Re: [Qemu-devel] [PATCH 02/13] target-ppc: add mask_u128 routine

[Richard Henderson]

On 12/05/2016 03:25 AM, Nikunj A Dadhania wrote:
> +#if defined(CONFIG_INT128)
> +FUNC_MASK(mask_u128, Int128, 128, Int128, ~((__uint128_t)0));
> +#else
> +static inline Int128 mask_u128(int start, int end)
> +{
> +    Int128 r = {0};
> +    if (start > 63) {
> +        r.hi = 0;
> +        r.lo = mask_u64(start - 64, end - 64);
> +    } else if (end < 64) {
> +        r.hi = mask_u64(start, end);
> +        r.lo = 0;
> +    } else {
> +        r.hi = mask_u64(start, 63);
> +        r.lo = mask_u64(0, end - 64);
> +    }
> +    return r;
> +}
>  #endif

First, I would really really like you to stop adding *any* ifdefs on
CONFIG_INT128.  All that's going to do is make sure that there's code that is
almost never tested, since x86_64 (and other 64-bit hosts) does support int128.

Second, you're not using the Int128 interface correctly.  Better would be

static inline Int128 mask_u128(int start, int end)
{
    uint64_t hi, lo;
    if (start > 63) {
        hi = 0;
        lo = mask_u64(start - 64, end - 64);
    } else if (end < 64) {
        hi = mask_u64(start, end);
        lo = 0;
    } else {
        hi = mask_u64(start, 63);
        lo = mask_u64(0, end - 64);
    }
    return make_int128(lo, hi);
}


r~