[Mesa-dev] [PATCH 3/9] i965: fix 64-bit immediates in brw_inst(_set)_bits

[Kristian Høgsberg]

On Thu, Nov 19, 2015 at 2:05 AM, Iago Toral Quiroga <itoral at igalia.com> wrote:
> From: Connor Abbott <connor.w.abbott at intel.com>
>
> If we tried to get/set something that was exactly 64 bits, we would
> try to do (1 << 64) - 1 to calculate the mask which doesn't give us all
> 1's like we want.
>
> v2 (Iago)
>  - Replace ~0 by ~0ull
>  - Removed unnecessary parenthesis
>
> Reviewed-by: Iago Toral Quiroga <itoral at igalia.com>
> ---
>  src/mesa/drivers/dri/i965/brw_inst.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_inst.h b/src/mesa/drivers/dri/i965/brw_inst.h
> index 4ed95c4..ec08194 100644
> --- a/src/mesa/drivers/dri/i965/brw_inst.h
> +++ b/src/mesa/drivers/dri/i965/brw_inst.h
> @@ -694,7 +694,8 @@ brw_inst_bits(const brw_inst *inst, unsigned high, unsigned low)
>     high %= 64;
>     low %= 64;
>
> -   const uint64_t mask = (1ull << (high - low + 1)) - 1;
> +   const uint64_t mask = (high - low == 63) ? ~0ull :
> +      (1ull << (high - low + 1)) - 1;

Can we do

const uint64_t mask = (~0ul >> (64 - (high - low + 1)));

instead?

Kristian

>     return (inst->data[word] >> low) & mask;
>  }
> @@ -713,7 +714,8 @@ brw_inst_set_bits(brw_inst *inst, unsigned high, unsigned low, uint64_t value)
>     high %= 64;
>     low %= 64;
>
> -   const uint64_t mask = ((1ull << (high - low + 1)) - 1) << low;
> +   const uint64_t mask = (high - low == 63) ? ~0ull :
> +      ((1ull << (high - low + 1)) - 1) << low;
>
>     /* Make sure the supplied value actually fits in the given bitfield. */
>     assert((value & (mask >> low)) == value);
> --
> 1.9.1
>
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