ADT: add a helper to check if the Triple is ARM64

Add a trivial helper for checking if the architecture is AArch64 Little
Endian or Big Endian.

llvm-svn: 316837

llvm/include/llvm/ADT/Triple.h

@@ -655,6 +655,11 @@ public:
     return getArch() == Triple::arm || getArch() == Triple::armeb;
   }
 
+  /// Tests whether the target is AArch64 (little and big endian).
+  bool isAArch64() const {
+    return getArch() == Triple::aarch64 || getArch() == Triple::aarch64_be;
+  }
+
   /// Tests wether the target supports comdat
   bool supportsCOMDAT() const { return !isOSBinFormatMachO(); }