[GHC] #15103: Speed optimizations for elimCommonBlocks

[GHC]

#15103: Speed optimizations for elimCommonBlocks
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        Reporter:  AndreasK          |                Owner:  AndreasK
            Type:  task              |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.5
      Resolution:                    |             Keywords:  CodeGen
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4597
       Wiki Page:                    |
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Comment (by AndreasK):

 Replying to [comment:7 simonpj]:
 > What is the perf impact of this optimisation, if any?

 Generated code is the same. Compiler performance changes for the better.

 I think the file I looked at was nofib/spectral/simple

 `ghc-stage2 -fforce-recomp -c -O1 Main.hs +RTS -s -RTS`
 || build ||  Allocated (Byte) || measured time ||
 || master || 4,475,812,248   || 3.220 s    (3.204 s .. 3.251 s) ||
 || toBlockList || 4,474,452,216 ||   3.196 s    (3.192 s .. 3.204 s) ||
 || IntMap + blockList || 4,461,727,496 || 3.189 s    (3.174 s .. 3.203 s)
 ||

 > I think the goal is to improve compile times, right?  Not run-time.

 Yes it's purely an "make GHC faster" patch.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15103#comment:8>
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