[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 tdammers):

 Correct, but that's why I needed to dig deeper - ticky-ing only the module
 itself didn't reveal anything, but compiling a bunch of dependencies with
 -ticky as well gives me this line:

 {{{
  2250377760180010799840          0   2 Mi                   $wnext2{v
 reC2} (regex-tdfa-
 text-1.0.0.3-CIfFZ6rjdCoJI5EFpqTwBO:Text.Regex.TDFA.Text.Lazy) (fun)
 }}}

 (note that it actually overflows the `Alloc` field, so that's two large
 numbers concatenated together there)

 I can't seem to find `wnext2` anywhere in the dumps though, which is a bit
 strange.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14519#comment:13>
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