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 "compiler/glsl_types.h" 34#include "util/hash_table.h" 35 36static bool debug = false; 37 38/** 39 * Do a dead code pass over instructions and everything that instructions 40 * references. 41 * 42 * Note that this will remove assignments to globals, so it is not suitable 43 * for usage on an unlinked instruction stream. 44 */ 45bool 46do_dead_code(exec_list *instructions, bool uniform_locations_assigned) 47{ 48 ir_variable_refcount_visitor v; 49 bool progress = false; 50 51 v.run(instructions); 52 53 struct hash_entry *e; 54 hash_table_foreach(v.ht, e) { 55 ir_variable_refcount_entry *entry = (ir_variable_refcount_entry *)e->data; 56 57 /* Since each assignment is a reference, the refereneced count must be 58 * greater than or equal to the assignment count. If they are equal, 59 * then all of the references are assignments, and the variable is 60 * dead. 61 * 62 * Note that if the variable is neither assigned nor referenced, both 63 * counts will be zero and will be caught by the equality test. 64 */ 65 assert(entry->referenced_count >= entry->assigned_count); 66 67 if (debug) { 68 printf("%s@%p: %d refs, %d assigns, %sdeclared in our scope\n", 69 entry->var->name, (void *) entry->var, 70 entry->referenced_count, entry->assigned_count, 71 entry->declaration ? "" : "not "); 72 } 73 74 if ((entry->referenced_count > entry->assigned_count) 75 || !entry->declaration) 76 continue; 77 78 /* Section 7.4.1 (Shader Interface Matching) of the OpenGL 4.5 79 * (Core Profile) spec says: 80 * 81 * "With separable program objects, interfaces between shader 82 * stages may involve the outputs from one program object and the 83 * inputs from a second program object. For such interfaces, it is 84 * not possible to detect mismatches at link time, because the 85 * programs are linked separately. When each such program is 86 * linked, all inputs or outputs interfacing with another program 87 * stage are treated as active." 88 */ 89 if (entry->var->data.always_active_io) 90 continue; 91 92 if (!entry->assign_list.is_empty()) { 93 /* Remove all the dead assignments to the variable we found. 94 * Don't do so if it's a shader or function output, though. 95 */ 96 if (entry->var->data.mode != ir_var_function_out && 97 entry->var->data.mode != ir_var_function_inout && 98 entry->var->data.mode != ir_var_shader_out && 99 entry->var->data.mode != ir_var_shader_storage) { 100 101 while (!entry->assign_list.is_empty()) { 102 struct assignment_entry *assignment_entry = 103 exec_node_data(struct assignment_entry, 104 entry->assign_list.get_head_raw(), link); 105 106 assignment_entry->assign->remove(); 107 108 if (debug) { 109 printf("Removed assignment to %s@%p\n", 110 entry->var->name, (void *) entry->var); 111 } 112 113 assignment_entry->link.remove(); 114 free(assignment_entry); 115 } 116 progress = true; 117 } 118 } 119 120 if (entry->assign_list.is_empty()) { 121 /* If there are no assignments or references to the variable left, 122 * then we can remove its declaration. 123 */ 124 125 /* uniform initializers are precious, and could get used by another 126 * stage. Also, once uniform locations have been assigned, the 127 * declaration cannot be deleted. 128 */ 129 if (entry->var->data.mode == ir_var_uniform || 130 entry->var->data.mode == ir_var_shader_storage) { 131 if (uniform_locations_assigned || entry->var->constant_initializer) 132 continue; 133 134 /* Section 2.11.6 (Uniform Variables) of the OpenGL ES 3.0.3 spec 135 * says: 136 * 137 * "All members of a named uniform block declared with a 138 * shared or std140 layout qualifier are considered active, 139 * even if they are not referenced in any shader in the 140 * program. The uniform block itself is also considered 141 * active, even if no member of the block is referenced." 142 * 143 * If the variable is in a uniform block with one of those 144 * layouts, do not eliminate it. 145 */ 146 if (entry->var->is_in_buffer_block()) { 147 if (entry->var->get_interface_type_packing() != 148 GLSL_INTERFACE_PACKING_PACKED) 149 continue; 150 } 151 152 if (entry->var->type->is_subroutine()) 153 continue; 154 } 155 156 entry->var->remove(); 157 progress = true; 158 159 if (debug) { 160 printf("Removed declaration of %s@%p\n", 161 entry->var->name, (void *) entry->var); 162 } 163 } 164 } 165 166 return progress; 167} 168 169/** 170 * Does a dead code pass on the functions present in the instruction stream. 171 * 172 * This is suitable for use while the program is not linked, as it will 173 * ignore variable declarations (and the assignments to them) for variables 174 * with global scope. 175 */ 176bool 177do_dead_code_unlinked(exec_list *instructions) 178{ 179 bool progress = false; 180 181 foreach_in_list(ir_instruction, ir, instructions) { 182 ir_function *f = ir->as_function(); 183 if (f) { 184 foreach_in_list(ir_function_signature, sig, &f->signatures) { 185 /* The setting of the uniform_locations_assigned flag here is 186 * irrelevent. If there is a uniform declaration encountered 187 * inside the body of the function, something has already gone 188 * terribly, terribly wrong. 189 */ 190 if (do_dead_code(&sig->body, false)) 191 progress = true; 192 } 193 } 194 } 195 196 return progress; 197} 198