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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.
37 #include "ir_print_visitor.h"
38 #include "ir_basic_block.h"
39 #include "ir_optimization.h"
40 #include "glsl_types.h"
42 static bool debug
= false;
44 class assignment_entry
: public exec_node
47 assignment_entry(ir_variable
*lhs
, ir_instruction
*ir
)
59 class kill_for_derefs_visitor
: public ir_hierarchical_visitor
{
61 kill_for_derefs_visitor(exec_list
*assignments
)
63 this->assignments
= assignments
;
66 virtual ir_visitor_status
visit(ir_dereference_variable
*ir
)
68 ir_variable
*const var
= ir
->variable_referenced();
70 foreach_iter(exec_list_iterator
, iter
, *this->assignments
) {
71 assignment_entry
*entry
= (assignment_entry
*)iter
.get();
73 if (entry
->lhs
== var
) {
75 printf("kill %s\n", entry
->lhs
->name
);
80 return visit_continue
;
84 exec_list
*assignments
;
87 class array_index_visit
: public ir_hierarchical_visitor
{
89 array_index_visit(ir_hierarchical_visitor
*v
)
94 virtual ir_visitor_status
visit_enter(class ir_dereference_array
*ir
)
96 ir
->array_index
->accept(visitor
);
97 return visit_continue
;
100 static void run(ir_instruction
*ir
, ir_hierarchical_visitor
*v
)
102 array_index_visit
top_visit(v
);
103 ir
->accept(& top_visit
);
106 ir_hierarchical_visitor
*visitor
;
111 * Adds an entry to the available copy list if it's a plain assignment
112 * of a variable to a variable.
115 process_assignment(ir_assignment
*ir
, exec_list
*assignments
)
117 ir_variable
*var
= NULL
;
118 bool progress
= false;
119 kill_for_derefs_visitor
v(assignments
);
121 /* Kill assignment entries for things used to produce this assignment. */
124 ir
->condition
->accept(&v
);
127 /* Kill assignment enties used as array indices.
129 array_index_visit::run(ir
->lhs
, &v
);
130 var
= ir
->lhs
->variable_referenced();
133 bool always_assign
= true;
135 ir_constant
*condition
= ir
->condition
->as_constant();
136 if (!condition
|| !condition
->value
.b
[0])
137 always_assign
= false;
140 /* Now, check if we did a whole-variable assignment. */
141 if (always_assign
&& (ir
->lhs
->whole_variable_referenced() != NULL
)) {
142 /* We did a whole-variable assignment. So, any instruction in
143 * the assignment list with the same LHS is dead.
146 printf("looking for %s to remove\n", var
->name
);
147 foreach_iter(exec_list_iterator
, iter
, *assignments
) {
148 assignment_entry
*entry
= (assignment_entry
*)iter
.get();
150 if (entry
->lhs
== var
) {
152 printf("removing %s\n", var
->name
);
160 /* Add this instruction to the assignment list. */
161 assignment_entry
*entry
= new assignment_entry(var
, ir
);
162 assignments
->push_tail(entry
);
165 printf("add %s\n", var
->name
);
167 printf("current entries\n");
168 foreach_iter(exec_list_iterator
, iter
, *assignments
) {
169 assignment_entry
*entry
= (assignment_entry
*)iter
.get();
171 printf(" %s\n", entry
->lhs
->name
);
179 dead_code_local_basic_block(ir_instruction
*first
,
180 ir_instruction
*last
,
183 ir_instruction
*ir
, *ir_next
;
184 /* List of avaialble_copy */
185 exec_list assignments
;
186 bool *out_progress
= (bool *)data
;
187 bool progress
= false;
189 /* Safe looping, since process_assignment */
190 for (ir
= first
, ir_next
= (ir_instruction
*)first
->next
;;
191 ir
= ir_next
, ir_next
= (ir_instruction
*)ir
->next
) {
192 ir_assignment
*ir_assign
= ir
->as_assignment();
201 progress
= process_assignment(ir_assign
, &assignments
) || progress
;
203 kill_for_derefs_visitor
kill(&assignments
);
210 *out_progress
= progress
;
214 * Does a copy propagation pass on the code present in the instruction stream.
217 do_dead_code_local(exec_list
*instructions
)
219 bool progress
= false;
221 call_for_basic_blocks(instructions
, dead_code_local_basic_block
, &progress
);