gcc/graphite-dependences.cc

   1 /* Data dependence analysis for Graphite.
   2    Copyright (C) 2009-2024 Free Software Foundation, Inc.
   3    Contributed by Sebastian Pop <sebastian.pop@amd.com> and
   4    Konrad Trifunovic <konrad.trifunovic@inria.fr>.
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 3, or (at your option)
  11 any later version.
  12
  13 GCC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 #define INCLUDE_ISL
  23
  24 #include "config.h"
  25
  26 #ifdef HAVE_isl
  27
  28 #include "system.h"
  29 #include "coretypes.h"
  30 #include "backend.h"
  31 #include "cfghooks.h"
  32 #include "tree.h"
  33 #include "gimple.h"
  34 #include "fold-const.h"
  35 #include "gimple-iterator.h"
  36 #include "tree-ssa-loop.h"
  37 #include "tree-pass.h"
  38 #include "cfgloop.h"
  39 #include "tree-data-ref.h"
  40 #include "graphite.h"
  41
  42 /* Add the constraints from the set S to the domain of MAP.  */
  43
  44 static isl_map *
  45 constrain_domain (isl_map *map, isl_set *s)
  46 {
  47   isl_space *d = isl_map_get_space (map);
  48   isl_id *id = isl_space_get_tuple_id (d, isl_dim_in);
  49
  50   s = isl_set_set_tuple_id (s, id);
  51   isl_space_free (d);
  52   return isl_map_coalesce (isl_map_intersect_domain (map, s));
  53 }
  54
  55 /* Constrain pdr->accesses with pdr->subscript_sizes and pbb->domain.  */
  56
  57 static isl_map *
  58 add_pdr_constraints (poly_dr_p pdr, poly_bb_p pbb)
  59 {
  60   isl_map *x = isl_map_intersect_range (isl_map_copy (pdr->accesses),
  61                                         isl_set_copy (pdr->subscript_sizes));
  62   x = isl_map_coalesce (x);
  63   return constrain_domain (x, isl_set_copy (pbb->domain));
  64 }
  65
  66 /* Returns an isl description of all memory operations in SCOP.  The memory
  67    reads are returned in READS and writes in MUST_WRITES and MAY_WRITES.  */
  68
  69 static void
  70 scop_get_reads_and_writes (scop_p scop, isl_union_map *&reads,
  71                            isl_union_map *&must_writes,
  72                            isl_union_map *&may_writes)
  73 {
  74   int i, j;
  75   poly_bb_p pbb;
  76   poly_dr_p pdr;
  77
  78   FOR_EACH_VEC_ELT (scop->pbbs, i, pbb)
  79     {
  80       FOR_EACH_VEC_ELT (PBB_DRS (pbb), j, pdr) {
  81         if (pdr_read_p (pdr))
  82           {
  83             if (dump_file)
  84               {
  85                 fprintf (dump_file, "Adding read to depedence graph: ");
  86                 print_pdr (dump_file, pdr);
  87               }
  88             isl_union_map *um
  89               = isl_union_map_from_map (add_pdr_constraints (pdr, pbb));
  90             reads = isl_union_map_union (reads, um);
  91             if (dump_file)
  92               {
  93                 fprintf (dump_file, "Reads depedence graph: ");
  94                 print_isl_union_map (dump_file, reads);
  95               }
  96           }
  97         else if (pdr_write_p (pdr))
  98           {
  99             if (dump_file)
 100               {
 101                 fprintf (dump_file, "Adding must write to depedence graph: ");
 102                 print_pdr (dump_file, pdr);
 103               }
 104             isl_union_map *um
 105               = isl_union_map_from_map (add_pdr_constraints (pdr, pbb));
 106             must_writes = isl_union_map_union (must_writes, um);
 107             if (dump_file)
 108               {
 109                 fprintf (dump_file, "Must writes depedence graph: ");
 110                 print_isl_union_map (dump_file, must_writes);
 111               }
 112           }
 113         else if (pdr_may_write_p (pdr))
 114           {
 115             if (dump_file)
 116               {
 117                 fprintf (dump_file, "Adding may write to depedence graph: ");
 118                 print_pdr (dump_file, pdr);
 119               }
 120             isl_union_map *um
 121               = isl_union_map_from_map (add_pdr_constraints (pdr, pbb));
 122             may_writes = isl_union_map_union (may_writes, um);
 123             if (dump_file)
 124               {
 125                 fprintf (dump_file, "May writes depedence graph: ");
