[Mesa-dev] [PATCH 10/29] nir/format_convert: Add a function to pack RGB9_E5 formats

[Pohjolainen, Topi]

On Fri, Jan 26, 2018 at 05:59:39PM -0800, Jason Ekstrand wrote:
> ---
>  src/compiler/nir/nir_format_convert.h | 64 +++++++++++++++++++++++++++++++++++
>  1 file changed, 64 insertions(+)

I didn't check against any specs but this looks to match
format_rgb9e5.h::float3_to_rgb9e5().

Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>

> 
> diff --git a/src/compiler/nir/nir_format_convert.h b/src/compiler/nir/nir_format_convert.h
> index 0ffd0db..479191e 100644
> --- a/src/compiler/nir/nir_format_convert.h
> +++ b/src/compiler/nir/nir_format_convert.h
> @@ -23,6 +23,8 @@
>  
>  #include "nir_builder.h"
>  
> +#include "util/format_rgb9e5.h"
> +
>  static inline nir_ssa_def *
>  nir_shift(nir_builder *b, nir_ssa_def *value, int left_shift)
>  {
> @@ -168,3 +170,65 @@ nir_format_pack_r11g11b10f(nir_builder *b, nir_ssa_def *color)
>  
>     return packed;
>  }
> +
> +static inline nir_ssa_def *
> +nir_format_pack_r9g9b9e5(nir_builder *b, nir_ssa_def *color)
> +{
> +   /* See also float3_to_rgb9e5 */
> +
> +   /* First, we need to clamp it to range. */
> +   nir_ssa_def *clamped = nir_fmin(b, color, nir_imm_float(b, MAX_RGB9E5));
> +
> +   /* Get rid of negatives and NaN */
> +   clamped = nir_bcsel(b, nir_ult(b, nir_imm_int(b, 0x7f800000), color),
> +                          nir_imm_float(b, 0), clamped);
> +
> +   /* maxrgb.u = MAX3(rc.u, gc.u, bc.u); */
> +   nir_ssa_def *maxu = nir_umax(b, nir_channel(b, clamped, 0),
> +                       nir_umax(b, nir_channel(b, clamped, 1),
> +                                   nir_channel(b, clamped, 2)));
> +
> +   /* maxrgb.u += maxrgb.u & (1 << (23-9)); */
> +   maxu = nir_iadd(b, maxu, nir_iand(b, maxu, nir_imm_int(b, 1 << 14)));
> +
> +   /* exp_shared = MAX2((maxrgb.u >> 23), -RGB9E5_EXP_BIAS - 1 + 127) +
> +    *              1 + RGB9E5_EXP_BIAS - 127;
> +    */
> +   nir_ssa_def *exp_shared =
> +      nir_iadd(b, nir_umax(b, nir_ushr(b, maxu, nir_imm_int(b, 23)),
> +                              nir_imm_int(b, -RGB9E5_EXP_BIAS - 1 + 127)),
> +                  nir_imm_int(b, 1 + RGB9E5_EXP_BIAS - 127));
> +
> +   /* revdenom_biasedexp = 127 - (exp_shared - RGB9E5_EXP_BIAS -
> +    *                             RGB9E5_MANTISSA_BITS) + 1;
> +    */
> +   nir_ssa_def *revdenom_biasedexp =
> +      nir_isub(b, nir_imm_int(b, 127 + RGB9E5_EXP_BIAS +
> +                                 RGB9E5_MANTISSA_BITS + 1),
> +                  exp_shared);
> +
> +   /* revdenom.u = revdenom_biasedexp << 23; */
> +   nir_ssa_def *revdenom =
> +      nir_ishl(b, revdenom_biasedexp, nir_imm_int(b, 23));
> +
> +   /* rm = (int) (rc.f * revdenom.f);
> +    * gm = (int) (gc.f * revdenom.f);
> +    * bm = (int) (bc.f * revdenom.f);
> +    */
> +   nir_ssa_def *mantissa =
> +      nir_f2i32(b, nir_fmul(b, clamped, revdenom));
> +
> +   /* rm = (rm & 1) + (rm >> 1);
> +    * gm = (gm & 1) + (gm >> 1);
> +    * bm = (bm & 1) + (bm >> 1);
> +    */
> +   mantissa = nir_iadd(b, nir_iand(b, mantissa, nir_imm_int(b, 1)),
> +                          nir_ushr(b, mantissa, nir_imm_int(b, 1)));
> +
> +   nir_ssa_def *packed = nir_channel(b, mantissa, 0);
> +   packed = nir_mask_shift_or(b, packed, nir_channel(b, mantissa, 1), ~0, 9);
> +   packed = nir_mask_shift_or(b, packed, nir_channel(b, mantissa, 2), ~0, 18);
> +   packed = nir_mask_shift_or(b, packed, exp_shared, ~0, 27);
> +
> +   return packed;
> +}
> -- 
> 2.5.0.400.gff86faf
> 
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