On Tue, Jan 10, 2017 at 08:34:29AM -0600, Eric Blake wrote: > On 01/09/2017 08:10 PM, Jose Ricardo Ziviani wrote: > > Implements 128-bit left shift and right shift as well as their > > testcases. By design, shift silently mods by 128, so the caller is > > responsible to assert the shift range if necessary. > > > > Left shift sets the overflow flag if any non-zero digit is shifted out. > > > > Examples: > > ulshift(&low, &high, 250, &overflow); > > equivalent: n << 122 > > > > urshift(&low, &high, -2); > > equivalent: n << 126 > > > > Signed-off-by: Jose Ricardo Ziviani <[email protected]> > > --- > > > +typedef struct { > > + uint64_t low; > > + uint64_t high; > > + uint64_t rlow; > > + uint64_t rhigh; > > + int32_t shift; > > + bool overflow; > > +} test_data; > > + > > +static const test_data test_ltable[] = { > > + { 0x4C7ULL, 0x0ULL, 0x00000000000004C7ULL, > > + 0x0000000000000000ULL, 0, false }, > > I might have laid it out as: > > { 0x00000000000004c7ULL, 0x0000000000000000ULL, > 0x00000000000004c7ULL, 0x0000000000000000ULL, > 0, false } > > to make the pre- and post-shift values line up better. It's not fatal > to the patch, so it's up to the maintainer if they want a v6 to improve > the alignment.
host-utils doesn't have a maintainer. So, I'm intending to take it
through my tree with your R-b.
> > + { 0x8888888888888888ULL, 0x9999999999999999ULL,
> > + 0x8000000000000000ULL, 0x9888888888888888ULL, 60, true },
> > + { 0x8888888888888888ULL, 0x9999999999999999ULL,
> > + 0x0000000000000000ULL, 0x8888888888888888ULL, 64, true },
>
> These two are the most legible.
>
> > +};
> > +
> > +static const test_data test_rtable[] = {
>
> > +++ b/util/host-utils.c
> > @@ -161,3 +161,67 @@ int divs128(int64_t *plow, int64_t *phigh, int64_t
> > divisor)
> > }
> > #endif
> >
> > +/**
> > + * urshift - 128-bit Unsigned Right Shift.
> > + * @plow: in/out - lower 64-bit integer.
> > + * @phigh: in/out - higher 64-bit integer.
> > + * @shift: in - bytes to shift, between 0 and 127.
> > + *
> > + * Result is zero-extended and stored in plow/phigh, which are
> > + * input/output variables. Shift values outside the range will
> > + * be mod to 128. In other words, the caller is responsible to
> > + * verify/assert both the shift range and plow/phigh pointers.
> > + */
>
> Duplicating docs in the .h and .c doesn't hurt, but risks one getting
> out of date; we have other spots that put the docs in the .h (where
> callers will look up what's available) or the .c (where the
> implementation is there to check against the docs). I don't have any
> strong preference on how to do it, though, so I don't mind leaving it as is.
>
> Reviewed-by: Eric Blake <[email protected]>
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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