nir: Add a better out-of-SSA pass
This commit rewrites the out-of-SSA pass to not be nearly as naieve. It's based on "Revisiting Out-of-SSA Translation for Correctness, Code Quality, and Efficiency" by Boissinot et. al. It should be fairly close to state-of-the art. Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
This commit is contained in:
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commit
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@ -28,134 +28,763 @@
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#include "nir.h"
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/*
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* Implements a quick-and-dirty out-of-ssa pass.
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* This file implements an out-of-SSA pass as described in "Revisiting
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* Out-of-SSA Translation for Correctness, Code Quality, and Efficiency" by
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* Boissinot et. al.
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*/
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struct from_ssa_state {
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void *mem_ctx;
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void *dead_ctx;
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struct hash_table *ssa_table;
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nir_function_impl *current_impl;
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struct hash_table *merge_node_table;
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nir_instr *instr;
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nir_function_impl *impl;
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};
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/* Returns true if a dominates b */
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static bool
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ssa_def_dominates(nir_ssa_def *a, nir_ssa_def *b)
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{
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if (a->live_index == 0) {
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/* SSA undefs always dominate */
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return true;
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} else if (b->live_index < a->live_index) {
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return false;
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} else if (a->parent_instr->block == b->parent_instr->block) {
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return a->live_index <= b->live_index;
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} else {
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nir_block *block = b->parent_instr->block;
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while (block->imm_dom != NULL) {
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if (block->imm_dom == a->parent_instr->block)
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return true;
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block = block->imm_dom;
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}
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return false;
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}
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}
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/* The following data structure, which I have named merge_set is a way of
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* representing a set registers of non-interfering registers. This is
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* based on the concept of a "dominence forest" presented in "Fast Copy
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* Coalescing and Live-Range Identification" by Budimlic et. al. but the
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* implementation concept is taken from "Revisiting Out-of-SSA Translation
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* for Correctness, Code Quality, and Efficiency" by Boissinot et. al..
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*
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* Each SSA definition is associated with a merge_node and the association
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* is represented by a combination of a hash table and the "def" parameter
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* in the merge_node structure. The merge_set stores a linked list of
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* merge_node's in dominence order of the ssa definitions. (Since the
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* liveness analysis pass indexes the SSA values in dominence order for us,
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* this is an easy thing to keep up.) It is assumed that no pair of the
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* nodes in a given set interfere. Merging two sets or checking for
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* interference can be done in a single linear-time merge-sort walk of the
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* two lists of nodes.
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*/
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struct merge_set;
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typedef struct {
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struct exec_node node;
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struct merge_set *set;
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nir_ssa_def *def;
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} merge_node;
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typedef struct merge_set {
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struct exec_list nodes;
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unsigned size;
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nir_register *reg;
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} merge_set;
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#if 0
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static void
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merge_set_dump(merge_set *set, FILE *fp)
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{
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nir_ssa_def *dom[set->size];
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int dom_idx = -1;
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foreach_list_typed(merge_node, node, node, &set->nodes) {
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while (dom_idx >= 0 && !ssa_def_dominates(dom[dom_idx], node->def))
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dom_idx--;
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for (int i = 0; i <= dom_idx; i++)
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fprintf(fp, " ");
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if (node->def->name)
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fprintf(fp, "ssa_%d /* %s */\n", node->def->index, node->def->name);
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else
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fprintf(fp, "ssa_%d\n", node->def->index);
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dom[++dom_idx] = node->def;
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}
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}
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#endif
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static merge_node *
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get_merge_node(nir_ssa_def *def, struct from_ssa_state *state)
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{
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struct hash_entry *entry =
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_mesa_hash_table_search(state->merge_node_table, def);
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if (entry)
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return entry->data;
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merge_set *set = ralloc(state->dead_ctx, merge_set);
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exec_list_make_empty(&set->nodes);
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set->size = 1;
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set->reg = NULL;
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merge_node *node = ralloc(state->dead_ctx, merge_node);
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node->set = set;
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node->def = def;
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exec_list_push_head(&set->nodes, &node->node);
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_mesa_hash_table_insert(state->merge_node_table, def, node);
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return node;
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}
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static bool
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merge_nodes_interfere(merge_node *a, merge_node *b)
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{
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return nir_ssa_defs_interfere(a->def, b->def);
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}
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/* Merges b into a */
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static merge_set *
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merge_merge_sets(merge_set *a, merge_set *b)
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{
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struct exec_node *an = exec_list_get_head(&a->nodes);
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struct exec_node *bn = exec_list_get_head(&b->nodes);
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while (!exec_node_is_tail_sentinel(bn)) {
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merge_node *a_node = exec_node_data(merge_node, an, node);
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merge_node *b_node = exec_node_data(merge_node, bn, node);
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if (exec_node_is_tail_sentinel(an) ||
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a_node->def->live_index > b_node->def->live_index) {
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struct exec_node *next = bn->next;
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exec_node_remove(bn);
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exec_node_insert_node_before(an, bn);
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exec_node_data(merge_node, bn, node)->set = a;
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bn = next;
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} else {
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an = an->next;
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}
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}
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a->size += b->size;
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b->size = 0;
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return a;
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}
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/* Checks for any interference between two merge sets
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*
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* This is an implementation of Algorithm 2 in "Revisiting Out-of-SSA
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* Translation for Correctness, Code Quality, and Efficiency" by
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* Boissinot et. al.
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*/
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static bool
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merge_sets_interfere(merge_set *a, merge_set *b)
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{
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merge_node *dom[a->size + b->size];
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int dom_idx = -1;
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struct exec_node *an = exec_list_get_head(&a->nodes);
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struct exec_node *bn = exec_list_get_head(&b->nodes);
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while (!exec_node_is_tail_sentinel(an) ||
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!exec_node_is_tail_sentinel(bn)) {
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merge_node *current;
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if (exec_node_is_tail_sentinel(an)) {
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current = exec_node_data(merge_node, bn, node);
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bn = bn->next;
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} else if (exec_node_is_tail_sentinel(bn)) {
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current = exec_node_data(merge_node, an, node);
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an = an->next;
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} else {
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merge_node *a_node = exec_node_data(merge_node, an, node);
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merge_node *b_node = exec_node_data(merge_node, bn, node);
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if (a_node->def->live_index <= b_node->def->live_index) {
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current = a_node;
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an = an->next;
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} else {
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current = b_node;
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bn = bn->next;
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}
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}
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while (dom_idx >= 0 &&
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!ssa_def_dominates(dom[dom_idx]->def, current->def))
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dom_idx--;
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if (dom_idx >= 0 && merge_nodes_interfere(current, dom[dom_idx]))
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return true;
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dom[++dom_idx] = current;
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}
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return false;
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}
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static nir_parallel_copy_instr *
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block_get_parallel_copy_at_end(nir_block *block, void *mem_ctx)
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{
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nir_instr *last_instr = nir_block_last_instr(block);
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/* First we try and find a parallel copy if it already exists. If the
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* last instruction is a jump, it will be right before the jump;
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* otherwise, it will be the last instruction.
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*/
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nir_instr *pcopy_instr;
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if (last_instr != NULL && last_instr->type == nir_instr_type_jump)
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pcopy_instr = nir_instr_prev(last_instr);
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else
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pcopy_instr = last_instr;
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if (pcopy_instr != NULL &&
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pcopy_instr->type == nir_instr_type_parallel_copy) {
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/* A parallel copy already exists. */
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nir_parallel_copy_instr *pcopy = nir_instr_as_parallel_copy(pcopy_instr);
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/* This parallel copy may be the copy for the beginning of some
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* block, so we need to check for that before we return it.
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*/
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if (pcopy->at_end)
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return pcopy;
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}
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/* At this point, we haven't found a suitable parallel copy, so we
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* have to create one.
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*/
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nir_parallel_copy_instr *pcopy = nir_parallel_copy_instr_create(mem_ctx);
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pcopy->at_end = true;
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if (last_instr && last_instr->type == nir_instr_type_jump) {
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nir_instr_insert_before(last_instr, &pcopy->instr);
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} else {
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nir_instr_insert_after_block(block, &pcopy->instr);
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}
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return pcopy;
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}
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static bool
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isolate_phi_nodes_block(nir_block *block, void *void_state)
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{
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struct from_ssa_state *state = void_state;
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nir_instr *last_phi_instr = NULL;
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nir_foreach_instr(block, instr) {
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/* Phi nodes only ever come at the start of a block */
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if (instr->type != nir_instr_type_phi)
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break;
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last_phi_instr = instr;
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}
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/* If we don't have any phi's, then there's nothing for us to do. */
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if (last_phi_instr == NULL)
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return true;
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/* If we have phi nodes, we need to create a parallel copy at the
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* start of this block but after the phi nodes.
