Re: [Xen-devel] [PATCH v3 07/13] x86: Add functions for 64-bit integer arithmetic

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 12/30/2015 10:03 PM, Haozhong Zhang wrote:
> This patch adds several functions to take multiplication, division and
> shifting involving 64-bit integers. Those functions are derived from
> Linux kernel and will be used by later patches to calculate scaling
> ratio and scaled TSC.
>
> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

(although I not sure why you decided to change Linux' code in mul64() below)



> +    c = (u64)rl.l.high + rm.l.low + rn.l.low;
> +    rl.l.high = c;
> +    c >>= 32;
> +    c = c + rm.l.high + rn.l.high + rh.l.low;
> +    rh.l.low = c;
> +    rh.l.high += (u32)(c >> 32);

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