Re: [GHC] #16086: Compile countLeadingZeros to lzcnt if -mbmi2 is set

4 Mar 2019

      #16086: Compile countLeadingZeros to lzcnt if -mbmi2 is set
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        Reporter:  ethercrow         |                Owner:  ethercrow
            Type:  feature request   |               Status:  patch
        Priority:  low               |            Milestone:
       Component:  Compiler          |              Version:  8.6.3
  (CodeGen)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Ben Gamari ):

 In [changeset:"c1d9416f2672b8d844141c0393fe773676749777/ghc"
 c1d9416f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="c1d9416f2672b8d844141c0393fe773676749777"
 Compile count{Leading,Trailing}Zeros to corresponding x86_64 instructions
 under -mbmi2

 This works similarly to existing implementation for popCount.
 Trac ticket: #16086.
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16086#comment:4
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