[GHC] #16372: GHC can't constant fold even basic power (^) applications for Int (and others?)

[GHC]

#16372: GHC can't constant fold even basic power (^) applications for Int (and
others?)
-------------------------------------+-------------------------------------
        Reporter:  Fuuzetsu          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Description changed by Fuuzetsu:

Old description:

> {{{#!hs
> [nix-shell:/tmp]$ ghc -O2 -fforce-recomp -ddump-simpl S.hs 2>&1 | tail
> [GblId,
>  Unf=Unf{Src=<vanilla>, TopLvl=True, Value=False, ConLike=False,
>          WorkFree=False, Expandable=False, Guidance=IF_ARGS [] 50 20}]
> foo
>   = case GHC.Real.$wf1 2# 1# of ww2_a2zt { __DEFAULT ->
>     GHC.Types.I# ww2_a2zt
>     }
>
> [nix-shell:/tmp]$ cat S.hs
> module S (fuck) where
> foo :: Int
> foo = (2 :: Int) ^ (1 :: Int)
> }}}
>
> This seems like a fairly strange thing to not optimise when constants are
> known on both sides. I'm complaining about Int for this particular
> ticket.

New description:

 {{{#!hs
 [nix-shell:/tmp]$ ghc -O2 -fforce-recomp -ddump-simpl S.hs 2>&1 | tail
 [GblId,
  Unf=Unf{Src=<vanilla>, TopLvl=True, Value=False, ConLike=False,
          WorkFree=False, Expandable=False, Guidance=IF_ARGS [] 50 20}]
 foo
   = case GHC.Real.$wf1 2# 1# of ww2_a2zt { __DEFAULT ->
     GHC.Types.I# ww2_a2zt
     }

 [nix-shell:/tmp]$ cat S.hs
 module S (foo) where
 foo :: Int
 foo = (2 :: Int) ^ (1 :: Int)
 }}}

 This seems like a fairly strange thing to not optimise when constants are
 known on both sides. I'm complaining about Int for this particular ticket.

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16372#comment:1>
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