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*/
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nir_parallel_copy_instr *block_pcopy =
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nir_parallel_copy_instr_create(state->dead_ctx);
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nir_instr_insert_after(last_phi_instr, &block_pcopy->instr);
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nir_foreach_instr(block, instr) {
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/* Phi nodes only ever come at the start of a block */
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if (instr->type != nir_instr_type_phi)
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break;
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nir_phi_instr *phi = nir_instr_as_phi(instr);
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assert(phi->dest.is_ssa);
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foreach_list_typed(nir_phi_src, src, node, &phi->srcs) {
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nir_parallel_copy_instr *pcopy =
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block_get_parallel_copy_at_end(src->pred, state->dead_ctx);
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nir_parallel_copy_copy *copy = ralloc(state->dead_ctx,
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nir_parallel_copy_copy);
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exec_list_push_tail(&pcopy->copies, ©->node);
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copy->src = nir_src_copy(src->src, state->dead_ctx);
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_mesa_set_add(src->src.ssa->uses,
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_mesa_hash_pointer(&pcopy->instr), &pcopy->instr);
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copy->dest.is_ssa = true;
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nir_ssa_def_init(state->impl, &pcopy->instr, ©->dest.ssa,
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phi->dest.ssa.num_components, src->src.ssa->name);
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struct set_entry *entry = _mesa_set_search(src->src.ssa->uses,
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_mesa_hash_pointer(instr),
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instr);
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if (entry)
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/* It is possible that a phi node can use the same source twice
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* but for different basic blocks. If that happens, entry will
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* be NULL because we already deleted it. This is safe
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* because, by the time the loop is done, we will have deleted
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* all of the sources of the phi from their respective use sets
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* and moved them to the parallel copy definitions.
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*/
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_mesa_set_remove(src->src.ssa->uses, entry);
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src->src.ssa = ©->dest.ssa;
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_mesa_set_add(copy->dest.ssa.uses, _mesa_hash_pointer(instr), instr);
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}
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nir_parallel_copy_copy *copy = ralloc(state->dead_ctx,
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nir_parallel_copy_copy);
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exec_list_push_tail(&block_pcopy->copies, ©->node);
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copy->dest.is_ssa = true;
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nir_ssa_def_init(state->impl, &block_pcopy->instr, ©->dest.ssa,
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phi->dest.ssa.num_components, phi->dest.ssa.name);
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nir_src copy_dest_src = {
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.ssa = ©->dest.ssa,
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.is_ssa = true,
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};
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nir_ssa_def_rewrite_uses(&phi->dest.ssa, copy_dest_src, state->mem_ctx);
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copy->src.is_ssa = true;
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copy->src.ssa = &phi->dest.ssa;
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_mesa_set_add(phi->dest.ssa.uses,
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_mesa_hash_pointer(&block_pcopy->instr),
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&block_pcopy->instr);
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}
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return true;
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}
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static bool
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coalesce_phi_nodes_block(nir_block *block, void *void_state)
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{
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struct from_ssa_state *state = void_state;
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nir_foreach_instr(block, instr) {
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/* Phi nodes only ever come at the start of a block */
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if (instr->type != nir_instr_type_phi)
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break;
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nir_phi_instr *phi = nir_instr_as_phi(instr);
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assert(phi->dest.is_ssa);
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merge_node *dest_node = get_merge_node(&phi->dest.ssa, state);
