Index: lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
===================================================================
--- lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
+++ lib/ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
@@ -74,13 +74,6 @@
       .Default(IMAGE_FILE_MACHINE_UNKNOWN);
 }
 
-static std::string getImplibPath(StringRef Path) {
-  SmallString<128> Out = StringRef("lib");
-  Out.append(Path);
-  sys::path::replace_extension(Out, ".a");
-  return Out.str();
-}
-
 int llvm::dlltoolDriverMain(llvm::ArrayRef<const char *> ArgsArr) {
   DllOptTable Table;
   unsigned MissingIndex;
@@ -154,8 +147,6 @@
   }
 
   std::string Path = Args.getLastArgValue(OPT_l);
-  if (Path.empty())
-    Path = getImplibPath(Def->OutputFile);
 
   if (Machine == IMAGE_FILE_MACHINE_I386 && Args.getLastArg(OPT_k)) {
     for (COFFShortExport& E : Def->Exports) {
@@ -174,7 +165,8 @@
     }
   }
 
-  if (writeImportLibrary(Def->OutputFile, Path, Def->Exports, Machine, true))
-    return 1;
+  if (!Path.empty())
+    if (writeImportLibrary(Def->OutputFile, Path, Def->Exports, Machine, true))
+      return 1;
   return 0;
 }