It's not necessary to do rounding for alloca operations when the requested

alignment is equal to the stack alignment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 1652 insertions, 0 deletions

diff --git a/lib/Linker/LinkArchives.cpp b/lib/Linker/LinkArchives.cpp
new file mode 100644
index 0000000..381d0e7
--- /dev/null
+++ b/lib/Linker/LinkArchives.cpp
@@ -0,0 +1,193 @@
+//===- lib/Linker/LinkArchives.cpp - Link LLVM objects and libraries ------===//
+//
+//                     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 contains routines to handle linking together LLVM bitcode files,
+// and to handle annoying things like static libraries.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Linker.h"
+#include "llvm/Module.h"
+#include "llvm/ModuleProvider.h"
+#include "llvm/ADT/SetOperations.h"
+#include "llvm/Bitcode/Archive.h"
+#include "llvm/Config/config.h"
+#include <memory>
+#include <set>
+using namespace llvm;
+
+/// GetAllUndefinedSymbols - calculates the set of undefined symbols that still
+/// exist in an LLVM module. This is a bit tricky because there may be two
+/// symbols with the same name but different LLVM types that will be resolved to
+/// each other but aren't currently (thus we need to treat it as resolved).
+///
+/// Inputs:
+///  M - The module in which to find undefined symbols.
+///
+/// Outputs:
+///  UndefinedSymbols - A set of C++ strings containing the name of all
+///                     undefined symbols.
+///
+static void
+GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) {
+  std::set<std::string> DefinedSymbols;
+  UndefinedSymbols.clear();
+
+  // If the program doesn't define a main, try pulling one in from a .a file.
+  // This is needed for programs where the main function is defined in an
+  // archive, such f2c'd programs.
+  Function *Main = M->getFunction("main");
+  if (Main == 0 || Main->isDeclaration())
+    UndefinedSymbols.insert("main");
+
+  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
+    if (I->hasName()) {
+      if (I->isDeclaration())
+        UndefinedSymbols.insert(I->getName());
+      else if (!I->hasInternalLinkage()) {
+        assert(!I->hasDLLImportLinkage()
+               && "Found dllimported non-external symbol!");
+        DefinedSymbols.insert(I->getName());
+      }      
+    }
+  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
+       I != E; ++I)
+    if (I->hasName()) {
+      if (I->isDeclaration())
+        UndefinedSymbols.insert(I->getName());
+      else if (!I->hasInternalLinkage()) {
+        assert(!I->hasDLLImportLinkage()
+               && "Found dllimported non-external symbol!");
+        DefinedSymbols.insert(I->getName());
+      }      
+    }
+
+  // Prune out any defined symbols from the undefined symbols set...
+  for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
+       I != UndefinedSymbols.end(); )
+    if (DefinedSymbols.count(*I))
+      UndefinedSymbols.erase(I++);  // This symbol really is defined!
+    else
+      ++I; // Keep this symbol in the undefined symbols list
+}
+
+/// LinkInArchive - opens an archive library and link in all objects which
+/// provide symbols that are currently undefined.
+///
+/// Inputs:
+///  Filename - The pathname of the archive.
+///
+/// Return Value:
+///  TRUE  - An error occurred.
+///  FALSE - No errors.
+bool
+Linker::LinkInArchive(const sys::Path &Filename, bool &is_native) {
+
+  // Make sure this is an archive file we're dealing with
+  if (!Filename.isArchive())
+    return error("File '" + Filename.toString() + "' is not an archive.");
+
+  // Open the archive file
+  verbose("Linking archive file '" + Filename.toString() + "'");
+
+  // Find all of the symbols currently undefined in the bitcode program.
+  // If all the symbols are defined, the program is complete, and there is
+  // no reason to link in any archive files.
+  std::set<std::string> UndefinedSymbols;
+  GetAllUndefinedSymbols(Composite, UndefinedSymbols);
+
+  if (UndefinedSymbols.empty()) {
+    verbose("No symbols undefined, skipping library '" +
+            Filename.toString() + "'");
+    return false;  // No need to link anything in!
+  }
+
+  std::string ErrMsg;
+  std::auto_ptr<Archive> AutoArch (
+    Archive::OpenAndLoadSymbols(Filename,&ErrMsg));
+
+  Archive* arch = AutoArch.get();
+
+  if (!arch)
+    return error("Cannot read archive '" + Filename.toString() +
+                 "': " + ErrMsg);
+  if (!arch->isBitcodeArchive()) {
+    is_native = true;
+    return false;
+  }
+  is_native = false;
+
+  // Save a set of symbols that are not defined by the archive. Since we're
+  // entering a loop, there's no point searching for these multiple times. This
+  // variable is used to "set_subtract" from the set of undefined symbols.
+  std::set<std::string> NotDefinedByArchive;
+
+  // Save the current set of undefined symbols, because we may have to make
+  // multiple passes over the archive:
+  std::set<std::string> CurrentlyUndefinedSymbols;
+
+  do {
+    CurrentlyUndefinedSymbols = UndefinedSymbols;
+
+    // Find the modules we need to link into the target module
+    std::set<ModuleProvider*> Modules;
+    if (!arch->findModulesDefiningSymbols(UndefinedSymbols, Modules, &ErrMsg))
+      return error("Cannot find symbols in '" + Filename.toString() + 
+                   "': " + ErrMsg);
+
+    // If we didn't find any more modules to link this time, we are done
+    // searching this archive.
+    if (Modules.empty())
+      break;
+
+    // Any symbols remaining in UndefinedSymbols after
+    // findModulesDefiningSymbols are ones that the archive does not define. So
+    // we add them to the NotDefinedByArchive variable now.
