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/*
* Copyright © 2015 Intel Corporation
*
* 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.
*/
/*
* Implements a pass that lowers output and/or input variables to a
* temporary plus an output variable with a single copy at each exit
* point of the shader and/or an input variable with a single copy
* at the entrance point of the shader. This way the output variable
* is only ever written once and/or input is only read once, and there
* are no indirect outut/input accesses.
*/
#include "nir.h"
#include "nir_builder.h"
struct lower_io_state {
nir_shader *shader;
nir_function_impl *entrypoint;
struct exec_list old_outputs;
struct exec_list old_inputs;
};
static void
emit_copies(nir_builder *b, struct exec_list *dest_vars,
struct exec_list *src_vars)
{
assert(exec_list_length(dest_vars) == exec_list_length(src_vars));
foreach_two_lists(dest_node, dest_vars, src_node, src_vars) {
nir_variable *dest = exec_node_data(nir_variable, dest_node, node);
nir_variable *src = exec_node_data(nir_variable, src_node, node);
/* No need to copy the contents of a non-fb_fetch_output output variable
* to the temporary allocated for it, since its initial value is
* undefined.
*/
if (src->data.mode == nir_var_shader_out &&
!src->data.fb_fetch_output)
continue;
/* Can't copy the contents of the temporary back to a read-only
* interface variable. The value of the temporary won't have been
* modified by the shader anyway.
*/
if (dest->data.read_only)
continue;
nir_copy_var(b, dest, src);
}
}
static void
emit_output_copies_impl(struct lower_io_state *state, nir_function_impl *impl)
{
nir_builder b;
nir_builder_init(&b, impl);
if (state->shader->info.stage == MESA_SHADER_GEOMETRY) {
/* For geometry shaders, we have to emit the output copies right
* before each EmitVertex call.
*/
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_emit_vertex) {
b.cursor = nir_before_instr(&intrin->instr);
emit_copies(&b, &state->shader->outputs, &state->old_outputs);
}
}
}
} else if (impl == state->entrypoint) {
b.cursor = nir_before_block(nir_start_block(impl));
emit_copies(&b, &state->old_outputs, &state->shader->outputs);
/* For all other shader types, we need to do the copies right before
* the jumps to the end block.
*/
set_foreach(impl->end_block->predecessors, block_entry) {
struct nir_block *block = (void *)block_entry->key;
b.cursor = nir_after_block_before_jump(block);
emit_copies(&b, &state->shader->outputs, &state->old_outputs);
}
}
}
static void
emit_input_copies_impl(struct lower_io_state *state, nir_function_impl *impl)
{
if (impl == state->entrypoint) {
nir_builder b;
nir_builder_init(&b, impl);
b.cursor = nir_before_block(nir_start_block(impl));
emit_copies(&b, &state->old_inputs, &state->shader->inputs);
}
}
static nir_variable *
create_shadow_temp(struct lower_io_state *state, nir_variable *var)
{
nir_variable *nvar = ralloc(state->shader, nir_variable);
memcpy(nvar, var, sizeof *nvar);
/* The original is now the temporary */
nir_variable *temp = var;
/* Reparent the name to the new variable */
ralloc_steal(nvar, nvar->name);
assert(nvar->constant_initializer == NULL);
/* Give the original a new name with @<mode>-temp appended */
const char *mode = (temp->data.mode == nir_var_shader_in) ? "in" : "out";
temp->name = ralloc_asprintf(var, "%s@%s-temp", mode, nvar->name);
temp->data.mode = nir_var_shader_temp;
temp->data.read_only = false;
temp->data.fb_fetch_output = false;
temp->data.compact = false;
return nvar;
}
void
nir_lower_io_to_temporaries(nir_shader *shader, nir_function_impl *entrypoint,
bool outputs, bool inputs)
{
struct lower_io_state state;
if (shader->info.stage == MESA_SHADER_TESS_CTRL)
return;
state.shader = shader;
state.entrypoint = entrypoint;
if (inputs)
exec_list_move_nodes_to(&shader->inputs, &state.old_inputs);
else
exec_list_make_empty(&state.old_inputs);
if (outputs)
exec_list_move_nodes_to(&shader->outputs, &state.old_outputs);
else
exec_list_make_empty(&state.old_outputs);
/* Walk over all of the outputs turn each output into a temporary and
* make a new variable for the actual output.
*/
nir_foreach_variable(var, &state.old_outputs) {
nir_variable *output = create_shadow_temp(&state, var);
exec_list_push_tail(&shader->outputs, &output->node);
}
/* and same for inputs: */
nir_foreach_variable(var, &state.old_inputs) {
nir_variable *input = create_shadow_temp(&state, var);
exec_list_push_tail(&shader->inputs, &input->node);
}
nir_foreach_function(function, shader) {
if (function->impl == NULL)
continue;
if (inputs)
emit_input_copies_impl(&state, function->impl);
if (outputs)
emit_output_copies_impl(&state, function->impl);
nir_metadata_preserve(function->impl, nir_metadata_block_index |
nir_metadata_dominance);
}
exec_list_append(&shader->globals, &state.old_inputs);
exec_list_append(&shader->globals, &state.old_outputs);
nir_fixup_deref_modes(shader);
}
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