This file originated in lib/VMCore/Linker.cpp but now lives in

lib/Linker/LinkModules.cpp

llvm-svn: 17694

1 files changed, 956 insertions, 0 deletions

diff --git a/llvm/lib/Linker/LinkModules.cpp b/llvm/lib/Linker/LinkModules.cpp
new file mode 100644
index 00000000000..6d732f11b8e
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+++ b/llvm/lib/Linker/LinkModules.cpp
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+//===- lib/Linker/LinkModules.cpp - Module Linker Implementation ----------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This file implements the LLVM module linker.
+//
+// Specifically, this:
+//  * Merges global variables between the two modules
+//    * Uninit + Uninit = Init, Init + Uninit = Init, Init + Init = Error if !=
+//  * Merges functions between two modules
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Linker.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Module.h"
+#include "llvm/SymbolTable.h"
+#include "llvm/Instructions.h"
+#include "llvm/Assembly/Writer.h"
+#include "llvm/System/Path.h"
+#include <iostream>
+#include <sstream>
+using namespace llvm;
+
+// Error - Simple wrapper function to conditionally assign to E and return true.
+// This just makes error return conditions a little bit simpler...
+//
+static inline bool Error(std::string *E, const std::string &Message) {
+  if (E) *E = Message;
+  return true;
+}
+
+static std::string ToStr(const Type *Ty, const Module *M) {
+  std::ostringstream OS;
+  WriteTypeSymbolic(OS, Ty, M);
+  return OS.str();
+}
+
+//
+// Function: ResolveTypes()
+//
+// Description:
+//  Attempt to link the two specified types together.
+//
+// Inputs:
+//  DestTy - The type to which we wish to resolve.
+//  SrcTy  - The original type which we want to resolve.
+//  Name   - The name of the type.
+//
+// Outputs:
+//  DestST - The symbol table in which the new type should be placed.
+//
+// Return value:
+//  true  - There is an error and the types cannot yet be linked.
+//  false - No errors.
+//
+static bool ResolveTypes(const Type *DestTy, const Type *SrcTy,
+                         SymbolTable *DestST, const std::string &Name) {
+  if (DestTy == SrcTy) return false;       // If already equal, noop
+
+  // Does the type already exist in the module?
+  if (DestTy && !isa<OpaqueType>(DestTy)) {  // Yup, the type already exists...
+    if (const OpaqueType *OT = dyn_cast<OpaqueType>(SrcTy)) {
+      const_cast<OpaqueType*>(OT)->refineAbstractTypeTo(DestTy);
+    } else {
+      return true;  // Cannot link types... neither is opaque and not-equal
+    }
+  } else {                       // Type not in dest module.  Add it now.
+    if (DestTy)                  // Type _is_ in module, just opaque...
+      const_cast<OpaqueType*>(cast<OpaqueType>(DestTy))
+                           ->refineAbstractTypeTo(SrcTy);
+    else if (!Name.empty())
+      DestST->insert(Name, const_cast<Type*>(SrcTy));
+  }
+  return false;
+}
+
+static const FunctionType *getFT(const PATypeHolder &TH) {
+  return cast<FunctionType>(TH.get());
+}
+static const StructType *getST(const PATypeHolder &TH) {
+  return cast<StructType>(TH.get());
+}
+
+// RecursiveResolveTypes - This is just like ResolveTypes, except that it
+// recurses down into derived types, merging the used types if the parent types
+// are compatible.
+//
+static bool RecursiveResolveTypesI(const PATypeHolder &DestTy,
+                                   const PATypeHolder &SrcTy,
+                                   SymbolTable *DestST, const std::string &Name,
+                std::vector<std::pair<PATypeHolder, PATypeHolder> > &Pointers) {
+  const Type *SrcTyT = SrcTy.get();
+  const Type *DestTyT = DestTy.get();
+  if (DestTyT == SrcTyT) return false;       // If already equal, noop
+  
+  // If we found our opaque type, resolve it now!
+  if (isa<OpaqueType>(DestTyT) || isa<OpaqueType>(SrcTyT))
+    return ResolveTypes(DestTyT, SrcTyT, DestST, Name);
+  
+  // Two types cannot be resolved together if they are of different primitive
+  // type.  For example, we cannot resolve an int to a float.
+  if (DestTyT->getTypeID() != SrcTyT->getTypeID()) return true;
+
+  // Otherwise, resolve the used type used by this derived type...