+    NotDefinedByArchive.insert(UndefinedSymbols.begin(),
+        UndefinedSymbols.end());
+
+    // Loop over all the ModuleProviders that we got back from the archive
+    for (std::set<ModuleProvider*>::iterator I=Modules.begin(), E=Modules.end();
+         I != E; ++I) {
+
+      // Get the module we must link in.
+      std::string moduleErrorMsg;
+      std::auto_ptr<Module> AutoModule((*I)->releaseModule( &moduleErrorMsg ));
+      Module* aModule = AutoModule.get();
+
+      if (aModule != NULL) {
+        verbose("  Linking in module: " + aModule->getModuleIdentifier());
+
+        // Link it in
+        if (LinkInModule(aModule, &moduleErrorMsg)) {
+          return error("Cannot link in module '" +
+                       aModule->getModuleIdentifier() + "': " + moduleErrorMsg);
+        }
+      } 
+    }
+    
+    // Get the undefined symbols from the aggregate module. This recomputes the
+    // symbols we still need after the new modules have been linked in.
+    GetAllUndefinedSymbols(Composite, UndefinedSymbols);
+
+    // At this point we have two sets of undefined symbols: UndefinedSymbols
+    // which holds the undefined symbols from all the modules, and
+    // NotDefinedByArchive which holds symbols we know the archive doesn't
+    // define. There's no point searching for symbols that we won't find in the
+    // archive so we subtract these sets.
+    set_subtract(UndefinedSymbols, NotDefinedByArchive);
+
+    // If there's no symbols left, no point in continuing to search the
+    // archive.
+    if (UndefinedSymbols.empty())
+      break;
+  } while (CurrentlyUndefinedSymbols != UndefinedSymbols);
+
+  return false;
+}
diff --git a/lib/Linker/LinkItems.cpp b/lib/Linker/LinkItems.cpp
new file mode 100644
index 0000000..3cf1f6b
--- /dev/null
+++ b/lib/Linker/LinkItems.cpp
@@ -0,0 +1,221 @@
+//===- lib/Linker/LinkItems.cpp - Link LLVM objects and libraries ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Reid Spencer and is distributed under the
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains routines to handle linking together LLVM bitcode files,
+// and to handle annoying things like static libraries.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Linker.h"
+#include "llvm/Module.h"
+
+using namespace llvm;
+
+// LinkItems - This function is the main entry point into linking. It takes a
+// list of LinkItem which indicates the order the files should be linked and
+// how each file should be treated (plain file or with library search). The
+// function only links bitcode and produces a result list of items that are
+// native objects. 
+bool
+Linker::LinkInItems(const ItemList& Items, ItemList& NativeItems) {
+  // Clear the NativeItems just in case
+  NativeItems.clear();
+
+  // For each linkage item ...
+  for (ItemList::const_iterator I = Items.begin(), E = Items.end();
+       I != E; ++I) {
+    if (I->second) {
+      // Link in the library suggested.
+      bool is_native = false;
+      if (LinkInLibrary(I->first, is_native))
+        return true;
+      if (is_native)
+        NativeItems.push_back(*I);
+    } else {
+      // Link in the file suggested
+      bool is_native = false;
+      if (LinkInFile(sys::Path(I->first), is_native))
+        return true;
+      if (is_native)
+        NativeItems.push_back(*I);
+    }
+  }
+
+  // At this point we have processed all the link items provided to us. Since
+  // we have an aggregated module at this point, the dependent libraries in
+  // that module should also be aggregated with duplicates eliminated. This is
+  // now the time to process the dependent libraries to resolve any remaining
+  // symbols.
+  bool is_native;
+  for (Module::lib_iterator I = Composite->lib_begin(),
+         E = Composite->lib_end(); I != E; ++I) {
+    if(LinkInLibrary(*I, is_native))
+      return true;
+    if (is_native)
+      NativeItems.push_back(std::make_pair(*I, true));
+  }
+
+  return false;
+}
+
+
+/// LinkInLibrary - links one library into the HeadModule.
+///
+bool Linker::LinkInLibrary(const std::string& Lib, bool& is_native) {
+  is_native = false;
+  // Determine where this library lives.
+  sys::Path Pathname = FindLib(Lib);
+  if (Pathname.isEmpty())
+    return warning("Cannot find library '" + Lib + "'");
+
+  // If its an archive, try to link it in
+  std::string Magic;
+  Pathname.getMagicNumber(Magic, 64);
+  switch (sys::IdentifyFileType(Magic.c_str(), 64)) {
+    default: assert(0 && "Bad file type identification");
+    case sys::Unknown_FileType:
+      return warning("Supposed library '" + Lib + "' isn't a library.");
+
+    case sys::Bitcode_FileType:
+      // LLVM ".so" file.
+      if (LinkInFile(Pathname, is_native))
+        return error("Cannot link file '" + Pathname.toString() + "'");
+      break;
+
+    case sys::Archive_FileType:
+      if (LinkInArchive(Pathname, is_native))
+        return error("Cannot link archive '" + Pathname.toString() + "'");
+      break;
+
+    case sys::ELF_Relocatable_FileType:
+    case sys::ELF_SharedObject_FileType:
+    case sys::Mach_O_Object_FileType:
+    case sys::Mach_O_FixedVirtualMemorySharedLib_FileType:
+    case sys::Mach_O_DynamicallyLinkedSharedLib_FileType:
+    case sys::Mach_O_DynamicallyLinkedSharedLibStub_FileType:
+    case sys::COFF_FileType:
+      is_native = true;
+      break;
+  }
+  return false;
+}
+
+/// LinkLibraries - takes the specified library files and links them into the
+/// main bitcode object file.
