/* * Copyright © 2014 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. * * Authors: * Jason Ekstrand (jason@jlekstrand.net) * */ #include "nir.h" struct deref_node { struct deref_node *parent; const struct glsl_type *type; bool lower_to_ssa; struct set *loads; struct set *stores; struct set *copies; nir_ssa_def **def_stack; nir_ssa_def **def_stack_tail; struct deref_node *wildcard; struct deref_node *indirect; struct deref_node *children[0]; }; struct lower_variables_state { void *mem_ctx; void *dead_ctx; nir_function_impl *impl; /* A hash table mapping variables to deref_node data */ struct hash_table *deref_var_nodes; /* A hash table mapping dereference leaves to deref_node data. A deref * is considered a leaf if it is fully-qualified (no wildcards) and * direct. In short, these are the derefs we can actually consider * lowering to SSA values. */ struct hash_table *deref_leaves; /* A hash table mapping phi nodes to deref_state data */ struct hash_table *phi_table; }; /* The following two functions implement a hash and equality check for * variable dreferences. When the hash or equality function encounters an * array, all indirects are treated as equal and are never equal to a * direct dereference or a wildcard. * * Some of the magic numbers here were taken from _mesa_hash_data and one * was just a big prime I found on the internet. */ static uint32_t hash_deref(const void *void_deref) { const nir_deref *deref = void_deref; uint32_t hash; if (deref->child) { hash = hash_deref(deref->child); } else { hash = 2166136261ul; } switch (deref->deref_type) { case nir_deref_type_var: hash ^= _mesa_hash_pointer(nir_deref_as_var(deref)->var); break; case nir_deref_type_array: { nir_deref_array *array = nir_deref_as_array(deref); hash += 268435183 * array->deref_array_type; if (array->deref_array_type == nir_deref_array_type_direct) hash ^= array->base_offset; /* Some prime */ break; } case nir_deref_type_struct: hash ^= nir_deref_as_struct(deref)->index; break; } return hash * 0x01000193; } static bool derefs_equal(const void *void_a, const void *void_b) { const nir_deref *a = void_a; const nir_deref *b = void_b; if (a->deref_type != b->deref_type) return false; switch (a->deref_type) { case nir_deref_type_var: if (nir_deref_as_var(a)->var != nir_deref_as_var(b)->var) return false; break; case nir_deref_type_array: { nir_deref_array *a_arr = nir_deref_as_array(a); nir_deref_array *b_arr = nir_deref_as_array(b); if (a_arr->deref_array_type != b_arr->deref_array_type) return false; if (a_arr->deref_array_type == nir_deref_array_type_direct && a_arr->base_offset != b_arr->base_offset) return false; break; } case nir_deref_type_struct: if (nir_deref_as_struct(a)->index != nir_deref_as_struct(b)->index) return false; break; default: unreachable("Invalid dreference type"); } assert((a->child == NULL) == (b->child == NULL)); if (a->child) return derefs_equal(a->child, b->child); else return true; } static int type_get_length(const struct glsl_type *type) { switch (glsl_get_base_type(type)) { case GLSL_TYPE_STRUCT: case GLSL_TYPE_ARRAY: return glsl_get_length(type); case GLSL_TYPE_FLOAT: case GLSL_TYPE_INT: case GLSL_TYPE_UINT: case GLSL_TYPE_BOOL: if (glsl_type_is_matrix(type)) return glsl_get_matrix_columns(type); else return glsl_get_vector_elements(type); default: unreachable("Invalid deref base type"); } } static struct deref_node * deref_node_create(struct deref_node *parent, const struct glsl_type *type, void *mem_ctx) { size_t size = sizeof(struct deref_node) + type_get_length(type) * sizeof(struct deref_node *); struct deref_node *node = rzalloc_size(mem_ctx, size); node->type = type; node->parent = parent; return node; } /* Gets the deref_node for the given deref chain and creates it if it * doesn't yet exist. If the deref is a leaf (fully-qualified and direct) * and add_to_leaves is true, it will be added to the hash table of leaves. */ static struct deref_node * get_deref_node(nir_deref_var *deref, bool add_to_leaves, struct