974 lines
33 KiB
C
974 lines
33 KiB
C
/*
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* Copyright © 2014 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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* Authors:
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* Jason Ekstrand (jason@jlekstrand.net)
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*
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*/
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#include "nir.h"
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#include "nir_builder.h"
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#include "nir_vla.h"
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struct deref_node {
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struct deref_node *parent;
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const struct glsl_type *type;
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bool lower_to_ssa;
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/* Only valid for things that end up in the direct list.
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* Note that multiple nir_deref_vars may correspond to this node, but they
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* will all be equivalent, so any is as good as the other.
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*/
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nir_deref_var *deref;
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struct exec_node direct_derefs_link;
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struct set *loads;
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struct set *stores;
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struct set *copies;
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nir_ssa_def **def_stack;
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nir_ssa_def **def_stack_tail;
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struct deref_node *wildcard;
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struct deref_node *indirect;
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struct deref_node *children[0];
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};
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struct lower_variables_state {
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nir_shader *shader;
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void *dead_ctx;
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nir_function_impl *impl;
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/* A hash table mapping variables to deref_node data */
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struct hash_table *deref_var_nodes;
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/* A hash table mapping fully-qualified direct dereferences, i.e.
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* dereferences with no indirect or wildcard array dereferences, to
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* deref_node data.
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*
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* At the moment, we only lower loads, stores, and copies that can be
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* trivially lowered to loads and stores, i.e. copies with no indirects
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* and no wildcards. If a part of a variable that is being loaded from
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* and/or stored into is also involved in a copy operation with
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* wildcards, then we lower that copy operation to loads and stores, but
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* otherwise we leave copies with wildcards alone. Since the only derefs
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* used in these loads, stores, and trivial copies are ones with no
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* wildcards and no indirects, these are precisely the derefs that we
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* can actually consider lowering.
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*/
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struct exec_list direct_deref_nodes;
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/* Controls whether get_deref_node will add variables to the
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* direct_deref_nodes table. This is turned on when we are initially
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* scanning for load/store instructions. It is then turned off so we
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* don't accidentally change the direct_deref_nodes table while we're
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* iterating throug it.
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*/
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bool add_to_direct_deref_nodes;
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/* A hash table mapping phi nodes to deref_state data */
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struct hash_table *phi_table;
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};
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static struct deref_node *
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deref_node_create(struct deref_node *parent,
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const struct glsl_type *type, nir_shader *shader)
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{
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size_t size = sizeof(struct deref_node) +
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glsl_get_length(type) * sizeof(struct deref_node *);
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struct deref_node *node = rzalloc_size(shader, size);
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node->type = type;
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node->parent = parent;
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node->deref = NULL;
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exec_node_init(&node->direct_derefs_link);
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return node;
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}
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/* Returns the deref node associated with the given variable. This will be
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* the root of the tree representing all of the derefs of the given variable.
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*/
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static struct deref_node *
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get_deref_node_for_var(nir_variable *var, struct lower_variables_state *state)
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{
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struct deref_node *node;
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struct hash_entry *var_entry =
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_mesa_hash_table_search(state->deref_var_nodes, var);
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if (var_entry) {
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return var_entry->data;
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} else {
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node = deref_node_create(NULL, var->type, state->dead_ctx);
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_mesa_hash_table_insert(state->deref_var_nodes, var, node);
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return node;
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}
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}
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/* Gets the deref_node for the given deref chain and creates it if it
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* doesn't yet exist. If the deref is fully-qualified and direct and
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* state->add_to_direct_deref_nodes is true, it will be added to the hash
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* table of of fully-qualified direct derefs.