+///
+/// Inputs:
+///  Libraries  - The list of libraries to link into the module.
+///
+/// Return value:
+///  FALSE - No error.
+///  TRUE  - Error.
+///
+bool Linker::LinkInLibraries(const std::vector<std::string> &Libraries) {
+
+  // Process the set of libraries we've been provided.
+  bool is_native = false;
+  for (unsigned i = 0; i < Libraries.size(); ++i)
+    if (LinkInLibrary(Libraries[i], is_native))
+      return true;
+
+  // At this point we have processed all the libraries provided to us. Since
+  // we have an aggregated module at this point, the dependent libraries in
+  // that module should also be aggregated with duplicates eliminated. This is
+  // now the time to process the dependent libraries to resolve any remaining
+  // symbols.
+  const Module::LibraryListType& DepLibs = Composite->getLibraries();
+  for (Module::LibraryListType::const_iterator I = DepLibs.begin(),
+         E = DepLibs.end(); I != E; ++I)
+    if (LinkInLibrary(*I, is_native))
+      return true;
+
+  return false;
+}
+
+/// LinkInFile - opens a bitcode file and links in all objects which
+/// provide symbols that are currently undefined.
+///
+/// Inputs:
+///  File - The pathname of the bitcode file.
+///
+/// Outputs:
+///  ErrorMessage - A C++ string detailing what error occurred, if any.
+///
+/// Return Value:
+///  TRUE  - An error occurred.
+///  FALSE - No errors.
+///
+bool Linker::LinkInFile(const sys::Path &File, bool &is_native) {
+  is_native = false;
+  // Make sure we can at least read the file
+  if (!File.canRead())
+    return error("Cannot find linker input '" + File.toString() + "'");
+
+  // If its an archive, try to link it in
+  std::string Magic;
+  File.getMagicNumber(Magic, 64);
+  switch (sys::IdentifyFileType(Magic.c_str(), 64)) {
+    default: assert(0 && "Bad file type identification");
+    case sys::Unknown_FileType:
+      return warning("Supposed object file '" + File.toString() + 
+                     "' not recognized as such");
+
+    case sys::Archive_FileType:
+      // A user may specify an ar archive without -l, perhaps because it
+      // is not installed as a library. Detect that and link the archive.
+      verbose("Linking archive file '" + File.toString() + "'");
+      if (LinkInArchive(File, is_native))
+        return error("Cannot link archive '" + File.toString() + "'");
+      break;
+
+    case sys::Bitcode_FileType: {
+      verbose("Linking bitcode file '" + File.toString() + "'");
+      std::auto_ptr<Module> M(LoadObject(File));
+      if (M.get() == 0)
+        return error("Cannot load file '" + File.toString() + "'" + Error);
+      if (LinkInModule(M.get()))
+        return error("Cannot link file '" + File.toString() + "'" + Error);
+
+      verbose("Linked in file '" + File.toString() + "'");
+      break;
+    }
+
+    case sys::ELF_Relocatable_FileType:
+    case sys::ELF_SharedObject_FileType:
+    case sys::Mach_O_Object_FileType:
+    case sys::Mach_O_FixedVirtualMemorySharedLib_FileType:
+    case sys::Mach_O_DynamicallyLinkedSharedLib_FileType:
+    case sys::Mach_O_DynamicallyLinkedSharedLibStub_FileType:
+    case sys::COFF_FileType:
+      is_native = true;
+      break;
+  }
+  return false;
+}
+
+/// LinkFiles - takes a module and a list of files and links them all together.
+/// It locates the file either in the current directory, as its absolute
+/// or relative pathname, or as a file somewhere in LLVM_LIB_SEARCH_PATH.
+///
+/// Inputs:
+///  Files      - A vector of sys::Path indicating the LLVM bitcode filenames
+///               to be linked.  The names can refer to a mixture of pure LLVM
+///               bitcode files and archive (ar) formatted files.
+///
+/// Return value:
+///  FALSE - No errors.
+///  TRUE  - Some error occurred.
+///
+bool Linker::LinkInFiles(const std::vector<sys::Path> &Files) {
+  bool is_native;
+  for (unsigned i = 0; i < Files.size(); ++i)
+    if (LinkInFile(Files[i], is_native))
+      return true;
+  return false;
+}
diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
new file mode 100644
index 0000000..462a4b7
--- /dev/null
+++ b/lib/Linker/LinkModules.cpp
@@ -0,0 +1,1045 @@
+//===- 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/Linker.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Module.h"
+#include "llvm/TypeSymbolTable.h"
+#include "llvm/ValueSymbolTable.h"
+#include "llvm/Instructions.h"
+#include "llvm/Assembly/Writer.h"
+#include "llvm/Support/Streams.h"
+#include "llvm/System/Path.h"
+#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;
+}
+
+// ToStr - Simple wrapper function to convert a type to a string.
+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,
+                         TypeSymbolTable *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,
+                                   TypeSymbolTable *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::IntegerTyID: {
+    if (cast<IntegerType>(DestTyT)->getBitWidth() !=
+        cast<IntegerType>(SrcTyT)->getBitWidth())
+      return true;
+    return false;
+  }
+  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,
+                                  TypeSymbolTable *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) {
+        TypeSymbolTable *DestST = &Dest->getTypeSymbolTable();
+  const TypeSymbolTable *SrcST  = &Src->getTypeSymbolTable();
+
+  // Look for a type plane for Type's...