lower_variables_state *state) { bool is_leaf = true; struct deref_node *parent = NULL; nir_deref *tail = &deref->deref; while (tail) { struct deref_node *node; switch (tail->deref_type) { case nir_deref_type_var: { assert(tail == &deref->deref); assert(parent == NULL); struct hash_entry *entry = _mesa_hash_table_search(state->deref_var_nodes, deref->var); if (entry) { node = entry->data; } else { node = deref_node_create(NULL, tail->type, state->dead_ctx); _mesa_hash_table_insert(state->deref_var_nodes, deref->var, node); } break; } case nir_deref_type_struct: { assert(parent != NULL); nir_deref_struct *deref_struct = nir_deref_as_struct(tail); assert(deref_struct->index < type_get_length(parent->type)); if (parent->children[deref_struct->index]) { node = parent->children[deref_struct->index]; } else { node = deref_node_create(parent, tail->type, state->dead_ctx); parent->children[deref_struct->index] = node; } break; } case nir_deref_type_array: { assert(parent != NULL); nir_deref_array *arr = nir_deref_as_array(tail); switch (arr->deref_array_type) { case nir_deref_array_type_direct: if (arr->base_offset >= type_get_length(parent->type)) { /* This is possible if a loop unrolls and generates an * out-of-bounds offset. We need to handle this at least * somewhat gracefully. */ return NULL; } else if (parent->children[arr->base_offset]) { node = parent->children[arr->base_offset]; } else { node = deref_node_create(parent, tail->type, state->dead_ctx); parent->children[arr->base_offset] = node; } break; case nir_deref_array_type_indirect: if (parent->indirect) { node = parent->indirect; } else { node = deref_node_create(parent, tail->type, state->dead_ctx); parent->indirect = node; } is_leaf = false; break; case nir_deref_array_type_wildcard: if (parent->wildcard) { node = parent->wildcard; } else { node = deref_node_create(parent, tail->type, state->dead_ctx); parent->wildcard = node; } is_leaf = false; break; default: unreachable("Invalid array deref type"); } break; } default: unreachable("Invalid deref type"); } parent = node; tail = tail->child; } assert(parent); if (is_leaf && add_to_leaves) _mesa_hash_table_insert(state->deref_leaves, deref, parent); return parent; } /* \sa foreach_deref_node_match */ static bool foreach_deref_node_worker(struct deref_node *node, nir_deref *deref, bool (* cb)(struct deref_node *node, struct lower_variables_state *state), struct lower_variables_state *state) { if (deref->child == NULL) { return cb(node, state); } else { switch (deref->child->deref_type) { case nir_deref_type_array: { nir_deref_array *arr = nir_deref_as_array(deref->child); assert(arr->deref_array_type == nir_deref_array_type_direct); if (node->children[arr->base_offset] && !foreach_deref_node_worker(node->children[arr->base_offset], deref->child, cb, state)) return false; if (node->wildcard && !foreach_deref_node_worker(node->wildcard, deref->child, cb, state)) return false; return true; } case nir_deref_type_struct: { nir_deref_struct *str = nir_deref_as_struct(deref->child); return foreach_deref_node_worker(node->children[str->index], deref->child, cb, state); } default: unreachable("Invalid deref child type"); } } } /* Walks over every "matching" deref_node and calls the callback. A node * is considered to "match" if either refers to that deref or matches up t * a wildcard. In other words, the following would match a[6].foo[3].bar: * * a[6].foo[3].bar * a[*].foo[3].bar * a[6].foo[*].bar * a[*].foo[*].bar * * The given deref must be a full-length and fully qualified (no wildcards * or indirexcts) deref chain. */ static bool foreach_deref_node_match(nir_deref_var *deref, bool (* cb)(struct deref_node *node, struct lower_variables_state *state), struct lower_variables_state *state) { nir_deref_var var_deref = *deref; var_deref.deref.child = NULL; struct deref_node *node = get_deref_node(&var_deref, false, state); if (node == NULL) return false; return foreach_deref_node_worker(node, &deref->deref, cb, state); } /* \sa