--- /dev/null
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "nir_phi_builder.h"
+#include "nir/nir_vla.h"
+
+struct nir_phi_builder {
+ nir_shader *shader;
+ nir_function_impl *impl;
+
+ /* Copied from the impl for easy access */
+ unsigned num_blocks;
+
+ /* Array of all blocks indexed by block->index. */
+ nir_block **blocks;
+
+ /* Hold on to the values so we can easily iterate over them. */
+ struct exec_list values;
+
+ /* Worklist for phi adding */
+ unsigned iter_count;
+ unsigned *work;
+ nir_block **W;
+};
+
+#define NEEDS_PHI ((nir_ssa_def *)(intptr_t)-1)
+
+struct nir_phi_builder_value {
+ struct exec_node node;
+
+ struct nir_phi_builder *builder;
+
+ /* Needed so we can create phis and undefs */
+ unsigned num_components;
+
+ /* The list of phi nodes associated with this value. Phi nodes are not
+ * added directly. Instead, they are created, the instr->block pointer
+ * set, and then added to this list. Later, in phi_builder_finish, we
+ * set up their sources and add them to the top of their respective
+ * blocks.
+ */
+ struct exec_list phis;
+
+ /* Array of SSA defs, indexed by block. If a phi needs to be inserted
+ * in a given block, it will have the magic value NEEDS_PHI.
+ */
+ nir_ssa_def *defs[0];
+};
+
+static bool
+fill_block_array(nir_block *block, void *void_data)
+{
+ nir_block **blocks = void_data;
+ blocks[block->index] = block;
+ return true;
+}
+
+struct nir_phi_builder *
+nir_phi_builder_create(nir_function_impl *impl)
+{
+ struct nir_phi_builder *pb = ralloc(NULL, struct nir_phi_builder);
+
+ pb->shader = impl->function->shader;
+ pb->impl = impl;
+
+ assert(impl->valid_metadata & (nir_metadata_block_index |
+ nir_metadata_dominance));
+
+ pb->num_blocks = impl->num_blocks;
+ pb->blocks = ralloc_array(pb, nir_block *, pb->num_blocks);
+ nir_foreach_block(impl, fill_block_array, pb->blocks);
+
+ exec_list_make_empty(&pb->values);
+
+ pb->iter_count = 0;
+ pb->work = rzalloc_array(pb, unsigned, pb->num_blocks);
+ pb->W = ralloc_array(pb, nir_block *, pb->num_blocks);
+
+ return pb;
+}
+
+struct nir_phi_builder_value *
+nir_phi_builder_add_value(struct nir_phi_builder *pb, unsigned num_components,
+ const BITSET_WORD *defs)
+{
+ struct nir_phi_builder_value *val;
+ unsigned i, w_start = 0, w_end = 0;
+
+ val = rzalloc_size(pb, sizeof(*val) + sizeof(val->defs[0]) * pb->num_blocks);
+ val->builder = pb;
+ val->num_components = num_components;
+ exec_list_make_empty(&val->phis);
+ exec_list_push_tail(&pb->values, &val->node);
+
+ pb->iter_count++;
+
+ BITSET_WORD tmp;
+ BITSET_FOREACH_SET(i, tmp, defs, pb->num_blocks) {
+ if (pb->work[i] < pb->iter_count)
+ pb->W[w_end++] = pb->blocks[i];
+ pb->work[i] = pb->iter_count;
+ }
+
+ while (w_start != w_end) {
+ nir_block *cur = pb->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 == pb->impl->end_block)
+ continue;
+
+ if (val->defs[next->index] == NULL) {
+ val->defs[next->index] = NEEDS_PHI;
+
+ if (pb->work[next->index] < pb->iter_count) {
+ pb->work[next->index] = pb->iter_count;
+ pb->W[w_end++] = next;
+ }
+ }
+ }
+ }
+
+ return val;
+}
+
+void
+nir_phi_builder_value_set_block_def(struct nir_phi_builder_value *val,
+ nir_block *block, nir_ssa_def *def)
+{
+ val->defs[block->index] = def;
+}
+
+nir_ssa_def *
+nir_phi_builder_value_get_block_def(struct nir_phi_builder_value *val,
+ nir_block *block)
+{
+ if (val->defs[block->index] == NULL) {
+ if (block->imm_dom) {
+ /* Grab it from our immediate dominator. We'll stash it here for
+ * easy access later.
+ */
+ val->defs[block->index] =
+ nir_phi_builder_value_get_block_def(val, block->imm_dom);
+ return val->defs[block->index];
+ } else {
+ /* No immediate dominator means that this block is either the
+ * start block or unreachable. In either case, the value is
+ * undefined so we need an SSA undef.
+ */
+ nir_ssa_undef_instr *undef =
+ nir_ssa_undef_instr_create(val->builder->shader,
+ val->num_components);
+ nir_instr_insert(nir_before_cf_list(&val->builder->impl->body),
+ &undef->instr);
+ val->defs[block->index] = &undef->def;
+ return &undef->def;
+ }
+ } else if (val->defs[block->index] == NEEDS_PHI) {
+ /* If we need a phi instruction, go ahead and create one but don't
+ * add it to the program yet. Later, we'll go through and set up phi
+ * sources and add the instructions will be added at that time.