+  TypeSymbolTable::const_iterator TI = SrcST->begin();
+  TypeSymbolTable::const_iterator TE = SrcST->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->lookup(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->lookup(Name);
+      Type *T2 = DestST->lookup(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->lookup(Name));
+        PATypeHolder T2(DestST->lookup(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.
+      if (DelayedTypesToResolve.size() == OldSize) {
+        // 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) {
+    cerr << " Fr: " << (void*)I->first << " ";
+    I->first->dump();
+    cerr << " To: " << (void*)I->second << " ";
+    I->second->dump();
+    cerr << "\n";
+  }
+}
+
+
+// RemapOperand - Use ValueMap to convert constants from one module to another.
+static Value *RemapOperand(const Value *In,
+                           std::map<const Value*, Value*> &ValueMap) {
+  std::map<const Value*,Value*>::const_iterator I = ValueMap.find(In);
+  if (I != ValueMap.end()) 
+    return I->second;
+
+  // Check to see if it's a constant that we are interested in transforming.
+  Value *Result = 0;
+  if (const Constant *CPV = dyn_cast<Constant>(In)) {
+    if ((!isa<DerivedType>(CPV->getType()) && !isa<ConstantExpr>(CPV)) ||
+        isa<ConstantInt>(CPV) || isa<ConstantAggregateZero>(CPV))
+      return const_cast<Constant*>(CPV);   // Simple constants stay identical.
+
+    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), ValueMap));
+      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), ValueMap));
+      Result = ConstantStruct::get(cast<StructType>(CPS->getType()), Operands);
+    } else if (isa<ConstantPointerNull>(CPV) || isa<UndefValue>(CPV)) {
+      Result = const_cast<Constant*>(CPV);
+    } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(CPV)) {
+      std::vector<Constant*> Operands(CP->getNumOperands());
+      for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
+        Operands[i] = cast<Constant>(RemapOperand(CP->getOperand(i), ValueMap));
+      Result = ConstantVector::get(Operands);
+    } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(CPV)) {
+      std::vector<Constant*> Ops;
+      for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i)
+        Ops.push_back(cast<Constant>(RemapOperand(CE->getOperand(i),ValueMap)));
+      Result = CE->getWithOperands(Ops);
+    } else if (isa<GlobalValue>(CPV)) {
+      assert(0 && "Unmapped global?");
+    } else {
+      assert(0 && "Unknown type of derived type constant value!");
+    }
+  } else if (isa<InlineAsm>(In)) {
+    Result = const_cast<Value*>(In);
+  }
+  
+  // Cache the mapping in our local map structure
+  if (Result) {
+    ValueMap.insert(std::make_pair(In, Result));
+    return Result;
+  }
+  
+
+  cerr << "LinkModules ValueMap: \n";
+  PrintMap(ValueMap);
+
+  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");
+  ValueSymbolTable &ST = GV->getParent()->getValueSymbolTable();
+
+  // If there is a conflict, rename the conflict.
+  if (GlobalValue *ConflictGV = cast_or_null<GlobalValue>(ST.lookup(Name))) {
+    assert(ConflictGV->hasInternalLinkage() &&
+           "Not conflicting with a static global, should link instead!");
+    GV->takeName(ConflictGV);
+    ConflictGV->setName(Name);    // This will cause ConflictGV to get renamed
+    assert(ConflictGV->getName() != Name && "ForceRenaming didn't work");
+  } else {
+    GV->setName(Name);              // Force the name back
+  }
+}
+
+/// CopyGVAttributes - copy additional attributes (those not needed to construct
+/// a GlobalValue) from the SrcGV to the DestGV. 
+static void CopyGVAttributes(GlobalValue *DestGV, const GlobalValue *SrcGV) {
+  // Propagate alignment, visibility and section info.
+  DestGV->setAlignment(std::max(DestGV->getAlignment(), SrcGV->getAlignment()));
+  DestGV->setSection(SrcGV->getSection());
+  DestGV->setVisibility(SrcGV->getVisibility());
+  if (const Function *SrcF = dyn_cast<Function>(SrcGV)) {
+    Function *DestF = cast<Function>(DestGV);
+    DestF->setCallingConv(SrcF->getCallingConv());
+  }
+}
+
+/// GetLinkageResult - This analyzes the two global values and determines what
+/// the result will look like in the destination module.  In particular, it
+/// computes the resultant linkage type, computes whether the global in the
+/// source should be copied over to the destination (replacing the existing
+/// one), and computes whether this linkage is an error or not. It also performs
+/// visibility checks: we cannot link together two symbols with different
+/// visibilities.
+static bool GetLinkageResult(GlobalValue *Dest, GlobalValue *Src,
+                             GlobalValue::LinkageTypes &LT, bool &LinkFromSrc,
+                             std::string *Err) {
+  assert((!Dest || !Src->hasInternalLinkage()) &&
+         "If Src has internal linkage, Dest shouldn't be set!");
+  if (!Dest) {
+    // Linking something to nothing.
+    LinkFromSrc = true;
+    LT = Src->getLinkage();
+  } else if (Src->isDeclaration()) {
+    // If Src is external or if both Src & Drc are external..  Just link the
+    // external globals, we aren't adding anything.
+    if (Src->hasDLLImportLinkage()) {
+      // If one of GVs has DLLImport linkage, result should be dllimport'ed.
+      if (Dest->isDeclaration()) {
+        LinkFromSrc = true;
+        LT = Src->getLinkage();
+      }      
+    } else if (Dest->hasExternalWeakLinkage()) {
+      //If the Dest is weak, use the source linkage
+      LinkFromSrc = true;
+      LT = Src->getLinkage();
+    } else {
+      LinkFromSrc = false;
+      LT = Dest->getLinkage();
+    }
+  } else if (Dest->isDeclaration() && !Dest->hasDLLImportLinkage()) {
+    // If Dest is external but Src is not:
+    LinkFromSrc = true;
+    LT = Src->getLinkage();
+  } else if (Src->hasAppendingLinkage() || Dest->hasAppendingLinkage()) {
+    if (Src->getLinkage() != Dest->getLinkage())
+      return Error(Err, "Linking globals named '" + Src->getName() +
+            "': can only link appending global with another appending global!");
+    LinkFromSrc = true; // Special cased.
+    LT = Src->getLinkage();
+  } else if (Src->hasWeakLinkage() || Src->hasLinkOnceLinkage()) {
+    // At this point we know that Dest has LinkOnce, External*, Weak, or
+    // DLL* linkage.
+    if ((Dest->hasLinkOnceLinkage() && Src->hasWeakLinkage()) ||
+        Dest->hasExternalWeakLinkage()) {
+      LinkFromSrc = true;
+      LT = Src->getLinkage();
+    } else {
+      LinkFromSrc = false;
+      LT = Dest->getLinkage();
+    }
+  } else if (Dest->hasWeakLinkage() || Dest->hasLinkOnceLinkage()) {
+    // At this point we know that Src has External* or DLL* linkage.
+    if (Src->hasExternalWeakLinkage()) {
+      LinkFromSrc = false;
+      LT = Dest->getLinkage();
+    } else {
+      LinkFromSrc = true;
+      LT = GlobalValue::ExternalLinkage;
+    }
+  } else {
+    assert((Dest->hasExternalLinkage() ||
+            Dest->hasDLLImportLinkage() ||
+            Dest->hasDLLExportLinkage() ||
+            Dest->hasExternalWeakLinkage()) &&
+           (Src->hasExternalLinkage() ||
+            Src->hasDLLImportLinkage() ||
+            Src->hasDLLExportLinkage() ||
+            Src->hasExternalWeakLinkage()) &&
+           "Unexpected linkage type!");
+    return Error(Err, "Linking globals named '" + Src->getName() +
+                 "': symbol multiply defined!");
+  }
+
+  // Check visibility
+  if (Dest && Src->getVisibility() != Dest->getVisibility())
+    return Error(Err, "Linking globals named '" + Src->getName() +
+                 "': symbols have different visibilities!");
+  return false;
+}
+
+// LinkGlobals - Loop through the global variables in the src module and merge
+// them into the dest module.
+static bool LinkGlobals(Module *Dest, Module *Src,
+                        std::map<const Value*, Value*> &ValueMap,
+                    std::multimap<std::string, GlobalVariable *> &AppendingVars,
+                        std::string *Err) {
+  // Loop over all of the globals in the src module, mapping them over as we go
+  for (Module::global_iterator I = Src->global_begin(), E = Src->global_end();
+       I != E; ++I) {
+    GlobalVariable *SGV = I;
+    GlobalVariable *DGV = 0;
+    // Check to see if may have to link the global.
+    if (SGV->hasName() && !SGV->hasInternalLinkage()) {
+      DGV = Dest->getGlobalVariable(SGV->getName());
+      if (DGV && DGV->getType() != SGV->getType())
+        // If types don't agree due to opaque types, try to resolve them.
+        RecursiveResolveTypes(SGV->getType(), DGV->getType(), 
+                              &Dest->getTypeSymbolTable(), "");
+    }
+
+    if (DGV && DGV->hasInternalLinkage())
+      DGV = 0;
+
+    assert(SGV->hasInitializer() || SGV->hasExternalWeakLinkage() ||
+           SGV->hasExternalLinkage() || SGV->hasDLLImportLinkage() &&
+           "Global must either be external or have an initializer!");
+
+    GlobalValue::LinkageTypes NewLinkage = GlobalValue::InternalLinkage;
+    bool LinkFromSrc = false;
+    if (GetLinkageResult(DGV, SGV, NewLinkage, LinkFromSrc, Err))
+      return true;
+
+    if (!DGV) {
+      // 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, SGV->isThreadLocal());
+      // Propagate alignment, visibility and section info.
+      CopyGVAttributes(NewDGV, SGV);
+
+      // 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 (DGV->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, SGV->isThreadLocal());
+
+      // Propagate alignment, section and visibility  info.
+      NewDGV->setAlignment(DGV->getAlignment());
+      CopyGVAttributes(NewDGV, SGV);
+
+      // 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 {
+      // Propagate alignment, section, and visibility info.
+      CopyGVAttributes(DGV, SGV);
+
+      // Otherwise, perform the mapping as instructed by GetLinkageResult.  If
+      // the types don't match, and if we are to link from the source, nuke DGV
+      // and create a new one of the appropriate type.
