[PATCH] D68586: Save a word in every StringSet entry

[Jordan Rose via Phabricator via llvm-commits]

jordan_rose created this revision.
jordan_rose added reviewers: mmpozulp, aaron.ballman.
Herald added subscribers: llvm-commits, dexonsmith.
Herald added a project: LLVM.

Add a specialization to StringMap (actually StringMapEntry) for a value type of NoneType (the type of llvm::None), and use it for StringSet. This'll save us a word from every entry in a StringSet, used for alignment with the size_t that stores the string length.

I could have gone all the way to some kind of empty base class optimization <https://en.cppreference.com/w/cpp/language/ebo>, but that seemed like overkill.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D68586

Files:
  llvm/include/llvm/ADT/StringMap.h
  llvm/include/llvm/ADT/StringSet.h

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