• simonpj@microsoft.com's avatar
    Refactor case-merging and identical-alternative optimisations · 367e603d
    simonpj@microsoft.com authored
    These two optimisations were originally done by SimplUtils.mkCase
    *after* all the pieces have been simplified.  Some while ago I
    moved them *before*, so they were done by SimplUtils.prepareAlts.
    It think the reason was that I couldn't rely on the dead-binder 
    information on OutIds, and that info is useful in these optimisations.
    
    However, 
     (a) Other changes (notably moving case-binder-swap to OccurAnal)
         have meant that dead-binder information is accurate in 
         OutIds
    
     (b) When there is a cascade of case-merges, they happen in 
         one sweep if you do it after, but in many sweeps if you
         do it before.  Reason: doing it after means you are looking
         at nice simplified Core.
    367e603d
Simplify.lhs 89.2 KB