[GHC] #14844: SpecConstr also non-recursive function

[GHC]

#14844: SpecConstr also non-recursive function
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:  SpecConstr
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by sgraf):

 I'm currently on vacation, so I'm afraid I won't be able to write much
 code.

 I'm not doing anything targeting non-recursive functions, that in itself
 should be pretty much independent. But given that you seem to have
 stumbled over the same "phase dependency" problems, here are some notes:

 Re: "anticipates the state after simplifications": That's what I figured
 out, too, and becomes much more crucial once you add lambdas, which does
 beta-reduction and makes seeing which arguments are scrutinized a little
 harder. Currently, SpecConstr only gets its `ArgOcc`s (which is a
 criterion for how deep it's worth to specialise in absence of forced
 `SPEC`) only considers the original RHS. Specialised RHS' Occs are never
 considered, although /calls/ from their RHSs are considered. My plan
 forward is to revise the fix-pointing scheme in a way that we can
 translate occurences in specialised RHSs back to occurences on the
 original RHS' arguments.

 In the case of lambdas, this also involves unification of call patterns
 with bound variables, which is rather nasty and what I've been fiddling
 with the last weeks.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14844#comment:9>
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