Add CachedHashStringRef::data().

[ruiu]

Summary

This accessor is useful and could be slightly more efficient than
Str.val().data() because you can avoid StringRef instantiation.

[grimar]

I have no objections. It already has size() getter, it is consistent to have data(). LGTM.

llvm/include/llvm/ADT/CachedHashString.h

explicit CachedHashStringRef(StringRef S)
       : CachedHashStringRef(S, DenseMapInfo<StringRef>::getHashValue(S)) {}
 
   CachedHashStringRef(StringRef S, uint32_t Hash)
       : P(S.data()), Size(S.size()), Hash(Hash) {
     assert(S.size() <= std::numeric_limits<uint32_t>::max());
   }
 
   StringRef val() const { return StringRef(P, Size); }
+  const char *data() const { return P; }
   uint32_t size() const { return Size; }
   uint32_t hash() const { return Hash; }
 };
 
 template <> struct DenseMapInfo<CachedHashStringRef> {
   static CachedHashStringRef getEmptyKey() {
     return CachedHashStringRef(DenseMapInfo<StringRef>::getEmptyKey(), 0);
   }