Change ModuleLinker to take a set of GlobalValues to import instead of a single one

For efficiency reason, when importing multiple functions for the same Module,
we can avoid reparsing it every time.

Differential Revision: http://reviews.llvm.org/D15102

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 254486

llvm/tools/llvm-link/llvm-link.cpp

@@ -198,7 +198,10 @@ static bool importFunctions(const char *argv0, LLVMContext &Context,
     }
 
     // Link in the specified function.
-    if (L.linkInModule(*M, Linker::Flags::None, Index.get(), F))
+    DenseSet<const GlobalValue *> FunctionToImport;
+    FunctionToImport.insert(F);
+    if (L.linkInModule(*M, Linker::Flags::None, Index.get(),
+                       &FunctionToImport))
       return false;
   }
   return true;