src/broadcom/compiler/vir_live_variables.c

   1 /*
   2  * Copyright © 2012 Intel Corporation
   3  * Copyright © 2016 Broadcom
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a
   6  * copy of this software and associated documentation files (the "Software"),
   7  * to deal in the Software without restriction, including without limitation
   8  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   9  * and/or sell copies of the Software, and to permit persons to whom the
  10  * Software is furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice (including the next
  13  * paragraph) shall be included in all copies or substantial portions of the
  14  * Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  21  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  22  * IN THE SOFTWARE.
  23  */
  24
  25 #define MAX_INSTRUCTION (1 << 30)
  26
  27 #include "util/ralloc.h"
  28 #include "util/register_allocate.h"
  29 #include "v3d_compiler.h"
  30
  31 struct partial_update_state {
  32         struct qinst *insts[4];
  33         uint8_t channels;
  34 };
  35
  36 static uint32_t
  37 int_hash(const void *key)
  38 {
  39         return _mesa_hash_data(key, sizeof(int));
  40 }
  41
  42 static bool
  43 int_compare(const void *key1, const void *key2)
  44 {
  45         return *(const int *)key1 == *(const int *)key2;
  46 }
  47
  48 static int
  49 vir_reg_to_var(struct qreg reg)
  50 {
  51         if (reg.file == QFILE_TEMP)
  52                 return reg.index;
  53
  54         return -1;
  55 }
  56
  57 static void
  58 vir_setup_use(struct v3d_compile *c, struct qblock *block, int ip,
  59               struct qreg src)
  60 {
  61         int var = vir_reg_to_var(src);
  62         if (var == -1)
  63                 return;
  64
  65         c->temp_start[var] = MIN2(c->temp_start[var], ip);
  66         c->temp_end[var] = MAX2(c->temp_end[var], ip);
  67
  68         /* The use[] bitset marks when the block makes
  69          * use of a variable without having completely
  70          * defined that variable within the block.
  71          */
  72         if (!BITSET_TEST(block->def, var))
  73                 BITSET_SET(block->use, var);
  74 }
  75
  76 static struct partial_update_state *
  77 get_partial_update_state(struct hash_table *partial_update_ht,
  78                          struct qinst *inst)
  79 {
  80         struct hash_entry *entry =
  81                 _mesa_hash_table_search(partial_update_ht,
  82                                         &inst->dst.index);
  83         if (entry)
  84                 return entry->data;
  85
  86         struct partial_update_state *state =
  87                 rzalloc(partial_update_ht, struct partial_update_state);
  88
  89         _mesa_hash_table_insert(partial_update_ht, &inst->dst.index, state);
  90
  91         return state;
  92 }
  93
  94 static void
  95 vir_setup_def(struct v3d_compile *c, struct qblock *block, int ip,
  96               struct hash_table *partial_update_ht, struct qinst *inst)
  97 {
  98         if (inst->qpu.type != V3D_QPU_INSTR_TYPE_ALU)
  99                 return;
 100
 101         /* The def[] bitset marks when an initialization in a
 102          * block completely screens off previous updates of
 103          * that variable.
 104          */
 105         int var = vir_reg_to_var(inst->dst);
 106         if (var == -1)
 107                 return;
 108
 109         c->temp_start[var] = MIN2(c->temp_start[var], ip);
 110         c->temp_end[var] = MAX2(c->temp_end[var], ip);
 111
 112         /* Mark the block as having a (partial) def of the var. */
 113         BITSET_SET(block->defout, var);
 114
 115         /* If we've already tracked this as a def that screens off previous
 116          * uses, or already used it within the block, there's nothing to do.
 117          */
 118         if (BITSET_TEST(block->use, var) || BITSET_TEST(block->def, var))
 119                 return;
 120
 121         /* Easy, common case: unconditional full register update.*/
 122         if ((inst->qpu.flags.ac == V3D_QPU_COND_NONE &&
 123              inst->qpu.flags.mc == V3D_QPU_COND_NONE) &&
 124             inst->qpu.alu.add.output_pack == V3D_QPU_PACK_NONE &&
 125             inst->qpu.alu.mul.output_pack == V3D_QPU_PACK_NONE) {
 126                 BITSET_SET(block->def, var);
 127                 return;
 128         }
 129
 130         /* Finally, look at the condition code and packing and mark it as a
 131          * def.  We need to make sure that we understand sequences
 132          * instructions like:
 133          *
 134          *     mov.zs t0, t1
 135          *     mov.zc t0, t2
 136          *
 137          * or:
 138          *
 139          *     mmov t0.8a, t1
 140          *     mmov t0.8b, t2
 141          *     mmov t0.8c, t3
 142          *     mmov t0.8d, t4
 143          *
 144          * as defining the temp within the block, because otherwise dst's live
 145          * range will get extended up the control flow to the top of the
 146          * program.
