opt_if_simplification.cpp revision 991fa4d3d07a3ebda2a1398d346b18b3afbaa736
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_if_simplification.cpp 26 * 27 * Moves constant branches of if statements out to the surrounding 28 * instruction stream. 29 */ 30 31#include "ir.h" 32 33class ir_if_simplification_visitor : public ir_hierarchical_visitor { 34public: 35 ir_if_simplification_visitor() 36 { 37 this->made_progress = false; 38 } 39 40 ir_visitor_status visit_leave(ir_if *); 41 ir_visitor_status visit_enter(ir_assignment *); 42 43 bool made_progress; 44}; 45 46/* We only care about the top level "if" instructions, so don't 47 * descend into expressions. 48 */ 49ir_visitor_status 50ir_if_simplification_visitor::visit_enter(ir_assignment *ir) 51{ 52 return visit_continue_with_parent; 53} 54 55bool 56do_if_simplification(exec_list *instructions) 57{ 58 ir_if_simplification_visitor v; 59 60 v.run(instructions); 61 return v.made_progress; 62} 63 64 65ir_visitor_status 66ir_if_simplification_visitor::visit_leave(ir_if *ir) 67{ 68 /* FINISHME: Ideally there would be a way to note that the condition results 69 * FINISHME: in a constant before processing both of the other subtrees. 70 * FINISHME: This can probably be done with some flags, but it would take 71 * FINISHME: some work to get right. 72 */ 73 ir_constant *condition_constant = ir->condition->constant_expression_value(); 74 if (condition_constant) { 75 /* Move the contents of the one branch of the conditional 76 * that matters out. 77 */ 78 if (condition_constant->value.b[0]) { 79 foreach_iter(exec_list_iterator, then_iter, ir->then_instructions) { 80 ir_instruction *then_ir = (ir_instruction *)then_iter.get(); 81 ir->insert_before(then_ir); 82 } 83 } else { 84 foreach_iter(exec_list_iterator, else_iter, ir->else_instructions) { 85 ir_instruction *else_ir = (ir_instruction *)else_iter.get(); 86 ir->insert_before(else_ir); 87 } 88 } 89 ir->remove(); 90 this->made_progress = true; 91 } 92 93 return visit_continue; 94} 95