On 4/12/19 5:11 PM, Ian Romanick wrote:
> On 4/8/19 5:34 AM, Thomas Helland wrote:
>> man. 8. apr. 2019 kl. 06:30 skrev Alyssa Rosenzweig <aly...@rosenzweig.io>:
>>>
>>> On Mali hardware (supported by Panfrost and Lima), the fixed-function
>>> transformation from world-space to screen-space coordinates is done in
>>> the vertex shader prior to writing out the gl_Position varying, rather
>>> than in dedicated hardware. This commit adds a shared NIR pass for
>>> implementing coordinate transformation and lowering gl_Position writes
>>> into screen-space gl_Position writes.
>>>
>>> v2: Run directly on derefs before io/vars are lowered to cleanup the
>>> code substantially. Thank you to Qiang for this suggestion!
>>>
>>> Signed-off-by: Alyssa Rosenzweig <aly...@rosenzweig.io>
>>> Suggested-by: Qiang Yu <yuq...@gmail.com>
>>> Cc: Jason Ekstrand <ja...@jlekstrand.net>
>>> Cc: Eric Anholt <e...@anholt.net>
>>> ---
>>> src/compiler/nir/meson.build | 1 +
>>> src/compiler/nir/nir.h | 1 +
>>> .../nir/nir_lower_viewport_transform.c | 98 +++++++++++++++++++
>>> 3 files changed, 100 insertions(+)
>>> create mode 100644 src/compiler/nir/nir_lower_viewport_transform.c
>>>
>>> diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
>>> index c65f2ff62ff..c274361bdc4 100644
>>> --- a/src/compiler/nir/meson.build
>>> +++ b/src/compiler/nir/meson.build
>>> @@ -151,6 +151,7 @@ files_libnir = files(
>>> 'nir_lower_vars_to_ssa.c',
>>> 'nir_lower_var_copies.c',
>>> 'nir_lower_vec_to_movs.c',
>>> + 'nir_lower_viewport_transform.c',
>>> 'nir_lower_wpos_center.c',
>>> 'nir_lower_wpos_ytransform.c',
>>> 'nir_lower_bit_size.c',
>>> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
>>> index bc72d8f83f5..0f6ed734efa 100644
>>> --- a/src/compiler/nir/nir.h
>>> +++ b/src/compiler/nir/nir.h
>>> @@ -3124,6 +3124,7 @@ void nir_lower_io_to_scalar(nir_shader *shader,
>>> nir_variable_mode mask);
>>> void nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode
>>> mask);
>>> bool nir_lower_io_to_vector(nir_shader *shader, nir_variable_mode mask);
>>>
>>> +void nir_lower_viewport_transform(nir_shader *shader);
>>> bool nir_lower_uniforms_to_ubo(nir_shader *shader, int multiplier);
>>>
>>> typedef struct nir_lower_subgroups_options {
>>> diff --git a/src/compiler/nir/nir_lower_viewport_transform.c
>>> b/src/compiler/nir/nir_lower_viewport_transform.c
>>> new file mode 100644
>>> index 00000000000..9646b72c053
>>> --- /dev/null
>>> +++ b/src/compiler/nir/nir_lower_viewport_transform.c
>>> @@ -0,0 +1,98 @@
>>> +/*
>>> + * Copyright (C) 2019 Alyssa Rosenzweig
>>> + *
>>> + * Permission is hereby granted, free of charge, to any person obtaining a
>>> + * copy of this software and associated documentation files (the
>>> "Software"),
>>> + * to deal in the Software without restriction, including without
>>> limitation
>>> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
>>> + * and/or sell copies of the Software, and to permit persons to whom the
>>> + * Software is furnished to do so, subject to the following conditions:
>>> + *
>>> + * The above copyright notice and this permission notice (including the
>>> next
>>> + * paragraph) shall be included in all copies or substantial portions of
>>> the
>>> + * Software.
>>> + *
>>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
>>> OR
>>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
>>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
>>> OTHER
>>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
>>> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
>>> DEALINGS
>>> + * IN THE SOFTWARE.
