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| 1901 | serge | 1 | /* |
| 2 | * Copyright © 2010 Intel Corporation |
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| 3 | * |
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| 4 | * Permission is hereby granted, free of charge, to any person obtaining a |
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| 5 | * copy of this software and associated documentation files (the "Software"), |
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| 6 | * to deal in the Software without restriction, including without limitation |
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| 7 | * the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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| 8 | * and/or sell copies of the Software, and to permit persons to whom the |
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| 9 | * Software is furnished to do so, subject to the following conditions: |
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| 10 | * |
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| 11 | * The above copyright notice and this permission notice (including the next |
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| 12 | * paragraph) shall be included in all copies or substantial portions of the |
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| 13 | * Software. |
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| 14 | * |
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| 15 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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| 16 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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| 17 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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| 18 | * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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| 19 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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| 20 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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| 21 | * DEALINGS IN THE SOFTWARE. |
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| 22 | */ |
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| 23 | |||
| 24 | /** |
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| 25 | * \file opt_constant_variable.cpp |
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| 26 | * |
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| 27 | * Marks variables assigned a single constant value over the course |
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| 28 | * of the program as constant. |
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| 29 | * |
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| 30 | * The goal here is to trigger further constant folding and then dead |
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| 31 | * code elimination. This is common with vector/matrix constructors |
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| 32 | * and calls to builtin functions. |
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| 33 | */ |
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| 34 | |||
| 35 | #include "ir.h" |
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| 36 | #include "ir_visitor.h" |
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| 37 | #include "ir_optimization.h" |
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| 38 | #include "glsl_types.h" |
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| 39 | |||
| 40 | struct assignment_entry { |
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| 41 | exec_node link; |
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| 42 | int assignment_count; |
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| 43 | ir_variable *var; |
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| 44 | ir_constant *constval; |
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| 45 | bool our_scope; |
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| 46 | }; |
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| 47 | |||
| 48 | class ir_constant_variable_visitor : public ir_hierarchical_visitor { |
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| 49 | public: |
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| 50 | virtual ir_visitor_status visit_enter(ir_dereference_variable *); |
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| 51 | virtual ir_visitor_status visit(ir_variable *); |
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| 52 | virtual ir_visitor_status visit_enter(ir_assignment *); |
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| 53 | virtual ir_visitor_status visit_enter(ir_call *); |
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| 54 | |||
| 55 | exec_list list; |
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| 56 | }; |
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| 57 | |||
| 58 | static struct assignment_entry * |
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| 59 | get_assignment_entry(ir_variable *var, exec_list *list) |
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| 60 | { |
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| 61 | struct assignment_entry *entry; |
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| 62 | |||
| 63 | foreach_list_typed(struct assignment_entry, entry, link, list) { |
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| 64 | if (entry->var == var) |
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| 65 | return entry; |
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| 66 | } |
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| 67 | |||
| 68 | entry = (struct assignment_entry *)calloc(1, sizeof(*entry)); |
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| 69 | entry->var = var; |
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| 70 | list->push_head(&entry->link); |
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| 71 | return entry; |
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| 72 | } |
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| 73 | |||
| 74 | ir_visitor_status |
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| 75 | ir_constant_variable_visitor::visit(ir_variable *ir) |
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| 76 | { |
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| 77 | struct assignment_entry *entry = get_assignment_entry(ir, &this->list); |
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| 78 | entry->our_scope = true; |
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| 79 | return visit_continue; |
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| 80 | } |
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| 81 | |||
| 82 | /* Skip derefs of variables so that we can detect declarations. */ |
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| 83 | ir_visitor_status |
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| 84 | ir_constant_variable_visitor::visit_enter(ir_dereference_variable *ir) |
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| 85 | { |
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| 86 | (void)ir; |
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| 87 | return visit_continue_with_parent; |
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| 88 | } |
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| 89 | |||
| 90 | ir_visitor_status |
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| 91 | ir_constant_variable_visitor::visit_enter(ir_assignment *ir) |
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| 92 | { |
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| 93 | ir_constant *constval; |
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| 94 | struct assignment_entry *entry; |
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| 95 | |||
