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25 * \file ir_dead_code_local.cpp
27 * Eliminates local dead assignments from the code.
29 * This operates on basic blocks, tracking assignments and finding if
30 * they're used before the variable is completely reassigned.
32 * Compare this to ir_dead_code.cpp, which operates globally looking
33 * for assignments to variables that are never read.
38 #include "ir_print_visitor.h"
39 #include "ir_basic_block.h"
40 #include "ir_optimization.h"
41 #include "glsl_types.h"
43 static bool debug = false;
45 class assignment_entry : public exec_node
48 assignment_entry(ir_variable *lhs, ir_instruction *ir)
60 class kill_for_derefs_visitor : public ir_hierarchical_visitor {
62 kill_for_derefs_visitor(exec_list *assignments)
64 this->assignments = assignments;
67 virtual ir_visitor_status visit(ir_dereference_variable *ir)
69 ir_variable *const var = ir->variable_referenced();
71 foreach_iter(exec_list_iterator, iter, *this->assignments) {
72 assignment_entry *entry = (assignment_entry *)iter.get();
74 if (entry->lhs == var) {
76 printf("kill %s\n", entry->lhs->name);
81 return visit_continue;
85 exec_list *assignments;
88 class array_index_visit : public ir_hierarchical_visitor {
90 array_index_visit(ir_hierarchical_visitor *v)
95 virtual ir_visitor_status visit_enter(class ir_dereference_array *ir)
97 ir->array_index->accept(visitor);
98 return visit_continue;
101 static void run(ir_instruction *ir, ir_hierarchical_visitor *v)
103 array_index_visit top_visit(v);
104 ir->accept(& top_visit);
107 ir_hierarchical_visitor *visitor;
112 * Adds an entry to the available copy list if it's a plain assignment
113 * of a variable to a variable.
116 process_assignment(ir_assignment *ir, exec_list *assignments)
118 ir_variable *var = NULL;
119 bool progress = false;
120 kill_for_derefs_visitor v(assignments);
122 /* Kill assignment entries for things used to produce this assignment. */
125 ir->condition->accept(&v);
128 /* Kill assignment enties used as array indices.
130 array_index_visit::run(ir->lhs, &v);
131 var = ir->lhs->variable_referenced();
134 bool always_assign = true;
136 ir_constant *condition = ir->condition->as_constant();
137 if (!condition || !condition->value.b[0])
138 always_assign = false;
141 /* Now, check if we did a whole-variable assignment. */
142 if (always_assign && (ir->lhs->whole_variable_referenced() != NULL)) {
143 /* We did a whole-variable assignment. So, any instruction in
144 * the assignment list with the same LHS is dead.
147 printf("looking for %s to remove\n", var->name);
148 foreach_iter(exec_list_iterator, iter, *assignments) {
149 assignment_entry *entry = (assignment_entry *)iter.get();
151 if (entry->lhs == var) {
153 printf("removing %s\n", var->name);
161 /* Add this instruction to the assignment list. */
162 assignment_entry *entry = new assignment_entry(var, ir);
163 assignments->push_tail(entry);
166 printf("add %s\n", var->name);
168 printf("current entries\n");
169 foreach_iter(exec_list_iterator, iter, *assignments) {
170 assignment_entry *entry = (assignment_entry *)iter.get();
172 printf(" %s\n", entry->lhs->name);
180 dead_code_local_basic_block(ir_instruction *first,
181 ir_instruction *last,
184 ir_instruction *ir, *ir_next;
185 /* List of avaialble_copy */
186 exec_list assignments;
187 bool *out_progress = (bool *)data;
188 bool progress = false;
190 /* Safe looping, since process_assignment */
191 for (ir = first, ir_next = (ir_instruction *)first->next;;
192 ir = ir_next, ir_next = (ir_instruction *)ir->next) {
193 ir_assignment *ir_assign = ir->as_assignment();
202 progress = process_assignment(ir_assign, &assignments) || progress;
204 kill_for_derefs_visitor kill(&assignments);
211 *out_progress = progress;
215 * Does a copy propagation pass on the code present in the instruction stream.
218 do_dead_code_local(exec_list *instructions)
220 bool progress = false;
222 call_for_basic_blocks(instructions, dead_code_local_basic_block, &progress);