#4943: Another odd missed SpecConstr opportunity
---------------------------------+------------------------------------------
Reporter: batterseapower | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Runtime performance bug
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Comment(by batterseapower):
I *do* get that result if I disable case liberation. The issue is that it
totally fails to happen if I turn case liberation off. I don't have a
build of HEAD on this laptop, but the attached code compiles as follows
with 6.12:
{{{
Rec {
$wa_r1y9
:: forall s_aGn.
Data.Array.Base.STUArray s_aGn GHC.Types.Int GHC.Types.Int
-> GHC.Types.Int
-> GHC.Prim.Int#
-> GHC.Prim.Int#
-> GHC.Prim.State# s_aGn
-> (# GHC.Prim.State# s_aGn, () #)
[GblId, Arity=5, Caf=NoCafRefs, Str=DmdType LLLLL]
$wa_r1y9 =
\ (@ s_aGn)
(w_s1wz
:: Data.Array.Base.STUArray s_aGn GHC.Types.Int GHC.Types.Int)
(w1_s1wA :: GHC.Types.Int)
(ww_s1wD :: GHC.Prim.Int#)
(ww1_s1wH :: GHC.Prim.Int#)
(w2_s1wJ :: GHC.Prim.State# s_aGn) ->
case GHC.Prim.># ww_s1wD ww1_s1wH of _ {
GHC.Bool.False ->
case w_s1wz
of wild1_aPx
{ Data.Array.Base.STUArray ds2_aPz ds3_aPA ds4_aPB marr#_aPC ->
case GHC.Prim.readIntArray# @ s_aGn marr#_aPC ww_s1wD w2_s1wJ
of _ { (# s2#_aPK, e#_aPL #) ->
case w1_s1wA of wild11_aQm { GHC.Types.I# y_aQo ->
case GHC.Prim.writeIntArray#
@ s_aGn marr#_aPC ww_s1wD (GHC.Prim.+# e#_aPL y_aQo)
s2#_aPK
of s2#1_aQc { __DEFAULT ->
$wa_r1y9
@ s_aGn
wild1_aPx
wild11_aQm
(GHC.Prim.+# ww_s1wD 1)
ww1_s1wH
s2#1_aQc
}
}
}
};
GHC.Bool.True -> (# w2_s1wJ, GHC.Unit.() #)
}
end Rec }
}}}
This is bad. The command line was:
{{{
ghc -O2 -fno-liberate-case -ddump-simpl -c -fforce-recomp STUArray-
Rewrite2.hs
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4943#comment:2>
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