src/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 "glsl_types.h"
  49
  50 static bool debug = false;
  51
  52 namespace {
  53
  54 class acp_entry : public exec_node
  55 {
  56 public:
  57    acp_entry(ir_variable *lhs, ir_variable *rhs, int write_mask, int swizzle[4])
  58    {
  59       this->lhs = lhs;
  60       this->rhs = rhs;
  61       this->write_mask = write_mask;
  62       memcpy(this->swizzle, swizzle, sizeof(this->swizzle));
  63    }
  64
  65    acp_entry(acp_entry *a)
  66    {
  67       this->lhs = a->lhs;
  68       this->rhs = a->rhs;
  69       this->write_mask = a->write_mask;
  70       memcpy(this->swizzle, a->swizzle, sizeof(this->swizzle));
  71    }
  72
  73    ir_variable *lhs;
  74    ir_variable *rhs;
  75    unsigned int write_mask;
  76    int swizzle[4];
  77 };
  78
  79
  80 class kill_entry : public exec_node
  81 {
  82 public:
  83    kill_entry(ir_variable *var, int write_mask)
  84    {
  85       this->var = var;
  86       this->write_mask = write_mask;
  87    }
  88
  89    ir_variable *var;
  90    unsigned int write_mask;
  91 };
  92
  93 class ir_copy_propagation_elements_visitor : public ir_rvalue_visitor {
  94 public:
  95    ir_copy_propagation_elements_visitor()
  96    {
  97       this->progress = false;
  98       this->killed_all = false;
  99       this->mem_ctx = ralloc_context(NULL);
 100       this->shader_mem_ctx = NULL;
 101       this->acp = new(mem_ctx) exec_list;
 102       this->kills = new(mem_ctx) exec_list;
 103    }
 104    ~ir_copy_propagation_elements_visitor()
 105    {
 106       ralloc_free(mem_ctx);
 107    }
 108
 109    virtual ir_visitor_status visit_enter(class ir_loop *);
 110    virtual ir_visitor_status visit_enter(class ir_function_signature *);
 111    virtual ir_visitor_status visit_leave(class ir_assignment *);
 112    virtual ir_visitor_status visit_enter(class ir_call *);
 113    virtual ir_visitor_status visit_enter(class ir_if *);
 114    virtual ir_visitor_status visit_leave(class ir_swizzle *);
 115
 116    void handle_rvalue(ir_rvalue **rvalue);
 117
 118    void add_copy(ir_assignment *ir);
 119    void kill(kill_entry *k);
 120    void handle_if_block(exec_list *instructions);
 121
 122    /** List of acp_entry: The available copies to propagate */
 123    exec_list *acp;
 124    /**
 125     * List of kill_entry: The variables whose values were killed in this
 126     * block.
 127     */
 128    exec_list *kills;
 129
 130    bool progress;
 131
 132    bool killed_all;
 133
 134    /* Context for our local data structures. */
 135    void *mem_ctx;
 136    /* Context for allocating new shader nodes. */
 137    void *shader_mem_ctx;
 138 };
 139
 140 } /* unnamed namespace */
 141
 142 ir_visitor_status
 143 ir_copy_propagation_elements_visitor::visit_enter(ir_function_signature *ir)
 144 {
 145    /* Treat entry into a function signature as a completely separate
 146     * block.  Any instructions at global scope will be shuffled into
 147     * main() at link time, so they're irrelevant to us.
 148     */
 149    exec_list *orig_acp = this->acp;
 150    exec_list *orig_kills = this->kills;
 151    bool orig_killed_all = this->killed_all;
 152
 153    this->acp = new(mem_ctx) exec_list;
 154    this->kills = new(mem_ctx) exec_list;
 155    this->killed_all = false;
 156
 157    visit_list_elements(this, &ir->body);
 158
 159    this->kills = orig_kills;
 160    this->acp = orig_acp;
 161    this->killed_all = orig_killed_all;
 162
 163    return visit_continue_with_parent;
 164 }
 165
 166 ir_visitor_status
 167 ir_copy_propagation_elements_visitor::visit_leave(ir_assignment *ir)
 168 {
 169    ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
 170    ir_variable *var = ir->lhs->variable_referenced();
 171
 172    if (var->type->is_scalar() || var->type->is_vector()) {
 173       kill_entry *k;
 174
 175       if (lhs)
 176          k = new(mem_ctx) kill_entry(var, ir->write_mask);
 177       else
 178          k = new(mem_ctx) kill_entry(var, ~0);
 179
 180       kill(k);
 181    }
 182
 183    add_copy(ir);
 184
 185    return visit_continue;
 186 }
 187
 188 ir_visitor_status
 189 ir_copy_propagation_elements_visitor::visit_leave(ir_swizzle *ir)
 190 {
 191    /* Don't visit the values of swizzles since they are handled while
 192     * visiting the swizzle itself.
 193     */
 194    return visit_continue;
 195 }
 196
 197 /**
 198  * Replaces dereferences of ACP RHS variables with ACP LHS variables.
