--- /dev/null
+/*
+ * Copyright © 2014 Intel Corporation
+ * Copyright © 2021 Valve 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 "ir3.h"
+#include "ralloc.h"
+
+/*
+ * Implements the algorithms for computing the dominance tree and the
+ * dominance frontier from "A Simple, Fast Dominance Algorithm" by Cooper,
+ * Harvey, and Kennedy.
+ */
+
+static struct ir3_block *
+intersect(struct ir3_block *b1, struct ir3_block *b2)
+{
+ while (b1 != b2) {
+ /*
+ * Note, the comparisons here are the opposite of what the paper says
+ * because we index blocks from beginning -> end (i.e. reverse
+ * post-order) instead of post-order like they assume.
+ */
+ while (b1->index > b2->index)
+ b1 = b1->imm_dom;
+ while (b2->index > b1->index)
+ b2 = b2->imm_dom;
+ }
+
+ return b1;
+}
+
+
+static bool
+calc_dominance(struct ir3_block *block)
+{
+ struct ir3_block *new_idom = NULL;
+ for (unsigned i = 0; i < block->predecessors_count; i++) {
+ struct ir3_block *pred = block->predecessors[i];
+
+ if (pred->imm_dom) {
+ if (new_idom)
+ new_idom = intersect(pred, new_idom);
+ else
+ new_idom = pred;
+ }
+ }
+
+ if (block->imm_dom != new_idom) {
+ block->imm_dom = new_idom;
+ return true;
+ }
+
+ return false;
+}
+
+static unsigned
+calc_dfs_indices(struct ir3_block *block, unsigned index)
+{
+ block->dom_pre_index = index++;
+ for (unsigned i = 0; i < block->dom_children_count; i++)
+ index = calc_dfs_indices(block->dom_children[i], index);
+ block->dom_post_index = index++;
+ return index;
+}
+
+void
+ir3_calc_dominance(struct ir3 *ir)
+{
+ unsigned i = 0;
+ foreach_block (block, &ir->block_list) {
+ block->index = i++;
+ if (block == ir3_start_block(ir))
+ block->imm_dom = block;
+ else
+ block->imm_dom = NULL;
+ block->dom_children = NULL;
+ block->dom_children_count = block->dom_children_sz = 0;
+ }
+
+ bool progress = true;
+ while (progress) {
+ progress = false;
+ foreach_block (block, &ir->block_list) {
+ if (block != ir3_start_block(ir))
+ progress |= calc_dominance(block);
+ }
+ }
+
+ ir3_start_block(ir)->imm_dom = NULL;
+
+ foreach_block (block, &ir->block_list) {
+ if (block->imm_dom)
+ array_insert(block->imm_dom, block->imm_dom->dom_children, block);
+ }
+
+ calc_dfs_indices(ir3_start_block(ir), 0);
+}
+
+/* Return true if a dominates b. This includes if a == b. */
+bool ir3_block_dominates(struct ir3_block *a, struct ir3_block *b)
+{
+ return a->dom_pre_index <= b->dom_pre_index &&
+ a->dom_post_index >= b->dom_post_index;
+}
+