[GHC] #9927: Should simplifier try more iterations?

[GHC]

#9927: Should simplifier try more iterations?
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       Reporter:  goldfire           |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Compiler           |                 Version:  7.11
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:
     Blocked By:                     |  None/Unknown
Related Tickets:                     |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
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 When compiling with the `devel1` build, we get debugging output while
 building libraries. I see a lot of warnings like this:

 {{{
 WARNING: file compiler/simplCore/SimplCore.hs, line 592
   Simplifier bailing out after 4 iterations [5024, 247, 22, 1]
     Size = {terms: 3,735, types: 3,028, coercions: 216}
 }}}

 It looks to me like the simplifier is doing quite a nice job and shouldn't
 give up so soon.

 Concretely, I propose: increase the cutoff and see what the effect is on
 timing of running the entire GHC build, at whatever settings a performance
 guru thinks appropriate (almost certainly ''not'' `devel1`!). Ideally, the
 testing would take place on ghcspeed, so that it's a controlled
 environment and can be compared nicely with historical performance.

 I have not carried out this proposal myself because I'm not sure if there
 are other issues at work here (I don't know the simplifier much at all),
 and I don't know if there is even a way to get ghcspeed to do this for us.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9927>
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