#14944: Compile speed regression -------------------------------------+------------------------------------- Reporter: br1 | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Thanks for this data. Several interesting things here. * There's a big jump in compilation cost between 7.8 and 7.10. (Like a factor of 2 in compiler allocation, according to comment:3. According to comment:6, the result of Specialise is much bigger in 7.10 than in 7.8. This extra code appears to be discarded at the end, but it persists through the compilation pipeline. '''Questions''': what are the extra specialisations? Do we need them? Why are they eventually discarded? Could we discard them earlier? * As you say in comment:8 it seems that GHC 8.4 has a new, and huge (temporary) blow-up in porgram size. It'd be really good to work out what this is. (You'll presumably need to cut down the program size to make this tractable.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14944#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler