content: {-# OPTIONS_GHC -O2 -ddump-simpl  #-}
  module Roman where
  
  {- From: Roman Leshchinskiy [mailto:rl@cse.unsw.edu.au]
     Sent: 07 February 2008 03:34
     Subject: Quadratic SpecConstr
  
  Here is a program which makes SpecConstr generate a quadratic number of
  iterations:
  -}
  
  
  bar :: Int -> Int -> Int
  bar m n = foo n (n,n) (n,n) (n,n) (n,n)
     where
       foo :: Int -> (Int,Int) -> (Int,Int) -> (Int,Int) -> (Int,Int) -> Int
       foo n p q r s
         | n == 0    = m
         | n > 3000  = case p of { (p1,p2) -> foo (n-1) (p2,p1) q r s }
         | n > 2000  = case q of { (q1,q2) -> foo (n-1) p (q2,q1) r s }
         | n > 1000  = case r of { (r1,r2) -> foo (n-1) p q (r2,r1) s }
         | otherwise = case s of { (s1,s2) -> foo (n-1) p q r (s2,s1) }
  
  {- For this particular function, I get 14 specialisations, one for each
     possible combination of arguments.
  
     However, since we can see all the call sites outside the loop, we could
     use that to 'seed' the specialisation, and get just one specialisation.
  -}
  
  
  -- Eyeball guidance:
  --      There should be just one specialisation for foo
  --      Indeed, the original function should disappear,
  --              since it isn't used
  
  