Re: [GHC] #5642: Deriving Generic of a big type takes a long time and lots of space

#5642: Deriving Generic of a big type takes a long time and lots of space -------------------------------------+------------------------------------- Reporter: basvandijk | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.3 Resolution: | Keywords: deriving- | perf, Generics Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: T5642 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2304 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ryan Scott ): In [changeset:"34010dbe77ac405da6c671c3feb3573d0d025379/ghc" 34010db/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="34010dbe77ac405da6c671c3feb3573d0d025379" Derive the Generic instance in perf/compiler/T5642 Summary: For some inexplicable reason, the `Generic` instance in `perf/compiler/T5642` is written out entirely by hand. This is not only strange, since Trac #5642 is about derived `Generic` instances, but it also annoying to maintain, since it requires manually changing a bunch of code whenever the algorithm behind `deriving Generic` changes. (See D2304 for a recent example of this.) It seems more sensible to just derive the `Generic` instance. It shifts the goalposts of what allocations we're measuring a bit, since we no longer have to parse a large amount of code (and as a knock-on effect, the allocations go down a bit). But I think this program is morally equivalent to what we were benchmarking before, so it's not too unreasonable to change. Test Plan: make test TEST=T5642 Reviewers: austin, thomie, bgamari Reviewed By: bgamari Differential Revision: https://phabricator.haskell.org/D2511 GHC Trac Issues: #5642 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5642#comment:48 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler