[Mesa-stable] [Mesa-dev] [PATCH 24/53] st/nine: Handle RSQ special cases

[Ilia Mirkin]

On Wed, Jan 7, 2015 at 11:36 AM, Axel Davy <axel.davy at ens.fr> wrote:
> We should use the absolute value of the input as input to ureg_RSQ.
>
> Moreover, an input of 0.0 should return FLT_MAX.
>
> Reviewed-by: David Heidelberg <david at ixit.cz>
> Signed-off-by: Axel Davy <axel.davy at ens.fr>
>
> Cc: "10.4" <mesa-stable at lists.freedesktop.org>
> ---
>  src/gallium/state_trackers/nine/nine_shader.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/src/gallium/state_trackers/nine/nine_shader.c b/src/gallium/state_trackers/nine/nine_shader.c
> index da77da5..4dee5f5 100644
> --- a/src/gallium/state_trackers/nine/nine_shader.c
> +++ b/src/gallium/state_trackers/nine/nine_shader.c
> @@ -1957,6 +1957,17 @@ DECL_SPECIAL(POW)
>      return D3D_OK;
>  }
>
> +DECL_SPECIAL(RSQ)
> +{
> +    struct ureg_program *ureg = tx->ureg;
> +    struct ureg_dst dst = tx_dst_param(tx, &tx->insn.dst[0]);
> +    struct ureg_src src = tx_src_param(tx, &tx->insn.src[0]);
> +    struct ureg_dst tmp = tx_scratch(tx);
> +    ureg_RSQ(ureg, tmp, ureg_abs(src));
> +    ureg_MIN(ureg, dst, ureg_imm1f(ureg, FLT_MAX), ureg_src(tmp));

When would this MIN not return the value in tmp? In the description
you say that RSQ(0.0) should return FLT_MAX... is the theory that
MIN(NaN, FLT_MAX) == FLT_MAX? Is RSQ(0) in tgsi defined to return NaN?

  -ilia