+      if (SGV->getType() != DGV->getType() && LinkFromSrc) {
+        GlobalVariable *NewDGV =
+          new GlobalVariable(SGV->getType()->getElementType(),
+                             DGV->isConstant(), DGV->getLinkage());
+        NewDGV->setThreadLocal(DGV->isThreadLocal());
+        CopyGVAttributes(NewDGV, DGV);
+        Dest->getGlobalList().insert(DGV, NewDGV);
+        DGV->replaceAllUsesWith(
+            ConstantExpr::getBitCast(NewDGV, DGV->getType()));
+        DGV->eraseFromParent();
+        NewDGV->setName(SGV->getName());
+        DGV = NewDGV;
+      }
+
+      DGV->setLinkage(NewLinkage);
+
+      if (LinkFromSrc) {
+        // Inherit const as appropriate
+        DGV->setConstant(SGV->isConstant());
+        DGV->setInitializer(0);
+      } else {
+        if (SGV->isConstant() && !DGV->isConstant()) {
+          if (DGV->isDeclaration())
+            DGV->setConstant(true);
+        }
+        SGV->setLinkage(GlobalValue::ExternalLinkage);
+        SGV->setInitializer(0);
+      }
+
+      ValueMap.insert(
+        std::make_pair(SGV, ConstantExpr::getBitCast(DGV, SGV->getType())));
+    }
+  }
+  return false;
+}
+
+// LinkAlias - Loop through the alias in the src module and link them into the
+// dest module.
+static bool LinkAlias(Module *Dest, const Module *Src, std::string *Err) {
+  // Loop over all alias in the src module
+  for (Module::const_alias_iterator I = Src->alias_begin(),
+         E = Src->alias_end(); I != E; ++I) {
+    const GlobalAlias *GA = I;
+
+    GlobalValue *NewAliased = NULL;
+    const GlobalValue *Aliased = GA->getAliasedGlobal();
+    if (isa<GlobalVariable>(*Aliased))
+      NewAliased = Dest->getGlobalVariable(Aliased->getName());
+    else if (isa<Function>(*Aliased))
+      NewAliased = Dest->getFunction(Aliased->getName());
+    // FIXME: we should handle the bitcast alias.
+    assert(NewAliased && "Can't find the aliased GV.");
+
+    GlobalAlias *NewGA = new GlobalAlias(GA->getType(), GA->getLinkage(),
+                                         GA->getName(), NewAliased, Dest);
+    CopyGVAttributes(NewGA, GA);
+  }
+  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_global_iterator I = Src->global_begin(),
+       E = Src->global_end(); 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));
+
+      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::string *Err) {
+  // Loop over all of the functions in the src module, mapping them over
+  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.
+      DF = Dest->getFunction(SF->getName());
+      if (DF && SF->getType() != DF->getType())
+        // If types don't agree because of opaque, try to resolve them
+        RecursiveResolveTypes(SF->getType(), DF->getType(), 
+                              &Dest->getTypeSymbolTable(), "");
+    }
+
+    // Check visibility
+    if (DF && !DF->hasInternalLinkage() &&
+        SF->getVisibility() != DF->getVisibility())
+      return Error(Err, "Linking functions named '" + SF->getName() +
+                   "': symbols have different visibilities!");
+    
+    if (DF && DF->getType() != SF->getType()) {
+      if (DF->isDeclaration() && !SF->isDeclaration()) {
+        // We have a definition of the same name but different type in the
+        // source module. Copy the prototype to the destination and replace
+        // uses of the destination's prototype with the new prototype.
+        Function *NewDF = new Function(SF->getFunctionType(), SF->getLinkage(),
+                                       SF->getName(), Dest);
+        CopyGVAttributes(NewDF, SF);
+
+        // Any uses of DF need to change to NewDF, with cast
+        DF->replaceAllUsesWith(ConstantExpr::getBitCast(NewDF, DF->getType()));
+
+        // DF will conflict with NewDF because they both had the same. We must
+        // erase this now so ForceRenaming doesn't assert because DF might
+        // not have internal linkage. 
+        DF->eraseFromParent();
+
+        // If the symbol table 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());
+
+        // Remember this mapping so uses in the source module get remapped
+        // later by RemapOperand.
+        ValueMap[SF] = NewDF;
+      } else if (SF->isDeclaration()) {
+        // We have two functions of the same name but different type and the
+        // source is a declaration while the destination is not. Any use of
+        // the source must be mapped to the destination, with a cast. 
+        ValueMap[SF] = ConstantExpr::getBitCast(DF, SF->getType());
+      } else {
+        // We have two functions of the same name but different types and they
+        // are both definitions. This is an error.
+        return Error(Err, "Function '" + DF->getName() + "' defined as both '" +
+                     ToStr(SF->getFunctionType(), Src) + "' and '" +
+                     ToStr(DF->getFunctionType(), Dest) + "'");
+      }
+    } else 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);
+      CopyGVAttributes(NewDF, SF);
+
+      // 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->isDeclaration()) {
+      // If SF is a declaration or if both SF & DF are declarations, just link 
+      // the declarations, we aren't adding anything.
+      if (SF->hasDLLImportLinkage()) {
+        if (DF->isDeclaration()) {
+          ValueMap.insert(std::make_pair(SF, DF));
+          DF->setLinkage(SF->getLinkage());          
+        }        
+      } else {
+        ValueMap.insert(std::make_pair(SF, DF));
+      }      
+    } else if (DF->isDeclaration() && !DF->hasDLLImportLinkage()) {
+      // 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
+      // *+External Weak = *
+      if ((DF->hasLinkOnceLinkage() && SF->hasWeakLinkage()) ||
+          DF->hasExternalWeakLinkage())
+        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() && !SF->hasExternalWeakLinkage())
+        // Don't inherit linkonce & external weak 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 identically 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, Function *Src,
+                             std::map<const Value*, Value*> &ValueMap,
+                             std::string *Err) {
+  assert(Src && Dest && Dest->isDeclaration() && !Src->isDeclaration());
+
+  // Go through and convert function arguments over, remembering the mapping.
+  Function::arg_iterator DI = Dest->arg_begin();
+  for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end();
+       I != E; ++I, ++DI) {
+    DI->setName(I->getName());  // Copy the name information over...
