#12847: ghci -fobject-code -O2 doesn't do the same optimisations as ghc --make -O2 -------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Other Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- From IRC: I have a module that takes around 10 seconds to compile on ghc --make -O2, but only around 3 seconds on ghci -fobject-code -O2.
bgamari: that is surprising
I've put the -v timing output of the two cases into https://gist.github.com/nh2/e9bc4732111bfe422d8e606c10f8f0ac I'm comparing the 2 files with `meld` for spotting differences easily. Check e.g. `Result size of Tidy Core` which seems to have 3x as many terms for ghc, and `Simplifier [Mymodule]` doesn't seem to run in ghci The first time terms are different is at `Desugar, the first time a factor 3 comes in is after `Specialize`.
bgamari: wow, it sounds like the simplifier isn't getting run as aggressively in GHCi
I'm running this on Ubuntu 16.04 inside nix (but happens the same way outside nix). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12847 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler