[Bug target/67317] [x86] Silly code generation for _addcarry_u32/_addcarry_u64

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67317

--- Comment #5 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Combine can handle most RTL expressions, although it sometimes
simplifies (or "simplifies") more than you want.

I think in this case what is already done in *add<mode>3_cc_overflow
will work well, but I do not know x86 CC modes terribly well.  You'll
need to experiment a bit to find something that works well in all
interesting cases.