/Linker/LinkModules.cpp
    llvm/trunk/test/Linker/alias.ll
    llvm/trunk/test/tools/gold/X86/drop-linkage.ll
    llvm/trunk/tools/gold/gold-plugin.cpp

Added: llvm/trunk/include/llvm/Linker/IRMover.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Linker/IRMover.h?rev=255254&view=auto
==============================================================================
--- llvm/trunk/include/llvm/Linker/IRMover.h (added)
+++ llvm/trunk/include/llvm/Linker/IRMover.h Thu Dec 10 08:19:35 2015
@@ -0,0 +1,78 @@
+//===- IRMover.h ------------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LINKER_IRMOVER_H
+#define LLVM_LINKER_IRMOVER_H
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/IR/DiagnosticInfo.h"
+
+namespace llvm {
+class GlobalValue;
+class Module;
+class StructType;
+class Type;
+
+class IRMover {
+  struct StructTypeKeyInfo {
+    struct KeyTy {
+      ArrayRef<Type *> ETypes;
+      bool IsPacked;
+      KeyTy(ArrayRef<Type *> E, bool P);
+      KeyTy(const StructType *ST);
+      bool operator==(const KeyTy &that) const;
+      bool operator!=(const KeyTy &that) const;
+    };
+    static StructType *getEmptyKey();
+    static StructType *getTombstoneKey();
+    static unsigned getHashValue(const KeyTy &Key);
+    static unsigned getHashValue(const StructType *ST);
+    static bool isEqual(const KeyTy &LHS, const StructType *RHS);
+    static bool isEqual(const StructType *LHS, const StructType *RHS);
+  };
+
+public:
+  class IdentifiedStructTypeSet {
+    // The set of opaque types is the composite module.
+    DenseSet<StructType *> OpaqueStructTypes;
+
+    // The set of identified but non opaque structures in the composite module.
+    DenseSet<StructType *, StructTypeKeyInfo> NonOpaqueStructTypes;
+
+  public:
+    void addNonOpaque(StructType *Ty);
+    void switchToNonOpaque(StructType *Ty);
+    void addOpaque(StructType *Ty);
+    StructType *findNonOpaque(ArrayRef<Type *> ETypes, bool IsPacked);
+    bool hasType(StructType *Ty);
+  };
+
+  IRMover(Module &M, DiagnosticHandlerFunction DiagnosticHandler);
+
+  typedef std::function<void(GlobalValue &)> ValueAdder;
+  /// Move in the provide values. The source is destroyed.
+  /// Returns true on error.
+  bool move(Module &Src, ArrayRef<GlobalValue *> ValuesToLink,
+            std::function<void(GlobalValue &GV, ValueAdder Add)> AddLazyFor);
+  Module &getModule() { return Composite; }
+
+  DiagnosticHandlerFunction getDiagnosticHandler() const {
+    return DiagnosticHandler;
+  }
+
+private:
+  Module &Composite;
+  IdentifiedStructTypeSet IdentifiedStructTypes;
+  DiagnosticHandlerFunction DiagnosticHandler;
+};
+
+} // End llvm namespace
+
+#endif

Modified: llvm/trunk/include/llvm/Linker/Linker.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Linker/Linker.h?rev=255254&r1=255253&r2=255254&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Linker/Linker.h (original)
+++ llvm/trunk/include/llvm/Linker/Linker.h Thu Dec 10 08:19:35 2015
@@ -10,11 +10,9 @@
 #ifndef LLVM_LINKER_LINKER_H
 #define LLVM_LINKER_LINKER_H
 
-#include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/DenseSet.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/FunctionInfo.h"
+#include "llvm/Linker/IRMover.h"
 
 namespace llvm {
 class Module;
@@ -26,41 +24,9 @@ class Type;
 /// module since it is assumed that the user of this class will want to do
 /// something with it after the linking.
 class Linker {
-public:
-  struct StructTypeKeyInfo {
-    struct KeyTy {
-      ArrayRef<Type *> ETypes;
-      bool IsPacked;
-      KeyTy(ArrayRef<Type *> E, bool P);
-      KeyTy(const StructType *ST);
-      bool operator==(const KeyTy &that) const;
-      bool operator!=(const KeyTy &that) const;
-    };
-    static StructType *getEmptyKey();
-    static StructType *getTombstoneKey();
-    static unsigned getHashValue(const KeyTy &Key);
-    static unsigned getHashValue(const StructType *ST);
-    static bool isEqual(const KeyTy &LHS, const StructType *RHS);
-    static bool isEqual(const StructType *LHS, const StructType *RHS);
-  };
-
-  typedef DenseSet<StructType *, StructTypeKeyInfo> NonOpaqueStructTypeSet;
-  typedef DenseSet<StructType *> OpaqueStructTypeSet;
-
-  struct IdentifiedStructTypeSet {
-    // The set of opaque types is the composite module.
-    OpaqueStructTypeSet OpaqueStructTypes;
-
-    // The set of identified but non opaque structures in the composite module.
-    NonOpaqueStructTypeSet NonOpaqueStructTypes;
-
-    void addNonOpaque(StructType *Ty);
-    void switchToNonOpaque(StructType *Ty);
-    void addOpaque(StructType *Ty);
-    StructType *findNonOpaque(ArrayRef<Type *> ETypes, bool IsPacked);
-    bool hasType(StructType *Ty);
-  };
+  IRMover Mover;
 
+public:
   enum Flags {
     None = 0,
     OverrideFromSrc = (1 << 0),
@@ -88,15 +54,8 @@ public:
                           unsigned Flags = Flags::None);
 
   DiagnosticHandlerFunction getDiagnosticHandler() const {
-    return DiagnosticHandler;
+    return Mover.getDiagnosticHandler();
   }
-
-private:
-  Module &Composite;
-
-  IdentifiedStructTypeSet IdentifiedStructTypes;
-
-  DiagnosticHandlerFunction DiagnosticHandler;
 };
 
 /// Create a new module with exported local functions renamed and promoted

Modified: llvm/trunk/lib/Linker/CMakeLists.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/CMakeLists.txt?rev=255254&r1=255253&r2=255254&view=diff
==============================================================================
--- llvm/trunk/lib/Linker/CMakeLists.txt (original)
+++ llvm/trunk/lib/Linker/CMakeLists.txt Thu Dec 10 08:19:35 2015
@@ -1,4 +1,5 @@
 add_llvm_library(LLVMLinker
+  IRMover.cpp
   LinkModules.cpp
 
   ADDITIONAL_HEADER_DIRS

Copied: llvm/trunk/lib/Linker/IRMover.cpp (from r255245, llvm/trunk/lib/Linker/LinkModules.cpp)
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/IRMover.cpp?p2=llvm/trunk/lib/Linker/IRMover.cpp&p1=llvm/trunk/lib/Linker/LinkModules.cpp&r1=255245&r2=255254&rev=255254&view=diff
==============================================================================
--- llvm/trunk/lib/Linker/LinkModules.cpp (original)
+++ llvm/trunk/lib/Linker/IRMover.cpp Thu Dec 10 08:19:35 2015
@@ -1,4 +1,4 @@
-//===- lib/Linker/LinkModules.cpp - Module Linker Implementation ----------===//
+//===- lib/Linker/IRMover.cpp ---------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -6,21 +6,14 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-//
-// This file implements the LLVM module linker.
-//
-//===----------------------------------------------------------------------===//
 
-#include "llvm/Linker/Linker.h"
-#include "llvm-c/Linker.h"
+#include "llvm/Linker/IRMover.h"
+#include "LinkDiagnosticInfo.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/IR/Constants.h"
-#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/Module.h"
 #include "llvm/IR/TypeFinder.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 using namespace llvm;
@@ -50,10 +43,10 @@ class TypeMapTy : public ValueMapTypeRem
   SmallPtrSet<StructType *, 16> DstResolvedOpaqueTypes;
 
 public:
-  TypeMapTy(Linker::IdentifiedStructTypeSet &DstStructTypesSet)
+  TypeMapTy(IRMover::IdentifiedStructTypeSet &DstStructTypesSet)
       : DstStructTypesSet(DstStructTypesSet) {}
 
-  Linker::IdentifiedStructTypeSet &DstStructTypesSet;
+  IRMover::IdentifiedStructTypeSet &DstStructTypesSet;
   /// Indicate that the specified type in the destination module is conceptually
   /// equivalent to the specified type in the source module.
   void addTypeMapping(Type *DstTy, Type *SrcTy);
@@ -73,17 +66,6 @@ public:
     return cast<FunctionType>(get((Type *)T));
   }
 
-  /// Dump out the type map for debugging purposes.
-  void dump() const {
-    for (auto &Pair : MappedTypes) {
-      dbgs() << "TypeMap: ";
-      Pair.first->print(dbgs());
-      dbgs() << " => ";
-      Pair.second->print(dbgs());
-      dbgs() << '\n';
-    }
-  }
-
 private:
   Type *remapType(Type *SrcTy) override { return get(SrcTy); }
 
@@ -345,73 +327,67 @@ Type *TypeMapTy::get(Type *Ty, SmallPtrS
   }
 }
 
+LinkDiagnosticInfo::LinkDiagnosticInfo(DiagnosticSeverity Severity,
+                                       const Twine &Msg)
+    : DiagnosticInfo(DK_Linker, Severity), Msg(Msg) {}
+void LinkDiagnosticInfo::print(DiagnosticPrinter &DP) const { DP << Msg; }
+
 //===----------------------------------------------------------------------===//
 // ModuleLinker implementation.
 //===----------------------------------------------------------------------===//
 
 namespace {
-class ModuleLinker;
+class IRLinker;
 
 /// Creates prototypes for functions that are lazily linked on the fly. This
 /// speeds up linking for modules with many/ lazily linked functions of which
 /// few get used.
-class ValueMaterializerTy final : public ValueMaterializer {
-  ModuleLinker *ModLinker;
+class GlobalValueMaterializer final : public ValueMaterializer {
+  IRLinker *ModLinker;
 
 public:
-  ValueMaterializerTy(ModuleLinker *ModLinker) : ModLinker(ModLinker) {}
-
+  GlobalValueMaterializer(IRLinker *ModLinker) : ModLinker(ModLinker) {}
   Value *materializeDeclFor(Value *V) override;
   void materializeInitFor(GlobalValue *New, GlobalValue *Old) override;
 };
 
-class LinkDiagnosticInfo : public DiagnosticInfo {
-  const Twine &Msg;
+class LocalValueMaterializer final : public ValueMaterializer {
+  IRLinker *ModLinker;
 
 public:
-  LinkDiagnosticInfo(DiagnosticSeverity Severity, const Twine &Msg);
-  void print(DiagnosticPrinter &DP) const override;
+  LocalValueMaterializer(IRLinker *ModLinker) : ModLinker(ModLinker) {}
+  Value *materializeDeclFor(Value *V) override;
+  void materializeInitFor(GlobalValue *New, GlobalValue *Old) override;
 };
-LinkDiagnosticInfo::LinkDiagnosticInfo(DiagnosticSeverity Severity,
-                                       const Twine &Msg)
-    : DiagnosticInfo(DK_Linker, Severity), Msg(Msg) {}
-void LinkDiagnosticInfo::print(DiagnosticPrinter &DP) const { DP << Msg; }
 
-/// This is an implementation class for the LinkModules function, which is the
-/// entrypoint for this file.
-class ModuleLinker {
+/// This is responsible for keeping track of the state used for moving data
+/// from SrcM to DstM.
+class IRLinker {
   Module &DstM;
   Module &SrcM;
 
+  std::function<void(GlobalValue &, IRMover::ValueAdder)> AddLazyFor;
+
   TypeMapTy TypeMap;
-  ValueMaterializerTy ValMaterializer;
+  GlobalValueMaterializer GValMaterializer;
+  LocalValueMaterializer LValMaterializer;
 
   /// Mapping of values from what they used to be in Src, to what they are now
   /// in DstM.  ValueToValueMapTy is a ValueMap, which involves some overhead
   /// due to the use of Value handles which the Linker doesn't actually need,
   /// but this allows us to reuse the ValueMapper code.
   ValueToValueMapTy ValueMap;
+  ValueToValueMapTy AliasValueMap;
 
-  SetVector<GlobalValue *> ValuesToLink;
+  DenseSet<GlobalValue *> ValuesToLink;
+  std::vector<GlobalValue *> Worklist;
 
-  DiagnosticHandlerFunction DiagnosticHandler;
-
-  /// For symbol clashes, prefer those from Src.
-  unsigned Flags;
+  void maybeAdd(GlobalValue *GV) {
+    if (ValuesToLink.insert(GV).second)
+      Worklist.push_back(GV);
+  }
 
-  /// Function index passed into ModuleLinker for using in function
-  /// importing/exporting handling.
-  const FunctionInfoIndex *ImportIndex;
-
-  /// Function to import from source module, all other functions are
-  /// imported as declarations instead of definitions.
-  DenseSet<const GlobalValue *> *ImportFunction;
-
-  /// Set to true if the given FunctionInfoIndex contains any functions
-  /// from this source module, in which case we must conservatively assume
-  /// that any of its functions may be imported into another module
-  /// as part of a different backend compilation process.
-  bool HasExportedFunctions = false;
+  DiagnosticHandlerFunction DiagnosticHandler;
 
   /// Set to true when all global value body linking is complete (including
   /// lazy linking). Used to prevent metadata linking from creating new
@@ -420,22 +396,10 @@ class ModuleLinker {
 
   bool HasError = false;
 
-  bool shouldOverrideFromSrc() { return Flags & Linker::OverrideFromSrc; }
-  bool shouldLinkOnlyNeeded() { return Flags & Linker::LinkOnlyNeeded; }
-  bool shouldInternalizeLinkedSymbols() {
-    return Flags & Linker::InternalizeLinkedSymbols;
-  }
-
   /// Handles cloning of a global values from the source module into
   /// the destination module, including setting the attributes and visibility.
   GlobalValue *copyGlobalValueProto(const GlobalValue *SGV, bool ForDefinition);
 
-  /// Check if we should promote the given local value to global scope.
-  bool doPromoteLocalToGlobal(const GlobalValue *SGV);
-
-  bool shouldLinkFromSource(bool &LinkFromSrc, const GlobalValue &Dest,
-                            const GlobalValue &Src);
-
   /// Helper method for setting a message and returning an error code.
   bool emitError(const Twine &Message) {
     DiagnosticHandler(LinkDiagnosticInfo(DS_Error, Message));
@@ -447,30 +411,16 @@ class ModuleLinker {
     DiagnosticHandler(LinkDiagnosticInfo(DS_Warning, Message));
   }
 
-  bool getComdatLeader(Module &M, StringRef ComdatName,
-                       const GlobalVariable *&GVar);
-  bool computeResultingSelectionKind(StringRef ComdatName,
-                                     Comdat::SelectionKind Src,
-                                     Comdat::SelectionKind Dst,
-                                     Comdat::SelectionKind &Result,
-                                     bool &LinkFromSrc);
-  std::map<const Comdat *, std::pair<Comdat::SelectionKind, bool>>
-      ComdatsChosen;
-  bool getComdatResult(const Comdat *SrcC, Comdat::SelectionKind &SK,
-                       bool &LinkFromSrc);
-  // Keep track of the global value members of each comdat in source.
-  DenseMap<const Comdat *, std::vector<GlobalValue *>> ComdatMembers;
-
   /// 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) {
     // 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(getLinkage(SrcGV)))
+    if (!SrcGV->hasName() || SrcGV->hasLocalLinkage())
       return nullptr;
 
     // Otherwise see if we have a match in the destination module's symtab.
-    GlobalValue *DGV = DstM.getNamedValue(getName(SrcGV));
+    GlobalValue *DGV = DstM.getNamedValue(SrcGV->getName());
     if (!DGV)
       return nullptr;
 
@@ -485,11 +435,12 @@ class ModuleLinker {
 
   void computeTypeMapping();
 
-  bool linkIfNeeded(GlobalValue &GV);
   Constant *linkAppendingVarProto(GlobalVariable *DstGV,
                                   const GlobalVariable *SrcGV);
 
-  Constant *linkGlobalValueProto(GlobalValue *GV);
+  bool shouldLink(GlobalValue *DGV, GlobalValue &SGV);
+  Constant *linkGlobalValueProto(GlobalValue *GV, bool ForAlias);
+
   bool linkModuleFlagsMetadata();
 
   void linkGlobalInit(GlobalVariable &Dst, GlobalVariable &Src);
@@ -503,58 +454,23 @@ class ModuleLinker {
   Function *copyFunctionProto(const Function *SF);
   GlobalValue *copyGlobalAliasProto(const GlobalAlias *SGA);
 
-  /// Helper methods to check if we are importing from or potentially
-  /// exporting from the current source module.
-  bool isPerformingImport() { return ImportFunction != nullptr; }
-  bool isModuleExporting() { return HasExportedFunctions; }
-
-  /// If we are importing from the source module, checks if we should
-  /// import SGV as a definition, otherwise import as a declaration.
-  bool doImportAsDefinition(const GlobalValue *SGV);
-
-  /// Get the name for SGV that should be used in the linked destination
-  /// module. Specifically, this handles the case where we need to rename
-  /// a local that is being promoted to global scope.
-  std::string getName(const GlobalValue *SGV);
-
-  /// Get the new linkage for SGV that should be used in the linked destination
-  /// module. Specifically, for ThinLTO importing or exporting it may need
-  /// to be adjusted.
-  GlobalValue::LinkageTypes getLinkage(const GlobalValue *SGV);
-
-  /// Copies the necessary global value attributes and name from the source
-  /// to the newly cloned global value.
-  void copyGVAttributes(GlobalValue *NewGV, const GlobalValue *SrcGV);
-
-  /// Updates the visibility for the new global cloned from the source
-  /// and, if applicable, linked with an existing destination global.
-  /// Handles visibility change required for promoted locals.
-  void setVisibility(GlobalValue *NewGV, const GlobalValue *SGV,
-                     const GlobalValue *DGV = nullptr);
-
   void linkNamedMDNodes();
 
 public:
-  ModuleLinker(Module &DstM, Linker::IdentifiedStructTypeSet &Set, Module &SrcM,
-               DiagnosticHandlerFunction DiagnosticHandler, unsigned Flags,
-               const FunctionInfoIndex *Index = nullptr,
-               DenseSet<const GlobalValue *> *FunctionsToImport = nullptr)
-      : DstM(DstM), SrcM(SrcM), TypeMap(Set), ValMaterializer(this),
-        DiagnosticHandler(DiagnosticHandler), Flags(Flags), ImportIndex(Index),
-        ImportFunction(FunctionsToImport) {
-    assert((ImportIndex || !ImportFunction) &&
-           "Expect a FunctionInfoIndex when importing");
-    // If we have a FunctionInfoIndex but no function to import,
-    // then this is the primary module being compiled in a ThinLTO
-    // backend compilation, and we need to see if it has functions that
-    // may be exported to another backend compilation.
-    if (ImportIndex && !ImportFunction)
-      HasExportedFunctions = ImportIndex->hasExportedFunctions(SrcM);
+  IRLinker(Module &DstM, IRMover::IdentifiedStructTypeSet &Set, Module &SrcM,
+           DiagnosticHandlerFunction DiagnosticHandler,
+           ArrayRef<GlobalValue *> ValuesToLink,
+           std::function<void(GlobalValue &, IRMover::ValueAdder)> AddLazyFor)
+      : DstM(DstM), SrcM(SrcM), AddLazyFor(AddLazyFor), TypeMap(Set),
+        GValMaterializer(this), LValMaterializer(this),
+        DiagnosticHandler(DiagnosticHandler) {
+    for (GlobalValue *GV : ValuesToLink)
+      maybeAdd(GV);
   }
 
   bool run();
-  Value *materializeDeclFor(Value *V);
-  void materializeInitFor(GlobalValue *New, GlobalValue *Old);
+  Value *materializeDeclFor(Value *V, bool ForAlias);
+  void materializeInitFor(GlobalValue *New, GlobalValue *Old, bool ForAlias);
 };
 }
 
