NFC: disallow comparison of AtomicOrdering

Follow-up to D18775 and related clang change. AtomicOrdering is a lattice, 'stronger' is the right thing to do, direct comparison is fraught with peril.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265685 91177308-0d34-0410-b5e6-96231b3b80d8

Author: jfbastien

include/llvm/IR/Instructions.h

@@ -53,6 +53,11 @@ enum class AtomicOrdering {
   SequentiallyConsistent = 7
 };
 
+bool operator<(AtomicOrdering, AtomicOrdering) = delete;
+bool operator>(AtomicOrdering, AtomicOrdering) = delete;
+bool operator<=(AtomicOrdering, AtomicOrdering) = delete;
+bool operator>=(AtomicOrdering, AtomicOrdering) = delete;
+
 /// String used by LLVM IR to represent atomic ordering.
 static inline const char *toIRString(AtomicOrdering ao) {
   static const char *names[8] = {"not_atomic", "unordered", "monotonic",