[GHC] #15250: Add support for _mm512_shuffle_epi8 intrinsic

[GHC]

#15250: Add support for _mm512_shuffle_epi8 intrinsic
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        Reporter:  newhoggy          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by carter):

 repeating my remark from phab:

 hrmmm, i suspect the AVX512 stuff may not be terrible performant / some /
 many intel CPUS in consumer / dev machine hands wont support them, have
 you tested using it via C FFI for your inner loops first?

 This is definitely an example of an instruction where the shuffle data can
 be at runtime, i'd suggest first making sure an inner loop / subroutine in
 C has satisfactory perf first. Whats the context driving this effort?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15250#comment:2>
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