Index: compiler-rt/trunk/lib/xray/xray_AArch64.cc
===================================================================
--- compiler-rt/trunk/lib/xray/xray_AArch64.cc
+++ compiler-rt/trunk/lib/xray/xray_AArch64.cc
@@ -120,4 +120,7 @@
   return patchSled(Enable, FuncId, Sled, __xray_FunctionTailExit);
 }
 
+// FIXME: Maybe implement this better?
+bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
+
 } // namespace __xray
Index: compiler-rt/trunk/lib/xray/xray_arm.cc
===================================================================
--- compiler-rt/trunk/lib/xray/xray_arm.cc
+++ compiler-rt/trunk/lib/xray/xray_arm.cc
@@ -156,4 +156,7 @@
   return patchSled(Enable, FuncId, Sled, __xray_FunctionTailExit);
 }
 
+// FIXME: Maybe implement this better?
+bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
+
 } // namespace __xray
Index: compiler-rt/trunk/lib/xray/xray_emulate_tsc.h
===================================================================
--- compiler-rt/trunk/lib/xray/xray_emulate_tsc.h
+++ compiler-rt/trunk/lib/xray/xray_emulate_tsc.h
@@ -35,6 +35,9 @@
   CPU = 0;
   return TS.tv_sec * NanosecondsPerSecond + TS.tv_nsec;
 }
-}
+
+bool probeRequiredCPUFeatures();
+
+} // namespace __xray
 
 #endif // XRAY_EMULATE_TSC_H
Index: compiler-rt/trunk/lib/xray/xray_inmemory_log.cc
===================================================================
--- compiler-rt/trunk/lib/xray/xray_inmemory_log.cc
+++ compiler-rt/trunk/lib/xray/xray_inmemory_log.cc
@@ -138,6 +138,11 @@
 }
 
 static auto Unused = [] {
+  if (!probeRequiredCPUFeatures()) {
+    Report("Required CPU features missing for XRay instrumentation, not "
+           "installing instrumentation hooks.\n");
+    return false;
+  }
   if (flags()->xray_naive_log)
     __xray_set_handler(__xray_InMemoryRawLog);
   return true;
Index: compiler-rt/trunk/lib/xray/xray_x86_64.h
===================================================================
--- compiler-rt/trunk/lib/xray/xray_x86_64.h
+++ compiler-rt/trunk/lib/xray/xray_x86_64.h
@@ -27,6 +27,9 @@
   CPU = LongCPU;
   return TSC;
 }
+
+bool probeRequiredCPUFeatures();
+
 } // namespace __xray
 
 #endif // XRAY_X86_64_H
Index: compiler-rt/trunk/lib/xray/xray_x86_64.cc
===================================================================
--- compiler-rt/trunk/lib/xray/xray_x86_64.cc
+++ compiler-rt/trunk/lib/xray/xray_x86_64.cc
@@ -1,6 +1,8 @@
+#include "cpuid.h"
 #include "sanitizer_common/sanitizer_common.h"
 #include "xray_defs.h"
 #include "xray_interface_internal.h"
+
 #include <atomic>
 #include <cstdint>
 #include <errno.h>
@@ -61,8 +63,8 @@
                         &CPUFrequency)) {
     CPUFrequency *= 1000;
   } else if (readValueFromFile(
-      "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq",
-      &CPUFrequency)) {
+                 "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq",
+                 &CPUFrequency)) {
     CPUFrequency *= 1000;
   } else {
     Report("Unable to determine CPU frequency for TSC accounting.\n");
@@ -199,4 +201,20 @@
   return true;
 }
 
+// We determine whether the CPU we're running on has the correct features we
+// need. In x86_64 this will be rdtscp support.
+bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT {
+  unsigned int EAX, EBX, ECX, EDX;
+
+  // We check whether rdtscp support is enabled. According to the x86_64 manual,
+  // level should be set at 0x80000001, and we should have a look at bit 27 in
+  // EDX. That's 0x8000000 (or 1u << 26).
+  __get_cpuid(0x80000001, &EAX, &EBX, &ECX, &EDX);
+  if (!(EDX & (1u << 26))) {
+    Report("Missing rdtscp support.\n");
+    return false;
+  }
+  return true;
+}
+
 } // namespace __xray