#8763: forM_ [1..N] does not get fused (10 times slower than go function) --------------------------------------------+------------------------------ Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime performance bug | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: --------------------------------------------+------------------------------ Comment (by daniel.is.fischer): Slight correction, @Niklas, it's not a suspicion that it's the floating out of the list to the top-level and consequently the use of the list for looping instead of unboxed `Int#`s, that is direct from the core (`-ddump- simpl` is your friend in all matters related to performance). The question is under which exact circumstances GHC floats the list out. To answer that, you need somebody knowing how GHC works. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8763#comment:15 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler