#5767: Integer inefficiencies
--------------------------------------+-------------------------------------
Reporter: rl | Owner: igloo
Type: bug | Status: new
Priority: highest | Milestone: 7.4.1
Component: Compiler | Version: 7.5
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Runtime performance bug | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: | Related:
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Comment(by rl):
I finally found a small test case for the missing
`integerToInt/smallInteger` rule:
{{{
foo :: (Integral a, Num a) => a -> a
{-# INLINE foo #-}
foo x = fromIntegral x
bar :: Int -> Int
bar x = foo x
}}}
The head generates this:
{{{
foo_$sfoo =
\ (eta_B1 :: Int) ->
case eta_B1 of _ { I# i_ara ->
case integerToInt (smallInteger i_ara) of wild1_ard { __DEFAULT ->
I# wild1_ard
}
}
bar = foo_$sfoo
}}}
Whereas 7.2.2 generates this:
{{{
bar_$sfoo = \ (eta_B1 :: Int) -> eta_B1
bar = bar_$sfoo
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5767#comment:6>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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