[GHC] #9476: Implement late lambda-lifting

[GHC]

#9476: Implement late lambda-lifting
-------------------------------------+-------------------------------------
        Reporter:  simonpj           |                Owner:  sgraf
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.8.2
      Resolution:                    |             Keywords:  LateLamLift
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #8763 #13286      |  Differential Rev(s):
       Wiki Page:  LateLamLift       |
-------------------------------------+-------------------------------------

Comment (by sgraf):

 The allocation heuristic
 (https://github.com/sgraf812/ghc/blob/9b9260c1d45d127edf9ebdfe04a3daaff24a9dea/compiler/simplStg/StgLiftLams/Analysis.hs#L235)
 tries to estimate closure growth and only allows the lift if it can
 guarantee that there are no regressions.

 I think this is quite essential to identify beneficial lifts, as well as
 non-trivial to implement. The whole `Analysis` module linked above mostly
 revolves around computing this `costToLift`
 https://github.com/sgraf812/ghc/blob/9b9260c1d45d127edf9ebdfe04a3daaff24a9dea/compiler/simplStg/StgLiftLams/Analysis.hs#L375.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9476#comment:36>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler