src/compiler/glsl/opt_array_splitting.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_array_splitting.cpp
  26  *
  27  * If an array is always dereferenced with a constant index, then
  28  * split it apart into its elements, making it more amenable to other
  29  * optimization passes.
  30  *
  31  * This skips uniform/varying arrays, which would need careful
  32  * handling due to their ir->location fields tying them to the GL API
  33  * and other shader stages.
  34  */
  35
  36 #include "ir.h"
  37 #include "ir_visitor.h"
  38 #include "ir_rvalue_visitor.h"
  39 #include "compiler/glsl_types.h"
  40
  41 static bool debug = false;
  42
  43 namespace {
  44
  45 namespace opt_array_splitting {
  46
  47 class variable_entry : public exec_node
  48 {
  49 public:
  50    variable_entry(ir_variable *var)
  51    {
  52       this->var = var;
  53       this->split = true;
  54       this->declaration = false;
  55       this->components = NULL;
  56       this->mem_ctx = NULL;
  57       if (var->type->is_array())
  58          this->size = var->type->length;
  59       else
  60          this->size = var->type->matrix_columns;
  61    }
  62
  63    ir_variable *var; /* The key: the variable's pointer. */
  64    unsigned size; /* array length or matrix columns */
  65
  66    /** Whether this array should be split or not. */
  67    bool split;
  68
  69    /* If the variable had a decl we can work with in the instruction
  70     * stream.  We can't do splitting on function arguments, which
  71     * don't get this variable set.
  72     */
  73    bool declaration;
  74
  75    ir_variable **components;
  76
  77    /** ralloc_parent(this->var) -- the shader's talloc context. */
  78    void *mem_ctx;
  79 };
  80
  81 } /* namespace */
  82
  83 using namespace opt_array_splitting;
  84
  85 /**
  86  * This class does a walk over the tree, coming up with the set of
  87  * variables that could be split by looking to see if they are arrays
  88  * that are only ever constant-index dereferenced.
  89  */
  90 class ir_array_reference_visitor : public ir_hierarchical_visitor {
  91 public:
  92    ir_array_reference_visitor(void)
  93    {
  94       this->mem_ctx = ralloc_context(NULL);
  95       this->variable_list.make_empty();
  96       this->in_whole_array_copy = false;
  97    }
  98
  99    ~ir_array_reference_visitor(void)
 100    {
 101       ralloc_free(mem_ctx);
 102    }
 103
 104    bool get_split_list(exec_list *instructions, bool linked);
 105
 106    virtual ir_visitor_status visit(ir_variable *);
 107    virtual ir_visitor_status visit(ir_dereference_variable *);
 108    virtual ir_visitor_status visit_enter(ir_assignment *);
 109    virtual ir_visitor_status visit_leave(ir_assignment *);
 110    virtual ir_visitor_status visit_enter(ir_dereference_array *);
 111    virtual ir_visitor_status visit_enter(ir_function_signature *);
 112
 113    variable_entry *get_variable_entry(ir_variable *var);
 114
 115    /* List of variable_entry */
 116    exec_list variable_list;
 117
 118    void *mem_ctx;
 119
 120    bool in_whole_array_copy;
 121 };
 122
 123 } /* namespace */
 124
 125 variable_entry *
 126 ir_array_reference_visitor::get_variable_entry(ir_variable *var)
 127 {
 128    assert(var);
 129
 130    if (var->data.mode != ir_var_auto &&
 131        var->data.mode != ir_var_temporary)
 132       return NULL;
 133
 134    if (!(var->type->is_array() || var->type->is_matrix()))
 135       return NULL;
 136
 137    /* If the array hasn't been sized yet, we can't split it.  After
 138     * linking, this should be resolved.
