[GHC] #13346: Run nofib with -fspec-constr-keen

[GHC]

#13346: Run nofib with -fspec-constr-keen
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mpickering):

 Increased allocations could be due to reboxing as described in section 6.1
 of the original paper.

 In a few experiments, it does seem that flag causes quite aggressive
 optimisation in the case of static arguments.

 For example:

 {{{
 main = drop 2 [1,2,3]
 }}}

 leads to

 {{{
 -- RHS size: {terms: 1, types: 0, coercions: 0, joins: 0/0}
 Foo.main1 :: Integer
 [GblId,
  Caf=NoCafRefs,
  Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 100 0}]
 Foo.main1 = 3

 -- RHS size: {terms: 3, types: 2, coercions: 0, joins: 0/0}
 main :: [Integer]
 [GblId,
  Caf=NoCafRefs,
  Str=m2,
  Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True,
          WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 30}]
 main = GHC.Types.: @ Integer Foo.main1 (GHC.Types.[] @ Integer)
 }}}

 Notice that `drop` has been fully evaluated even though it is self-
 recursive.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13346#comment:4>
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