[clang] [CIR] Upstream ThreeWayCmpOp (PR #169963)

[Hendrik Hübner via cfe-commits]

================
@@ -447,6 +447,68 @@ def CIR_ConstPtrAttr : CIR_Attr<"ConstPtr", "ptr", [TypedAttrInterface]> {
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// CmpThreeWayInfoAttr
+//===----------------------------------------------------------------------===//
+
+def CIR_CmpOrdering : CIR_I32EnumAttr<
+  "CmpOrdering", "three-way comparison ordering kind", [
+    I32EnumAttrCase<"Strong", 0, "strong">,
----------------
HendrikHuebner wrote:

I just realized the built in three way comparison operator never actually returns a weak ordering, only overloading it makes that possible. Should we still keep the weak case?

https://github.com/llvm/llvm-project/pull/169963