+  switch (DestTyT->getTypeID()) {
+  case Type::FunctionTyID: {
+    if (cast<FunctionType>(DestTyT)->isVarArg() !=
+        cast<FunctionType>(SrcTyT)->isVarArg() ||
+        cast<FunctionType>(DestTyT)->getNumContainedTypes() !=
+        cast<FunctionType>(SrcTyT)->getNumContainedTypes())
+      return true;
+    for (unsigned i = 0, e = getFT(DestTy)->getNumContainedTypes(); i != e; ++i)
+      if (RecursiveResolveTypesI(getFT(DestTy)->getContainedType(i),
+                                 getFT(SrcTy)->getContainedType(i), DestST, "",
+                                 Pointers))
+        return true;
+    return false;
+  }
+  case Type::StructTyID: {
+    if (getST(DestTy)->getNumContainedTypes() != 
+        getST(SrcTy)->getNumContainedTypes()) return 1;
+    for (unsigned i = 0, e = getST(DestTy)->getNumContainedTypes(); i != e; ++i)
+      if (RecursiveResolveTypesI(getST(DestTy)->getContainedType(i),
+                                 getST(SrcTy)->getContainedType(i), DestST, "",
+                                 Pointers))
+        return true;
+    return false;
+  }
+  case Type::ArrayTyID: {
+    const ArrayType *DAT = cast<ArrayType>(DestTy.get());
+    const ArrayType *SAT = cast<ArrayType>(SrcTy.get());
+    if (DAT->getNumElements() != SAT->getNumElements()) return true;
+    return RecursiveResolveTypesI(DAT->getElementType(), SAT->getElementType(),
+                                  DestST, "", Pointers);
+  }
+  case Type::PointerTyID: {
+    // If this is a pointer type, check to see if we have already seen it.  If
+    // so, we are in a recursive branch.  Cut off the search now.  We cannot use
+    // an associative container for this search, because the type pointers (keys
+    // in the container) change whenever types get resolved...
+    //
+    for (unsigned i = 0, e = Pointers.size(); i != e; ++i)
+      if (Pointers[i].first == DestTy)
+        return Pointers[i].second != SrcTy;
+
+    // Otherwise, add the current pointers to the vector to stop recursion on
+    // this pair.
+    Pointers.push_back(std::make_pair(DestTyT, SrcTyT));
+    bool Result =
+      RecursiveResolveTypesI(cast<PointerType>(DestTy.get())->getElementType(),
+                             cast<PointerType>(SrcTy.get())->getElementType(),
+                             DestST, "", Pointers);
+    Pointers.pop_back();
+    return Result;
+  }
+  default: assert(0 && "Unexpected type!"); return true;
+  }  
+}
+
+static bool RecursiveResolveTypes(const PATypeHolder &DestTy,
+                                  const PATypeHolder &SrcTy,
+                                  SymbolTable *DestST, const std::string &Name){
+  std::vector<std::pair<PATypeHolder, PATypeHolder> > PointerTypes;
+  return RecursiveResolveTypesI(DestTy, SrcTy, DestST, Name, PointerTypes);
+}
+
+
+// LinkTypes - Go through the symbol table of the Src module and see if any
+// types are named in the src module that are not named in the Dst module.
+// Make sure there are no type name conflicts.
+//
+static bool LinkTypes(Module *Dest, const Module *Src, std::string *Err) {
+  SymbolTable       *DestST = &Dest->getSymbolTable();
+  const SymbolTable *SrcST  = &Src->getSymbolTable();
+
+  // Look for a type plane for Type's...
+  SymbolTable::type_const_iterator TI = SrcST->type_begin();
+  SymbolTable::type_const_iterator TE = SrcST->type_end();
+  if (TI == TE) return false;  // No named types, do nothing.
+
+  // Some types cannot be resolved immediately because they depend on other
+  // types being resolved to each other first.  This contains a list of types we
+  // are waiting to recheck.
+  std::vector<std::string> DelayedTypesToResolve;
+
+  for ( ; TI != TE; ++TI ) {
+    const std::string &Name = TI->first;
+    const Type *RHS = TI->second;
+
+    // Check to see if this type name is already in the dest module...
+    Type *Entry = DestST->lookupType(Name);
+
+    if (ResolveTypes(Entry, RHS, DestST, Name)) {
+      // They look different, save the types 'till later to resolve.
+      DelayedTypesToResolve.push_back(Name);
+    }
+  }
+
+  // Iteratively resolve types while we can...
+  while (!DelayedTypesToResolve.empty()) {
+    // Loop over all of the types, attempting to resolve them if possible...
+    unsigned OldSize = DelayedTypesToResolve.size();
+
+    // Try direct resolution by name...
+    for (unsigned i = 0; i != DelayedTypesToResolve.size(); ++i) {
+      const std::string &Name = DelayedTypesToResolve[i];
+      Type *T1 = SrcST->lookupType(Name);
+      Type *T2 = DestST->lookupType(Name);
+      if (!ResolveTypes(T2, T1, DestST, Name)) {
+        // We are making progress!
+        DelayedTypesToResolve.erase(DelayedTypesToResolve.begin()+i);
+        --i;
+      }
+    }
+
+    // Did we not eliminate any types?
+    if (DelayedTypesToResolve.size() == OldSize) {
+      // Attempt to resolve subelements of types.  This allows us to merge these
+      // two types: { int* } and { opaque* }
+      for (unsigned i = 0, e = DelayedTypesToResolve.size(); i != e; ++i) {
+        const std::string &Name = DelayedTypesToResolve[i];
+        PATypeHolder T1(SrcST->lookupType(Name));
+        PATypeHolder T2(DestST->lookupType(Name));
+
+        if (!RecursiveResolveTypes(T2, T1, DestST, Name)) {
+          // We are making progress!
+          DelayedTypesToResolve.erase(DelayedTypesToResolve.begin()+i);
+          
+          // Go back to the main loop, perhaps we can resolve directly by name
+          // now...
+          break;
+        }
+      }
+
+      // If we STILL cannot resolve the types, then there is something wrong.
