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    /* override operator new from exec_node */
  74    DECLARE_LINEAR_ZALLOC_CXX_OPERATORS(acp_entry)
  75
  76    acp_entry(ir_variable *lhs, ir_variable *rhs, int write_mask, int swizzle[4])
  77       : rhs_node(this)
  78    {
  79       this->lhs = lhs;
  80       this->rhs = rhs;
  81       this->write_mask = write_mask;
  82       memcpy(this->swizzle, swizzle, sizeof(this->swizzle));
  83    }
  84
  85    ir_variable *lhs;
  86    ir_variable *rhs;
  87    unsigned int write_mask;
  88    int swizzle[4];
  89    acp_ref rhs_node;
  90 };
  91
  92
  93 class kill_entry : public exec_node
  94 {
  95 public:
  96    /* override operator new from exec_node */
  97    DECLARE_LINEAR_ZALLOC_CXX_OPERATORS(kill_entry)
  98
  99    kill_entry(ir_variable *var, int write_mask)
 100    {
 101       this->var = var;
 102       this->write_mask = write_mask;
 103    }
 104
 105    ir_variable *var;
 106    unsigned int write_mask;
 107 };
 108
 109 class ir_copy_propagation_elements_visitor : public ir_rvalue_visitor {
 110 public:
 111    ir_copy_propagation_elements_visitor()
 112    {
 113       this->progress = false;
 114       this->killed_all = false;
 115       this->mem_ctx = ralloc_context(NULL);
 116       this->lin_ctx = linear_alloc_parent(this->mem_ctx, 0);
 117       this->shader_mem_ctx = NULL;
 118       this->kills = new(mem_ctx) exec_list;
 119
 120       create_acp();
 121    }
 122    ~ir_copy_propagation_elements_visitor()
 123    {
 124       ralloc_free(mem_ctx);
 125    }
 126
 127    void create_acp()
 128    {
 129       lhs_ht = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
 130                                        _mesa_key_pointer_equal);
 131       rhs_ht = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
 132                                        _mesa_key_pointer_equal);
 133    }
 134
 135    void destroy_acp()
 136    {
 137       _mesa_hash_table_destroy(lhs_ht, NULL);
 138       _mesa_hash_table_destroy(rhs_ht, NULL);
 139    }
 140
 141    void populate_acp(hash_table *lhs, hash_table *rhs)
 142    {
 143       struct hash_entry *entry;
 144
 145       hash_table_foreach(lhs, entry) {
 146          _mesa_hash_table_insert(lhs_ht, entry->key, entry->data);
 147       }
 148
 149       hash_table_foreach(rhs, entry) {
 150          _mesa_hash_table_insert(rhs_ht, entry->key, entry->data);
 151       }
 152    }
 153
 154    void handle_loop(ir_loop *, bool keep_acp);
 155    virtual ir_visitor_status visit_enter(class ir_loop *);
 156    virtual ir_visitor_status visit_enter(class ir_function_signature *);
 157    virtual ir_visitor_status visit_leave(class ir_assignment *);
 158    virtual ir_visitor_status visit_enter(class ir_call *);
 159    virtual ir_visitor_status visit_enter(class ir_if *);
 160    virtual ir_visitor_status visit_leave(class ir_swizzle *);
 161
 162    void handle_rvalue(ir_rvalue **rvalue);
 163
 164    void add_copy(ir_assignment *ir);
 165    void kill(kill_entry *k);
 166    void handle_if_block(exec_list *instructions);
 167
 168    /** Hash of acp_entry: The available copies to propagate */
 169    hash_table *lhs_ht;
 170    hash_table *rhs_ht;
 171
 172    /**
 173     * List of kill_entry: The variables whose values were killed in this
 174     * block.
