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_dead_code.cpp 26 * 27 * Eliminates dead assignments and variable declarations from the code. 28 */ 29 30 #include "ir.h" 31 #include "ir_visitor.h" 32 #include "ir_variable_refcount.h" 33 #include "glsl_types.h" 34 35 static bool debug = false; 36 37 /** 38 * Do a dead code pass over instructions and everything that instructions 39 * references. 40 * 41 * Note that this will remove assignments to globals, so it is not suitable 42 * for usage on an unlinked instruction stream. 43 */ 44 bool 45 do_dead_code(exec_list *instructions) 46 { 47 ir_variable_refcount_visitor v; 48 bool progress = false; 49 50 v.run(instructions); 51 52 foreach_iter(exec_list_iterator, iter, v.variable_list) { 53 variable_entry *entry = (variable_entry *)iter.get(); 54 55 /* Since each assignment is a reference, the refereneced count must be 56 * greater than or equal to the assignment count. If they are equal, 57 * then all of the references are assignments, and the variable is 58 * dead. 59 * 60 * Note that if the variable is neither assigned nor referenced, both 61 * counts will be zero and will be caught by the equality test. 62 */ 63 assert(entry->referenced_count >= entry->assigned_count); 64 65 if (debug) { 66 printf("%s@%p: %d refs, %d assigns, %sdeclared in our scope\n", 67 entry->var->name, (void *) entry->var, 68 entry->referenced_count, entry->assigned_count, 69 entry->declaration ? "" : "not "); 70 } 71 72 if ((entry->referenced_count > entry->assigned_count) 73 || !entry->declaration) 74 continue; 75 76 if (entry->assign) { 77 /* Remove a single dead assignment to the variable we found. 78 * Don't do so if it's a shader output, though. 79 */ 80 if (entry->var->mode != ir_var_out && 81 entry->var->mode != ir_var_inout && 82 !ir_has_call(entry->assign)) { 83 entry->assign->remove(); 84 progress = true; 85 86 if (debug) { 87 printf("Removed assignment to %s@%p\n", 88 entry->var->name, (void *) entry->var); 89 } 90 } 91 } else { 92 /* If there are no assignments or references to the variable left, 93 * then we can remove its declaration. 94 */ 95 96 /* uniform initializers are precious, and could get used by another 97 * stage. 98 */ 99 if (entry->var->mode == ir_var_uniform && 100 entry->var->constant_value) 101 continue; 102 103 entry->var->remove(); 104 progress = true; 105 106 if (debug) { 107 printf("Removed declaration of %s@%p\n", 108 entry->var->name, (void *) entry->var); 109 } 110 } 111 } 112 113 return progress; 114 } 115 116 /** 117 * Does a dead code pass on the functions present in the instruction stream. 118 * 119 * This is suitable for use while the program is not linked, as it will 120 * ignore variable declarations (and the assignments to them) for variables 121 * with global scope. 122 */ 123 bool 124 do_dead_code_unlinked(exec_list *instructions) 125 { 126 bool progress = false; 127 128 foreach_iter(exec_list_iterator, iter, *instructions) { 129 ir_instruction *ir = (ir_instruction *)iter.get(); 130 ir_function *f = ir->as_function(); 131 if (f) { 132 foreach_iter(exec_list_iterator, sigiter, *f) { 133 ir_function_signature *sig = 134 (ir_function_signature *) sigiter.get(); 135 if (do_dead_code(&sig->body)) 136 progress = true; 137 } 138 } 139 } 140 141 return progress; 142 } 143