+      // Report the warning and delete one of the names.
+      if (DelayedTypesToResolve.size() == OldSize) {
+        const std::string &Name = DelayedTypesToResolve.back();
+        
+        const Type *T1 = SrcST->lookupType(Name);
+        const Type *T2 = DestST->lookupType(Name);
+        std::cerr << "WARNING: Type conflict between types named '" << Name
+                  <<  "'.\n    Src='";
+        WriteTypeSymbolic(std::cerr, T1, Src);
+        std::cerr << "'.\n   Dest='";
+        WriteTypeSymbolic(std::cerr, T2, Dest);
+        std::cerr << "'\n";
+
+        // Remove the symbol name from the destination.
+        DelayedTypesToResolve.pop_back();
+      }
+    }
+  }
+
+
+  return false;
+}
+
+static void PrintMap(const std::map<const Value*, Value*> &M) {
+  for (std::map<const Value*, Value*>::const_iterator I = M.begin(), E =M.end();
+       I != E; ++I) {
+    std::cerr << " Fr: " << (void*)I->first << " ";
+    I->first->dump();
+    std::cerr << " To: " << (void*)I->second << " ";
+    I->second->dump();
+    std::cerr << "\n";
+  }
+}
+
+
+// RemapOperand - Use LocalMap and GlobalMap to convert references from one
+// module to another.  This is somewhat sophisticated in that it can
+// automatically handle constant references correctly as well...
+//
+static Value *RemapOperand(const Value *In,
+                           std::map<const Value*, Value*> &LocalMap,
+                           std::map<const Value*, Value*> *GlobalMap) {
+  std::map<const Value*,Value*>::const_iterator I = LocalMap.find(In);
+  if (I != LocalMap.end()) return I->second;
+
+  if (GlobalMap) {
+    I = GlobalMap->find(In);
+    if (I != GlobalMap->end()) return I->second;
+  }
+
+  // Check to see if it's a constant that we are interesting in transforming...
+  if (const Constant *CPV = dyn_cast<Constant>(In)) {
+    if ((!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV)) ||
+        isa<ConstantAggregateZero>(CPV))
+      return const_cast<Constant*>(CPV);   // Simple constants stay identical...
+
+    Constant *Result = 0;
+
+    if (const ConstantArray *CPA = dyn_cast<ConstantArray>(CPV)) {
+      std::vector<Constant*> Operands(CPA->getNumOperands());
+      for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
+        Operands[i] =
+          cast<Constant>(RemapOperand(CPA->getOperand(i), LocalMap, GlobalMap));
+      Result = ConstantArray::get(cast<ArrayType>(CPA->getType()), Operands);
+    } else if (const ConstantStruct *CPS = dyn_cast<ConstantStruct>(CPV)) {
+      std::vector<Constant*> Operands(CPS->getNumOperands());
+      for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i)
+        Operands[i] =
+          cast<Constant>(RemapOperand(CPS->getOperand(i), LocalMap, GlobalMap));
+      Result = ConstantStruct::get(cast<StructType>(CPS->getType()), Operands);
+    } else if (isa<ConstantPointerNull>(CPV) || isa<UndefValue>(CPV)) {
+      Result = const_cast<Constant*>(CPV);
+    } else if (isa<GlobalValue>(CPV)) {
+      Result = cast<Constant>(RemapOperand(CPV, LocalMap, GlobalMap));
+    } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CPV)) {
+      if (CE->getOpcode() == Instruction::GetElementPtr) {
+        Value *Ptr = RemapOperand(CE->getOperand(0), LocalMap, GlobalMap);
+        std::vector<Constant*> Indices;
+        Indices.reserve(CE->getNumOperands()-1);
+        for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
+          Indices.push_back(cast<Constant>(RemapOperand(CE->getOperand(i),
+                                                        LocalMap, GlobalMap)));
+
+        Result = ConstantExpr::getGetElementPtr(cast<Constant>(Ptr), Indices);
+      } else if (CE->getNumOperands() == 1) {
+        // Cast instruction
+        assert(CE->getOpcode() == Instruction::Cast);
+        Value *V = RemapOperand(CE->getOperand(0), LocalMap, GlobalMap);
+        Result = ConstantExpr::getCast(cast<Constant>(V), CE->getType());
+      } else if (CE->getNumOperands() == 3) {
+        // Select instruction
+        assert(CE->getOpcode() == Instruction::Select);
+        Value *V1 = RemapOperand(CE->getOperand(0), LocalMap, GlobalMap);
+        Value *V2 = RemapOperand(CE->getOperand(1), LocalMap, GlobalMap);
+        Value *V3 = RemapOperand(CE->getOperand(2), LocalMap, GlobalMap);
+        Result = ConstantExpr::getSelect(cast<Constant>(V1), cast<Constant>(V2),
+                                         cast<Constant>(V3));
+      } else if (CE->getNumOperands() == 2) {
+        // Binary operator...
+        Value *V1 = RemapOperand(CE->getOperand(0), LocalMap, GlobalMap);
+        Value *V2 = RemapOperand(CE->getOperand(1), LocalMap, GlobalMap);
+
+        Result = ConstantExpr::get(CE->getOpcode(), cast<Constant>(V1),
+                                   cast<Constant>(V2));
+      } else {
+        assert(0 && "Unknown constant expr type!");
+      }
+
+    } else {
+      assert(0 && "Unknown type of derived type constant value!");
+    }
+
+    // Cache the mapping in our local map structure...
