Use bmi2 and multi precision add carry instruction extensions in the case of Intel ?

[ytrezq]

https://en.wikipedia.org/wiki/Intel_ADX for adcx/adox and mulx/sarx/shrx/shlx being in bmi2. I recognize the gcc-go for accessing them as compiler defined functions/instructions instead of raw assembly.

gmp/mpir is using them along other extensions for most cpu instructions sets.