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/*
* Copyright © 2017 Broadcom
*
* 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.
*/
/**
* @file
*
* Implements GL alpha testing by comparing the output color's alpha to the
* alpha_ref intrinsic and emitting a discard based on it.
*
* The alpha_to_one value overrides the source alpha to 1.0 to implement
* GL_SAMPLE_ALPHA_TO_ONE, which applies before the alpha test (and would be
* rather silly to use with alpha test, but the spec permits).
*/
#include "nir/nir.h"
#include "nir/nir_builder.h"
void
nir_lower_alpha_test(nir_shader *shader, enum compare_func func,
bool alpha_to_one)
{
assert(shader->info.stage == MESA_SHADER_FRAGMENT);
nir_assert_lowered_derefs(shader, nir_lower_load_store_derefs);
nir_foreach_function(function, shader) {
nir_function_impl *impl = function->impl;
nir_builder b;
nir_builder_init(&b, impl);
b.cursor = nir_before_cf_list(&impl->body);
nir_foreach_block(block, impl) {
nir_foreach_instr_safe(instr, block) {
if (instr->type == nir_instr_type_intrinsic) {
nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
nir_variable *out = NULL;
switch (intr->intrinsic) {
case nir_intrinsic_store_var:
out = intr->variables[0]->var;
break;
case nir_intrinsic_store_output:
/* already had i/o lowered.. lookup the matching output var: */
nir_foreach_variable(var, &shader->outputs) {
int drvloc = var->data.driver_location;
if (nir_intrinsic_base(intr) == drvloc) {
out = var;
break;
}
}
assume(out);
break;
default:
continue;
}
if (out->data.mode != nir_var_shader_out)
continue;
if (out->data.location != FRAG_RESULT_COLOR &&
out->data.location != FRAG_RESULT_DATA0)
continue;
b.cursor = nir_before_instr(&intr->instr);
nir_ssa_def *alpha;
if (alpha_to_one) {
alpha = nir_imm_float(&b, 1.0);
} else {
alpha = nir_channel(&b, nir_ssa_for_src(&b, intr->src[0], 4),
3);
}
nir_ssa_def *condition =
nir_compare_func(&b, func,
alpha, nir_load_alpha_ref_float(&b));
nir_intrinsic_instr *discard =
nir_intrinsic_instr_create(b.shader,
nir_intrinsic_discard_if);
discard->num_components = 1;
discard->src[0] = nir_src_for_ssa(nir_inot(&b, condition));
nir_builder_instr_insert(&b, &discard->instr);
shader->info.fs.uses_discard = true;
}
}
}
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
}
}
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