| 96 | entry = get_assignment_entry(ir->lhs->variable_referenced(), &this->list); |
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| 97 | assert(entry); |
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| 98 | entry->assignment_count++; |
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| 99 | |||
| 100 | /* If it's already constant, don't do the work. */ |
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| 101 | if (entry->var->constant_value) |
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| 102 | return visit_continue; |
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| 103 | |||
| 104 | /* OK, now find if we actually have all the right conditions for |
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| 105 | * this to be a constant value assigned to the var. |
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| 106 | */ |
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| 107 | if (ir->condition) { |
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| 108 | constval = ir->condition->constant_expression_value(); |
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| 109 | if (!constval || !constval->value.b[0]) |
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| 110 | return visit_continue; |
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| 111 | } |
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| 112 | |||
| 113 | ir_variable *var = ir->whole_variable_written(); |
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| 114 | if (!var) |
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| 115 | return visit_continue; |
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| 116 | |||
| 117 | constval = ir->rhs->constant_expression_value(); |
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| 118 | if (!constval) |
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| 119 | return visit_continue; |
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| 120 | |||
| 121 | /* Mark this entry as having a constant assignment (if the |
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| 122 | * assignment count doesn't go >1). do_constant_variable will fix |
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| 123 | * up the variable with the constant value later. |
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| 124 | */ |
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| 125 | entry->constval = constval; |
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| 126 | |||
| 127 | return visit_continue; |
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| 128 | } |
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| 129 | |||
| 130 | ir_visitor_status |
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| 131 | ir_constant_variable_visitor::visit_enter(ir_call *ir) |
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| 132 | { |
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| 133 | exec_list_iterator sig_iter = ir->get_callee()->parameters.iterator(); |
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| 134 | foreach_iter(exec_list_iterator, iter, *ir) { |
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| 135 | ir_rvalue *param_rval = (ir_rvalue *)iter.get(); |
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| 136 | ir_variable *param = (ir_variable *)sig_iter.get(); |
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| 137 | |||
| 138 | if (param->mode == ir_var_out || |
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| 139 | param->mode == ir_var_inout) { |
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| 140 | ir_variable *var = param_rval->variable_referenced(); |
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| 141 | struct assignment_entry *entry; |
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| 142 | |||
| 143 | assert(var); |
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| 144 | entry = get_assignment_entry(var, &this->list); |
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| 145 | entry->assignment_count++; |
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| 146 | } |
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| 147 | sig_iter.next(); |
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| 148 | } |
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| 149 | return visit_continue; |
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| 150 | } |
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| 151 | |||
| 152 | /** |
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| 153 | * Does a copy propagation pass on the code present in the instruction stream. |
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| 154 | */ |
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| 155 | bool |
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| 156 | do_constant_variable(exec_list *instructions) |
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| 157 | { |
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| 158 | bool progress = false; |
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| 159 | ir_constant_variable_visitor v; |
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| 160 | |||
| 161 | v.run(instructions); |
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| 162 | |||
| 163 | while (!v.list.is_empty()) { |
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| 164 | |||
| 165 | struct assignment_entry *entry; |
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| 166 | entry = exec_node_data(struct assignment_entry, v.list.head, link); |
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| 167 | |||
| 168 | if (entry->assignment_count == 1 && entry->constval && entry->our_scope) { |
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| 169 | entry->var->constant_value = entry->constval; |
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| 170 | progress = true; |
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| 171 | } |
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| 172 | entry->link.remove(); |
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| 173 | free(entry); |
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| 174 | } |
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| 175 | |||
| 176 | return progress; |
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| 177 | } |
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| 178 | |||
| 179 | bool |
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| 180 | do_constant_variable_unlinked(exec_list *instructions) |
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| 181 | { |
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| 182 | bool progress = false; |
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| 183 | |||
| 184 | foreach_iter(exec_list_iterator, iter, *instructions) { |
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| 185 | ir_instruction *ir = (ir_instruction *)iter.get(); |
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| 186 | ir_function *f = ir->as_function(); |
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| 187 | if (f) { |
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| 188 | foreach_iter(exec_list_iterator, sigiter, *f) { |
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| 189 | ir_function_signature *sig = |
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| 190 | (ir_function_signature *) sigiter.get(); |
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| 191 | if (do_constant_variable(&sig->body)) |
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| 192 | progress = true; |
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| 193 | } |
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| 194 | } |
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| 195 | } |
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| 196 | |||
| 197 | return progress; |
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| 198 | } |