[GHC] #15124: Improve block layout for the NCG

[GHC]

#15124: Improve block layout for the NCG
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        Reporter:  AndreasK          |                Owner:  AndreasK
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (NCG)    |              Version:  8.2.2
      Resolution:                    |             Keywords:  CodeGen
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #8082 #14672      |  Differential Rev(s):  Phab:D4726
       Wiki Page:                    |
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Changes (by AndreasK):

 * differential:   => Phab:D4726
 * related:  #8082 => #8082 #14672


Comment:

 I've wrote up a patch implementing an experimental code layout algorithm,
 which hopefully is easy to adjust to take advantage of additional
 information about control flow.

 Code is at Phab:D4726. As it stands:

 * It works (only) on x64.
 * Performance is around the same. (Better but within the margin of error).
 * Compiler performance is slightly worse.

 There are a lot of knobs to tune this approach further but verifying any
 results is tedious so I stopped eventually.

 For now I hope to use this eventually as a substrate for the work on
 #14672.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15124#comment:5>
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