#9630: compile-time performance regression (probably due to Generics) -------------------------------------+------------------------------------- Reporter: hvr | Owner: dfeuer Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 7.9 Resolution: | Keywords: deriving- | perf, Generics Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #9583, #10293, | Differential Rev(s): #13059, #10818 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Hmmmm... While 2b74bd9d8b4c6b20f3e8d9ada12e7db645cc3c19 seems to improve matters considerably, it doesn't fix the whole issue. ezyang's reproduction in comment:22 can be modified to make things blow up after the commit, and as far back as 7.8 at least. Specifically: * Increase the size of the definition of `T`, leaving it in the `Gen` module. * Move the definition of `tput` to a separate `GenSpec` module. This will lead to simplifier tick exhaustion. If the definition of `T` (or even just the derivation of `Generic T`) is moved to `GenSpec`, then compilation succeeds. The number of terms seems to blow up several simplifier passes after specialization. I don't yet know why, but it smells like inlining. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9630#comment:62 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler