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/*
* © Copyright 2018 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.
*
*/
#include <stdio.h>
#include "pan_blend_shaders.h"
#include "pan_util.h"
#include "midgard/midgard_compile.h"
#include "compiler/nir/nir_builder.h"
#include "nir/nir_lower_blend.h"
#include "gallium/auxiliary/util/u_blend.h"
#include "util/u_memory.h"
/*
* Implements the command stream portion of programmatic blend shaders.
*
* On Midgard, common blending operations are accelerated by the fixed-function
* blending pipeline. Panfrost supports this fast path via the code in
* pan_blending.c. Nevertheless, uncommon blend modes (including some seemingly
* simple modes present in ES2) require "blend shaders", a special internal
* shader type used for programmable blending.
*
* Blend shaders operate during the normal blending time, but they bypass the
* fixed-function blending pipeline and instead go straight to the Midgard
* shader cores. The shaders themselves are essentially just fragment shaders,
* making heavy use of uint8 arithmetic to manipulate RGB values for the
* framebuffer.
*
* As is typical with Midgard, shader binaries must be accompanied by
* information about the first tag (ORed with the bottom nibble of address,
* like usual) and work registers. Work register count is specified in the
* blend descriptor, as well as in the coresponding fragment shader's work
* count. This suggests that blend shader invocation is tied to fragment shader
* execution.
*
* ---
*
* As for blend shaders, they use the standard ISA.
*
* The source pixel colour, including alpha, is preloaded into r0 as a vec4 of
* float32.
*
* The destination pixel colour must be loaded explicitly via load/store ops.
* TODO: Investigate.
*
* They use fragment shader writeout; however, instead of writing a vec4 of
* float32 for RGBA encoding, we writeout a vec4 of uint8, using 8-bit imov
* instead of 32-bit fmov. The net result is that r0 encodes a single uint32
* containing all four channels of the color. Accordingly, the blend shader
* epilogue has to scale all four channels by 255 and then type convert to a
* uint8.
*
* ---
*
* Blend shaders hardcode constants. Naively, this requires recompilation each
* time the blend color changes, which is a performance risk. Accordingly, we
* 'cheat' a bit: instead of loading the constant, we compile a shader with a
* dummy constant, exporting the offset to the immediate in the shader binary,
* storing this generic binary and metadata in the CSO itself at CSO create
* time.
*
* We then hot patch in the color into this shader at attachment / color change
* time, allowing for CSO create to be the only expensive operation
* (compilation).
*/
static nir_lower_blend_options
nir_make_options(const struct pipe_blend_state *blend, unsigned i)
{
nir_lower_blend_options options;
if (blend->logicop_enable) {
options.logicop_enable = true;
options.logicop_func = blend->logicop_func;
return options;
}
options.logicop_enable = false;
/* If blend is disabled, we just use replace mode */
nir_lower_blend_channel rgb = {
.func = BLEND_FUNC_ADD,
.src_factor = BLEND_FACTOR_ZERO,
.invert_src_factor = true,
.dst_factor = BLEND_FACTOR_ZERO,
.invert_dst_factor = false
};
nir_lower_blend_channel alpha = rgb;
if (blend->rt[i].blend_enable) {
rgb.func = util_blend_func_to_shader(blend->rt[i].rgb_func);
rgb.src_factor = util_blend_factor_to_shader(blend->rt[i].rgb_src_factor);
rgb.dst_factor = util_blend_factor_to_shader(blend->rt[i].rgb_dst_factor);
rgb.invert_src_factor = util_blend_factor_is_inverted(blend->rt[i].rgb_src_factor);
rgb.invert_dst_factor = util_blend_factor_is_inverted(blend->rt[i].rgb_dst_factor);
alpha.func = util_blend_func_to_shader(blend->rt[i].alpha_func);
alpha.src_factor = util_blend_factor_to_shader(blend->rt[i].alpha_src_factor);
alpha.dst_factor = util_blend_factor_to_shader(blend->rt[i].alpha_dst_factor);
alpha.invert_src_factor = util_blend_factor_is_inverted(blend->rt[i].alpha_src_factor);
alpha.invert_dst_factor = util_blend_factor_is_inverted(blend->rt[i].alpha_dst_factor);
}
options.rgb = rgb;
options.alpha = alpha;
options.colormask = blend->rt[i].colormask;
return options;
}
struct panfrost_blend_shader
panfrost_compile_blend_shader(
struct panfrost_context *ctx,
struct pipe_blend_state *cso,
enum pipe_format format,
unsigned rt)
{
struct panfrost_screen *screen = pan_screen(ctx->base.screen);
struct panfrost_blend_shader res;
res.ctx = ctx;
/* Build the shader */
nir_shader *shader = nir_shader_create(NULL, MESA_SHADER_FRAGMENT, &midgard_nir_options, NULL);
nir_function *fn = nir_function_create(shader, "main");
nir_function_impl *impl = nir_function_impl_create(fn);
/* Create the blend variables */
nir_variable *c_src = nir_variable_create(shader, nir_var_shader_in, glsl_vector_type(GLSL_TYPE_FLOAT, 4), "gl_Color");
nir_variable *c_out = nir_variable_create(shader, nir_var_shader_out, glsl_vector_type(GLSL_TYPE_FLOAT, 4), "gl_FragColor");
c_src->data.location = VARYING_SLOT_COL0;
c_out->data.location = FRAG_RESULT_COLOR;
/* Setup nir_builder */
nir_builder _b;
nir_builder *b = &_b;
nir_builder_init(b, impl);
b->cursor = nir_before_block(nir_start_block(impl));
/* Setup inputs */
nir_ssa_def *s_src = nir_load_var(b, c_src);
/* Build a trivial blend shader */
nir_store_var(b, c_out, s_src, 0xFF);
nir_lower_blend_options options =
nir_make_options(cso, rt);
NIR_PASS_V(shader, nir_lower_blend, options);
NIR_PASS_V(shader, nir_lower_framebuffer, format, screen->gpu_id);
/* Compile the built shader */
midgard_program program;
midgard_compile_shader_nir(shader, &program, true, rt, screen->gpu_id, false);
/* Allow us to patch later */
res.patch_index = program.blend_patch_offset;
res.first_tag = program.first_tag;
res.size = program.compiled.size;
res.buffer = program.compiled.data;
return res;
}
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