 175     */
 176    exec_list *kills;
 177
 178    bool progress;
 179
 180    bool killed_all;
 181
 182    /* Context for our local data structures. */
 183    void *mem_ctx;
 184    void *lin_ctx;
 185    /* Context for allocating new shader nodes. */
 186    void *shader_mem_ctx;
 187 };
 188
 189 } /* unnamed namespace */
 190
 191 ir_visitor_status
 192 ir_copy_propagation_elements_visitor::visit_enter(ir_function_signature *ir)
 193 {
 194    /* Treat entry into a function signature as a completely separate
 195     * block.  Any instructions at global scope will be shuffled into
 196     * main() at link time, so they're irrelevant to us.
 197     */
 198    exec_list *orig_kills = this->kills;
 199    bool orig_killed_all = this->killed_all;
 200
 201    hash_table *orig_lhs_ht = lhs_ht;
 202    hash_table *orig_rhs_ht = rhs_ht;
 203
 204    this->kills = new(mem_ctx) exec_list;
 205    this->killed_all = false;
 206
 207    create_acp();
 208
 209    visit_list_elements(this, &ir->body);
 210
 211    ralloc_free(this->kills);
 212
 213    destroy_acp();
 214
 215    this->kills = orig_kills;
 216    this->killed_all = orig_killed_all;
 217
 218    lhs_ht = orig_lhs_ht;
 219    rhs_ht = orig_rhs_ht;
 220
 221    return visit_continue_with_parent;
 222 }
 223
 224 ir_visitor_status
 225 ir_copy_propagation_elements_visitor::visit_leave(ir_assignment *ir)
 226 {
 227    ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
 228    ir_variable *var = ir->lhs->variable_referenced();
 229
 230    if (var->type->is_scalar() || var->type->is_vector()) {
 231       kill_entry *k;
 232
 233       if (lhs)
 234          k = new(this->lin_ctx) kill_entry(var, ir->write_mask);
 235       else
 236          k = new(this->lin_ctx) kill_entry(var, ~0);
 237
 238       kill(k);
 239    }
 240
 241    add_copy(ir);
 242
 243    return visit_continue;
 244 }
 245
 246 ir_visitor_status
 247 ir_copy_propagation_elements_visitor::visit_leave(ir_swizzle *)
 248 {
 249    /* Don't visit the values of swizzles since they are handled while
 250     * visiting the swizzle itself.
 251     */
 252    return visit_continue;
 253 }
 254
 255 /**
 256  * Replaces dereferences of ACP RHS variables with ACP LHS variables.
 257  *
 258  * This is where the actual copy propagation occurs.  Note that the
 259  * rewriting of ir_dereference means that the ir_dereference instance
 260  * must not be shared by multiple IR operations!
 261  */
 262 void
 263 ir_copy_propagation_elements_visitor::handle_rvalue(ir_rvalue **ir)
 264 {
 265    int swizzle_chan[4];
 266    ir_dereference_variable *deref_var;
 267    ir_variable *source[4] = {NULL, NULL, NULL, NULL};
 268    int source_chan[4] = {0, 0, 0, 0};
 269    int chans;
 270    bool noop_swizzle = true;
 271
 272    if (!*ir)
 273       return;
 274
 275    ir_swizzle *swizzle = (*ir)->as_swizzle();
 276    if (swizzle) {
 277       deref_var = swizzle->val->as_dereference_variable();
 278       if (!deref_var)
 279          return;
 280
 281       swizzle_chan[0] = swizzle->mask.x;
 282       swizzle_chan[1] = swizzle->mask.y;
 283       swizzle_chan[2] = swizzle->mask.z;
 284       swizzle_chan[3] = swizzle->mask.w;
 285       chans = swizzle->type->vector_elements;
 286    } else {
 287       deref_var = (*ir)->as_dereference_variable();
 288       if (!deref_var)
 289          return;
 290
 291       swizzle_chan[0] = 0;
 292       swizzle_chan[1] = 1;
 293       swizzle_chan[2] = 2;
 294       swizzle_chan[3] = 3;
 295       chans = deref_var->type->vector_elements;
 296    }
 297
 298    if (this->in_assignee)
 299       return;
 300
 301    ir_variable *var = deref_var->var;
 302
 303    /* Try to find ACP entries covering swizzle_chan[], hoping they're
 304     * the same source variable.
 305     */
 306    hash_entry *ht_entry = _mesa_hash_table_search(lhs_ht, var);
 307    if (ht_entry) {
 308       exec_list *ht_list = (exec_list *) ht_entry->data;
 309       foreach_in_list(acp_entry, entry, ht_list) {
 310          for (int c = 0; c < chans; c++) {
 311             if (entry->write_mask & (1 << swizzle_chan[c])) {
 312                source[c] = entry->rhs;
 313                source_chan[c] = entry->swizzle[swizzle_chan[c]];
 314
 315                if (source_chan[c] != swizzle_chan[c])
 316                   noop_swizzle = false;
 317             }
 318          }
 319       }
 320    }
 321
 322    /* Make sure all channels are copying from the same source variable. */
 323    if (!source[0])
 324       return;
 325    for (int c = 1; c < chans; c++) {
 326       if (source[c] != source[0])
 327          return;
 328    }
 329
 330    if (!shader_mem_ctx)
 331       shader_mem_ctx = ralloc_parent(deref_var);
 332
 333    /* Don't pointlessly replace the rvalue with itself (or a noop swizzle
 334     * of itself, which would just be deleted by opt_noop_swizzle).
 335     */
 336    if (source[0] == var && noop_swizzle)
 337       return;
 338
 339    if (debug) {
 340       printf("Copy propagation from:\n");
 341       (*ir)->print();
 342    }
 343
 344    deref_var = new(shader_mem_ctx) ir_dereference_variable(source[0]);
 345    *ir = new(shader_mem_ctx) ir_swizzle(deref_var,
 346                                         source_chan[0],
 347                                         source_chan[1],
 348                                         source_chan[2],
 349                                         source_chan[3],
 350                                         chans);
 351    progress = true;
 352
 353    if (debug) {
 354       printf("to:\n");
 355       (*ir)->print();
 356       printf("\n");
 357    }
 358 }
 359
 360
 361 ir_visitor_status
 362 ir_copy_propagation_elements_visitor::visit_enter(ir_call *ir)
 363 {
 364    /* Do copy propagation on call parameters, but skip any out params */
 365    foreach_two_lists(formal_node, &ir->callee->parameters,
 366                      actual_node, &ir->actual_parameters) {
 367       ir_variable *sig_param = (ir_variable *) formal_node;
 368       ir_rvalue *ir = (ir_rvalue *) actual_node;
 369       if (sig_param->data.mode != ir_var_function_out
 370           && sig_param->data.mode != ir_var_function_inout) {
 371          ir->accept(this);
 372       }
 373    }
 374
 375    /* Since we're unlinked, we don't (necessarily) know the side effects of
 376     * this call.  So kill all copies.
 377     */
 378    _mesa_hash_table_clear(lhs_ht, NULL);
 379    _mesa_hash_table_clear(rhs_ht, NULL);
 380
 381    this->killed_all = true;
 382
 383    return visit_continue_with_parent;
 384 }
 385
 386 void
 387 ir_copy_propagation_elements_visitor::handle_if_block(exec_list *instructions)
 388 {
 389    exec_list *orig_kills = this->kills;
 390    bool orig_killed_all = this->killed_all;
 391
 392    hash_table *orig_lhs_ht = lhs_ht;
 393    hash_table *orig_rhs_ht = rhs_ht;
 394
 395    this->kills = new(mem_ctx) exec_list;
 396    this->killed_all = false;
 397
 398    create_acp();
 399
 400    /* Populate the initial acp with a copy of the original */
 401    populate_acp(orig_lhs_ht, orig_rhs_ht);
 402
 403    visit_list_elements(this, instructions);
 404
 405    if (this->killed_all) {
 406       _mesa_hash_table_clear(orig_lhs_ht, NULL);
 407       _mesa_hash_table_clear(orig_rhs_ht, NULL);
 408    }
 409
 410    exec_list *new_kills = this->kills;
 411    this->kills = orig_kills;
 412    this->killed_all = this->killed_all || orig_killed_all;
 413
 414    destroy_acp();
 415
 416    lhs_ht = orig_lhs_ht;
 417    rhs_ht = orig_rhs_ht;
 418
 419    /* Move the new kills into the parent block's list, removing them
 420     * from the parent's ACP list in the process.
