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_copy_propagation.cpp 26 * 27 * Moves usage of recently-copied variables to the previous copy of 28 * the variable. 29 * 30 * This should reduce the number of MOV instructions in the generated 31 * programs unless copy propagation is also done on the LIR, and may 32 * help anyway by triggering other optimizations that live in the HIR. 33 */ 34 35 #include "ir.h" 36 #include "ir_visitor.h" 37 #include "ir_basic_block.h" 38 #include "ir_optimization.h" 39 #include "glsl_types.h" 40 41 namespace { 42 43 class acp_entry : public exec_node 44 { 45 public: 46 acp_entry(ir_variable *lhs, ir_variable *rhs) 47 { 48 assert(lhs); 49 assert(rhs); 50 this->lhs = lhs; 51 this->rhs = rhs; 52 } 53 54 ir_variable *lhs; 55 ir_variable *rhs; 56 }; 57 58 59 class kill_entry : public exec_node 60 { 61 public: 62 kill_entry(ir_variable *var) 63 { 64 assert(var); 65 this->var = var; 66 } 67 68 ir_variable *var; 69 }; 70 71 class ir_copy_propagation_visitor : public ir_hierarchical_visitor { 72 public: 73 ir_copy_propagation_visitor() 74 { 75 progress = false; 76 mem_ctx = ralloc_context(0); 77 this->acp = new(mem_ctx) exec_list; 78 this->kills = new(mem_ctx) exec_list; 79 } 80 ~ir_copy_propagation_visitor() 81 { 82 ralloc_free(mem_ctx); 83 } 84 85 virtual ir_visitor_status visit(class ir_dereference_variable *); 86 virtual ir_visitor_status visit_enter(class ir_loop *); 87 virtual ir_visitor_status visit_enter(class ir_function_signature *); 88 virtual ir_visitor_status visit_enter(class ir_function *); 89 virtual ir_visitor_status visit_leave(class ir_assignment *); 90 virtual ir_visitor_status visit_enter(class ir_call *); 91 virtual ir_visitor_status visit_enter(class ir_if *); 92 93 void add_copy(ir_assignment *ir); 94 void kill(ir_variable *ir); 95 void handle_if_block(exec_list *instructions); 96 97 /** List of acp_entry: The available copies to propagate */ 98 exec_list *acp; 99 /** 100 * List of kill_entry: The variables whose values were killed in this 101 * block. 102 */ 103 exec_list *kills; 104 105 bool progress; 106 107 bool killed_all; 108 109 void *mem_ctx; 110 }; 111 112 } /* unnamed namespace */ 113 114 ir_visitor_status 115 ir_copy_propagation_visitor::visit_enter(ir_function_signature *ir) 116 { 117 /* Treat entry into a function signature as a completely separate 118 * block. Any instructions at global scope will be shuffled into 119 * main() at link time, so they're irrelevant to us. 120 */ 121 exec_list *orig_acp = this->acp; 122 exec_list *orig_kills = this->kills; 123 bool orig_killed_all = this->killed_all; 124 125 this->acp = new(mem_ctx) exec_list; 126 this->kills = new(mem_ctx) exec_list; 127 this->killed_all = false; 128 129 visit_list_elements(this, &ir->body); 130 131 this->kills = orig_kills; 132 this->acp = orig_acp; 133 this->killed_all = orig_killed_all; 134 135 return visit_continue_with_parent; 136 } 137 138 ir_visitor_status 139 ir_copy_propagation_visitor::visit_leave(ir_assignment *ir) 140 { 141 kill(ir->lhs->variable_referenced()); 142 143 add_copy(ir); 144 145 return visit_continue; 146 } 147 148 ir_visitor_status 149 ir_copy_propagation_visitor::visit_enter(ir_function *ir) 150 { 151 (void) ir; 152 return visit_continue; 153 } 154 155 /** 156 * Replaces dereferences of ACP RHS variables with ACP LHS variables. 157 * 158 * This is where the actual copy propagation occurs. Note that the 159 * rewriting of ir_dereference means that the ir_dereference instance 160 * must not be shared by multiple IR operations! 161 */ 162 ir_visitor_status 163 ir_copy_propagation_visitor::visit(ir_dereference_variable *ir) 164 { 165 if (this->in_assignee) 166 return visit_continue; 167 168 ir_variable *var = ir->var; 169 170 foreach_iter(exec_list_iterator, iter, *this->acp) { 171 acp_entry *entry = (acp_entry *)iter.get(); 172 173 if (var == entry->lhs) { 174 ir->var = entry->rhs; 175 this->progress = true; 176 break; 177 } 178 } 179 180 return visit_continue; 181 } 182 183 184 ir_visitor_status 185 ir_copy_propagation_visitor::visit_enter(ir_call *ir) 186 { 187 /* Do copy propagation on call parameters, but skip any out params */ 188 exec_list_iterator sig_param_iter = ir->callee->parameters.iterator(); 189 foreach_iter(exec_list_iterator, iter, ir->actual_parameters) { 190 ir_variable *sig_param = (ir_variable *)sig_param_iter.get(); 191 ir_instruction *ir = (ir_instruction *)iter.get(); 192 if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) { 193 ir->accept(this); 194 } 195 sig_param_iter.next(); 196 } 197 198 /* Since we're unlinked, we don't (necessarily) know the side effects of 199 * this call. So kill all copies. 