[llvm] [TableGen] Emit `llvm::is_contained` when CheckOpcode accepts a large list (PR #134057)

[Pengcheng Wang via llvm-commits]

================
@@ -152,6 +152,18 @@ void PredicateExpander::expandCheckOpcode(raw_ostream &OS,
     return;
   }
 
+  if (Opcodes.size() >= 8) {
----------------
wangpc-pp wrote:

It is determined by the estimated instruction count when the list is large: https://godbolt.org/z/3qGeWfjM9.
Yeah, I think it worths being the default behavior since `is_contained` can be inlined and unrolled for small sizes.

https://github.com/llvm/llvm-project/pull/134057