search for: umul128

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2018 Dec 31
0
[cfe-dev] Portable multiplication 64 x 64 -> 128 for int128 reimplementation
...ly, 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://docs.microsoft.com/en-us/cpp/intrinsics/umul128?view=vs-2017>`, > and on MSVC it does generate a regular MUL instruction rather than forcing > MULX. > > > Anyway, I want to go the opposite direction. [...] mulx() helper without >> using __int128 type in a wa...
2018 Dec 30
3
[cfe-dev] Portable multiplication 64 x 64 -> 128 for int128 reimplementation
_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