 147          */
 148         struct partial_update_state *state =
 149                 get_partial_update_state(partial_update_ht, inst);
 150         uint8_t mask = 0xf; /* XXX vir_channels_written(inst); */
 151
 152         if (inst->qpu.flags.ac == V3D_QPU_COND_NONE &&
 153             inst->qpu.flags.mc == V3D_QPU_COND_NONE) {
 154                 state->channels |= mask;
 155         } else {
 156                 for (int i = 0; i < 4; i++) {
 157                         if (!(mask & (1 << i)))
 158                                 continue;
 159
 160                         /* XXXif (state->insts[i] &&
 161                             state->insts[i]->cond ==
 162                             qpu_cond_complement(inst->cond))
 163                                 state->channels |= 1 << i;
 164                         else
 165                         */
 166                                 state->insts[i] = inst;
 167                 }
 168         }
 169
 170         if (state->channels == 0xf)
 171                 BITSET_SET(block->def, var);
 172 }
 173
 174 static void
 175 sf_state_clear(struct hash_table *partial_update_ht)
 176 {
 177         hash_table_foreach(partial_update_ht, entry) {
 178                 struct partial_update_state *state = entry->data;
 179
 180                 for (int i = 0; i < 4; i++) {
 181                         if (state->insts[i] &&
 182                             (state->insts[i]->qpu.flags.ac != V3D_QPU_COND_NONE ||
 183                              state->insts[i]->qpu.flags.mc != V3D_QPU_COND_NONE))
 184                                 state->insts[i] = NULL;
 185                 }
 186         }
 187 }
 188
 189 /* Sets up the def/use arrays for when variables are used-before-defined or
 190  * defined-before-used in the block.
 191  *
 192  * Also initializes the temp_start/temp_end to cover just the instruction IPs
 193  * where the variable is used, which will be extended later in
 194  * vir_compute_start_end().
 195  */
 196 static void
 197 vir_setup_def_use(struct v3d_compile *c)
 198 {
 199         struct hash_table *partial_update_ht =
 200                 _mesa_hash_table_create(c, int_hash, int_compare);
 201         int ip = 0;
 202
 203         vir_for_each_block(block, c) {
 204                 block->start_ip = ip;
 205
 206                 _mesa_hash_table_clear(partial_update_ht, NULL);
 207
 208                 vir_for_each_inst(inst, block) {
 209                         for (int i = 0; i < vir_get_nsrc(inst); i++)
 210                                 vir_setup_use(c, block, ip, inst->src[i]);
 211
 212                         vir_setup_def(c, block, ip, partial_update_ht, inst);
 213
 214                         if (false /* XXX inst->uf */)
 215                                 sf_state_clear(partial_update_ht);
 216
 217                         /* Payload registers: r0/1/2 contain W, centroid W,
 218                          * and Z at program start.  Register allocation will
 219                          * force their nodes to R0/1/2.
 220                          */
 221                         if (inst->src[0].file == QFILE_REG) {
 222                                 switch (inst->src[0].index) {
 223                                 case 0:
 224                                 case 1:
 225                                 case 2:
 226                                         c->temp_start[inst->dst.index] = 0;
 227                                         break;
 228                                 }
 229                         }
 230
 231                         ip++;
 232                 }
 233                 block->end_ip = ip;
 234         }
 235
 236         _mesa_hash_table_destroy(partial_update_ht, NULL);
 237 }
 238
 239 static bool
 240 vir_live_variables_dataflow(struct v3d_compile *c, int bitset_words)
 241 {
 242         bool cont = false;
 243
 244         vir_for_each_block_rev(block, c) {
 245                 /* Update live_out: Any successor using the variable
 246                  * on entrance needs us to have the variable live on
 247                  * exit.