 421     */
 422    foreach_in_list_safe(kill_entry, k, new_kills) {
 423       kill(k);
 424    }
 425
 426    ralloc_free(new_kills);
 427 }
 428
 429 ir_visitor_status
 430 ir_copy_propagation_elements_visitor::visit_enter(ir_if *ir)
 431 {
 432    ir->condition->accept(this);
 433
 434    handle_if_block(&ir->then_instructions);
 435    handle_if_block(&ir->else_instructions);
 436
 437    /* handle_if_block() already descended into the children. */
 438    return visit_continue_with_parent;
 439 }
 440
 441 void
 442 ir_copy_propagation_elements_visitor::handle_loop(ir_loop *ir, bool keep_acp)
 443 {
 444    exec_list *orig_kills = this->kills;
 445    bool orig_killed_all = this->killed_all;
 446
 447    hash_table *orig_lhs_ht = lhs_ht;
 448    hash_table *orig_rhs_ht = rhs_ht;
 449
 450    /* FINISHME: For now, the initial acp for loops is totally empty.
 451     * We could go through once, then go through again with the acp
 452     * cloned minus the killed entries after the first run through.
 453     */
 454    this->kills = new(mem_ctx) exec_list;
 455    this->killed_all = false;
 456
 457    create_acp();
 458
 459    if (keep_acp) {
 460       /* Populate the initial acp with a copy of the original */
 461       populate_acp(orig_lhs_ht, orig_rhs_ht);
 462    }
 463
 464    visit_list_elements(this, &ir->body_instructions);
 465
 466    if (this->killed_all) {
 467       _mesa_hash_table_clear(orig_lhs_ht, NULL);
 468       _mesa_hash_table_clear(orig_rhs_ht, NULL);
 469    }
 470
 471    exec_list *new_kills = this->kills;
 472    this->kills = orig_kills;
 473    this->killed_all = this->killed_all || orig_killed_all;
 474
 475    destroy_acp();
 476
 477    lhs_ht = orig_lhs_ht;
 478    rhs_ht = orig_rhs_ht;
 479
 480    foreach_in_list_safe(kill_entry, k, new_kills) {
 481       kill(k);
 482    }
 483
 484    ralloc_free(new_kills);
 485 }
 486
 487 ir_visitor_status
 488 ir_copy_propagation_elements_visitor::visit_enter(ir_loop *ir)
 489 {
 490    handle_loop(ir, false);
 491    handle_loop(ir, true);
 492
 493    /* already descended into the children. */
 494    return visit_continue_with_parent;
 495 }
 496
 497 /* Remove any entries currently in the ACP for this kill. */
 498 void
 499 ir_copy_propagation_elements_visitor::kill(kill_entry *k)
 500 {
 501    /* removal of lhs entries */
 502    hash_entry *ht_entry = _mesa_hash_table_search(lhs_ht, k->var);
 503    if (ht_entry) {
 504       exec_list *lhs_list = (exec_list *) ht_entry->data;
 505       foreach_in_list_safe(acp_entry, entry, lhs_list) {
 506          entry->write_mask = entry->write_mask & ~k->write_mask;
 507          if (entry->write_mask == 0) {
 508             entry->remove();
 509             continue;
 510          }
 511       }
 512    }
 513
 514    /* removal of rhs entries */
 515    ht_entry = _mesa_hash_table_search(rhs_ht, k->var);
 516    if (ht_entry) {
 517       exec_list *rhs_list = (exec_list *) ht_entry->data;
 518       acp_ref *ref;
 519
 520       while ((ref = (acp_ref *) rhs_list->pop_head()) != NULL) {
 521          acp_entry *entry = ref->entry;
 522
 523          /* If entry is still in a list (not already removed by lhs entry
 524           * removal above), remove it.
