Portable "add with carry" loop for arbitrary precision arithmetic
Ian Lance Taylor
Mon Jun 23 13:49:00 GMT 2008
"Alexander Konovalenko" <firstname.lastname@example.org> writes:
> There is an "add with carry" instruction on some architectures which
> enables efficient implementation of arbitrary precision (bignum)
> integer addition. Is it possible to make gcc generate efficient
> machine code from pure C or C++ code for bignum addition on those
> It looks like the popular libraries like GMP and CLN use hand-coded
> assembly for that. I wonder if gcc can help rewrite that kind of code
> in a more portable way.
In general, no, except for the limiting case of the "long long" type.
gcc doesn't provide any machine independent access to the carry flag.
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