Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -919,11 +919,6 @@
     else
       CmdArgs.push_back("-aarch64-global-merge=true");
   }
-
-  if (Args.hasArg(options::OPT_ffixed_x18)) {
-    CmdArgs.push_back("-backend-option");
-    CmdArgs.push_back("-aarch64-reserve-x18");
-  }
 }
 
 // Get CPU and ABI names. They are not independent
@@ -1971,6 +1966,9 @@
     else
       Features.push_back("-crc");
   }
+
+  if (Args.hasArg(options::OPT_ffixed_x18))
+    Features.push_back("+reserve-x18");
 }
 
 static void getTargetFeatures(const Driver &D, const llvm::Triple &Triple,
Index: test/Driver/aarch64-fixed-x18.c
===================================================================
--- test/Driver/aarch64-fixed-x18.c
+++ test/Driver/aarch64-fixed-x18.c
@@ -1,4 +1,4 @@
 // RUN: %clang -target aarch64-none-gnu -ffixed-x18 -### %s 2> %t
 // RUN: FileCheck --check-prefix=CHECK-FIXED-X18 < %t %s
 
-// CHECK-FIXED-X18: "-backend-option" "-aarch64-reserve-x18"
+// CHECK-FIXED-X18: "-target-feature" "+reserve-x18"