[Haskell-cafe] Re: ANN: HLint 1.2

Max Bolingbroke wrote:

2009/1/12 Jan-Willem Maessen :

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On Jan 12, 2009, at 9:01 AM, Duncan Coutts wrote:

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No because the current definition are recursive and ghc cannot inline recursive functions.

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Then the map can be inlined at the call site and the 'f' inlined into the body of 'go'. This seems like exactly the sort of mechanical transformation that computers do quickly and accurately, and humans get wrong. Surely it wouldn't be that hard for GHC to transform self recursion in this way (possibly subject to the condition that the result be worth inlining)?

GHC should indeed be doing so. I'm working (on and off) to work out some suitable heuristics and put the transformation into ghc -O2. There are a few wrinkles that still need sorting out, but preliminary indications are that it decreases the runtime of our standard benchmark suite, nofib, by 12% or so.

!!! That's a surprising result - have you looked closely at the places where the transformation is having a big effect to see what's going on? Cheers, Simon