[GHC] #13016: SPECIALIZE INLINE doesn't necessarily inline specializations of a recursive function

[GHC]

#13016: SPECIALIZE INLINE doesn't necessarily inline specializations of a recursive
function
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        Reporter:  nfrisby           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  Inlining
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13014            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mpickering):

 I discussed this on IRC with David briefly.

 {{{
 mpickering> dfeuer: I don't think SPECIALISE INLINE ever worked like you
 are suggesting. I think it just works like SPECIALISE and then marks the
 specialisation with an INLINE pragma
 10:07 PM <mpickering> I was under the impression that SpecConstr allowed
 you to force this unrolling to happen
 10:08 PM <mpickering> The manual states that "and applies even if the
 function is recursive."
 10:09 PM <mpickering> but I don't know what this means or how it works as
 there is no special check in the simplifier to inline specialisations
 arising from SPECIALISE INLINE pragmas
 10:09 PM <dfeuer> mpickering: I'm just going off of the documentation that
 was added when SPECIALISE INLINE was.
 10:09 PM <dfeuer> The only way I know to push really hard for SpecConstr
 is using that funky pseudo-argument.
 10:10 PM <mpickering> there is another deprecated way
 10:10 PM <mpickering> but yes you have to use that argument or use a flag
 I think
 10:11 PM <dfeuer> mpickering: well, if the documentation is just wrong,
 and wasn't intended to be right, then we need to fix the documentation.
 10:11 PM <mpickering> indeed, I've just been trying to work out the
 intention, implementation and documentation line up with each other
 10:11 PM <mpickering> as they clearly don't at the moment
 10:12 PM <dfeuer> But I do think it's worth considering; the funny special
 argument is highly unlikely to appear in any other (future) Haskell
 implementation, so using it is screaming "GHC only forever".
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13016#comment:9>
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