src/glsl/nir/nir_dominance.c

   1 /*
   2  * Copyright © 2014 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  *
  23  * Authors:
  24  *    Connor Abbott (cwabbott0@gmail.com)
  25  *
  26  */
  27
  28 #include "nir.h"
  29
  30 /*
  31  * Implements the algorithms for computing the dominance tree and the
  32  * dominance frontier from "A Simple, Fast Dominance Algorithm" by Cooper,
  33  * Harvey, and Kennedy.
  34  */
  35
  36 typedef struct {
  37    nir_function_impl *impl;
  38    bool progress;
  39 } dom_state;
  40
  41 static bool
  42 init_block_cb(nir_block *block, void *_state)
  43 {
  44    dom_state *state = (dom_state *) _state;
  45    if (block == state->impl->start_block)
  46       block->imm_dom = block;
  47    else
  48       block->imm_dom = NULL;
  49    block->num_dom_children = 0;
  50
  51    struct set_entry *entry;
  52    set_foreach(block->dom_frontier, entry) {
  53       _mesa_set_remove(block->dom_frontier, entry);
  54    }
  55
  56    return true;
  57 }
  58
  59 static nir_block *
  60 intersect(nir_block *b1, nir_block *b2)
  61 {
  62    while (b1 != b2) {
  63       /*
  64        * Note, the comparisons here are the opposite of what the paper says
  65        * because we index blocks from beginning -> end (i.e. reverse
  66        * post-order) instead of post-order like they assume.
  67        */
  68       while (b1->index > b2->index)
  69          b1 = b1->imm_dom;
  70       while (b2->index > b1->index)
  71          b2 = b2->imm_dom;
  72    }
  73
  74    return b1;
  75 }
  76
  77 static bool
  78 calc_dominance_cb(nir_block *block, void *_state)
  79 {
  80    dom_state *state = (dom_state *) _state;
  81    if (block == state->impl->start_block)
  82       return true;
  83
  84    nir_block *new_idom = NULL;
  85    struct set_entry *entry;
  86    set_foreach(block->predecessors, entry) {
  87       nir_block *pred = (nir_block *) entry->key;
  88
  89       if (pred->imm_dom) {
  90          if (new_idom)
  91             new_idom = intersect(pred, new_idom);
  92          else
  93             new_idom = pred;
  94       }
  95    }
  96
  97    assert(new_idom);
  98    if (block->imm_dom != new_idom) {
  99       block->imm_dom = new_idom;
 100       state->progress = true;
 101    }
 102
 103    return true;
 104 }
 105
 106 static bool
 107 calc_dom_frontier_cb(nir_block *block, void *state)
 108 {
 109    (void) state;
 110
 111    if (block->predecessors->entries > 1) {
 112       struct set_entry *entry;
 113       set_foreach(block->predecessors, entry) {
 114          nir_block *runner = (nir_block *) entry->key;
 115          while (runner != block->imm_dom) {
 116             _mesa_set_add(runner->dom_frontier, _mesa_hash_pointer(block),
 117                           block);
 118             runner = runner->imm_dom;
 119          }
 120       }
 121    }
 122
 123    return true;
 124 }
 125
 126 /*
 127  * Compute each node's children in the dominance tree from the immediate
 128  * dominator information. We do this in three stages:
 129  *
 130  * 1. Calculate the number of children each node has
 131  * 2. Allocate arrays, setting the number of children to 0 again
 132  * 3. For each node, add itself to its parent's list of children, using
 133  *    num_dom_children as an index - at the end of this step, num_dom_children
 134  *    for each node will be the same as it was at the end of step #1.