@@ -564,9 +480,6 @@ public:
 static void forceRenaming(GlobalValue *GV, StringRef Name) {
   // If the global doesn't force its name or if it already has the right name,
   // there is nothing for us to do.
-  // Note that any required local to global promotion should already be done,
-  // so promoted locals will not skip this handling as their linkage is no
-  // longer local.
   if (GV->hasLocalLinkage() || GV->getName() == Name)
     return;
 
@@ -582,239 +495,88 @@ static void forceRenaming(GlobalValue *G
   }
 }
 
-/// copy additional attributes (those not needed to construct a GlobalValue)
-/// from the SrcGV to the DestGV.
-void ModuleLinker::copyGVAttributes(GlobalValue *NewGV,
-                                    const GlobalValue *SrcGV) {
-  NewGV->copyAttributesFrom(SrcGV);
-  forceRenaming(NewGV, getName(SrcGV));
+Value *GlobalValueMaterializer::materializeDeclFor(Value *V) {
+  return ModLinker->materializeDeclFor(V, false);
 }
 
-bool ModuleLinker::doImportAsDefinition(const GlobalValue *SGV) {
-  if (!isPerformingImport())
-    return false;
-  auto *GA = dyn_cast<GlobalAlias>(SGV);
-  if (GA) {
-    if (GA->hasWeakAnyLinkage())
-      return false;
-    const GlobalObject *GO = GA->getBaseObject();
-    if (!GO->hasLinkOnceODRLinkage())
-      return false;
-    return doImportAsDefinition(GO);
-  }
-  // Always import GlobalVariable definitions, except for the special
-  // case of WeakAny which are imported as ExternalWeak declarations
-  // (see comments in ModuleLinker::getLinkage). The linkage changes
-  // described in ModuleLinker::getLinkage ensure the correct behavior (e.g.
-  // global variables with external linkage are transformed to
-  // available_externally definitions, which are ultimately turned into
-  // declarations after the EliminateAvailableExternally pass).
-  if (isa<GlobalVariable>(SGV) && !SGV->isDeclaration() &&
-      !SGV->hasWeakAnyLinkage())
-    return true;
-  // Only import the function requested for importing.
-  auto *SF = dyn_cast<Function>(SGV);
-  if (SF && ImportFunction->count(SF))
-    return true;
-  // Otherwise no.
-  return false;
+void GlobalValueMaterializer::materializeInitFor(GlobalValue *New,
+                                                 GlobalValue *Old) {
+  ModLinker->materializeInitFor(New, Old, false);
 }
 
-bool ModuleLinker::doPromoteLocalToGlobal(const GlobalValue *SGV) {
-  assert(SGV->hasLocalLinkage());
-  // Both the imported references and the original local variable must
-  // be promoted.
-  if (!isPerformingImport() && !isModuleExporting())
-    return false;
-
-  // Local const variables never need to be promoted unless they are address
-  // taken. The imported uses can simply use the clone created in this module.
-  // For now we are conservative in determining which variables are not
-  // address taken by checking the unnamed addr flag. To be more aggressive,
-  // the address taken information must be checked earlier during parsing
-  // of the module and recorded in the function index for use when importing
-  // from that module.
-  auto *GVar = dyn_cast<GlobalVariable>(SGV);
-  if (GVar && GVar->isConstant() && GVar->hasUnnamedAddr())
-    return false;
+Value *LocalValueMaterializer::materializeDeclFor(Value *V) {
+  return ModLinker->materializeDeclFor(V, true);
+}
 
-  // Eventually we only need to promote functions in the exporting module that
-  // are referenced by a potentially exported function (i.e. one that is in the
-  // function index).
-  return true;
+void LocalValueMaterializer::materializeInitFor(GlobalValue *New,
+                                                GlobalValue *Old) {
+  ModLinker->materializeInitFor(New, Old, true);
 }
 
-std::string ModuleLinker::getName(const GlobalValue *SGV) {
-  // For locals that must be promoted to global scope, ensure that
-  // the promoted name uniquely identifies the copy in the original module,
-  // using the ID assigned during combined index creation. When importing,
-  // we rename all locals (not just those that are promoted) in order to
-  // avoid naming conflicts between locals imported from different modules.
-  if (SGV->hasLocalLinkage() &&
-      (doPromoteLocalToGlobal(SGV) || isPerformingImport()))
-    return FunctionInfoIndex::getGlobalNameForLocal(
-        SGV->getName(),
-        ImportIndex->getModuleId(SGV->getParent()->getModuleIdentifier()));
-  return SGV->getName();
-}
-
-GlobalValue::LinkageTypes ModuleLinker::getLinkage(const GlobalValue *SGV) {
-  // Any local variable that is referenced by an exported function needs
-  // to be promoted to global scope. Since we don't currently know which
-  // functions reference which local variables/functions, we must treat
-  // all as potentially exported if this module is exporting anything.
-  if (isModuleExporting()) {
-    if (SGV->hasLocalLinkage() && doPromoteLocalToGlobal(SGV))
-      return GlobalValue::ExternalLinkage;
-    return SGV->getLinkage();
-  }
-
-  // Otherwise, if we aren't importing, no linkage change is needed.
-  if (!isPerformingImport())
-    return SGV->getLinkage();
-
-  switch (SGV->getLinkage()) {
-  case GlobalValue::ExternalLinkage:
-    // External defnitions are converted to available_externally
-    // definitions upon import, so that they are available for inlining
-    // and/or optimization, but are turned into declarations later
-    // during the EliminateAvailableExternally pass.
-    if (doImportAsDefinition(SGV) && !dyn_cast<GlobalAlias>(SGV))
-      return GlobalValue::AvailableExternallyLinkage;
-    // An imported external declaration stays external.
-    return SGV->getLinkage();
-
-  case GlobalValue::AvailableExternallyLinkage:
-    // An imported available_externally definition converts
-    // to external if imported as a declaration.
-    if (!doImportAsDefinition(SGV))
-      return GlobalValue::ExternalLinkage;
-    // An imported available_externally declaration stays that way.
-    return SGV->getLinkage();
-
-  case GlobalValue::LinkOnceAnyLinkage:
-  case GlobalValue::LinkOnceODRLinkage:
-    // These both stay the same when importing the definition.
-    // The ThinLTO pass will eventually force-import their definitions.
-    return SGV->getLinkage();
-
-  case GlobalValue::WeakAnyLinkage:
-    // Can't import weak_any definitions correctly, or we might change the
-    // program semantics, since the linker will pick the first weak_any
-    // definition and importing would change the order they are seen by the
-    // linker. The module linking caller needs to enforce this.
-    assert(!doImportAsDefinition(SGV));
-    // If imported as a declaration, it becomes external_weak.
-    return GlobalValue::ExternalWeakLinkage;
-
-  case GlobalValue::WeakODRLinkage:
-    // For weak_odr linkage, there is a guarantee that all copies will be
-    // equivalent, so the issue described above for weak_any does not exist,
-    // and the definition can be imported. It can be treated similarly
-    // to an imported externally visible global value.
-    if (doImportAsDefinition(SGV) && !dyn_cast<GlobalAlias>(SGV))
-      return GlobalValue::AvailableExternallyLinkage;
-    else
-      return GlobalValue::ExternalLinkage;
+Value *IRLinker::materializeDeclFor(Value *V, bool ForAlias) {
+  auto *SGV = dyn_cast<GlobalValue>(V);
+  if (!SGV)
+    return nullptr;
 
-  case GlobalValue::AppendingLinkage:
-    // It would be incorrect to import an appending linkage variable,
-    // since it would cause global constructors/destructors to be
-    // executed multiple times. This should have already been handled
-    // by linkIfNeeded, and we will assert in shouldLinkFromSource
-    // if we try to import, so we simply return AppendingLinkage here
-    // as this helper is called more widely in getLinkedToGlobal.
-    return GlobalValue::AppendingLinkage;
-
-  case GlobalValue::InternalLinkage:
-  case GlobalValue::PrivateLinkage:
-    // If we are promoting the local to global scope, it is handled
-    // similarly to a normal externally visible global.
-    if (doPromoteLocalToGlobal(SGV)) {
-      if (doImportAsDefinition(SGV) && !dyn_cast<GlobalAlias>(SGV))
-        return GlobalValue::AvailableExternallyLinkage;
-      else
-        return GlobalValue::ExternalLinkage;
-    }
-    // A non-promoted imported local definition stays local.
-    // The ThinLTO pass will eventually force-import their definitions.
-    return SGV->getLinkage();
-
-  case GlobalValue::ExternalWeakLinkage:
-    // External weak doesn't apply to definitions, must be a declaration.
-    assert(!doImportAsDefinition(SGV));
-    // Linkage stays external_weak.
-    return SGV->getLinkage();
-
-  case GlobalValue::CommonLinkage:
-    // Linkage stays common on definitions.
-    // The ThinLTO pass will eventually force-import their definitions.
-    return SGV->getLinkage();
+  return linkGlobalValueProto(SGV, ForAlias);
+}
+
+void IRLinker::materializeInitFor(GlobalValue *New, GlobalValue *Old,
+                                  bool ForAlias) {
+  // If we already created the body, just return.
+  if (auto *F = dyn_cast<Function>(New)) {
+    if (!F->isDeclaration())
+      return;
+  } else if (auto *V = dyn_cast<GlobalVariable>(New)) {
+    if (V->hasInitializer())
+      return;
+  } else {
+    auto *A = cast<GlobalAlias>(New);
+    if (A->getAliasee())
+      return;
   }
 
-  llvm_unreachable("unknown linkage type");
+  if (ForAlias || shouldLink(New, *Old))
+    linkGlobalValueBody(*New, *Old);
 }
 
 /// Loop through the global variables in the src module and merge them into the
 /// dest module.
-GlobalVariable *
-ModuleLinker::copyGlobalVariableProto(const GlobalVariable *SGVar) {
+GlobalVariable *IRLinker::copyGlobalVariableProto(const GlobalVariable *SGVar) {
   // No linking to be performed or linking from the source: simply create an
   // identical version of the symbol over in the dest module... the
   // initializer will be filled in later by LinkGlobalInits.
   GlobalVariable *NewDGV =
       new GlobalVariable(DstM, TypeMap.get(SGVar->getType()->getElementType()),
                          SGVar->isConstant(), GlobalValue::ExternalLinkage,
-                         /*init*/ nullptr, getName(SGVar),
+                         /*init*/ nullptr, SGVar->getName(),
                          /*insertbefore*/ nullptr, SGVar->getThreadLocalMode(),
                          SGVar->getType()->getAddressSpace());
-
+  NewDGV->setAlignment(SGVar->getAlignment());
   return NewDGV;
 }
 
 /// Link the function in the source module into the destination module if
 /// needed, setting up mapping information.
-Function *ModuleLinker::copyFunctionProto(const Function *SF) {
+Function *IRLinker::copyFunctionProto(const Function *SF) {
   // If there is no linkage to be performed or we are linking from the source,
   // bring SF over.
   return Function::Create(TypeMap.get(SF->getFunctionType()),
-                          GlobalValue::ExternalLinkage, getName(SF), &DstM);
+                          GlobalValue::ExternalLinkage, SF->getName(), &DstM);
 }
 
 /// Set up prototypes for any aliases that come over from the source module.
-GlobalValue *ModuleLinker::copyGlobalAliasProto(const GlobalAlias *SGA) {
+GlobalValue *IRLinker::copyGlobalAliasProto(const GlobalAlias *SGA) {
   // If there is no linkage to be performed or we're linking from the source,
   // bring over SGA.
   auto *Ty = TypeMap.get(SGA->getValueType());
   return GlobalAlias::create(Ty, SGA->getType()->getPointerAddressSpace(),
-                             GlobalValue::ExternalLinkage, getName(SGA), &DstM);
-}
-
-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;
-}
-
-void ModuleLinker::setVisibility(GlobalValue *NewGV, const GlobalValue *SGV,
-                                 const GlobalValue *DGV) {
-  GlobalValue::VisibilityTypes Visibility = SGV->getVisibility();
-  if (DGV)
-    Visibility = getMinVisibility(DGV->getVisibility(), Visibility);
-  // For promoted locals, mark them hidden so that they can later be
-  // stripped from the symbol table to reduce bloat.
-  if (SGV->hasLocalLinkage() && doPromoteLocalToGlobal(SGV))
-    Visibility = GlobalValue::HiddenVisibility;
-  NewGV->setVisibility(Visibility);
+                             GlobalValue::ExternalLinkage, SGA->getName(),
+                             &DstM);
 }
 
-GlobalValue *ModuleLinker::copyGlobalValueProto(const GlobalValue *SGV,
-                                                bool ForDefinition) {
+GlobalValue *IRLinker::copyGlobalValueProto(const GlobalValue *SGV,
+                                            bool ForDefinition) {
   GlobalValue *NewGV;
   if (auto *SGVar = dyn_cast<GlobalVariable>(SGV)) {
     NewGV = copyGlobalVariableProto(SGVar);
@@ -827,294 +589,26 @@ GlobalValue *ModuleLinker::copyGlobalVal
       NewGV = new GlobalVariable(
           DstM, TypeMap.get(SGV->getType()->getElementType()),
           /*isConstant*/ false, GlobalValue::ExternalLinkage,
-          /*init*/ nullptr, getName(SGV),
+          /*init*/ nullptr, SGV->getName(),
           /*insertbefore*/ nullptr, SGV->getThreadLocalMode(),
           SGV->getType()->getAddressSpace());
   }
 
   if (ForDefinition)
-    NewGV->setLinkage(getLinkage(SGV));
-  else if (SGV->hasAvailableExternallyLinkage() || SGV->hasWeakLinkage() ||
+    NewGV->setLinkage(SGV->getLinkage());
+  else if (SGV->hasExternalWeakLinkage() || SGV->hasWeakLinkage() ||
            SGV->hasLinkOnceLinkage())
     NewGV->setLinkage(GlobalValue::ExternalWeakLinkage);
 
-  copyGVAttributes(NewGV, SGV);
+  NewGV->copyAttributesFrom(SGV);
   return NewGV;
 }
 
-Value *ValueMaterializerTy::materializeDeclFor(Value *V) {
-  return ModLinker->materializeDeclFor(V);
-}
-
-Value *ModuleLinker::materializeDeclFor(Value *V) {
-  auto *SGV = dyn_cast<GlobalValue>(V);
-  if (!SGV)
-    return nullptr;
-
-  return linkGlobalValueProto(SGV);
-}
-
-void ValueMaterializerTy::materializeInitFor(GlobalValue *New,
-                                             GlobalValue *Old) {
-  return ModLinker->materializeInitFor(New, Old);
-}
-
-static bool shouldLazyLink(const GlobalValue &GV) {
-  return GV.hasLocalLinkage() || GV.hasLinkOnceLinkage() ||
-         GV.hasAvailableExternallyLinkage();
-}
-
-void ModuleLinker::materializeInitFor(GlobalValue *New, GlobalValue *Old) {
-  if (auto *F = dyn_cast<Function>(New)) {
-    if (!F->isDeclaration())
-      return;
-  } else if (auto *V = dyn_cast<GlobalVariable>(New)) {
-    if (V->hasInitializer())
-      return;
-  } else {
-    auto *A = cast<GlobalAlias>(New);
-    if (A->getAliasee())
-      return;
-  }
-
-  if (Old->isDeclaration())
-    return;
-
-  if (isPerformingImport() && !doImportAsDefinition(Old))
-    return;
-
-  if (!ValuesToLink.count(Old) && !shouldLazyLink(*Old))
-    return;
-
-  linkGlobalValueBody(*New, *Old);
-}
-
-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->getBaseObject();
-    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,
-                                                 bool &LinkFromSrc) {
-  // 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.
-    LinkFromSrc = false;
-    break;
-  case Comdat::SelectionKind::NoDuplicates:
-    return emitError("Linking COMDATs named '" + ComdatName +
-                     "': noduplicates has been violated!");
-  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->getType()->getPointerElementType());
-    uint64_t SrcSize =
-        SrcDL.getTypeAllocSize(SrcGV->getType()->getPointerElementType());
-    if (Result == Comdat::SelectionKind::ExactMatch) {
-      if (SrcGV->getInitializer() != DstGV->getInitializer())
-        return emitError("Linking COMDATs named '" + ComdatName +
-                         "': ExactMatch violated!");
-      LinkFromSrc = false;
-    } else if (Result == Comdat::SelectionKind::Largest) {
-      LinkFromSrc = SrcSize > DstSize;
-    } else if (Result == Comdat::SelectionKind::SameSize) {
-      if (SrcSize != DstSize)
-        return emitError("Linking COMDATs named '" + ComdatName +
-                         "': SameSize violated!");
-      LinkFromSrc = false;
-    } else {
-      llvm_unreachable("unknown selection kind");
-    }
-    break;
-  }
-  }
-
-  return false;
-}
-
-bool ModuleLinker::getComdatResult(const Comdat *SrcC,
-                                   Comdat::SelectionKind &Result,
-                                   bool &LinkFromSrc) {
-  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.
-    LinkFromSrc = true;
-    Result = SSK;
-    return false;
-  }
-
-  const Comdat *DstC = &DstCI->second;
-  Comdat::SelectionKind DSK = DstC->getSelectionKind();
-  return computeResultingSelectionKind(ComdatName, SSK, DSK, Result,
-                                       LinkFromSrc);
-}
-
-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()) {
-    // Should have prevented importing for appending linkage in linkIfNeeded.
-    assert(!isPerformingImport());
-    LinkFromSrc = true;
-    return false;
-  }
-
-  bool SrcIsDeclaration = Src.isDeclarationForLinker();
-  bool DestIsDeclaration = Dest.isDeclarationForLinker();
-
-  if (isPerformingImport()) {
-    if (isa<Function>(&Src)) {
-      // For functions, LinkFromSrc iff this is the function requested
-      // for importing. For variables, decide below normally.
-      LinkFromSrc = ImportFunction->count(&Src);
-      return false;
-    }
-
-    // Check if this is an alias with an already existing definition
-    // in Dest, which must have come from a prior importing pass from
-    // the same Src module. Unlike imported function and variable
-    // definitions, which are imported as available_externally and are
-    // not definitions for the linker, that is not a valid linkage for
-    // imported aliases which must be definitions. Simply use the existing
-    // Dest copy.
-    if (isa<GlobalAlias>(&Src) && !DestIsDeclaration) {
-      assert(isa<GlobalAlias>(&Dest));
-      LinkFromSrc = false;
-      return false;
-    }
-  }
-
-  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.getType()->getElementType());
-    uint64_t SrcSize = DL.getTypeAllocSize(Src.getType()->getElementType());
-    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!");
-}
-
 /// Loop over all of the linked values to compute type mappings.  For example,
 /// if we link "extern Foo *x" and "Foo *x = NULL", then we have two struct
 /// types 'Foo' but one got renamed when the module was loaded into the same
 /// LLVMContext.
-void ModuleLinker::computeTypeMapping() {
+void IRLinker::computeTypeMapping() {
   for (GlobalValue &SGV : SrcM.globals()) {
     GlobalValue *DGV = getLinkedToGlobal(&SGV);
     if (!DGV)
@@ -1131,15 +625,13 @@ void ModuleLinker::computeTypeMapping()
     TypeMap.addTypeMapping(DAT->getElementType(), SAT->getElementType());
   }
 
