Re: [Qemu-devel] [PATCH 1/2] qemu-common.h: optimise muldiv64 if int128 is available

[Peter Maydell]

On 9 January 2015 at 11:25, Frediano Ziglio <address@hidden> wrote:
> Let compiler do the job to optimise the function.
>
> Signed-off-by: Frediano Ziglio <address@hidden>
> ---
>  include/qemu-common.h | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/include/qemu-common.h b/include/qemu-common.h
> index f862214..f3033ae 100644
> --- a/include/qemu-common.h
> +++ b/include/qemu-common.h
> @@ -370,6 +370,12 @@ static inline uint8_t from_bcd(uint8_t val)
>  }
>
>  /* compute with 96 bit intermediate result: (a*b)/c */
> +#ifdef CONFIG_INT128
> +static inline uint64_t muldiv64(uint64_t a, uint32_t b, uint32_t c)
> +{
> +    return (__int128)a * b / c;

Wrong type -- this should be __int128_t, which is what we check for
in our configure test. (Or __uint128_t I suppose.)

thanks
-- PMM