+
+    // Add a mapping to our local map
+    ValueMap.insert(std::make_pair(I, DI));
+  }
+
+  // Splice the body of the source function into the dest function.
+  Dest->getBasicBlockList().splice(Dest->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 (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)
+        if (!isa<Instruction>(*OI) && !isa<BasicBlock>(*OI))
+          *OI = RemapOperand(*OI, ValueMap);
+
+  // There is no need to map the arguments anymore.
+  for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end();
+       I != E; ++I)
+    ValueMap.erase(I);
+
+  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, 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::iterator SF = Src->begin(), E = Src->end(); SF != E; ++SF) {
+    if (!SF->isDeclaration()) {               // No body if function is external
+      Function *DF = cast<Function>(ValueMap[SF]); // Destination function
+
+      // DF not external SF external?
+      if (DF->isDeclaration())
+        // 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!");
+
+      if (G1->getAlignment() != G2->getAlignment())
+        return Error(ErrorMsg,
+         "Appending variables with different alignment need to be linked!");
+
+      if (G1->getVisibility() != G2->getVisibility())
+        return Error(ErrorMsg,
+         "Appending variables with different visibility need to be linked!");
+
+      if (G1->getSection() != G2->getSection())
+        return Error(ErrorMsg,
+         "Appending variables with different section name need to be linked!");
+      
+      unsigned NewSize = T1->getNumElements() + T2->getNumElements();
+      ArrayType *NewType = ArrayType::get(T1->getElementType(), NewSize);
+
+      G1->setName("");   // Clear G1's name in case of a conflict!
+      
+      // Create the new global variable...
+      GlobalVariable *NG =
+        new GlobalVariable(NewType, G1->isConstant(), G1->getLinkage(),
+                           /*init*/0, First->first, M, G1->isThreadLocal());
+
+      // Propagate alignment, visibility and section info.
+      CopyGVAttributes(NG, G1);
+
+      // 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::getBitCast(NG, G1->getType()));
+      G2->replaceAllUsesWith(ConstantExpr::getBitCast(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
+Linker::LinkModules(Module *Dest, Module *Src, std::string *ErrorMsg) {
+  assert(Dest != 0 && "Invalid Destination module");
+  assert(Src  != 0 && "Invalid Source Module");
+
+  if (Dest->getDataLayout().empty()) {
+    if (!Src->getDataLayout().empty()) {
+      Dest->setDataLayout(Src->getDataLayout());
+    } else {
+      std::string DataLayout;
+
+      if (Dest->getEndianness() == Module::AnyEndianness)
+        if (Src->getEndianness() == Module::BigEndian)
+          DataLayout.append("E");
+        else if (Src->getEndianness() == Module::LittleEndian)
+          DataLayout.append("e");
+      if (Dest->getPointerSize() == Module::AnyPointerSize)
+        if (Src->getPointerSize() == Module::Pointer64)
+          DataLayout.append(DataLayout.length() == 0 ? "p:64:64" : "-p:64:64");
+        else if (Src->getPointerSize() == Module::Pointer32)
+          DataLayout.append(DataLayout.length() == 0 ? "p:32:32" : "-p:32:32");
+      Dest->setDataLayout(DataLayout);
+    }
+  }
+
+  // COpy the target triple from the source to dest if the dest's is empty
+  if (Dest->getTargetTriple().empty() && !Src->getTargetTriple().empty())
+    Dest->setTargetTriple(Src->getTargetTriple());
+      
+  if (!Src->getDataLayout().empty() && !Dest->getDataLayout().empty() &&
+      Src->getDataLayout() != Dest->getDataLayout())
+    cerr << "WARNING: Linking two modules of different data layouts!\n";
+  if (!Src->getTargetTriple().empty() &&
+      Dest->getTargetTriple() != Src->getTargetTriple())
+    cerr << "WARNING: Linking two modules of different target triples!\n";
+
+  // Append the module inline asm string
+  if (!Src->getModuleInlineAsm().empty()) {
+    if (Dest->getModuleInlineAsm().empty())
+      Dest->setModuleInlineAsm(Src->getModuleInlineAsm());
+    else
+      Dest->setModuleInlineAsm(Dest->getModuleInlineAsm()+"\n"+
+                               Src->getModuleInlineAsm());
+  }
+  
+  // 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;
+  for (Module::global_iterator I = Dest->global_begin(), E = Dest->global_end();
+       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));
+  }
+
+  // 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, 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, 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 there were any alias, link them now.