 139     */
 140    if (var->type->is_unsized_array())
 141       return NULL;
 142
 143    foreach_in_list(variable_entry, entry, &this->variable_list) {
 144       if (entry->var == var)
 145          return entry;
 146    }
 147
 148    variable_entry *entry = new(mem_ctx) variable_entry(var);
 149    this->variable_list.push_tail(entry);
 150    return entry;
 151 }
 152
 153
 154 ir_visitor_status
 155 ir_array_reference_visitor::visit(ir_variable *ir)
 156 {
 157    variable_entry *entry = this->get_variable_entry(ir);
 158
 159    if (entry)
 160       entry->declaration = true;
 161
 162    return visit_continue;
 163 }
 164
 165 ir_visitor_status
 166 ir_array_reference_visitor::visit_enter(ir_assignment *ir)
 167 {
 168    in_whole_array_copy =
 169       ir->lhs->type->is_array() && ir->whole_variable_written();
 170
 171    return visit_continue;
 172 }
 173
 174 ir_visitor_status
 175 ir_array_reference_visitor::visit_leave(ir_assignment *ir)
 176 {
 177    in_whole_array_copy = false;
 178
 179    return visit_continue;
 180 }
 181
 182 ir_visitor_status
 183 ir_array_reference_visitor::visit(ir_dereference_variable *ir)
 184 {
 185    variable_entry *entry = this->get_variable_entry(ir->var);
 186
 187    /* Allow whole-array assignments on the LHS.  We can split those
 188     * by "unrolling" the assignment into component-wise assignments.
 189     */
 190    if (in_assignee && in_whole_array_copy)
 191       return visit_continue;
 192
 193    /* If we made it to here without seeing an ir_dereference_array,
 194     * then the dereference of this array didn't have a constant index
 195     * (see the visit_continue_with_parent below), so we can't split
 196     * the variable.
 197     */
 198    if (entry)
 199       entry->split = false;
 200
 201    return visit_continue;
 202 }
 203
 204 ir_visitor_status
 205 ir_array_reference_visitor::visit_enter(ir_dereference_array *ir)
 206 {
 207    ir_dereference_variable *deref = ir->array->as_dereference_variable();
 208    if (!deref)
 209       return visit_continue;
 210
 211    variable_entry *entry = this->get_variable_entry(deref->var);
 212
 213    /* If the access to the array has a variable index, we wouldn't
 214     * know which split variable this dereference should go to.
 215     */
 216    if (!ir->array_index->as_constant()) {
 217       if (entry)
 218          entry->split = false;
 219       /* This variable indexing could come from a different array dereference
 220        * that also has variable indexing, that is, something like a[b[a[b[0]]]].
 221        * If we return visit_continue_with_parent here for the first appearence
 222        * of a, then we can miss that b also has indirect indexing (if this is
 223        * the only place in the program where such indirect indexing into b
 224        * happens), so keep going.
 225        */
 226       return visit_continue;
 227    }
 228
 229    /* If the index is also array dereference, visit index. */
 230    if (ir->array_index->as_dereference_array())
 231       visit_enter(ir->array_index->as_dereference_array());
 232
 233    return visit_continue_with_parent;
 234 }
 235
 236 ir_visitor_status
 237 ir_array_reference_visitor::visit_enter(ir_function_signature *ir)
 238 {
 239    /* We don't have logic for array-splitting function arguments,
 240     * so just look at the body instructions and not the parameter
 241     * declarations.
 242     */
 243    visit_list_elements(this, &ir->body);
 244    return visit_continue_with_parent;
 245 }
 246
 247 bool
 248 ir_array_reference_visitor::get_split_list(exec_list *instructions,
 249                                            bool linked)
 250 {
 251    visit_list_elements(this, instructions);
 252
 253    /* If the shaders aren't linked yet, we can't mess with global
 254     * declarations, which need to be matched by name across shaders.
