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* Copyright © 2015 Red Hat
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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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* This is based on the logic in st_get_bitmap_shader() in TGSI compiler.
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* From st_cb_bitmap.c:
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* glBitmaps are drawn as textured quads. The user's bitmap pattern
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* is stored in a texture image. An alpha8 texture format is used.
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* The fragment shader samples a bit (texel) from the texture, then
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* discards the fragment if the bit is off.
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* Note that we actually store the inverse image of the bitmap to
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* simplify the fragment program. An "on" bit gets stored as texel=0x0
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* and an "off" bit is stored as texel=0xff. Then we kill the
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* fragment if the negated texel value is less than zero.
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* Note that the texture format will be, according to what driver supports,
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* in order of preference (with swizzle):
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* If L8_UNORM, options->swizzle_xxxx is true. Otherwise we can just use
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* Run before nir_lower_io.
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get_texcoord(nir_shader *shader)
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nir_variable *texcoord =
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nir_find_variable_with_location(shader, nir_var_shader_in,
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/* otherwise create it: */
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if (texcoord == NULL) {
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texcoord = nir_variable_create(shader,
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texcoord->data.location = VARYING_SLOT_TEX0;
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lower_bitmap(nir_shader *shader, nir_builder *b,
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const nir_lower_bitmap_options *options)
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nir_ssa_def *texcoord;
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texcoord = nir_load_var(b, get_texcoord(shader));
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const struct glsl_type *sampler2D =
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glsl_sampler_type(GLSL_SAMPLER_DIM_2D, false, false, GLSL_TYPE_FLOAT);
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nir_variable *tex_var =
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nir_variable_create(shader, nir_var_uniform, sampler2D, "bitmap_tex");
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tex_var->data.binding = options->sampler;
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tex_var->data.explicit_binding = true;
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tex_var->data.how_declared = nir_var_hidden;
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nir_deref_instr *tex_deref = nir_build_deref_var(b, tex_var);
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tex = nir_tex_instr_create(shader, 3);
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tex->op = nir_texop_tex;
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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_texture_deref;
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tex->src[0].src = nir_src_for_ssa(&tex_deref->dest.ssa);
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tex->src[1].src_type = nir_tex_src_sampler_deref;
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tex->src[1].src = nir_src_for_ssa(&tex_deref->dest.ssa);
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tex->src[2].src_type = nir_tex_src_coord;
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nir_src_for_ssa(nir_channels(b, texcoord,
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(1 << tex->coord_components) - 1));
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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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/* kill if tex != 0.0.. take .x or .w channel according to format: */
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cond = nir_f2b(b, nir_channel(b, &tex->dest.ssa,
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options->swizzle_xxxx ? 0 : 3));
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nir_discard_if(b, cond);
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shader->info.fs.uses_discard = true;
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lower_bitmap_impl(nir_function_impl *impl,
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const nir_lower_bitmap_options *options)
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nir_builder_init(&b, impl);
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b.cursor = nir_before_cf_list(&impl->body);
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lower_bitmap(impl->function->shader, &b, options);
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nir_metadata_preserve(impl, nir_metadata_block_index |
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nir_metadata_dominance);
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nir_lower_bitmap(nir_shader *shader,
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const nir_lower_bitmap_options *options)
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assert(shader->info.stage == MESA_SHADER_FRAGMENT);
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lower_bitmap_impl(nir_shader_get_entrypoint(shader), options);