[GHC] #7206: Implement cheap build

[GHC]

#7206: Implement cheap build
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                   Owner:  simonpj
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  ⊥
       Component:  Compiler          |                 Version:  7.4.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by bgamari):

 I brought up this issue again in yesterday's GHC meeting. Simon's opinion
 was that while this doesn't produce a compelling performance improve with
 existing producers, it is a tool that may be nice to have available for
 use in user code.

 I've ported these patches to `master` in my `cheap-build`
 [https://github.com/ghc/ghc/compare/master...bgamari:cheap-build?expand=1
 branch]. Sadly but not surprisingly the story told by `nofib` is still
 rather disappointing (showing only major changes),
 {{{
 --------------------------------------------------------------------------------
         Program           Size    Allocs   Runtime   Elapsed  TotalMem
 --------------------------------------------------------------------------------
       cacheprof           0.0%     +0.1%     0.173     0.173     -2.6%
         circsim           0.0%      0.0%     +3.5%     +3.6%      0.0%
     constraints           0.0%      0.0%     +1.2%     +1.2%      0.0%
    cryptarithm1           0.0%      0.0%     -0.6%     -0.4%      0.0%
    k-nucleotide           0.0%      0.0%     -1.1%     -1.1%      0.0%
        maillist           0.0%      0.0%     0.018     0.018     +5.6%
    wheel-sieve1           0.0%      0.0%     +0.7%     +0.9%      0.0%
 --------------------------------------------------------------------------------
             Min           0.0%      0.0%     -1.1%     -1.1%     -2.6%
             Max           0.0%     +0.1%     +3.5%     +3.6%     +5.6%
  Geometric Mean          -0.0%     +0.0%     +0.2%     +0.3%     +0.0%
 }}}

 I'll be looking in to this later.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7206#comment:13>
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