-  for (GlobalValue &SGV : SrcM) {
+  for (GlobalValue &SGV : SrcM)
     if (GlobalValue *DGV = getLinkedToGlobal(&SGV))
       TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
-  }
 
-  for (GlobalValue &SGV : SrcM.aliases()) {
+  for (GlobalValue &SGV : SrcM.aliases())
     if (GlobalValue *DGV = getLinkedToGlobal(&SGV))
       TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
-  }
 
   // Incorporate types by name, scanning all the types in the source module.
   // At this point, the destination module may have a type "%foo = { i32 }" for
@@ -1198,8 +690,8 @@ static void getArrayElements(const Const
 
 /// If there were any appending global variables, link them together now.
 /// Return true on error.
-Constant *ModuleLinker::linkAppendingVarProto(GlobalVariable *DstGV,
-                                              const GlobalVariable *SrcGV) {
+Constant *IRLinker::linkAppendingVarProto(GlobalVariable *DstGV,
+                                          const GlobalVariable *SrcGV) {
   Type *EltTy = cast<ArrayType>(TypeMap.get(SrcGV->getType()->getElementType()))
                     ->getElementType();
 
@@ -1278,8 +770,10 @@ Constant *ModuleLinker::linkAppendingVar
                        [this](Constant *E) {
                          auto *Key = dyn_cast<GlobalValue>(
                              E->getAggregateElement(2)->stripPointerCasts());
-                         return Key && !ValuesToLink.count(Key) &&
-                                !shouldLazyLink(*Key);
+                         if (!Key)
+                           return false;
+                         GlobalValue *DGV = getLinkedToGlobal(Key);
+                         return !shouldLink(DGV, *Key);
                        }),
         SrcElements.end());
   uint64_t NewSize = DstElements.size() + SrcElements.size();
@@ -1291,8 +785,8 @@ Constant *ModuleLinker::linkAppendingVar
       /*init*/ nullptr, /*name*/ "", DstGV, SrcGV->getThreadLocalMode(),
       SrcGV->getType()->getAddressSpace());
 
-  // Propagate alignment, visibility and section info.
-  copyGVAttributes(NG, SrcGV);
+  NG->copyAttributesFrom(SrcGV);
+  forceRenaming(NG, SrcGV->getName());
 
   Constant *Ret = ConstantExpr::getBitCast(NG, TypeMap.get(SrcGV->getType()));
 
@@ -1304,15 +798,15 @@ Constant *ModuleLinker::linkAppendingVar
     if (IsOldStructor) {
       auto *S = cast<ConstantStruct>(V);
       auto *E1 = MapValue(S->getOperand(0), ValueMap, RF_MoveDistinctMDs,
-                          &TypeMap, &ValMaterializer);
+                          &TypeMap, &GValMaterializer);
       auto *E2 = MapValue(S->getOperand(1), ValueMap, RF_MoveDistinctMDs,
-                          &TypeMap, &ValMaterializer);
+                          &TypeMap, &GValMaterializer);
       Value *Null = Constant::getNullValue(VoidPtrTy);
       NewV =
           ConstantStruct::get(cast<StructType>(EltTy), E1, E2, Null, nullptr);
     } else {
-      NewV =
-          MapValue(V, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
+      NewV = MapValue(V, ValueMap, RF_MoveDistinctMDs, &TypeMap,
+                      &GValMaterializer);
     }
     DstElements.push_back(NewV);
   }
@@ -1329,41 +823,71 @@ Constant *ModuleLinker::linkAppendingVar
   return Ret;
 }
 
-Constant *ModuleLinker::linkGlobalValueProto(GlobalValue *SGV) {
+static bool useExistingDest(GlobalValue &SGV, GlobalValue *DGV,
+                            bool ShouldLink) {
+  if (!DGV)
+    return false;
+
+  if (SGV.isDeclaration())
+    return true;
+
+  if (DGV->isDeclarationForLinker())
+    return false;
+
+  if (ShouldLink)
+    return false;
+
+  return true;
+}
+
+bool IRLinker::shouldLink(GlobalValue *DGV, GlobalValue &SGV) {
+  if (ValuesToLink.count(&SGV))
+    return true;
+
+  if (SGV.hasLocalLinkage())
+    return true;
+
+  if (DGV && !DGV->isDeclaration())
+    return false;
+
+  if (SGV.hasAvailableExternallyLinkage())
+    return true;
+
+  if (DoneLinkingBodies)
+    return false;
+
+  AddLazyFor(SGV, [this](GlobalValue &GV) { maybeAdd(&GV); });
+  return ValuesToLink.count(&SGV);
+}
+
+Constant *IRLinker::linkGlobalValueProto(GlobalValue *SGV, bool ForAlias) {
   GlobalValue *DGV = getLinkedToGlobal(SGV);
 
+  bool ShouldLink = shouldLink(DGV, *SGV);
+
+  // just missing from map
+  if (ShouldLink) {
+    auto I = ValueMap.find(SGV);
+    if (I != ValueMap.end())
+      return cast<Constant>(I->second);
+
+    I = AliasValueMap.find(SGV);
+    if (I != AliasValueMap.end())
+      return cast<Constant>(I->second);
+  }
+
+  DGV = nullptr;
+  if (ShouldLink || !ForAlias)
+    DGV = getLinkedToGlobal(SGV);
+
   // Handle the ultra special appending linkage case first.
   assert(!DGV || SGV->hasAppendingLinkage() == DGV->hasAppendingLinkage());
-  if (SGV->hasAppendingLinkage()) {
-    // Should have prevented importing for appending linkage in linkIfNeeded.
-    assert(!isPerformingImport());
+  if (SGV->hasAppendingLinkage())
     return linkAppendingVarProto(cast_or_null<GlobalVariable>(DGV),
                                  cast<GlobalVariable>(SGV));
-  }
-
-  bool LinkFromSrc = true;
-  Comdat *C = nullptr;
-  bool HasUnnamedAddr = SGV->hasUnnamedAddr();
-
-  if (isPerformingImport() && !doImportAsDefinition(SGV)) {
-    LinkFromSrc = false;
-  } else if (const Comdat *SC = SGV->getComdat()) {
-    Comdat::SelectionKind SK;
-    std::tie(SK, LinkFromSrc) = ComdatsChosen[SC];
-    C = DstM.getOrInsertComdat(SC->getName());
-    C->setSelectionKind(SK);
-    if (SGV->hasLocalLinkage())
-      LinkFromSrc = true;
-  } else if (DGV) {
-    if (shouldLinkFromSource(LinkFromSrc, *DGV, *SGV))
-      return nullptr;
-  }
-
-  if (DGV)
-    HasUnnamedAddr = HasUnnamedAddr && DGV->hasUnnamedAddr();
 
   GlobalValue *NewGV;
-  if (!LinkFromSrc && DGV) {
+  if (useExistingDest(*SGV, DGV, ShouldLink)) {
     NewGV = DGV;
   } else {
     // If we are done linking global value bodies (i.e. we are performing
@@ -1372,48 +896,47 @@ Constant *ModuleLinker::linkGlobalValueP
     if (DoneLinkingBodies)
       return nullptr;
 
-    NewGV = copyGlobalValueProto(SGV, LinkFromSrc);
+    NewGV = copyGlobalValueProto(SGV, ShouldLink);
+    if (!ForAlias)
+      forceRenaming(NewGV, SGV->getName());
+  }
+  if (ShouldLink || ForAlias) {
+    if (const Comdat *SC = SGV->getComdat()) {
+      if (auto *GO = dyn_cast<GlobalObject>(NewGV)) {
+        Comdat *DC = DstM.getOrInsertComdat(SC->getName());
+        DC->setSelectionKind(SC->getSelectionKind());
+        GO->setComdat(DC);
+      }
+    }
   }
 
-  setVisibility(NewGV, SGV, DGV);
-  NewGV->setUnnamedAddr(HasUnnamedAddr);
-
-  if (auto *NewGO = dyn_cast<GlobalObject>(NewGV)) {
-    if (C && LinkFromSrc)
-      NewGO->setComdat(C);
-
-    if (DGV && DGV->hasCommonLinkage() && SGV->hasCommonLinkage())
-      NewGO->setAlignment(std::max(DGV->getAlignment(), SGV->getAlignment()));
-  }
+  if (!ShouldLink && ForAlias)
+    NewGV->setLinkage(GlobalValue::InternalLinkage);
 
-  if (auto *NewGVar = dyn_cast<GlobalVariable>(NewGV)) {
-    auto *DGVar = dyn_cast_or_null<GlobalVariable>(DGV);
-    auto *SGVar = dyn_cast<GlobalVariable>(SGV);
-    if (DGVar && SGVar && DGVar->isDeclaration() && SGVar->isDeclaration() &&
-        (!DGVar->isConstant() || !SGVar->isConstant()))
-      NewGVar->setConstant(false);
-  }
+  Constant *C = NewGV;
+  if (DGV)
+    C = ConstantExpr::getBitCast(NewGV, TypeMap.get(SGV->getType()));
 
-  if (NewGV != DGV && DGV) {
+  if (DGV && NewGV != DGV) {
     DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, DGV->getType()));
     DGV->eraseFromParent();
   }
 
-  return ConstantExpr::getBitCast(NewGV, TypeMap.get(SGV->getType()));
+  return C;
 }
 
 /// Update the initializers in the Dest module now that all globals that may be
 /// referenced are in Dest.
-void ModuleLinker::linkGlobalInit(GlobalVariable &Dst, GlobalVariable &Src) {
+void IRLinker::linkGlobalInit(GlobalVariable &Dst, GlobalVariable &Src) {
   // Figure out what the initializer looks like in the dest module.
   Dst.setInitializer(MapValue(Src.getInitializer(), ValueMap,
-                              RF_MoveDistinctMDs, &TypeMap, &ValMaterializer));
+                              RF_MoveDistinctMDs, &TypeMap, &GValMaterializer));
 }
 
 /// Copy the source function over into the dest function and fix up references
 /// to values. At this point we know that Dest is an external function, and
 /// that Src is not.
-bool ModuleLinker::linkFunctionBody(Function &Dst, Function &Src) {
+bool IRLinker::linkFunctionBody(Function &Dst, Function &Src) {
   assert(Dst.isDeclaration() && !Src.isDeclaration());
 
   // Materialize if needed.
@@ -1423,19 +946,20 @@ bool ModuleLinker::linkFunctionBody(Func
   // Link in the prefix data.
   if (Src.hasPrefixData())
     Dst.setPrefixData(MapValue(Src.getPrefixData(), ValueMap,
-                               RF_MoveDistinctMDs, &TypeMap, &ValMaterializer));
+                               RF_MoveDistinctMDs, &TypeMap,
+                               &GValMaterializer));
 
   // Link in the prologue data.
   if (Src.hasPrologueData())
     Dst.setPrologueData(MapValue(Src.getPrologueData(), ValueMap,
                                  RF_MoveDistinctMDs, &TypeMap,
-                                 &ValMaterializer));
+                                 &GValMaterializer));
 
   // Link in the personality function.
   if (Src.hasPersonalityFn())
     Dst.setPersonalityFn(MapValue(Src.getPersonalityFn(), ValueMap,
                                   RF_MoveDistinctMDs, &TypeMap,
-                                  &ValMaterializer));
+                                  &GValMaterializer));
 
   // Go through and convert function arguments over, remembering the mapping.
   Function::arg_iterator DI = Dst.arg_begin();
@@ -1452,7 +976,7 @@ bool ModuleLinker::linkFunctionBody(Func
   Src.getAllMetadata(MDs);
   for (const auto &I : MDs)
     Dst.setMetadata(I.first, MapMetadata(I.second, ValueMap, RF_MoveDistinctMDs,
-                                         &TypeMap, &ValMaterializer));
+                                         &TypeMap, &GValMaterializer));
 
   // Splice the body of the source function into the dest function.
   Dst.getBasicBlockList().splice(Dst.end(), Src.getBasicBlockList());
@@ -1465,7 +989,7 @@ bool ModuleLinker::linkFunctionBody(Func
     for (Instruction &I : BB)
       RemapInstruction(&I, ValueMap,
                        RF_IgnoreMissingEntries | RF_MoveDistinctMDs, &TypeMap,
-                       &ValMaterializer);
+                       &GValMaterializer);
 
   // There is no need to map the arguments anymore.
   for (Argument &Arg : Src.args())
@@ -1475,30 +999,14 @@ bool ModuleLinker::linkFunctionBody(Func
   return false;
 }
 
-void ModuleLinker::linkAliasBody(GlobalAlias &Dst, GlobalAlias &Src) {
+void IRLinker::linkAliasBody(GlobalAlias &Dst, GlobalAlias &Src) {
   Constant *Aliasee = Src.getAliasee();
-  Constant *Val = MapValue(Aliasee, ValueMap, RF_MoveDistinctMDs, &TypeMap,
-                           &ValMaterializer);
+  Constant *Val = MapValue(Aliasee, AliasValueMap, RF_MoveDistinctMDs, &TypeMap,
+                           &LValMaterializer);
   Dst.setAliasee(Val);
 }
 
-bool ModuleLinker::linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src) {
-  if (const Comdat *SC = Src.getComdat()) {
-    // To ensure that we don't generate an incomplete comdat group,
-    // we must materialize and map in any other members that are not
-    // yet materialized in Dst, which also ensures their definitions
-    // are linked in. Otherwise, linkonce and other lazy linked GVs will
-    // not be materialized if they aren't referenced.
-    for (auto *SGV : ComdatMembers[SC]) {
-      auto *DGV = cast_or_null<GlobalValue>(ValueMap.lookup(SGV));
-      if (DGV && !DGV->isDeclaration())
-        continue;
-      MapValue(SGV, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
-    }
-  }
-  if (shouldInternalizeLinkedSymbols())
-    if (auto *DGV = dyn_cast<GlobalValue>(&Dst))
-      DGV->setLinkage(GlobalValue::InternalLinkage);
+bool IRLinker::linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src) {
   if (auto *F = dyn_cast<Function>(&Src))
     return linkFunctionBody(cast<Function>(Dst), *F);
   if (auto *GVar = dyn_cast<GlobalVariable>(&Src)) {
@@ -1510,7 +1018,7 @@ bool ModuleLinker::linkGlobalValueBody(G
 }
 
 /// Insert all of the named MDNodes in Src into the Dest module.
-void ModuleLinker::linkNamedMDNodes() {
+void IRLinker::linkNamedMDNodes() {
   const NamedMDNode *SrcModFlags = SrcM.getModuleFlagsMetadata();
   for (const NamedMDNode &NMD : SrcM.named_metadata()) {
     // Don't link module flags here. Do them separately.
@@ -1521,12 +1029,12 @@ void ModuleLinker::linkNamedMDNodes() {
     for (const MDNode *op : NMD.operands())
       DestNMD->addOperand(MapMetadata(
           op, ValueMap, RF_MoveDistinctMDs | RF_NullMapMissingGlobalValues,
-          &TypeMap, &ValMaterializer));
+          &TypeMap, &GValMaterializer));
   }
 }
 
 /// Merge the linker flags in Src into the Dest module.
-bool ModuleLinker::linkModuleFlagsMetadata() {
+bool IRLinker::linkModuleFlagsMetadata() {
   // If the source module has no module flags, we are done.
   const NamedMDNode *SrcModFlags = SrcM.getModuleFlagsMetadata();
   if (!SrcModFlags)
@@ -1705,74 +1213,7 @@ static std::string mergeTriples(const Tr
   return DstTriple.str();
 }
 
-bool ModuleLinker::linkIfNeeded(GlobalValue &GV) {
-  GlobalValue *DGV = getLinkedToGlobal(&GV);
-
-  if (shouldLinkOnlyNeeded() && !(DGV && 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()) {
-        unsigned 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);
-
-    bool HasUnnamedAddr = GV.hasUnnamedAddr() && DGV->hasUnnamedAddr();
-    DGV->setUnnamedAddr(HasUnnamedAddr);
-    GV.setUnnamedAddr(HasUnnamedAddr);
-  }
-
-  // Don't want to append to global_ctors list, for example, when we
-  // are importing for ThinLTO, otherwise the global ctors and dtors
-  // get executed multiple times for local variables (the latter causing
-  // double frees).
-  if (GV.hasAppendingLinkage() && isPerformingImport())
-    return false;
-
-  if (isPerformingImport() && !doImportAsDefinition(&GV))
-    return false;
-
-  if (!DGV && !shouldOverrideFromSrc() &&
-      (GV.hasLocalLinkage() || GV.hasLinkOnceLinkage() ||
-       GV.hasAvailableExternallyLinkage()))
-    return false;
-
-  if (GV.isDeclaration())
-    return false;
-
-  if (const Comdat *SC = GV.getComdat()) {
-    bool LinkFromSrc;
-    Comdat::SelectionKind SK;
-    std::tie(SK, LinkFromSrc) = ComdatsChosen[SC];
-    if (LinkFromSrc)
-      ValuesToLink.insert(&GV);
-    return false;
-  }
-
-  bool LinkFromSrc = true;
-  if (DGV && shouldLinkFromSource(LinkFromSrc, *DGV, GV))
-    return true;
-  if (LinkFromSrc)
-    ValuesToLink.insert(&GV);
-  return false;
-}
-
-bool ModuleLinker::run() {
+bool IRLinker::run() {
   // Inherit the target data from the source module if the destination module
   // doesn't have one already.
   if (DstM.getDataLayout().isDefault())
@@ -1812,46 +1253,18 @@ bool ModuleLinker::run() {
   // Loop over all of the linked values to compute type mappings.
   computeTypeMapping();
 
