Index: include/clang/Basic/Features.def
===================================================================
--- include/clang/Basic/Features.def
+++ include/clang/Basic/Features.def
@@ -37,6 +37,7 @@
 FEATURE(hwaddress_sanitizer,
         LangOpts.Sanitize.hasOneOf(SanitizerKind::HWAddress |
                                    SanitizerKind::KernelHWAddress))
+FEATURE(xray_instrument, LangOpts.XRayInstrument)
 FEATURE(assume_nonnull, true)
 FEATURE(attribute_analyzer_noreturn, true)
 FEATURE(attribute_availability, true)
Index: test/Lexer/has_feature_xray_instrument.cpp
===================================================================
--- test/Lexer/has_feature_xray_instrument.cpp
+++ test/Lexer/has_feature_xray_instrument.cpp
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -E -fxray-instrument %s -o - | FileCheck --check-prefix=CHECK-XRAY %s
+// RUN: %clang_cc1 -E  %s -o - | FileCheck --check-prefix=CHECK-NO-XRAY %s
+
+#if __has_feature(xray_instrument)
+int XRayInstrumentEnabled();
+#else
+int XRayInstrumentDisabled();
+#endif
+
+// CHECK-XRAY: XRayInstrumentEnabled
+// CHECK-NO-XRAY: XRayInstrumentDisabled