src/compiler/glsl/opt_copy_propagation_elements.cpp

   1 /*
   2  * Copyright © 2010 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
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * \file opt_copy_propagation_elements.cpp
  26  *
  27  * Replaces usage of recently-copied components of variables with the
  28  * previous copy of the variable.
  29  *
  30  * This pass can be compared with opt_copy_propagation, which operands
  31  * on arbitrary whole-variable copies.  However, in order to handle
  32  * the copy propagation of swizzled variables or writemasked writes,
  33  * we want to track things on a channel-wise basis.  I found that
  34  * trying to mix the swizzled/writemasked support here with the
  35  * whole-variable stuff in opt_copy_propagation.cpp just made a mess,
  36  * so this is separate despite the ACP handling being somewhat
  37  * similar.
  38  *
  39  * This should reduce the number of MOV instructions in the generated
  40  * programs unless copy propagation is also done on the LIR, and may
  41  * help anyway by triggering other optimizations that live in the HIR.
  42  */
  43
  44 #include "ir.h"
  45 #include "ir_rvalue_visitor.h"
  46 #include "ir_basic_block.h"
  47 #include "ir_optimization.h"
  48 #include "compiler/glsl_types.h"
  49 #include "util/hash_table.h"
  50
  51 static bool debug = false;
  52
  53 namespace {
  54
  55 class acp_entry;
  56
  57 /* Class that refers to acp_entry in another exec_list. Used
  58  * when making removals based on rhs.
  59  */
  60 class acp_ref : public exec_node
  61 {
  62 public:
  63    acp_ref(acp_entry *e)
  64    {
  65       entry = e;
  66    }
  67    acp_entry *entry;
  68 };
  69
  70 class acp_entry : public exec_node
  71 {
  72 public:
  73    acp_entry(ir_variable *lhs, ir_variable *rhs, int write_mask, int swizzle[4])
  74       : rhs_node(this)
  75    {
  76       this->lhs = lhs;
  77       this->rhs = rhs;
  78       this->write_mask = write_mask;
  79       memcpy(this->swizzle, swizzle, sizeof(this->swizzle));
  80    }
  81
  82    ir_variable *lhs;
  83    ir_variable *rhs;
  84    unsigned int write_mask;
  85    int swizzle[4];
  86    acp_ref rhs_node;
  87 };
  88
  89
  90 class kill_entry : public exec_node
  91 {
  92 public:
  93    kill_entry(ir_variable *var, int write_mask)
  94    {
  95       this->var = var;
  96       this->write_mask = write_mask;
  97    }
  98
  99    ir_variable *var;
 100    unsigned int write_mask;
 101 };
 102
 103 class ir_copy_propagation_elements_visitor : public ir_rvalue_visitor {
 104 public:
 105    ir_copy_propagation_elements_visitor()
 106    {
 107       this->progress = false;
 108       this->killed_all = false;
 109       this->mem_ctx = ralloc_context(NULL);
 110       this->shader_mem_ctx = NULL;
 111       this->kills = new(mem_ctx) exec_list;
 112
 113       create_acp();
 114    }
 115    ~ir_copy_propagation_elements_visitor()
 116    {
 117       ralloc_free(mem_ctx);
 118    }
 119
 120    void create_acp()
 121    {
 122       lhs_ht = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
 123                                        _mesa_key_pointer_equal);
 124       rhs_ht = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
 125                                        _mesa_key_pointer_equal);
 126    }
 127
 128    void destroy_acp()
 129    {
 130       _mesa_hash_table_destroy(lhs_ht, NULL);
 131       _mesa_hash_table_destroy(rhs_ht, NULL);
 132    }
 133
 134    void populate_acp(hash_table *lhs, hash_table *rhs)
 135    {
 136       struct hash_entry *entry;
 137
 138       hash_table_foreach(lhs, entry) {
 139          _mesa_hash_table_insert(lhs_ht, entry->key, entry->data);
 140       }
 141
 142       hash_table_foreach(rhs, entry) {
 143          _mesa_hash_table_insert(rhs_ht, entry->key, entry->data);
 144       }
 145    }
 146
 147    void handle_loop(ir_loop *, bool keep_acp);
 148    virtual ir_visitor_status visit_enter(class ir_loop *);
 149    virtual ir_visitor_status visit_enter(class ir_function_signature *);
 150    virtual ir_visitor_status visit_leave(class ir_assignment *);
 151    virtual ir_visitor_status visit_enter(class ir_call *);
 152    virtual ir_visitor_status visit_enter(class ir_if *);
 153    virtual ir_visitor_status visit_leave(class ir_swizzle *);
 154
 155    void handle_rvalue(ir_rvalue **rvalue);
 156
 157    void add_copy(ir_assignment *ir);
 158    void kill(kill_entry *k);
 159    void handle_if_block(exec_list *instructions);
 160
 161    /** Hash of acp_entry: The available copies to propagate */
 162    hash_table *lhs_ht;
 163    hash_table *rhs_ht;
 164
 165    /**
 166     * List of kill_entry: The variables whose values were killed in this
 167     * block.
