[ThinLTO] Helper for performing renaming/promotion on a module

Creates a module and performs necessary renaming/promotion of locals
that may be exported to another module.

Split out of D15024.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254802 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Linker/Linker.h

@@ -99,6 +99,13 @@ private:
   DiagnosticHandlerFunction DiagnosticHandler;
 };
 
+/// Create a new module with exported local functions renamed and promoted
+/// for ThinLTO.
+std::unique_ptr<Module>
+renameModuleForThinLTO(std::unique_ptr<Module> &M,
+                       const FunctionInfoIndex *Index,
+                       DiagnosticHandlerFunction DiagnosticHandler);
+
 } // End llvm namespace
 
 #endif

lib/Linker/LinkModules.cpp

@@ -2056,6 +2056,18 @@ bool Linker::linkModules(Module &Dest, Module &Src,
   return L.linkInModule(Src, Flags);
 }
 
+std::unique_ptr<Module>
+llvm::renameModuleForThinLTO(std::unique_ptr<Module> &M,
+                             const FunctionInfoIndex *Index,
+                             DiagnosticHandlerFunction DiagnosticHandler) {
+  std::unique_ptr<llvm::Module> RenamedModule(
+      new llvm::Module(M->getModuleIdentifier(), M->getContext()));
+  Linker L(*RenamedModule.get(), DiagnosticHandler);
+  if (L.linkInModule(*M.get(), llvm::Linker::Flags::None, Index))
+    return nullptr;
+  return RenamedModule;
+}
+
 //===----------------------------------------------------------------------===//
 // C API.
 //===----------------------------------------------------------------------===//