The flattener is very slow
The flattener (part of the constraint solver) can be very slow. Tests perf/compiler/T9872a
and b,c,d, demonstrate this.
A lot of time is spent in GHC.Tc.Solver.Flatten.flatten_args_slow
, and thence in GHC.Core.Coercion.simplifyArgsWorker
. I think the latter is where all the time is spent.
This ticket is just to remind us of the problem, and provide us a place to discuss solutions.
- !3548 (closed): tweaks in Coercion
- !3763 (closed): more tweaks in Coercion