 168     */
 169    exec_list *kills;
 170
 171    bool progress;
 172
 173    bool killed_all;
 174
 175    /* Context for our local data structures. */
 176    void *mem_ctx;
 177    /* Context for allocating new shader nodes. */
 178    void *shader_mem_ctx;
 179 };
 180
 181 } /* unnamed namespace */
 182
 183 ir_visitor_status
 184 ir_copy_propagation_elements_visitor::visit_enter(ir_function_signature *ir)
 185 {
 186    /* Treat entry into a function signature as a completely separate
 187     * block.  Any instructions at global scope will be shuffled into
 188     * main() at link time, so they're irrelevant to us.
 189     */
 190    exec_list *orig_kills = this->kills;
 191    bool orig_killed_all = this->killed_all;
 192
 193    hash_table *orig_lhs_ht = lhs_ht;
 194    hash_table *orig_rhs_ht = rhs_ht;
 195
 196    this->kills = new(mem_ctx) exec_list;
 197    this->killed_all = false;
 198
 199    create_acp();
 200
 201    visit_list_elements(this, &ir->body);
 202
 203    ralloc_free(this->kills);
 204
 205    destroy_acp();
 206
 207    this->kills = orig_kills;
 208    this->killed_all = orig_killed_all;
 209
 210    lhs_ht = orig_lhs_ht;
 211    rhs_ht = orig_rhs_ht;
 212
 213    return visit_continue_with_parent;
 214 }
 215
 216 ir_visitor_status
 217 ir_copy_propagation_elements_visitor::visit_leave(ir_assignment *ir)
 218 {
 219    ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
 220    ir_variable *var = ir->lhs->variable_referenced();
 221
 222    if (var->type->is_scalar() || var->type->is_vector()) {
 223       kill_entry *k;
 224
 225       if (lhs)
 226          k = new(this->kills) kill_entry(var, ir->write_mask);
 227       else
 228          k = new(this->kills) kill_entry(var, ~0);
 229
 230       kill(k);
 231    }
 232
 233    add_copy(ir);
 234
 235    return visit_continue;
 236 }
 237
 238 ir_visitor_status
 239 ir_copy_propagation_elements_visitor::visit_leave(ir_swizzle *)
 240 {
 241    /* Don't visit the values of swizzles since they are handled while
 242     * visiting the swizzle itself.
 243     */
 244    return visit_continue;
 245 }
 246
 247 /**
 248  * Replaces dereferences of ACP RHS variables with ACP LHS variables.
 249  *
 250  * This is where the actual copy propagation occurs.  Note that the
 251  * rewriting of ir_dereference means that the ir_dereference instance
 252  * must not be shared by multiple IR operations!
 253  */
 254 void
 255 ir_copy_propagation_elements_visitor::handle_rvalue(ir_rvalue **ir)
 256 {
 257    int swizzle_chan[4];
 258    ir_dereference_variable *deref_var;
 259    ir_variable *source[4] = {NULL, NULL, NULL, NULL};
 260    int source_chan[4] = {0, 0, 0, 0};
 261    int chans;
 262    bool noop_swizzle = true;
 263
 264    if (!*ir)
 265       return;
 266
 267    ir_swizzle *swizzle = (*ir)->as_swizzle();
 268    if (swizzle) {
 269       deref_var = swizzle->val->as_dereference_variable();
 270       if (!deref_var)
 271          return;
 272
 273       swizzle_chan[0] = swizzle->mask.x;
 274       swizzle_chan[1] = swizzle->mask.y;
 275       swizzle_chan[2] = swizzle->mask.z;
 276       swizzle_chan[3] = swizzle->mask.w;
 277       chans = swizzle->type->vector_elements;
 278    } else {
 279       deref_var = (*ir)->as_dereference_variable();
 280       if (!deref_var)
 281          return;
 282
 283       swizzle_chan[0] = 0;
 284       swizzle_chan[1] = 1;
 285       swizzle_chan[2] = 2;
 286       swizzle_chan[3] = 3;
 287       chans = deref_var->type->vector_elements;
 288    }
 289
 290    if (this->in_assignee)
 291       return;
 292
 293    ir_variable *var = deref_var->var;
 294
 295    /* Try to find ACP entries covering swizzle_chan[], hoping they're
 296     * the same source variable.
