bug in longlong.h for aarch64 sub_ddmmss

[Vincent Lefevre]

On 2020-06-17 11:04:26 +0200, Niels Möller wrote:
> 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

This is a - b - borrow, where the borrow is the complement of the
carry bit.

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