[GHC] #13817: Simplifier and SpecConstr performance regression with 8.2.1

[GHC]

#13817: Simplifier and SpecConstr performance regression with 8.2.1
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        Reporter:  albertov          |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1-rc1
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by dfeuer):

 * status:  new => infoneeded


Old description:

> A propietary application I've upgraded to compile with 8.2.1-rc1 makes
> GHC manifest a performance regression when producing optimized
> ({{{-O2}}}) code.
>
> After a crude analysis of a compile log produced with {{{-show-passes}}}
> it appears that the biggest slowdown is in the Simplifier and SpecConstr
> phases when compiling the "main" modules.
>
> Theres a conversation at GHC Users with more details:
> https://mail.haskell.org/pipermail/glasgow-haskell-
> users/2017-June/026543.html. The data, the results and the script to to
> analyse it live at:
> https://gist.github.com/albertov/145ac5c01bfbadc5c9ff55e9c5c2e50e
>
> I'll try to update this ticket with a way to to reproduce it as soon as I
> can (if I can)

New description:

 A proprietary application I've upgraded to compile with 8.2.1-rc1 makes
 GHC manifest a performance regression when producing optimized ({{{-O2}}})
 code.

 After a crude analysis of a compile log produced with {{{-show-passes}}}
 it appears that the biggest slowdown is in the Simplifier and SpecConstr
 phases when compiling the "main" modules.

 Theres a conversation at GHC Users with more details:
 https://mail.haskell.org/pipermail/glasgow-haskell-
 users/2017-June/026543.html. The data, the results and the script to to
 analyse it live at:
 https://gist.github.com/albertov/145ac5c01bfbadc5c9ff55e9c5c2e50e

 I'll try to update this ticket with a way to to reproduce it as soon as I
 can (if I can).

--

Comment:

 I don't think we can do anything about this without a proper reproduction.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13817#comment:2>
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