src/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 "ir_print_visitor.h"
  40 #include "glsl_types.h"
  41
  42 static bool debug = false;
  43
  44 namespace opt_array_splitting {
  45
  46 class variable_entry : public exec_node
  47 {
  48 public:
  49    variable_entry(ir_variable *var)
  50    {
  51       this->var = var;
  52       this->split = true;
  53       this->declaration = false;
  54       this->components = NULL;
  55       this->mem_ctx = NULL;
  56       if (var->type->is_array())
  57          this->size = var->type->length;
  58       else
  59          this->size = var->type->matrix_columns;
  60    }
  61
  62    ir_variable *var; /* The key: the variable's pointer. */
  63    unsigned size; /* array length or matrix columns */
  64
  65    /** Whether this array should be split or not. */
  66    bool split;
  67
  68    /* If the variable had a decl we can work with in the instruction
  69     * stream.  We can't do splitting on function arguments, which
  70     * don't get this variable set.
  71     */
  72    bool declaration;
  73
  74    ir_variable **components;
  75
  76    /** ralloc_parent(this->var) -- the shader's talloc context. */
  77    void *mem_ctx;
  78 };
  79
  80 } /* namespace */
  81 using namespace opt_array_splitting;
  82
  83 /**
  84  * This class does a walk over the tree, coming up with the set of
  85  * variables that could be split by looking to see if they are arrays
  86  * that are only ever constant-index dereferenced.
  87  */
  88 class ir_array_reference_visitor : public ir_hierarchical_visitor {
  89 public:
  90    ir_array_reference_visitor(void)
  91    {
  92       this->mem_ctx = ralloc_context(NULL);
  93       this->variable_list.make_empty();
  94    }
  95
  96    ~ir_array_reference_visitor(void)
  97    {
  98       ralloc_free(mem_ctx);
  99    }
 100
 101    bool get_split_list(exec_list *instructions, bool linked);
 102
 103    virtual ir_visitor_status visit(ir_variable *);
 104    virtual ir_visitor_status visit(ir_dereference_variable *);
 105    virtual ir_visitor_status visit_enter(ir_dereference_array *);
 106    virtual ir_visitor_status visit_enter(ir_function_signature *);
 107
 108    variable_entry *get_variable_entry(ir_variable *var);
 109
 110    /* List of variable_entry */
 111    exec_list variable_list;
 112
 113    void *mem_ctx;
 114 };
 115
 116 variable_entry *
 117 ir_array_reference_visitor::get_variable_entry(ir_variable *var)
 118 {
 119    assert(var);
 120
 121    if (var->mode != ir_var_auto &&
 122        var->mode != ir_var_temporary)
 123       return NULL;
 124
 125    if (!(var->type->is_array() || var->type->is_matrix()))
 126       return NULL;
 127
 128    /* If the array hasn't been sized yet, we can't split it.  After
 129     * linking, this should be resolved.
 130     */
 131    if (var->type->is_array() && var->type->length == 0)
 132       return NULL;
 133
 134    foreach_iter(exec_list_iterator, iter, this->variable_list) {
 135       variable_entry *entry = (variable_entry *)iter.get();
 136       if (entry->var == var)
 137          return entry;
 138    }
 139
 140    variable_entry *entry = new(mem_ctx) variable_entry(var);
 141    this->variable_list.push_tail(entry);
 142    return entry;
 143 }
 144
 145
 146 ir_visitor_status
 147 ir_array_reference_visitor::visit(ir_variable *ir)
 148 {
 149    variable_entry *entry = this->get_variable_entry(ir);
 150
 151    if (entry)
 152       entry->declaration = true;
 153
 154    return visit_continue;
 155 }
 156
 157 ir_visitor_status
 158 ir_array_reference_visitor::visit(ir_dereference_variable *ir)
 159 {
 160    variable_entry *entry = this->get_variable_entry(ir->var);
 161
 162    /* If we made it to here without seeing an ir_dereference_array,
 163     * then the dereference of this array didn't have a constant index
 164     * (see the visit_continue_with_parent below), so we can't split
 165     * the variable.