 248                  */
 249                 vir_for_each_successor(succ, block) {
 250                         for (int i = 0; i < bitset_words; i++) {
 251                                 BITSET_WORD new_live_out = (succ->live_in[i] &
 252                                                             ~block->live_out[i]);
 253                                 if (new_live_out) {
 254                                         block->live_out[i] |= new_live_out;
 255                                         cont = true;
 256                                 }
 257                         }
 258                 }
 259
 260                 /* Update live_in */
 261                 for (int i = 0; i < bitset_words; i++) {
 262                         BITSET_WORD new_live_in = (block->use[i] |
 263                                                    (block->live_out[i] &
 264                                                     ~block->def[i]));
 265                         if (new_live_in & ~block->live_in[i]) {
 266                                 block->live_in[i] |= new_live_in;
 267                                 cont = true;
 268                         }
 269                 }
 270         }
 271
 272         return cont;
 273 }
 274
 275 static bool
 276 vir_live_variables_defin_defout_dataflow(struct v3d_compile *c, int bitset_words)
 277 {
 278         bool cont = false;
 279
 280         vir_for_each_block_rev(block, c) {
 281                 /* Propagate defin/defout down the successors to produce the
 282                  * union of blocks with a reachable (partial) definition of
 283                  * the var.
 284                  *
 285                  * This keeps a conditional first write to a reg from
 286                  * extending its lifetime back to the start of the program.
 287                  */
 288                 vir_for_each_successor(succ, block) {
 289                         for (int i = 0; i < bitset_words; i++) {
 290                                 BITSET_WORD new_def = (block->defout[i] &
 291                                                        ~succ->defin[i]);
 292                                 succ->defin[i] |= new_def;
 293                                 succ->defout[i] |= new_def;
 294                                 cont |= new_def;
 295                         }
 296                 }
 297         }
 298
 299         return cont;
 300 }
 301
 302 /**
 303  * Extend the start/end ranges for each variable to account for the
 304  * new information calculated from control flow.
 305  */
 306 static void
 307 vir_compute_start_end(struct v3d_compile *c, int num_vars)
 308 {
 309         vir_for_each_block(block, c) {
 310                 for (int i = 0; i < num_vars; i++) {
 311                         if (BITSET_TEST(block->live_in, i) &&
 312                             BITSET_TEST(block->defin, i)) {
 313                                 c->temp_start[i] = MIN2(c->temp_start[i],
 314                                                         block->start_ip);
 315                                 c->temp_end[i] = MAX2(c->temp_end[i],
 316                                                       block->start_ip);
 317                         }
 318
 319                         if (BITSET_TEST(block->live_out, i) &&
 320                             BITSET_TEST(block->defout, i)) {
 321                                 c->temp_start[i] = MIN2(c->temp_start[i],
 322                                                         block->end_ip);
 323                                 c->temp_end[i] = MAX2(c->temp_end[i],
 324                                                       block->end_ip);
 325                         }
 326                 }
 327         }
 328 }
 329
 330 void
 331 vir_calculate_live_intervals(struct v3d_compile *c)
 332 {
 333         int bitset_words = BITSET_WORDS(c->num_temps);
 334
 335         /* We may be called more than once if we've rearranged the program to
 336          * try to get register allocation to succeed.
 337          */
 338         if (c->temp_start) {
 339                 ralloc_free(c->temp_start);
 340                 ralloc_free(c->temp_end);
 341
 342                 vir_for_each_block(block, c) {
 343                         ralloc_free(block->def);
 344                         ralloc_free(block->use);
 345                         ralloc_free(block->live_in);
 346                         ralloc_free(block->live_out);
 347                 }
 348         }
 349
 350         c->temp_start = rzalloc_array(c, int, c->num_temps);
 351         c->temp_end = rzalloc_array(c, int, c->num_temps);
 352
 353         for (int i = 0; i < c->num_temps; i++) {
 354                 c->temp_start[i] = MAX_INSTRUCTION;
 355                 c->temp_end[i] = -1;
 356         }
 357
 358         vir_for_each_block(block, c) {
 359                 block->def = rzalloc_array(c, BITSET_WORD, bitset_words);
 360                 block->defin = rzalloc_array(c, BITSET_WORD, bitset_words);
 361                 block->defout = rzalloc_array(c, BITSET_WORD, bitset_words);
 362                 block->use = rzalloc_array(c, BITSET_WORD, bitset_words);
 363                 block->live_in = rzalloc_array(c, BITSET_WORD, bitset_words);
 364                 block->live_out = rzalloc_array(c, BITSET_WORD, bitset_words);
 365         }
 366
 367         vir_setup_def_use(c);
 368
 369         while (vir_live_variables_dataflow(c, bitset_words))
 370                 ;
 371
 372         while (vir_live_variables_defin_defout_dataflow(c, bitset_words))
 373                 ;
 374
 375         vir_compute_start_end(c, c->num_temps);
 376
 377         c->live_intervals_valid = true;
 378 }