 525           */
 526          if (entry->prev || entry->next)
 527             entry->remove();
 528       }
 529    }
 530
 531    /* If we were on a list, remove ourselves before inserting */
 532    if (k->next)
 533       k->remove();
 534
 535    this->kills->push_tail(k);
 536 }
 537
 538 /**
 539  * Adds directly-copied channels between vector variables to the available
 540  * copy propagation list.
 541  */
 542 void
 543 ir_copy_propagation_elements_visitor::add_copy(ir_assignment *ir)
 544 {
 545    acp_entry *entry;
 546    int orig_swizzle[4] = {0, 1, 2, 3};
 547    int swizzle[4];
 548
 549    if (ir->condition)
 550       return;
 551
 552    ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
 553    if (!lhs || !(lhs->type->is_scalar() || lhs->type->is_vector()))
 554       return;
 555
 556    ir_dereference_variable *rhs = ir->rhs->as_dereference_variable();
 557    if (!rhs) {
 558       ir_swizzle *swiz = ir->rhs->as_swizzle();
 559       if (!swiz)
 560          return;
 561
 562       rhs = swiz->val->as_dereference_variable();
 563       if (!rhs)
 564          return;
 565
 566       orig_swizzle[0] = swiz->mask.x;
 567       orig_swizzle[1] = swiz->mask.y;
 568       orig_swizzle[2] = swiz->mask.z;
 569       orig_swizzle[3] = swiz->mask.w;
 570    }
 571
 572    /* Move the swizzle channels out to the positions they match in the
 573     * destination.  We don't want to have to rewrite the swizzle[]
 574     * array every time we clear a bit of the write_mask.
 575     */
 576    int j = 0;
 577    for (int i = 0; i < 4; i++) {
 578       if (ir->write_mask & (1 << i))
 579          swizzle[i] = orig_swizzle[j++];
 580    }
 581
 582    int write_mask = ir->write_mask;
 583    if (lhs->var == rhs->var) {
 584       /* If this is a copy from the variable to itself, then we need
 585        * to be sure not to include the updated channels from this
 586        * instruction in the set of new source channels to be
 587        * copy-propagated from.
 588        */
 589       for (int i = 0; i < 4; i++) {
 590          if (ir->write_mask & (1 << orig_swizzle[i]))
 591             write_mask &= ~(1 << i);
 592       }
 593    }
 594
 595    if (lhs->var->data.precise != rhs->var->data.precise)
 596       return;
 597
 598    entry = new(this->lin_ctx) acp_entry(lhs->var, rhs->var, write_mask,
 599                                         swizzle);
 600
 601    /* lhs hash, hash of lhs -> acp_entry lists */
 602    hash_entry *ht_entry = _mesa_hash_table_search(lhs_ht, lhs->var);
 603    if (ht_entry) {
 604       exec_list *lhs_list = (exec_list *) ht_entry->data;
 605       lhs_list->push_tail(entry);
 606    } else {
 607       exec_list *lhs_list = new(mem_ctx) exec_list;
 608       lhs_list->push_tail(entry);
 609       _mesa_hash_table_insert(lhs_ht, lhs->var, lhs_list);
 610    }
 611
 612    /* rhs hash, hash of rhs -> acp_entry pointers to lhs lists */
 613    ht_entry = _mesa_hash_table_search(rhs_ht, rhs->var);
 614    if (ht_entry) {
 615       exec_list *rhs_list = (exec_list *) ht_entry->data;
 616       rhs_list->push_tail(&entry->rhs_node);
 617    } else {
 618       exec_list *rhs_list = new(mem_ctx) exec_list;
 619       rhs_list->push_tail(&entry->rhs_node);
 620       _mesa_hash_table_insert(rhs_ht, rhs->var, rhs_list);
 621    }
 622 }
 623
 624 bool
 625 do_copy_propagation_elements(exec_list *instructions)
 626 {
 627    ir_copy_propagation_elements_visitor v;
 628
 629    visit_list_elements(&v, instructions);
 630
 631    return v.progress;
 632 }