#13996: Non-cheap primop is duplicated -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by mboes):
better to push it inside the inner lambda, so the two lambdas come together (generally a big win).
Note in particular that `-fno-lambda-eta-expansion` can be a huge pessimization in the following way. Consider this program: {{{#!hs module Main where f :: Double -> Double -> Double f t = let s = sin t in \x -> x + s main = do print $ sum [ f t x | t <- [1..10000], x <- [1..10000]] }}} `ghc --make -O2` yields a program that runs in constant space. Whereas adding `-fno-do-lambda-eta-expansion` to the command-line yields a program that segfaults, because its memory consumption blew up and it ultimately ran out of space. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13996#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler