[X86] Add test for clflushopt intrinsic and only enable it to be selected if the feature flag is set.

llvm-svn: 294407
diff --git a/llvm/lib/Target/X86/X86Subtarget.h b/llvm/lib/Target/X86/X86Subtarget.h
index f9ae5a4..633c7ad 100644
--- a/llvm/lib/Target/X86/X86Subtarget.h
+++ b/llvm/lib/Target/X86/X86Subtarget.h
@@ -487,6 +487,7 @@
   bool hasVLX() const { return HasVLX; }
   bool hasPKU() const { return HasPKU; }
   bool hasMPX() const { return HasMPX; }
+  bool hasCLFLUSHOPT() const { return HasCLFLUSHOPT; }
 
   bool isXRaySupported() const override { return is64Bit(); }