We were religiously keeping exit join points throughout, which had some bad effects (#21148, #22084). This MR does two things: * Arranges that exit join points are inhibited from inlining only in /one/ Simplifier pass (right after Exitification). See Note [Be selective about not-inlining exit join points] in GHC.Core.Opt.Exitify It's not a big deal, but it shaves 0.1% off compile times. * Inline used-once non-recursive join points very aggressively Given join j x = rhs in joinrec k y = ....j x.... where this is the only occurrence of `j`, we want to inline `j`. (Unless sm_keep_exits is on.) See Note [Inline used-once non-recursive join points] in GHC.Core.Opt.Simplify.Utils This is just a tidy-up really. It doesn't change allocation, but getting rid of a binding is always good. Very effect on nofib -- some up and down.