 135  */
 136
 137 static bool
 138 block_count_children(nir_block *block, void *state)
 139 {
 140    (void) state;
 141
 142    if (block->imm_dom)
 143       block->imm_dom->num_dom_children++;
 144
 145    return true;
 146 }
 147
 148 static bool
 149 block_alloc_children(nir_block *block, void *state)
 150 {
 151    void *mem_ctx = state;
 152
 153    block->dom_children = ralloc_array(mem_ctx, nir_block *,
 154                                       block->num_dom_children);
 155    block->num_dom_children = 0;
 156
 157    return true;
 158 }
 159
 160 static bool
 161 block_add_child(nir_block *block, void *state)
 162 {
 163    (void) state;
 164
 165    if (block->imm_dom)
 166       block->imm_dom->dom_children[block->imm_dom->num_dom_children++] = block;
 167
 168    return true;
 169 }
 170
 171 static void
 172 calc_dom_children(nir_function_impl* impl)
 173 {
 174    void *mem_ctx = ralloc_parent(impl);
 175
 176    nir_foreach_block(impl, block_count_children, NULL);
 177    nir_foreach_block(impl, block_alloc_children, mem_ctx);
 178    nir_foreach_block(impl, block_add_child, NULL);
 179 }
 180
 181 void
 182 nir_calc_dominance_impl(nir_function_impl *impl)
 183 {
 184    if (impl->valid_metadata & nir_metadata_dominance)
 185       return;
 186
 187    nir_metadata_require(impl, nir_metadata_block_index);
 188
 189    dom_state state;
 190    state.impl = impl;
 191    state.progress = true;
 192
 193    nir_foreach_block(impl, init_block_cb, &state);
 194
 195    while (state.progress) {
 196       state.progress = false;
 197       nir_foreach_block(impl, calc_dominance_cb, &state);
 198    }
 199
 200    nir_foreach_block(impl, calc_dom_frontier_cb, &state);
 201
 202    impl->start_block->imm_dom = NULL;
 203
 204    calc_dom_children(impl);
 205 }
 206
 207 void
 208 nir_calc_dominance(nir_shader *shader)
 209 {
 210    nir_foreach_overload(shader, overload) {
 211       if (overload->impl)
 212          nir_calc_dominance_impl(overload->impl);
 213    }
 214 }
 215
 216 static bool
 217 dump_block_dom(nir_block *block, void *state)
 218 {
 219    FILE *fp = (FILE *) state;
 220    if (block->imm_dom)
 221       fprintf(fp, "\t%u -> %u\n", block->imm_dom->index, block->index);
 222    return true;
 223 }
 224
 225 void
 226 nir_dump_dom_tree_impl(nir_function_impl *impl, FILE *fp)
 227 {
 228    fprintf(fp, "digraph doms_%s {\n", impl->overload->function->name);
 229    nir_foreach_block(impl, dump_block_dom, fp);
 230    fprintf(fp, "}\n\n");
 231 }
 232
 233 void
 234 nir_dump_dom_tree(nir_shader *shader, FILE *fp)
 235 {
 236    nir_foreach_overload(shader, overload) {
 237       if (overload->impl)
 238          nir_dump_dom_tree_impl(overload->impl, fp);
 239    }
 240 }
 241
 242 static bool
 243 dump_block_dom_frontier(nir_block *block, void *state)
 244 {
 245    FILE *fp = (FILE *) state;
 246
 247    fprintf(fp, "DF(%u) = {", block->index);
 248    struct set_entry *entry;
 249    set_foreach(block->dom_frontier, entry) {
 250       nir_block *df = (nir_block *) entry->key;
 251       fprintf(fp, "%u, ", df->index);
 252    }
 253    fprintf(fp, "}\n");
 254    return true;
 255 }
 256
 257 void
 258 nir_dump_dom_frontier_impl(nir_function_impl *impl, FILE *fp)
 259 {
 260    nir_foreach_block(impl, dump_block_dom_frontier, fp);
 261 }
 262
 263 void
 264 nir_dump_dom_frontier(nir_shader *shader, FILE *fp)
 265 {
 266    nir_foreach_overload(shader, overload) {
 267       if (overload->impl)
 268          nir_dump_dom_frontier_impl(overload->impl, fp);
 269    }
 270 }
 271
 272 static bool
 273 dump_block_succs(nir_block *block, void *state)
 274 {
 275    FILE *fp = (FILE *) state;
 276    if (block->successors[0])
 277       fprintf(fp, "\t%u -> %u\n", block->index, block->successors[0]->index);
 278    if (block->successors[1])
 279       fprintf(fp, "\t%u -> %u\n", block->index, block->successors[1]->index);
 280    return true;
 281 }
 282
 283 void
 284 nir_dump_cfg_impl(nir_function_impl *impl, FILE *fp)
 285 {
 286    fprintf(fp, "digraph cfg_%s {\n", impl->overload->function->name);
 287    nir_foreach_block(impl, dump_block_succs, fp);
 288    fprintf(fp, "}\n\n");
 289 }
 290
 291 void
 292 nir_dump_cfg(nir_shader *shader, FILE *fp)
 293 {
 294    nir_foreach_overload(shader, overload) {
 295       if (overload->impl)
 296          nir_dump_cfg_impl(overload->impl, fp);
 297    }
 298 }