Hi Gergo, Am Dienstag, dem 28.12.2021 um 15:57 +0000 schrieb Erdi, Gergo via ghc- devs:
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phew
I’m seeing ‘do’ blocks getting taking apart into top-level definitions, so e.g. main = do some complicated expression 1 some complicated expression 2 is compiled into sat_sKv = some complicated expression 1 sat_sKw = \_ -> some complicated expression 2 main = bindIO sat_sKv sat_sKw This seems to happen regardless of any common subexpressions, i.e. it is not the case that sat_sKv or sat_sKw are used anywhere else. What is the intended benefit of this floating-out? Is there a particular Core-to-Core pass that causes this? Is it possible to turn it off?
didn’t investigate deeper (maybe if you provide a small example I would), but just from looking at this: * It is generally preferable to turn local lambda expressions into top-level functions. This way, instead of dynamically allocating a FUN heap object, it’s just a static function. * sat_sKv is an IO expression? Then it is actually a function in a way (taking the “State token” as an argument). So the above applies. * I think this is the FloatOut pass. You can turn it out using -fno-full-laziness. Not sure if some others passes might do similar things, though. Cheers, Joachim -- Joachim Breitner mail@joachim-breitner.de http://www.joachim-breitner.de/