Two suggestions for gcc C compiler to extend C language (by WD Smith)

[Joseph Myers]

On Tue, 26 Jul 2016, Warren D Smith wrote:

> However, why not provide access to double-precision multiply and
> add-with-carry (subtract with borrow? shift-left?) in the same fashion?
>    twofer  x = mul(a,b);  would cause  x.hi and x.lo  to be computed.
>    twofer  x = addwithcarry(a,b)   ditto.

If add-with-carry were provided then it would be appropriate to provide 
Clang-compatible __builtin_addc* (in addition to any type-generic form 
provided to allow the functionality to be used with types such unsigned 
__int128).  (I don't see Clang built-ins to be compatible with for 
double-precision multiply.)

-- 
Joseph S. Myers
joseph@codesourcery.com