deref_may_be_aliased */ static bool deref_may_be_aliased_node(struct deref_node *node, nir_deref *deref, struct lower_variables_state *state) { if (deref->child == NULL) { return false; } else { switch (deref->child->deref_type) { case nir_deref_type_array: { nir_deref_array *arr = nir_deref_as_array(deref->child); if (arr->deref_array_type == nir_deref_array_type_indirect) return true; assert(arr->deref_array_type == nir_deref_array_type_direct); if (node->children[arr->base_offset] && deref_may_be_aliased_node(node->children[arr->base_offset], deref->child, state)) return true; if (node->wildcard && deref_may_be_aliased_node(node->wildcard, deref->child, state)) return true; return false; } case nir_deref_type_struct: { nir_deref_struct *str = nir_deref_as_struct(deref->child); if (node->children[str->index]) { return deref_may_be_aliased_node(node->children[str->index], deref->child, state); } else { return false; } } default: unreachable("Invalid nir_deref child type"); } } } /* Returns true if there are no indirects that can ever touch this deref. * This question can only be asked about fully-qualified derefs. * Obviously, it's pointless to ask this about indirects, but we also * rule-out wildcards. For example, if the given deref is a[6].foo, then * any uses of a[i].foo would case this to return false, but a[i].bar would * not affect it because it's a different structure member. A var_copy * involving of a[*].bar also doesn't affect it because that can be lowered * to entirely direct load/stores. */ static bool deref_may_be_aliased(nir_deref_var *deref, struct lower_variables_state *state) { nir_deref_var var_deref = *deref; var_deref.deref.child = NULL; struct deref_node *node = get_deref_node(&var_deref, false, state); /* An invalid dereference can't be aliased. */ if (node == NULL) return false; return deref_may_be_aliased_node(node, &deref->deref, state); } static void register_load_instr(nir_intrinsic_instr *load_instr, bool create_node, struct lower_variables_state *state) { struct deref_node *node = get_deref_node(load_instr->variables[0], create_node, state); if (node == NULL) return; if (node->loads == NULL) node->loads = _mesa_set_create(state->dead_ctx, _mesa_key_pointer_equal); _mesa_set_add(node->loads, _mesa_hash_pointer(load_instr), load_instr); } static void register_store_instr(nir_intrinsic_instr *store_instr, bool create_node, struct lower_variables_state *state) { struct deref_node *node = get_deref_node(store_instr->variables[0], create_node, state); if (node == NULL) return; if (node->stores == NULL) node->stores = _mesa_set_create(state->dead_ctx, _mesa_key_pointer_equal); _mesa_set_add(node->stores, _mesa_hash_pointer(store_instr), store_instr); } static void register_copy_instr(nir_intrinsic_instr *copy_instr, bool create_node, struct lower_variables_state *state) { for (unsigned idx = 0; idx < 2; idx++) { struct deref_node *node = get_deref_node(copy_instr->variables[idx], create_node, state); if (node == NULL) continue; if (node->copies == NULL) node->copies = _mesa_set_create(state->dead_ctx, _mesa_key_pointer_equal); _mesa_set_add(node->copies, _mesa_hash_pointer(copy_instr), copy_instr); } } /* Registers all variable uses in the given block. */ static bool register_variable_uses_block(nir_block *block, void *void_state) { struct lower_variables_state *state = void_state; nir_foreach_instr_safe(block, instr) { if (instr->type != nir_instr_type_intrinsic) continue; nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); switch (intrin->intrinsic) { case nir_intrinsic_load_var: register_load_instr(intrin, true, state); break; case nir_intrinsic_store_var: register_store_instr(intrin, true, state); break; case nir_intrinsic_copy_var: register_copy_instr(intrin, true, state); break; default: continue; } } return true; } /* Walks down the deref chain and returns the next deref in the chain whose * child is a wildcard. In other words, given the chain a[1].foo[*].bar, * this function will return the deref to