-  ComdatsChosen.clear();
-  for (const auto &SMEC : SrcM.getComdatSymbolTable()) {
-    const Comdat &C = SMEC.getValue();
-    if (ComdatsChosen.count(&C))
+  std::reverse(Worklist.begin(), Worklist.end());
+  while (!Worklist.empty()) {
+    GlobalValue *GV = Worklist.back();
+    Worklist.pop_back();
+
+    // Already mapped.
+    if (ValueMap.find(GV) != ValueMap.end() ||
+        AliasValueMap.find(GV) != AliasValueMap.end())
       continue;
-    Comdat::SelectionKind SK;
-    bool LinkFromSrc;
-    if (getComdatResult(&C, SK, LinkFromSrc))
-      return true;
-    ComdatsChosen[&C] = std::make_pair(SK, LinkFromSrc);
-  }
-
-  for (GlobalVariable &GV : SrcM.globals())
-    if (const Comdat *SC = GV.getComdat())
-      ComdatMembers[SC].push_back(&GV);
-
-  for (Function &SF : SrcM)
-    if (const Comdat *SC = SF.getComdat())
-      ComdatMembers[SC].push_back(&SF);
 
-  for (GlobalAlias &GA : SrcM.aliases())
-    if (const Comdat *SC = GA.getComdat())
-      ComdatMembers[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).
-  for (GlobalVariable &GV : SrcM.globals())
-    if (linkIfNeeded(GV))
-      return true;
-
-  for (Function &SF : SrcM)
-    if (linkIfNeeded(SF))
-      return true;
-
-  for (GlobalAlias &GA : SrcM.aliases())
-    if (linkIfNeeded(GA))
-      return true;
-
-  for (GlobalValue *GV : ValuesToLink) {
-    MapValue(GV, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
+    assert(!GV->isDeclaration());
+    MapValue(GV, ValueMap, RF_MoveDistinctMDs, &TypeMap, &GValMaterializer);
     if (HasError)
       return true;
   }
@@ -1872,13 +1285,13 @@ bool ModuleLinker::run() {
   return false;
 }
 
-Linker::StructTypeKeyInfo::KeyTy::KeyTy(ArrayRef<Type *> E, bool P)
+IRMover::StructTypeKeyInfo::KeyTy::KeyTy(ArrayRef<Type *> E, bool P)
     : ETypes(E), IsPacked(P) {}
 
-Linker::StructTypeKeyInfo::KeyTy::KeyTy(const StructType *ST)
+IRMover::StructTypeKeyInfo::KeyTy::KeyTy(const StructType *ST)
     : ETypes(ST->elements()), IsPacked(ST->isPacked()) {}
 
-bool Linker::StructTypeKeyInfo::KeyTy::operator==(const KeyTy &That) const {
+bool IRMover::StructTypeKeyInfo::KeyTy::operator==(const KeyTy &That) const {
   if (IsPacked != That.IsPacked)
     return false;
   if (ETypes != That.ETypes)
@@ -1886,36 +1299,36 @@ bool Linker::StructTypeKeyInfo::KeyTy::o
   return true;
 }
 
-bool Linker::StructTypeKeyInfo::KeyTy::operator!=(const KeyTy &That) const {
+bool IRMover::StructTypeKeyInfo::KeyTy::operator!=(const KeyTy &That) const {
   return !this->operator==(That);
 }
 
-StructType *Linker::StructTypeKeyInfo::getEmptyKey() {
+StructType *IRMover::StructTypeKeyInfo::getEmptyKey() {
   return DenseMapInfo<StructType *>::getEmptyKey();
 }
 
-StructType *Linker::StructTypeKeyInfo::getTombstoneKey() {
+StructType *IRMover::StructTypeKeyInfo::getTombstoneKey() {
   return DenseMapInfo<StructType *>::getTombstoneKey();
 }
 
-unsigned Linker::StructTypeKeyInfo::getHashValue(const KeyTy &Key) {
+unsigned IRMover::StructTypeKeyInfo::getHashValue(const KeyTy &Key) {
   return hash_combine(hash_combine_range(Key.ETypes.begin(), Key.ETypes.end()),
                       Key.IsPacked);
 }
 
-unsigned Linker::StructTypeKeyInfo::getHashValue(const StructType *ST) {
+unsigned IRMover::StructTypeKeyInfo::getHashValue(const StructType *ST) {
   return getHashValue(KeyTy(ST));
 }
 
-bool Linker::StructTypeKeyInfo::isEqual(const KeyTy &LHS,
-                                        const StructType *RHS) {
+bool IRMover::StructTypeKeyInfo::isEqual(const KeyTy &LHS,
+                                         const StructType *RHS) {
   if (RHS == getEmptyKey() || RHS == getTombstoneKey())
     return false;
   return LHS == KeyTy(RHS);
 }
 
-bool Linker::StructTypeKeyInfo::isEqual(const StructType *LHS,
-                                        const StructType *RHS) {
+bool IRMover::StructTypeKeyInfo::isEqual(const StructType *LHS,
+                                         const StructType *RHS) {
   if (RHS == getEmptyKey())
     return LHS == getEmptyKey();
 
@@ -1925,12 +1338,12 @@ bool Linker::StructTypeKeyInfo::isEqual(
   return KeyTy(LHS) == KeyTy(RHS);
 }
 
-void Linker::IdentifiedStructTypeSet::addNonOpaque(StructType *Ty) {
+void IRMover::IdentifiedStructTypeSet::addNonOpaque(StructType *Ty) {
   assert(!Ty->isOpaque());
   NonOpaqueStructTypes.insert(Ty);
 }
 
-void Linker::IdentifiedStructTypeSet::switchToNonOpaque(StructType *Ty) {
+void IRMover::IdentifiedStructTypeSet::switchToNonOpaque(StructType *Ty) {
   assert(!Ty->isOpaque());
   NonOpaqueStructTypes.insert(Ty);
   bool Removed = OpaqueStructTypes.erase(Ty);
@@ -1938,22 +1351,22 @@ void Linker::IdentifiedStructTypeSet::sw
   assert(Removed);
 }
 
-void Linker::IdentifiedStructTypeSet::addOpaque(StructType *Ty) {
+void IRMover::IdentifiedStructTypeSet::addOpaque(StructType *Ty) {
   assert(Ty->isOpaque());
   OpaqueStructTypes.insert(Ty);
 }
 
 StructType *
-Linker::IdentifiedStructTypeSet::findNonOpaque(ArrayRef<Type *> ETypes,
-                                               bool IsPacked) {
-  Linker::StructTypeKeyInfo::KeyTy Key(ETypes, IsPacked);
+IRMover::IdentifiedStructTypeSet::findNonOpaque(ArrayRef<Type *> ETypes,
+                                                bool IsPacked) {
+  IRMover::StructTypeKeyInfo::KeyTy Key(ETypes, IsPacked);
   auto I = NonOpaqueStructTypes.find_as(Key);
   if (I == NonOpaqueStructTypes.end())
     return nullptr;
   return *I;
 }
 
-bool Linker::IdentifiedStructTypeSet::hasType(StructType *Ty) {
+bool IRMover::IdentifiedStructTypeSet::hasType(StructType *Ty) {
   if (Ty->isOpaque())
     return OpaqueStructTypes.count(Ty);
   auto I = NonOpaqueStructTypes.find(Ty);
@@ -1962,7 +1375,7 @@ bool Linker::IdentifiedStructTypeSet::ha
   return *I == Ty;
 }
 
-Linker::Linker(Module &M, DiagnosticHandlerFunction DiagnosticHandler)
+IRMover::IRMover(Module &M, DiagnosticHandlerFunction DiagnosticHandler)
     : Composite(M), DiagnosticHandler(DiagnosticHandler) {
   TypeFinder StructTypes;
   StructTypes.run(M, true);
@@ -1974,61 +1387,12 @@ Linker::Linker(Module &M, DiagnosticHand
   }
 }
 
-bool Linker::linkInModule(Module &Src, unsigned Flags,
-                          const FunctionInfoIndex *Index,
-                          DenseSet<const GlobalValue *> *FunctionsToImport) {
-  ModuleLinker TheLinker(Composite, IdentifiedStructTypes, Src,
-                         DiagnosticHandler, Flags, Index, FunctionsToImport);
+bool IRMover::move(
+    Module &Src, ArrayRef<GlobalValue *> ValuesToLink,
+    std::function<void(GlobalValue &, ValueAdder Add)> AddLazyFor) {
+  IRLinker TheLinker(Composite, IdentifiedStructTypes, Src, DiagnosticHandler,
+                     ValuesToLink, AddLazyFor);
   bool RetCode = TheLinker.run();
   Composite.dropTriviallyDeadConstantArrays();
   return RetCode;
 }
-
-//===----------------------------------------------------------------------===//
-// 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, Module &Src,
-                         DiagnosticHandlerFunction DiagnosticHandler,
-                         unsigned Flags) {
-  Linker L(Dest, DiagnosticHandler);
-  return L.linkInModule(Src, Flags);
-}
-
-std::unique_ptr<Module>
-llvm::renameModuleForThinLTO(std::unique_ptr<Module> &M,
-                             const FunctionInfoIndex *Index,
-                             DiagnosticHandlerFunction DiagnosticHandler) {
-  std::unique_ptr<llvm::Module> RenamedModule(
-      new llvm::Module(M->getModuleIdentifier(), M->getContext()));
-  Linker L(*RenamedModule.get(), DiagnosticHandler);
-  if (L.linkInModule(*M.get(), llvm::Linker::Flags::None, Index))
-    return nullptr;
-  return RenamedModule;
-}
-
-//===----------------------------------------------------------------------===//
-// C API.
-//===----------------------------------------------------------------------===//
-
-LLVMBool LLVMLinkModules(LLVMModuleRef Dest, LLVMModuleRef Src,
-                         LLVMLinkerMode Unused, char **OutMessages) {
-  Module *D = unwrap(Dest);
-  std::string Message;
-  raw_string_ostream Stream(Message);
-  DiagnosticPrinterRawOStream DP(Stream);
-
-  LLVMBool Result = Linker::linkModules(
-      *D, *unwrap(Src), [&](const DiagnosticInfo &DI) { DI.print(DP); });
-
-  if (OutMessages && Result) {
-    Stream.flush();
-    *OutMessages = strdup(Message.c_str());
-  }
-  return Result;
-}

Added: llvm/trunk/lib/Linker/LinkDiagnosticInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/LinkDiagnosticInfo.h?rev=255254&view=auto
==============================================================================
--- llvm/trunk/lib/Linker/LinkDiagnosticInfo.h (added)
+++ llvm/trunk/lib/Linker/LinkDiagnosticInfo.h Thu Dec 10 08:19:35 2015
@@ -0,0 +1,25 @@
+//===- LinkDiagnosticInfo.h -------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_LINKER_LINK_DIAGNOSTIC_INFO_H
+#define LLVM_LIB_LINKER_LINK_DIAGNOSTIC_INFO_H
+
+#include "llvm/IR/DiagnosticInfo.h"
+
+namespace llvm {
+class LinkDiagnosticInfo : public DiagnosticInfo {
+  const Twine &Msg;
+
+public:
+  LinkDiagnosticInfo(DiagnosticSeverity Severity, const Twine &Msg);
+  void print(DiagnosticPrinter &DP) const override;
+};
+}
+
+#endif

Modified: llvm/trunk/lib/Linker/LinkModules.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/LinkModules.cpp?rev=255254&r1=255253&r2=255254&view=diff
==============================================================================
--- llvm/trunk/lib/Linker/LinkModules.cpp (original)
+++ llvm/trunk/lib/Linker/LinkModules.cpp Thu Dec 10 08:19:35 2015
@@ -12,389 +12,23 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Linker/Linker.h"
+#include "LinkDiagnosticInfo.h"
 #include "llvm-c/Linker.h"
 #include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallString.h"
-#include "llvm/ADT/Triple.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/IR/DiagnosticPrinter.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/TypeFinder.h"
-#include "llvm/Transforms/Utils/Cloning.h"
 using namespace llvm;
 
