[GHC] #7116: Missing optimisation: strength reduction of floating-point multiplication

[GHC]

#7116: Missing optimisation: strength reduction of floating-point multiplication
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        Reporter:  simonmar                 |            Owner:
            Type:  bug                      |           Status:  patch
        Priority:  normal                   |        Milestone:  7.8.1
       Component:  Compiler                 |          Version:  7.4.2
      Resolution:                           |         Keywords:
Operating System:  Unknown/Multiple         |     Architecture:
 Type of failure:  Runtime performance bug  |  Unknown/Multiple
       Test Case:                           |       Difficulty:  Unknown
        Blocking:                           |       Blocked By:
                                            |  Related Tickets:
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Comment (by simonmar):

 jstolarek: the ticket is about doing the optimisation for floating-point
 multiplication, not integer.  We don't want to do it for integer
 operations, because it's better to do this in the code generator (the only
 reason for doing it in the simplifier would be to enable further
 simplifications, but that isn't the case here).

 Furthermore, we definitely want to optimise integer multiplication at the
 Cmm level, because the Stg->Cmm code generator and later stages may create
 opportunities for this optimisation.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7116#comment:7>
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