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foreach_list_typed(nir_phi_src, src, node, &phi->srcs) {
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assert(src->src.is_ssa);
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merge_node *src_node = get_merge_node(src->src.ssa, state);
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if (src_node->set != dest_node->set)
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merge_merge_sets(dest_node->set, src_node->set);
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}
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}
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return true;
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}
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static void
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agressive_coalesce_parallel_copy(nir_parallel_copy_instr *pcopy,
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struct from_ssa_state *state)
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{
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foreach_list_typed_safe(nir_parallel_copy_copy, copy, node, &pcopy->copies) {
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if (!copy->src.is_ssa)
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continue;
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/* Don't try and coalesce these */
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if (copy->dest.ssa.num_components != copy->src.ssa->num_components)
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continue;
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merge_node *src_node = get_merge_node(copy->src.ssa, state);
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merge_node *dest_node = get_merge_node(©->dest.ssa, state);
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if (src_node->set == dest_node->set)
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continue;
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if (!merge_sets_interfere(src_node->set, dest_node->set))
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merge_merge_sets(src_node->set, dest_node->set);
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}
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}
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static bool
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agressive_coalesce_block(nir_block *block, void *void_state)
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{
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struct from_ssa_state *state = void_state;
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nir_foreach_instr(block, instr) {
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/* Phi nodes only ever come at the start of a block */
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if (instr->type != nir_instr_type_phi) {
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if (instr->type != nir_instr_type_parallel_copy)
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break; /* The parallel copy must be right after the phis */
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nir_parallel_copy_instr *pcopy = nir_instr_as_parallel_copy(instr);
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agressive_coalesce_parallel_copy(pcopy, state);
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if (pcopy->at_end)
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return true;
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break;
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}
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}
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nir_instr *last_instr = nir_block_last_instr(block);
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if (last_instr && last_instr->type == nir_instr_type_parallel_copy) {
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nir_parallel_copy_instr *pcopy = nir_instr_as_parallel_copy(last_instr);
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if (pcopy->at_end)
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agressive_coalesce_parallel_copy(pcopy, state);
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}
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return true;
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}
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static nir_register *
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get_register_for_ssa_def(nir_ssa_def *def, struct from_ssa_state *state)
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{
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struct hash_entry *entry =
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_mesa_hash_table_search(state->merge_node_table, def);
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if (entry) {
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merge_node *node = (merge_node *)entry->data;
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/* If it doesn't have a register yet, create one. Note that all of
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* the things in the merge set should be the same so it doesn't
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* matter which node's definition we use.
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*/
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if (node->set->reg == NULL) {
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node->set->reg = nir_local_reg_create(state->impl);
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node->set->reg->name = def->name;
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node->set->reg->num_components = def->num_components;
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node->set->reg->num_array_elems = 0;
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}
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return node->set->reg;
