On Wed, 7 Apr 2021, Huacai Chen wrote: > > This code is rather broken in an obvious way, starting from: > > > > unsigned long long __n; \ > > \ > > __high = *__n >> 32; \ > > __low = __n; \ > > > > where `__n' is used uninitialised. Since this is my code originally I'll > > look into it; we may want to reinstate `do_div' too, which didn't have to > > be removed in the first place. > I think we can reuse the generic do_div(). We can, but it's not clear to me if this is optimal. We have a DIVMOD instruction which original code took advantage of (although I can see potential in reusing bits from include/asm-generic/div64.h). The two implementations would have to be benchmarked against each other across a couple of different CPUs. > > Huacai, thanks for your investigation! Please be more careful in > > verifying your future submissions however. > Sorry, I thought there is only one bug in div64.h, but in fact there > are three... This just shows the verification you made was not good enough, hence my observation. Maciej
