Re: [PATCH v2] sparc/vdso: Add helper function for 64-bit right shift on 32-bit target

[Koakuma]

Andreas Larsson <andreas@xxxxxxxxxxx> wrote:
> Koakuma via B4 Relay wrote:
> > +notrace static __always_inline u64 __shr64(u64 val, int amt)
> > +{
> > + u64 ret;
> > +
> > + asm volatile("sllx %H1, 32, %%g1\n\t"
> > + "srl %L1, 0, %L1\n\t"
> > + "or %%g1, %L1, %%g1\n\t"
> > + "srlx %%g1, %2, %L0\n\t"
> > + "srlx %L0, 32, %H0"
> > + : "=r" (ret)
> > + : "r" (val), "r" (amt)
> > + : "g1");
> > + return ret;
> > +}
> 
> Can not residual in bits 63:32 of %L0 potentially pose a problem?

It shouldn't be a problem, upon returning the caller should treat
the upper bits of %L0 as an unspecified value and not depend on/use
its contents.