Hello, I've had a similar problem that's been fixed in 8.2.1:
https://ghc.haskell.org/trac/ghc/ticket/12603 You can also use some extreme global flags, such as ghc-options: -fexpose-all-unfoldings -fspecialise-aggressively to get most the GHC subtlety and shyness out of the way when experimenting. Good luck Mikolaj On Fri, Sep 8, 2017 at 11:21 AM, Harendra Kumar <[email protected]> wrote: > Hi, > > I have this code snippet for the bind implementation of a Monad: > > AsyncT m >>= f = AsyncT $ \_ stp yld -> > let run x = (runAsyncT x) Nothing stp yld > yield a _ Nothing = run $ f a > yield a _ (Just r) = run $ f a <> (r >>= f) > in m Nothing stp yield > > I want to have multiple versions of this implementation parameterized by a > function, like this: > > bindWith k (AsyncT m) f = AsyncT $ \_ stp yld -> > let run x = (runAsyncT x) Nothing stp yld > yield a _ Nothing = run $ f a > yield a _ (Just r) = run $ f a `k` (bindWith k r f) > in m Nothing stp yield > > And then the bind function becomes: > > (>>=) = bindWith (<>) > > But this leads to a performance degradation of more than 10%. inlining does > not help, I tried INLINE pragma as well as the "inline" GHC builtin. I > thought this should be a more or less straightforward replacement making the > second version equivalent to the first one. But apparently there is > something going on here that makes it perform worse. > > I did not look at the core, stg or asm yet. Hoping someone can quickly > comment on it. Any ideas why is it so? Can this be worked around somehow? > > Thanks, > Harendra > > _______________________________________________ > ghc-devs mailing list > [email protected] > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > _______________________________________________ ghc-devs mailing list [email protected] http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
