[Libre-soc-isa] [Bug 794] SVP64 REMAP for utf8

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Wed Mar 30 15:35:04 BST 2022


--- Comment #4 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Jacob Lifshay from comment #1)
> additional useful links:
> converting utf-8 <-> utf-16 (useful for JS and Java)
> https://web.archive.org/web/20210625032530/https://researcher.watson.ibm.com/
> researcher/files/jp-INOUEHRS/IPSJPRO2008_SIMDdecoding.pdf

this will be useful to know about only that 8-16 is desirable
(which is great). trying to understand what on earth the SIMD
assembly is doing, not so much.

> validating UTF-8 (useful for JSON decoding and many many other things)
> https://github.com/rusticstuff/simdutf8

this is about as bad as it gets:

hopelessly unreadable, the level of "optimisations" is so deeply embedded
within that code that it is worse than useless!

with SVP64 being based in the abstract on "Multi-Issue parallelisation
of Scalar operations by dropping hardware for-loops around them", time and
time again it has been shown that progress is made by starting from a
*scalar* proof-of-concept, never from someone's heavily optimised SIMD

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