diff --git a/src/panfrost/compiler/bi_dominance.c b/src/panfrost/compiler/bi_dominance.c new file mode 100644 index 00000000000..d953479a1d9 --- /dev/null +++ b/src/panfrost/compiler/bi_dominance.c @@ -0,0 +1,241 @@ +/* + * 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: + * Connor Abbott (cwabbott0@gmail.com) + * + */ + +#include "nir.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 bool +init_block(nir_block *block, nir_function_impl *impl) +{ + if (block == nir_start_block(impl)) + block->imm_dom = block; + else + block->imm_dom = NULL; + block->num_dom_children = 0; + + /* See nir_block_dominates */ + block->dom_pre_index = UINT32_MAX; + block->dom_post_index = 0; + + _mesa_set_clear(&block->dom_frontier, NULL); + + return true; +} + +static nir_block * +intersect(nir_block *b1, nir_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(nir_block *block) +{ + nir_block *new_idom = NULL; + set_foreach(&block->predecessors, entry) { + nir_block *pred = (nir_block *)entry->key; + + 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 bool +calc_dom_frontier(nir_block *block) +{ + if (block->predecessors.entries > 1) { + set_foreach(&block->predecessors, entry) { + nir_block *runner = (nir_block *)entry->key; + + /* Skip unreachable predecessors */ + if (runner->imm_dom == NULL) + continue; + + while (runner != block->imm_dom) { + _mesa_set_add(&runner->dom_frontier, block); + runner = runner->imm_dom; + } + } + } + + return true; +} + +/* + * Compute each node's children in the dominance tree from the immediate + * dominator information. We do this in three stages: + * + * 1. Calculate the number of children each node has + * 2. Allocate arrays, setting the number of children to 0 again + * 3. For each node, add itself to its parent's list of children, using + * num_dom_children as an index - at the end of this step, num_dom_children + * for each node will be the same as it was at the end of step #1. + */ + +static void +calc_dom_children(nir_function_impl *impl) +{ + void *mem_ctx = ralloc_parent(impl); + + nir_foreach_block_unstructured(block, impl) { + if (block->imm_dom) + block->imm_dom->num_dom_children++; + } + + nir_foreach_block_unstructured(block, impl) { + if (!block->num_dom_children) { + block->dom_children = NULL; + continue; + } + + if (block->num_dom_children <= 3) { + block->dom_children = block->_dom_children_storage; + } else { + block->dom_children = ralloc_array(mem_ctx, nir_block *, + block->num_dom_children); + } + block->num_dom_children = 0; + } + + nir_foreach_block_unstructured(block, impl) { + if (block->imm_dom) { + block->imm_dom->dom_children[block->imm_dom->num_dom_children++] = block; + } + } +} + +static void +calc_dfs_indices(nir_block *block, uint32_t *index) +{ + /* UINT32_MAX has special meaning. See nir_block_dominates. */ + assert(*index < UINT32_MAX - 2); + + block->dom_pre_index = (*index)++; + + for (unsigned i = 0; i < block->num_dom_children; i++) + calc_dfs_indices(block->dom_children[i], index); + + block->dom_post_index = (*index)++; +} + +void +nir_calc_dominance_impl(nir_function_impl *impl) +{ + if (impl->valid_metadata & nir_metadata_dominance) + return; + + nir_metadata_require(impl, nir_metadata_block_index); + + nir_foreach_block_unstructured(block, impl) { + init_block(block, impl); + } + + bool progress = true; + while (progress) { + progress = false; + nir_foreach_block_unstructured(block, impl) { + if (block != nir_start_block(impl)) + progress |= calc_dominance(block); + } + } + + nir_foreach_block_unstructured(block, impl) { + calc_dom_frontier(block); + } + + nir_block *start_block = nir_start_block(impl); + start_block->imm_dom = NULL; + + calc_dom_children(impl); + + uint32_t dfs_index = 1; + calc_dfs_indices(start_block, &dfs_index); +} + +void +nir_calc_dominance(nir_shader *shader) +{ + nir_foreach_function_impl(impl, shader) { + nir_calc_dominance_impl(impl); + } +} + +/** + * Returns true if parent dominates child according to the following + * definition: + * + * "The block A dominates the block B if every path from the start block + * to block B passes through A." + * + * This means, in particular, that any unreachable block is dominated by every + * other block and an unreachable block does not dominate anything except + * another unreachable block. + */ +bool +nir_block_dominates(nir_block *parent, nir_block *child) +{ + assert(nir_cf_node_get_function(&parent->cf_node) == + nir_cf_node_get_function(&child->cf_node)); + + assert(nir_cf_node_get_function(&parent->cf_node)->valid_metadata & + nir_metadata_dominance); + + /* If a block is unreachable, then nir_block::dom_pre_index == UINT32_MAX + * and nir_block::dom_post_index == 0. This allows us to trivially handle + * unreachable blocks here with zero extra work. + */ + return child->dom_pre_index >= parent->dom_pre_index && + child->dom_post_index <= parent->dom_post_index; +}