#include "nir.h"
#include "nir_builder.h"
+#include "nir_phi_builder.h"
#include "nir_vla.h"
struct set *stores;
struct set *copies;
- nir_ssa_def **def_stack;
- nir_ssa_def **def_stack_tail;
+ struct nir_phi_builder_value *pb_value;
struct deref_node *wildcard;
struct deref_node *indirect;
*/
bool add_to_direct_deref_nodes;
- /* A hash table mapping phi nodes to deref_state data */
- struct hash_table *phi_table;
+ struct nir_phi_builder *phi_builder;
};
static struct deref_node *
/* Registers all variable uses in the given block. */
static bool
-register_variable_uses_block(nir_block *block, void *void_state)
+register_variable_uses_block(nir_block *block,
+ struct lower_variables_state *state)
{
- struct lower_variables_state *state = void_state;
-
- nir_foreach_instr_safe(block, instr) {
+ nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
return true;
}
-/** 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->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
+/* Performs variable renaming
*
* 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
+ * 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)
+rename_variables(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)
+ nir_foreach_block(block, state->impl) {
+ nir_foreach_instr_safe(instr, block) {
+ if (instr->type != nir_instr_type_intrinsic)
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) {
*/
nir_ssa_undef_instr *undef =
nir_ssa_undef_instr_create(state->shader,
- intrin->num_components);
+ intrin->num_components,
+ intrin->dest.ssa.bit_size);
nir_instr_insert_before(&intrin->instr, &undef->instr);
nir_instr_remove(&intrin->instr);
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);
+ mov->src[0].src = nir_src_for_ssa(
+ nir_phi_builder_value_get_block_def(node->pb_value, block));
for (unsigned i = intrin->num_components; i < 4; i++)
mov->src[0].swizzle[i] = 0;
mov->dest.write_mask = (1 << intrin->num_components) - 1;
nir_ssa_dest_init(&mov->instr, &mov->dest.dest,
- intrin->num_components, NULL);
+ intrin->num_components,
+ intrin->dest.ssa.bit_size, NULL);
nir_instr_insert_before(&intrin->instr, &mov->instr);
nir_instr_remove(&intrin->instr);
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);
+ nir_ssa_def *old_def =
+ nir_phi_builder_value_get_block_def(node->pb_value, block);
/* 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.
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.
- */
+ nir_phi_builder_value_set_block_def(node->pb_value, block, new_def);
+ nir_instr_remove(&intrin->instr);
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
* 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
+ * 2) Walk over 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.
+ * use the given deref to load/store operations.
*
* 3) Walk over the list of derefs we plan to lower to SSA values and
* insert phi nodes as needed.
_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);
+
+ nir_foreach_block(block, impl) {
+ register_variable_uses_block(block, &state);
+ }
bool progress = false;
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);
}
* added load/store instructions are registered. We need this
* information for phi node insertion below.
*/
- nir_foreach_block(impl, register_variable_uses_block, &state);
+ nir_foreach_block(block, impl) {
+ register_variable_uses_block(block, &state);
+ }
- insert_phi_nodes(&state);
- rename_variables_block(nir_start_block(impl), &state);
+ state.phi_builder = nir_phi_builder_create(state.impl);
+
+ NIR_VLA(BITSET_WORD, store_blocks, BITSET_WORDS(state.impl->num_blocks));
+ foreach_list_typed(struct deref_node, node, direct_derefs_link,
+ &state.direct_deref_nodes) {
+ if (!node->lower_to_ssa)
+ continue;
+
+ memset(store_blocks, 0,
+ BITSET_WORDS(state.impl->num_blocks) * sizeof(*store_blocks));
+
+ assert(node->deref->var->constant_initializer == NULL);
+
+ if (node->stores) {
+ struct set_entry *store_entry;
+ set_foreach(node->stores, store_entry) {
+ nir_intrinsic_instr *store =
+ (nir_intrinsic_instr *)store_entry->key;
+ BITSET_SET(store_blocks, store->instr.block->index);
+ }
+ }
+
+ node->pb_value =
+ nir_phi_builder_add_value(state.phi_builder,
+ glsl_get_vector_elements(node->type),
+ glsl_get_bit_size(node->type),
+ store_blocks);
+ }
+
+ rename_variables(&state);
+
+ nir_phi_builder_finish(state.phi_builder);
nir_metadata_preserve(impl, nir_metadata_block_index |
nir_metadata_dominance);
return progress;
}
-void
+bool
nir_lower_vars_to_ssa(nir_shader *shader)
{
- nir_foreach_function(shader, function) {
+ bool progress = false;
+
+ nir_foreach_function(function, shader) {
if (function->impl)
- nir_lower_vars_to_ssa_impl(function->impl);
+ progress |= nir_lower_vars_to_ssa_impl(function->impl);
}
+
+ return progress;
}
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