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/*
* Copyright © 2021 Advanced Micro Devices, Inc.
*
* 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"
/**
* This pass removes no-op assignment to gl_FragDepth.
*
* gl_FragDepth implicit value is gl_FragCoord.z, so if a shader only assign
* this value to gl_FragDepth, the store instruction is removed.
*/
static bool
ssa_def_is_source_depth(nir_ssa_def *def)
{
nir_ssa_scalar scalar = nir_ssa_scalar_resolved(def, 0);
nir_instr *instr = scalar.def->parent_instr;
if (instr->type != nir_instr_type_intrinsic)
return false;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
if (intrin->intrinsic != nir_intrinsic_load_frag_coord)
return false;
/* Depth is gl_FragCoord.z */
return scalar.comp == 2;
}
bool
nir_opt_fragdepth(nir_shader *shader)
{
bool progress = false;
nir_intrinsic_instr *store_intrin = NULL;
if (shader->info.stage != MESA_SHADER_FRAGMENT)
goto end;
nir_function_impl *impl = nir_shader_get_entrypoint(shader);
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
if (intrin->intrinsic != nir_intrinsic_store_deref &&
intrin->intrinsic != nir_intrinsic_store_output)
continue;
unsigned data_src;
if (intrin->intrinsic == nir_intrinsic_store_deref) {
nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
if (!nir_deref_mode_is(deref, nir_var_shader_out))
continue;
nir_variable *var = nir_deref_instr_get_variable(deref);
if (var->data.location != FRAG_RESULT_DEPTH)
continue;
data_src = 1;
} else {
nir_io_semantics sem = nir_intrinsic_io_semantics(intrin);
if (sem.location != FRAG_RESULT_DEPTH)
continue;
data_src = 0;
}
/* We found a write to gl_FragDepth */
if (store_intrin) {
/* This isn't the only write: give up on this optimization */
goto end;
} else {
if (ssa_def_is_source_depth(intrin->src[data_src].ssa)) {
/* We're writing gl_FragCoord.z in gl_FragDepth: remember
* intrin so we can try to remove it later. */
store_intrin = intrin;
} else {
/* We're writing something else: give up. */
goto end;
}
}
}
}
if (store_intrin) {
/* Found a single store to gl_FragDepth, and it writes gl_FragCoord.z to it.
* Remove it since that's the implicit value of gl_FragDepth.
*/
nir_instr_remove(&store_intrin->instr);
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance |
nir_metadata_loop_analysis |
nir_metadata_instr_index);
progress = true;
}
end:
if (!progress)
nir_shader_preserve_all_metadata(shader);
return progress;
}
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