diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index 78cbf3efd2b..e7183eb4bb2 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -374,7 +374,7 @@ static void CopyGVAttributes(GlobalValue *DestGV, const GlobalValue *SrcGV) {
 /// 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,
+static bool GetLinkageResult(GlobalValue *Dest, const GlobalValue *Src,
                              GlobalValue::LinkageTypes &LT, bool &LinkFromSrc,
                              std::string *Err) {
   assert((!Dest || !Src->hasInternalLinkage()) &&
@@ -454,14 +454,14 @@ static bool GetLinkageResult(GlobalValue *Dest, GlobalValue *Src,
 
 // LinkGlobals - Loop through the global variables in the src module and merge
 // them into the dest module.
-static bool LinkGlobals(Module *Dest, Module *Src,
+static bool LinkGlobals(Module *Dest, const 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();
+  for (Module::const_global_iterator I = Src->global_begin(), E = Src->global_end();
        I != E; ++I) {
-    GlobalVariable *SGV = I;
+    const GlobalVariable *SGV = I;
     GlobalVariable *DGV = 0;
     // Check to see if may have to link the global.
     if (SGV->hasName() && !SGV->hasInternalLinkage()) {
@@ -528,42 +528,53 @@ static bool LinkGlobals(Module *Dest, Module *Src,
       AppendingVars.insert(std::make_pair(SGV->getName(), NewDGV));
     } else {
       // Otherwise, perform the mapping as instructed by GetLinkageResult.
-
-      // Propagate alignment, section, and visibility info.
-      CopyGVAttributes(DGV, SGV);
-
-      // 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());
-        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) {
+        // Propagate alignment, section, and visibility info.
+        CopyGVAttributes(DGV, SGV);
+
+        // 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()) {
+          GlobalVariable *NewDGV =
+            new GlobalVariable(SGV->getType()->getElementType(),
+                               DGV->isConstant(), DGV->getLinkage(),
+                               /*init*/0, DGV->getName(), Dest);
+          CopyGVAttributes(NewDGV, DGV);
+          DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewDGV,
+                                                           DGV->getType()));
+          // DGV will conflict with NewDGV because they both had the same
+          // name. We must erase this now so ForceRenaming doesn't assert
+          // because DGV might not have internal linkage.
+          DGV->eraseFromParent();
+
+          // If the symbol table 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());
+
+          DGV = NewDGV;
+        }
+
         // Inherit const as appropriate
         DGV->setConstant(SGV->isConstant());
+
+        // Set initializer to zero, so we can link the stuff later
         DGV->setInitializer(0);
       } else {
-        if (SGV->isConstant() && !DGV->isConstant()) {
-          if (DGV->isDeclaration())
-            DGV->setConstant(true);
-        }
-        SGV->setLinkage(GlobalValue::ExternalLinkage);
-        SGV->setInitializer(0);
+        // Special case for const propagation
+        if (DGV->isDeclaration() && SGV->isConstant() && !DGV->isConstant())
+          DGV->setConstant(true);
       }
 
-      ValueMap.insert(
-        std::make_pair(SGV, ConstantExpr::getBitCast(DGV, SGV->getType())));
+      // Set calculated linkage
+      DGV->setLinkage(NewLinkage);
+
+      // Make sure to remember this mapping...
+      ValueMap.insert(std::make_pair(SGV,
+                                     ConstantExpr::getBitCast(DGV,
+                                                              SGV->getType())));
     }
   }
   return false;