 255     */
 256    if (!linked) {
 257       foreach_in_list(ir_instruction, node, instructions) {
 258          ir_variable *var = node->as_variable();
 259          if (var) {
 260             variable_entry *entry = get_variable_entry(var);
 261             if (entry)
 262                entry->remove();
 263          }
 264       }
 265    }
 266
 267    /* Trim out variables we found that we can't split. */
 268    foreach_in_list_safe(variable_entry, entry, &variable_list) {
 269       if (debug) {
 270          printf("array %s@%p: decl %d, split %d\n",
 271                 entry->var->name, (void *) entry->var, entry->declaration,
 272                 entry->split);
 273       }
 274
 275       if (!(entry->declaration && entry->split)) {
 276          entry->remove();
 277       }
 278    }
 279
 280    return !variable_list.is_empty();
 281 }
 282
 283 /**
 284  * This class rewrites the dereferences of arrays that have been split
 285  * to use the newly created ir_variables for each component.
 286  */
 287 class ir_array_splitting_visitor : public ir_rvalue_visitor {
 288 public:
 289    ir_array_splitting_visitor(exec_list *vars)
 290    {
 291       this->variable_list = vars;
 292    }
 293
 294    virtual ~ir_array_splitting_visitor()
 295    {
 296    }
 297
 298    virtual ir_visitor_status visit_leave(ir_assignment *);
 299
 300    void split_deref(ir_dereference **deref);
 301    void handle_rvalue(ir_rvalue **rvalue);
 302    variable_entry *get_splitting_entry(ir_variable *var);
 303
 304    exec_list *variable_list;
 305 };
 306
 307 variable_entry *
 308 ir_array_splitting_visitor::get_splitting_entry(ir_variable *var)
 309 {
 310    assert(var);
 311
 312    foreach_in_list(variable_entry, entry, this->variable_list) {
 313       if (entry->var == var) {
 314          return entry;
 315       }
 316    }
 317
 318    return NULL;
 319 }
 320
 321 void
 322 ir_array_splitting_visitor::split_deref(ir_dereference **deref)
 323 {
 324    ir_dereference_array *deref_array = (*deref)->as_dereference_array();
 325    if (!deref_array)
 326       return;
 327
 328    ir_dereference_variable *deref_var = deref_array->array->as_dereference_variable();
 329    if (!deref_var)
 330       return;
 331    ir_variable *var = deref_var->var;
 332
 333    variable_entry *entry = get_splitting_entry(var);
 334    if (!entry)
 335       return;
 336
 337    ir_constant *constant = deref_array->array_index->as_constant();
 338    assert(constant);
 339
 340    if (constant->value.i[0] >= 0 && constant->value.i[0] < (int)entry->size) {
 341       *deref = new(entry->mem_ctx)
 342                ir_dereference_variable(entry->components[constant->value.i[0]]);
 343    } else {
 344       /* There was a constant array access beyond the end of the
 345        * array.  This might have happened due to constant folding
 346        * after the initial parse.  This produces an undefined value,
 347        * but shouldn't crash.  Just give them an uninitialized
 348        * variable.
 349        */
 350       ir_variable *temp = new(entry->mem_ctx) ir_variable(deref_array->type,
 351                                                           "undef",
 352                                                           ir_var_temporary);
 353       entry->components[0]->insert_before(temp);
 354       *deref = new(entry->mem_ctx) ir_dereference_variable(temp);
 355    }
 356 }
 357
 358 void
 359 ir_array_splitting_visitor::handle_rvalue(ir_rvalue **rvalue)
 360 {
 361    if (!*rvalue)
 362       return;
 363
 364    ir_dereference *deref = (*rvalue)->as_dereference();
 365
 366    if (!deref)
 367       return;
 368
 369    split_deref(&deref);
 370    *rvalue = deref;
 371 }
 372
 373 ir_visitor_status
 374 ir_array_splitting_visitor::visit_leave(ir_assignment *ir)
 375 {
 376    /* The normal rvalue visitor skips the LHS of assignments, but we
 377     * need to process those just the same.
 378     */
 379    ir_rvalue *lhs = ir->lhs;
 380
 381    /* "Unroll" any whole array assignments, creating assignments for
 382     * each array element.  Then, do splitting on each new assignment.
