[GHC] #9340: Implement new `clz` inline primop

[GHC]

#9340: Implement new `clz` inline primop
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              Reporter:  hvr         |            Owner:  hvr
                  Type:  feature     |           Status:  patch
  request                            |        Milestone:  7.10.1
              Priority:  normal      |          Version:  7.8.2
             Component:  Compiler    |         Keywords:  primop clz
  (CodeGen)                          |     Architecture:  Unknown/Multiple
            Resolution:              |       Difficulty:  Unknown
      Operating System:              |       Blocked By:
  Unknown/Multiple                   |  Related Tickets:
       Type of failure:              |
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D144   |
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Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"3669b60cb0b24e22563bfe624aab4aba369cbfca/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="3669b60cb0b24e22563bfe624aab4aba369cbfca"
 Add bit scan {forward,reverse} insns to x86 NCG

 This is a pre-requisite for implementing count-{leading,trailing}-zero
 prim-ops (re #9340)

 Reviewers: ezyang, rwbarton, simonmar, austin

 Subscribers: simonmar, relrod, ezyang, carter

 Differential Revision: https://phabricator.haskell.org/D141
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9340#comment:4>
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