patch applied (ghc): Desugar multiple polymorphic bindings more intelligently

[Simon Peyton Jones]

Thu Jun  5 05:44:23 PDT 2008  simonpj at microsoft.com
  * Desugar multiple polymorphic bindings more intelligently
  
  Occasionally people write very large recursive groups of definitions. 
  In general we desugar these to a single definition that binds tuple,
  plus lots of tuple selectors.  But that code has quadratic size, which
  can be bad.
  
  This patch adds a new case to the desugaring of bindings, for the
  situation where there are lots of polymorphic variables, but no
  dictionaries.  (Dictionaries force us into the general case.)
  
  See Note [Abstracting over tyvars only].  
  
  The extra behaviour can be disabled with the (static) flag
  
  	-fno-ds-multi-tyvar
  
  in case we want to experiment with switching it on or off.  There is
  essentially-zero effect on the nofib suite though.
  
  I was provoked into doing this by Trac #1136.  In fact I'm not sure
  it's the real cause of the problem there, but it's a good idea anyway.
  

    M ./compiler/deSugar/DsBinds.lhs -33 +135
    M ./compiler/main/StaticFlags.hs +7

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20080605124423-1287e-67d2828e0ffaaeac6b8c9cffebc1288e275f7673.gz