[Mesa-dev] [PATCH] gallium/tgsi: correct typo propagated from NV_vertex_program1_1

[Brian Paul]

On 02/06/2014 09:09 AM, Erik Faye-Lund wrote:
> In the specification text of NV_vertex_program1_1, the upper
> limit of the RCC instruction is written as 1.884467e+19 in
> scientific notation, but as 0x5F800000 in binary. But the binary
> version translates to 1.84467e+19 rather than 1.884467e+19 in
> scientific notation.
>
> Since the lower-limit equals 2^-64 and the binary version equals
> 2^+64, let's assume the value in scientific notation is a typo
> and implement this using the value from the binary version
> instead.
>
> Signed-off-by: Erik Faye-Lund <kusmabite at gmail.com>
> ---
>
> I've also e-mailed NVIDIA's contact as listed in the specification,
> but I haven't gotten any reply yet.
>
> I think it's pretty obvious, though. I seriously doubt anyone
> implemented the old limit, as it would require quite a bit more
> gates AFAIK.
>
>   src/gallium/auxiliary/tgsi/tgsi_exec.c | 8 ++++----
>   src/gallium/docs/source/tgsi.rst       | 2 +-
>   2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/src/gallium/auxiliary/tgsi/tgsi_exec.c b/src/gallium/auxiliary/tgsi/tgsi_exec.c
> index 3d37eaa..7d35aeb 100644
> --- a/src/gallium/auxiliary/tgsi/tgsi_exec.c
> +++ b/src/gallium/auxiliary/tgsi/tgsi_exec.c
> @@ -915,8 +915,8 @@ micro_rcc(union tgsi_exec_channel *dst,
>         float recip = 1.0f / src->f[i];
>
>         if (recip > 0.0f) {
> -         if (recip > 1.884467e+019f) {
> -            dst->f[i] = 1.884467e+019f;
> +         if (recip > 1.84467e+019f) {
> +            dst->f[i] = 1.84467e+019f;
>            }
>            else if (recip < 5.42101e-020f) {
>               dst->f[i] = 5.42101e-020f;
> @@ -926,8 +926,8 @@ micro_rcc(union tgsi_exec_channel *dst,
>            }
>         }
>         else {
> -         if (recip < -1.884467e+019f) {
> -            dst->f[i] = -1.884467e+019f;
> +         if (recip < -1.84467e+019f) {
> +            dst->f[i] = -1.84467e+019f;
>            }
>            else if (recip > -5.42101e-020f) {
>               dst->f[i] = -5.42101e-020f;

As long as you're at it, this code should probably be rewritten in terms 
of the CLAMP() macro to be more concise.


> diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
> index 0501aca..be42572 100644
> --- a/src/gallium/docs/source/tgsi.rst
> +++ b/src/gallium/docs/source/tgsi.rst
> @@ -424,7 +424,7 @@ XXX cleanup on aisle three
>
>   .. math::
>
> -  dst = (1 / src.x) > 0 ? clamp(1 / src.x, 5.42101e-020, 1.884467e+019) : clamp(1 / src.x, -1.884467e+019, -5.42101e-020)
> +  dst = (1 / src.x) > 0 ? clamp(1 / src.x, 5.42101e-020, 1.84467e+019) : clamp(1 / src.x, -1.84467e+019, -5.42101e-020)
>
>
>   .. opcode:: DPH - Homogeneous Dot Product
>

Looks OK otherwise to me.

-Brian