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