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*/
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static struct deref_node *
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get_deref_node(nir_deref_var *deref, struct lower_variables_state *state)
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{
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bool is_direct = true;
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/* Start at the base of the chain. */
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struct deref_node *node = get_deref_node_for_var(deref->var, state);
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assert(deref->deref.type == node->type);
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for (nir_deref *tail = deref->deref.child; tail; tail = tail->child) {
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switch (tail->deref_type) {
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case nir_deref_type_struct: {
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nir_deref_struct *deref_struct = nir_deref_as_struct(tail);
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assert(deref_struct->index < glsl_get_length(node->type));
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if (node->children[deref_struct->index] == NULL)
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node->children[deref_struct->index] =
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deref_node_create(node, tail->type, state->dead_ctx);
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node = node->children[deref_struct->index];
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break;
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}
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case nir_deref_type_array: {
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nir_deref_array *arr = nir_deref_as_array(tail);
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switch (arr->deref_array_type) {
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case nir_deref_array_type_direct:
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/* This is possible if a loop unrolls and generates an
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* out-of-bounds offset. We need to handle this at least
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* somewhat gracefully.
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*/
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if (arr->base_offset >= glsl_get_length(node->type))
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return NULL;
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if (node->children[arr->base_offset] == NULL)
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node->children[arr->base_offset] =
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deref_node_create(node, tail->type, state->dead_ctx);
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node = node->children[arr->base_offset];
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break;
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case nir_deref_array_type_indirect:
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if (node->indirect == NULL)
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node->indirect = deref_node_create(node, tail->type,
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state->dead_ctx);
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node = node->indirect;
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is_direct = false;
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break;
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case nir_deref_array_type_wildcard:
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if (node->wildcard == NULL)
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node->wildcard = deref_node_create(node, tail->type,
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state->dead_ctx);
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node = node->wildcard;
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is_direct = false;
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break;
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default:
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unreachable("Invalid array deref type");
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}
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break;
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}
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default:
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unreachable("Invalid deref type");
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}
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}
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assert(node);
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/* Only insert if it isn't already in the list. */
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if (is_direct && state->add_to_direct_deref_nodes &&
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node->direct_derefs_link.next == NULL) {
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node->deref = deref;
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assert(deref->var != NULL);
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exec_list_push_tail(&state->direct_deref_nodes,
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&node->direct_derefs_link);
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}
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return node;
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}
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/* \sa foreach_deref_node_match */
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static bool
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foreach_deref_node_worker(struct deref_node *node, nir_deref *deref,
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bool (* cb)(struct deref_node *node,
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struct lower_variables_state *state),
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struct lower_variables_state *state)
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{
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if (deref->child == NULL) {
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return cb(node, state);
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} else {
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switch (deref->child->deref_type) {
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case nir_deref_type_array: {
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nir_deref_array *arr = nir_deref_as_array(deref->child);
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assert(arr->deref_array_type == nir_deref_array_type_direct);
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if (node->children[arr->base_offset] &&
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!foreach_deref_node_worker(node->children[arr->base_offset],
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deref->child, cb, state))
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return false;
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if (node->wildcard &&
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!foreach_deref_node_worker(node->wildcard,
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deref->child, cb, state))
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return false;
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return true;
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}
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case nir_deref_type_struct: {
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nir_deref_struct *str = nir_deref_as_struct(deref->child);
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return foreach_deref_node_worker(node->children[str->index],
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deref->child, cb, state);
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}
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default:
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unreachable("Invalid deref child type");
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}
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}
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}
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/* Walks over every "matching" deref_node and calls the callback. A node
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* is considered to "match" if either refers to that deref or matches up t
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* a wildcard. In other words, the following would match a[6].foo[3].bar:
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*
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* a[6].foo[3].bar
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* a[*].foo[3].bar
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* a[6].foo[*].bar
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* a[*].foo[*].bar
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*
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* The given deref must be a full-length and fully qualified (no wildcards
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* or indirects) deref chain.
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*/
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static bool
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foreach_deref_node_match(nir_deref_var *deref,
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bool (* cb)(struct deref_node *node,
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struct lower_variables_state *state),
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struct lower_variables_state *state)
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{
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nir_deref_var var_deref = *deref;
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var_deref.deref.child = NULL;
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struct deref_node *node = get_deref_node(&var_deref, state);
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if (node == NULL)
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return false;
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return foreach_deref_node_worker(node, &deref->deref, cb, state);
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}
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/* \sa deref_may_be_aliased */
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static bool
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deref_may_be_aliased_node(struct deref_node *node, nir_deref *deref,
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struct lower_variables_state *state)
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{
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if (deref->child == NULL) {
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return false;
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} else {
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switch (deref->child->deref_type) {
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case nir_deref_type_array: {
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nir_deref_array *arr = nir_deref_as_array(deref->child);
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if (arr->deref_array_type == nir_deref_array_type_indirect)
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return true;
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/* If there is an indirect at this level, we're aliased. */
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if (node->indirect)
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return true;
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assert(arr->deref_array_type == nir_deref_array_type_direct);
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if (node->children[arr->base_offset] &&
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deref_may_be_aliased_node(node->children[arr->base_offset],
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deref->child, state))
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return true;
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if (node->wildcard &&
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deref_may_be_aliased_node(node->wildcard, deref->child, state))
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return true;
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return false;
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}
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case nir_deref_type_struct: {
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nir_deref_struct *str = nir_deref_as_struct(deref->child);
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if (node->children[str->index]) {
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return deref_may_be_aliased_node(node->children[str->index],
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deref->child, state);
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} else {
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return false;
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}
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}
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default:
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unreachable("Invalid nir_deref child type");
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}
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}
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}
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/* Returns true if there are no indirects that can ever touch this deref.
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*
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* For example, if the given deref is a[6].foo, then any uses of a[i].foo
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* would cause this to return false, but a[i].bar would not affect it
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* because it's a different structure member. A var_copy involving of
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* a[*].bar also doesn't affect it because that can be lowered to entirely
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* direct load/stores.
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*
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* We only support asking this question about fully-qualified derefs.
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* Obviously, it's pointless to ask this about indirects, but we also
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* rule-out wildcards. Handling Wildcard dereferences would involve
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* checking each array index to make sure that there aren't any indirect
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* references.
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*/
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static bool
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deref_may_be_aliased(nir_deref_var *deref,
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struct lower_variables_state *state)
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{
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return deref_may_be_aliased_node(get_deref_node_for_var(deref->var, state),
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&deref->deref, state);
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}
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static void
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register_load_instr(nir_intrinsic_instr *load_instr,
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struct lower_variables_state *state)
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{
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struct deref_node *node = get_deref_node(load_instr->variables[0], state);
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if (node == NULL)
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return;
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if (node->loads == NULL)
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node->loads = _mesa_set_create(state->dead_ctx, _mesa_hash_pointer,
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_mesa_key_pointer_equal);
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_mesa_set_add(node->loads, load_instr);
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}
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static void
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register_store_instr(nir_intrinsic_instr *store_instr,
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struct lower_variables_state *state)
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{
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struct deref_node *node = get_deref_node(store_instr->variables[0], state);
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if (node == NULL)
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return;
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if (node->stores == NULL)
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node->stores = _mesa_set_create(state->dead_ctx, _mesa_hash_pointer,
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_mesa_key_pointer_equal);
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_mesa_set_add(node->stores, store_instr);
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}
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static void
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register_copy_instr(nir_intrinsic_instr *copy_instr,
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struct lower_variables_state *state)
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{
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for (unsigned idx = 0; idx < 2; idx++) {
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struct deref_node *node =
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get_deref_node(copy_instr->variables[idx], state);
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if (node == NULL)
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continue;
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if (node->copies == NULL)
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node->copies = _mesa_set_create(state->dead_ctx, _mesa_hash_pointer,
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_mesa_key_pointer_equal);
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_mesa_set_add(node->copies, copy_instr);
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}
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}
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/* Registers all variable uses in the given block. */
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static bool
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register_variable_uses_block(nir_block *block, void *void_state)
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{
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struct lower_variables_state *state = void_state;
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nir_foreach_instr_safe(block, instr) {
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if (instr->type != nir_instr_type_intrinsic)
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continue;
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nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
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switch (intrin->intrinsic) {
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case nir_intrinsic_load_var:
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register_load_instr(intrin, state);
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break;
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case nir_intrinsic_store_var:
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register_store_instr(intrin, state);
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break;
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case nir_intrinsic_copy_var:
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register_copy_instr(intrin, state);
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break;
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default:
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continue;
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}
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}
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return true;
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}
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/* Walks over all of the copy instructions to or from the given deref_node
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* and lowers them to load/store intrinsics.