+    if (GlobalMap)
+      GlobalMap->insert(std::make_pair(In, Result));
+    else
+      LocalMap.insert(std::make_pair(In, Result));
+    return Result;
+  }
+
+  std::cerr << "XXX LocalMap: \n";
+  PrintMap(LocalMap);
+
+  if (GlobalMap) {
+    std::cerr << "XXX GlobalMap: \n";
+    PrintMap(*GlobalMap);
+  }
+
+  std::cerr << "Couldn't remap value: " << (void*)In << " " << *In << "\n";
+  assert(0 && "Couldn't remap value!");
+  return 0;
+}
+
+/// ForceRenaming - The LLVM SymbolTable class autorenames globals that conflict
+/// in the symbol table.  This is good for all clients except for us.  Go
+/// through the trouble to force this back.
+static void ForceRenaming(GlobalValue *GV, const std::string &Name) {
+  assert(GV->getName() != Name && "Can't force rename to self");
+  SymbolTable &ST = GV->getParent()->getSymbolTable();
+
+  // If there is a conflict, rename the conflict.
+  Value *ConflictVal = ST.lookup(GV->getType(), Name);
+  assert(ConflictVal&&"Why do we have to force rename if there is no conflic?");
+  GlobalValue *ConflictGV = cast<GlobalValue>(ConflictVal);
+  assert(ConflictGV->hasInternalLinkage() &&
+         "Not conflicting with a static global, should link instead!");
+
+  ConflictGV->setName("");          // Eliminate the conflict
+  GV->setName(Name);                // Force the name back
+  ConflictGV->setName(Name);        // This will cause ConflictGV to get renamed
+  assert(GV->getName() == Name && ConflictGV->getName() != Name &&
+         "ForceRenaming didn't work");
+}
+
+
+// LinkGlobals - Loop through the global variables in the src module and merge
+// them into the dest module.
+//
+static bool LinkGlobals(Module *Dest, const Module *Src,
+                        std::map<const Value*, Value*> &ValueMap,
+                    std::multimap<std::string, GlobalVariable *> &AppendingVars,
+                        std::map<std::string, GlobalValue*> &GlobalsByName,
+                        std::string *Err) {
+  // We will need a module level symbol table if the src module has a module
+  // level symbol table...
+  SymbolTable *ST = (SymbolTable*)&Dest->getSymbolTable();
+  
+  // Loop over all of the globals in the src module, mapping them over as we go
+  //
+  for (Module::const_giterator I = Src->gbegin(), E = Src->gend(); I != E; ++I){
+    const GlobalVariable *SGV = I;
+    GlobalVariable *DGV = 0;
+    // Check to see if may have to link the global.
+    if (SGV->hasName() && !SGV->hasInternalLinkage())
+      if (!(DGV = Dest->getGlobalVariable(SGV->getName(),
+                                          SGV->getType()->getElementType()))) {
+        std::map<std::string, GlobalValue*>::iterator EGV =
+          GlobalsByName.find(SGV->getName());
+        if (EGV != GlobalsByName.end())
+          DGV = dyn_cast<GlobalVariable>(EGV->second);
+        if (DGV && RecursiveResolveTypes(SGV->getType(), DGV->getType(), ST, ""))
+          DGV = 0;  // FIXME: gross.
+      }
+
+    assert(SGV->hasInitializer() || SGV->hasExternalLinkage() &&
+           "Global must either be external or have an initializer!");
+
+    bool SGExtern = SGV->isExternal();
+    bool DGExtern = DGV ? DGV->isExternal() : false;
+
+    if (!DGV || DGV->hasInternalLinkage() || SGV->hasInternalLinkage()) {
+      // No linking to be performed, 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(SGV->getType()->getElementType(),
+                           SGV->isConstant(), SGV->getLinkage(), /*init*/0,
+                           SGV->getName(), Dest);
+
+      // If the LLVM runtime renamed the global, but it is an externally visible
+      // symbol, DGV must be an existing global with internal linkage.  Rename
+      // it.
+      if (NewDGV->getName() != SGV->getName() && !NewDGV->hasInternalLinkage())
+        ForceRenaming(NewDGV, SGV->getName());
+
+      // Make sure to remember this mapping...
+      ValueMap.insert(std::make_pair(SGV, NewDGV));
+      if (SGV->hasAppendingLinkage())
+        // Keep track that this is an appending variable...
+        AppendingVars.insert(std::make_pair(SGV->getName(), NewDGV));
+
+    } else if (SGV->isExternal()) {
+      // If SGV is external or if both SGV & DGV are external..  Just link the
+      // external globals, we aren't adding anything.
+      ValueMap.insert(std::make_pair(SGV, DGV));
+
+      // Inherit 'const' information.
+      if (SGV->isConstant()) DGV->setConstant(true);
+
+    } else if (DGV->isExternal()) {   // If DGV is external but SGV is not...
+      ValueMap.insert(std::make_pair(SGV, DGV));
+      DGV->setLinkage(SGV->getLinkage());    // Inherit linkage!
