[GHC] #14490: TTG Snags

[GHC]

#14490: TTG Snags
-------------------------------------+-------------------------------------
        Reporter:  alanz             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14482            |  Differential Rev(s):
       Wiki Page:                    |
  ImplementingTreesThatGrow          |
-------------------------------------+-------------------------------------

Comment (by alanz):

 Comparing compile performance for current master (with TTG) and after
 reverting.

 1. Check timing on home.smart-cactus.org, for current master
    at 25f36bd7ba6899be6c720292528c56bc35e0f089

 a. Make mk/validate.mk which overrides the mk/flavours/validate.mk one
    Set:
      `GhcStage2HcOpts    = -ddump-timings -O -dcore-lint -dno-debug-
 output`
 b. Run
 {{{#!sh
    $ make maintainer-clean
    $ CPUS=6 ./validate >> master-validate.log 2>&1
 }}}
 2. Revert the prior TTG commits

    on branch `wip/revert-ttg-2017-11-20`

    GHC/master
    - 438dd1cbba13d35f3452b4dcef3f94ce9a216905
    - e3ec2e7ae94524ebd111963faf34b84d942265b4
    - 47ad6578ea460999b53eb4293c3a3b3017a56d65

    haddock/ghc-head
    - 01eeeb048acd2dd05ff6471ae148a97cf0720547
    - 73a26af844ac50b8bec39de11d64452a6286b00c
    - 9f054dc365379c66668de6719840918190ae6e44
    - 134a7bb054ea730b13c8629a76232d73e3ace049

 3. Run the timing again
 {{{#!sh
    $ make maintainer-clean
    $ CPUS=6 ./validate >> revert-validate.log 2>&1
 }}}

 Results to follow

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14490#comment:16>
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