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*/
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static bool
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lower_copies_to_load_store(struct deref_node *node,
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struct lower_variables_state *state)
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{
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if (!node->copies)
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return true;
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struct set_entry *copy_entry;
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set_foreach(node->copies, copy_entry) {
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nir_intrinsic_instr *copy = (void *)copy_entry->key;
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nir_lower_var_copy_instr(copy, state->shader);
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for (unsigned i = 0; i < 2; ++i) {
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struct deref_node *arg_node =
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get_deref_node(copy->variables[i], state);
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/* Only bother removing copy entries for other nodes */
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if (arg_node == NULL || arg_node == node)
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continue;
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struct set_entry *arg_entry = _mesa_set_search(arg_node->copies, copy);
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assert(arg_entry);
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_mesa_set_remove(node->copies, arg_entry);
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}
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nir_instr_remove(©->instr);
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}
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node->copies = NULL;
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return true;
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}
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|
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/** Pushes an SSA def onto the def stack for the given node
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*
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* Each node is potentially associated with a stack of SSA definitions.
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|
* This stack is used for determining what SSA definition reaches a given
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|
* point in the program for variable renaming. The stack is always kept in
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* dominance-order with at most one SSA def per block. If the SSA
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* definition on the top of the stack is in the same block as the one being
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* pushed, the top element is replaced.
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*/
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static void
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def_stack_push(struct deref_node *node, nir_ssa_def *def,
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struct lower_variables_state *state)
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{
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if (node->def_stack == NULL) {
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node->def_stack = ralloc_array(state->dead_ctx, nir_ssa_def *,
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state->impl->num_blocks);
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node->def_stack_tail = node->def_stack - 1;
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}
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if (node->def_stack_tail >= node->def_stack) {
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nir_ssa_def *top_def = *node->def_stack_tail;
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if (def->parent_instr->block == top_def->parent_instr->block) {
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/* They're in the same block, just replace the top */
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*node->def_stack_tail = def;
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return;
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}
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}
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*(++node->def_stack_tail) = def;
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}
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|
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/* Pop the top of the def stack if it's in the given block */
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static void
|
|
def_stack_pop_if_in_block(struct deref_node *node, nir_block *block)
|
|
{
|
|
/* If we're popping, then we have presumably pushed at some time in the
|
|
* past so this should exist.
|
|
*/
|
|
assert(node->def_stack != NULL);
|
|
|
|
/* The stack is already empty. Do nothing. */
|
|
if (node->def_stack_tail < node->def_stack)
|
|
return;
|
|
|
|
nir_ssa_def *def = *node->def_stack_tail;
|
|
if (def->parent_instr->block == block)
|
|
node->def_stack_tail--;
|
|
}
|
|
|
|
/** Retrieves the SSA definition on the top of the stack for the given
|
|
* node, if one exists. If the stack is empty, then we return the constant
|
|
* initializer (if it exists) or an SSA undef.
|
|
*/
|
|
static nir_ssa_def *
|
|
get_ssa_def_for_block(struct deref_node *node, nir_block *block,
|
|
struct lower_variables_state *state)
|
|
{
|
|
/* If we have something on the stack, go ahead and return it. We're
|
|
* assuming that the top of the stack dominates the given block.
|
|
*/
|
|
if (node->def_stack && node->def_stack_tail >= node->def_stack)
|
|
return *node->def_stack_tail;
|
|
|
|
/* If we got here then we don't have a definition that dominates the
|
|
* given block. This means that we need to add an undef and use that.
|
|
*/
|
|
nir_ssa_undef_instr *undef =
|
|
nir_ssa_undef_instr_create(state->shader,
|
|
glsl_get_vector_elements(node->type));
|
|
nir_instr_insert_before_cf_list(&state->impl->body, &undef->instr);
|
|
def_stack_push(node, &undef->def, state);
|
|
return &undef->def;
|
|
}
|
|
|
|
/* Given a block and one of its predecessors, this function fills in the
|
|
* souces of the phi nodes to take SSA defs from the given predecessor.
|
|
* This function must be called exactly once per block/predecessor pair.