 199  *
 200  * This is where the actual copy propagation occurs.  Note that the
 201  * rewriting of ir_dereference means that the ir_dereference instance
 202  * must not be shared by multiple IR operations!
 203  */
 204 void
 205 ir_copy_propagation_elements_visitor::handle_rvalue(ir_rvalue **ir)
 206 {
 207    int swizzle_chan[4];
 208    ir_dereference_variable *deref_var;
 209    ir_variable *source[4] = {NULL, NULL, NULL, NULL};
 210    int source_chan[4];
 211    int chans;
 212
 213    if (!*ir)
 214       return;
 215
 216    ir_swizzle *swizzle = (*ir)->as_swizzle();
 217    if (swizzle) {
 218       deref_var = swizzle->val->as_dereference_variable();
 219       if (!deref_var)
 220          return;
 221
 222       swizzle_chan[0] = swizzle->mask.x;
 223       swizzle_chan[1] = swizzle->mask.y;
 224       swizzle_chan[2] = swizzle->mask.z;
 225       swizzle_chan[3] = swizzle->mask.w;
 226       chans = swizzle->type->vector_elements;
 227    } else {
 228       deref_var = (*ir)->as_dereference_variable();
 229       if (!deref_var)
 230          return;
 231
 232       swizzle_chan[0] = 0;
 233       swizzle_chan[1] = 1;
 234       swizzle_chan[2] = 2;
 235       swizzle_chan[3] = 3;
 236       chans = deref_var->type->vector_elements;
 237    }
 238
 239    if (this->in_assignee)
 240       return;
 241
 242    ir_variable *var = deref_var->var;
 243
 244    /* Try to find ACP entries covering swizzle_chan[], hoping they're
 245     * the same source variable.
 246     */
 247    foreach_iter(exec_list_iterator, iter, *this->acp) {
 248       acp_entry *entry = (acp_entry *)iter.get();
 249
 250       if (var == entry->lhs) {
 251          for (int c = 0; c < chans; c++) {
 252             if (entry->write_mask & (1 << swizzle_chan[c])) {
 253                source[c] = entry->rhs;
 254                source_chan[c] = entry->swizzle[swizzle_chan[c]];
 255             }
 256          }
 257       }
 258    }
 259
 260    /* Make sure all channels are copying from the same source variable. */
 261    if (!source[0])
 262       return;
 263    for (int c = 1; c < chans; c++) {
 264       if (source[c] != source[0])
 265          return;
 266    }
 267
 268    if (!shader_mem_ctx)
 269       shader_mem_ctx = ralloc_parent(deref_var);
 270
 271    if (debug) {
 272       printf("Copy propagation from:\n");
 273       (*ir)->print();
 274    }
 275
 276    deref_var = new(shader_mem_ctx) ir_dereference_variable(source[0]);
 277    *ir = new(shader_mem_ctx) ir_swizzle(deref_var,
 278                                         source_chan[0],
 279                                         source_chan[1],
 280                                         source_chan[2],
 281                                         source_chan[3],
 282                                         chans);
 283
 284    if (debug) {
 285       printf("to:\n");
 286       (*ir)->print();
 287       printf("\n");
 288    }
 289 }
 290
 291
 292 ir_visitor_status
 293 ir_copy_propagation_elements_visitor::visit_enter(ir_call *ir)
 294 {
 295    /* Do copy propagation on call parameters, but skip any out params */
 296    exec_list_iterator sig_param_iter = ir->callee->parameters.iterator();
 297    foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {
 298       ir_variable *sig_param = (ir_variable *)sig_param_iter.get();
 299       ir_instruction *ir = (ir_instruction *)iter.get();
 300       if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) {
 301          ir->accept(this);
 302       }
 303       sig_param_iter.next();
 304    }
 305
 306    /* Since we're unlinked, we don't (necessarily) know the side effects of
 307     * this call.  So kill all copies.
 308     */
 309    acp->make_empty();
 310    this->killed_all = true;
 311
 312    return visit_continue_with_parent;
 313 }
 314
 315 void
 316 ir_copy_propagation_elements_visitor::handle_if_block(exec_list *instructions)
 317 {
 318    exec_list *orig_acp = this->acp;
 319    exec_list *orig_kills = this->kills;
 320    bool orig_killed_all = this->killed_all;
 321
 322    this->acp = new(mem_ctx) exec_list;
 323    this->kills = new(mem_ctx) exec_list;
 324    this->killed_all = false;
 325
 326    /* Populate the initial acp with a copy of the original */
 327    foreach_iter(exec_list_iterator, iter, *orig_acp) {
 328       acp_entry *a = (acp_entry *)iter.get();
 329       this->acp->push_tail(new(this->mem_ctx) acp_entry(a));
 330    }
 331
 332    visit_list_elements(this, instructions);
 333
 334    if (this->killed_all) {
 335       orig_acp->make_empty();
 336    }
 337
 338    exec_list *new_kills = this->kills;
 339    this->kills = orig_kills;
 340    this->acp = orig_acp;
 341    this->killed_all = this->killed_all || orig_killed_all;
 342
 343    /* Move the new kills into the parent block's list, removing them
 344     * from the parent's ACP list in the process.