-//===----------------------------------------------------------------------===//
-// TypeMap implementation.
-//===----------------------------------------------------------------------===//
-
-namespace {
-class TypeMapTy : public ValueMapTypeRemapper {
-  /// This is a mapping from a source type to a destination type to use.
-  DenseMap<Type *, Type *> MappedTypes;
-
-  /// When checking to see if two subgraphs are isomorphic, we speculatively
-  /// add types to MappedTypes, but keep track of them here in case we need to
-  /// roll back.
-  SmallVector<Type *, 16> SpeculativeTypes;
-
-  SmallVector<StructType *, 16> SpeculativeDstOpaqueTypes;
-
-  /// This is a list of non-opaque structs in the source module that are mapped
-  /// to an opaque struct in the destination module.
-  SmallVector<StructType *, 16> SrcDefinitionsToResolve;
-
-  /// This is the set of opaque types in the destination modules who are
-  /// getting a body from the source module.
-  SmallPtrSet<StructType *, 16> DstResolvedOpaqueTypes;
-
-public:
-  TypeMapTy(Linker::IdentifiedStructTypeSet &DstStructTypesSet)
-      : DstStructTypesSet(DstStructTypesSet) {}
-
-  Linker::IdentifiedStructTypeSet &DstStructTypesSet;
-  /// Indicate that the specified type in the destination module is conceptually
-  /// equivalent to the specified type in the source module.
-  void addTypeMapping(Type *DstTy, Type *SrcTy);
-
-  /// Produce a body for an opaque type in the dest module from a type
-  /// definition in the source module.
-  void linkDefinedTypeBodies();
-
-  /// Return the mapped type to use for the specified input type from the
-  /// source module.
-  Type *get(Type *SrcTy);
-  Type *get(Type *SrcTy, SmallPtrSet<StructType *, 8> &Visited);
-
-  void finishType(StructType *DTy, StructType *STy, ArrayRef<Type *> ETypes);
-
-  FunctionType *get(FunctionType *T) {
-    return cast<FunctionType>(get((Type *)T));
-  }
-
-  /// Dump out the type map for debugging purposes.
-  void dump() const {
-    for (auto &Pair : MappedTypes) {
-      dbgs() << "TypeMap: ";
-      Pair.first->print(dbgs());
-      dbgs() << " => ";
-      Pair.second->print(dbgs());
-      dbgs() << '\n';
-    }
-  }
-
-private:
-  Type *remapType(Type *SrcTy) override { return get(SrcTy); }
-
-  bool areTypesIsomorphic(Type *DstTy, Type *SrcTy);
-};
-}
-
-void TypeMapTy::addTypeMapping(Type *DstTy, Type *SrcTy) {
-  assert(SpeculativeTypes.empty());
-  assert(SpeculativeDstOpaqueTypes.empty());
-
-  // Check to see if these types are recursively isomorphic and establish a
-  // mapping between them if so.
-  if (!areTypesIsomorphic(DstTy, SrcTy)) {
-    // Oops, they aren't isomorphic.  Just discard this request by rolling out
-    // any speculative mappings we've established.
-    for (Type *Ty : SpeculativeTypes)
-      MappedTypes.erase(Ty);
-
-    SrcDefinitionsToResolve.resize(SrcDefinitionsToResolve.size() -
-                                   SpeculativeDstOpaqueTypes.size());
-    for (StructType *Ty : SpeculativeDstOpaqueTypes)
-      DstResolvedOpaqueTypes.erase(Ty);
-  } else {
-    for (Type *Ty : SpeculativeTypes)
-      if (auto *STy = dyn_cast<StructType>(Ty))
-        if (STy->hasName())
-          STy->setName("");
-  }
-  SpeculativeTypes.clear();
-  SpeculativeDstOpaqueTypes.clear();
-}
-
-/// Recursively walk this pair of types, returning true if they are isomorphic,
-/// false if they are not.
-bool TypeMapTy::areTypesIsomorphic(Type *DstTy, Type *SrcTy) {
-  // Two types with differing kinds are clearly not isomorphic.
-  if (DstTy->getTypeID() != SrcTy->getTypeID())
-    return false;
-
-  // If we have an entry in the MappedTypes table, then we have our answer.
-  Type *&Entry = MappedTypes[SrcTy];
-  if (Entry)
-    return Entry == DstTy;
-
-  // Two identical types are clearly isomorphic.  Remember this
-  // non-speculatively.
-  if (DstTy == SrcTy) {
-    Entry = DstTy;
-    return true;
-  }
-
-  // Okay, we have two types with identical kinds that we haven't seen before.
-
-  // If this is an opaque struct type, special case it.
-  if (StructType *SSTy = dyn_cast<StructType>(SrcTy)) {
-    // Mapping an opaque type to any struct, just keep the dest struct.
-    if (SSTy->isOpaque()) {
-      Entry = DstTy;
-      SpeculativeTypes.push_back(SrcTy);
-      return true;
-    }
-
-    // Mapping a non-opaque source type to an opaque dest.  If this is the first
-    // type that we're mapping onto this destination type then we succeed.  Keep
-    // the dest, but fill it in later. If this is the second (different) type
-    // that we're trying to map onto the same opaque type then we fail.
-    if (cast<StructType>(DstTy)->isOpaque()) {
-      // We can only map one source type onto the opaque destination type.
-      if (!DstResolvedOpaqueTypes.insert(cast<StructType>(DstTy)).second)
-        return false;
-      SrcDefinitionsToResolve.push_back(SSTy);
-      SpeculativeTypes.push_back(SrcTy);
-      SpeculativeDstOpaqueTypes.push_back(cast<StructType>(DstTy));
-      Entry = DstTy;
-      return true;
-    }
-  }
-
-  // If the number of subtypes disagree between the two types, then we fail.
-  if (SrcTy->getNumContainedTypes() != DstTy->getNumContainedTypes())
-    return false;
-
-  // Fail if any of the extra properties (e.g. array size) of the type disagree.
-  if (isa<IntegerType>(DstTy))
-    return false; // bitwidth disagrees.
-  if (PointerType *PT = dyn_cast<PointerType>(DstTy)) {
-    if (PT->getAddressSpace() != cast<PointerType>(SrcTy)->getAddressSpace())
-      return false;
-
-  } else if (FunctionType *FT = dyn_cast<FunctionType>(DstTy)) {
-    if (FT->isVarArg() != cast<FunctionType>(SrcTy)->isVarArg())
-      return false;
-  } else if (StructType *DSTy = dyn_cast<StructType>(DstTy)) {
-    StructType *SSTy = cast<StructType>(SrcTy);
-    if (DSTy->isLiteral() != SSTy->isLiteral() ||
-        DSTy->isPacked() != SSTy->isPacked())
-      return false;
-  } else if (ArrayType *DATy = dyn_cast<ArrayType>(DstTy)) {
-    if (DATy->getNumElements() != cast<ArrayType>(SrcTy)->getNumElements())
-      return false;
-  } else if (VectorType *DVTy = dyn_cast<VectorType>(DstTy)) {
-    if (DVTy->getNumElements() != cast<VectorType>(SrcTy)->getNumElements())
-      return false;
-  }
-
-  // Otherwise, we speculate that these two types will line up and recursively
-  // check the subelements.
-  Entry = DstTy;
-  SpeculativeTypes.push_back(SrcTy);
-
-  for (unsigned I = 0, E = SrcTy->getNumContainedTypes(); I != E; ++I)
-    if (!areTypesIsomorphic(DstTy->getContainedType(I),
-                            SrcTy->getContainedType(I)))
-      return false;
-
-  // If everything seems to have lined up, then everything is great.
-  return true;
-}
-
-void TypeMapTy::linkDefinedTypeBodies() {
-  SmallVector<Type *, 16> Elements;
-  for (StructType *SrcSTy : SrcDefinitionsToResolve) {
-    StructType *DstSTy = cast<StructType>(MappedTypes[SrcSTy]);
-    assert(DstSTy->isOpaque());
-
-    // Map the body of the source type over to a new body for the dest type.
-    Elements.resize(SrcSTy->getNumElements());
-    for (unsigned I = 0, E = Elements.size(); I != E; ++I)
-      Elements[I] = get(SrcSTy->getElementType(I));
-
-    DstSTy->setBody(Elements, SrcSTy->isPacked());
-    DstStructTypesSet.switchToNonOpaque(DstSTy);
-  }
-  SrcDefinitionsToResolve.clear();
-  DstResolvedOpaqueTypes.clear();
-}
-
-void TypeMapTy::finishType(StructType *DTy, StructType *STy,
-                           ArrayRef<Type *> ETypes) {
-  DTy->setBody(ETypes, STy->isPacked());
-
-  // Steal STy's name.
-  if (STy->hasName()) {
-    SmallString<16> TmpName = STy->getName();
-    STy->setName("");
-    DTy->setName(TmpName);
-  }
-
-  DstStructTypesSet.addNonOpaque(DTy);
-}
-
-Type *TypeMapTy::get(Type *Ty) {
-  SmallPtrSet<StructType *, 8> Visited;
-  return get(Ty, Visited);
-}
-
-Type *TypeMapTy::get(Type *Ty, SmallPtrSet<StructType *, 8> &Visited) {
-  // If we already have an entry for this type, return it.
-  Type **Entry = &MappedTypes[Ty];
-  if (*Entry)
-    return *Entry;
-
-  // These are types that LLVM itself will unique.
-  bool IsUniqued = !isa<StructType>(Ty) || cast<StructType>(Ty)->isLiteral();
-
-#ifndef NDEBUG
-  if (!IsUniqued) {
-    for (auto &Pair : MappedTypes) {
-      assert(!(Pair.first != Ty && Pair.second == Ty) &&
-             "mapping to a source type");
-    }
-  }
-#endif
-
-  if (!IsUniqued && !Visited.insert(cast<StructType>(Ty)).second) {
-    StructType *DTy = StructType::create(Ty->getContext());
-    return *Entry = DTy;
-  }
-
-  // If this is not a recursive type, then just map all of the elements and
-  // then rebuild the type from inside out.
-  SmallVector<Type *, 4> ElementTypes;
-
-  // If there are no element types to map, then the type is itself.  This is
-  // true for the anonymous {} struct, things like 'float', integers, etc.
-  if (Ty->getNumContainedTypes() == 0 && IsUniqued)
-    return *Entry = Ty;
-
-  // Remap all of the elements, keeping track of whether any of them change.
-  bool AnyChange = false;
-  ElementTypes.resize(Ty->getNumContainedTypes());
-  for (unsigned I = 0, E = Ty->getNumContainedTypes(); I != E; ++I) {
-    ElementTypes[I] = get(Ty->getContainedType(I), Visited);
-    AnyChange |= ElementTypes[I] != Ty->getContainedType(I);
-  }
-
-  // If we found our type while recursively processing stuff, just use it.
-  Entry = &MappedTypes[Ty];
-  if (*Entry) {
-    if (auto *DTy = dyn_cast<StructType>(*Entry)) {
-      if (DTy->isOpaque()) {
-        auto *STy = cast<StructType>(Ty);
-        finishType(DTy, STy, ElementTypes);
-      }
-    }
-    return *Entry;
-  }
-
-  // If all of the element types mapped directly over and the type is not
-  // a nomed struct, then the type is usable as-is.
-  if (!AnyChange && IsUniqued)
-    return *Entry = Ty;
-
-  // Otherwise, rebuild a modified type.
-  switch (Ty->getTypeID()) {
-  default:
-    llvm_unreachable("unknown derived type to remap");
-  case Type::ArrayTyID:
-    return *Entry = ArrayType::get(ElementTypes[0],
-                                   cast<ArrayType>(Ty)->getNumElements());
-  case Type::VectorTyID:
-    return *Entry = VectorType::get(ElementTypes[0],
-                                    cast<VectorType>(Ty)->getNumElements());
-  case Type::PointerTyID:
-    return *Entry = PointerType::get(ElementTypes[0],
-                                     cast<PointerType>(Ty)->getAddressSpace());
-  case Type::FunctionTyID:
-    return *Entry = FunctionType::get(ElementTypes[0],
-                                      makeArrayRef(ElementTypes).slice(1),
-                                      cast<FunctionType>(Ty)->isVarArg());
-  case Type::StructTyID: {
-    auto *STy = cast<StructType>(Ty);
-    bool IsPacked = STy->isPacked();
-    if (IsUniqued)
-      return *Entry = StructType::get(Ty->getContext(), ElementTypes, IsPacked);
-
-    // If the type is opaque, we can just use it directly.
-    if (STy->isOpaque()) {
-      DstStructTypesSet.addOpaque(STy);
-      return *Entry = Ty;
-    }
-
-    if (StructType *OldT =
-            DstStructTypesSet.findNonOpaque(ElementTypes, IsPacked)) {
-      STy->setName("");
-      return *Entry = OldT;
-    }
-
-    if (!AnyChange) {
-      DstStructTypesSet.addNonOpaque(STy);
-      return *Entry = Ty;
-    }
-
-    StructType *DTy = StructType::create(Ty->getContext());
-    finishType(DTy, STy, ElementTypes);
-    return *Entry = DTy;
-  }
-  }
-}
-
-//===----------------------------------------------------------------------===//
-// ModuleLinker implementation.
-//===----------------------------------------------------------------------===//
-
 namespace {
-class ModuleLinker;
-
-/// Creates prototypes for functions that are lazily linked on the fly. This
-/// speeds up linking for modules with many/ lazily linked functions of which
-/// few get used.
-class ValueMaterializerTy final : public ValueMaterializer {
-  ModuleLinker *ModLinker;
-
-public:
-  ValueMaterializerTy(ModuleLinker *ModLinker) : ModLinker(ModLinker) {}
-
-  Value *materializeDeclFor(Value *V) override;
-  void materializeInitFor(GlobalValue *New, GlobalValue *Old) override;
-};
-
-class LinkDiagnosticInfo : public DiagnosticInfo {
-  const Twine &Msg;
-
-public:
-  LinkDiagnosticInfo(DiagnosticSeverity Severity, const Twine &Msg);
-  void print(DiagnosticPrinter &DP) const override;
-};
-LinkDiagnosticInfo::LinkDiagnosticInfo(DiagnosticSeverity Severity,
-                                       const Twine &Msg)
-    : DiagnosticInfo(DK_Linker, Severity), Msg(Msg) {}
-void LinkDiagnosticInfo::print(DiagnosticPrinter &DP) const { DP << Msg; }
 
 /// This is an implementation class for the LinkModules function, which is the
 /// entrypoint for this file.
 class ModuleLinker {
-  Module &DstM;
+  IRMover &Mover;
   Module &SrcM;
 
-  TypeMapTy TypeMap;
-  ValueMaterializerTy ValMaterializer;
-
-  /// Mapping of values from what they used to be in Src, to what they are now
-  /// in DstM.  ValueToValueMapTy is a ValueMap, which involves some overhead
-  /// due to the use of Value handles which the Linker doesn't actually need,
-  /// but this allows us to reuse the ValueMapper code.
-  ValueToValueMapTy ValueMap;
-
   SetVector<GlobalValue *> ValuesToLink;
-
-  DiagnosticHandlerFunction DiagnosticHandler;
+  StringSet<> Internalize;
 
   /// For symbol clashes, prefer those from Src.
   unsigned Flags;
@@ -413,12 +47,11 @@ class ModuleLinker {
   /// as part of a different backend compilation process.
   bool HasExportedFunctions = false;
 
-  /// Set to true when all global value body linking is complete (including
-  /// lazy linking). Used to prevent metadata linking from creating new
-  /// references.
-  bool DoneLinkingBodies = false;
-
-  bool HasError = false;
+  /// 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, IRMover::ValueAdder Add);
 
   bool shouldOverrideFromSrc() { return Flags & Linker::OverrideFromSrc; }
   bool shouldLinkOnlyNeeded() { return Flags & Linker::LinkOnlyNeeded; }
@@ -426,27 +59,18 @@ class ModuleLinker {
     return Flags & Linker::InternalizeLinkedSymbols;
   }
 
-  /// Handles cloning of a global values from the source module into
-  /// the destination module, including setting the attributes and visibility.
-  GlobalValue *copyGlobalValueProto(const GlobalValue *SGV, bool ForDefinition);
-
   /// Check if we should promote the given local value to global scope.
   bool doPromoteLocalToGlobal(const GlobalValue *SGV);
 
   bool shouldLinkFromSource(bool &LinkFromSrc, const GlobalValue &Dest,
                             const GlobalValue &Src);
 
-  /// Helper method for setting a message and returning an error code.
+  /// Should we have mover and linker error diag info?
   bool emitError(const Twine &Message) {
-    DiagnosticHandler(LinkDiagnosticInfo(DS_Error, Message));
-    HasError = true;
+    Mover.getDiagnosticHandler()(LinkDiagnosticInfo(DS_Error, Message));
     return true;
   }
 
-  void emitWarning(const Twine &Message) {
-    DiagnosticHandler(LinkDiagnosticInfo(DS_Warning, Message));
-  }
-
   bool getComdatLeader(Module &M, StringRef ComdatName,
                        const GlobalVariable *&GVar);
   bool computeResultingSelectionKind(StringRef ComdatName,
@@ -464,6 +88,7 @@ class ModuleLinker {
   /// 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(getLinkage(SrcGV)))
@@ -483,25 +108,7 @@ class ModuleLinker {
     return DGV;
   }
 
-  void computeTypeMapping();
-
   bool linkIfNeeded(GlobalValue &GV);
-  Constant *linkAppendingVarProto(GlobalVariable *DstGV,
-                                  const GlobalVariable *SrcGV);
-
-  Constant *linkGlobalValueProto(GlobalValue *GV);
-  bool linkModuleFlagsMetadata();
-
-  void linkGlobalInit(GlobalVariable &Dst, GlobalVariable &Src);
-  bool linkFunctionBody(Function &Dst, Function &Src);
-  void linkAliasBody(GlobalAlias &Dst, GlobalAlias &Src);
-  bool linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src);
-
-  /// Functions that take care of cloning a specific global value type
-  /// into the destination module.
-  GlobalVariable *copyGlobalVariableProto(const GlobalVariable *SGVar);
-  Function *copyFunctionProto(const Function *SF);
-  GlobalValue *copyGlobalAliasProto(const GlobalAlias *SGA);
 
   /// Helper methods to check if we are importing from or potentially
   /// exporting from the current source module.
@@ -517,6 +124,13 @@ class ModuleLinker {
   /// a local that is being promoted to global scope.
   std::string getName(const GlobalValue *SGV);
 
+  /// Process globals so that they can be used in ThinLTO. This includes
+  /// promoting local variables so that they can be reference externally by
+  /// thin lto imported globals and converting strong external globals to
+  /// available_externally.
+  void processGlobalsForThinLTO();
+  void processGlobalForThinLTO(GlobalValue &GV);
+
   /// Get the new linkage for SGV that should be used in the linked destination
   /// module. Specifically, for ThinLTO importing or exporting it may need
   /// to be adjusted.
@@ -532,15 +146,11 @@ class ModuleLinker {
   void setVisibility(GlobalValue *NewGV, const GlobalValue *SGV,
                      const GlobalValue *DGV = nullptr);
 
-  void linkNamedMDNodes();
-
 public:
-  ModuleLinker(Module &DstM, Linker::IdentifiedStructTypeSet &Set, Module &SrcM,
-               DiagnosticHandlerFunction DiagnosticHandler, unsigned Flags,
+  ModuleLinker(IRMover &Mover, Module &SrcM, unsigned Flags,
                const FunctionInfoIndex *Index = nullptr,
                DenseSet<const GlobalValue *> *FunctionsToImport = nullptr)
-      : DstM(DstM), SrcM(SrcM), TypeMap(Set), ValMaterializer(this),
-        DiagnosticHandler(DiagnosticHandler), Flags(Flags), ImportIndex(Index),
+      : Mover(Mover), SrcM(SrcM), Flags(Flags), ImportIndex(Index),
         ImportFunction(FunctionsToImport) {
     assert((ImportIndex || !ImportFunction) &&
            "Expect a FunctionInfoIndex when importing");
@@ -553,8 +163,6 @@ public:
   }
 
   bool run();
-  Value *materializeDeclFor(Value *V);
-  void materializeInitFor(GlobalValue *New, GlobalValue *Old);
 };
 }
 
@@ -755,41 +363,6 @@ GlobalValue::LinkageTypes ModuleLinker::
   llvm_unreachable("unknown linkage type");
 }
 
-/// Loop through the global variables in the src module and merge them into the
-/// dest module.
-GlobalVariable *
-ModuleLinker::copyGlobalVariableProto(const GlobalVariable *SGVar) {
-  // No linking to be performed or linking from the source: simply create an
-  // identical version of the symbol over in the dest module... the
-  // initializer will be filled in later by LinkGlobalInits.
-  GlobalVariable *NewDGV =
-      new GlobalVariable(DstM, TypeMap.get(SGVar->getType()->getElementType()),
-                         SGVar->isConstant(), GlobalValue::ExternalLinkage,
-                         /*init*/ nullptr, getName(SGVar),
-                         /*insertbefore*/ nullptr, SGVar->getThreadLocalMode(),
-                         SGVar->getType()->getAddressSpace());
-
-  return NewDGV;
-}
-
-/// Link the function in the source module into the destination module if
-/// needed, setting up mapping information.
-Function *ModuleLinker::copyFunctionProto(const Function *SF) {
-  // If there is no linkage to be performed or we are linking from the source,
-  // bring SF over.
-  return Function::Create(TypeMap.get(SF->getFunctionType()),
-                          GlobalValue::ExternalLinkage, getName(SF), &DstM);
-}
-
-/// Set up prototypes for any aliases that come over from the source module.
-GlobalValue *ModuleLinker::copyGlobalAliasProto(const GlobalAlias *SGA) {
-  // If there is no linkage to be performed or we're linking from the source,
-  // bring over SGA.
-  auto *Ty = TypeMap.get(SGA->getValueType());
-  return GlobalAlias::create(Ty, SGA->getType()->getPointerAddressSpace(),
-                             GlobalValue::ExternalLinkage, getName(SGA), &DstM);
-}
-
 static GlobalValue::VisibilityTypes
 getMinVisibility(GlobalValue::VisibilityTypes A,
                  GlobalValue::VisibilityTypes B) {
@@ -813,82 +386,6 @@ void ModuleLinker::setVisibility(GlobalV
   NewGV->setVisibility(Visibility);
 }
 
-GlobalValue *ModuleLinker::copyGlobalValueProto(const GlobalValue *SGV,
-                                                bool ForDefinition) {
-  GlobalValue *NewGV;
-  if (auto *SGVar = dyn_cast<GlobalVariable>(SGV)) {
-    NewGV = copyGlobalVariableProto(SGVar);
-  } else if (auto *SF = dyn_cast<Function>(SGV)) {
-    NewGV = copyFunctionProto(SF);
-  } else {
-    if (ForDefinition)
-      NewGV = copyGlobalAliasProto(cast<GlobalAlias>(SGV));
-    else
-      NewGV = new GlobalVariable(
-          DstM, TypeMap.get(SGV->getType()->getElementType()),
-          /*isConstant*/ false, GlobalValue::ExternalLinkage,
-          /*init*/ nullptr, getName(SGV),
-          /*insertbefore*/ nullptr, SGV->getThreadLocalMode(),
-          SGV->getType()->getAddressSpace());
-  }
-
-  if (ForDefinition)
-    NewGV->setLinkage(getLinkage(SGV));
-  else if (SGV->hasAvailableExternallyLinkage() || SGV->hasWeakLinkage() ||
-           SGV->hasLinkOnceLinkage())
-    NewGV->setLinkage(GlobalValue::ExternalWeakLinkage);
-
-  copyGVAttributes(NewGV, SGV);
-  return NewGV;
-}
-
-Value *ValueMaterializerTy::materializeDeclFor(Value *V) {
-  return ModLinker->materializeDeclFor(V);
-}
-
-Value *ModuleLinker::materializeDeclFor(Value *V) {
-  auto *SGV = dyn_cast<GlobalValue>(V);
-  if (!SGV)
-    return nullptr;
-
-  return linkGlobalValueProto(SGV);
-}
-
-void ValueMaterializerTy::materializeInitFor(GlobalValue *New,
-                                             GlobalValue *Old) {
-  return ModLinker->materializeInitFor(New, Old);
-}
-
-static bool shouldLazyLink(const GlobalValue &GV) {
-  return GV.hasLocalLinkage() || GV.hasLinkOnceLinkage() ||
-         GV.hasAvailableExternallyLinkage();
-}
-
-void ModuleLinker::materializeInitFor(GlobalValue *New, GlobalValue *Old) {
-  if (auto *F = dyn_cast<Function>(New)) {
-    if (!F->isDeclaration())
-      return;
-  } else if (auto *V = dyn_cast<GlobalVariable>(New)) {
-    if (V->hasInitializer())
-      return;
-  } else {
-    auto *A = cast<GlobalAlias>(New);
-    if (A->getAliasee())
-      return;
-  }
-
-  if (Old->isDeclaration())
-    return;
-
-  if (isPerformingImport() && !doImportAsDefinition(Old))
-    return;
-
-  if (!ValuesToLink.count(Old) && !shouldLazyLink(*Old))
-    return;
-
-  linkGlobalValueBody(*New, *Old);
-}
-
 bool ModuleLinker::getComdatLeader(Module &M, StringRef ComdatName,
                                    const GlobalVariable *&GVar) {
   const GlobalValue *GVal = M.getNamedValue(ComdatName);
@@ -914,6 +411,7 @@ bool ModuleLinker::computeResultingSelec
                                                  Comdat::SelectionKind Dst,
                                                  Comdat::SelectionKind &Result,
                                                  bool &LinkFromSrc) {
+  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 ||
@@ -981,6 +479,7 @@ bool ModuleLinker::computeResultingSelec
 bool ModuleLinker::getComdatResult(const Comdat *SrcC,
                                    Comdat::SelectionKind &Result,
                                    bool &LinkFromSrc) {
+  Module &DstM = Mover.getModule();
   Comdat::SelectionKind SSK = SrcC->getSelectionKind();
   StringRef ComdatName = SrcC->getName();
   Module::ComdatSymTabType &ComdatSymTab = DstM.getComdatSymbolTable();
@@ -1110,601 +609,6 @@ bool ModuleLinker::shouldLinkFromSource(
                    "': symbol multiply defined!");
 }
 
