[GHC] #14672: Make likelyhood of branches/conditions available throughout the compiler.

[GHC]

#14672: Make likelyhood of branches/conditions available throughout the compiler.
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        Reporter:  AndreasK          |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4316
       Wiki Page:                    |  Phab:D4324 Phab:D4327
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Comment (by AndreasK):

 Replying to [comment:8 svenpanne]:
 > Just a general remark: [https://phabricator.haskell.org/D4327 D4327]
 talks about annotations as a source of likelihood values, which is fine,
 but having actual data from previous runs, i.e. using profile-guided
 optimization, would probably have much more potential.

 I was talking about annotations primarily because they seem like the low
 hanging fruit.

 As far as the native codegen is concerned it makes no difference if the
 data comes from user suggestions or actual measurements. Having good data
 on all code paths would certainly be better then just an estimate for some
 paths the user annotated.

 Once we have a way to pass/use the information throughout the passes
 adding PGO is the next logical step and should be possible without
 touching anything past core.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14672#comment:10>
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