200 */ 201 acp->make_empty(); 202 this->killed_all = true; 203 204 return visit_continue_with_parent; 205 } 206 207 void 208 ir_copy_propagation_visitor::handle_if_block(exec_list *instructions) 209 { 210 exec_list *orig_acp = this->acp; 211 exec_list *orig_kills = this->kills; 212 bool orig_killed_all = this->killed_all; 213 214 this->acp = new(mem_ctx) exec_list; 215 this->kills = new(mem_ctx) exec_list; 216 this->killed_all = false; 217 218 /* Populate the initial acp with a copy of the original */ 219 foreach_iter(exec_list_iterator, iter, *orig_acp) { 220 acp_entry *a = (acp_entry *)iter.get(); 221 this->acp->push_tail(new(this->mem_ctx) acp_entry(a->lhs, a->rhs)); 222 } 223 224 visit_list_elements(this, instructions); 225 226 if (this->killed_all) { 227 orig_acp->make_empty(); 228 } 229 230 exec_list *new_kills = this->kills; 231 this->kills = orig_kills; 232 this->acp = orig_acp; 233 this->killed_all = this->killed_all || orig_killed_all; 234 235 foreach_iter(exec_list_iterator, iter, *new_kills) { 236 kill_entry *k = (kill_entry *)iter.get(); 237 kill(k->var); 238 } 239 } 240 241 ir_visitor_status 242 ir_copy_propagation_visitor::visit_enter(ir_if *ir) 243 { 244 ir->condition->accept(this); 245 246 handle_if_block(&ir->then_instructions); 247 handle_if_block(&ir->else_instructions); 248 249 /* handle_if_block() already descended into the children. */ 250 return visit_continue_with_parent; 251 } 252 253 ir_visitor_status 254 ir_copy_propagation_visitor::visit_enter(ir_loop *ir) 255 { 256 exec_list *orig_acp = this->acp; 257 exec_list *orig_kills = this->kills; 258 bool orig_killed_all = this->killed_all; 259 260 /* FINISHME: For now, the initial acp for loops is totally empty. 261 * We could go through once, then go through again with the acp 262 * cloned minus the killed entries after the first run through. 263 */ 264 this->acp = new(mem_ctx) exec_list; 265 this->kills = new(mem_ctx) exec_list; 266 this->killed_all = false; 267 268 visit_list_elements(this, &ir->body_instructions); 269 270 if (this->killed_all) { 271 orig_acp->make_empty(); 272 } 273 274 exec_list *new_kills = this->kills; 275 this->kills = orig_kills; 276 this->acp = orig_acp; 277 this->killed_all = this->killed_all || orig_killed_all; 278 279 foreach_iter(exec_list_iterator, iter, *new_kills) { 280 kill_entry *k = (kill_entry *)iter.get(); 281 kill(k->var); 282 } 283 284 /* already descended into the children. */ 285 return visit_continue_with_parent; 286 } 287 288 void 289 ir_copy_propagation_visitor::kill(ir_variable *var) 290 { 291 assert(var != NULL); 292 293 /* Remove any entries currently in the ACP for this kill. */ 294 foreach_iter(exec_list_iterator, iter, *acp) { 295 acp_entry *entry = (acp_entry *)iter.get(); 296 297 if (entry->lhs == var || entry->rhs == var) { 298 entry->remove(); 299 } 300 } 301 302 /* Add the LHS variable to the list of killed variables in this block. 303 */ 304 this->kills->push_tail(new(this->mem_ctx) kill_entry(var)); 305 } 306 307 /** 308 * Adds an entry to the available copy list if it's a plain assignment 309 * of a variable to a variable. 310 */ 311 void 312 ir_copy_propagation_visitor::add_copy(ir_assignment *ir) 313 { 314 acp_entry *entry; 315 316 if (ir->condition) 317 return; 318 319 ir_variable *lhs_var = ir->whole_variable_written(); 320 ir_variable *rhs_var = ir->rhs->whole_variable_referenced(); 321 322 if ((lhs_var != NULL) && (rhs_var != NULL)) { 323 if (lhs_var == rhs_var) { 324 /* This is a dumb assignment, but we've conveniently noticed 325 * it here. Removing it now would mess up the loop iteration 326 * calling us. Just flag it to not execute, and someone else 327 * will clean up the mess. 328 */ 329 ir->condition = new(ralloc_parent(ir)) ir_constant(false); 330 this->progress = true; 331 } else { 332 entry = new(this->mem_ctx) acp_entry(lhs_var, rhs_var); 333 this->acp->push_tail(entry); 334 } 335 } 336 } 337 338 /** 339 * Does a copy propagation pass on the code present in the instruction stream. 340 */ 341 bool 342 do_copy_propagation(exec_list *instructions) 343 { 344 ir_copy_propagation_visitor v; 345 346 visit_list_elements(&v, instructions); 347 348 return v.progress; 349 } 350
