[GHC] #12191: 7% allocation regression in Haddock performance tests

[GHC]

#12191: 7% allocation regression in Haddock performance tests
-------------------------------------+-------------------------------------
           Reporter:  bgamari        |             Owner:
               Type:  task           |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  performance bug
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 One of the commits below is responsible for a rather significant
 [[https://perf.haskell.org/ghc/#revision/d55a9b4fd5a3ce24b13311962bca66155b17a558|regression]]
 in the `haddock.Cabal` and `haddock.compiler` testcases,

 {{{
 d55a9b4fd5a3ce24b13311962bca66155b17a558
 0497ee504cc9ac5d6babee9b98bf779b3fc50b98
 586d55815401c54f4687d053fb033e53865e0bf1
 7de776cfe7825fca6a71fe6b3854c3c86bf9ca12
 5cee88d766723929f789ffcd2ef24d8b5ef62a16
 1dcb32ddba605bced2e0e0ce3f52b58e8ff33f5b
 921ebc9f0854d033cbafd43d3b2c5ba679c27b3c
 e064f501d76c208ddab3c3be551ffe5167d7974f
 8104f7c674d7ef2db0c25312f48763202dcef57f
 599d912f0b85583e389661d85ed2f198e2621bb0
 15fc52819c440f9e9b91ce92fcfda3c264cbe1c1
 1f661281a23b6eab83a1144c43e464c0e2d2195a
 35c9de7ca053eda472cb446c53bcd2007bfd8394
 7afb7adf45216701e4f645676ecc0668f64b424d
 c28dde37f3f274a2a1207dd4e175ea79769f5ead
 15b9bf4ba4ab47e6809bf2b3b36ec16e502aea72
 }}}

 It would be nice to identify which of these is the culprit. The fix in
 `d55a9b4fd5a3ce24b13311962bca66155b17a558` will need to be applied on top
 of each of these to allow things to build.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12191>
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