[X86] Add -mclflushopt/-mno-clflushopt command line support and __CLFLUSHOPT__ define to match gcc.

llvm-svn: 294411
diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 851d3f6..c0473a5 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -3881,6 +3881,8 @@
     Builder.defineMacro("__PKU__");
   if (HasCX16)
     Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_16");
+  if (HasCLFLUSHOPT)
+    Builder.defineMacro("__CLFLUSHOPT__");
 
   // Each case falls through to the previous one here.
   switch (SSELevel) {