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}
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entry = _mesa_hash_table_search(state->ssa_table, def);
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if (entry) {
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return (nir_register *)entry->data;
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} else {
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nir_register *reg = nir_local_reg_create(state->impl);
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reg->name = def->name;
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reg->num_components = def->num_components;
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reg->num_array_elems = 0;
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_mesa_hash_table_insert(state->ssa_table, def, reg);
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return reg;
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}
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}
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|
||||
static bool
|
||||
rewrite_ssa_src(nir_src *src, void *void_state)
|
||||
{
|
||||
struct from_ssa_state *state = void_state;
|
||||
|
||||
if (src->is_ssa) {
|
||||
struct hash_entry *entry =
|
||||
_mesa_hash_table_search(state->ssa_table, src->ssa);
|
||||
assert(entry);
|
||||
/* We don't need to remove it from the uses set because that is going
|
||||
* away. We just need to add it to the one for the register. */
|
||||
nir_register *reg = get_register_for_ssa_def(src->ssa, state);
|
||||
memset(src, 0, sizeof *src);
|
||||
src->reg.reg = (nir_register *)entry->data;
|
||||
src->reg.reg = reg;
|
||||
|
||||
_mesa_set_add(reg->uses, _mesa_hash_pointer(state->instr), state->instr);
|
||||
}
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
static nir_register *
|
||||
reg_create_from_def(nir_ssa_def *def, struct from_ssa_state *state)
|
||||
{
|
||||
nir_register *reg = nir_local_reg_create(state->current_impl);
|
||||
reg->name = def->name;
|
||||
reg->num_components = def->num_components;
|
||||
reg->num_array_elems = 0;
|
||||
|
||||
/* Might as well steal the use-def information from SSA */
|
||||
_mesa_set_destroy(reg->uses, NULL);
|
||||
reg->uses = def->uses;
|
||||
_mesa_set_destroy(reg->if_uses, NULL);
|
||||
reg->if_uses = def->if_uses;
|
||||
_mesa_set_add(reg->defs, _mesa_hash_pointer(def->parent_instr),
|
||||
def->parent_instr);
|
||||
|
||||
/* Add the new register to the table and rewrite the destination */
|
||||
_mesa_hash_table_insert(state->ssa_table, def, reg);
|
||||
|
||||
return reg;
|
||||
}
|
||||
|
||||
static bool
|
||||
rewrite_ssa_dest(nir_dest *dest, void *void_state)
|
||||
{
|
||||
struct from_ssa_state *state = void_state;
|
||||
|
||||
if (dest->is_ssa) {
|
||||
nir_register *reg = reg_create_from_def(&dest->ssa, state);
|
||||
_mesa_set_destroy(dest->ssa.uses, NULL);
|
||||
_mesa_set_destroy(dest->ssa.if_uses, NULL);
|
||||
|
||||
nir_register *reg = get_register_for_ssa_def(&dest->ssa, state);
|
||||
memset(dest, 0, sizeof *dest);
|
||||
dest->reg.reg = reg;
|
||||
|
||||
_mesa_set_add(reg->defs, _mesa_hash_pointer(state->instr), state->instr);
|
||||
}
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
/* Resolves ssa definitions to registers. While we're at it, we also
|
||||
* remove phi nodes and ssa_undef instructions
|
||||
*/
|
||||
static bool
|
||||
convert_from_ssa_block(nir_block *block, void *void_state)
|
||||
resolve_registers_block(nir_block *block, void *void_state)
|
||||
{
|
||||
struct from_ssa_state *state = void_state;
|
||||
|
||||
nir_foreach_instr_safe(block, instr) {
|
||||
if (instr->type == nir_instr_type_ssa_undef) {
|
||||
nir_ssa_undef_instr *undef = nir_instr_as_ssa_undef(instr);
|
||||
reg_create_from_def(&undef->def, state);
|
||||
exec_node_remove(&instr->node);
|
||||
ralloc_steal(state->dead_ctx, instr);
|
||||
} else {
|
||||
nir_foreach_src(instr, rewrite_ssa_src, state);
|
||||
nir_foreach_dest(instr, rewrite_ssa_dest, state);
|
||||
}
|
||||
}
|
||||
|
||||
nir_if *following_if = nir_block_following_if(block);
|
||||
if (following_if)
|
||||
rewrite_ssa_src(&following_if->condition, state);
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
static bool
|
||||
remove_phi_nodes(nir_block *block, void *void_state)
|
||||
{
|
||||
struct from_ssa_state *state = void_state;
|
||||
|
||||
nir_foreach_instr_safe(block, instr) {
|
||||
/* Phi nodes only ever come at the start of a block */
|
||||
if (instr->type != nir_instr_type_phi)
|
||||
break;
|
||||
|
||||
state->instr = instr;
|
||||
nir_foreach_src(instr, rewrite_ssa_src, state);
|
||||
nir_foreach_dest(instr, rewrite_ssa_dest, state);
|
||||
|
||||
nir_phi_instr *phi = nir_instr_as_phi(instr);
|
||||
foreach_list_typed(nir_phi_src, src, node, &phi->srcs) {
|
||||
assert(src->src.is_ssa);
|
||||
struct hash_entry *entry =
|
||||
_mesa_hash_table_search(state->ssa_table, src->src.ssa);
|
||||
nir_alu_instr *mov = nir_alu_instr_create(state->mem_ctx, nir_op_imov);
|
||||
mov->dest.dest = nir_dest_copy(phi->dest, state->mem_ctx);
|
||||
if (entry) {
|
||||
nir_register *reg = (nir_register *)entry->data;
|
||||
mov->src[0].src.reg.reg = reg;
|
||||
mov->dest.write_mask = (1 << reg->num_components) - 1;
|
||||
} else {
|
||||
mov->src[0].src = nir_src_copy(src->src, state->mem_ctx);
|
||||
mov->dest.write_mask = (1 << src->src.ssa->num_components) - 1;
|
||||
}
|
||||
if (instr->type == nir_instr_type_ssa_undef ||
|
||||
instr->type == nir_instr_type_phi) {
|
||||
nir_instr_remove(instr);
|
||||
ralloc_steal(state->dead_ctx, instr);
|
||||
continue;
|
||||
}
|
||||
}
|
||||
state->instr = NULL;
|
||||
|
||||
nir_instr *block_end = nir_block_last_instr(src->pred);
|
||||
if (block_end && block_end->type == nir_instr_type_jump) {
|
||||
/* If the last instruction in the block is a jump, we want to
|
||||
* place the moves after the jump. Otherwise, we want to place
|
||||
* them at the very end.