-/// Loop over all of the linked values to compute type mappings.  For example,
-/// if we link "extern Foo *x" and "Foo *x = NULL", then we have two struct
-/// types 'Foo' but one got renamed when the module was loaded into the same
-/// LLVMContext.
-void ModuleLinker::computeTypeMapping() {
-  for (GlobalValue &SGV : SrcM.globals()) {
-    GlobalValue *DGV = getLinkedToGlobal(&SGV);
-    if (!DGV)
-      continue;
-
-    if (!DGV->hasAppendingLinkage() || !SGV.hasAppendingLinkage()) {
-      TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
-      continue;
-    }
-
-    // Unify the element type of appending arrays.
-    ArrayType *DAT = cast<ArrayType>(DGV->getType()->getElementType());
-    ArrayType *SAT = cast<ArrayType>(SGV.getType()->getElementType());
-    TypeMap.addTypeMapping(DAT->getElementType(), SAT->getElementType());
-  }
-
-  for (GlobalValue &SGV : SrcM) {
-    if (GlobalValue *DGV = getLinkedToGlobal(&SGV))
-      TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
-  }
-
-  for (GlobalValue &SGV : SrcM.aliases()) {
-    if (GlobalValue *DGV = getLinkedToGlobal(&SGV))
-      TypeMap.addTypeMapping(DGV->getType(), SGV.getType());
-  }
-
-  // Incorporate types by name, scanning all the types in the source module.
-  // At this point, the destination module may have a type "%foo = { i32 }" for
-  // example.  When the source module got loaded into the same LLVMContext, if
-  // it had the same type, it would have been renamed to "%foo.42 = { i32 }".
-  std::vector<StructType *> Types = SrcM.getIdentifiedStructTypes();
-  for (StructType *ST : Types) {
-    if (!ST->hasName())
-      continue;
-
-    // Check to see if there is a dot in the name followed by a digit.
-    size_t DotPos = ST->getName().rfind('.');
-    if (DotPos == 0 || DotPos == StringRef::npos ||
-        ST->getName().back() == '.' ||
-        !isdigit(static_cast<unsigned char>(ST->getName()[DotPos + 1])))
-      continue;
-
-    // Check to see if the destination module has a struct with the prefix name.
-    StructType *DST = DstM.getTypeByName(ST->getName().substr(0, DotPos));
-    if (!DST)
-      continue;
-
-    // Don't use it if this actually came from the source module. They're in
-    // the same LLVMContext after all. Also don't use it unless the type is
-    // actually used in the destination module. This can happen in situations
-    // like this:
-    //
-    //      Module A                         Module B
-    //      --------                         --------
-    //   %Z = type { %A }                %B = type { %C.1 }
-    //   %A = type { %B.1, [7 x i8] }    %C.1 = type { i8* }
-    //   %B.1 = type { %C }              %A.2 = type { %B.3, [5 x i8] }
-    //   %C = type { i8* }               %B.3 = type { %C.1 }
-    //
-    // When we link Module B with Module A, the '%B' in Module B is
-    // used. However, that would then use '%C.1'. But when we process '%C.1',
-    // we prefer to take the '%C' version. So we are then left with both
-    // '%C.1' and '%C' being used for the same types. This leads to some
-    // variables using one type and some using the other.
-    if (TypeMap.DstStructTypesSet.hasType(DST))
-      TypeMap.addTypeMapping(DST, ST);
-  }
-
-  // Now that we have discovered all of the type equivalences, get a body for
-  // any 'opaque' types in the dest module that are now resolved.
-  TypeMap.linkDefinedTypeBodies();
-}
-
-static void getArrayElements(const Constant *C,
-                             SmallVectorImpl<Constant *> &Dest) {
-  unsigned NumElements = cast<ArrayType>(C->getType())->getNumElements();
-
-  for (unsigned i = 0; i != NumElements; ++i)
-    Dest.push_back(C->getAggregateElement(i));
-}
-
-/// If there were any appending global variables, link them together now.
-/// Return true on error.
-Constant *ModuleLinker::linkAppendingVarProto(GlobalVariable *DstGV,
-                                              const GlobalVariable *SrcGV) {
-  Type *EltTy = cast<ArrayType>(TypeMap.get(SrcGV->getType()->getElementType()))
-                    ->getElementType();
-
-  StringRef Name = SrcGV->getName();
-  bool IsNewStructor = false;
-  bool IsOldStructor = false;
-  if (Name == "llvm.global_ctors" || Name == "llvm.global_dtors") {
-    if (cast<StructType>(EltTy)->getNumElements() == 3)
-      IsNewStructor = true;
-    else
-      IsOldStructor = true;
-  }
-
-  PointerType *VoidPtrTy = Type::getInt8Ty(SrcGV->getContext())->getPointerTo();
-  if (IsOldStructor) {
-    auto &ST = *cast<StructType>(EltTy);
-    Type *Tys[3] = {ST.getElementType(0), ST.getElementType(1), VoidPtrTy};
-    EltTy = StructType::get(SrcGV->getContext(), Tys, false);
-  }
-
-  if (DstGV) {
-    ArrayType *DstTy = cast<ArrayType>(DstGV->getType()->getElementType());
-
-    if (!SrcGV->hasAppendingLinkage() || !DstGV->hasAppendingLinkage()) {
-      emitError(
-          "Linking globals named '" + SrcGV->getName() +
-          "': can only link appending global with another appending global!");
-      return nullptr;
-    }
-
-    // Check to see that they two arrays agree on type.
-    if (EltTy != DstTy->getElementType()) {
-      emitError("Appending variables with different element types!");
-      return nullptr;
-    }
-    if (DstGV->isConstant() != SrcGV->isConstant()) {
-      emitError("Appending variables linked with different const'ness!");
-      return nullptr;
-    }
-
-    if (DstGV->getAlignment() != SrcGV->getAlignment()) {
-      emitError(
-          "Appending variables with different alignment need to be linked!");
-      return nullptr;
-    }
-
-    if (DstGV->getVisibility() != SrcGV->getVisibility()) {
-      emitError(
-          "Appending variables with different visibility need to be linked!");
-      return nullptr;
-    }
-
-    if (DstGV->hasUnnamedAddr() != SrcGV->hasUnnamedAddr()) {
-      emitError(
-          "Appending variables with different unnamed_addr need to be linked!");
-      return nullptr;
-    }
-
-    if (StringRef(DstGV->getSection()) != SrcGV->getSection()) {
-      emitError(
-          "Appending variables with different section name need to be linked!");
-      return nullptr;
-    }
-  }
-
-  SmallVector<Constant *, 16> DstElements;
-  if (DstGV)
-    getArrayElements(DstGV->getInitializer(), DstElements);
-
-  SmallVector<Constant *, 16> SrcElements;
-  getArrayElements(SrcGV->getInitializer(), SrcElements);
-
-  if (IsNewStructor)
-    SrcElements.erase(
-        std::remove_if(SrcElements.begin(), SrcElements.end(),
-                       [this](Constant *E) {
-                         auto *Key = dyn_cast<GlobalValue>(
-                             E->getAggregateElement(2)->stripPointerCasts());
-                         return Key && !ValuesToLink.count(Key) &&
-                                !shouldLazyLink(*Key);
-                       }),
-        SrcElements.end());
-  uint64_t NewSize = DstElements.size() + SrcElements.size();
-  ArrayType *NewType = ArrayType::get(EltTy, NewSize);
-
-  // Create the new global variable.
-  GlobalVariable *NG = new GlobalVariable(
-      DstM, NewType, SrcGV->isConstant(), SrcGV->getLinkage(),
-      /*init*/ nullptr, /*name*/ "", DstGV, SrcGV->getThreadLocalMode(),
-      SrcGV->getType()->getAddressSpace());
-
-  // Propagate alignment, visibility and section info.
-  copyGVAttributes(NG, SrcGV);
-
-  Constant *Ret = ConstantExpr::getBitCast(NG, TypeMap.get(SrcGV->getType()));
-
-  // Stop recursion.
-  ValueMap[SrcGV] = Ret;
-
-  for (auto *V : SrcElements) {
-    Constant *NewV;
-    if (IsOldStructor) {
-      auto *S = cast<ConstantStruct>(V);
-      auto *E1 = MapValue(S->getOperand(0), ValueMap, RF_MoveDistinctMDs,
-                          &TypeMap, &ValMaterializer);
-      auto *E2 = MapValue(S->getOperand(1), ValueMap, RF_MoveDistinctMDs,
-                          &TypeMap, &ValMaterializer);
-      Value *Null = Constant::getNullValue(VoidPtrTy);
-      NewV =
-          ConstantStruct::get(cast<StructType>(EltTy), E1, E2, Null, nullptr);
-    } else {
-      NewV =
-          MapValue(V, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
-    }
-    DstElements.push_back(NewV);
-  }
-
-  NG->setInitializer(ConstantArray::get(NewType, DstElements));
-
-  // Replace any uses of the two global variables with uses of the new
-  // global.
-  if (DstGV) {
-    DstGV->replaceAllUsesWith(ConstantExpr::getBitCast(NG, DstGV->getType()));
-    DstGV->eraseFromParent();
-  }
-
-  return Ret;
-}
-
-Constant *ModuleLinker::linkGlobalValueProto(GlobalValue *SGV) {
-  GlobalValue *DGV = getLinkedToGlobal(SGV);
-
-  // Handle the ultra special appending linkage case first.
-  assert(!DGV || SGV->hasAppendingLinkage() == DGV->hasAppendingLinkage());
-  if (SGV->hasAppendingLinkage()) {
-    // Should have prevented importing for appending linkage in linkIfNeeded.
-    assert(!isPerformingImport());
-    return linkAppendingVarProto(cast_or_null<GlobalVariable>(DGV),
-                                 cast<GlobalVariable>(SGV));
-  }
-
-  bool LinkFromSrc = true;
-  Comdat *C = nullptr;
-  bool HasUnnamedAddr = SGV->hasUnnamedAddr();
-
-  if (isPerformingImport() && !doImportAsDefinition(SGV)) {
-    LinkFromSrc = false;
-  } else if (const Comdat *SC = SGV->getComdat()) {
-    Comdat::SelectionKind SK;
-    std::tie(SK, LinkFromSrc) = ComdatsChosen[SC];
-    C = DstM.getOrInsertComdat(SC->getName());
-    C->setSelectionKind(SK);
-    if (SGV->hasLocalLinkage())
-      LinkFromSrc = true;
-  } else if (DGV) {
-    if (shouldLinkFromSource(LinkFromSrc, *DGV, *SGV))
-      return nullptr;
-  }
-
-  if (DGV)
-    HasUnnamedAddr = HasUnnamedAddr && DGV->hasUnnamedAddr();
-
-  GlobalValue *NewGV;
-  if (!LinkFromSrc && DGV) {
-    NewGV = DGV;
-  } else {
-    // If we are done linking global value bodies (i.e. we are performing
-    // metadata linking), don't link in the global value due to this
-    // reference, simply map it to null.
-    if (DoneLinkingBodies)
-      return nullptr;
-
-    NewGV = copyGlobalValueProto(SGV, LinkFromSrc);
-  }
-
-  setVisibility(NewGV, SGV, DGV);
-  NewGV->setUnnamedAddr(HasUnnamedAddr);
-
-  if (auto *NewGO = dyn_cast<GlobalObject>(NewGV)) {
-    if (C && LinkFromSrc)
-      NewGO->setComdat(C);
-
-    if (DGV && DGV->hasCommonLinkage() && SGV->hasCommonLinkage())
-      NewGO->setAlignment(std::max(DGV->getAlignment(), SGV->getAlignment()));
-  }
-
-  if (auto *NewGVar = dyn_cast<GlobalVariable>(NewGV)) {
-    auto *DGVar = dyn_cast_or_null<GlobalVariable>(DGV);
-    auto *SGVar = dyn_cast<GlobalVariable>(SGV);
-    if (DGVar && SGVar && DGVar->isDeclaration() && SGVar->isDeclaration() &&
-        (!DGVar->isConstant() || !SGVar->isConstant()))
-      NewGVar->setConstant(false);
-  }
-
-  if (NewGV != DGV && DGV) {
-    DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, DGV->getType()));
-    DGV->eraseFromParent();
-  }
-
-  return ConstantExpr::getBitCast(NewGV, TypeMap.get(SGV->getType()));
-}
-
-/// Update the initializers in the Dest module now that all globals that may be
-/// referenced are in Dest.
-void ModuleLinker::linkGlobalInit(GlobalVariable &Dst, GlobalVariable &Src) {
-  // Figure out what the initializer looks like in the dest module.
-  Dst.setInitializer(MapValue(Src.getInitializer(), ValueMap,
-                              RF_MoveDistinctMDs, &TypeMap, &ValMaterializer));
-}
-
-/// Copy the source function over into the dest function and fix up references
-/// to values. At this point we know that Dest is an external function, and
-/// that Src is not.
-bool ModuleLinker::linkFunctionBody(Function &Dst, Function &Src) {
-  assert(Dst.isDeclaration() && !Src.isDeclaration());
-
-  // Materialize if needed.
-  if (std::error_code EC = Src.materialize())
-    return emitError(EC.message());
-
-  // Link in the prefix data.
-  if (Src.hasPrefixData())
-    Dst.setPrefixData(MapValue(Src.getPrefixData(), ValueMap,
-                               RF_MoveDistinctMDs, &TypeMap, &ValMaterializer));
-
-  // Link in the prologue data.
-  if (Src.hasPrologueData())
-    Dst.setPrologueData(MapValue(Src.getPrologueData(), ValueMap,
-                                 RF_MoveDistinctMDs, &TypeMap,
-                                 &ValMaterializer));
-
-  // Link in the personality function.
-  if (Src.hasPersonalityFn())
-    Dst.setPersonalityFn(MapValue(Src.getPersonalityFn(), ValueMap,
-                                  RF_MoveDistinctMDs, &TypeMap,
-                                  &ValMaterializer));
-
-  // Go through and convert function arguments over, remembering the mapping.
-  Function::arg_iterator DI = Dst.arg_begin();
-  for (Argument &Arg : Src.args()) {
-    DI->setName(Arg.getName()); // Copy the name over.
-
-    // Add a mapping to our mapping.
-    ValueMap[&Arg] = &*DI;
-    ++DI;
-  }
-
-  // Copy over the metadata attachments.
-  SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
-  Src.getAllMetadata(MDs);
-  for (const auto &I : MDs)
-    Dst.setMetadata(I.first, MapMetadata(I.second, ValueMap, RF_MoveDistinctMDs,
-                                         &TypeMap, &ValMaterializer));
-
-  // Splice the body of the source function into the dest function.
-  Dst.getBasicBlockList().splice(Dst.end(), Src.getBasicBlockList());
-
-  // At this point, all of the instructions and values of the function are now
-  // copied over.  The only problem is that they are still referencing values in
-  // the Source function as operands.  Loop through all of the operands of the
-  // functions and patch them up to point to the local versions.
-  for (BasicBlock &BB : Dst)
-    for (Instruction &I : BB)
-      RemapInstruction(&I, ValueMap,
-                       RF_IgnoreMissingEntries | RF_MoveDistinctMDs, &TypeMap,
-                       &ValMaterializer);
-
-  // There is no need to map the arguments anymore.
-  for (Argument &Arg : Src.args())
-    ValueMap.erase(&Arg);
-
-  Src.dematerialize();
-  return false;
-}
-
-void ModuleLinker::linkAliasBody(GlobalAlias &Dst, GlobalAlias &Src) {
-  Constant *Aliasee = Src.getAliasee();
-  Constant *Val = MapValue(Aliasee, ValueMap, RF_MoveDistinctMDs, &TypeMap,
-                           &ValMaterializer);
-  Dst.setAliasee(Val);
-}
-
-bool ModuleLinker::linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src) {
-  if (const Comdat *SC = Src.getComdat()) {
-    // To ensure that we don't generate an incomplete comdat group,
-    // we must materialize and map in any other members that are not
-    // yet materialized in Dst, which also ensures their definitions
-    // are linked in. Otherwise, linkonce and other lazy linked GVs will
-    // not be materialized if they aren't referenced.
-    for (auto *SGV : ComdatMembers[SC]) {
-      auto *DGV = cast_or_null<GlobalValue>(ValueMap.lookup(SGV));
-      if (DGV && !DGV->isDeclaration())
-        continue;
-      MapValue(SGV, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
-    }
-  }
-  if (shouldInternalizeLinkedSymbols())
-    if (auto *DGV = dyn_cast<GlobalValue>(&Dst))
-      DGV->setLinkage(GlobalValue::InternalLinkage);
-  if (auto *F = dyn_cast<Function>(&Src))
-    return linkFunctionBody(cast<Function>(Dst), *F);
-  if (auto *GVar = dyn_cast<GlobalVariable>(&Src)) {
-    linkGlobalInit(cast<GlobalVariable>(Dst), *GVar);
-    return false;
-  }
-  linkAliasBody(cast<GlobalAlias>(Dst), cast<GlobalAlias>(Src));
-  return false;
-}
-
-/// Insert all of the named MDNodes in Src into the Dest module.
-void ModuleLinker::linkNamedMDNodes() {
-  const NamedMDNode *SrcModFlags = SrcM.getModuleFlagsMetadata();
-  for (const NamedMDNode &NMD : SrcM.named_metadata()) {
-    // Don't link module flags here. Do them separately.
-    if (&NMD == SrcModFlags)
-      continue;
-    NamedMDNode *DestNMD = DstM.getOrInsertNamedMetadata(NMD.getName());
-    // Add Src elements into Dest node.
-    for (const MDNode *op : NMD.operands())
-      DestNMD->addOperand(MapMetadata(
-          op, ValueMap, RF_MoveDistinctMDs | RF_NullMapMissingGlobalValues,
-          &TypeMap, &ValMaterializer));
-  }
-}
-
-/// Merge the linker flags in Src into the Dest module.
-bool ModuleLinker::linkModuleFlagsMetadata() {
-  // If the source module has no module flags, we are done.
-  const NamedMDNode *SrcModFlags = SrcM.getModuleFlagsMetadata();
-  if (!SrcModFlags)
-    return false;
-
-  // If the destination module doesn't have module flags yet, then just copy
-  // over the source module's flags.
-  NamedMDNode *DstModFlags = DstM.getOrInsertModuleFlagsMetadata();
-  if (DstModFlags->getNumOperands() == 0) {
-    for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I)
-      DstModFlags->addOperand(SrcModFlags->getOperand(I));
-
-    return false;
-  }
-
-  // First build a map of the existing module flags and requirements.
-  DenseMap<MDString *, std::pair<MDNode *, unsigned>> Flags;
-  SmallSetVector<MDNode *, 16> Requirements;
-  for (unsigned I = 0, E = DstModFlags->getNumOperands(); I != E; ++I) {
-    MDNode *Op = DstModFlags->getOperand(I);
-    ConstantInt *Behavior = mdconst::extract<ConstantInt>(Op->getOperand(0));
-    MDString *ID = cast<MDString>(Op->getOperand(1));
-
-    if (Behavior->getZExtValue() == Module::Require) {
-      Requirements.insert(cast<MDNode>(Op->getOperand(2)));
-    } else {
-      Flags[ID] = std::make_pair(Op, I);
-    }
-  }
-
-  // Merge in the flags from the source module, and also collect its set of
-  // requirements.
-  for (unsigned I = 0, E = SrcModFlags->getNumOperands(); I != E; ++I) {
-    MDNode *SrcOp = SrcModFlags->getOperand(I);
-    ConstantInt *SrcBehavior =
-        mdconst::extract<ConstantInt>(SrcOp->getOperand(0));
-    MDString *ID = cast<MDString>(SrcOp->getOperand(1));
-    MDNode *DstOp;
-    unsigned DstIndex;
-    std::tie(DstOp, DstIndex) = Flags.lookup(ID);
-    unsigned SrcBehaviorValue = SrcBehavior->getZExtValue();
-
-    // If this is a requirement, add it and continue.
-    if (SrcBehaviorValue == Module::Require) {
-      // If the destination module does not already have this requirement, add
-      // it.
-      if (Requirements.insert(cast<MDNode>(SrcOp->getOperand(2)))) {
-        DstModFlags->addOperand(SrcOp);
-      }
-      continue;
-    }
-
-    // If there is no existing flag with this ID, just add it.
-    if (!DstOp) {
-      Flags[ID] = std::make_pair(SrcOp, DstModFlags->getNumOperands());
-      DstModFlags->addOperand(SrcOp);
-      continue;
-    }
-
-    // Otherwise, perform a merge.
-    ConstantInt *DstBehavior =
-        mdconst::extract<ConstantInt>(DstOp->getOperand(0));
-    unsigned DstBehaviorValue = DstBehavior->getZExtValue();
-
-    // If either flag has override behavior, handle it first.
-    if (DstBehaviorValue == Module::Override) {
-      // Diagnose inconsistent flags which both have override behavior.
-      if (SrcBehaviorValue == Module::Override &&
-          SrcOp->getOperand(2) != DstOp->getOperand(2)) {
-        emitError("linking module flags '" + ID->getString() +
-                  "': IDs have conflicting override values");
-      }
-      continue;
-    } else if (SrcBehaviorValue == Module::Override) {
-      // Update the destination flag to that of the source.
-      DstModFlags->setOperand(DstIndex, SrcOp);
-      Flags[ID].first = SrcOp;
-      continue;
-    }
-
-    // Diagnose inconsistent merge behavior types.
-    if (SrcBehaviorValue != DstBehaviorValue) {
-      emitError("linking module flags '" + ID->getString() +
-                "': IDs have conflicting behaviors");
-      continue;
-    }
-
-    auto replaceDstValue = [&](MDNode *New) {
-      Metadata *FlagOps[] = {DstOp->getOperand(0), ID, New};
-      MDNode *Flag = MDNode::get(DstM.getContext(), FlagOps);
-      DstModFlags->setOperand(DstIndex, Flag);
-      Flags[ID].first = Flag;
-    };
-
-    // Perform the merge for standard behavior types.
-    switch (SrcBehaviorValue) {
-    case Module::Require:
-    case Module::Override:
-      llvm_unreachable("not possible");
-    case Module::Error: {
-      // Emit an error if the values differ.
-      if (SrcOp->getOperand(2) != DstOp->getOperand(2)) {
-        emitError("linking module flags '" + ID->getString() +
-                  "': IDs have conflicting values");
-      }
-      continue;
-    }
-    case Module::Warning: {
-      // Emit a warning if the values differ.
-      if (SrcOp->getOperand(2) != DstOp->getOperand(2)) {
-        emitWarning("linking module flags '" + ID->getString() +
-                    "': IDs have conflicting values");
-      }
-      continue;
-    }
-    case Module::Append: {
-      MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
-      MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
-      SmallVector<Metadata *, 8> MDs;
-      MDs.reserve(DstValue->getNumOperands() + SrcValue->getNumOperands());
-      MDs.append(DstValue->op_begin(), DstValue->op_end());
-      MDs.append(SrcValue->op_begin(), SrcValue->op_end());
-
-      replaceDstValue(MDNode::get(DstM.getContext(), MDs));
-      break;
-    }
-    case Module::AppendUnique: {
-      SmallSetVector<Metadata *, 16> Elts;
-      MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
-      MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
-      Elts.insert(DstValue->op_begin(), DstValue->op_end());
-      Elts.insert(SrcValue->op_begin(), SrcValue->op_end());
-
-      replaceDstValue(MDNode::get(DstM.getContext(),
-                                  makeArrayRef(Elts.begin(), Elts.end())));
-      break;
-    }
-    }
-  }
-
-  // Check all of the requirements.
-  for (unsigned I = 0, E = Requirements.size(); I != E; ++I) {
-    MDNode *Requirement = Requirements[I];
-    MDString *Flag = cast<MDString>(Requirement->getOperand(0));
-    Metadata *ReqValue = Requirement->getOperand(1);
-
-    MDNode *Op = Flags[Flag].first;
-    if (!Op || Op->getOperand(2) != ReqValue) {
-      emitError("linking module flags '" + Flag->getString() +
-                "': does not have the required value");
-      continue;
-    }
-  }
-
-  return HasError;
-}
-
-// This function returns true if the triples match.
-static bool triplesMatch(const Triple &T0, const Triple &T1) {
-  // If vendor is apple, ignore the version number.
-  if (T0.getVendor() == Triple::Apple)
-    return T0.getArch() == T1.getArch() && T0.getSubArch() == T1.getSubArch() &&
-           T0.getVendor() == T1.getVendor() && T0.getOS() == T1.getOS();
-
-  return T0 == T1;
-}
-
-// This function returns the merged triple.
-static std::string mergeTriples(const Triple &SrcTriple,
-                                const Triple &DstTriple) {
-  // If vendor is apple, pick the triple with the larger version number.
-  if (SrcTriple.getVendor() == Triple::Apple)
-    if (DstTriple.isOSVersionLT(SrcTriple))
-      return SrcTriple.str();
-
-  return DstTriple.str();
-}
-
 bool ModuleLinker::linkIfNeeded(GlobalValue &GV) {
   GlobalValue *DGV = getLinkedToGlobal(&GV);
 
