[GHC] #12979: -fspecialise-aggressively is not documented

[GHC]

#12979: -fspecialise-aggressively is not documented
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        Reporter:  mpickering        |                Owner:
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  newcomer
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 danharaj):

 The relevant documentation seems to be:

 {{{
 Note [Specialise imported INLINABLE things]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 What imported functions do we specialise?  The basic set is
  * DFuns and things with INLINABLE pragmas.
 but with -fspecialise-aggressively we add
  * Anything with an unfolding template

 Trac #8874 has a good example of why we want to auto-specialise DFuns.

 We have the -fspecialise-aggressively flag (usually off), because we
 risk lots of orphan modules from over-vigorous specialisation.
 However it's not a big deal: anything non-recursive with an
 unfolding-template will probably have been inlined already.
 }}}

 I have experimented with using this flag too, but it didn't do much for my
 use case beyond `-fexpose-all-unfoldings` and generous use of `INLINABLE`.
 As I understand it, instead I could use `-fexpose-all-unfoldings` and
 `-fspecialise-aggressively` and need not worry about putting `INLINABLE`
 annotations on my declarations. Is that correct?

 By the way, it is really brutal on compilation times!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12979#comment:3>
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