From: simonpj@microsoft.com <unknown>
Date: Thu, 6 Mar 2008 12:00:04 +0000 (+0000)
Subject: Improve SpecConstr for local bindings: seed specialisation from the calls
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=e5adcaf845207c73da65cb44cff4ef83b76dd4a9;hp=e5adcaf845207c73da65cb44cff4ef83b76dd4a9;p=ghc-hetmet.git

Improve SpecConstr for local bindings: seed specialisation from the calls

This patch makes a significant improvement to SpecConstr, based on
Roman's experience with using it for stream fusion.  The main change is
this:

  * For local (not-top-level) declarations, seed the specialisation
    loop from the calls in the body of the 'let'.

See Note [Local recursive groups] for discussion and example.  Top-level
declarations are treated just as before.

Other changes in this patch:

  * New flag -fspec-constr-count=N sets the maximum number of specialisations
    for any single function to N.  -fno-spec-constr-count removes the limit.

  * Refactoring in specLoop and friends; new algebraic data types
    OneSpec and SpecInfo instead of the tuples that were there before

  * Be less keen to specialise on variables that are simply in scope.
    Example
      f p q = letrec g a y = ...g....  in g q p
    We probably do not want to specialise 'g' for calls with exactly
    the arguments 'q' and 'p', since we know nothing about them.
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