@@ -1772,47 +676,49 @@ bool ModuleLinker::linkIfNeeded(GlobalVa
   return false;
 }
 
-bool ModuleLinker::run() {
-  // Inherit the target data from the source module if the destination module
-  // doesn't have one already.
-  if (DstM.getDataLayout().isDefault())
-    DstM.setDataLayout(SrcM.getDataLayout());
-
-  if (SrcM.getDataLayout() != DstM.getDataLayout()) {
-    emitWarning("Linking two modules of different data layouts: '" +
-                SrcM.getModuleIdentifier() + "' is '" +
-                SrcM.getDataLayoutStr() + "' whereas '" +
-                DstM.getModuleIdentifier() + "' is '" +
-                DstM.getDataLayoutStr() + "'\n");
-  }
-
-  // Copy the target triple from the source to dest if the dest's is empty.
-  if (DstM.getTargetTriple().empty() && !SrcM.getTargetTriple().empty())
-    DstM.setTargetTriple(SrcM.getTargetTriple());
-
-  Triple SrcTriple(SrcM.getTargetTriple()), DstTriple(DstM.getTargetTriple());
-
-  if (!SrcM.getTargetTriple().empty() && !triplesMatch(SrcTriple, DstTriple))
-    emitWarning("Linking two modules of different target triples: " +
-                SrcM.getModuleIdentifier() + "' is '" + SrcM.getTargetTriple() +
-                "' whereas '" + DstM.getModuleIdentifier() + "' is '" +
-                DstM.getTargetTriple() + "'\n");
-
-  DstM.setTargetTriple(mergeTriples(SrcTriple, DstTriple));
-
-  // Append the module inline asm string.
-  if (!SrcM.getModuleInlineAsm().empty()) {
-    if (DstM.getModuleInlineAsm().empty())
-      DstM.setModuleInlineAsm(SrcM.getModuleInlineAsm());
-    else
-      DstM.setModuleInlineAsm(DstM.getModuleInlineAsm() + "\n" +
-                              SrcM.getModuleInlineAsm());
+void ModuleLinker::addLazyFor(GlobalValue &GV, IRMover::ValueAdder Add) {
+  // Add these to the internalize list
+  if (!GV.hasLinkOnceLinkage())
+    return;
+
+  if (shouldInternalizeLinkedSymbols())
+    Internalize.insert(GV.getName());
+  Add(GV);
+
+  const Comdat *SC = GV.getComdat();
+  if (!SC)
+    return;
+  for (GlobalValue *GV2 : ComdatMembers[SC]) {
+    if (!GV2->hasLocalLinkage() && shouldInternalizeLinkedSymbols())
+      Internalize.insert(GV2->getName());
+    Add(*GV2);
   }
+}
 
-  // Loop over all of the linked values to compute type mappings.
-  computeTypeMapping();
+void ModuleLinker::processGlobalForThinLTO(GlobalValue &GV) {
+  if (GV.hasLocalLinkage() &&
+      (doPromoteLocalToGlobal(&GV) || isPerformingImport())) {
+    GV.setName(getName(&GV));
+    GV.setLinkage(getLinkage(&GV));
+    if (!GV.hasLocalLinkage())
+      GV.setVisibility(GlobalValue::HiddenVisibility);
+    if (isModuleExporting())
+      ValuesToLink.insert(&GV);
+    return;
+  }
+  GV.setLinkage(getLinkage(&GV));
+}
 
-  ComdatsChosen.clear();
+void ModuleLinker::processGlobalsForThinLTO() {
+  for (GlobalVariable &GV : SrcM.globals())
+    processGlobalForThinLTO(GV);
+  for (Function &SF : SrcM)
+    processGlobalForThinLTO(SF);
+  for (GlobalAlias &GA : SrcM.aliases())
+    processGlobalForThinLTO(GA);
+}
+
+bool ModuleLinker::run() {
   for (const auto &SMEC : SrcM.getComdatSymbolTable()) {
     const Comdat &C = SMEC.getValue();
     if (ComdatsChosen.count(&C))
@@ -1850,138 +756,45 @@ bool ModuleLinker::run() {
     if (linkIfNeeded(GA))
       return true;
 
-  for (GlobalValue *GV : ValuesToLink) {
-    MapValue(GV, ValueMap, RF_MoveDistinctMDs, &TypeMap, &ValMaterializer);
-    if (HasError)
-      return true;
+  processGlobalsForThinLTO();
+
+  for (unsigned I = 0; I < ValuesToLink.size(); ++I) {
+    GlobalValue *GV = ValuesToLink[I];
+    const Comdat *SC = GV->getComdat();
+    if (!SC)
+      continue;
+    for (GlobalValue *GV2 : ComdatMembers[SC])
+      ValuesToLink.insert(GV2);
   }
 
-  // Note that we are done linking global value bodies. This prevents
-  // metadata linking from creating new references.
-  DoneLinkingBodies = true;
-
-  // Remap all of the named MDNodes in Src into the DstM module. We do this
-  // after linking GlobalValues so that MDNodes that reference GlobalValues
-  // are properly remapped.
-  linkNamedMDNodes();
+  if (shouldInternalizeLinkedSymbols()) {
+    for (GlobalValue *GV : ValuesToLink)
+      Internalize.insert(GV->getName());
+  }
 
-  // Merge the module flags into the DstM module.
-  if (linkModuleFlagsMetadata())
+  if (Mover.move(SrcM,
+                 makeArrayRef(&*ValuesToLink.begin(), ValuesToLink.size()),
+                 [this](GlobalValue &GV, IRMover::ValueAdder Add) {
+                   addLazyFor(GV, Add);
+                 }))
     return true;
+  Module &DstM = Mover.getModule();
+  for (auto &P : Internalize) {
+    GlobalValue *GV = DstM.getNamedValue(P.first());
+    GV->setLinkage(GlobalValue::InternalLinkage);
+  }
 
   return false;
 }
 
-Linker::StructTypeKeyInfo::KeyTy::KeyTy(ArrayRef<Type *> E, bool P)
-    : ETypes(E), IsPacked(P) {}
-
-Linker::StructTypeKeyInfo::KeyTy::KeyTy(const StructType *ST)
-    : ETypes(ST->elements()), IsPacked(ST->isPacked()) {}
-
-bool Linker::StructTypeKeyInfo::KeyTy::operator==(const KeyTy &That) const {
-  if (IsPacked != That.IsPacked)
-    return false;
-  if (ETypes != That.ETypes)
-    return false;
-  return true;
-}
-
-bool Linker::StructTypeKeyInfo::KeyTy::operator!=(const KeyTy &That) const {
-  return !this->operator==(That);
-}
-
-StructType *Linker::StructTypeKeyInfo::getEmptyKey() {
-  return DenseMapInfo<StructType *>::getEmptyKey();
-}
-
-StructType *Linker::StructTypeKeyInfo::getTombstoneKey() {
-  return DenseMapInfo<StructType *>::getTombstoneKey();
-}
-
-unsigned Linker::StructTypeKeyInfo::getHashValue(const KeyTy &Key) {
-  return hash_combine(hash_combine_range(Key.ETypes.begin(), Key.ETypes.end()),
-                      Key.IsPacked);
-}
-
-unsigned Linker::StructTypeKeyInfo::getHashValue(const StructType *ST) {
-  return getHashValue(KeyTy(ST));
-}
-
-bool Linker::StructTypeKeyInfo::isEqual(const KeyTy &LHS,
-                                        const StructType *RHS) {
-  if (RHS == getEmptyKey() || RHS == getTombstoneKey())
-    return false;
-  return LHS == KeyTy(RHS);
-}
-
-bool Linker::StructTypeKeyInfo::isEqual(const StructType *LHS,
-                                        const StructType *RHS) {
-  if (RHS == getEmptyKey())
-    return LHS == getEmptyKey();
-
-  if (RHS == getTombstoneKey())
-    return LHS == getTombstoneKey();
-
-  return KeyTy(LHS) == KeyTy(RHS);
-}
-
-void Linker::IdentifiedStructTypeSet::addNonOpaque(StructType *Ty) {
-  assert(!Ty->isOpaque());
-  NonOpaqueStructTypes.insert(Ty);
-}
-
-void Linker::IdentifiedStructTypeSet::switchToNonOpaque(StructType *Ty) {
-  assert(!Ty->isOpaque());
-  NonOpaqueStructTypes.insert(Ty);
-  bool Removed = OpaqueStructTypes.erase(Ty);
-  (void)Removed;
-  assert(Removed);
-}
-
-void Linker::IdentifiedStructTypeSet::addOpaque(StructType *Ty) {
-  assert(Ty->isOpaque());
-  OpaqueStructTypes.insert(Ty);
-}
-
-StructType *
-Linker::IdentifiedStructTypeSet::findNonOpaque(ArrayRef<Type *> ETypes,
-                                               bool IsPacked) {
-  Linker::StructTypeKeyInfo::KeyTy Key(ETypes, IsPacked);
-  auto I = NonOpaqueStructTypes.find_as(Key);
-  if (I == NonOpaqueStructTypes.end())
-    return nullptr;
-  return *I;
-}
-
-bool Linker::IdentifiedStructTypeSet::hasType(StructType *Ty) {
-  if (Ty->isOpaque())
-    return OpaqueStructTypes.count(Ty);
-  auto I = NonOpaqueStructTypes.find(Ty);
-  if (I == NonOpaqueStructTypes.end())
-    return false;
-  return *I == Ty;
-}
-
 Linker::Linker(Module &M, DiagnosticHandlerFunction DiagnosticHandler)
-    : Composite(M), DiagnosticHandler(DiagnosticHandler) {
-  TypeFinder StructTypes;
-  StructTypes.run(M, true);
-  for (StructType *Ty : StructTypes) {
-    if (Ty->isOpaque())
-      IdentifiedStructTypes.addOpaque(Ty);
-    else
-      IdentifiedStructTypes.addNonOpaque(Ty);
-  }
-}
+    : Mover(M, DiagnosticHandler) {}
 
 bool Linker::linkInModule(Module &Src, unsigned Flags,
                           const FunctionInfoIndex *Index,
                           DenseSet<const GlobalValue *> *FunctionsToImport) {
-  ModuleLinker TheLinker(Composite, IdentifiedStructTypes, Src,
-                         DiagnosticHandler, Flags, Index, FunctionsToImport);
-  bool RetCode = TheLinker.run();
-  Composite.dropTriviallyDeadConstantArrays();
-  return RetCode;
+  ModuleLinker TheLinker(Mover, Src, Flags, Index, FunctionsToImport);
+  return TheLinker.run();
 }
 
 //===----------------------------------------------------------------------===//

Modified: llvm/trunk/test/Linker/alias.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Linker/alias.ll?rev=255254&r1=255253&r2=255254&view=diff
==============================================================================
--- llvm/trunk/test/Linker/alias.ll (original)
+++ llvm/trunk/test/Linker/alias.ll Thu Dec 10 08:19:35 2015
@@ -1,16 +1,37 @@
-; RUN: llvm-link %s %S/Inputs/alias.ll -S -o - | FileCheck %s
-; RUN: llvm-link %S/Inputs/alias.ll %s -S -o - | FileCheck %s
+; RUN: llvm-link %s %S/Inputs/alias.ll -S -o - | FileCheck --check-prefix=C1 %s
+; RUN: llvm-link %S/Inputs/alias.ll %s -S -o - | FileCheck --check-prefix=C2 %s
+
+; FIXME:
+; The C1 direction is incorrect.
+; When moving an alias to an existing module and we want to discard the aliasee
+; (the C2 case), the IRMover knows to copy the aliasee as internal.
+; When moving a replacement to an aliasee to a module that has an alias (C1),
+; a replace all uses with blindly changes the alias.
+; The C1 case doesn't happen when using a system linker with a plugin because
+; the linker does full symbol resolution first.
+; Given that this is a problem only with llvm-link and its 1 module at a time
+; linking, it should probably learn to changes the aliases in the destination
+; before using the IRMover.
 