|
|
*/
|
|
static void
|
|
add_phi_sources(nir_block *block, nir_block *pred,
|
|
struct lower_variables_state *state)
|
|
{
|
|
nir_foreach_instr(block, instr) {
|
|
if (instr->type != nir_instr_type_phi)
|
|
break;
|
|
|
|
nir_phi_instr *phi = nir_instr_as_phi(instr);
|
|
|
|
struct hash_entry *entry =
|
|
_mesa_hash_table_search(state->phi_table, phi);
|
|
if (!entry)
|
|
continue;
|
|
|
|
struct deref_node *node = entry->data;
|
|
|
|
nir_phi_src *src = ralloc(phi, nir_phi_src);
|
|
src->pred = pred;
|
|
src->src.parent_instr = &phi->instr;
|
|
src->src.is_ssa = true;
|
|
src->src.ssa = get_ssa_def_for_block(node, pred, state);
|
|
|
|
list_addtail(&src->src.use_link, &src->src.ssa->uses);
|
|
|
|
exec_list_push_tail(&phi->srcs, &src->node);
|
|
}
|
|
}
|
|
|
|
/* Performs variable renaming by doing a DFS of the dominance tree
|
|
*
|
|
* This algorithm is very similar to the one outlined in "Efficiently
|
|
* Computing Static Single Assignment Form and the Control Dependence
|
|
* Graph" by Cytron et. al. The primary difference is that we only put one
|
|
* SSA def on the stack per block.
|
|
*/
|
|
static bool
|
|
rename_variables_block(nir_block *block, struct lower_variables_state *state)
|
|
{
|
|
nir_builder b;
|
|
nir_builder_init(&b, state->impl);
|
|
|
|
nir_foreach_instr_safe(block, instr) {
|
|
if (instr->type == nir_instr_type_phi) {
|
|
nir_phi_instr *phi = nir_instr_as_phi(instr);
|
|
|
|
struct hash_entry *entry =
|
|
_mesa_hash_table_search(state->phi_table, phi);
|
|
|
|
/* This can happen if we already have phi nodes in the program
|
|
* that were not created in this pass.
|
|
*/
|
|
if (!entry)
|
|
continue;
|
|
|
|
struct deref_node *node = entry->data;
|
|
|
|
def_stack_push(node, &phi->dest.ssa, state);
|
|
} else if (instr->type == nir_instr_type_intrinsic) {
|
|
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
|
|
|
|
switch (intrin->intrinsic) {
|
|
case nir_intrinsic_load_var: {
|
|
struct deref_node *node =
|
|
get_deref_node(intrin->variables[0], state);
|
|
|
|
if (node == NULL) {
|
|
/* If we hit this path then we are referencing an invalid
|
|
* value. Most likely, we unrolled something and are
|
|
* reading past the end of some array. In any case, this
|
|
* should result in an undefined value.
|
|
*/
|
|
nir_ssa_undef_instr *undef =
|
|
nir_ssa_undef_instr_create(state->shader,
|
|
intrin->num_components);
|
|
|
|
nir_instr_insert_before(&intrin->instr, &undef->instr);
|
|
nir_instr_remove(&intrin->instr);
|
|
|
|
nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
|
|
nir_src_for_ssa(&undef->def));
|
|
continue;
|
|
}
|
|
|
|
if (!node->lower_to_ssa)
|
|
continue;
|
|
|
|
nir_alu_instr *mov = nir_alu_instr_create(state->shader,
|
|
nir_op_imov);
|
|
mov->src[0].src.is_ssa = true;
|
|
mov->src[0].src.ssa = get_ssa_def_for_block(node, block, state);
|
|
for (unsigned i = intrin->num_components; i < 4; i++)
|
|
mov->src[0].swizzle[i] = 0;
|
|
|
|
assert(intrin->dest.is_ssa);
|
|
|
|
mov->dest.write_mask = (1 << intrin->num_components) - 1;
|
|
nir_ssa_dest_init(&mov->instr, &mov->dest.dest,
|
|
intrin->num_components, NULL);
|
|
|
|
nir_instr_insert_before(&intrin->instr, &mov->instr);
|
|
nir_instr_remove(&intrin->instr);
|
|
|
|
nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
|
|
nir_src_for_ssa(&mov->dest.dest.ssa));
|
|
break;
|
|
}
|
|
|
|
case nir_intrinsic_store_var: {
|
|
struct deref_node *node =
|
|
get_deref_node(intrin->variables[0], state);
|
|
|
|
if (node == NULL) {
|
|
/* Probably an out-of-bounds array store. That should be a
|
|
* no-op. */
|
|
nir_instr_remove(&intrin->instr);
|
|
continue;
|
|
}
|
|
|
|
if (!node->lower_to_ssa)
|
|
continue;
|
|
|
|
assert(intrin->num_components ==
|
|
glsl_get_vector_elements(node->type));
|
|
|
|
assert(intrin->src[0].is_ssa);
|
|
|
|
nir_ssa_def *new_def;
|
|
b.cursor = nir_before_instr(&intrin->instr);
|
|
|
|
if (intrin->const_index[0] == (1 << intrin->num_components) - 1) {
|
|
/* Whole variable store - just copy the source. Note that
|
|
* intrin->num_components and intrin->src[0].ssa->num_components
|
|
* may differ.
