[Mesa-dev] [PATCH 09/29] nir/format_convert: Add pack/unpack for R11F_G11F_B10F

[Pohjolainen, Topi]

On Fri, Jan 26, 2018 at 05:59:38PM -0800, Jason Ekstrand wrote:
> ---
>  src/compiler/nir/nir_format_convert.h | 38 +++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/src/compiler/nir/nir_format_convert.h b/src/compiler/nir/nir_format_convert.h
> index 07618dc..0ffd0db 100644
> --- a/src/compiler/nir/nir_format_convert.h
> +++ b/src/compiler/nir/nir_format_convert.h
> @@ -130,3 +130,41 @@ nir_format_srgb_to_linear(nir_builder *b, nir_ssa_def *c)
>     return nir_fsat(b, nir_bcsel(b, nir_flt(b, c, nir_imm_float(b, 0.04045f)),
>                                     linear, curved));
>  }
> +
> +static inline nir_ssa_def *
> +nir_format_unpack_11f11f10f(nir_builder *b, nir_ssa_def *packed)
> +{
> +   nir_ssa_def *chans[3];
> +   chans[0] = nir_mask_shift(b, packed, 0x000007ff, 4);
> +   chans[1] = nir_mask_shift(b, packed, 0x003ff100, -7);
> +   chans[2] = nir_mask_shift(b, packed, 0xffc00000, -17);
> +
> +   for (unsigned i = 0; i < 3; i++)
> +      chans[i] = nir_unpack_half_2x16_split_x(b, chans[i]);
> +
> +   return nir_vec(b, chans, 3);
> +}
> +
> +static inline nir_ssa_def *
> +nir_format_pack_r11g11b10f(nir_builder *b, nir_ssa_def *color)
> +{
> +   /* 10 and 11-bit floats are unsigned.  Clamp to non-negative */
> +   nir_ssa_def *clamped = nir_fmax(b, color, nir_imm_float(b, 0));
> +
> +   nir_ssa_def *undef = nir_ssa_undef(b, 1, color->bit_size);
> +   nir_ssa_def *p1 = nir_pack_half_2x16_split(b, nir_channel(b, clamped, 0),
> +                                                 nir_channel(b, clamped, 1));
> +   nir_ssa_def *p2 = nir_pack_half_2x16_split(b, nir_channel(b, clamped, 2),
> +                                                 undef);
> +
> +   /* A 10 or 11-bit float has the same exponent as a 16-bit float but with
> +    * fewer exponent bits and no sign bit.  All we have to do is throw away

               mantissa?

> +    * the sign bit and the bottom mantissa bits and shift it into place.
> +    */
> +   nir_ssa_def *packed = nir_imm_int(b, 0);
> +   packed = nir_mask_shift_or(b, packed, p1, 0x00007ff0, -4);
> +   packed = nir_mask_shift_or(b, packed, p1, 0x7ff00000, -9);
> +   packed = nir_mask_shift_or(b, packed, p2, 0x00007ff0, 17);

Shouldn't the mask be 0x00007FE? Otherwise the lowest bit collides with the
exponent bits of green?

> +
> +   return packed;
> +}
> -- 
> 2.5.0.400.gff86faf
> 
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