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/*
* Copyright © 2015 Red Hat
*
* 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 "nir.h"
#include "nir_builder.h"
/* Lower glBitmap().
*
* This is based on the logic in st_get_bitmap_shader() in TGSI compiler.
* From st_cb_bitmap.c:
*
* glBitmaps are drawn as textured quads. The user's bitmap pattern
* is stored in a texture image. An alpha8 texture format is used.
* The fragment shader samples a bit (texel) from the texture, then
* discards the fragment if the bit is off.
*
* Note that we actually store the inverse image of the bitmap to
* simplify the fragment program. An "on" bit gets stored as texel=0x0
* and an "off" bit is stored as texel=0xff. Then we kill the
* fragment if the negated texel value is less than zero.
*
* Note that the texture format will be, according to what driver supports,
* in order of preference (with swizzle):
*
* I8_UNORM - .xxxx
* A8_UNORM - .000x
* L8_UNORM - .xxx1
*
* If L8_UNORM, options->swizzle_xxxx is true. Otherwise we can just use
* the .w comp.
*
* Run before nir_lower_io.
*/
static nir_variable *
get_texcoord(nir_shader *shader)
{
nir_variable *texcoord = NULL;
/* find gl_TexCoord, if it exists: */
nir_foreach_variable(var, &shader->inputs) {
if (var->data.location == VARYING_SLOT_TEX0) {
texcoord = var;
break;
}
}
/* otherwise create it: */
if (texcoord == NULL) {
texcoord = nir_variable_create(shader,
nir_var_shader_in,
glsl_vec4_type(),
"gl_TexCoord");
texcoord->data.location = VARYING_SLOT_TEX0;
}
return texcoord;
}
static void
lower_bitmap(nir_shader *shader, nir_builder *b,
const nir_lower_bitmap_options *options)
{
nir_ssa_def *texcoord;
nir_tex_instr *tex;
nir_ssa_def *cond;
nir_intrinsic_instr *discard;
texcoord = nir_load_var(b, get_texcoord(shader));
tex = nir_tex_instr_create(shader, 1);
tex->op = nir_texop_tex;
tex->sampler_dim = GLSL_SAMPLER_DIM_2D;
tex->coord_components = 2;
tex->sampler_index = options->sampler;
tex->texture_index = options->sampler;
tex->dest_type = nir_type_float;
tex->src[0].src = nir_src_for_ssa(texcoord);
nir_ssa_dest_init(&tex->instr, &tex->dest, 4, 32, NULL);
nir_builder_instr_insert(b, &tex->instr);
/* kill if tex != 0.0.. take .x or .w channel according to format: */
cond = nir_f2b(b, nir_channel(b, &tex->dest.ssa,
options->swizzle_xxxx ? 0 : 3));
discard = nir_intrinsic_instr_create(shader, nir_intrinsic_discard_if);
discard->src[0] = nir_src_for_ssa(cond);
nir_builder_instr_insert(b, &discard->instr);
shader->info.fs.uses_discard = true;
}
static void
lower_bitmap_impl(nir_function_impl *impl,
const nir_lower_bitmap_options *options)
{
nir_builder b;
nir_builder_init(&b, impl);
b.cursor = nir_before_cf_list(&impl->body);
lower_bitmap(impl->function->shader, &b, options);
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
}
void
nir_lower_bitmap(nir_shader *shader,
const nir_lower_bitmap_options *options)
{
assert(shader->stage == MESA_SHADER_FRAGMENT);
lower_bitmap_impl(nir_shader_get_entrypoint(shader), options);
}
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