>>> + */
>>> +
>>> +/* On some hardware (particularly, all current versions of Mali GPUs),
>>> + * vertex shaders do not output gl_Position in world-space. Instead, they
>>> + * output gl_Position in transformed screen space via the "pseudo"
>>> + * position varying. Thus, this pass finds writes to gl_Position and
>>> + * changes them to transformed writes, still to gl_Position. The
>>> + * outputted screen space is still written back to VARYING_SLOT_POS,
>>> + * which is semantically ambiguous but nevertheless a good match for
>>> + * Gallium/NIR/Mali.
>>> + *
>>> + * Implements coordinate transformation as defined in section 12.5
>>> + * "Coordinate Transformation" of the OpenGL ES 3.2 full specification.
>>> + *
>>> + * This pass must run before lower_vars/lower_io such that derefs are
>>> + * still in place.
>>> + */
>>> +
>>> +#include "nir/nir.h"
>>> +#include "nir/nir_builder.h"
>>> +
>>> +void
>>> +nir_lower_viewport_transform(nir_shader *shader)
>>> +{
>>> + assert(shader->info.stage == MESA_SHADER_VERTEX);
>>> +
>>> + nir_foreach_function(func, shader) {
>>> + nir_foreach_block(block, func->impl) {
>>> + nir_foreach_instr_safe(instr, block) {
>>> + if (instr->type != nir_instr_type_intrinsic) continue;
>>> +
>>> + nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
>>> + if (intr->intrinsic != nir_intrinsic_store_deref) continue;
>>> +
>>> + nir_variable *var = nir_intrinsic_get_var(intr, 0);
>>> + if (var->data.location != VARYING_SLOT_POS) continue;
>>> +
>>
>> I believe it's agreement in mesa that the if ( ... ) should be on one line,
>> and the continue, return, etc should be on a new one.
>>
>> Regards,
>> Thomas Helland
>>
>>> + nir_builder b;
>>> + nir_builder_init(&b, func->impl);
>>> + b.cursor = nir_before_instr(instr);
>>> +
>>> + /* Grab the source and viewport */
>>> + nir_ssa_def *input_point = nir_ssa_for_src(&b, intr->src[1],
>>> 4);
>>> + nir_ssa_def *scale = nir_load_viewport_scale(&b);
>>> + nir_ssa_def *offset = nir_load_viewport_offset(&b);
>>> +
>>> + /* World space to normalised device coordinates to screen
>>> space */
>>> +
>>> + nir_ssa_def *w_recip = nir_frcp(&b, nir_channel(&b,
>>> input_point, 3));
>>> +
>>> + nir_ssa_def *ndc_point = nir_fmul(&b,
>>> + nir_channels(&b, input_point, 0x7), w_recip);
>>> +
>>> + nir_ssa_def *screen = nir_fadd(&b,
>>> + nir_fmul(&b, ndc_point, scale), offset);
>>> +
>>> + /* gl_Position will be written out in screenspace xyz, with w
>>> set to
>>> + * the reciprocal we computed earlier. The transformed w
>>> component is
>>> + * then used for perspective-correct varying interpolation. The
>>> + * transformed w component must preserve its original sign;
>>> this is
>>> + * used in depth clipping computations */
>
> As an even smaller nit to pick... the */ of a multi-line comment should
> be on its own line.
But I see v3 hit the list about half hour ago... Don't worry about this
unless you need a v4 for some other reason.
>>> +
>>> + nir_ssa_def *screen_space = nir_vec4(&b,
>>> + nir_channel(&b, screen, 0),
>>> + nir_channel(&b, screen, 1),
>>> + nir_channel(&b, screen, 2),
>>> + w_recip);
>>> +
>>> + nir_instr_rewrite_src(instr, &intr->src[1],
>>> + nir_src_for_ssa(screen_space));
>>> + }
>>> + }
>>> +
>>> + nir_metadata_preserve(func->impl, nir_metadata_block_index |
>>> + nir_metadata_dominance);
>>> + }
>>> +}
>>> --
>>> 2.20.1
>>>
>>> _______________________________________________
>>> mesa-dev mailing list
>>> mesa-dev@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>> _______________________________________________
>> mesa-dev mailing list
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>>
>
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