 166     */
 167    if (entry)
 168       entry->split = false;
 169
 170    return visit_continue;
 171 }
 172
 173 ir_visitor_status
 174 ir_array_reference_visitor::visit_enter(ir_dereference_array *ir)
 175 {
 176    ir_dereference_variable *deref = ir->array->as_dereference_variable();
 177    if (!deref)
 178       return visit_continue;
 179
 180    variable_entry *entry = this->get_variable_entry(deref->var);
 181
 182    /* If the access to the array has a variable index, we wouldn't
 183     * know which split variable this dereference should go to.
 184     */
 185    if (entry && !ir->array_index->as_constant())
 186       entry->split = false;
 187
 188    return visit_continue_with_parent;
 189 }
 190
 191 ir_visitor_status
 192 ir_array_reference_visitor::visit_enter(ir_function_signature *ir)
 193 {
 194    /* We don't have logic for array-splitting function arguments,
 195     * so just look at the body instructions and not the parameter
 196     * declarations.
 197     */
 198    visit_list_elements(this, &ir->body);
 199    return visit_continue_with_parent;
 200 }
 201
 202 bool
 203 ir_array_reference_visitor::get_split_list(exec_list *instructions,
 204                                            bool linked)
 205 {
 206    visit_list_elements(this, instructions);
 207
 208    /* If the shaders aren't linked yet, we can't mess with global
 209     * declarations, which need to be matched by name across shaders.
 210     */
 211    if (!linked) {
 212       foreach_list(node, instructions) {
 213          ir_variable *var = ((ir_instruction *)node)->as_variable();
 214          if (var) {
 215             variable_entry *entry = get_variable_entry(var);
 216             if (entry)
 217                entry->remove();
 218          }
 219       }
 220    }
 221
 222    /* Trim out variables we found that we can't split. */
 223    foreach_iter(exec_list_iterator, iter, variable_list) {
 224       variable_entry *entry = (variable_entry *)iter.get();
 225
 226       if (debug) {
 227          printf("array %s@%p: decl %d, split %d\n",
 228                 entry->var->name, (void *) entry->var, entry->declaration,
 229                 entry->split);
 230       }
 231
 232       if (!(entry->declaration && entry->split)) {
 233          entry->remove();
 234       }
 235    }
 236
 237    return !variable_list.is_empty();
 238 }
 239
 240 /**
 241  * This class rewrites the dereferences of arrays that have been split
 242  * to use the newly created ir_variables for each component.
 243  */
 244 class ir_array_splitting_visitor : public ir_rvalue_visitor {
 245 public:
 246    ir_array_splitting_visitor(exec_list *vars)
 247    {
 248       this->variable_list = vars;
 249    }
 250
 251    virtual ~ir_array_splitting_visitor()
 252    {
 253    }
 254
 255    virtual ir_visitor_status visit_leave(ir_assignment *);
 256
 257    void split_deref(ir_dereference **deref);
 258    void handle_rvalue(ir_rvalue **rvalue);
 259    variable_entry *get_splitting_entry(ir_variable *var);
 260
 261    exec_list *variable_list;
 262 };
 263
 264 variable_entry *
 265 ir_array_splitting_visitor::get_splitting_entry(ir_variable *var)
 266 {
 267    assert(var);
 268
 269    foreach_iter(exec_list_iterator, iter, *this->variable_list) {
 270       variable_entry *entry = (variable_entry *)iter.get();
 271       if (entry->var == var) {
 272          return entry;
 273       }
 274    }
 275
 276    return NULL;
 277 }
 278
 279 void
 280 ir_array_splitting_visitor::split_deref(ir_dereference **deref)
 281 {
 282    ir_dereference_array *deref_array = (*deref)->as_dereference_array();
 283    if (!deref_array)
 284       return;
 285
 286    ir_dereference_variable *deref_var = deref_array->array->as_dereference_variable();
 287    if (!deref_var)
 288       return;
 289    ir_variable *var = deref_var->var;
 290
 291    variable_entry *entry = get_splitting_entry(var);
 292    if (!entry)
 293       return;
 294
 295    ir_constant *constant = deref_array->array_index->as_constant();
 296    assert(constant);
 297
 298    if (constant->value.i[0] < (int)entry->size) {
 299       *deref = new(entry->mem_ctx)
 300          ir_dereference_variable(entry->components[constant->value.i[0]]);
 301    } else {
 302       /* There was a constant array access beyond the end of the
 303        * array.  This might have happened due to constant folding
 304        * after the initial parse.  This produces an undefined value,
 305        * but shouldn't crash.  Just give them an uninitialized
 306        * variable.