|
||||
*/
|
||||
exec_node_insert_node_before(&block_end->node, &mov->instr.node);
|
||||
} else {
|
||||
exec_list_push_tail(&src->pred->instr_list, &mov->instr.node);
|
||||
}
|
||||
nir_if *following_if = nir_block_following_if(block);
|
||||
if (following_if && following_if->condition.is_ssa) {
|
||||
nir_register *reg = get_register_for_ssa_def(following_if->condition.ssa,
|
||||
state);
|
||||
memset(&following_if->condition, 0, sizeof following_if->condition);
|
||||
following_if->condition.reg.reg = reg;
|
||||
|
||||
_mesa_set_add(reg->if_uses, _mesa_hash_pointer(following_if),
|
||||
following_if);
|
||||
}
|
||||
|
||||
return true;
|
||||
}
|
||||
|
||||
static void
|
||||
emit_copy(nir_parallel_copy_instr *pcopy, nir_src src, nir_src dest_src,
|
||||
void *mem_ctx)
|
||||
{
|
||||
assert(!dest_src.is_ssa &&
|
||||
dest_src.reg.indirect == NULL &&
|
||||
dest_src.reg.base_offset == 0);
|
||||
nir_dest dest = {
|
||||
.reg.reg = dest_src.reg.reg,
|
||||
.reg.indirect = NULL,
|
||||
.reg.base_offset = 0,
|
||||
.is_ssa = false,
|
||||
};
|
||||
|
||||
if (src.is_ssa)
|
||||
assert(src.ssa->num_components >= dest.reg.reg->num_components);
|
||||
else
|
||||
assert(src.reg.reg->num_components >= dest.reg.reg->num_components);
|
||||
|
||||
nir_alu_instr *mov = nir_alu_instr_create(mem_ctx, nir_op_imov);
|
||||
mov->src[0].src = nir_src_copy(src, mem_ctx);
|
||||
mov->dest.dest = nir_dest_copy(dest, mem_ctx);
|
||||
mov->dest.write_mask = (1 << dest.reg.reg->num_components) - 1;
|
||||
|
||||
nir_instr_insert_before(&pcopy->instr, &mov->instr);
|
||||
}
|
||||
|
||||
/* Resolves a single parallel copy operation into a sequence of mov's
|
||||
*
|
||||
* This is based on Algorithm 1 from "Revisiting Out-of-SSA Translation for
|
||||
* Correctness, Code Quality, and Efficiency" by Boissinot et. al..
|
||||
* However, I never got the algorithm to work as written, so this version
|
||||
* is slightly modified.
|
||||
*
|
||||
* The algorithm works by playing this little shell game with the values.
|
||||
* We start by recording where every source value is and which source value
|
||||
* each destination value should recieve. We then grab any copy whose
|
||||
* destination is "empty", i.e. not used as a source, and do the following:
|
||||
* - Find where its source value currently lives
|
||||
* - Emit the move instruction
|
||||
* - Set the location of the source value to the destination
|
||||
* - Mark the location containing the source value
|
||||
* - Mark the destination as no longer needing to be copied
|
||||
*
|
||||
* When we run out of "empty" destinations, we have a cycle and so we
|
||||
* create a temporary register, copy to that register, and mark the value
|
||||
* we copied as living in that temporary. Now, the cycle is broken, so we
|
||||
* can continue with the above steps.
|
||||
*/
|
||||
static void
|
||||
resolve_parallel_copy(nir_parallel_copy_instr *pcopy,
|
||||
struct from_ssa_state *state)
|
||||
{
|
||||
unsigned num_copies = 0;
|
||||
foreach_list_typed_safe(nir_parallel_copy_copy, copy, node, &pcopy->copies) {
|
||||
/* Sources may be SSA */
|
||||
if (!copy->src.is_ssa && copy->src.reg.reg == copy->dest.reg.reg)
|
||||
continue;
|
||||
|
||||
/* Set both indices equal to UINT_MAX to mark them as not indexed yet. */
|
||||
num_copies++;
|
||||
}
|
||||
|
||||
if (num_copies == 0) {
|
||||
/* Hooray, we don't need any copies! */
|
||||
nir_instr_remove(&pcopy->instr);
|
||||
return;
|
||||
}
|
||||
|
||||
/* The register/source corresponding to the given index */
|
||||
nir_src values[num_copies * 2];
|
||||
memset(values, 0, sizeof values);
|
||||
|
||||
/* The current location of a given piece of data */
|
||||
