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25 * \file opt_constant_variable.cpp
27 * Marks variables assigned a single constant value over the course
28 * of the program as constant.
30 * The goal here is to trigger further constant folding and then dead
31 * code elimination. This is common with vector/matrix constructors
32 * and calls to builtin functions.
36 #include "ir_visitor.h"
37 #include "ir_optimization.h"
38 #include "glsl_types.h"
42 struct assignment_entry {
46 ir_constant *constval;
50 class ir_constant_variable_visitor : public ir_hierarchical_visitor {
52 virtual ir_visitor_status visit_enter(ir_dereference_variable *);
53 virtual ir_visitor_status visit(ir_variable *);
54 virtual ir_visitor_status visit_enter(ir_assignment *);
55 virtual ir_visitor_status visit_enter(ir_call *);
60 } /* unnamed namespace */
62 static struct assignment_entry *
63 get_assignment_entry(ir_variable *var, exec_list *list)
65 struct assignment_entry *entry;
67 foreach_list_typed(struct assignment_entry, entry, link, list) {
68 if (entry->var == var)
72 entry = (struct assignment_entry *)calloc(1, sizeof(*entry));
74 list->push_head(&entry->link);
79 ir_constant_variable_visitor::visit(ir_variable *ir)
81 struct assignment_entry *entry = get_assignment_entry(ir, &this->list);
82 entry->our_scope = true;
83 return visit_continue;
86 /* Skip derefs of variables so that we can detect declarations. */
88 ir_constant_variable_visitor::visit_enter(ir_dereference_variable *ir)
91 return visit_continue_with_parent;
95 ir_constant_variable_visitor::visit_enter(ir_assignment *ir)
97 ir_constant *constval;
98 struct assignment_entry *entry;
100 entry = get_assignment_entry(ir->lhs->variable_referenced(), &this->list);
102 entry->assignment_count++;
104 /* If it's already constant, don't do the work. */
105 if (entry->var->constant_value)
106 return visit_continue;
108 /* OK, now find if we actually have all the right conditions for
109 * this to be a constant value assigned to the var.
112 return visit_continue;
114 ir_variable *var = ir->whole_variable_written();
116 return visit_continue;
118 constval = ir->rhs->constant_expression_value();
120 return visit_continue;
122 /* Mark this entry as having a constant assignment (if the
123 * assignment count doesn't go >1). do_constant_variable will fix
124 * up the variable with the constant value later.
126 entry->constval = constval;
128 return visit_continue;
132 ir_constant_variable_visitor::visit_enter(ir_call *ir)
134 /* Mark any out parameters as assigned to */
135 exec_list_iterator sig_iter = ir->callee->parameters.iterator();
136 foreach_iter(exec_list_iterator, iter, *ir) {
137 ir_rvalue *param_rval = (ir_rvalue *)iter.get();
138 ir_variable *param = (ir_variable *)sig_iter.get();
140 if (param->mode == ir_var_out ||
141 param->mode == ir_var_inout) {
142 ir_variable *var = param_rval->variable_referenced();
143 struct assignment_entry *entry;
146 entry = get_assignment_entry(var, &this->list);
147 entry->assignment_count++;
152 /* Mark the return storage as having been assigned to */
153 if (ir->return_deref != NULL) {
154 ir_variable *var = ir->return_deref->variable_referenced();
155 struct assignment_entry *entry;
158 entry = get_assignment_entry(var, &this->list);
159 entry->assignment_count++;
162 return visit_continue;
166 * Does a copy propagation pass on the code present in the instruction stream.
169 do_constant_variable(exec_list *instructions)
171 bool progress = false;
172 ir_constant_variable_visitor v;
176 while (!v.list.is_empty()) {
178 struct assignment_entry *entry;
179 entry = exec_node_data(struct assignment_entry, v.list.head, link);
181 if (entry->assignment_count == 1 && entry->constval && entry->our_scope) {
182 entry->var->constant_value = entry->constval;
185 entry->link.remove();
193 do_constant_variable_unlinked(exec_list *instructions)
195 bool progress = false;
197 foreach_iter(exec_list_iterator, iter, *instructions) {
198 ir_instruction *ir = (ir_instruction *)iter.get();
199 ir_function *f = ir->as_function();
201 foreach_iter(exec_list_iterator, sigiter, *f) {
202 ir_function_signature *sig =
203 (ir_function_signature *) sigiter.get();
204 if (do_constant_variable(&sig->body))