 297     */
 298    hash_entry *ht_entry = _mesa_hash_table_search(lhs_ht, var);
 299    if (ht_entry) {
 300       exec_list *ht_list = (exec_list *) ht_entry->data;
 301       foreach_in_list(acp_entry, entry, ht_list) {
 302          for (int c = 0; c < chans; c++) {
 303             if (entry->write_mask & (1 << swizzle_chan[c])) {
 304                source[c] = entry->rhs;
 305                source_chan[c] = entry->swizzle[swizzle_chan[c]];
 306
 307                if (source_chan[c] != swizzle_chan[c])
 308                   noop_swizzle = false;
 309             }
 310          }
 311       }
 312    }
 313
 314    /* Make sure all channels are copying from the same source variable. */
 315    if (!source[0])
 316       return;
 317    for (int c = 1; c < chans; c++) {
 318       if (source[c] != source[0])
 319          return;
 320    }
 321
 322    if (!shader_mem_ctx)
 323       shader_mem_ctx = ralloc_parent(deref_var);
 324
 325    /* Don't pointlessly replace the rvalue with itself (or a noop swizzle
 326     * of itself, which would just be deleted by opt_noop_swizzle).
 327     */
 328    if (source[0] == var && noop_swizzle)
 329       return;
 330
 331    if (debug) {
 332       printf("Copy propagation from:\n");
 333       (*ir)->print();
 334    }
 335
 336    deref_var = new(shader_mem_ctx) ir_dereference_variable(source[0]);
 337    *ir = new(shader_mem_ctx) ir_swizzle(deref_var,
 338                                         source_chan[0],
 339                                         source_chan[1],
 340                                         source_chan[2],
 341                                         source_chan[3],
 342                                         chans);
 343    progress = true;
 344
 345    if (debug) {
 346       printf("to:\n");
 347       (*ir)->print();
 348       printf("\n");
 349    }
 350 }
 351
 352
 353 ir_visitor_status
 354 ir_copy_propagation_elements_visitor::visit_enter(ir_call *ir)
 355 {
 356    /* Do copy propagation on call parameters, but skip any out params */
 357    foreach_two_lists(formal_node, &ir->callee->parameters,
 358                      actual_node, &ir->actual_parameters) {
 359       ir_variable *sig_param = (ir_variable *) formal_node;
 360       ir_rvalue *ir = (ir_rvalue *) actual_node;
 361       if (sig_param->data.mode != ir_var_function_out
 362           && sig_param->data.mode != ir_var_function_inout) {
 363          ir->accept(this);
 364       }
 365    }
 366
 367    /* Since we're unlinked, we don't (necessarily) know the side effects of
 368     * this call.  So kill all copies.
 369     */
 370    _mesa_hash_table_clear(lhs_ht, NULL);
 371    _mesa_hash_table_clear(rhs_ht, NULL);
 372
 373    this->killed_all = true;
 374
 375    return visit_continue_with_parent;
 376 }
 377
 378 void
 379 ir_copy_propagation_elements_visitor::handle_if_block(exec_list *instructions)
 380 {
 381    exec_list *orig_kills = this->kills;
 382    bool orig_killed_all = this->killed_all;
 383
 384    hash_table *orig_lhs_ht = lhs_ht;
 385    hash_table *orig_rhs_ht = rhs_ht;
 386
 387    this->kills = new(mem_ctx) exec_list;
 388    this->killed_all = false;
 389
 390    create_acp();
 391
 392    /* Populate the initial acp with a copy of the original */
 393    populate_acp(orig_lhs_ht, orig_rhs_ht);
 394
 395    visit_list_elements(this, instructions);
 396
 397    if (this->killed_all) {
 398       _mesa_hash_table_clear(orig_lhs_ht, NULL);
 399       _mesa_hash_table_clear(orig_rhs_ht, NULL);
 400    }
 401
 402    exec_list *new_kills = this->kills;
 403    this->kills = orig_kills;
 404    this->killed_all = this->killed_all || orig_killed_all;
 405
 406    destroy_acp();
 407
 408    lhs_ht = orig_lhs_ht;
 409    rhs_ht = orig_rhs_ht;
 410
 411    /* Move the new kills into the parent block's list, removing them
 412     * from the parent's ACP list in the process.
