[PATCH] D142862: [Support] change StringMap hash function from djbHash to xxHash

[Noah Goldstein via Phabricator via cfe-commits]

goldstein.w.n added a comment.

FWIW, if the only use if hashtables `xxhash` has a slight perf bug in `XXH3_len_129to240_128b` and `XXH3_len_129to240_64b` where it will repeat the last the block if length is a factor of `32`/`16` respectively.
`XXH3_len_129to240_128b`:

- https://github.com/Cyan4973/xxHash/blob/dev/xxhash.h#L3981

`XXH3_len_129to240_64b`:

- https://github.com/Cyan4973/xxHash/blob/dev/xxhash.h#L5877

It's not fixed b.c `xxhash` needs to have a stable result for compression, but for hashtable it might be worth fixing in the internal llvm version?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D142862/new/

https://reviews.llvm.org/D142862