[GHC] #11725: Performance Regression from 7.8.3 to 7.10.3

[GHC]

#11725: Performance Regression from 7.8.3 to 7.10.3
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        Reporter:  dominic           |                Owner:  dominic
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dominic):

 Here's my proposed approach to pinning it down.

 1. Build ghc-8.0.1-rc2 and run my program under it. If the regression is
 gone then I propose to do no further investigation.
 2. git bisect the sources from 7.8.3 to 7.10.3 until I find the change
 that causes the regression.

 Does that sound reasonable? Is there any guidance on how to do (2)
 efficiently and effectively?

 At the moment I cannot get my sources to compile under ghc-8.0.1-rc2 so my
 first mini-step is to solve this.

 I should point out that this is somewhat tangential to my day job although
 we use RNGs extremely heavily in our application.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11725#comment:5>
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