 @foo = weak global i32 0
-; CHECK-DAG: @foo = alias i32, i32* @zed
+; C1-DAG: @foo = alias i32, i32* @zed
+; C2-DAG: @foo = alias i32, i32* @zed
 
 @bar = alias i32, i32* @foo
-; CHECK-DAG: @bar = alias i32, i32* @foo
+; C1-DAG: @bar = alias i32, i32* @foo
+
+; C2-DAG: @foo.1 = internal global i32 0
+; C2-DAG: @bar = alias i32, i32* @foo.1
 
 @foo2 = weak global i32 0
-; CHECK-DAG: @foo2 = alias i16, bitcast (i32* @zed to i16*)
+; C1-DAG: @foo2 = alias i16, bitcast (i32* @zed to i16*)
+; C2-DAG: @foo2 = alias i16, bitcast (i32* @zed to i16*)
 
 @bar2 = alias i32, i32* @foo2
-; CHECK-DAG: @bar2 = alias i32, bitcast (i16* @foo2 to i32*)
+; C1-DAG: @bar2 = alias i32, bitcast (i16* @foo2 to i32*)
+
+; C2-DAG: @foo2.2 = internal global i32 0
+; C2-DAG: @bar2 = alias i32, i32* @foo2.2
 
-; CHECK-DAG: @zed = global i32 42
+; C1-DAG: @zed = global i32 42
+; C2-DAG: @zed = global i32 42

Modified: llvm/trunk/test/tools/gold/X86/drop-linkage.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/tools/gold/X86/drop-linkage.ll?rev=255254&r1=255253&r2=255254&view=diff
==============================================================================
--- llvm/trunk/test/tools/gold/X86/drop-linkage.ll (original)
+++ llvm/trunk/test/tools/gold/X86/drop-linkage.ll Thu Dec 10 08:19:35 2015
@@ -11,4 +11,4 @@ define void @foo() {
   ret void
 }
 
-; CHECK: declare void @foo(){{$}}
+; CHECK: declare extern_weak void @foo(){{$}}

Modified: llvm/trunk/tools/gold/gold-plugin.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/gold/gold-plugin.cpp?rev=255254&r1=255253&r2=255254&view=diff
==============================================================================
--- llvm/trunk/tools/gold/gold-plugin.cpp (original)
+++ llvm/trunk/tools/gold/gold-plugin.cpp Thu Dec 10 08:19:35 2015
@@ -29,7 +29,7 @@
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Verifier.h"
-#include "llvm/Linker/Linker.h"
+#include "llvm/Linker/IRMover.h"
 #include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Object/FunctionIndexObjectFile.h"
 #include "llvm/Object/IRObjectFile.h"
@@ -62,6 +62,17 @@ struct claimed_file {
   void *handle;
   std::vector<ld_plugin_symbol> syms;
 };
+
+struct ResolutionInfo {
+  bool IsLinkonceOdr = true;
+  bool UnnamedAddr = true;
+  GlobalValue::VisibilityTypes Visibility = GlobalValue::DefaultVisibility;
+  bool CommonInternal = false;
+  bool UseCommon = false;
+  unsigned CommonSize = 0;
+  unsigned CommonAlign = 0;
+  claimed_file *CommonFile = nullptr;
+};
 }
 
 static ld_plugin_status discard_message(int level, const char *format, ...) {
@@ -81,6 +92,7 @@ static ld_plugin_message message = disca
 static Reloc::Model RelocationModel = Reloc::Default;
 static std::string output_name = "";
 static std::list<claimed_file> Modules;
+static StringMap<ResolutionInfo> ResInfo;
 static std::vector<std::string> Cleanup;
 static llvm::TargetOptions TargetOpts;
 
@@ -332,6 +344,18 @@ static void diagnosticHandlerForContext(
   diagnosticHandler(DI);
 }
 
+static GlobalValue::VisibilityTypes
+getMinVisibility(GlobalValue::VisibilityTypes A,
+                 GlobalValue::VisibilityTypes B) {
+  if (A == GlobalValue::HiddenVisibility)
+    return A;
+  if (B == GlobalValue::HiddenVisibility)
+    return B;
+  if (A == GlobalValue::ProtectedVisibility)
+    return A;
+  return B;
+}
+
 /// Called by gold to see whether this file is one that our plugin can handle.
 /// We'll try to open it and register all the symbols with add_symbol if
 /// possible.
@@ -411,8 +435,22 @@ static ld_plugin_status claim_file_hook(
 
     const GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl());
 
+    ResolutionInfo &Res = ResInfo[sym.name];
+
     sym.visibility = LDPV_DEFAULT;
     if (GV) {
+      Res.UnnamedAddr &= GV->hasUnnamedAddr();
+      Res.IsLinkonceOdr &= GV->hasLinkOnceLinkage();
+      if (GV->hasCommonLinkage()) {
+        Res.CommonAlign = std::max(Res.CommonAlign, GV->getAlignment());
+        const DataLayout &DL = GV->getParent()->getDataLayout();
+        uint64_t Size = DL.getTypeAllocSize(GV->getType()->getElementType());
+        if (Size >= Res.CommonSize) {
+          Res.CommonSize = Size;
+          Res.CommonFile = &cf;
+        }
+      }
+      Res.Visibility = getMinVisibility(Res.Visibility, GV->getVisibility());
       switch (GV->getVisibility()) {
       case GlobalValue::DefaultVisibility:
         sym.visibility = LDPV_DEFAULT;
@@ -466,27 +504,6 @@ static ld_plugin_status claim_file_hook(
   return LDPS_OK;
 }
 
-static void keepGlobalValue(GlobalValue &GV,
-                            std::vector<GlobalAlias *> &KeptAliases) {
-  assert(!GV.hasLocalLinkage());
-
-  if (auto *GA = dyn_cast<GlobalAlias>(&GV))
-    KeptAliases.push_back(GA);
-
-  switch (GV.getLinkage()) {
-  default:
-    break;
-  case GlobalValue::LinkOnceAnyLinkage:
-    GV.setLinkage(GlobalValue::WeakAnyLinkage);
-    break;
-  case GlobalValue::LinkOnceODRLinkage:
-    GV.setLinkage(GlobalValue::WeakODRLinkage);
-    break;
-  }
-
-  assert(!GV.isDiscardableIfUnused());
-}
-
 static void internalize(GlobalValue &GV) {
   if (GV.isDeclarationForLinker())
     return; // We get here if there is a matching asm definition.
@@ -494,33 +511,6 @@ static void internalize(GlobalValue &GV)
     GV.setLinkage(GlobalValue::InternalLinkage);
 }
 
-static void drop(GlobalValue &GV) {
-  if (auto *F = dyn_cast<Function>(&GV)) {
-    F->deleteBody();
-    F->setComdat(nullptr); // Should deleteBody do this?
-    return;
-  }
-
-  if (auto *Var = dyn_cast<GlobalVariable>(&GV)) {
-    Var->setInitializer(nullptr);
-    Var->setLinkage(
-        GlobalValue::ExternalLinkage); // Should setInitializer do this?
-    Var->setComdat(nullptr); // and this?
-    return;
-  }
-
-  auto &Alias = cast<GlobalAlias>(GV);
-  Module &M = *Alias.getParent();
-  PointerType &Ty = *cast<PointerType>(Alias.getType());
-  GlobalValue::LinkageTypes L = Alias.getLinkage();
-  auto *Var =
-      new GlobalVariable(M, Ty.getElementType(), /*isConstant*/ false, L,
-                         /*Initializer*/ nullptr);
-  Var->takeName(&Alias);
-  Alias.replaceAllUsesWith(Var);
-  Alias.eraseFromParent();
-}
-
 static const char *getResolutionName(ld_plugin_symbol_resolution R) {
   switch (R) {
   case LDPR_UNKNOWN:
@@ -547,58 +537,6 @@ static const char *getResolutionName(ld_
   llvm_unreachable("Unknown resolution");
 }
 
-namespace {
-class LocalValueMaterializer final : public ValueMaterializer {
-  DenseSet<GlobalValue *> &Dropped;
-  DenseMap<GlobalObject *, GlobalObject *> LocalVersions;
-
-public:
-  LocalValueMaterializer(DenseSet<GlobalValue *> &Dropped) : Dropped(Dropped) {}
-  Value *materializeDeclFor(Value *V) override;
-};
-}
-
-Value *LocalValueMaterializer::materializeDeclFor(Value *V) {
-  auto *GO = dyn_cast<GlobalObject>(V);
-  if (!GO)
-    return nullptr;
-
-  auto I = LocalVersions.find(GO);
-  if (I != LocalVersions.end())
-    return I->second;
-
-  if (!Dropped.count(GO))
-    return nullptr;
-
-  Module &M = *GO->getParent();
-  GlobalValue::LinkageTypes L = GO->getLinkage();
-  GlobalObject *Declaration;
-  if (auto *F = dyn_cast<Function>(GO)) {
-    Declaration = Function::Create(F->getFunctionType(), L, "", &M);
-  } else {
-    auto *Var = cast<GlobalVariable>(GO);
-    Declaration = new GlobalVariable(M, Var->getType()->getElementType(),
-                                     Var->isConstant(), L,
-                                     /*Initializer*/ nullptr);
-  }
-  Declaration->takeName(GO);
-  Declaration->copyAttributesFrom(GO);
-
-  GO->setLinkage(GlobalValue::InternalLinkage);
-  GO->setName(Declaration->getName());
-  Dropped.erase(GO);
-  GO->replaceAllUsesWith(Declaration);
-
-  LocalVersions[Declaration] = GO;
-
-  return GO;
-}
-
-static Constant *mapConstantToLocalCopy(Constant *C, ValueToValueMapTy &VM,
-                                        LocalValueMaterializer *Materializer) {
-  return MapValue(C, VM, RF_IgnoreMissingEntries, nullptr, Materializer);
-}
-
 static void freeSymName(ld_plugin_symbol &Sym) {
   free(Sym.name);
   free(Sym.comdat_key);
@@ -640,7 +578,8 @@ getFunctionIndexForFile(claimed_file &F,
 static std::unique_ptr<Module>
 getModuleForFile(LLVMContext &Context, claimed_file &F,
                  ld_plugin_input_file &Info, raw_fd_ostream *ApiFile,
-                 StringSet<> &Internalize, StringSet<> &Maybe) {
+                 StringSet<> &Internalize, StringSet<> &Maybe,
+                 std::vector<GlobalValue *> &Keep) {
 
   if (get_symbols(F.handle, F.syms.size(), F.syms.data()) != LDPS_OK)
     message(LDPL_FATAL, "Failed to get symbol information");
@@ -668,11 +607,12 @@ getModuleForFile(LLVMContext &Context, c
   SmallPtrSet<GlobalValue *, 8> Used;
   collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
 
-  DenseSet<GlobalValue *> Drop;
-  std::vector<GlobalAlias *> KeptAliases;
-
   unsigned SymNum = 0;
   for (auto &ObjSym : Obj.symbols()) {
+    GlobalValue *GV = Obj.getSymbolGV(ObjSym.getRawDataRefImpl());
+    if (GV && GV->hasAppendingLinkage())
+      Keep.push_back(GV);
+
     if (shouldSkip(ObjSym.getFlags()))
       continue;
     ld_plugin_symbol &Sym = F.syms[SymNum];
@@ -684,20 +624,37 @@ getModuleForFile(LLVMContext &Context, c
     if (options::generate_api_file)
       *ApiFile << Sym.name << ' ' << getResolutionName(Resolution) << '\n';
 
-    GlobalValue *GV = Obj.getSymbolGV(ObjSym.getRawDataRefImpl());
     if (!GV) {
       freeSymName(Sym);
       continue; // Asm symbol.
     }
 
-    if (Resolution != LDPR_PREVAILING_DEF_IRONLY && GV->hasCommonLinkage()) {
-      // Common linkage is special. There is no single symbol that wins the
-      // resolution. Instead we have to collect the maximum alignment and size.
-      // The IR linker does that for us if we just pass it every common GV.
-      // We still have to keep track of LDPR_PREVAILING_DEF_IRONLY so we
-      // internalize once the IR linker has done its job.
-      freeSymName(Sym);
-      continue;
+    ResolutionInfo &Res = ResInfo[Sym.name];
+    if (Resolution == LDPR_PREVAILING_DEF_IRONLY_EXP && !Res.IsLinkonceOdr)
+      Resolution = LDPR_PREVAILING_DEF;
+
+    GV->setUnnamedAddr(Res.UnnamedAddr);
+    GV->setVisibility(Res.Visibility);
+
+    // Override gold's resolution for common symbols. We want the largest
+    // one to win.
+    if (GV->hasCommonLinkage()) {
+      cast<GlobalVariable>(GV)->setAlignment(Res.CommonAlign);
+      if (Resolution == LDPR_PREVAILING_DEF_IRONLY)
+        Res.CommonInternal = true;
+
+      if (Resolution == LDPR_PREVAILING_DEF_IRONLY ||
+          Resolution == LDPR_PREVAILING_DEF)
+        Res.UseCommon = true;
+
+      if (Res.CommonFile == &F && Res.UseCommon) {
+        if (Res.CommonInternal)
+          Resolution = LDPR_PREVAILING_DEF_IRONLY;
+        else
+          Resolution = LDPR_PREVAILING_DEF;
+      } else {
+        Resolution = LDPR_PREEMPTED_IR;
+      }
     }
 
     switch (Resolution) {
@@ -707,40 +664,37 @@ getModuleForFile(LLVMContext &Context, c
     case LDPR_RESOLVED_IR:
     case LDPR_RESOLVED_EXEC:
     case LDPR_RESOLVED_DYN:
-      assert(GV->isDeclarationForLinker());
+    case LDPR_PREEMPTED_IR:
+    case LDPR_PREEMPTED_REG:
       break;
 
     case LDPR_UNDEF:
-      if (!GV->isDeclarationForLinker()) {
+      if (!GV->isDeclarationForLinker())
         assert(GV->hasComdat());
-        Drop.insert(GV);
-      }
       break;
 
     case LDPR_PREVAILING_DEF_IRONLY: {
-      keepGlobalValue(*GV, KeptAliases);
-      if (!Used.count(GV)) {
-        // Since we use the regular lib/Linker, we cannot just internalize GV
-        // now or it will not be copied to the merged module. Instead we force
-        // it to be copied and then internalize it.
+      Keep.push_back(GV);
+      // The IR linker has to be able to map this value to a declaration,
+      // so we can only internalize after linking.
+      if (!Used.count(GV))
         Internalize.insert(GV->getName());
-      }
       break;
     }
 
     case LDPR_PREVAILING_DEF:
-      keepGlobalValue(*GV, KeptAliases);
-      break;
-
-    case LDPR_PREEMPTED_IR:
-      // Gold might have selected a linkonce_odr and preempted a weak_odr.
-      // In that case we have to make sure we don't end up internalizing it.
-      if (!GV->isDiscardableIfUnused())
-        Maybe.erase(GV->getName());
-
-      // fall-through
-    case LDPR_PREEMPTED_REG:
-      Drop.insert(GV);
+      Keep.push_back(GV);
+      // There is a non IR use, so we have to force optimizations to keep this.
+      switch (GV->getLinkage()) {
+      default:
+        break;
+      case GlobalValue::LinkOnceAnyLinkage:
+        GV->setLinkage(GlobalValue::WeakAnyLinkage);
+        break;
+      case GlobalValue::LinkOnceODRLinkage:
+        GV->setLinkage(GlobalValue::WeakODRLinkage);
+        break;
+      }
       break;
 
     case LDPR_PREVAILING_DEF_IRONLY_EXP: {
@@ -748,9 +702,8 @@ getModuleForFile(LLVMContext &Context, c
       // reason is that this GV might have a copy in another module
       // and in that module the address might be significant, but that
       // copy will be LDPR_PREEMPTED_IR.
-      if (GV->hasLinkOnceODRLinkage())
-        Maybe.insert(GV->getName());
-      keepGlobalValue(*GV, KeptAliases);
+      Maybe.insert(GV->getName());
+      Keep.push_back(GV);
       break;
     }
     }
@@ -758,19 +711,6 @@ getModuleForFile(LLVMContext &Context, c
     freeSymName(Sym);
   }
 
-  ValueToValueMapTy VM;
-  LocalValueMaterializer Materializer(Drop);
-  for (GlobalAlias *GA : KeptAliases) {
-    // Gold told us to keep GA. It is possible that a GV usied in the aliasee
-    // expression is being dropped. If that is the case, that GV must be copied.
-    Constant *Aliasee = GA->getAliasee();
-    Constant *Replacement = mapConstantToLocalCopy(Aliasee, VM, &Materializer);
-    GA->setAliasee(Replacement);
-  }
-
-  for (auto *GV : Drop)
-    drop(*GV);
-
   return Obj.takeModule();
 }
 
@@ -941,7 +881,7 @@ static ld_plugin_status allSymbolsReadHo
   Context.setDiagnosticHandler(diagnosticHandlerForContext, nullptr, true);
 
   std::unique_ptr<Module> Combined(new Module("ld-temp.o", Context));
-  Linker L(*Combined, diagnosticHandler);
+  IRMover L(*Combined, diagnosticHandler);
 
   std::string DefaultTriple = sys::getDefaultTargetTriple();
 
@@ -951,15 +891,15 @@ static ld_plugin_status allSymbolsReadHo
     ld_plugin_input_file File;
     if (get_input_file(F.handle, &File) != LDPS_OK)
       message(LDPL_FATAL, "Failed to get file information");
+    std::vector<GlobalValue *> Keep;
     std::unique_ptr<Module> M =
-        getModuleForFile(Context, F, File, ApiFile, Internalize, Maybe);
+        getModuleForFile(Context, F, File, ApiFile, Internalize, Maybe, Keep);
     if (!options::triple.empty())
       M->setTargetTriple(options::triple.c_str());
-    else if (M->getTargetTriple().empty()) {
+    else if (M->getTargetTriple().empty())
       M->setTargetTriple(DefaultTriple);
-    }
 
-    if (L.linkInModule(*M))
+    if (L.move(*M, Keep, [](GlobalValue &, IRMover::ValueAdder) {}))
       message(LDPL_FATAL, "Failed to link module");
     if (release_input_file(F.handle) != LDPS_OK)
       message(LDPL_FATAL, "Failed to release file information");




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