[GHC] #2070: Record field selectors are not optimized

[GHC]

#2070: Record field selectors are not optimized
------------------------+---------------------------------------------------
    Reporter:  twanvl   |       Owner:          
        Type:  bug      |      Status:  new     
    Priority:  normal   |   Component:  Compiler
     Version:  6.9      |    Severity:  normal  
    Keywords:           |    Testcase:          
Architecture:  Unknown  |          Os:  Unknown 
------------------------+---------------------------------------------------
 It seems that record field selectors are not optimized. Usually this
 doesn't matter, but when there are unpacked fields this leaves suboptimal
 code. The equivalent code using the data type constructor ''is''
 optimized.

 For example:
 {{{
 module Test where

 data Test = Test { getR :: {-# UNPACK #-} !Int }
 getC (Test a) = a
 }}}

 Generates the following core (with -O2 -ddump-simpl):

 {{{
 Test.getR :: Test.Test -> GHC.Base.Int
 [RecSel]
 [Arity 1
  NoCafRefs
  Str: DmdType U(L)m]
 Test.getR =
   \ (tpl_B1 :: Test.Test) ->
     case tpl_B1 of tpl1_B2 { Test.Test rb_B4 ->
     let {
       ipv_B3 [Just S] :: GHC.Base.Int
       [Str: DmdType m]
       ipv_B3 = GHC.Base.I# rb_B4
     } in  ipv_B3
     }

 Test.getC :: Test.Test -> GHC.Base.Int
 [GlobalId]
 [Arity 1
  NoCafRefs
  Str: DmdType U(L)m]
 Test.getC =
   \ (ds_d5Q :: Test.Test) ->
     case ds_d5Q of wild_B1 { Test.Test rb_d5S -> GHC.Base.I# rb_d5S }
 }}}

 After further investigation, it seems that `getR` is not passed through
 the optimizer at all, earlier simplifier passes (-ddump-simpl-iterations,
 -ddump-cse, -ddump-occur-anal) do not include the function.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2070>
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