Re: [Xen-devel] [PATCH v3 04/25] xen: implement an signed 64 bit division helper function

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.12.11 at 17:30, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> 
> Implement a C function to perform 64 bit signed division and return both
> quotient and remainder.
> Useful as an helper function to implement __aeabi_ldivmod.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> ---
>  xen/common/lib.c |   19 +++++++++++++++++++
>  1 files changed, 19 insertions(+), 0 deletions(-)
> 
> diff --git a/xen/common/lib.c b/xen/common/lib.c
> index 4ae637c..fe831a3 100644
> --- a/xen/common/lib.c
> +++ b/xen/common/lib.c
> @@ -399,6 +399,25 @@ s64 __moddi3(s64 a, s64 b)
>      return (neg ? -urem : urem);
>  }
>  
> +/*
> + * Quotient and remainder of unsigned long long division
> + */
> +s64 __ldivmod_helper(s64 a, s64 b, s64 *r)
> +{
> +    u64 ua, ub, rem, quot;
> +
> +    ua = (a < 0) ? -(u64)a : a;
> +    ub = (b < 0) ? -(u64)b : b;

ABS() in both cases?

Jan

> +    quot = __qdivrem(ua, ub, &rem);
> +    if ( a < 0 )
> +        *r = -rem;
> +    else
> +        *r = rem;
> +    if ( (a < 0) ^ (b < 0) )
> +        return -quot;
> +    else
> +        return quot;
> +}
>  #endif /* BITS_PER_LONG == 32 */
>  
>  /* Compute with 96 bit intermediate result: (a*b)/c */
> -- 
> 1.7.2.5




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