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

["Cédric Le Goater" <clg@kaod.org>]

On 9/4/23 15:07, Nicholas Piggin wrote:
> On Sat Sep 2, 2023 at 3:02 AM AEST, Richard Henderson wrote:
>> 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?
> 
> Thanks, that would be okay. Or could be muldiv64_rounding?
> 
>>
>> Otherwise,
>> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

oh, and I already sent the PR with the Rb of Richard ... :/
Sorry about that. Can we fix it later ? Or I will respin with
the update.

Someone really ought to take over PPC. Daniel and I are real
busy on other subsystems. Volunteers ?

Thanks,

C.

>>
>>
>> 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
>>>>    /**
>>>
>>>
>