[XRay][compiler-rt] Disable XRay instrumentation of the XRay runtime.

Summary:
Adds a CMake check for whether the compiler used to build the XRay
library supports XRay-instrumentation. If the compiler we're using does
support the `-fxray-instrument` flag (i.e. recently-built Clang), we
define the XRAY_NEVER_INSTRUMENT macro that then makes sure that the
XRay runtime functions never get XRay-instrumented.

This prevents potential weirdness involved with building the XRay
library with a Clang that supports XRay-instrumentation, and is
attempting to XRay-instrument the build of compiler-rt.

Reviewers: majnemer, rSerge, echristo

Subscribers: mehdi_amini, llvm-commits, mgorny

Differential Revision: https://reviews.llvm.org/D26597

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@287068 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 3 deletions

diff --git a/lib/xray/xray_flags.cc b/lib/xray/xray_flags.cc
index 6f829128c..338c2378b 100644
--- a/lib/xray/xray_flags.cc
+++ b/lib/xray/xray_flags.cc
@@ -16,6 +16,7 @@
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_flag_parser.h"
 #include "sanitizer_common/sanitizer_libc.h"
+#include "xray_defs.h"
 
 using namespace __sanitizer;
 
@@ -23,20 +24,20 @@ namespace __xray {
 
 Flags xray_flags_dont_use_directly; // use via flags().
 
-void Flags::SetDefaults() {
+void Flags::SetDefaults() XRAY_NEVER_INSTRUMENT {
 #define XRAY_FLAG(Type, Name, DefaultValue, Description) Name = DefaultValue;
 #include "xray_flags.inc"
 #undef XRAY_FLAG
 }
 
-static void RegisterXRayFlags(FlagParser *P, Flags *F) {
+static void RegisterXRayFlags(FlagParser *P, Flags *F) XRAY_NEVER_INSTRUMENT {
 #define XRAY_FLAG(Type, Name, DefaultValue, Description)                       \
   RegisterFlag(P, #Name, Description, &F->Name);
 #include "xray_flags.inc"
 #undef XRAY_FLAG
 }
 
-void InitializeFlags() {
+void InitializeFlags() XRAY_NEVER_INSTRUMENT {
   SetCommonFlagsDefaults();
   auto *F = flags();
   F->SetDefaults();