|
|
*/
|
|
unsigned swiz[4];
|
|
for (unsigned i = 0; i < 4; i++)
|
|
swiz[i] = i < intrin->num_components ? i : 0;
|
|
|
|
new_def = nir_swizzle(&b, intrin->src[0].ssa, swiz,
|
|
intrin->num_components, false);
|
|
} else {
|
|
nir_ssa_def *old_def = get_ssa_def_for_block(node, block, state);
|
|
/* For writemasked store_var intrinsics, we combine the newly
|
|
* written values with the existing contents of unwritten
|
|
* channels, creating a new SSA value for the whole vector.
|
|
*/
|
|
nir_ssa_def *srcs[4];
|
|
for (unsigned i = 0; i < intrin->num_components; i++) {
|
|
if (intrin->const_index[0] & (1 << i)) {
|
|
srcs[i] = nir_channel(&b, intrin->src[0].ssa, i);
|
|
} else {
|
|
srcs[i] = nir_channel(&b, old_def, i);
|
|
}
|
|
}
|
|
new_def = nir_vec(&b, srcs, intrin->num_components);
|
|
}
|
|
|
|
assert(new_def->num_components == intrin->num_components);
|
|
|
|
def_stack_push(node, new_def, state);
|
|
|
|
/* We'll wait to remove the instruction until the next pass
|
|
* where we pop the node we just pushed back off the stack.
|
|
*/
|
|
break;
|
|
}
|
|
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
if (block->successors[0])
|
|
add_phi_sources(block->successors[0], block, state);
|
|
if (block->successors[1])
|
|
add_phi_sources(block->successors[1], block, state);
|
|
|
|
for (unsigned i = 0; i < block->num_dom_children; ++i)
|
|
rename_variables_block(block->dom_children[i], state);
|
|
|
|
/* Now we iterate over the instructions and pop off any SSA defs that we
|
|
* pushed in the first loop.
|
|
*/
|
|
nir_foreach_instr_safe(block, instr) {
|
|
if (instr->type == nir_instr_type_phi) {
|
|
nir_phi_instr *phi = nir_instr_as_phi(instr);
|
|
|
|
struct hash_entry *entry =
|
|
_mesa_hash_table_search(state->phi_table, phi);
|
|
|
|
/* This can happen if we already have phi nodes in the program
|
|
* that were not created in this pass.
|
|
*/
|
|
if (!entry)
|
|
continue;
|
|
|
|
struct deref_node *node = entry->data;
|
|
|
|
def_stack_pop_if_in_block(node, block);
|
|
} else if (instr->type == nir_instr_type_intrinsic) {
|
|
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
|
|
|
|
if (intrin->intrinsic != nir_intrinsic_store_var)
|
|
continue;
|
|
|
|
struct deref_node *node = get_deref_node(intrin->variables[0], state);
|
|
if (!node)
|
|
continue;
|
|
|
|
if (!node->lower_to_ssa)
|
|
continue;
|
|
|
|
def_stack_pop_if_in_block(node, block);
|
|
nir_instr_remove(&intrin->instr);
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/* Inserts phi nodes for all variables marked lower_to_ssa
|
|
*
|
|
* This is the same algorithm as presented in "Efficiently Computing Static
|
|
* Single Assignment Form and the Control Dependence Graph" by Cytron et.
