Driver: Improve -Xarch argument diagnostics a bit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129918 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index 02105ac..75cb935 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -555,9 +555,16 @@
       // driver behavior; that isn't going to work in our model. We
       // use isDriverOption() as an approximation, although things
       // like -O4 are going to slip through.
-      if (!XarchArg || Index > Prev + 1 ||
-          XarchArg->getOption().isDriverOption()) {
-       getDriver().Diag(clang::diag::err_drv_invalid_Xarch_argument)
+      if (!XarchArg) {
+        getDriver().Diag(clang::diag::err_drv_invalid_Xarch_argument_unknown)
+          << A->getAsString(Args);
+        continue;
+      } else if (Index > Prev + 1) {
+        getDriver().Diag(clang::diag::err_drv_invalid_Xarch_argument_with_args)
+          << A->getAsString(Args);
+        continue;
+      } else if (XarchArg->getOption().isDriverOption()) {
+        getDriver().Diag(clang::diag::err_drv_invalid_Xarch_argument_isdriver)
           << A->getAsString(Args);
         continue;
       }