GCC does not generate ADCX or ADOX for _addcarryx_u64

[Jeffrey Walton]

On Mon, Aug 21, 2017 at 7:20 AM, Marc Glisse <marc.glisse@inria.fr> wrote:
> On Mon, 21 Aug 2017, Jeffrey Walton wrote:
>
>> I'm trying to use _addcarryx_u64. GCC 7.1 is still generating ADD and
>> ADC instead of ADCX or ADOX:
>
> Does that compute wrong values? Make the program slower?

It looks like the values are computed correctly.

I don't know the affect on performance. The only benchmarks I have are
for add/adc. I can't get the adcx/adox generated to benchmark them.

Compared to Intel ICC code generation, Intel's code is about 20% to 30% smaller.

Jeff