patch applied (ghc): Optimise the %.hi : %.o rule

[Simon Marlow]

Tue Jun 23 05:49:01 PDT 2009  Simon Marlow <marlowsd at gmail.com>
  * Optimise the %.hi : %.o rule
  Ignore-this: 4c467d6b7ae90243429951a4f54ff027
  Previously this rule had a sanity check for the existence of the .o
  file.  However, the sanity check is expensive, especially on Windows,
  because it requires spawning a shell.  So now we use an empty command
  here.
  
  This change reduced the time to do 'make' in an up-to-date tree on
  Windows from 33s to 16s for me.  (the actual saving depends on how
  much rebuilding you've been doing, and how many .hi files are older
  than their .o files).
  
  The comments in this file now describe various versions of the rule
  that don't work.

    M ./rules/hi-rule.mk -16 +53

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20090623124901-12142-6de2ece06f281dd3f5d6961213406743bdb499eb.gz