+
+      if (DGV->isConstant() && !SGV->isConstant())
+        return Error(Err, "Linking globals named '" + SGV->getName() +
+                     "': declaration is const but definition is not!");
+
+      // Inherit 'const' information.
+      if (SGV->isConstant()) DGV->setConstant(true);
+
+    } else if (SGV->hasWeakLinkage() || SGV->hasLinkOnceLinkage()) {
+      // At this point we know that DGV has LinkOnce, Appending, Weak, or
+      // External linkage.  If DGV is Appending, this is an error.
+      if (DGV->hasAppendingLinkage())
+        return Error(Err, "Linking globals named '" + SGV->getName() +
+                     "' with 'weak' and 'appending' linkage is not allowed!");
+
+      if (SGV->isConstant() != DGV->isConstant())
+        return Error(Err, "Global Variable Collision on '" + 
+                     ToStr(SGV->getType(), Src) + " %" + SGV->getName() +
+                     "' - Global variables differ in const'ness");
+
+      // Otherwise, just perform the link.
+      ValueMap.insert(std::make_pair(SGV, DGV));
+
+      // Linkonce+Weak = Weak
+      if (DGV->hasLinkOnceLinkage() && SGV->hasWeakLinkage())
+        DGV->setLinkage(SGV->getLinkage());
+
+    } else if (DGV->hasWeakLinkage() || DGV->hasLinkOnceLinkage()) {
+      // At this point we know that SGV has LinkOnce, Appending, or External
+      // linkage.  If SGV is Appending, this is an error.
+      if (SGV->hasAppendingLinkage())
+        return Error(Err, "Linking globals named '" + SGV->getName() +
+                     " ' with 'weak' and 'appending' linkage is not allowed!");
+
+      if (SGV->isConstant() != DGV->isConstant())
+        return Error(Err, "Global Variable Collision on '" + 
+                     ToStr(SGV->getType(), Src) + " %" + SGV->getName() +
+                     "' - Global variables differ in const'ness");
+
+      if (!SGV->hasLinkOnceLinkage())
+        DGV->setLinkage(SGV->getLinkage());    // Inherit linkage!
+      ValueMap.insert(std::make_pair(SGV, DGV));
+  
+    } else if (SGV->getLinkage() != DGV->getLinkage()) {
+      return Error(Err, "Global variables named '" + SGV->getName() +
+                   "' have different linkage specifiers!");
+      // Inherit 'const' information.
+      if (SGV->isConstant()) DGV->setConstant(true);
+
+    } else if (SGV->hasExternalLinkage()) {
+      // Allow linking two exactly identical external global variables...
+      if (SGV->isConstant() != DGV->isConstant())
+        return Error(Err, "Global Variable Collision on '" + 
+                     ToStr(SGV->getType(), Src) + " %" + SGV->getName() +
+                     "' - Global variables differ in const'ness");
+
+      if (SGV->getInitializer() != DGV->getInitializer())
+        return Error(Err, "Global Variable Collision on '" + 
+                     ToStr(SGV->getType(), Src) + " %" + SGV->getName() +
+                    "' - External linkage globals have different initializers");
+
+      ValueMap.insert(std::make_pair(SGV, DGV));
+    } else if (SGV->hasAppendingLinkage()) {
+      // No linking is performed yet.  Just insert a new copy of the global, and
+      // keep track of the fact that it is an appending variable in the
+      // AppendingVars map.  The name is cleared out so that no linkage is
+      // performed.
+      GlobalVariable *NewDGV =
+        new GlobalVariable(SGV->getType()->getElementType(),
+                           SGV->isConstant(), SGV->getLinkage(), /*init*/0,
+                           "", Dest);
+
+      // Make sure to remember this mapping...
+      ValueMap.insert(std::make_pair(SGV, NewDGV));
+
+      // Keep track that this is an appending variable...
+      AppendingVars.insert(std::make_pair(SGV->getName(), NewDGV));
+    } else {
+      assert(0 && "Unknown linkage!");
+    }
+  }
+  return false;
+}
+
+
+// LinkGlobalInits - Update the initializers in the Dest module now that all
+// globals that may be referenced are in Dest.
+//
+static bool LinkGlobalInits(Module *Dest, const Module *Src,
+                            std::map<const Value*, Value*> &ValueMap,
+                            std::string *Err) {
+
+  // Loop over all of the globals in the src module, mapping them over as we go
+  //
+  for (Module::const_giterator I = Src->gbegin(), E = Src->gend(); I != E; ++I){
+    const GlobalVariable *SGV = I;
+
+    if (SGV->hasInitializer()) {      // Only process initialized GV's
+      // Figure out what the initializer looks like in the dest module...
+      Constant *SInit =
+        cast<Constant>(RemapOperand(SGV->getInitializer(), ValueMap, 0));
+
+      GlobalVariable *DGV = cast<GlobalVariable>(ValueMap[SGV]);    
+      if (DGV->hasInitializer()) {
+        if (SGV->hasExternalLinkage()) {
+          if (DGV->getInitializer() != SInit)
+            return Error(Err, "Global Variable Collision on '" + 
+                         ToStr(SGV->getType(), Src) +"':%"+SGV->getName()+
+                         " - Global variables have different initializers");
+        } else if (DGV->hasLinkOnceLinkage() || DGV->hasWeakLinkage()) {
+          // Nothing is required, mapped values will take the new global
+          // automatically.