+ */
+ nir_phi_instr *phi = nir_phi_instr_create(val->builder->shader);
+ nir_ssa_dest_init(&phi->instr, &phi->dest, val->num_components, NULL);
+ phi->instr.block = block;
+ exec_list_push_tail(&val->phis, &phi->instr.node);
+ val->defs[block->index] = &phi->dest.ssa;
+ return &phi->dest.ssa;
+ } else {
+ return val->defs[block->index];
+ }
+}
+
+static int
+compare_blocks(const void *_a, const void *_b)
+{
+ nir_block * const * a = _a;
+ nir_block * const * b = _b;
+
+ return (*a)->index - (*b)->index;
+}
+
+void
+nir_phi_builder_finish(struct nir_phi_builder *pb)
+{
+ const unsigned num_blocks = pb->num_blocks;
+ NIR_VLA(nir_block *, preds, num_blocks);
+
+ foreach_list_typed(struct nir_phi_builder_value, val, node, &pb->values) {
+ /* We can't iterate over the list of phis normally because we are
+ * removing them as we go and, in some cases, adding new phis as we
+ * build the source lists of others.
+ */
+ while (!exec_list_is_empty(&val->phis)) {
+ struct exec_node *head = exec_list_get_head(&val->phis);
+ nir_phi_instr *phi = exec_node_data(nir_phi_instr, head, instr.node);
+ assert(phi->instr.type == nir_instr_type_phi);
+
+ exec_node_remove(&phi->instr.node);
+
+ /* Construct an array of predecessors. We sort it to ensure
+ * determinism in the phi insertion algorithm.
+ *
+ * XXX: Calling qsort this many times seems expensive.
+ */
+ int num_preds = 0;
+ struct set_entry *entry;
+ set_foreach(phi->instr.block->predecessors, entry)
+ preds[num_preds++] = (nir_block *)entry->key;
+ qsort(preds, num_preds, sizeof(*preds), compare_blocks);
+
+ for (unsigned i = 0; i < num_preds; i++) {
+ nir_phi_src *src = ralloc(phi, nir_phi_src);
+ src->pred = preds[i];
+ src->src = nir_src_for_ssa(
+ nir_phi_builder_value_get_block_def(val, preds[i]));
+ exec_list_push_tail(&phi->srcs, &src->node);
+ }
+
+ nir_instr_insert(nir_before_block(phi->instr.block), &phi->instr);
+ }
+ }
+
+ ralloc_free(pb);
+}
--- /dev/null
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "nir.h"
+
+struct nir_phi_builder;
+struct nir_phi_builder_value;
+
+/* Create a new phi builder.
+ *
+ * While this is fairly cheap, it does allocate some memory and walk the list
+ * of blocks so it's recommended that you only call it once and use it to
+ * build phis for several values.
+ */
+struct nir_phi_builder *nir_phi_builder_create(nir_function_impl *impl);
+
+/* Register a value with the builder.
+ *
+ * The 'defs' parameter specifies a bitset of blocks in which the given value
+ * is defined. This is used to determine where to place the phi nodes.
+ */
+struct nir_phi_builder_value *
+nir_phi_builder_add_value(struct nir_phi_builder *pb, unsigned num_components,
+ const BITSET_WORD *defs);
+
+/* Register a definition for the given value and block.
+ *
+ * It is safe to call this function as many times as you wish for any given
+ * block/value pair. However, it always replaces whatever was there
+ * previously even if that definition is from a phi node. The phi builder
+ * always uses the latest information it has, so you must be careful about the
+ * order in which you register definitions. The final value at the end of the
+ * block must be the last value registered.
+ */
+void
+nir_phi_builder_value_set_block_def(struct nir_phi_builder_value *val,
+ nir_block *block, nir_ssa_def *def);
+
+/* Get the definition for the given value in the given block.
+ *
+ * This definition will always be the latest definition known for the given
+ * block. If no definition is immediately available, it will crawl up the
+ * dominance tree and insert phi nodes as needed until it finds one. In the
+ * case that no suitable definition is found, it will return the result of a
+ * nir_ssa_undef_instr with the correct number of components.
+ *
+ * Because this function only uses the latest available information for any
+ * given block, you must have already finished registering definitions for any
+ * blocks that dominate the current block in order to get the correct result.
+ */
+nir_ssa_def *
+nir_phi_builder_value_get_block_def(struct nir_phi_builder_value *val,
+ nir_block *block);
+
+/* Finish building phi nodes and free the builder.
+ *
+ * This function does far more than just free memory. Prior to calling
+ * nir_phi_builder_finish, no phi nodes have actually been inserted in the
+ * program. This function is what finishes setting up phi node sources and
+ * adds the phi nodes to the program.
+ */
+void nir_phi_builder_finish(struct nir_phi_builder *pb);
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