--- /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;
+ unsigned bit_size;
+
+ /* 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. For each block, this array has has
+ * one of three types of values:
+ *
+ * - NULL. Indicates that there is no known definition in this block. If
+ * you need to find one, look at the block's immediate dominator.
+ *
+ * - NEEDS_PHI. Indicates that the block may need a phi node but none has
+ * been created yet. If a def is requested for a block, a phi will need
+ * to be created.
+ *
+ * - A regular SSA def. This will be either the result of a phi node or
+ * one of the defs provided by nir_phi_builder_value_set_blocK_def().
+ */
+ 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,
+ unsigned bit_size, 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;
+ val->bit_size = bit_size;
+ 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) {
+ /* Instead of creating a phi node immediately, we simply set the
+ * value to the magic value NEEDS_PHI. Later, we create phi nodes
+ * on demand in nir_phi_builder_value_get_block_def().
+ */
+ 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)
+{
+ /* For each block, we have one of three types of values */
+ if (val->defs[block->index] == NULL) {
+ /* NULL indicates that we have no SSA def for this block. */
+ 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) {
+ /* The magic value NEEDS_PHI indicates that the block needs a phi node
+ * but none has been created. We need to create one now so we can
+ * return it to the caller.
+ *
+ * Because a phi node may use SSA defs that it does not dominate (this
+ * happens in loops), we do not yet have enough information to fully
+ * fill out the phi node. Instead, the phi nodes we create here will be
+ * empty (have no sources) and won't actually be placed in the block's
+ * instruction list yet. Later, in nir_phi_builder_finish(), we walk
+ * over all of the phi instructions, fill out the sources lists, and
+ * place them at the top of their respective block's instruction list.
+ *
+ * Creating phi nodes on-demand allows us to avoid creating dead phi
+ * nodes that will just get deleted later. While this probably isn't a
+ * big win for a full into-SSA pass, other users may use the phi builder
+ * to make small SSA form repairs where most of the phi nodes will never
+ * be used.
+ */
+ nir_phi_instr *phi = nir_phi_instr_create(val->builder->shader);
+ nir_ssa_dest_init(&phi->instr, &phi->dest, val->num_components,
+ val->bit_size, 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 {
+ /* In this case, we have an actual SSA def. It's either the result of a
+ * phi node created by the case above or one passed to us through
+ * nir_phi_builder_value_set_block_def().
+ */
+ 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 treat the linked list of phi nodes like a worklist. The list is
+ * pre-populated by calls to nir_phi_builder_value_get_block_def() that
+ * create phi nodes. As we fill in the sources of phi nodes, more may
+ * be created and are added to the end of the list.
+ *
+ * Because we are adding and removing phi nodes from the list as we go,
+ * we can't iterate over it normally. Instead, we just iterate until
+ * the list is empty.
+ */
+ 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);
+}
projects / mesa.git / blobdiff