[GHC] #9281: Rewrite `integer-gmp` to use only non-allocating GMP functions

[GHC]

#9281: Rewrite `integer-gmp` to use only non-allocating GMP functions
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       Reporter:  hvr                |             Owner:  hvr
           Type:  task               |            Status:  new
       Priority:  normal             |         Milestone:  7.10.1
      Component:  libraries (other)  |           Version:
       Keywords:  integer-gmp        |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple   |   Type of failure:  None/Unknown
     Difficulty:  Unknown            |         Test Case:
     Blocked By:                     |          Blocking:
Related Tickets:                     |
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 After some promising results with a proof-of-concept implementation, I'm
 optimistic we can rewrite `integer-gmp` to use only non-allocating GMP lib
 functions without suffering from serious regressions.

 If successful, this would

  - allow to avoid the custom GMP allocator hack, and thus
  - avoid issues when linking against other C libraries using GMP,
  - simplify code, as we would perform all heap allocations in Haskell code
 (and never inside Cmm/C code as its done now),
  - and finally maybe even remove a few more superfluous temporary heap
 allocations.

 This rewrite can be done incrementally.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9281>
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