 413     */
 414    foreach_in_list_safe(kill_entry, k, new_kills) {
 415       kill(k);
 416    }
 417
 418    ralloc_free(new_kills);
 419 }
 420
 421 ir_visitor_status
 422 ir_copy_propagation_elements_visitor::visit_enter(ir_if *ir)
 423 {
 424    ir->condition->accept(this);
 425
 426    handle_if_block(&ir->then_instructions);
 427    handle_if_block(&ir->else_instructions);
 428
 429    /* handle_if_block() already descended into the children. */
 430    return visit_continue_with_parent;
 431 }
 432
 433 void
 434 ir_copy_propagation_elements_visitor::handle_loop(ir_loop *ir, bool keep_acp)
 435 {
 436    exec_list *orig_kills = this->kills;
 437    bool orig_killed_all = this->killed_all;
 438
 439    hash_table *orig_lhs_ht = lhs_ht;
 440    hash_table *orig_rhs_ht = rhs_ht;
 441
 442    /* FINISHME: For now, the initial acp for loops is totally empty.
 443     * We could go through once, then go through again with the acp
 444     * cloned minus the killed entries after the first run through.
 445     */
 446    this->kills = new(mem_ctx) exec_list;
 447    this->killed_all = false;
 448
 449    create_acp();
 450
 451    if (keep_acp) {
 452       /* Populate the initial acp with a copy of the original */
 453       populate_acp(orig_lhs_ht, orig_rhs_ht);
 454    }
 455
 456    visit_list_elements(this, &ir->body_instructions);
 457
 458    if (this->killed_all) {
 459       _mesa_hash_table_clear(orig_lhs_ht, NULL);
 460       _mesa_hash_table_clear(orig_rhs_ht, NULL);
 461    }
 462
 463    exec_list *new_kills = this->kills;
 464    this->kills = orig_kills;
 465    this->killed_all = this->killed_all || orig_killed_all;
 466
 467    destroy_acp();
 468
 469    lhs_ht = orig_lhs_ht;
 470    rhs_ht = orig_rhs_ht;
 471
 472    foreach_in_list_safe(kill_entry, k, new_kills) {
 473       kill(k);
 474    }
 475
 476    ralloc_free(new_kills);
 477 }
 478
 479 ir_visitor_status
 480 ir_copy_propagation_elements_visitor::visit_enter(ir_loop *ir)
 481 {
 482    handle_loop(ir, false);
 483    handle_loop(ir, true);
 484
 485    /* already descended into the children. */
 486    return visit_continue_with_parent;
 487 }
 488
 489 /* Remove any entries currently in the ACP for this kill. */
 490 void
 491 ir_copy_propagation_elements_visitor::kill(kill_entry *k)
 492 {
 493    /* removal of lhs entries */
 494    hash_entry *ht_entry = _mesa_hash_table_search(lhs_ht, k->var);
 495    if (ht_entry) {
 496       exec_list *lhs_list = (exec_list *) ht_entry->data;
 497       foreach_in_list_safe(acp_entry, entry, lhs_list) {
 498          entry->write_mask = entry->write_mask & ~k->write_mask;
 499          if (entry->write_mask == 0) {
 500             entry->remove();
 501             continue;
 502          }
 503       }
 504    }
 505
 506    /* removal of rhs entries */
 507    ht_entry = _mesa_hash_table_search(rhs_ht, k->var);
 508    if (ht_entry) {
 509       exec_list *rhs_list = (exec_list *) ht_entry->data;
 510       acp_ref *ref;
 511
 512       while ((ref = (acp_ref *) rhs_list->pop_head()) != NULL) {
 513          acp_entry *entry = ref->entry;
 514
 515          /* If entry is still in a list (not already removed by lhs entry
 516           * removal above), remove it.
