#4448: Another case of SpecConstr not specialising
---------------------------------+------------------------------------------
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 with -O2 -fno-spec-constr-count -fno-spec-constr-threshold:
{{{
foo :: Int -> Int -> Int -> (Int,Int)
foo !a !b !c = loop (Left (a,b))
where
loop :: Either (Int,Int) (Int, (Int,Int)) -> (Int,Int)
loop (Left (!x,!n))
| n > 0 = loop (Right (x,(x+c,n-1)))
| otherwise = (x,n)
loop (Right (i,t))
| i < c = loop (Right (i+1,t))
| otherwise = loop (Left t)
}}}
!SpecConstr doesn't specialise for the `(Int,Int)` pair. Unless I'm
mistaken, the !SpecConstr loop should get this since the call in `foo` has
the form `Left (I# x, I# y)` and the pair then gets threaded through the
loop.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4448>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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