+  if (LinkAlias(Dest, Src, 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.set(Src->getModuleIdentifier());
+  if (!modId.isEmpty())
+    Dest->removeLibrary(modId.getBasename());
+
+  return false;
+}
+
+// vim: sw=2
diff --git a/lib/Linker/Linker.cpp b/lib/Linker/Linker.cpp
new file mode 100644
index 0000000..9f9a59d
--- /dev/null
+++ b/lib/Linker/Linker.cpp
@@ -0,0 +1,178 @@
+//===- lib/Linker/Linker.cpp - Basic Linker functionality  ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Reid Spencer and is distributed under the
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains basic Linker functionality that all usages will need.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Linker.h"
+#include "llvm/Module.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/Config/config.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Streams.h"
+using namespace llvm;
+
+Linker::Linker(const std::string& progname, const std::string& modname, unsigned flags)
+  : Composite(0)
+  , LibPaths()
+  , Flags(flags)
+  , Error()
+  , ProgramName(progname)
+{
+  Composite = new Module(modname);
+}
+
+Linker::Linker(const std::string& progname, Module* aModule, unsigned flags)
+  : Composite(aModule)
+  , LibPaths()
+  , Flags(flags)
+  , Error()
+  , ProgramName(progname)
+{
+}
+
+Linker::~Linker() {
+  delete Composite;
+}
+
+bool
+Linker::error(const std::string& message) {
+  Error = message;
+  if (!(Flags&QuietErrors))
+    cerr << ProgramName << ": error: " << message << "\n";
+  return true;
+}
+
+bool
+Linker::warning(const std::string& message) {
+  Error = message;
+  if (!(Flags&QuietErrors))
+    cerr << ProgramName << ": warning: " << message << "\n";
+  return false;
+}
+
+void
+Linker::verbose(const std::string& message) {
+  if (Flags&Verbose)
+    cerr << "  " << message << "\n";
+}
+
+void
+Linker::addPath(const sys::Path& path) {
+  LibPaths.push_back(path);
+}
+
+void
+Linker::addPaths(const std::vector<std::string>& paths) {
+  for (unsigned i = 0; i != paths.size(); ++i) {
+    sys::Path aPath;
+    aPath.set(paths[i]);
+    LibPaths.push_back(aPath);
+  }
+}
+
+void
+Linker::addSystemPaths() {
+  sys::Path::GetBitcodeLibraryPaths(LibPaths);
+  LibPaths.insert(LibPaths.begin(),sys::Path("./"));
+}
+
+Module*
+Linker::releaseModule() {
+  Module* result = Composite;
+  LibPaths.clear();
+  Error.clear();
+  Composite = 0;
+  Flags = 0;
+  return result;
+}
+
+// LoadObject - Read in and parse the bitcode file named by FN and return the
+// module it contains (wrapped in an auto_ptr), or auto_ptr<Module>() and set
+// Error if an error occurs.
+std::auto_ptr<Module>
+Linker::LoadObject(const sys::Path &FN) {
+  std::string ParseErrorMessage;
+  Module *Result = 0;
+  
+  const std::string &FNS = FN.toString();
+  std::auto_ptr<MemoryBuffer> Buffer(
+                          MemoryBuffer::getFileOrSTDIN(&FNS[0], FNS.size()));
+  if (Buffer.get())
+    Result = ParseBitcodeFile(Buffer.get(), &ParseErrorMessage);
+  else
+    ParseErrorMessage = "Error reading file '" + FNS + "'";
+    
+  if (Result)
+    return std::auto_ptr<Module>(Result);
+  Error = "Bitcode file '" + FN.toString() + "' could not be loaded";
+  if (ParseErrorMessage.size())
+    Error += ": " + ParseErrorMessage;
+  return std::auto_ptr<Module>();
+}
+
+// IsLibrary - Determine if "Name" is a library in "Directory". Return
+// a non-empty sys::Path if its found, an empty one otherwise.
+static inline sys::Path IsLibrary(const std::string& Name,
+                                  const sys::Path& Directory) {
+
+  sys::Path FullPath(Directory);
+
+  // Try the libX.a form
+  FullPath.appendComponent("lib" + Name);
+  FullPath.appendSuffix("a");
+  if (FullPath.isArchive())
+    return FullPath;
+
+  // Try the libX.bca form
+  FullPath.eraseSuffix();
+  FullPath.appendSuffix("bca");
+  if (FullPath.isArchive())
+    return FullPath;
+
+  // Try the libX.so (or .dylib) form
+  FullPath.eraseSuffix();
+  FullPath.appendSuffix(&(LTDL_SHLIB_EXT[1]));
+  if (FullPath.isDynamicLibrary())  // Native shared library?
+    return FullPath;
+  if (FullPath.isBitcodeFile())    // .so file containing bitcode?
+    return FullPath;
+
+  // Not found .. fall through
+
+  // Indicate that the library was not found in the directory.
+  FullPath.clear();
+  return FullPath;
+}
+
+/// FindLib - Try to convert Filename into the name of a file that we can open,
+/// if it does not already name a file we can open, by first trying to open
+/// Filename, then libFilename.[suffix] for each of a set of several common
+/// library suffixes, in each of the directories in LibPaths. Returns an empty
+/// Path if no matching file can be found.
+///
+sys::Path
+Linker::FindLib(const std::string &Filename) {
+  // Determine if the pathname can be found as it stands.
+  sys::Path FilePath(Filename);
+  if (FilePath.canRead() &&
+      (FilePath.isArchive() || FilePath.isDynamicLibrary()))
+    return FilePath;
+
+  // Iterate over the directories in Paths to see if we can find the library
+  // there.
+  for (unsigned Index = 0; Index != LibPaths.size(); ++Index) {
+    sys::Path Directory(LibPaths[Index]);
+    sys::Path FullPath = IsLibrary(Filename,Directory);
+    if (!FullPath.isEmpty())
+      return FullPath;
+  }
+  return sys::Path();
+}
diff --git a/lib/Linker/Makefile b/lib/Linker/Makefile
new file mode 100644
index 0000000..efa2c35
--- /dev/null
+++ b/lib/Linker/Makefile
@@ -0,0 +1,15 @@
+##===- lib/Linker/Makefile ---------------------------------*- Makefile -*-===##
+# 
+#                     The LLVM Compiler Infrastructure
+#
+# This file was developed by Reid Spencer and is distributed under the 
+# University of Illinois Open Source License. See LICENSE.TXT for details.
+# 
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../..
+LIBRARYNAME = LLVMLinker
+BUILD_ARCHIVE := 1
+
+include $(LEVEL)/Makefile.common
+