int loc[num_copies * 2];
|
||||
|
||||
/* The piece of data that the given piece of data is to be copied from */
|
||||
int pred[num_copies * 2];
|
||||
|
||||
/* Initialize loc and pred. We will use -1 for "null" */
|
||||
memset(loc, -1, sizeof loc);
|
||||
memset(pred, -1, sizeof pred);
|
||||
|
||||
/* The destinations we have yet to properly fill */
|
||||
int to_do[num_copies * 2];
|
||||
int to_do_idx = -1;
|
||||
|
||||
/* Now we set everything up:
|
||||
* - All values get assigned a temporary index
|
||||
* - Current locations are set from sources
|
||||
* - Predicessors are recorded from sources and destinations
|
||||
*/
|
||||
int num_vals = 0;
|
||||
foreach_list_typed(nir_parallel_copy_copy, copy, node, &pcopy->copies) {
|
||||
/* Sources may be SSA */
|
||||
if (!copy->src.is_ssa && copy->src.reg.reg == copy->dest.reg.reg)
|
||||
continue;
|
||||
|
||||
int src_idx = -1;
|
||||
for (int i = 0; i < num_vals; ++i) {
|
||||
if (nir_srcs_equal(values[i], copy->src))
|
||||
src_idx = i;
|
||||
}
|
||||
if (src_idx < 0) {
|
||||
src_idx = num_vals++;
|
||||
values[src_idx] = copy->src;
|
||||
}
|
||||
|
||||
exec_node_remove(&instr->node);
|
||||
ralloc_steal(state->dead_ctx, instr);
|
||||
nir_src dest_src = {
|
||||
.reg.reg = copy->dest.reg.reg,
|
||||
.reg.indirect = NULL,
|
||||
.reg.base_offset = 0,
|
||||
.is_ssa = false,
|
||||
};
|
||||
|
||||
int dest_idx = -1;
|
||||
for (int i = 0; i < num_vals; ++i) {
|
||||
if (nir_srcs_equal(values[i], dest_src)) {
|
||||
/* Each destination of a parallel copy instruction should be
|
||||
* unique. A destination may get used as a source, so we still
|
||||
* have to walk the list. However, the predecessor should not,
|
||||
* at this point, be set yet, so we should have -1 here.
|
||||
*/
|
||||
assert(pred[i] == -1);
|
||||
dest_idx = i;
|
||||
}
|
||||
}
|
||||
if (dest_idx < 0) {
|
||||
dest_idx = num_vals++;
|
||||
values[dest_idx] = dest_src;
|
||||
}
|
||||
|
||||
loc[src_idx] = src_idx;
|
||||
pred[dest_idx] = src_idx;
|
||||
|
||||
to_do[++to_do_idx] = dest_idx;
|
||||
}
|
||||
|
||||
/* Currently empty destinations we can go ahead and fill */
|
||||
int ready[num_copies * 2];
|
||||
int ready_idx = -1;
|
||||
|
||||
/* Mark the ones that are ready for copying. We know an index is a
|
||||
* destination if it has a predecessor and it's ready for copying if
|
||||
* it's not marked as containing data.
|
||||
*/
|
||||
for (int i = 0; i < num_vals; i++) {
|
||||
if (pred[i] != -1 && loc[i] == -1)
|
||||
ready[++ready_idx] = i;
|
||||
}
|
||||
|
||||
while (to_do_idx >= 0) {
|
||||
while (ready_idx >= 0) {
|
||||
int b = ready[ready_idx--];
|
||||
int a = pred[b];
|
||||
emit_copy(pcopy, values[loc[a]], values[b], state->mem_ctx);
|
||||
|
||||
/* If any other copies want a they can find it at b */
|
||||
loc[a] = b;
|
||||
|
||||
/* b has been filled, mark it as not needing to be copied */
|
||||
pred[b] = -1;
|
||||
|
||||
/* If a needs to be filled, it's ready for copying now */
|
||||
if (pred[a] != -1)
|
||||
ready[++ready_idx] = a;
|
||||
}
|
||||
int b = to_do[to_do_idx--];
|
||||
if (pred[b] == -1)
|
||||
continue;
|
||||
|
||||
/* If we got here, then we don't have any more trivial copies that we
|
||||
* can do. We have to break a cycle, so we create a new temporary
|
||||
* register for that purpose. Normally, if going out of SSA after
|
||||
* register allocation, you would want to avoid creating temporary
|
||||
* registers. However, we are going out of SSA before register
|
||||
* allocation, so we would rather not create extra register
|
||||
* dependencies for the backend to deal with. If it wants, the
|
||||
* backend can coalesce the (possibly multiple) temporaries.
