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* Copyright © 2019 Google, Inc.
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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#include "nir_builder.h"
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/* Lowing for fragment shader load_output.
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* This pass supports the blend_equation_advanced, where a fragment
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* shader loads the output (fragcolor) to read the current framebuffer.
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* It does this by lowering the output read to a txf_ms_fb instruction.
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* This instruction works similarly to a normal txf_ms except without
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* taking a texture source argument. (The driver backend is expected
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* to wire this up to a free texture slot which is configured to read
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* from the framebuffer.)
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* This should be run after lower_wpos_ytransform, because the tex
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* coordinates should be the physical fragcoord, not the logical
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* Note that this pass explicitly does *not* add a sampler uniform
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* (as txf_ms_fb does not reference a texture). The driver backend
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* is going to want nif->info.num_textures to include the count of
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* number of textures *not* including the one it inserts to sample
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* from the framebuffer, so it more easily knows where to insert the
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* hidden texture to read from the fb.
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lower_fb_read(nir_builder *b, nir_intrinsic_instr *intr)
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b->cursor = nir_before_instr(&intr->instr);
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nir_ssa_def *fragcoord = nir_load_frag_coord(b);
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nir_ssa_def *sampid = nir_load_sample_id(b);
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fragcoord = nir_f2i32(b, fragcoord);
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nir_tex_instr *tex = nir_tex_instr_create(b->shader, 2);
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tex->op = nir_texop_txf_ms_fb;
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tex->sampler_dim = GLSL_SAMPLER_DIM_2D;
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tex->coord_components = 2;
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tex->dest_type = nir_type_float32;
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tex->src[0].src_type = nir_tex_src_coord;
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tex->src[0].src = nir_src_for_ssa(nir_channels(b, fragcoord, 0x3));
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tex->src[1].src_type = nir_tex_src_ms_index;
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tex->src[1].src = nir_src_for_ssa(sampid);
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nir_ssa_dest_init(&tex->instr, &tex->dest, 4, 32, NULL);
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nir_builder_instr_insert(b, &tex->instr);
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nir_ssa_def_rewrite_uses(&intr->dest.ssa, &tex->dest.ssa);
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nir_lower_fb_read(nir_shader *shader)
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bool progress = false;
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assert(shader->info.stage == MESA_SHADER_FRAGMENT);
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nir_foreach_function(function, shader) {
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nir_function_impl *impl = function->impl;
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nir_foreach_block(block, impl) {
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nir_foreach_instr_safe(instr, block) {
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if (instr->type != nir_instr_type_intrinsic)
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nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
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if (intr->intrinsic != nir_intrinsic_load_output)
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/* TODO KHR_blend_equation_advanced is limited to non-MRT
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* scenarios.. but possible there are other extensions
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* where this pass would be useful that do support MRT?
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* I guess for now I'll leave that as an exercise for the
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if (nir_intrinsic_base(intr) != 0 ||
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nir_src_as_uint(intr->src[0]) != 0)
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nir_builder_init(&b, impl);
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lower_fb_read(&b, intr);
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nir_metadata_preserve(impl, nir_metadata_block_index |
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nir_metadata_dominance);