 307        */
 308       ir_variable *temp = new(entry->mem_ctx) ir_variable(deref_array->type,
 309                                                           "undef",
 310                                                           ir_var_temporary);
 311       entry->components[0]->insert_before(temp);
 312       *deref = new(entry->mem_ctx) ir_dereference_variable(temp);
 313    }
 314 }
 315
 316 void
 317 ir_array_splitting_visitor::handle_rvalue(ir_rvalue **rvalue)
 318 {
 319    if (!*rvalue)
 320       return;
 321
 322    ir_dereference *deref = (*rvalue)->as_dereference();
 323
 324    if (!deref)
 325       return;
 326
 327    split_deref(&deref);
 328    *rvalue = deref;
 329 }
 330
 331 ir_visitor_status
 332 ir_array_splitting_visitor::visit_leave(ir_assignment *ir)
 333 {
 334    /* The normal rvalue visitor skips the LHS of assignments, but we
 335     * need to process those just the same.
 336     */
 337    ir_rvalue *lhs = ir->lhs;
 338
 339    handle_rvalue(&lhs);
 340    ir->lhs = lhs->as_dereference();
 341
 342    ir->lhs->accept(this);
 343
 344    handle_rvalue(&ir->rhs);
 345    ir->rhs->accept(this);
 346
 347    if (ir->condition) {
 348       handle_rvalue(&ir->condition);
 349       ir->condition->accept(this);
 350    }
 351
 352    return visit_continue;
 353 }
 354
 355 bool
 356 optimize_split_arrays(exec_list *instructions, bool linked)
 357 {
 358    ir_array_reference_visitor refs;
 359    if (!refs.get_split_list(instructions, linked))
 360       return false;
 361
 362    void *mem_ctx = ralloc_context(NULL);
 363
 364    /* Replace the decls of the arrays to be split with their split
 365     * components.
 366     */
 367    foreach_iter(exec_list_iterator, iter, refs.variable_list) {
 368       variable_entry *entry = (variable_entry *)iter.get();
 369       const struct glsl_type *type = entry->var->type;
 370       const struct glsl_type *subtype;
 371
 372       if (type->is_matrix())
 373          subtype = type->column_type();
 374       else
 375          subtype = type->fields.array;
 376
 377       entry->mem_ctx = ralloc_parent(entry->var);
 378
 379       entry->components = ralloc_array(mem_ctx,
 380                                        ir_variable *,
 381                                        entry->size);
 382
 383       for (unsigned int i = 0; i < entry->size; i++) {
 384          const char *name = ralloc_asprintf(mem_ctx, "%s_%d",
 385                                             entry->var->name, i);
 386
 387          entry->components[i] =
 388             new(entry->mem_ctx) ir_variable(subtype, name, ir_var_temporary);
 389          entry->var->insert_before(entry->components[i]);
 390       }
 391
 392       entry->var->remove();
 393    }
 394
 395    ir_array_splitting_visitor split(&refs.variable_list);
 396    visit_list_elements(&split, instructions);
 397
 398    if (debug)
 399       _mesa_print_ir(instructions, NULL);
 400
 401    ralloc_free(mem_ctx);
 402
 403    return true;
 404
 405 }