[Mesa-dev] [PATCH 14/28] nir: fix denorms in unpack_half_1x16()

[Samuel Iglesias Gonsálvez]

On 05/12/2018 19:31, Connor Abbott wrote:
> On Wed, Dec 5, 2018 at 4:56 PM Samuel Iglesias Gonsálvez
> <siglesias at igalia.com> wrote:
>>
>> According to VK_KHR_shader_float_controls:
>>
>> "Denormalized values obtained via unpacking an integer into a vector
>>  of values with smaller bit width and interpreting those values as
>>  floating-point numbers must: be flushed to zero, unless the entry point
>>  is declared with the code:DenormPreserve execution mode."
>>
>> Signed-off-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
>> ---
>>  src/compiler/nir/nir_constant_expressions.py | 13 +++++++++++++
>>  src/compiler/nir/nir_lower_alu_to_scalar.c   | 10 ++++++++--
>>  src/compiler/nir/nir_opcodes.py              |  5 +++++
>>  3 files changed, 26 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/compiler/nir/nir_constant_expressions.py b/src/compiler/nir/nir_constant_expressions.py
>> index a9af1bd233d..bc60a08da28 100644
>> --- a/src/compiler/nir/nir_constant_expressions.py
>> +++ b/src/compiler/nir/nir_constant_expressions.py
>> @@ -245,6 +245,19 @@ pack_half_1x16(float x)
>>     return _mesa_float_to_half(x);
>>  }
>>
>> +/**
>> + * Evaluate one component of unpackHalf2x16.
>> + */
>> +static float
>> +unpack_half_1x16_flush_to_zero(uint16_t u)
>> +{
>> +   if (u < 0x0400)
>> +      u = 0;
>> +   if (u & 0x8000 && !(u & 0x7c00))
>> +      u = 0x8000;
>> +   return _mesa_half_to_float(u);
>> +}
>> +
>>  /**
>>   * Evaluate one component of unpackHalf2x16.
>>   */
>> diff --git a/src/compiler/nir/nir_lower_alu_to_scalar.c b/src/compiler/nir/nir_lower_alu_to_scalar.c
>> index 7ef032cd164..d80cf2504c7 100644
>> --- a/src/compiler/nir/nir_lower_alu_to_scalar.c
>> +++ b/src/compiler/nir/nir_lower_alu_to_scalar.c
>> @@ -133,8 +133,14 @@ lower_alu_instr_scalar(nir_alu_instr *instr, nir_builder *b)
>>        nir_ssa_def *packed = nir_ssa_for_alu_src(b, instr, 0);
>>
>>        nir_ssa_def *comps[2];
>> -      comps[0] = nir_unpack_half_2x16_split_x(b, packed);
>> -      comps[1] = nir_unpack_half_2x16_split_y(b, packed);
>> +
>> +      if (b->shader->info.shader_float_controls_execution_mode & SHADER_DENORM_FLUSH_TO_ZERO_FP16) {
>> +         comps[0] = nir_unpack_half_2x16_split_x_flush_to_zero(b, packed);
>> +         comps[1] = nir_unpack_half_2x16_split_y_flush_to_zero(b, packed);
> 
> This feels a little wrong... I think either we should add a
> nir_op_unpack_half_2x16_flush_to_zero, or we shouldn't be changing
> this here. We should be consistent on whether the flushing behavior is
> implied by the environment or specified by the opcode.
> 

Right, I am going to add it.

Thanks!

Sam

>> +      } else {
>> +         comps[0] = nir_unpack_half_2x16_split_x(b, packed);
>> +         comps[1] = nir_unpack_half_2x16_split_y(b, packed);
>> +      }
>>        nir_ssa_def *vec = nir_vec(b, comps, 2);
>>
>>        nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa, nir_src_for_ssa(vec));
>> diff --git a/src/compiler/nir/nir_opcodes.py b/src/compiler/nir/nir_opcodes.py
>> index eb554a66b44..191025f6932 100644
>> --- a/src/compiler/nir/nir_opcodes.py
>> +++ b/src/compiler/nir/nir_opcodes.py
>> @@ -309,6 +309,11 @@ unop_convert("unpack_half_2x16_split_x", tfloat32, tuint32,
>>  unop_convert("unpack_half_2x16_split_y", tfloat32, tuint32,
>>               "unpack_half_1x16((uint16_t)(src0 >> 16))")
>>
>> +unop_convert("unpack_half_2x16_split_x_flush_to_zero", tfloat32, tuint32,
>> +             "unpack_half_1x16_flush_to_zero((uint16_t)(src0 & 0xffff))")
>> +unop_convert("unpack_half_2x16_split_y_flush_to_zero", tfloat32, tuint32,
>> +             "unpack_half_1x16_flush_to_zero((uint16_t)(src0 >> 16))")
>> +
>>  unop_convert("unpack_32_2x16_split_x", tuint16, tuint32, "src0")
>>  unop_convert("unpack_32_2x16_split_y", tuint16, tuint32, "src0 >> 16")
>>
>> --
>> 2.19.1
>>
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> 

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