[GHC] #13477: Turn cIntegerLibraryType into a dynflag

[GHC]

#13477: Turn cIntegerLibraryType into a dynflag
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  patch
        Priority:  low               |            Milestone:
       Component:  GHC API           |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D5079
       Wiki Page:                    |
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Comment (by Krzysztof Gogolewski <krz.gogolewski@…>):

 In [changeset:"fc2ff6dd7496a33bf68165b28f37f40b7d647418/ghc"
 fc2ff6dd/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="fc2ff6dd7496a33bf68165b28f37f40b7d647418"
 Make GHC (the library) flexible in the choice of integer library

 Summary:
 We have more and more users of GHC as a library, for example the
 Haskell-to-WebAssembly-compiler https://github.com/tweag/asterius.
 These need to make different decisions about various aspects of
 code generation than the host compiler, and ideally GHC-the-library
 allows them to set the `DynFlags` as needed.

 This patch adds a new `DynFlag` that configures which `integer`
 library to use. This flag is initialized by `cIntegerLibraryType`
 (as before), and is only used in `CorePrep` to decide whether to
 use `S#` or not.

 The other code paths that were varying based on `cIntegerLibraryType`
 are no now longer varying: The trick is to use `integer-wired-in`
 as the `-this-unit-id` when compiling either `integer-gmp` or
 `integer-simple`.

 Test Plan: Validate is happy.

 Reviewers: hvr, bgamari

 Reviewed By: bgamari

 Subscribers: TerrorJack, adamse, simonpj, rwbarton, carter

 GHC Trac Issues: #13477

 Differential Revision: https://phabricator.haskell.org/D5079
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13477#comment:4>
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