[GHC] #10720: New GHC fails to specialize imported function

[GHC]

#10720: New GHC fails to specialize imported function
-------------------------------------+-------------------------------------
        Reporter:  wyager            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.2
      Resolution:                    |                Keywords:
                                     |  performance, inline, specialize
Operating System:  MacOS X           |            Architecture:  x86_64
 Type of failure:  Runtime           |  (amd64)
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by simonpj):

 I tried this.  It's all behaving as advertised

  * You need an `INLINEABLE` pragma on `(**)`.
  * If you add that, then `(**)` is getting specialised perfectly well; but
 it calls `(*)`, which is not.
  * So you need an `INLINEABLE` pragma on `(*)` too.

 Admittedly this isn't terribly clear. I'll add some new warnings to point
 out that this might be happening.

 Meanwhile, you might just want to confirm that this is indeed ok for you.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10720#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler