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25 * \file opt_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.
37 #include "ir_basic_block.h"
38 #include "ir_optimization.h"
39 #include "glsl_types.h"
41 static bool debug
= false;
43 class assignment_entry
: public exec_node
46 assignment_entry(ir_variable
*lhs
, ir_instruction
*ir
)
58 class kill_for_derefs_visitor
: public ir_hierarchical_visitor
{
60 kill_for_derefs_visitor(exec_list
*assignments
)
62 this->assignments
= assignments
;
65 virtual ir_visitor_status
visit(ir_dereference_variable
*ir
)
67 ir_variable
*const var
= ir
->variable_referenced();
69 foreach_iter(exec_list_iterator
, iter
, *this->assignments
) {
70 assignment_entry
*entry
= (assignment_entry
*)iter
.get();
72 if (entry
->lhs
== var
) {
74 printf("kill %s\n", entry
->lhs
->name
);
79 return visit_continue
;
83 exec_list
*assignments
;
86 class array_index_visit
: public ir_hierarchical_visitor
{
88 array_index_visit(ir_hierarchical_visitor
*v
)
93 virtual ir_visitor_status
visit_enter(class ir_dereference_array
*ir
)
95 ir
->array_index
->accept(visitor
);
96 return visit_continue
;
99 static void run(ir_instruction
*ir
, ir_hierarchical_visitor
*v
)
101 array_index_visit
top_visit(v
);
102 ir
->accept(& top_visit
);
105 ir_hierarchical_visitor
*visitor
;
110 * Adds an entry to the available copy list if it's a plain assignment
111 * of a variable to a variable.
114 process_assignment(void *ctx
, ir_assignment
*ir
, exec_list
*assignments
)
116 ir_variable
*var
= NULL
;
117 bool progress
= false;
118 kill_for_derefs_visitor
v(assignments
);
120 /* Kill assignment entries for things used to produce this assignment. */
123 ir
->condition
->accept(&v
);
126 /* Kill assignment enties used as array indices.
128 array_index_visit::run(ir
->lhs
, &v
);
129 var
= ir
->lhs
->variable_referenced();
132 /* Now, check if we did a whole-variable assignment. */
133 if (!ir
->condition
&& (ir
->whole_variable_written() != NULL
)) {
134 /* We did a whole-variable assignment. So, any instruction in
135 * the assignment list with the same LHS is dead.
138 printf("looking for %s to remove\n", var
->name
);
139 foreach_iter(exec_list_iterator
, iter
, *assignments
) {
140 assignment_entry
*entry
= (assignment_entry
*)iter
.get();
142 if (entry
->lhs
== var
) {
144 printf("removing %s\n", var
->name
);
152 /* Add this instruction to the assignment list available to be removed.
153 * But not if the assignment has other side effects.
158 assignment_entry
*entry
= new(ctx
) assignment_entry(var
, ir
);
159 assignments
->push_tail(entry
);
162 printf("add %s\n", var
->name
);
164 printf("current entries\n");
165 foreach_iter(exec_list_iterator
, iter
, *assignments
) {
166 assignment_entry
*entry
= (assignment_entry
*)iter
.get();
168 printf(" %s\n", entry
->lhs
->name
);
176 dead_code_local_basic_block(ir_instruction
*first
,
177 ir_instruction
*last
,
180 ir_instruction
*ir
, *ir_next
;
181 /* List of avaialble_copy */
182 exec_list assignments
;
183 bool *out_progress
= (bool *)data
;
184 bool progress
= false;
186 void *ctx
= ralloc_context(NULL
);
187 /* Safe looping, since process_assignment */
188 for (ir
= first
, ir_next
= (ir_instruction
*)first
->next
;;
189 ir
= ir_next
, ir_next
= (ir_instruction
*)ir
->next
) {
190 ir_assignment
*ir_assign
= ir
->as_assignment();
198 progress
= process_assignment(ctx
, ir_assign
, &assignments
) || progress
;
200 kill_for_derefs_visitor
kill(&assignments
);
207 *out_progress
= progress
;
212 * Does a copy propagation pass on the code present in the instruction stream.
215 do_dead_code_local(exec_list
*instructions
)
217 bool progress
= false;
219 call_for_basic_blocks(instructions
, dead_code_local_basic_block
, &progress
);