[GHC] #5615: ghc produces poor code for `div` with constant powers of 2.

[GHC]

#5615: ghc produces poor code for `div` with constant powers of 2.
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        Reporter:  Lennart           |                Owner:  akio
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.4.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:  x86
 Type of failure:  Runtime           |            Test Case:
  performance bug                    |
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2486
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"6ea62427de419ea071e1ea79ad0c15d9f4e90a67/ghc" 6ea6242/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="6ea62427de419ea071e1ea79ad0c15d9f4e90a67"
 Turn divInt# and modInt# into bitwise operations when possible

 This implements #5615 for divInt# and modInt#.

 I also included rules to do constant-folding when the both arguments
 are known.

 Test Plan: validate

 Reviewers: austin, simonmar, bgamari

 Reviewed By: bgamari

 Subscribers: hvr, thomie

 Differential Revision: https://phabricator.haskell.org/D2486

 GHC Trac Issues: #5615
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5615#comment:31>
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