[GHC] #14519: Exponential runtime performance regression in GHC 8.2 + Data.Text.Lazy + Text.RE.TDFA

[GHC]

#14519: Exponential runtime performance regression in GHC 8.2 + Data.Text.Lazy +
Text.RE.TDFA
-------------------------------------+-------------------------------------
        Reporter:  ntc2              |                Owner:  tdammers
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime           |            Test Case:
  performance bug                    |  https://github.com/ntc2/ghc-8.2.1
                                     |  -regex-lazy-text-
                                     |  bug/tree/07b7bb32c6e90e8f2d2eada4b59943f37e632d53
      Blocked By:                    |             Blocking:
 Related Tickets:  #13745, #14564    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by ntc2):

 @simonpj, you can reproduce by checking out the repo with the `slow-regex`
 test package (https://github.com/ntc2/ghc-8.2.1-regex-lazy-text-bug),
 building it, and then running the `slow-regex` executable that produces
 with arguments "text-lazy" and the name of one of the test files. E.g.
 {{{
 slow-regex text-lazy defs-10000.txt
 }}}
 The `defs-10000.txt` test file is included with the test package.

 With GHC 8.2.2, using new Cabal:
 {{{
 git clone git at github.com:ntc2/ghc-8.2.1-regex-lazy-text-bug.git
 cd ghc-8.2.1-regex-lazy-text-bug.git
 cabal new-build slow-regex
 ./dist-newstyle/build/x86_64-linux/ghc-8.2.2/slow-regex-0.1.0.0/c/slow-
 regex/build/slow-regex/slow-regex text-lazy defs-10000.txt
 }}}

 With GHC 8.2.2, using Stack:
 {{{
 git clone git at github.com:ntc2/ghc-8.2.1-regex-lazy-text-bug.git
 cd ghc-8.2.1-regex-lazy-text-bug.git
 stack build --stack-yaml stack-ghc-8.2.2.yaml slow-regex
 stack exec --stack-yaml stack-ghc-8.2.2.yaml slow-regex text-lazy
 defs-10000.txt
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14519#comment:20>
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