Re: [PATCH v2 0/4] MR375: ntdll: Fixes for runtime 64-bit shift functions.

[Zebediah Figura (she/her)]

On 7/6/22 10:50, Jinoh Kang (@iamahuman) wrote:
> Jinoh Kang (@iamahuman) commented about dlls/ntdll/large_int.c:
> > +LONGLONG __regs__allshl( LONGLONG a, unsigned char b )
> > +{
> > - const LARGE_INTEGER x = { .QuadPart = a };
> > - LARGE_INTEGER ret;
> > -
> > - if (b >= 64)
> > -
> >    return 0;
> > -
> > - if (b >= 32)
> > - {
> > -
> >    ret.HighPart = x.LowPart << (b & 31);
> > -
> >    ret.LowPart = 0;
> > - }
> > - else
> > - {
> > -
> >    ret.HighPart = (x.LowPart >> (32 - b)) | (x.HighPart << b);
>
> Shall we use intrinsics such as `__ll_lshift` (`shld` instruction)? Ditto for other functions.

I suppose we could, although ideally GCC would just recognize this 
pattern and generate shld.