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/*
* Copyright © 2016 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.
*/
#include "nir.h"
#include "nir_phi_builder.h"
struct repair_ssa_state {
nir_function_impl *impl;
BITSET_WORD *def_set;
struct nir_phi_builder *phi_builder;
bool progress;
};
/* Get ready to build a phi and return the builder */
static struct nir_phi_builder *
prep_build_phi(struct repair_ssa_state *state)
{
const unsigned num_words = BITSET_WORDS(state->impl->num_blocks);
/* We create the phi builder on-demand. */
if (state->phi_builder == NULL) {
state->phi_builder = nir_phi_builder_create(state->impl);
state->def_set = ralloc_array(NULL, BITSET_WORD, num_words);
}
/* We're going to build a phi. That's progress. */
state->progress = true;
/* Set the defs set to empty */
memset(state->def_set, 0, num_words * sizeof(*state->def_set));
return state->phi_builder;
}
static nir_block *
get_src_block(nir_src *src)
{
if (src->parent_instr->type == nir_instr_type_phi) {
return exec_node_data(nir_phi_src, src, src)->pred;
} else {
return src->parent_instr->block;
}
}
static bool
repair_ssa_def(nir_ssa_def *def, void *void_state)
{
struct repair_ssa_state *state = void_state;
bool is_valid = true;
nir_foreach_use(src, def) {
if (nir_block_is_unreachable(get_src_block(src)) ||
!nir_block_dominates(def->parent_instr->block, get_src_block(src))) {
is_valid = false;
break;
}
}
nir_foreach_if_use(src, def) {
nir_block *block_before_if =
nir_cf_node_as_block(nir_cf_node_prev(&src->parent_if->cf_node));
if (nir_block_is_unreachable(block_before_if) ||
!nir_block_dominates(def->parent_instr->block, block_before_if)) {
is_valid = false;
break;
}
}
if (is_valid)
return true;
struct nir_phi_builder *pb = prep_build_phi(state);
BITSET_SET(state->def_set, def->parent_instr->block->index);
struct nir_phi_builder_value *val =
nir_phi_builder_add_value(pb, def->num_components, def->bit_size,
state->def_set);
nir_phi_builder_value_set_block_def(val, def->parent_instr->block, def);
nir_foreach_use_safe(src, def) {
nir_block *src_block = get_src_block(src);
if (nir_block_is_unreachable(src_block) ||
!nir_block_dominates(def->parent_instr->block, src_block)) {
nir_instr_rewrite_src(src->parent_instr, src, nir_src_for_ssa(
nir_phi_builder_value_get_block_def(val, src_block)));
}
}
nir_foreach_if_use_safe(src, def) {
nir_block *block_before_if =
nir_cf_node_as_block(nir_cf_node_prev(&src->parent_if->cf_node));
if (nir_block_is_unreachable(block_before_if) ||
!nir_block_dominates(def->parent_instr->block, block_before_if)) {
nir_if_rewrite_condition(src->parent_if, nir_src_for_ssa(
nir_phi_builder_value_get_block_def(val, block_before_if)));
}
}
return true;
}
bool
nir_repair_ssa_impl(nir_function_impl *impl)
{
struct repair_ssa_state state;
state.impl = impl;
state.phi_builder = NULL;
state.progress = false;
nir_metadata_require(impl, nir_metadata_block_index |
nir_metadata_dominance);
nir_foreach_block(block, impl) {
nir_foreach_instr_safe(instr, block) {
nir_foreach_ssa_def(instr, repair_ssa_def, &state);
}
}
if (state.progress)
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
if (state.phi_builder) {
nir_phi_builder_finish(state.phi_builder);
ralloc_free(state.def_set);
}
return state.progress;
}
/** This pass can be used to repair SSA form in a shader.
*
* Sometimes a transformation (such as return lowering) will have to make
* changes to a shader which, while still correct, break some of NIR's SSA
* invariants. This pass will insert ssa_undefs and phi nodes as needed to
* get the shader back into SSA that the validator will like.
*/
bool
nir_repair_ssa(nir_shader *shader)
{
bool progress = false;
nir_foreach_function(function, shader) {
if (function->impl)
progress = nir_repair_ssa_impl(function->impl) || progress;
}
return progress;
}
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