bug in longlong.h for aarch64 sub_ddmmss

[Torbjörn Granlund]

nisse at lysator.liu.se (Niels Möller) writes:

  tg at gmplib.org (Torbjörn Granlund) writes:

  > The two - signs ought to be ~, I think.  Let me think a buit more about that.

  If I remember ARM conventions correctly, subtract with carry is defined
  as

    {cout, r} = a + ~b + cin

Here we traded non-borrow subtract and non-carry addition on both ARM
and PPC.

Subtract is defined on both these architectures as

    {cout, r} = a + ~b + 1

while addition is refined similarly as

    {cout, r} = a + b

.

-- 
Torbjörn
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