foo. Calling it a second time * with the [*].bar, it will return NULL. */ static nir_deref * deref_next_wildcard_parent(nir_deref *deref) { for (nir_deref *tail = deref; tail->child; tail = tail->child) { if (tail->child->deref_type != nir_deref_type_array) continue; nir_deref_array *arr = nir_deref_as_array(tail->child); if (arr->deref_array_type == nir_deref_array_type_wildcard) return tail; } return NULL; } /* Returns the last deref in the chain. */ static nir_deref * get_deref_tail(nir_deref *deref) { while (deref->child) deref = deref->child; return deref; } /* This function recursively walks the given deref chain and replaces the * given copy instruction with an equivalent sequence load/store * operations. * * @copy_instr The copy instruction to replace; new instructions will be * inserted before this one * * @dest_head The head of the destination variable deref chain * * @src_head The head of the source variable deref chain * * @dest_tail The current tail of the destination variable deref chain; * this is used for recursion and external callers of this * function should call it with tail == head * * @src_tail The current tail of the source variable deref chain; * this is used for recursion and external callers of this * function should call it with tail == head * * @state The current variable lowering state */ static void emit_copy_load_store(nir_intrinsic_instr *copy_instr, nir_deref_var *dest_head, nir_deref_var *src_head, nir_deref *dest_tail, nir_deref *src_tail, struct lower_variables_state *state) { /* Find the next pair of wildcards */ nir_deref *src_arr_parent = deref_next_wildcard_parent(src_tail); nir_deref *dest_arr_parent = deref_next_wildcard_parent(dest_tail); if (src_arr_parent || dest_arr_parent) { /* Wildcards had better come in matched pairs */ assert(dest_arr_parent && dest_arr_parent); nir_deref_array *src_arr = nir_deref_as_array(src_arr_parent->child); nir_deref_array *dest_arr = nir_deref_as_array(dest_arr_parent->child); unsigned length = type_get_length(src_arr_parent->type); /* The wildcards should represent the same number of elements */ assert(length == type_get_length(dest_arr_parent->type)); assert(length > 0); /* Walk over all of the elements that this wildcard refers to and * call emit_copy_load_store on each one of them */ src_arr->deref_array_type = nir_deref_array_type_direct; dest_arr->deref_array_type = nir_deref_array_type_direct; for (unsigned i = 0; i < length; i++) { src_arr->base_offset = i; dest_arr->base_offset = i; emit_copy_load_store(copy_instr, dest_head, src_head, &dest_arr->deref, &src_arr->deref, state); } src_arr->deref_array_type = nir_deref_array_type_wildcard; dest_arr->deref_array_type = nir_deref_array_type_wildcard; } else { /* In this case, we have no wildcards anymore, so all we have to do * is just emit the load and store operations. */ src_tail = get_deref_tail(src_tail); dest_tail = get_deref_tail(dest_tail); assert(src_tail->type == dest_tail->type); unsigned num_components = glsl_get_vector_elements(src_tail->type); nir_deref *src_deref = nir_copy_deref(state->mem_ctx, &src_head->deref); nir_deref *dest_deref = nir_copy_deref(state->mem_ctx, &dest_head->deref); nir_intrinsic_instr *load = nir_intrinsic_instr_create(state->mem_ctx, nir_intrinsic_load_var); load->num_components = num_components; load->variables[0] = nir_deref_as_var(src_deref); load->dest.is_ssa = true; nir_ssa_def_init(&load->instr, &load->dest.ssa, num_components, NULL); nir_instr_insert_before(©_instr->instr, &load->instr); register_load_instr(load, false, state); nir_intrinsic_instr *store = nir_intrinsic_instr_create(state->mem_ctx, nir_intrinsic_store_var); store->num_components = num_components; store->variables[0] = nir_deref_as_var(dest_deref); store->src[0].is_ssa = true; store->src[0].ssa = &load->dest.ssa; nir_instr_insert_before(©_instr->instr, &store->instr); register_store_instr(store, false, state); } } /* Walks over all of the copy instructions to or from the given deref_node * and lowers them to load/store intrinsics. */ static bool lower_copies_to_load_store(struct deref_node *node, struct lower_variables_state *state) { if (!node->copies) return true; struct set_entry *copy_entry; set_foreach(node->copies, copy_entry) { nir_intrinsic_instr *copy = (void *)copy_entry->key; emit_copy_load_store(copy, copy->variables[0], copy->variables[1], ©->variables[0]->deref, ©->variables[1]->deref, state); for (unsigned i = 0; i < 2; ++i) { struct deref_node *arg_node = get_deref_node(copy->variables[i], false, state); if (arg_node == NULL) continue; struct set_entry *arg_entry = _mesa_set_search(arg_node->copies, copy_entry->hash, copy); assert(arg_entry); _mesa_set_remove(node->copies, arg_entry); } nir_instr_remove(©->instr); } return true; } /* Returns a load_const instruction that represents the constant * initializer for the given deref chain. The caller is responsible for * ensuring that there actually is a constant initializer. */ static nir_load_const_instr * get_const_initializer_load(const nir_deref_var *deref, struct lower_variables_state *state) { nir_constant *constant = deref->var->constant_initializer; const nir_deref *tail = &deref->deref; unsigned matrix_offset = 0; while (tail->child) { switch (tail->child->deref_type) { case nir_deref_type_array: { nir_deref_array *arr = nir_deref_as_array(tail->child); assert(arr->deref_array_type == nir_deref_array_type_direct); if (glsl_type_is_matrix(tail->type)) { assert(arr->deref.child == NULL); matrix_offset = arr->base_offset; } else { constant = constant->elements[arr->base_offset]; } break; } case nir_deref_type_struct: { constant = constant->elements[nir_deref_as_struct(tail->child)->index]; break; } default: unreachable("Invalid deref child type"); } tail = tail->child; } nir_load_const_instr *load = nir_load_const_instr_create(state->mem_ctx, glsl_get_vector_elements(tail->type)); matrix_offset *= load->def.num_components; for (unsigned i = 0; i < load->def.num_components; i++) { switch (glsl_get_base_type(tail->type)) { case GLSL_TYPE_FLOAT: case GLSL_TYPE_INT: case GLSL_TYPE_UINT: load->value.u[i] = constant->value.u[matrix_offset + i]; break; case GLSL_TYPE_BOOL: load->value.u[i] = constant->value.u[matrix_offset + i] ? NIR_TRUE : NIR_FALSE; break; default: unreachable("Invalid immediate type"); } } return load; } /** Pushes an SSA def onto the def stack for the given node * * Each node is potentially associated with a stack of SSA definitions. * This stack is used for determining what SSA definition reaches a given * point in the program for variable renaming. The stack is always kept in * dominance-order with at most one SSA def per block. If the SSA * definition on the top of the stack is in the same block as the one being * pushed, the top element is replaced. */ static void def_stack_push(struct deref_node *node, nir_ssa_def *def, struct lower_variables_state *state) { if (node->def_stack == NULL) { node->def_stack = ralloc_array(state->dead_ctx, nir_ssa_def *, state->impl->num_blocks); node->def_stack_tail = node->def_stack - 1; } if (node->def_stack_tail >= node->def_stack) { nir_ssa_def *top_def = *node->def_stack_tail; if (def->parent_instr->block == top_def->parent_instr->block) { /* They're in the same block, just replace the top */ *node->def_stack_tail = def; return; } } *(++node->def_stack_tail) = def; } /* Pop the top of the def stack if it's in the given block */ 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->mem_ctx, 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(state->mem_ctx, nir_phi_src); src->pred = pred; src->src.is_ssa = true; src->src.ssa = get_ssa_def_for_block(node, pred, state); _mesa_set_add(src->src.ssa->uses, _mesa_hash_pointer(instr), instr); 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_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], false, 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->mem_ctx, intrin->num_components); nir_instr_insert_before(&intrin->instr, &undef->instr); nir_instr_remove(&intrin->instr); nir_src