[GHC] #13282: Introduce fast path through simplifier for static bindings

[GHC]

#13282: Introduce fast path through simplifier for static bindings
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      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:                    |
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Comment (by rwbarton):

 > Here we will consider a top-level binding to be "static" if its RHS
 consists of a data constructor applied to zero or more other static
 bindings.

 Minor amendments:

 - I think you only intend to allow ''saturated'' data constructor
 applications; though I'm not sure.

 - Literals should also be considered static.

 - What about type applications of polymorphic data constructors to type
 variables? E.g.

   {{{#!hs
   a :: [Maybe a]
   a = [Nothing]
   }}}

   desugars to

   {{{#!hs
   a :: forall a. [Maybe a]
   a = \ (@ a1) -> : @ (Maybe a1) (Nothing @ a1) ([] @ (Maybe a1))
   }}}

   and it's static in the sense that it will be represented by static
 closures; but at the Core level, it involves a type variable `a1`. Do you
 consider this "static" in your sense?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13282#comment:2>
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