 345     */
 346    foreach_list_safe(node, new_kills) {
 347       kill_entry *k = (kill_entry *)node;
 348       kill(k);
 349    }
 350 }
 351
 352 ir_visitor_status
 353 ir_copy_propagation_elements_visitor::visit_enter(ir_if *ir)
 354 {
 355    ir->condition->accept(this);
 356
 357    handle_if_block(&ir->then_instructions);
 358    handle_if_block(&ir->else_instructions);
 359
 360    /* handle_if_block() already descended into the children. */
 361    return visit_continue_with_parent;
 362 }
 363
 364 ir_visitor_status
 365 ir_copy_propagation_elements_visitor::visit_enter(ir_loop *ir)
 366 {
 367    exec_list *orig_acp = this->acp;
 368    exec_list *orig_kills = this->kills;
 369    bool orig_killed_all = this->killed_all;
 370
 371    /* FINISHME: For now, the initial acp for loops is totally empty.
 372     * We could go through once, then go through again with the acp
 373     * cloned minus the killed entries after the first run through.
 374     */
 375    this->acp = new(mem_ctx) exec_list;
 376    this->kills = new(mem_ctx) exec_list;
 377    this->killed_all = false;
 378
 379    visit_list_elements(this, &ir->body_instructions);
 380
 381    if (this->killed_all) {
 382       orig_acp->make_empty();
 383    }
 384
 385    exec_list *new_kills = this->kills;
 386    this->kills = orig_kills;
 387    this->acp = orig_acp;
 388    this->killed_all = this->killed_all || orig_killed_all;
 389
 390    foreach_list_safe(node, new_kills) {
 391       kill_entry *k = (kill_entry *)node;
 392       kill(k);
 393    }
 394
 395    /* already descended into the children. */
 396    return visit_continue_with_parent;
 397 }
 398
 399 /* Remove any entries currently in the ACP for this kill. */
 400 void
 401 ir_copy_propagation_elements_visitor::kill(kill_entry *k)
 402 {
 403    foreach_list_safe(node, acp) {
 404       acp_entry *entry = (acp_entry *)node;
 405
 406       if (entry->lhs == k->var) {
 407          entry->write_mask = entry->write_mask & ~k->write_mask;
 408          if (entry->write_mask == 0) {
 409             entry->remove();
 410             continue;
 411          }
 412       }
 413       if (entry->rhs == k->var) {
 414          entry->remove();
 415       }
 416    }
 417
 418    /* If we were on a list, remove ourselves before inserting */
 419    if (k->next)
 420       k->remove();
 421
 422    this->kills->push_tail(k);
 423 }
 424
 425 /**
 426  * Adds directly-copied channels between vector variables to the available
 427  * copy propagation list.
 428  */
 429 void
 430 ir_copy_propagation_elements_visitor::add_copy(ir_assignment *ir)
 431 {
 432    acp_entry *entry;
 433    int orig_swizzle[4] = {0, 1, 2, 3};
 434    int swizzle[4];
 435
 436    if (ir->condition)
 437       return;
 438
 439    ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
 440    if (!lhs || !(lhs->type->is_scalar() || lhs->type->is_vector()))
 441       return;
 442
 443    ir_dereference_variable *rhs = ir->rhs->as_dereference_variable();
 444    if (!rhs) {
 445       ir_swizzle *swiz = ir->rhs->as_swizzle();
 446       if (!swiz)
 447          return;
 448
 449       rhs = swiz->val->as_dereference_variable();
 450       if (!rhs)
 451          return;
 452
 453       orig_swizzle[0] = swiz->mask.x;
 454       orig_swizzle[1] = swiz->mask.y;
 455       orig_swizzle[2] = swiz->mask.z;
 456       orig_swizzle[3] = swiz->mask.w;
 457    }
 458
 459    /* Move the swizzle channels out to the positions they match in the
 460     * destination.  We don't want to have to rewrite the swizzle[]
 461     * array every time we clear a bit of the write_mask.
 462     */
 463    int j = 0;
 464    for (int i = 0; i < 4; i++) {
 465       if (ir->write_mask & (1 << i))
 466          swizzle[i] = orig_swizzle[j++];
 467    }
 468
 469    int write_mask = ir->write_mask;
 470    if (lhs->var == rhs->var) {
 471       /* If this is a copy from the variable to itself, then we need
 472        * to be sure not to include the updated channels from this
 473        * instruction in the set of new source channels to be
 474        * copy-propagated from.
 475        */
 476       for (int i = 0; i < 4; i++) {
 477          if (ir->write_mask & (1 << orig_swizzle[i]))
 478             write_mask &= ~(1 << i);
 479       }
 480    }
 481
 482    entry = new(this->mem_ctx) acp_entry(lhs->var, rhs->var, write_mask,
 483                                         swizzle);
 484    this->acp->push_tail(entry);
 485 }
 486
 487 bool
 488 do_copy_propagation_elements(exec_list *instructions)
 489 {
 490    ir_copy_propagation_elements_visitor v;
 491
 492    visit_list_elements(&v, instructions);
 493
 494    return v.progress;
 495 }