[GHC] #14697: Redundant computation in fingerprintDynFlags when compiling many modules

[GHC]

#14697: Redundant computation in fingerprintDynFlags when compiling many modules
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        Reporter:  niteria           |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:
      Resolution:                    |             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):  phab:D4445
       Wiki Page:                    |
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Comment (by Bartosz Nitka <niteria@…>):

 In [changeset:"b8f03bbe16af7a09b494a33fbbe523ecd82f1a50/ghc"
 b8f03bbe/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="b8f03bbe16af7a09b494a33fbbe523ecd82f1a50"
 Cache the fingerprint of sOpt_P

 Before this change we would compute a hash of
 all the command line -optP flags once per file.
 With a lot of files and many -optP flags, that's a lot
 of repeated work.

 I added a new Note that explains the approach and rationale.

 Test Plan: new test

 Reviewers: simonmar, simonpj, bgamari

 Reviewed By: simonpj

 Subscribers: rwbarton, thomie, carter

 GHC Trac Issues: #14697

 Differential Revision: https://phabricator.haskell.org/D4445
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14697#comment:3>
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