+        } else if (SGV->hasLinkOnceLinkage() || SGV->hasWeakLinkage()) {
+          // Nothing is required, mapped values will take the new global
+          // automatically.
+        } else if (DGV->hasAppendingLinkage()) {
+          assert(0 && "Appending linkage unimplemented!");
+        } else {
+          assert(0 && "Unknown linkage!");
+        }
+      } else {
+        // Copy the initializer over now...
+        DGV->setInitializer(SInit);
+      }
+    }
+  }
+  return false;
+}
+
+// LinkFunctionProtos - Link the functions together between the two modules,
+// without doing function bodies... this just adds external function prototypes
+// to the Dest function...
+//
+static bool LinkFunctionProtos(Module *Dest, const Module *Src,
+                               std::map<const Value*, Value*> &ValueMap,
+                             std::map<std::string, GlobalValue*> &GlobalsByName,
+                               std::string *Err) {
+  SymbolTable *ST = (SymbolTable*)&Dest->getSymbolTable();
+  
+  // Loop over all of the functions in the src module, mapping them over as we
+  // go
+  //
+  for (Module::const_iterator I = Src->begin(), E = Src->end(); I != E; ++I) {
+    const Function *SF = I;   // SrcFunction
+    Function *DF = 0;
+    if (SF->hasName() && !SF->hasInternalLinkage()) {
+      // Check to see if may have to link the function.
+      if (!(DF = Dest->getFunction(SF->getName(), SF->getFunctionType()))) {
+        std::map<std::string, GlobalValue*>::iterator EF =
+          GlobalsByName.find(SF->getName());
+        if (EF != GlobalsByName.end())
+          DF = dyn_cast<Function>(EF->second);
+        if (DF && RecursiveResolveTypes(SF->getType(), DF->getType(), ST, ""))
+          DF = 0;  // FIXME: gross.
+      }
+    }
+
+    if (!DF || SF->hasInternalLinkage() || DF->hasInternalLinkage()) {
+      // Function does not already exist, simply insert an function signature
+      // identical to SF into the dest module...
+      Function *NewDF = new Function(SF->getFunctionType(), SF->getLinkage(),
+                                     SF->getName(), Dest);
+
+      // If the LLVM runtime renamed the function, but it is an externally
+      // visible symbol, DF must be an existing function with internal linkage.
+      // Rename it.
+      if (NewDF->getName() != SF->getName() && !NewDF->hasInternalLinkage())
+        ForceRenaming(NewDF, SF->getName());
+
+      // ... and remember this mapping...
+      ValueMap.insert(std::make_pair(SF, NewDF));
+    } else if (SF->isExternal()) {
+      // If SF is external or if both SF & DF are external..  Just link the
+      // external functions, we aren't adding anything.
+      ValueMap.insert(std::make_pair(SF, DF));
+    } else if (DF->isExternal()) {   // If DF is external but SF is not...
+      // Link the external functions, update linkage qualifiers
+      ValueMap.insert(std::make_pair(SF, DF));
+      DF->setLinkage(SF->getLinkage());
+
+    } else if (SF->hasWeakLinkage() || SF->hasLinkOnceLinkage()) {
+      // At this point we know that DF has LinkOnce, Weak, or External linkage.
+      ValueMap.insert(std::make_pair(SF, DF));
+
+      // Linkonce+Weak = Weak
+      if (DF->hasLinkOnceLinkage() && SF->hasWeakLinkage())
+        DF->setLinkage(SF->getLinkage());
+
+    } else if (DF->hasWeakLinkage() || DF->hasLinkOnceLinkage()) {
+      // At this point we know that SF has LinkOnce or External linkage.
+      ValueMap.insert(std::make_pair(SF, DF));
+      if (!SF->hasLinkOnceLinkage())   // Don't inherit linkonce linkage
+        DF->setLinkage(SF->getLinkage());
+
+    } else if (SF->getLinkage() != DF->getLinkage()) {
+      return Error(Err, "Functions named '" + SF->getName() +
+                   "' have different linkage specifiers!");
+    } else if (SF->hasExternalLinkage()) {
+      // The function is defined in both modules!!
+      return Error(Err, "Function '" + 
+                   ToStr(SF->getFunctionType(), Src) + "':\"" + 
+                   SF->getName() + "\" - Function is already defined!");
+    } else {
+      assert(0 && "Unknown linkage configuration found!");
+    }
+  }
+  return false;
+}
+
+// LinkFunctionBody - 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.
+//
+static bool LinkFunctionBody(Function *Dest, const Function *Src,
+                             std::map<const Value*, Value*> &GlobalMap,
+                             std::string *Err) {
+  assert(Src && Dest && Dest->isExternal() && !Src->isExternal());
+  std::map<const Value*, Value*> LocalMap;   // Map for function local values
+
+  // Go through and convert function arguments over...
+  Function::aiterator DI = Dest->abegin();
+  for (Function::const_aiterator I = Src->abegin(), E = Src->aend();
+       I != E; ++I, ++DI) {
+    DI->setName(I->getName());  // Copy the name information over...
