Re: [GHC] #5302: Unused arguments in join points

15 Feb 2018

      #5302: Unused arguments in join points
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        Reporter:  reinerp           |                Owner:  simonpj
            Type:  bug               |               Status:  new
        Priority:  low               |            Milestone:
       Component:  Compiler          |              Version:  7.0.3
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by osa1):

 Just tried with GHC HEAD. Late demand analysis removes unused join point
 argument.

 {{{
 let-no-escape {
   $j_s4wc [Occ=Once*!T[2], Dmd=]
     :: GHC.Prim.Int#
        -> GHC.Types.Int
        -> (# Unboxed.FingerTree
                Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z),
              Unboxed.FingerTree
                Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z) #)
   [LclId[JoinId(2)], Arity=2, Str=, Unf=OtherCon []] = ...
 }}}

 After:

 {{{
 let-no-escape {
   $w$j_s4BK [InlPrag=NOUSERINLINE[0],
              Occ=Once*!T[1],
              Dmd=]
     :: GHC.Prim.Int#
        -> (# Unboxed.FingerTree
                Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o),
              Unboxed.FingerTree
                Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o) #)
   [LclId[JoinId(1)], Arity=1, Str=, Unf=OtherCon []] = ...
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5302#comment:17
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