[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:  8.8.1
       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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Comment (by AndreasK):

 Snapshot of the performance gains by the linked patch. (Speedup - so
 **higher is better**).
 Last I checked nofib performance was neither here no there in terms of
 runtime. (Slightly slower on sandy bridge, slightly faster on haswell).
 Compile time with the patch went down on both though.

 || Library ||Sandy Bridge (Linux) || Haswell (Linux) || Skylake (Win) ||
 || aeson         || +2.6%/+2.8%   || +2.3%/-0%         ||   +1.2%/+1.0%
 || containers    || +1.4%/+1.2%   || +1.1%/+1.7%       ||   +1.7%/+1.0%
 || megaparsec    || +3.2%/+3.6%   || +13.6%/+13.7% 1)  ||   +8.0%/+6.6%
 || perf-xml    || +0.2%/+0.0%   ||         || +1.1%/+0.8%
 || text          || +3.0%/+3.0%   || NA                ||   NA
 || Vector      || +2.5%/+3.6%   || +2.5%/+2.9%       ||   +1.3%/3.8%

 1 ) Inflated by background noise.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15124#comment:9>
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