 383     */
 384    if (lhs->type->is_array() && ir->whole_variable_written() &&
 385        get_splitting_entry(ir->whole_variable_written())) {
 386       void *mem_ctx = ralloc_parent(ir);
 387
 388       for (unsigned i = 0; i < lhs->type->length; i++) {
 389          ir_rvalue *lhs_i =
 390             new(mem_ctx) ir_dereference_array(ir->lhs->clone(mem_ctx, NULL),
 391                                               new(mem_ctx) ir_constant(i));
 392          ir_rvalue *rhs_i =
 393             new(mem_ctx) ir_dereference_array(ir->rhs->clone(mem_ctx, NULL),
 394                                               new(mem_ctx) ir_constant(i));
 395          ir_rvalue *condition_i =
 396             ir->condition ? ir->condition->clone(mem_ctx, NULL) : NULL;
 397
 398          ir_assignment *assign_i =
 399             new(mem_ctx) ir_assignment(lhs_i, rhs_i, condition_i);
 400
 401          ir->insert_before(assign_i);
 402          assign_i->accept(this);
 403       }
 404       ir->remove();
 405       return visit_continue;
 406    }
 407
 408    handle_rvalue(&lhs);
 409    ir->lhs = lhs->as_dereference();
 410
 411    ir->lhs->accept(this);
 412
 413    handle_rvalue(&ir->rhs);
 414    ir->rhs->accept(this);
 415
 416    if (ir->condition) {
 417       handle_rvalue(&ir->condition);
 418       ir->condition->accept(this);
 419    }
 420
 421    return visit_continue;
 422 }
 423
 424 bool
 425 optimize_split_arrays(exec_list *instructions, bool linked)
 426 {
 427    ir_array_reference_visitor refs;
 428    if (!refs.get_split_list(instructions, linked))
 429       return false;
 430
 431    void *mem_ctx = ralloc_context(NULL);
 432
 433    /* Replace the decls of the arrays to be split with their split
 434     * components.
 435     */
 436    foreach_in_list(variable_entry, entry, &refs.variable_list) {
 437       const struct glsl_type *type = entry->var->type;
 438       const struct glsl_type *subtype;
 439
 440       if (type->is_matrix())
 441          subtype = type->column_type();
 442       else
 443          subtype = type->fields.array;
 444
 445       entry->mem_ctx = ralloc_parent(entry->var);
 446
 447       entry->components = ralloc_array(mem_ctx, ir_variable *, entry->size);
 448
 449       for (unsigned int i = 0; i < entry->size; i++) {
 450          const char *name = ralloc_asprintf(mem_ctx, "%s_%d",
 451                                             entry->var->name, i);
 452          ir_variable *new_var =
 453             new(entry->mem_ctx) ir_variable(subtype, name, ir_var_temporary);
 454
 455          /* Do not lose memory/format qualifiers when arrays of images are
 456           * split.
 457           */
 458          new_var->data.memory_read_only = entry->var->data.memory_read_only;
 459          new_var->data.memory_write_only = entry->var->data.memory_write_only;
 460          new_var->data.memory_coherent = entry->var->data.memory_coherent;
 461          new_var->data.memory_volatile = entry->var->data.memory_volatile;
 462          new_var->data.memory_restrict = entry->var->data.memory_restrict;
 463          new_var->data.image_format = entry->var->data.image_format;
 464
 465          entry->components[i] = new_var;
 466          entry->var->insert_before(entry->components[i]);
 467       }
 468
 469       entry->var->remove();
 470    }
 471
 472    ir_array_splitting_visitor split(&refs.variable_list);
 473    visit_list_elements(&split, instructions);
 474
 475    if (debug)
 476       _mesa_print_ir(stdout, instructions, NULL);
 477
 478    ralloc_free(mem_ctx);
 479
 480    return true;
 481
 482 }