[Mesa-dev] [PATCH 06/16] nir: improve convert_yuv_to_rgb when fuse_ffma=true

[Jonathan Marek]

Hi,

Did you get a chance try this? If not, I might be able to try it myself 
as I have Intel HW.

On 12/19/18 12:34 PM, Lionel Landwerlin wrote:
> Hey Jonathan,
> 
> I'm kind of curious as to whether we can have a single expression that 
> pretty much generates the same final code (through some of the algebraic 
> lowering/optimizations).
> I'll give it a try on Intel HW, see what it does.
> 
> -
> Lionel
> 
> On 19/12/2018 16:39, Jonathan Marek wrote:
>> When ffma is available, we can use a different arrangement of 
>> constants to
>> get a better result. On freedreno/ir3, this reduces the YUV->RGB to 7
>> scalar ffma. On freedreno/a2xx, it will allow YUV->RGB to be 3 vec4 ffma.
>>
>> Signed-off-by: Jonathan Marek <jonathan at marek.ca>
>> ---
>>   src/compiler/nir/nir_lower_tex.c | 62 ++++++++++++++++++++++----------
>>   1 file changed, 43 insertions(+), 19 deletions(-)
>>
>> diff --git a/src/compiler/nir/nir_lower_tex.c 
>> b/src/compiler/nir/nir_lower_tex.c
>> index 6a6b6c41a7..f7c821bb34 100644
>> --- a/src/compiler/nir/nir_lower_tex.c
>> +++ b/src/compiler/nir/nir_lower_tex.c
>> @@ -342,25 +342,49 @@ convert_yuv_to_rgb(nir_builder *b, nir_tex_instr 
>> *tex,
>>                      nir_ssa_def *y, nir_ssa_def *u, nir_ssa_def *v,
>>                      nir_ssa_def *a)
>>   {
>> -   nir_const_value m[3] = {
>> -      { .f32 = { 1.0f,  0.0f,         1.59602678f, 0.0f } },
>> -      { .f32 = { 1.0f, -0.39176229f, -0.81296764f, 0.0f } },
>> -      { .f32 = { 1.0f,  2.01723214f,  0.0f,        0.0f } }
>> -   };
>> -
>> -   nir_ssa_def *yuv =
>> -      nir_vec4(b,
>> -               nir_fmul(b, nir_imm_float(b, 1.16438356f),
>> -                        nir_fadd(b, y, nir_imm_float(b, -16.0f / 
>> 255.0f))),
>> -               nir_channel(b, nir_fadd(b, u, nir_imm_float(b, -128.0f 
>> / 255.0f)), 0),
>> -               nir_channel(b, nir_fadd(b, v, nir_imm_float(b, -128.0f 
>> / 255.0f)), 0),
>> -               nir_imm_float(b, 0.0));
>> -
>> -   nir_ssa_def *red = nir_fdot4(b, yuv, nir_build_imm(b, 4, 32, m[0]));
>> -   nir_ssa_def *green = nir_fdot4(b, yuv, nir_build_imm(b, 4, 32, 
>> m[1]));
>> -   nir_ssa_def *blue = nir_fdot4(b, yuv, nir_build_imm(b, 4, 32, m[2]));
>> -
>> -   nir_ssa_def *result = nir_vec4(b, red, green, blue, a);
>> +   nir_ssa_def *result;
>> +
>> +
>> +   if (b->shader->options->fuse_ffma) {
>> +      nir_const_value m[4] = {
>> +         { .f32 = { 1.16438356f, 1.16438356f, 1.16438356f, 0.0f } },
>> +         { .f32 = { 0.0f,       -0.39176229f, 2.01723214f, 0.0f } },
>> +         { .f32 = { 1.59602678f,-0.81296764f, 0.0f,        0.0f } },
>> +      };
>> +      static const float y_off = -16.0f * 1.16438356f / 255.0f;
>> +      static const float sc = 128.0f / 255.0f;
>> +
>> +      nir_ssa_def *offset =
>> +         nir_vec4(b,
>> +                  nir_imm_float(b, y_off - sc * 1.59602678f),
>> +                  nir_imm_float(b, y_off + sc * (0.81296764f + 
>> 0.39176229f)),
>> +                  nir_imm_float(b, y_off - sc * 2.01723214f),
>> +                  a);
>> +
>> +      result = nir_ffma(b, y, nir_build_imm(b, 4, 32, m[0]),
>> +                       nir_ffma(b, u, nir_build_imm(b, 4, 32, m[1]),
>> +                                nir_ffma(b, v, nir_build_imm(b, 4, 
>> 32, m[2]), offset)));
>> +   } else {
>> +      nir_const_value m[3] = {
>> +         { .f32 = { 1.0f,  0.0f,         1.59602678f, 0.0f } },
>> +         { .f32 = { 1.0f, -0.39176229f, -0.81296764f, 0.0f } },
>> +         { .f32 = { 1.0f,  2.01723214f,  0.0f,        0.0f } }
>> +      };
>> +
>> +      nir_ssa_def *yuv =
>> +         nir_vec4(b,
>> +                  nir_fmul(b, nir_imm_float(b, 1.16438356f),
>> +                           nir_fadd(b, y, nir_imm_float(b, -16.0f / 
>> 255.0f))),
>> +                  nir_channel(b, nir_fadd(b, u, nir_imm_float(b, 
>> -128.0f / 255.0f)), 0),
>> +                  nir_channel(b, nir_fadd(b, v, nir_imm_float(b, 
>> -128.0f / 255.0f)), 0),
>> +                  nir_imm_float(b, 0.0));
>> +
>> +      nir_ssa_def *red = nir_fdot4(b, yuv, nir_build_imm(b, 4, 32, 
>> m[0]));
>> +      nir_ssa_def *green = nir_fdot4(b, yuv, nir_build_imm(b, 4, 32, 
>> m[1]));
>> +      nir_ssa_def *blue = nir_fdot4(b, yuv, nir_build_imm(b, 4, 32, 
>> m[2]));
>> +
>> +      result = nir_vec4(b, red, green, blue, a);
>> +   }
>>      nir_ssa_def_rewrite_uses(&tex->dest.ssa, nir_src_for_ssa(result));
>>   }
> 
>