[TableGen][DecoderEmitter] Add a few DecoderTableInfo helpers (NFC)

llvm/utils/TableGen/DecoderEmitter.cpp

@@ -226,6 +226,26 @@ struct DecoderTableInfo {
   DecoderTable Table;
   PredicateSet Predicates;
   DecoderSet Decoders;
+
+  void insertPredicate(StringRef Predicate) {
+    Predicates.insert(CachedHashString(Predicate));
+  }
+
+  void insertDecoder(StringRef Decoder) {
+    Decoders.insert(CachedHashString(Decoder));
+  }
+
+  unsigned getPredicateIndex(StringRef Predicate) const {
+    auto I = find(Predicates, Predicate);
+    assert(I != Predicates.end());
+    return std::distance(Predicates.begin(), I);
+  }
+
+  unsigned getDecoderIndex(StringRef Decoder) const {
+    auto I = find(Decoders, Decoder);
+    assert(I != Decoders.end());
+    return std::distance(Decoders.begin(), I);
+  }
 };
 
 using NamespacesHwModesMap = std::map<StringRef, std::set<unsigned>>;
@@ -1090,13 +1110,8 @@ unsigned DecoderTableBuilder::getDecoderIndex(unsigned EncodingID) const {
   // performance concern, we can implement a mangling of the predicate
   // data easily enough with a map back to the actual string. That's
   // overkill for now, though.
-
-  // Make sure the predicate is in the table.
-  DecoderSet &Decoders = TableInfo.Decoders;
-  Decoders.insert(CachedHashString(Decoder));
-  // Now figure out the index for when we write out the table.
-  DecoderSet::const_iterator P = find(Decoders, Decoder.str());
-  return std::distance(Decoders.begin(), P);
+  TableInfo.insertDecoder(Decoder);
+  return TableInfo.getDecoderIndex(Decoder);
 }
 
 // If ParenIfBinOp is true, print a surrounding () if Val uses && or ||.
@@ -1154,12 +1169,8 @@ unsigned DecoderTableBuilder::getPredicateIndex(StringRef Predicate) const {
   // performance concern, we can implement a mangling of the predicate
   // data easily enough with a map back to the actual string. That's
   // overkill for now, though.
-
-  // Make sure the predicate is in the table.
-  TableInfo.Predicates.insert(CachedHashString(Predicate));
-  // Now figure out the index for when we write out the table.
-  PredicateSet::const_iterator P = find(TableInfo.Predicates, Predicate);
-  return (unsigned)(P - TableInfo.Predicates.begin());
+  TableInfo.insertPredicate(Predicate);
+  return TableInfo.getPredicateIndex(Predicate);
 }
 
 void DecoderTableBuilder::emitPredicateTableEntry(unsigned EncodingID) const {