1 /* 2 * Copyright 2010 Intel Corporation 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining a 5 * constant 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, constant, 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 constantright 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 CONSTANTRIGHT 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_constant_propagation.cpp 26 * 27 * Tracks assignments of constants to channels of variables, and 28 * usage of those constant channels with direct usage of the constants. 29 * 30 * This can lead to constant folding and algebraic optimizations in 31 * those later expressions, while causing no increase in instruction 32 * count (due to constants being generally free to load from a 33 * constant push buffer or as instruction immediate values) and 34 * possibly reducing register pressure. 35 */ 36 37 #include "ir.h" 38 #include "ir_visitor.h" 39 #include "ir_rvalue_visitor.h" 40 #include "ir_basic_block.h" 41 #include "ir_optimization.h" 42 #include "glsl_types.h" 43 44 class acp_entry : public exec_node 45 { 46 public: 47 acp_entry(ir_variable *var, unsigned write_mask, ir_constant *constant) 48 { 49 assert(var); 50 assert(constant); 51 this->var = var; 52 this->write_mask = write_mask; 53 this->constant = constant; 54 } 55 56 ir_variable *var; 57 ir_constant *constant; 58 unsigned write_mask; 59 }; 60 61 62 class kill_entry : public exec_node 63 { 64 public: 65 kill_entry(ir_variable *var, unsigned write_mask) 66 { 67 assert(var); 68 this->var = var; 69 this->write_mask = write_mask; 70 } 71 72 ir_variable *var; 73 unsigned write_mask; 74 }; 75 76 class ir_constant_propagation_visitor : public ir_rvalue_visitor { 77 public: 78 ir_constant_propagation_visitor() 79 { 80 progress = false; 81 mem_ctx = hieralloc_new(0); 82 this->acp = new(mem_ctx) exec_list; 83 this->kills = new(mem_ctx) exec_list; 84 } 85 ~ir_constant_propagation_visitor() 86 { 87 hieralloc_free(mem_ctx); 88 } 89 90 virtual ir_visitor_status visit_enter(class ir_loop *); 91 virtual ir_visitor_status visit_enter(class ir_function_signature *); 92 virtual ir_visitor_status visit_enter(class ir_function *); 93 virtual ir_visitor_status visit_leave(class ir_assignment *); 94 virtual ir_visitor_status visit_enter(class ir_call *); 95 virtual ir_visitor_status visit_enter(class ir_if *); 96 97 void add_constant(ir_assignment *ir); 98 void kill(ir_variable *ir, unsigned write_mask); 99 void handle_if_block(exec_list *instructions); 100 void handle_rvalue(ir_rvalue **rvalue); 101 102 /** List of acp_entry: The available constants to propagate */ 103 exec_list *acp; 104 105 /** 106 * List of kill_entry: The masks of variables whose values were 107 * killed in this block. 108 */ 109 exec_list *kills; 110 111 bool progress; 112 113 bool killed_all; 114 115 void *mem_ctx; 116 }; 117 118 119 void 120 ir_constant_propagation_visitor::handle_rvalue(ir_rvalue **rvalue) 121 { 122 if (this->in_assignee || !*rvalue) 123 return; 124 125 const glsl_type *type = (*rvalue)->type; 126 if (!type->is_scalar() && !type->is_vector()) 127 return; 128 129 ir_swizzle *swiz = NULL; 130 ir_dereference_variable *deref = (*rvalue)->as_dereference_variable(); 131 if (!deref) { 132 swiz = (*rvalue)->as_swizzle(); 133 if (!swiz) 134 return; 135 136 deref = swiz->val->as_dereference_variable(); 137 if (!deref) 138 return; 139 } 140 141 ir_constant_data data; 142 memset(&data, 0, sizeof(data)); 143 144 for (unsigned int i = 0; i < type->components(); i++) { 145 int channel; 146 acp_entry *found = NULL; 147 148 if (swiz) { 149 switch (i) { 150 case 0: channel = swiz->mask.x; break; 151 case 1: channel = swiz->mask.y; break; 152 case 2: channel = swiz->mask.z; break; 153 case 3: channel = swiz->mask.w; break; 154 default: assert(!"shouldn't be reached"); channel = 0; break; 155 } 156 } else { 157 channel = i; 158 } 159 160 foreach_iter(exec_list_iterator, iter, *this->acp) { 161 acp_entry *entry = (acp_entry *)iter.get(); 162 if (entry->var == deref->var && entry->write_mask & (1 << channel)) { 163 found = entry; 164 break; 165 } 166 } 167 168 if (!found) 169 return; 170 171 int rhs_channel = 0; 172 for (int j = 0; j < 4; j++) { 173 if (j == channel) 174 break; 175 if (found->write_mask & (1 << j)) 176 rhs_channel++; 177 } 178 179 switch (type->base_type) { 180 case GLSL_TYPE_FLOAT: 181 data.f[i] = found->constant->value.f[rhs_channel]; 182 break; 183 case GLSL_TYPE_INT: 184 data.i[i] = found->constant->value.i[rhs_channel]; 185 break; 186 case GLSL_TYPE_UINT: 187 data.u[i] = found->constant->value.u[rhs_channel]; 188 break; 189 case GLSL_TYPE_BOOL: 190 data.b[i] = found->constant->value.b[rhs_channel]; 191 break; 192 default: 193 assert(!"not reached"); 194 break; 195 } 196 } 197 198 *rvalue = new(hieralloc_parent(deref)) ir_constant(type, &data); 199 this->progress = true; 200 } 201 202 ir_visitor_status 203 ir_constant_propagation_visitor::visit_enter(ir_function_signature *ir) 204 { 205 /* Treat entry into a function signature as a completely separate 206 * block. Any instructions at global scope will be shuffled into 207 * main() at link time, so they're irrelevant to us. 208 */ 209 exec_list *orig_acp = this->acp; 210 exec_list *orig_kills = this->kills; 211 bool orig_killed_all = this->killed_all; 212 213 this->acp = new(mem_ctx) exec_list; 214 this->kills = new(mem_ctx) exec_list; 215 this->killed_all = false; 216 217 visit_list_elements(this, &ir->body); 218 219 this->kills = orig_kills; 220 this->acp = orig_acp; 221 this->killed_all = orig_killed_all; 222 223 return visit_continue_with_parent; 224 } 225 226 ir_visitor_status 227 ir_constant_propagation_visitor::visit_leave(ir_assignment *ir) 228 { 229 if (this->in_assignee) 230 return visit_continue; 231 232 kill(ir->lhs->variable_referenced(), ir->write_mask); 233 234 add_constant(ir); 235 236 return visit_continue; 237 } 238 239 ir_visitor_status 240 ir_constant_propagation_visitor::visit_enter(ir_function *ir) 241 { 242 (void) ir; 243 return visit_continue; 244 } 245 246 ir_visitor_status 247 ir_constant_propagation_visitor::visit_enter(ir_call *ir) 248 { 249 /* Do constant propagation on call parameters, but skip any out params */ 250 exec_list_iterator sig_param_iter = ir->get_callee()->parameters.iterator(); 251 foreach_iter(exec_list_iterator, iter, ir->actual_parameters) { 252 ir_variable *sig_param = (ir_variable *)sig_param_iter.get(); 253 ir_rvalue *param = (ir_rvalue *)iter.get(); 254 if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) { 255 ir_rvalue *new_param = param; 256 handle_rvalue(&new_param); 257 if (new_param != param) 258 param->replace_with(new_param); 259 else 260 param->accept(this); 261 } 262 sig_param_iter.next(); 263 } 264 265 /* Since we're unlinked, we don't (necssarily) know the side effects of 266 * this call. So kill all copies. 267 */ 268 acp->make_empty(); 269 this->killed_all = true; 270 271 return visit_continue_with_parent; 272 } 273 274 void 275 ir_constant_propagation_visitor::handle_if_block(exec_list *instructions) 276 { 277 exec_list *orig_acp = this->acp; 278 exec_list *orig_kills = this->kills; 279 bool orig_killed_all = this->killed_all; 280 281 this->acp = new(mem_ctx) exec_list; 282 this->kills = new(mem_ctx) exec_list; 283 this->killed_all = false; 284 285 /* Populate the initial acp with a constant of the original */ 286 foreach_iter(exec_list_iterator, iter, *orig_acp) { 287 acp_entry *a = (acp_entry *)iter.get(); 288 this->acp->push_tail(new(this->mem_ctx) acp_entry(a->var, a->write_mask, 289 a->constant)); 290 } 291 292 visit_list_elements(this, instructions); 293 294 if (this->killed_all) { 295 orig_acp->make_empty(); 296 } 297 298 exec_list *new_kills = this->kills; 299 this->kills = orig_kills; 300 this->acp = orig_acp; 301 this->killed_all = this->killed_all || orig_killed_all; 302 303 foreach_iter(exec_list_iterator, iter, *new_kills) { 304 kill_entry *k = (kill_entry *)iter.get(); 305 kill(k->var, k->write_mask); 306 } 307 } 308 309 ir_visitor_status 310 ir_constant_propagation_visitor::visit_enter(ir_if *ir) 311 { 312 ir->condition->accept(this); 313 handle_rvalue(&ir->condition); 314 315 handle_if_block(&ir->then_instructions); 316 handle_if_block(&ir->else_instructions); 317 318 /* handle_if_block() already descended into the children. */ 319 return visit_continue_with_parent; 320 } 321 322 ir_visitor_status 323 ir_constant_propagation_visitor::visit_enter(ir_loop *ir) 324 { 325 exec_list *orig_acp = this->acp; 326 exec_list *orig_kills = this->kills; 327 bool orig_killed_all = this->killed_all; 328 329 /* FINISHME: For now, the initial acp for loops is totally empty. 330 * We could go through once, then go through again with the acp 331 * cloned minus the killed entries after the first run through. 332 */ 333 this->acp = new(mem_ctx) exec_list; 334 this->kills = new(mem_ctx) exec_list; 335 this->killed_all = false; 336 337 visit_list_elements(this, &ir->body_instructions); 338 339 if (this->killed_all) { 340 orig_acp->make_empty(); 341 } 342 343 exec_list *new_kills = this->kills; 344 this->kills = orig_kills; 345 this->acp = orig_acp; 346 this->killed_all = this->killed_all || orig_killed_all; 347 348 foreach_iter(exec_list_iterator, iter, *new_kills) { 349 kill_entry *k = (kill_entry *)iter.get(); 350 kill(k->var, k->write_mask); 351 } 352 353 /* already descended into the children. */ 354 return visit_continue_with_parent; 355 } 356 357 void 358 ir_constant_propagation_visitor::kill(ir_variable *var, unsigned write_mask) 359 { 360 assert(var != NULL); 361 362 /* We don't track non-vectors. */ 363 if (!var->type->is_vector() && !var->type->is_scalar()) 364 return; 365 366 /* Remove any entries currently in the ACP for this kill. */ 367 foreach_iter(exec_list_iterator, iter, *this->acp) { 368 acp_entry *entry = (acp_entry *)iter.get(); 369 370 if (entry->var == var) { 371 entry->write_mask &= ~write_mask; 372 if (entry->write_mask == 0) 373 entry->remove(); 374 } 375 } 376 377 /* Add this writemask of the variable to the list of killed 378 * variables in this block. 379 */ 380 foreach_iter(exec_list_iterator, iter, *this->kills) { 381 kill_entry *entry = (kill_entry *)iter.get(); 382 383 if (entry->var == var) { 384 entry->write_mask |= write_mask; 385 return; 386 } 387 } 388 /* Not already in the list. Make new entry. */ 389 this->kills->push_tail(new(this->mem_ctx) kill_entry(var, write_mask)); 390 } 391 392 /** 393 * Adds an entry to the available constant list if it's a plain assignment 394 * of a variable to a variable. 395 */ 396 void 397 ir_constant_propagation_visitor::add_constant(ir_assignment *ir) 398 { 399 acp_entry *entry; 400 401 if (ir->condition) { 402 ir_constant *condition = ir->condition->as_constant(); 403 if (!condition || !condition->value.b[0]) 404 return; 405 } 406 407 if (!ir->write_mask) 408 return; 409 410 ir_dereference_variable *deref = ir->lhs->as_dereference_variable(); 411 ir_constant *constant = ir->rhs->as_constant(); 412 413 if (!deref || !constant) 414 return; 415 416 /* Only do constant propagation on vectors. Constant matrices, 417 * arrays, or structures would require more work elsewhere. 418 */ 419 if (!deref->var->type->is_vector() && !deref->var->type->is_scalar()) 420 return; 421 422 entry = new(this->mem_ctx) acp_entry(deref->var, ir->write_mask, constant); 423 this->acp->push_tail(entry); 424 } 425 426 /** 427 * Does a constant propagation pass on the code present in the instruction stream. 428 */ 429 bool 430 do_constant_propagation(exec_list *instructions) 431 { 432 ir_constant_propagation_visitor v; 433 434 visit_list_elements(&v, instructions); 435 436 return v.progress; 437 } 438