new_src = { .is_ssa = true, .ssa = &undef->def, }; nir_ssa_def_rewrite_uses(&intrin->dest.ssa, new_src, state->mem_ctx); continue; } if (!node->lower_to_ssa) continue; nir_alu_instr *mov = nir_alu_instr_create(state->mem_ctx, 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; mov->dest.dest.is_ssa = true; nir_ssa_def_init(&mov->instr, &mov->dest.dest.ssa, intrin->num_components, NULL); nir_instr_insert_before(&intrin->instr, &mov->instr); nir_instr_remove(&intrin->instr); nir_src new_src = { .is_ssa = true, .ssa = &mov->dest.dest.ssa, }; nir_ssa_def_rewrite_uses(&intrin->dest.ssa, new_src, state->mem_ctx); break; } case nir_intrinsic_store_var: { struct deref_node *node = get_deref_node(intrin->variables[0], false, 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_alu_instr *mov = nir_alu_instr_create(state->mem_ctx, nir_op_imov); mov->src[0].src.is_ssa = true; mov->src[0].src.ssa = intrin->src[0].ssa; for (unsigned i = intrin->num_components; i < 4; i++) mov->src[0].swizzle[i] = 0; mov->dest.write_mask = (1 << intrin->num_components) - 1; mov->dest.dest.is_ssa = true; nir_ssa_def_init(&mov->instr, &mov->dest.dest.ssa, intrin->num_components, NULL); nir_instr_insert_before(&intrin->instr, &mov->instr); def_stack_push(node, &mov->dest.dest.ssa, state); /* We'll wait to remove the unstruction 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], false, 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) { unsigned work[state->impl->num_blocks]; unsigned has_already[state->impl->num_blocks]; nir_block *W[state->impl->num_blocks]; memset(work, 0, sizeof work); memset(has_already, 0, sizeof has_already); unsigned w_start, w_end; unsigned iter_count = 0; struct hash_entry *deref_entry; hash_table_foreach(state->deref_leaves, deref_entry) { struct deref_node *node = deref_entry->data; 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->mem_ctx); phi->dest.is_ssa = true; nir_ssa_def_init(&phi->instr, &phi->dest.ssa, 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; } } } } } } static bool nir_lower_variables_impl(nir_function_impl *impl) { struct lower_variables_state state; state.mem_ctx = ralloc_parent(impl); state.dead_ctx = ralloc_context(state.mem_ctx); state.impl = impl; state.deref_var_nodes = _mesa_hash_table_create(state.dead_ctx, _mesa_hash_pointer, _mesa_key_pointer_equal); state.deref_leaves = _mesa_hash_table_create(state.dead_ctx, hash_deref, derefs_equal); state.phi_table = _mesa_hash_table_create(state.dead_ctx, _mesa_hash_pointer, _mesa_key_pointer_equal); nir_foreach_block(impl, register_variable_uses_block, &state); struct set *outputs = _mesa_set_create(state.dead_ctx, _mesa_key_pointer_equal); bool progress = false; nir_metadata_require(impl, nir_metadata_block_index); struct hash_entry *entry; hash_table_foreach(state.deref_leaves, entry) { nir_deref_var *deref = (void *)entry->key; struct deref_node *node = entry->data; if (deref->var->data.mode != nir_var_local) { _mesa_hash_table_remove(state.deref_leaves, entry); continue; } if (deref_may_be_aliased(deref, &state)) { _mesa_hash_table_remove(state.deref_leaves, entry); continue; } node->lower_to_ssa = true; progress = true; if (deref->var->constant_initializer) { nir_load_const_instr *load = get_const_initializer_load(deref, &state); 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); } if (deref->var->data.mode == nir_var_shader_out) _mesa_set_add(outputs, _mesa_hash_pointer(node), node); foreach_deref_node_match(deref, lower_copies_to_load_store, &state); } if (!progress) return false; nir_metadata_require(impl, nir_metadata_dominance); insert_phi_nodes(&state); rename_variables_block(impl->start_block, &state); nir_metadata_preserve(impl, nir_metadata_block_index | nir_metadata_dominance); ralloc_free(state.dead_ctx); return progress; } void nir_lower_variables(nir_shader *shader) { nir_foreach_overload(shader, overload) { if (overload->impl) nir_lower_variables_impl(overload->impl); } }