Inconsistent loop performance

Here are two small benchmarks:

import Criterion.Main

foo :: Int -> Int -> Int
foo n k | n <= 0    = k
        | otherwise = foo (n-1) (k+1)

bar :: Int -> Int -> Int
bar n k | n == 0    = k
        | otherwise = bar (n-1) (k+1)

main :: IO ()
main = defaultMain [ bench "foo" $ nf (uncurry foo) (20000000,0)
                   , bench "bar" $ nf (uncurry bar) (20000000,0)
                   ]

On my laptop, I consistently get a mean running time of about 36ms for foo and about 45ms for bar. This is a rather big difference. The Core looks about the same and going via C gives me about 42ms for both loops so this is certainly a code generator problem.

Trac metadata

Trac field	Value
Version	6.13
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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