#11735: Optimize coercionKind -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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): There are a number of different things going on. 1. comment:5 gets rid of a non-linearity in `coercionKind` for the `ForallCo` case. This is a big win. We definitely want it. 2. The same non-linearity is present in `coercionKindRole` so I suggested getting rid of the duplication between the two. That seems possible by caching the role in `NthCo`. Doing so doesn't solve any known performance problems, but seems to be nicer code. 3. We have a clear problem in `simplCast`, which comes from transforming {{{ (f |> co) @t1 @t2 ... @tn ===> ((f @t1') |> co1) @t2 ... @tn ===> (etc) (f @t1' @t2' ... @tn') |> con }}} Doing these steps one at a time gives clearly non-linear behaviour. Hence comment:10. I think comment:41 is in this territory. I think it'd be helpful to separate these issues, possibly into separate tickets. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11735#comment:48 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler