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_tree_grafting.cpp 26 * 27 * Takes assignments to variables that are dereferenced only once and 28 * pastes the RHS expression into where the variable is dereferenced. 29 * 30 * In the process of various operations like function inlining and 31 * tertiary op handling, we'll end up with our expression trees having 32 * been chopped up into a series of assignments of short expressions 33 * to temps. Other passes like ir_algebraic.cpp would prefer to see 34 * the deepest expression trees they can to try to optimize them. 35 * 36 * This is a lot like copy propagaton. In comparison, copy 37 * propagation only acts on plain copies, not arbitrary expressions on 38 * the RHS. Generally, we wouldn't want to go pasting some 39 * complicated expression everywhere it got used, though, so we don't 40 * handle expressions in that pass. 41 * 42 * The hard part is making sure we don't move an expression across 43 * some other assignments that would change the value of the 44 * expression. So we split this into two passes: First, find the 45 * variables in our scope which are written to once and read once, and 46 * then go through basic blocks seeing if we find an opportunity to 47 * move those expressions safely. 48 */ 49 50 #include "ir.h" 51 #include "ir_visitor.h" 52 #include "ir_variable_refcount.h" 53 #include "ir_basic_block.h" 54 #include "ir_optimization.h" 55 #include "glsl_types.h" 56 57 namespace { 58 59 static bool debug = false; 60 61 class ir_tree_grafting_visitor : public ir_hierarchical_visitor { 62 public: 63 ir_tree_grafting_visitor(ir_assignment *graft_assign, 64 ir_variable *graft_var) 65 { 66 this->progress = false; 67 this->graft_assign = graft_assign; 68 this->graft_var = graft_var; 69 } 70 71 virtual ir_visitor_status visit_leave(class ir_assignment *); 72 virtual ir_visitor_status visit_enter(class ir_call *); 73 virtual ir_visitor_status visit_enter(class ir_expression *); 74 virtual ir_visitor_status visit_enter(class ir_function *); 75 virtual ir_visitor_status visit_enter(class ir_function_signature *); 76 virtual ir_visitor_status visit_enter(class ir_if *); 77 virtual ir_visitor_status visit_enter(class ir_loop *); 78 virtual ir_visitor_status visit_enter(class ir_swizzle *); 79 virtual ir_visitor_status visit_enter(class ir_texture *); 80 81 ir_visitor_status check_graft(ir_instruction *ir, ir_variable *var); 82 83 bool do_graft(ir_rvalue **rvalue); 84 85 bool progress; 86 ir_variable *graft_var; 87 ir_assignment *graft_assign; 88 }; 89 90 struct find_deref_info { 91 ir_variable *var; 92 bool found; 93 }; 94 95 void 96 dereferences_variable_callback(ir_instruction *ir, void *data) 97 { 98 struct find_deref_info *info = (struct find_deref_info *)data; 99 ir_dereference_variable *deref = ir->as_dereference_variable(); 100 101 if (deref && deref->var == info->var) 102 info->found = true; 103 } 104 105 static bool 106 dereferences_variable(ir_instruction *ir, ir_variable *var) 107 { 108 struct find_deref_info info; 109 110 info.var = var; 111 info.found = false; 112 113 visit_tree(ir, dereferences_variable_callback, &info); 114 115 return info.found; 116 } 117 118 bool 119 ir_tree_grafting_visitor::do_graft(ir_rvalue **rvalue) 120 { 121 if (!*rvalue) 122 return false; 123 124 ir_dereference_variable *deref = (*rvalue)->as_dereference_variable(); 125 126 if (!deref || deref->var != this->graft_var) 127 return false; 128 129 if (debug) { 130 printf("GRAFTING:\n"); 131 this->graft_assign->print(); 132 printf("\n"); 133 printf("TO:\n"); 134 (*rvalue)->print(); 135 printf("\n"); 136 } 137 138 this->graft_assign->remove(); 139 *rvalue = this->graft_assign->rhs; 140 141 this->progress = true; 142 return true; 143 } 144 145 ir_visitor_status 146 ir_tree_grafting_visitor::visit_enter(ir_loop *ir) 147 { 148 (void)ir; 149 /* Do not traverse into the body of the loop since that is a 150 * different basic block. 151 */ 152 return visit_stop; 153 } 154 155 /** 156 * Check if we can continue grafting after writing to a variable. If the 157 * expression we're trying to graft references the variable, we must stop. 158 * 159 * \param ir An instruction that writes to a variable. 160 * \param var The variable being updated. 161 */ 162 ir_visitor_status 163 ir_tree_grafting_visitor::check_graft(ir_instruction *ir, ir_variable *var) 164 { 165 if (dereferences_variable(this->graft_assign->rhs, var)) { 166 if (debug) { 167 printf("graft killed by: "); 168 ir->print(); 169 printf("\n"); 170 } 171 return visit_stop; 172 } 173 174 return visit_continue; 175 } 176 177 ir_visitor_status 178 ir_tree_grafting_visitor::visit_leave(ir_assignment *ir) 179 { 180 if (do_graft(&ir->rhs) || 181 do_graft(&ir->condition)) 182 return visit_stop; 183 184 /* If this assignment updates a variable used in the assignment 185 * we're trying to graft, then we're done. 186 */ 187 return check_graft(ir, ir->lhs->variable_referenced()); 188 } 189 190 ir_visitor_status 191 ir_tree_grafting_visitor::visit_enter(ir_function *ir) 192 { 193 (void) ir; 194 return visit_continue_with_parent; 195 } 196 197 ir_visitor_status 198 ir_tree_grafting_visitor::visit_enter(ir_function_signature *ir) 199 { 200 (void)ir; 201 return visit_continue_with_parent; 202 } 203 204 ir_visitor_status 205 ir_tree_grafting_visitor::visit_enter(ir_call *ir) 206 { 207 exec_list_iterator sig_iter = ir->callee->parameters.iterator(); 208 /* Reminder: iterating ir_call iterates its parameters. */ 209 foreach_iter(exec_list_iterator, iter, *ir) { 210 ir_variable *sig_param = (ir_variable *)sig_iter.get(); 211 ir_rvalue *ir = (ir_rvalue *)iter.get(); 212 ir_rvalue *new_ir = ir; 213 214 if (sig_param->mode != ir_var_in && sig_param->mode != ir_var_const_in) { 215 if (check_graft(ir, sig_param) == visit_stop) 216 return visit_stop; 217 continue; 218 } 219 220 if (do_graft(&new_ir)) { 221 ir->replace_with(new_ir); 222 return visit_stop; 223 } 224 sig_iter.next(); 225 } 226 227 if (ir->return_deref && check_graft(ir, ir->return_deref->var) == visit_stop) 228 return visit_stop; 229 230 return visit_continue; 231 } 232 233 ir_visitor_status 234 ir_tree_grafting_visitor::visit_enter(ir_expression *ir) 235 { 236 for (unsigned int i = 0; i < ir->get_num_operands(); i++) { 237 if (do_graft(&ir->operands[i])) 238 return visit_stop; 239 } 240 241 return visit_continue; 242 } 243 244 ir_visitor_status 245 ir_tree_grafting_visitor::visit_enter(ir_if *ir) 246 { 247 if (do_graft(&ir->condition)) 248 return visit_stop; 249 250 /* Do not traverse into the body of the if-statement since that is a 251 * different basic block. 252 */ 253 return visit_continue_with_parent; 254 } 255 256 ir_visitor_status 257 ir_tree_grafting_visitor::visit_enter(ir_swizzle *ir) 258 { 259 if (do_graft(&ir->val)) 260 return visit_stop; 261 262 return visit_continue; 263 } 264 265 ir_visitor_status 266 ir_tree_grafting_visitor::visit_enter(ir_texture *ir) 267 { 268 if (do_graft(&ir->coordinate) || 269 do_graft(&ir->projector) || 270 do_graft(&ir->offset) || 271 do_graft(&ir->shadow_comparitor)) 272 return visit_stop; 273 274 switch (ir->op) { 275 case ir_tex: 276 break; 277 case ir_txb: 278 if (do_graft(&ir->lod_info.bias)) 279 return visit_stop; 280 break; 281 case ir_txf: 282 case ir_txl: 283 case ir_txs: 284 if (do_graft(&ir->lod_info.lod)) 285 return visit_stop; 286 break; 287 case ir_txd: 288 if (do_graft(&ir->lod_info.grad.dPdx) || 289 do_graft(&ir->lod_info.grad.dPdy)) 290 return visit_stop; 291 break; 292 } 293 294 return visit_continue; 295 } 296 297 struct tree_grafting_info { 298 ir_variable_refcount_visitor *refs; 299 bool progress; 300 }; 301 302 static bool 303 try_tree_grafting(ir_assignment *start, 304 ir_variable *lhs_var, 305 ir_instruction *bb_last) 306 { 307 ir_tree_grafting_visitor v(start, lhs_var); 308 309 if (debug) { 310 printf("trying to graft: "); 311 lhs_var->print(); 312 printf("\n"); 313 } 314 315 for (ir_instruction *ir = (ir_instruction *)start->next; 316 ir != bb_last->next; 317 ir = (ir_instruction *)ir->next) { 318 319 if (debug) { 320 printf("- "); 321 ir->print(); 322 printf("\n"); 323 } 324 325 ir_visitor_status s = ir->accept(&v); 326 if (s == visit_stop) 327 return v.progress; 328 } 329 330 return false; 331 } 332 333 static void 334 tree_grafting_basic_block(ir_instruction *bb_first, 335 ir_instruction *bb_last, 336 void *data) 337 { 338 struct tree_grafting_info *info = (struct tree_grafting_info *)data; 339 ir_instruction *ir, *next; 340 341 for (ir = bb_first, next = (ir_instruction *)ir->next; 342 ir != bb_last->next; 343 ir = next, next = (ir_instruction *)ir->next) { 344 ir_assignment *assign = ir->as_assignment(); 345 346 if (!assign) 347 continue; 348 349 ir_variable *lhs_var = assign->whole_variable_written(); 350 if (!lhs_var) 351 continue; 352 353 if (lhs_var->mode == ir_var_out || 354 lhs_var->mode == ir_var_inout) 355 continue; 356 357 ir_variable_refcount_entry *entry = info->refs->get_variable_entry(lhs_var); 358 359 if (!entry->declaration || 360 entry->assigned_count != 1 || 361 entry->referenced_count != 2) 362 continue; 363 364 assert(assign == entry->assign); 365 366 /* Found a possibly graftable assignment. Now, walk through the 367 * rest of the BB seeing if the deref is here, and if nothing interfered with 368 * pasting its expression's values in between. 369 */ 370 info->progress |= try_tree_grafting(assign, lhs_var, bb_last); 371 } 372 } 373 374 } /* unnamed namespace */ 375 376 /** 377 * Does a copy propagation pass on the code present in the instruction stream. 378 */ 379 bool 380 do_tree_grafting(exec_list *instructions) 381 { 382 ir_variable_refcount_visitor refs; 383 struct tree_grafting_info info; 384 385 info.progress = false; 386 info.refs = &refs; 387 388 visit_list_elements(info.refs, instructions); 389 390 call_for_basic_blocks(instructions, tree_grafting_basic_block, &info); 391 392 return info.progress; 393 } 394