|
|
* al.
|
|
*/
|
|
static void
|
|
insert_phi_nodes(struct lower_variables_state *state)
|
|
{
|
|
NIR_VLA_ZERO(unsigned, work, state->impl->num_blocks);
|
|
NIR_VLA_ZERO(unsigned, has_already, state->impl->num_blocks);
|
|
|
|
/*
|
|
* Since the work flags already prevent us from inserting a node that has
|
|
* ever been inserted into W, we don't need to use a set to represent W.
|
|
* Also, since no block can ever be inserted into W more than once, we know
|
|
* that the maximum size of W is the number of basic blocks in the
|
|
* function. So all we need to handle W is an array and a pointer to the
|
|
* next element to be inserted and the next element to be removed.
|
|
*/
|
|
NIR_VLA(nir_block *, W, state->impl->num_blocks);
|
|
|
|
unsigned w_start, w_end;
|
|
unsigned iter_count = 0;
|
|
|
|
foreach_list_typed(struct deref_node, node, direct_derefs_link,
|
|
&state->direct_deref_nodes) {
|
|
if (node->stores == NULL)
|
|
continue;
|
|
|
|
if (!node->lower_to_ssa)
|
|
continue;
|
|
|
|
w_start = w_end = 0;
|
|
iter_count++;
|
|
|
|
struct set_entry *store_entry;
|
|
set_foreach(node->stores, store_entry) {
|
|
nir_intrinsic_instr *store = (nir_intrinsic_instr *)store_entry->key;
|
|
if (work[store->instr.block->index] < iter_count)
|
|
W[w_end++] = store->instr.block;
|
|
work[store->instr.block->index] = iter_count;
|
|
}
|
|
|
|
while (w_start != w_end) {
|
|
nir_block *cur = W[w_start++];
|
|
struct set_entry *dom_entry;
|
|
set_foreach(cur->dom_frontier, dom_entry) {
|
|
nir_block *next = (nir_block *) dom_entry->key;
|
|
|
|
/*
|
|
* If there's more than one return statement, then the end block
|
|
* can be a join point for some definitions. However, there are
|
|
* no instructions in the end block, so nothing would use those
|
|
* phi nodes. Of course, we couldn't place those phi nodes
|
|
* anyways due to the restriction of having no instructions in the
|
|
* end block...
|
|
*/
|
|
if (next == state->impl->end_block)
|
|
continue;
|
|
|
|
if (has_already[next->index] < iter_count) {
|
|
nir_phi_instr *phi = nir_phi_instr_create(state->shader);
|
|
nir_ssa_dest_init(&phi->instr, &phi->dest,
|
|
glsl_get_vector_elements(node->type), NULL);
|
|
nir_instr_insert_before_block(next, &phi->instr);
|
|
|
|
_mesa_hash_table_insert(state->phi_table, phi, node);
|
|
|
|
has_already[next->index] = iter_count;
|
|
if (work[next->index] < iter_count) {
|
|
work[next->index] = iter_count;
|
|
W[w_end++] = next;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/** Implements a pass to lower variable uses to SSA values
|
|
*
|
|
* This path walks the list of instructions and tries to lower as many
|
|
* local variable load/store operations to SSA defs and uses as it can.
|
|
* The process involves four passes:
|
|
*
|
|
* 1) Iterate over all of the instructions and mark where each local
|
|
* variable deref is used in a load, store, or copy. While we're at
|
|
* it, we keep track of all of the fully-qualified (no wildcards) and
|
|
* fully-direct references we see and store them in the
|
|
* direct_deref_nodes hash table.
|
|
*
|
|
* 2) Walk over the the list of fully-qualified direct derefs generated in
|
|
* the previous pass. For each deref, we determine if it can ever be
|
|
* aliased, i.e. if there is an indirect reference anywhere that may
|
|
* refer to it. If it cannot be aliased, we mark it for lowering to an
|
|
* SSA value. At this point, we lower any var_copy instructions that
|
|
* use the given deref to load/store operations and, if the deref has a
|
|
* constant initializer, we go ahead and add a load_const value at the
|
|
* beginning of the function with the initialized value.
