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