#4431: SpecConstr doesn't specialise
---------------------------------+------------------------------------------
Reporter: rl | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.1 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Runtime performance bug
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Compile this with `-O2 -fno-spec-constr-count`:
{{{
foo :: Int -> Int -> Bool
foo n x = loop 0 False (Just x)
where
loop i b x | i > n = b
loop i False x = loop (i+1) True x
loop i True (Just x) = loop (i+1) False Nothing
loop i True Nothing = loop (i+1) True (Just x)
}}}
!SpecConstr produces a loop of type `Maybe Int -> Int# -> Bool`, i.e., it
doesn't specialise for the `Maybe` argument for some reason.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4431>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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