Re: [Qemu-devel] [PATCH 26/29] target-sparc: store the UA2005 entries in sun4u format

[Richard Henderson]

On 10/01/2016 05:05 AM, Artyom Tarasenko wrote:
> +    sun4u_tte = TTE_PA(sun4v_tte) | (sun4v_tte & TTE_VALID_BIT);
> +    sun4u_tte |= (sun4v_tte & 3ULL) << 61;
> +    sun4u_tte |= (sun4v_tte & TTE_NFO_BIT_UA2005) >> 2;
> +    sun4u_tte |= (sun4v_tte & TTE_USED_BIT_UA2005) >> 6;
> +    sun4u_tte |= (sun4v_tte & TTE_W_OK_BIT_UA2005) >> 5;
> +    sun4u_tte |= (sun4v_tte & TTE_SIDEEFFECT_BIT_UA2005) >> 8;
> +    sun4u_tte |= (sun4v_tte & TTE_PRIV_BIT_UA2005) >> 6;
> +    sun4u_tte |= (sun4v_tte & TTE_LOCKED_BIT_UA2005) >> 55;

I think it might be clearer to use

#define CONVERT_BIT(X, SRC, DST) \
    (SRC > DST ? (X) / (SRC / DST) & (DST) : ((X) & SRC) * (DST / SRC))

  sun4u_tte |= CONVERT_BIT(sun4v_tte, TTE_NFO_BIT_UA2005, TTE_NFO_BIT);

The compiler folds all of the constants down to the same code, but you don't 
have to manually compute the shift counts.


r~