|
|
*
|
|
* 3) Walk over the list of derefs we plan to lower to SSA values and
|
|
* insert phi nodes as needed.
|
|
*
|
|
* 4) Perform "variable renaming" by replacing the load/store instructions
|
|
* with SSA definitions and SSA uses.
|
|
*/
|
|
static bool
|
|
nir_lower_vars_to_ssa_impl(nir_function_impl *impl)
|
|
{
|
|
struct lower_variables_state state;
|
|
|
|
state.shader = impl->function->shader;
|
|
state.dead_ctx = ralloc_context(state.shader);
|
|
state.impl = impl;
|
|
|
|
state.deref_var_nodes = _mesa_hash_table_create(state.dead_ctx,
|
|
_mesa_hash_pointer,
|
|
_mesa_key_pointer_equal);
|
|
exec_list_make_empty(&state.direct_deref_nodes);
|
|
state.phi_table = _mesa_hash_table_create(state.dead_ctx,
|
|
_mesa_hash_pointer,
|
|
_mesa_key_pointer_equal);
|
|
|
|
/* Build the initial deref structures and direct_deref_nodes table */
|
|
state.add_to_direct_deref_nodes = true;
|
|
nir_foreach_block(impl, register_variable_uses_block, &state);
|
|
|
|
bool progress = false;
|
|
|
|
nir_metadata_require(impl, nir_metadata_block_index);
|
|
|
|
/* We're about to iterate through direct_deref_nodes. Don't modify it. */
|
|
state.add_to_direct_deref_nodes = false;
|
|
|
|
foreach_list_typed_safe(struct deref_node, node, direct_derefs_link,
|
|
&state.direct_deref_nodes) {
|
|
nir_deref_var *deref = node->deref;
|
|
|
|
if (deref->var->data.mode != nir_var_local) {
|
|
exec_node_remove(&node->direct_derefs_link);
|
|
continue;
|
|
}
|
|
|
|
if (deref_may_be_aliased(deref, &state)) {
|
|
exec_node_remove(&node->direct_derefs_link);
|
|
continue;
|
|
}
|
|
|
|
node->lower_to_ssa = true;
|
|
progress = true;
|
|
|
|
if (deref->var->constant_initializer) {
|
|
nir_load_const_instr *load =
|
|
nir_deref_get_const_initializer_load(state.shader, deref);
|
|
nir_ssa_def_init(&load->instr, &load->def,
|
|
glsl_get_vector_elements(node->type), NULL);
|
|
nir_instr_insert_before_cf_list(&impl->body, &load->instr);
|
|
def_stack_push(node, &load->def, &state);
|
|
}
|
|
|
|
foreach_deref_node_match(deref, lower_copies_to_load_store, &state);
|
|
}
|
|
|
|
if (!progress)
|
|
return false;
|
|
|
|
nir_metadata_require(impl, nir_metadata_dominance);
|
|
|
|
/* We may have lowered some copy instructions to load/store
|
|
* instructions. The uses from the copy instructions hav already been
|
|
* removed but we need to rescan to ensure that the uses from the newly
|
|
* added load/store instructions are registered. We need this
|
|
* information for phi node insertion below.
|
|
*/
|
|
nir_foreach_block(impl, register_variable_uses_block, &state);
|
|
|
|
insert_phi_nodes(&state);
|
|
rename_variables_block(nir_start_block(impl), &state);
|
|
|
|
nir_metadata_preserve(impl, nir_metadata_block_index |
|
|
nir_metadata_dominance);
|
|
|
|
ralloc_free(state.dead_ctx);
|
|
|
|
return progress;
|
|
}
|
|
|
|
void
|
|
nir_lower_vars_to_ssa(nir_shader *shader)
|
|
{
|
|
nir_foreach_function(shader, function) {
|
|
if (function->impl)
|
|
nir_lower_vars_to_ssa_impl(function->impl);
|
|
}
|
|
}
|