 126                 print_isl_union_map (dump_file, may_writes);
 127               }
 128           }
 129       }
 130     }
 131 }
 132
 133 /* Helper function used on each MAP of a isl_union_map.  Computes the
 134    maximal output dimension.  */
 135
 136 static isl_stat
 137 max_number_of_out_dimensions (__isl_take isl_map *map, void *user)
 138 {
 139   int global_max = *((int *) user);
 140   isl_space *space = isl_map_get_space (map);
 141   int nb_out = isl_space_dim (space, isl_dim_out);
 142
 143   if (global_max < nb_out)
 144     *((int *) user) = nb_out;
 145
 146   isl_map_free (map);
 147   isl_space_free (space);
 148   return isl_stat_ok;
 149 }
 150
 151 /* Extends the output dimension of MAP to MAX dimensions.  */
 152
 153 static __isl_give isl_map *
 154 extend_map (__isl_take isl_map *map, int max)
 155 {
 156   isl_space *space = isl_map_get_space (map);
 157   int n = isl_space_dim (space, isl_dim_out);
 158
 159   isl_space_free (space);
 160   return isl_map_add_dims (map, isl_dim_out, max - n);
 161 }
 162
 163 /* Structure used to pass parameters to extend_schedule_1.  */
 164
 165 struct extend_schedule_str {
 166   int max;
 167   isl_union_map *umap;
 168 };
 169
 170 /* Helper function for extend_schedule.  */
 171
 172 static isl_stat
 173 extend_schedule_1 (__isl_take isl_map *map, void *user)
 174 {
 175   struct extend_schedule_str *str = (struct extend_schedule_str *) user;
 176   str->umap = isl_union_map_add_map (str->umap, extend_map (map, str->max));
 177   return isl_stat_ok;
 178 }
 179
 180 /* Return a relation that has uniform output dimensions.  */
 181
 182 static __isl_give isl_union_map *
 183 extend_schedule (__isl_take isl_union_map *x)
 184 {
 185   int max = 0;
 186   struct extend_schedule_str str;
 187
 188   isl_union_map_foreach_map (x, max_number_of_out_dimensions, (void *) &max);
 189   str.max = max;
 190   str.umap = isl_union_map_empty (isl_union_map_get_space (x));
 191   isl_union_map_foreach_map (x, extend_schedule_1, (void *) &str);
 192   isl_union_map_free (x);
 193   return isl_union_map_coalesce (str.umap);
 194 }
 195
 196 /* Applies SCHEDULE to the in and out dimensions of the dependences
 197    DEPS and return the resulting relation.  */
 198
 199 static isl_map *
 200 apply_schedule_on_deps (__isl_keep isl_union_map *schedule,
 201                         __isl_keep isl_union_map *deps)
 202 {
 203   isl_union_map *trans = extend_schedule (isl_union_map_copy (schedule));
 204   isl_union_map *ux = isl_union_map_copy (deps);
 205   ux = isl_union_map_apply_domain (ux, isl_union_map_copy (trans));
 206   ux = isl_union_map_apply_range (ux, trans);
 207   ux = isl_union_map_coalesce (ux);
 208
 209   if (!isl_union_map_is_empty (ux))
 210     return isl_map_from_union_map (ux);
 211
 212   isl_union_map_free (ux);
 213   return NULL;
 214 }
 215
 216 /* Return true when DEPS is non empty and the intersection of LEX with
 217    the DEPS transformed by SCHEDULE is non empty.  LEX is the relation
 218    in which all the inputs before DEPTH occur at the same time as the
 219    output, and the input at DEPTH occurs before output.  */
 220
 221 bool
 222 carries_deps (__isl_keep isl_union_map *schedule,
 223               __isl_keep isl_union_map *deps,
 224               int depth)
 225 {
 226   if (isl_union_map_is_empty (deps))
 227     return false;
 228
 229   isl_map *x = apply_schedule_on_deps (schedule, deps);
 230   if (x == NULL)
 231     return false;
 232
 233   isl_space *space = isl_map_get_space (x);
 234   isl_map *lex = isl_map_lex_le (isl_space_range (space));
 235   isl_constraint *ineq = isl_inequality_alloc
 236     (isl_local_space_from_space (isl_map_get_space (x)));
 237
 238   for (int i = 0; i < depth - 1; i++)
 239     lex = isl_map_equate (lex, isl_dim_in, i, isl_dim_out, i);
 240
 241   /* in + 1 <= out  */
 242   ineq = isl_constraint_set_coefficient_si (ineq, isl_dim_out, depth - 1, 1);
 243   ineq = isl_constraint_set_coefficient_si (ineq, isl_dim_in, depth - 1, -1);
 244   ineq = isl_constraint_set_constant_si (ineq, -1);
 245   lex = isl_map_add_constraint (lex, ineq);
 246   lex = isl_map_coalesce (lex);