|
||||
*/
|
||||
assert(num_vals < num_copies * 2);
|
||||
nir_register *reg = nir_local_reg_create(state->impl);
|
||||
reg->name = "copy_temp";
|
||||
reg->num_array_elems = 0;
|
||||
if (values[b].is_ssa)
|
||||
reg->num_components = values[b].ssa->num_components;
|
||||
else
|
||||
reg->num_components = values[b].reg.reg->num_components;
|
||||
values[num_vals].is_ssa = false;
|
||||
values[num_vals].reg.reg = reg;
|
||||
|
||||
emit_copy(pcopy, values[b], values[num_vals], state->mem_ctx);
|
||||
loc[b] = num_vals;
|
||||
ready[++ready_idx] = b;
|
||||
num_vals++;
|
||||
}
|
||||
|
||||
nir_instr_remove(&pcopy->instr);
|
||||
}
|
||||
|
||||
/* Resolves the parallel copies in a block. Each block can have at most
|
||||
* two: One at the beginning, right after all the phi noces, and one at
|
||||
* the end (or right before the final jump if it exists).
|
||||
*/
|
||||
static bool
|
||||
resolve_parallel_copies_block(nir_block *block, void *void_state)
|
||||
{
|
||||
struct from_ssa_state *state = void_state;
|
||||
|
||||
/* At this point, we have removed all of the phi nodes. If a parallel
|
||||
* copy existed right after the phi nodes in this block, it is now the
|
||||
* first instruction.
|
||||
*/
|
||||
nir_instr *first_instr = nir_block_first_instr(block);
|
||||
if (first_instr == NULL)
|
||||
return true; /* Empty, nothing to do. */
|
||||
|
||||
if (first_instr->type == nir_instr_type_parallel_copy) {
|
||||
nir_parallel_copy_instr *pcopy = nir_instr_as_parallel_copy(first_instr);
|
||||
|
||||
resolve_parallel_copy(pcopy, state);
|
||||
}
|
||||
|
||||
nir_instr *last_instr = nir_block_last_instr(block);
|
||||
if (last_instr == NULL)
|
||||
return true; /* Now empty, nothing to do. */
|
||||
|
||||
/* If the last instruction is a jump, the parallel copy will be before
|
||||
* the jump.
|
||||
*/
|
||||
if (last_instr->type == nir_instr_type_jump)
|
||||
last_instr = nir_instr_prev(last_instr);
|
||||
|
||||
if (last_instr && last_instr->type == nir_instr_type_parallel_copy) {
|
||||
nir_parallel_copy_instr *pcopy = nir_instr_as_parallel_copy(last_instr);
|
||||
if (pcopy->at_end)
|
||||
resolve_parallel_copy(pcopy, state);
|
||||
}
|
||||
|
||||
return true;
|
||||
|
@ -168,16 +797,30 @@ nir_convert_from_ssa_impl(nir_function_impl *impl)
|
|||
|
||||
state.mem_ctx = ralloc_parent(impl);
|
||||
state.dead_ctx = ralloc_context(NULL);
|
||||
state.current_impl = impl;
|
||||
state.impl = impl;
|
||||
state.merge_node_table = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
|
||||
_mesa_key_pointer_equal);
|
||||
|
||||
nir_foreach_block(impl, isolate_phi_nodes_block, &state);
|
||||
|
||||
nir_metadata_dirty(impl, nir_metadata_block_index |
|
||||
nir_metadata_dominance);
|
||||
nir_metadata_require(impl, nir_metadata_live_variables |
|
||||
nir_metadata_dominance);
|
||||
|
||||
nir_foreach_block(impl, coalesce_phi_nodes_block, &state);
|
||||
nir_foreach_block(impl, agressive_coalesce_block, &state);
|
||||
|
||||
state.ssa_table = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
|
||||
_mesa_key_pointer_equal);
|
||||
nir_foreach_block(impl, resolve_registers_block, &state);
|
||||
|
||||
nir_foreach_block(impl, remove_phi_nodes, &state);
|
||||
nir_foreach_block(impl, convert_from_ssa_block, &state);
|
||||
nir_foreach_block(impl, resolve_parallel_copies_block, &state);
|
||||
|
||||
/* Clean up dead instructions and the hash table */
|
||||
ralloc_free(state.dead_ctx);
|
||||
/* Clean up dead instructions and the hash tables */
|
||||
_mesa_hash_table_destroy(state.ssa_table, NULL);
|
||||
_mesa_hash_table_destroy(state.merge_node_table, NULL);
|
||||
ralloc_free(state.dead_ctx);
|
||||
}
|
||||
|
||||
void
|
||||
|
|
Loading…
Reference in New Issue