Re: [PATCH v2 05/19] host-utils: Add muldiv64_round_up

[Richard Henderson]

On 9/1/23 04:51, Cédric Le Goater wrote:
> Adding more reviewers since this patch is modifying a common service.
>
> Thanks,
>
> C.
>
>
> On 8/8/23 06:19, Nicholas Piggin wrote:
> > This will be used for converting time intervals in different base units
> > to host units, for the purpose of scheduling timers to emulate target
> > timers. Timers typically must not fire before their requested expiry
> > time but may fire some time afterward, so rounding up is the right way
> > to implement these.
> >
> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> > ---
> >   include/qemu/host-utils.h | 21 ++++++++++++++++++++-
> >   1 file changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
> > index 011618373e..e2a50a567f 100644
> > --- a/include/qemu/host-utils.h
> > +++ b/include/qemu/host-utils.h
> > @@ -56,6 +56,11 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b, 
> > uint32_t c)
> >       return (__int128_t)a * b / c;
> >   }
> > +static inline uint64_t muldiv64_round_up(uint64_t a, uint32_t b, uint32_t c)
> > +{
> > +    return ((__int128_t)a * b + c - 1) / c;
> > +}
> > +
> >   static inline uint64_t divu128(uint64_t *plow, uint64_t *phigh,
> >                                  uint64_t divisor)
> >   {
> > @@ -83,7 +88,8 @@ void mulu64(uint64_t *plow, uint64_t *phigh, uint64_t a, 
> > uint64_t b);
> >   uint64_t divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor);
> >   int64_t divs128(uint64_t *plow, int64_t *phigh, int64_t divisor);
> > -static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
> > +static inline uint64_t __muldiv64(uint64_t a, uint32_t b, uint32_t c,
> > +                                  bool round_up)

Perhaps better avoiding the reserved name: muldiv64_internal?

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~


> >   {
> >       union {
> >           uint64_t ll;
> > @@ -99,12 +105,25 @@ static inline uint64_t muldiv64(uint64_t a, uint32_t b, 
> > uint32_t c)
> >       u.ll = a;
> >       rl = (uint64_t)u.l.low * (uint64_t)b;
> > +    if (round_up) {
> > +        rl += c - 1;
> > +    }
> >       rh = (uint64_t)u.l.high * (uint64_t)b;
> >       rh += (rl >> 32);
> >       res.l.high = rh / c;
> >       res.l.low = (((rh % c) << 32) + (rl & 0xffffffff)) / c;
> >       return res.ll;
> >   }
> > +
> > +static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
> > +{
> > +    return __muldiv64(a, b, c, false);
> > +}
> > +
> > +static inline uint64_t muldiv64_round_up(uint64_t a, uint32_t b, uint32_t c)
> > +{
> > +    return __muldiv64(a, b, c, true);
> > +}
> >   #endif
> >   /**