[GHC] #8647: Reduce allocations in `integer-gmp`

[GHC]

#8647: Reduce allocations in `integer-gmp`
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        Reporter:  hvr                      |            Owner:
            Type:  task                     |           Status:  patch
        Priority:  normal                   |        Milestone:  7.8.1
       Component:  libraries (other)        |          Version:  7.6.3
      Resolution:                           |         Keywords:  integer-
Operating System:  Unknown/Multiple         |  gmp
 Type of failure:  Runtime performance bug  |     Architecture:  x86_64
       Test Case:                           |  (amd64)
        Blocking:                           |       Difficulty:  Unknown
                                            |       Blocked By:
                                            |  Related Tickets:  #8638
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Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"0476327376045838375fbbe4a78c02859a1913cb/integer-gmp"]:
 {{{
 #!CommitTicketReference repository="integer-gmp"
 revision="0476327376045838375fbbe4a78c02859a1913cb"
 Dont use big/small-int primops on IL32P64 (i.e. Win/x86_64) for now

 This is due to `mpz_*()` functions having @long@ arguments which are
 32bit on IL32P64, whereas `Int#` and `Word#` are 64bit wide, causing all
 sorts of malfunction due to truncation.

 This affects mostly the new big/small-int primops introduced in the
 course of #8647, so when `SIZEOF_W != SIZEOF_LONG` we simply fall back
 to using the big/big-int primops. big/small primops implemented via the
 low-level `mpn_*()` GMP operations are not affected, as those use
 `mp_limb_t` arguments.

 Signed-off-by: Herbert Valerio Riedel <hvr at gnu.org>
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8647#comment:17>
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