 517           */
 518          if (entry->prev || entry->next)
 519             entry->remove();
 520       }
 521    }
 522
 523    /* If we were on a list, remove ourselves before inserting */
 524    if (k->next)
 525       k->remove();
 526
 527    ralloc_steal(this->kills, k);
 528    this->kills->push_tail(k);
 529 }
 530
 531 /**
 532  * Adds directly-copied channels between vector variables to the available
 533  * copy propagation list.
 534  */
 535 void
 536 ir_copy_propagation_elements_visitor::add_copy(ir_assignment *ir)
 537 {
 538    acp_entry *entry;
 539    int orig_swizzle[4] = {0, 1, 2, 3};
 540    int swizzle[4];
 541
 542    if (ir->condition)
 543       return;
 544
 545    ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
 546    if (!lhs || !(lhs->type->is_scalar() || lhs->type->is_vector()))
 547       return;
 548
 549    ir_dereference_variable *rhs = ir->rhs->as_dereference_variable();
 550    if (!rhs) {
 551       ir_swizzle *swiz = ir->rhs->as_swizzle();
 552       if (!swiz)
 553          return;
 554
 555       rhs = swiz->val->as_dereference_variable();
 556       if (!rhs)
 557          return;
 558
 559       orig_swizzle[0] = swiz->mask.x;
 560       orig_swizzle[1] = swiz->mask.y;
 561       orig_swizzle[2] = swiz->mask.z;
 562       orig_swizzle[3] = swiz->mask.w;
 563    }
 564
 565    /* Move the swizzle channels out to the positions they match in the
 566     * destination.  We don't want to have to rewrite the swizzle[]
 567     * array every time we clear a bit of the write_mask.
 568     */
 569    int j = 0;
 570    for (int i = 0; i < 4; i++) {
 571       if (ir->write_mask & (1 << i))
 572          swizzle[i] = orig_swizzle[j++];
 573    }
 574
 575    int write_mask = ir->write_mask;
 576    if (lhs->var == rhs->var) {
 577       /* If this is a copy from the variable to itself, then we need
 578        * to be sure not to include the updated channels from this
 579        * instruction in the set of new source channels to be
 580        * copy-propagated from.
 581        */
 582       for (int i = 0; i < 4; i++) {
 583          if (ir->write_mask & (1 << orig_swizzle[i]))
 584             write_mask &= ~(1 << i);
 585       }
 586    }
 587
 588    if (lhs->var->data.precise != rhs->var->data.precise)
 589       return;
 590
 591    entry = new(this->mem_ctx) acp_entry(lhs->var, rhs->var, write_mask,
 592                                         swizzle);
 593
 594    /* lhs hash, hash of lhs -> acp_entry lists */
 595    hash_entry *ht_entry = _mesa_hash_table_search(lhs_ht, lhs->var);
 596    if (ht_entry) {
 597       exec_list *lhs_list = (exec_list *) ht_entry->data;
 598       lhs_list->push_tail(entry);
 599    } else {
 600       exec_list *lhs_list = new(mem_ctx) exec_list;
 601       lhs_list->push_tail(entry);
 602       _mesa_hash_table_insert(lhs_ht, lhs->var, lhs_list);
 603    }
 604
 605    /* rhs hash, hash of rhs -> acp_entry pointers to lhs lists */
 606    ht_entry = _mesa_hash_table_search(rhs_ht, rhs->var);
 607    if (ht_entry) {
 608       exec_list *rhs_list = (exec_list *) ht_entry->data;
 609       rhs_list->push_tail(&entry->rhs_node);
 610    } else {
 611       exec_list *rhs_list = new(mem_ctx) exec_list;
 612       rhs_list->push_tail(&entry->rhs_node);
 613       _mesa_hash_table_insert(rhs_ht, rhs->var, rhs_list);
 614    }
 615 }
 616
 617 bool
 618 do_copy_propagation_elements(exec_list *instructions)
 619 {
 620    ir_copy_propagation_elements_visitor v;
 621
 622    visit_list_elements(&v, instructions);
 623
 624    return v.progress;
 625 }