[Mesa-dev] [PATCH 4/4] nir: add ARB_shader_ballot and ARB_shader_group_vote instructions

[Connor Abbott]

On Mon, Jun 5, 2017 at 1:37 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
> I'm not sure how I feel about having these as ALU operations.  ALU
> operations are generally pure functions (with the exception derivative) that
> can be re-ordered at will.  I don't really like breaking that.  In fact, I'd
> almost be inclined to make derivatives intrinsics and just special-case them
> in constant folding.  Thoughts?

I wasn't too sure about this either. It is a little weird to make
these ALU instructions. I followed the rule here that if something can
be constant-folded, it should be an ALU instruction, but I guess you
can argue that it's just a coincidence that these can be
constant-folded anyways. I guess the main downside is that it would be
impossible to make nir_algebraic patterns with these, although I can't
think of too many simple pattern-matching type things you'd want to do
on these instructions anyways. Maybe something like not(any(not(foo)))
-> all(foo) and vice-versa?

>
> On Mon, Jun 5, 2017 at 12:22 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>>
>> Signed-off-by: Connor Abbott <cwabbott0 at gmail.com>
>> ---
>>  src/compiler/nir/nir_intrinsics.h | 14 ++++++++++++++
>>  src/compiler/nir/nir_opcodes.py   | 18 ++++++++++++++++--
>>  2 files changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/compiler/nir/nir_intrinsics.h
>> b/src/compiler/nir/nir_intrinsics.h
>> index 21e7d90..157df7f 100644
>> --- a/src/compiler/nir/nir_intrinsics.h
>> +++ b/src/compiler/nir/nir_intrinsics.h
>> @@ -330,6 +330,20 @@ SYSTEM_VALUE(channel_num, 1, 0, xx, xx, xx)
>>  SYSTEM_VALUE(alpha_ref_float, 1, 0, xx, xx, xx)
>>  SYSTEM_VALUE(layer_id, 1, 0, xx, xx, xx)
>>  SYSTEM_VALUE(view_index, 1, 0, xx, xx, xx)
>> +SYSTEM_VALUE(subgroup_invocation, 1, 0, xx, xx, xx)
>> +
>> +
>> +/* ARB_shader_ballot instructions */
>> +
>> +SYSTEM_VALUE(subgroup_eq_mask, 1, 0, xx, xx, xx)
>> +SYSTEM_VALUE(subgroup_ge_mask, 1, 0, xx, xx, xx)
>> +SYSTEM_VALUE(subgroup_gt_mask, 1, 0, xx, xx, xx)
>> +SYSTEM_VALUE(subgroup_le_mask, 1, 0, xx, xx, xx)
>> +SYSTEM_VALUE(subgroup_lt_mask, 1, 0, xx, xx, xx)
>> +
>> +INTRINSIC(ballot, 1, ARR(0), true, 0, 0, 0, xx, xx, xx,
>> +          NIR_INTRINSIC_CAN_ELIMINATE | NIR_INTRINSIC_CAN_REORDER |
>> +          NIR_INTRINSIC_CROSS_THREAD)
>>
>>  /* Blend constant color values.  Float values are clamped. */
>>  SYSTEM_VALUE(blend_const_color_r_float, 1, 0, xx, xx, xx)
>> diff --git a/src/compiler/nir/nir_opcodes.py
>> b/src/compiler/nir/nir_opcodes.py
>> index be3ab6d..05a80b2 100644
>> --- a/src/compiler/nir/nir_opcodes.py
>> +++ b/src/compiler/nir/nir_opcodes.py
>> @@ -120,8 +120,10 @@ def opcode(name, output_size, output_type,
>> input_sizes, input_types,
>>                            input_types, convergent, cross_thread,
>>                            algebraic_properties, const_expr)
>>
>> -def unop_convert(name, out_type, in_type, const_expr):
>> -   opcode(name, 0, out_type, [0], [in_type], "", const_expr)
>> +def unop_convert(name, out_type, in_type, const_expr, cross_thread=False,
>> +                 convergent=False):
>> +   opcode(name, 0, out_type, [0], [in_type], "", const_expr, convergent,
>> +          cross_thread)
>>
>>  def unop(name, ty, const_expr, convergent=False, cross_thread=False):
>>     opcode(name, 0, ty, [0], [ty], "", const_expr, convergent,
>> cross_thread)
>> @@ -355,6 +357,18 @@ for i in xrange(1, 5):
>>     for j in xrange(1, 5):
>>        unop_horiz("fnoise{0}_{1}".format(i, j), i, tfloat, j, tfloat,
>> "0.0f")
>>
>> +# ARB_shader_ballot instructions
>> +
>> +opcode("read_invocation", 0, tuint, [0, 1], [tuint, tuint32], "", "src0",
>> +        cross_thread=True)
>> +unop("read_first_invocation", tuint, "src0", cross_thread=True)
>> +
>> +# ARB_shader_group_vote instructions
>> +
>> +unop("any_invocations", tbool, "src0", cross_thread=True)
>> +unop("all_invocations", tbool, "src0", cross_thread=True)
>> +unop("all_invocations_equal", tbool, "true", cross_thread=True)
>> +
>>  def binop_convert(name, out_type, in_type, alg_props, const_expr):
>>     opcode(name, 0, out_type, [0, 0], [in_type, in_type], alg_props,
>> const_expr)
>>
>> --
>> 2.9.3
>>
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
>