Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -4804,7 +4804,16 @@
 
   if (Args.hasFlag(options::OPT_fxray_instrument,
                    options::OPT_fnoxray_instrument, false)) {
-    CmdArgs.push_back("-fxray-instrument");
+    const std::string XRayInstrumentOption("-fxray-instrument");
+    if (Triple.getOS() == llvm::Triple::Linux &&
+        (Triple.getArch() == llvm::Triple::arm ||
+         Triple.getArch() == llvm::Triple::x86_64)) {
+      // Supported.
+    } else {
+      D.Diag(diag::err_drv_clang_unsupported) << (XRayInstrumentOption + " on "
+        + Triple.str());
+    }
+    CmdArgs.push_back(XRayInstrumentOption.c_str());
     if (const Arg *A =
             Args.getLastArg(options::OPT_fxray_instruction_threshold_,
                             options::OPT_fxray_instruction_threshold_EQ)) {