+
+    // Add a mapping to our local map
+    LocalMap.insert(std::make_pair(I, DI));
+  }
+
+  // Loop over all of the basic blocks, copying the instructions over...
+  //
+  for (Function::const_iterator I = Src->begin(), E = Src->end(); I != E; ++I) {
+    // Create new basic block and add to mapping and the Dest function...
+    BasicBlock *DBB = new BasicBlock(I->getName(), Dest);
+    LocalMap.insert(std::make_pair(I, DBB));
+
+    // Loop over all of the instructions in the src basic block, copying them
+    // over.  Note that this is broken in a strict sense because the cloned
+    // instructions will still be referencing values in the Src module, not
+    // the remapped values.  In our case, however, we will not get caught and 
+    // so we can delay patching the values up until later...
+    //
+    for (BasicBlock::const_iterator II = I->begin(), IE = I->end(); 
+         II != IE; ++II) {
+      Instruction *DI = II->clone();
+      DI->setName(II->getName());
+      DBB->getInstList().push_back(DI);
+      LocalMap.insert(std::make_pair(II, DI));
+    }
+  }
+
+  // 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 (Function::iterator BB = Dest->begin(), BE = Dest->end(); BB != BE; ++BB)
+    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
+      for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
+           OI != OE; ++OI)
+        *OI = RemapOperand(*OI, LocalMap, &GlobalMap);
+
+  return false;
+}
+
+
+// LinkFunctionBodies - Link in the function bodies that are defined in the
+// source module into the DestModule.  This consists basically of copying the
+// function over and fixing up references to values.
+//
+static bool LinkFunctionBodies(Module *Dest, const Module *Src,
+                               std::map<const Value*, Value*> &ValueMap,
+                               std::string *Err) {
+
+  // Loop over all of the functions in the src module, mapping them over as we
+  // go
+  //
+  for (Module::const_iterator SF = Src->begin(), E = Src->end(); SF != E; ++SF){
+    if (!SF->isExternal()) {                  // No body if function is external
+      Function *DF = cast<Function>(ValueMap[SF]); // Destination function
+
+      // DF not external SF external?
+      if (DF->isExternal()) {
+        // Only provide the function body if there isn't one already.
+        if (LinkFunctionBody(DF, SF, ValueMap, Err))
+          return true;
+      }
+    }
+  }
+  return false;
+}
+
+// LinkAppendingVars - If there were any appending global variables, link them
+// together now.  Return true on error.
+//
+static bool LinkAppendingVars(Module *M,
+                  std::multimap<std::string, GlobalVariable *> &AppendingVars,
+                              std::string *ErrorMsg) {
+  if (AppendingVars.empty()) return false; // Nothing to do.
+  
+  // Loop over the multimap of appending vars, processing any variables with the
+  // same name, forming a new appending global variable with both of the
+  // initializers merged together, then rewrite references to the old variables
+  // and delete them.
+  //
+  std::vector<Constant*> Inits;
+  while (AppendingVars.size() > 1) {
+    // Get the first two elements in the map...
+    std::multimap<std::string,
+      GlobalVariable*>::iterator Second = AppendingVars.begin(), First=Second++;
+
+    // If the first two elements are for different names, there is no pair...
+    // Otherwise there is a pair, so link them together...
+    if (First->first == Second->first) {
+      GlobalVariable *G1 = First->second, *G2 = Second->second;
+      const ArrayType *T1 = cast<ArrayType>(G1->getType()->getElementType());
+      const ArrayType *T2 = cast<ArrayType>(G2->getType()->getElementType());
+      
+      // Check to see that they two arrays agree on type...
+      if (T1->getElementType() != T2->getElementType())
+        return Error(ErrorMsg,
+         "Appending variables with different element types need to be linked!");
+      if (G1->isConstant() != G2->isConstant())
+        return Error(ErrorMsg,
+                     "Appending variables linked with different const'ness!");
+
+      unsigned NewSize = T1->getNumElements() + T2->getNumElements();
+      ArrayType *NewType = ArrayType::get(T1->getElementType(), NewSize);
+
+      // Create the new global variable...
+      GlobalVariable *NG =
+        new GlobalVariable(NewType, G1->isConstant(), G1->getLinkage(),
+                           /*init*/0, First->first, M);
+
+      // Merge the initializer...
+      Inits.reserve(NewSize);
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G1->getInitializer())) {
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(I->getOperand(i));
+      } else {
+        assert(isa<ConstantAggregateZero>(G1->getInitializer()));
+        Constant *CV = Constant::getNullValue(T1->getElementType());
+        for (unsigned i = 0, e = T1->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
+      if (ConstantArray *I = dyn_cast<ConstantArray>(G2->getInitializer())) {
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(I->getOperand(i));
+      } else {
+        assert(isa<ConstantAggregateZero>(G2->getInitializer()));
+        Constant *CV = Constant::getNullValue(T2->getElementType());
+        for (unsigned i = 0, e = T2->getNumElements(); i != e; ++i)
+          Inits.push_back(CV);
+      }
+      NG->setInitializer(ConstantArray::get(NewType, Inits));
+      Inits.clear();
+
+      // Replace any uses of the two global variables with uses of the new
+      // global...
+
+      // FIXME: This should rewrite simple/straight-forward uses such as
+      // getelementptr instructions to not use the Cast!
