Sorry I haven't gotten back on this. It got lost somehow.
On Fri, Mar 10, 2017 at 1:56 AM, Iago Toral <ito...@igalia.com> wrote:
> On Thu, 2017-03-09 at 14:05 -0800, Jason Ekstrand wrote:
> > ---
> > src/compiler/nir/nir.h | 4 ++++
> > src/compiler/nir/nir_constant_expressions.py | 16 +++++++++++++++-
> > src/compiler/nir/nir_opcodes.py | 6 +++++-
> > 3 files changed, 24 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> > index 57b8be3..eaa103d 100644
> > --- a/src/compiler/nir/nir.h
> > +++ b/src/compiler/nir/nir.h
> > @@ -105,6 +105,10 @@ typedef enum {
> > typedef union {
> > float f32[4];
> > double f64[4];
> > + int8_t i8[4];
> > + uint8_t u8[4];
> > + int16_t i16[4];
> > + uint16_t u16[4];
> > int32_t i32[4];
> > uint32_t u32[4];
> > int64_t i64[4];
> >
> > diff --git a/src/compiler/nir/nir_constant_expressions.py
> > b/src/compiler/nir/nir_constant_expressions.py
> > index aecca8b..cbda4b1 100644
> > --- a/src/compiler/nir/nir_constant_expressions.py
> > +++ b/src/compiler/nir/nir_constant_expressions.py
> > @@ -14,8 +14,10 @@ def type_size(type_):
> > def type_sizes(type_):
> > if type_has_size(type_):
> > return [type_size(type_)]
> > + elif type_ == 'float':
> > + return [16, 32, 64]
> > else:
> > - return [32, 64]
> > + return [8, 16, 32, 64]
> >
> > def type_add_size(type_, size):
> > if type_has_size(type_):
> > @@ -34,6 +36,8 @@ def op_bit_sizes(op):
> > def get_const_field(type_):
> > if type_ == "bool32":
> > return "u32"
> > + elif type_ == "float16":
> > + return "u16"
>
> I was wondering why not have a f16 field with type float16_t
> in nir_const_value instead, but reading the rest of the patch it seems
> we really want to work with 32-bit floats and then encode results back to
> 16-bit values? Is it because there are some operations that we can't
> implement directly with half-floats?
>
Yes. CPUs cannot, in general, work with 16-bit floats so there is no
actual float16_t type in C. We typedef float to float16_t below just
because it makes the codegen easier. In reality, all 16-bit operations
have to be done in 32-bit with a manual conversion to/from 16-bit float on
both sides.
> Iago
>
> > else:
> > m = type_split_re.match(type_)
> > if not m:
> > @@ -246,6 +250,7 @@ unpack_half_1x16(uint16_t u)
> > }
> >
> > /* Some typed vector structures to make things like src0.y work */
> > +typedef float float16_t;
> > typedef float float32_t;
> > typedef double float64_t;
> > typedef bool bool32_t;
> > @@ -297,6 +302,8 @@ evaluate_${name}(MAYBE_UNUSED unsigned
> > num_components, unsigned bit_size,
> > % for k in range(op.input_sizes[j]):
> > % if input_types[j] == "bool32":
> > _src[${j}].u32[${k}] != 0,
> > + % elif input_types[j] == "float16":
> > + _mesa_half_to_float(_src[${j}].u16[${k}]),
> > % else:
> > _src[${j}].${get_const_field(input_types[j])}[${k}],
> > % endif
> > @@ -322,6 +329,9 @@ evaluate_${name}(MAYBE_UNUSED unsigned
> > num_components, unsigned bit_size,
> > <% continue %>
> > % elif input_types[j] == "bool32":
> > const bool src${j} = _src[${j}].u32[_i] != 0;
> > + % elif input_types[j] == "float16":
> > + const float src${j} =
> > + _mesa_half_to_float(_src[${j}].u16[_i]);
> > % else:
> > const ${input_types[j]}_t src${j} =
> > _src[${j}].${get_const_field(input_types[j])}[_
> > i];
> > @@ -344,6 +354,8 @@ evaluate_${name}(MAYBE_UNUSED unsigned
> > num_components, unsigned bit_size,
> > % if output_type == "bool32":
> > ## Sanitize the C value to a proper NIR bool
> > _dst_val.u32[_i] = dst ? NIR_TRUE : NIR_FALSE;
> > + % elif output_type == "float16":
> > + _dst_val.u16[_i] = _mesa_float_to_half(dst);
> > % else:
> > _dst_val.${get_const_field(output_type)}[_i] = dst;
> > % endif
> > @@ -371,6 +383,8 @@ evaluate_${name}(MAYBE_UNUSED unsigned
> > num_components, unsigned bit_size,
> > % if output_type == "bool32":
> > ## Sanitize the C value to a proper NIR bool
> > _dst_val.u32[${k}] = dst.${"xyzw"[k]} ? NIR_TRUE :
> > NIR_FALSE;
> > + % elif output_type == "float16":
> > + _dst_val.u16[${k}] =
> > _mesa_float_to_half(dst.${"xyzw"[k]});
> > % else:
> > _dst_val.${get_const_field(output_type)}[${k}] =
> > dst.${"xyzw"[k]};
> > % endif
> > diff --git a/src/compiler/nir/nir_opcodes.py
> > b/src/compiler/nir/nir_opcodes.py
> > index 53e9aff..37c655b 100644
> > --- a/src/compiler/nir/nir_opcodes.py
> > +++ b/src/compiler/nir/nir_opcodes.py
> > @@ -175,7 +175,11 @@ for src_t in [tint, tuint, tfloat]:
> > dst_types = [tint, tuint, tfloat]
> >
> > for dst_t in dst_types:
> > - for bit_size in [32, 64]:
> > + if dst_t == tfloat:
> > + bit_sizes = [16, 32, 64]
> > + else:
> > + bit_sizes = [8, 16, 32, 64]
> > + for bit_size in bit_sizes:
> > unop_convert("{}2{}{}".format(src_t[0], dst_t[0],
> > bit_size),
> > dst_t + str(bit_size), src_t, "src0")
> >
>
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