 247   x = isl_map_intersect (x, lex);
 248   bool res = !isl_map_is_empty (x);
 249
 250   isl_map_free (x);
 251   return res;
 252 }
 253
 254 /* Compute the dependence relations for the SCOP:
 255    RAW are read after write dependences,
 256    WAR are write after read dependences,
 257    WAW are write after write dependences.  */
 258
 259 void
 260 scop_get_dependences (scop_p scop)
 261 {
 262   if (scop->dependence)
 263     return;
 264
 265   isl_space *space = isl_set_get_space (scop->param_context);
 266   isl_union_map *reads = isl_union_map_empty (isl_space_copy (space));
 267   isl_union_map *must_writes = isl_union_map_empty (isl_space_copy (space));
 268   isl_union_map *may_writes = isl_union_map_empty (space);
 269   scop_get_reads_and_writes (scop, reads, must_writes, may_writes);
 270
 271   if (dump_file)
 272     {
 273       fprintf (dump_file, "\n--- Documentation for datarefs dump: ---\n");
 274       fprintf (dump_file, "Statements on the iteration domain are mapped to"
 275                " array references.\n");
 276       fprintf (dump_file, "  To read the following data references:\n\n");
 277       fprintf (dump_file, "  S_5[i0] -> [106] : i0 >= 0 and i0 <= 3\n");
 278       fprintf (dump_file, "  S_8[i0] -> [1, i0] : i0 >= 0 and i0 <= 3\n\n");
 279
 280       fprintf (dump_file, "  S_5[i0] is the dynamic instance of statement"
 281                " bb_5 in a loop that accesses all iterations 0 <= i0 <= 3.\n");
 282       fprintf (dump_file, "  [1, i0] is a 'memref' with alias set 1"
 283                " and first subscript access i0.\n");
 284       fprintf (dump_file, "  [106] is a 'scalar reference' which is the sum of"
 285                " SSA_NAME_VERSION 6"
 286                " and --param graphite-max-arrays-per-scop=100\n");
 287       fprintf (dump_file, "-----------------------\n\n");
 288
 289       fprintf (dump_file, "data references (\n");
 290       fprintf (dump_file, "  reads: ");
 291       print_isl_union_map (dump_file, reads);
 292       fprintf (dump_file, "  must_writes: ");
 293       print_isl_union_map (dump_file, must_writes);
 294       fprintf (dump_file, "  may_writes: ");
 295       print_isl_union_map (dump_file, may_writes);
 296       fprintf (dump_file, ")\n");
 297     }
 298
 299   gcc_assert (scop->original_schedule);
 300
 301   isl_union_access_info *ai;
 302   ai = isl_union_access_info_from_sink (isl_union_map_copy (reads));
 303   ai = isl_union_access_info_set_must_source (ai, isl_union_map_copy (must_writes));
 304   ai = isl_union_access_info_set_may_source (ai, may_writes);
 305   ai = isl_union_access_info_set_schedule
 306     (ai, isl_schedule_copy (scop->original_schedule));
 307   isl_union_flow *flow = isl_union_access_info_compute_flow (ai);
 308   isl_union_map *raw = isl_union_flow_get_must_dependence (flow);
 309   isl_union_flow_free (flow);
 310
 311   ai = isl_union_access_info_from_sink (isl_union_map_copy (must_writes));
 312   ai = isl_union_access_info_set_must_source (ai, must_writes);
 313   ai = isl_union_access_info_set_may_source (ai, reads);
 314   ai = isl_union_access_info_set_schedule
 315     (ai, isl_schedule_copy (scop->original_schedule));
 316   flow = isl_union_access_info_compute_flow (ai);
 317
 318   isl_union_map *waw = isl_union_flow_get_must_dependence (flow);
 319   isl_union_map *war = isl_union_flow_get_may_dependence (flow);
 320   war = isl_union_map_subtract (war, isl_union_map_copy (waw));
 321   isl_union_flow_free (flow);
 322
 323   raw = isl_union_map_coalesce (raw);
 324   waw = isl_union_map_coalesce (waw);
 325   war = isl_union_map_coalesce (war);
 326
 327   isl_union_map *dependences = raw;
 328   dependences = isl_union_map_union (dependences, war);
 329   dependences = isl_union_map_union (dependences, waw);
 330   dependences = isl_union_map_coalesce (dependences);
 331
 332   if (dump_file)
 333     {
 334       fprintf (dump_file, "data dependences (\n");
 335       print_isl_union_map (dump_file, dependences);
 336       fprintf (dump_file, ")\n");
 337     }
 338
 339   scop->dependence = dependences;
 340 }
 341
 342 #endif /* HAVE_isl */