search for: _mulx_64

...I never considered >> using them, but they might be better alternative to inline assembly. >> Is there a one for regular MUL? >> > > I'm not sure, but I think there currently does not exist any intrinsic to > generate the top half of a 64x64=128 multiply, except for `_mulx_64`. > If Clang stopped requiring `-mbmi2`, I would then expect the `_mulx_64` > intrinsic to generate a regular MUL instruction; similar to > how_addcarry_u64 generates ADCX/ADOX when available/useful and a regular > ADC otherwise. > MSVC calls this intrinsic `_umul128 > <https:/...

_mulx_u64 only exists when the target is x86_64. That's still not very portable. I'm not opposed to removing the bmi2 check, but gcc also has the same check so it doesn't improve portability much. ~Craig On Sat, Dec 29, 2018 at 4:44 PM Arthur O'Dwyer via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Hi Pawel, > > There is the _mulx_u64 intrinsic, but it