[llvm] [TableGen] DecoderEmitter clean-ups and modernization. (PR #84832)

[James Y Knight via llvm-commits]

================
@@ -1760,14 +1759,14 @@ bool FilterChooser::filterProcessor(bool AllowMixed, bool Greedy) {
   bool AllUseless = true;
   unsigned BestScore = 0;
 
-  for (unsigned i = 0, e = Filters.size(); i != e; ++i) {
-    unsigned Usefulness = Filters[i].usefulness();
+  for (const auto &[I, TFilter] : enumerate(Filters)) {
----------------
jyknight wrote:

Maybe use "Idx" instead of "I".
What's the "T" in "TFilter" mean?

https://github.com/llvm/llvm-project/pull/84832