+      G1->replaceAllUsesWith(ConstantExpr::getCast(NG, G1->getType()));
+      G2->replaceAllUsesWith(ConstantExpr::getCast(NG, G2->getType()));
+
+      // Remove the two globals from the module now...
+      M->getGlobalList().erase(G1);
+      M->getGlobalList().erase(G2);
+
+      // Put the new global into the AppendingVars map so that we can handle
+      // linking of more than two vars...
+      Second->second = NG;
+    }
+    AppendingVars.erase(First);
+  }
+
+  return false;
+}
+
+
+// LinkModules - This function links two modules together, with the resulting
+// left 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 llvm::LinkModules(Module *Dest, const Module *Src, std::string *ErrorMsg) {
+  assert(Dest != 0 && "Invalid Destination module");
+  assert(Src  != 0 && "Invalid Source Module");
+
+  if (Dest->getEndianness() == Module::AnyEndianness)
+    Dest->setEndianness(Src->getEndianness());
+  if (Dest->getPointerSize() == Module::AnyPointerSize)
+    Dest->setPointerSize(Src->getPointerSize());
+
+  if (Src->getEndianness() != Module::AnyEndianness &&
+      Dest->getEndianness() != Src->getEndianness())
+    std::cerr << "WARNING: Linking two modules of different endianness!\n";
+  if (Src->getPointerSize() != Module::AnyPointerSize &&
+      Dest->getPointerSize() != Src->getPointerSize())
+    std::cerr << "WARNING: Linking two modules of different pointer size!\n";
+
+  // Update the destination module's dependent libraries list with the libraries 
+  // from the source module. There's no opportunity for duplicates here as the
+  // Module ensures that duplicate insertions are discarded.
+  Module::lib_iterator SI = Src->lib_begin();
+  Module::lib_iterator SE = Src->lib_end();
+  while ( SI != SE ) {
+    Dest->addLibrary(*SI);
+    ++SI;
+  }
+
+  // LinkTypes - Go through the symbol table of the Src module and see if any
+  // types are named in the src module that are not named in the Dst module.
+  // Make sure there are no type name conflicts.
+  //
+  if (LinkTypes(Dest, Src, ErrorMsg)) return true;
+
+  // ValueMap - Mapping of values from what they used to be in Src, to what they
+  // are now in Dest.
+  //
+  std::map<const Value*, Value*> ValueMap;
+
+  // AppendingVars - Keep track of global variables in the destination module
+  // with appending linkage.  After the module is linked together, they are
+  // appended and the module is rewritten.
+  //
+  std::multimap<std::string, GlobalVariable *> AppendingVars;
+
+  // GlobalsByName - The LLVM SymbolTable class fights our best efforts at
+  // linking by separating globals by type.  Until PR411 is fixed, we replicate
+  // it's functionality here.
+  std::map<std::string, GlobalValue*> GlobalsByName;
+
+  for (Module::giterator I = Dest->gbegin(), E = Dest->gend(); I != E; ++I) {
+    // Add all of the appending globals already in the Dest module to
+    // AppendingVars.
+    if (I->hasAppendingLinkage())
+      AppendingVars.insert(std::make_pair(I->getName(), I));
+
+    // Keep track of all globals by name.
+    if (!I->hasInternalLinkage() && I->hasName())
+      GlobalsByName[I->getName()] = I;
+  }
+
+  // Keep track of all globals by name.
+  for (Module::iterator I = Dest->begin(), E = Dest->end(); I != E; ++I)
+    if (!I->hasInternalLinkage() && I->hasName())
+      GlobalsByName[I->getName()] = I;
+
+  // Insert all of the globals in src into the Dest module... without linking
+  // initializers (which could refer to functions not yet mapped over).
+  //
+  if (LinkGlobals(Dest, Src, ValueMap, AppendingVars, GlobalsByName, ErrorMsg))
+    return true;
+
+  // Link the functions together between the two modules, without doing function
+  // bodies... this just adds external function prototypes to the Dest
+  // function...  We do this so that when we begin processing function bodies,
+  // all of the global values that may be referenced are available in our
+  // ValueMap.
+  //
+  if (LinkFunctionProtos(Dest, Src, ValueMap, GlobalsByName, ErrorMsg))
+    return true;
+
+  // Update the initializers in the Dest module now that all globals that may
+  // be referenced are in Dest.
+  //
+  if (LinkGlobalInits(Dest, Src, ValueMap, ErrorMsg)) return true;
+
+  // Link in the function bodies that are defined in the source module into the
+  // DestModule.  This consists basically of copying the function over and
+  // fixing up references to values.
+  //
+  if (LinkFunctionBodies(Dest, Src, ValueMap, ErrorMsg)) return true;
+
+  // If there were any appending global variables, link them together now.
+  //
+  if (LinkAppendingVars(Dest, AppendingVars, ErrorMsg)) return true;
+
+  // If the source library's module id is in the dependent library list of the
+  // destination library, remove it since that module is now linked in.
+  sys::Path modId;
+  modId.setFile(Src->getModuleIdentifier());
+  if (!modId.isEmpty())
+    Dest->removeLibrary(modId.getBasename());
+
+  return false;
+}
+
+// vim: sw=2