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25 * \file opt_copy_propagation.cpp
27 * Moves usage of recently-copied variables to the previous copy of
30 * This should reduce the number of MOV instructions in the generated
31 * programs unless copy propagation is also done on the LIR, and may
32 * help anyway by triggering other optimizations that live in the HIR.
36 #include "ir_visitor.h"
37 #include "ir_basic_block.h"
38 #include "ir_optimization.h"
39 #include "glsl_types.h"
43 class acp_entry
: public exec_node
46 acp_entry(ir_variable
*lhs
, ir_variable
*rhs
)
59 class kill_entry
: public exec_node
62 kill_entry(ir_variable
*var
)
71 class ir_copy_propagation_visitor
: public ir_hierarchical_visitor
{
73 ir_copy_propagation_visitor()
76 mem_ctx
= ralloc_context(0);
77 this->acp
= new(mem_ctx
) exec_list
;
78 this->kills
= new(mem_ctx
) exec_list
;
80 ~ir_copy_propagation_visitor()
85 virtual ir_visitor_status
visit(class ir_dereference_variable
*);
86 virtual ir_visitor_status
visit_enter(class ir_loop
*);
87 virtual ir_visitor_status
visit_enter(class ir_function_signature
*);
88 virtual ir_visitor_status
visit_enter(class ir_function
*);
89 virtual ir_visitor_status
visit_leave(class ir_assignment
*);
90 virtual ir_visitor_status
visit_enter(class ir_call
*);
91 virtual ir_visitor_status
visit_enter(class ir_if
*);
93 void add_copy(ir_assignment
*ir
);
94 void kill(ir_variable
*ir
);
95 void handle_if_block(exec_list
*instructions
);
97 /** List of acp_entry: The available copies to propagate */
100 * List of kill_entry: The variables whose values were killed in this
112 } /* unnamed namespace */
115 ir_copy_propagation_visitor::visit_enter(ir_function_signature
*ir
)
117 /* Treat entry into a function signature as a completely separate
118 * block. Any instructions at global scope will be shuffled into
119 * main() at link time, so they're irrelevant to us.
121 exec_list
*orig_acp
= this->acp
;
122 exec_list
*orig_kills
= this->kills
;
123 bool orig_killed_all
= this->killed_all
;
125 this->acp
= new(mem_ctx
) exec_list
;
126 this->kills
= new(mem_ctx
) exec_list
;
127 this->killed_all
= false;
129 visit_list_elements(this, &ir
->body
);
131 ralloc_free(this->acp
);
132 ralloc_free(this->kills
);
134 this->kills
= orig_kills
;
135 this->acp
= orig_acp
;
136 this->killed_all
= orig_killed_all
;
138 return visit_continue_with_parent
;
142 ir_copy_propagation_visitor::visit_leave(ir_assignment
*ir
)
144 kill(ir
->lhs
->variable_referenced());
148 return visit_continue
;
152 ir_copy_propagation_visitor::visit_enter(ir_function
*ir
)
155 return visit_continue
;
159 * Replaces dereferences of ACP RHS variables with ACP LHS variables.
161 * This is where the actual copy propagation occurs. Note that the
162 * rewriting of ir_dereference means that the ir_dereference instance
163 * must not be shared by multiple IR operations!
166 ir_copy_propagation_visitor::visit(ir_dereference_variable
*ir
)
168 if (this->in_assignee
)
169 return visit_continue
;
171 ir_variable
*var
= ir
->var
;
173 foreach_in_list(acp_entry
, entry
, this->acp
) {
174 if (var
== entry
->lhs
) {
175 ir
->var
= entry
->rhs
;
176 this->progress
= true;
181 return visit_continue
;
186 ir_copy_propagation_visitor::visit_enter(ir_call
*ir
)
188 /* Do copy propagation on call parameters, but skip any out params */
189 foreach_two_lists(formal_node
, &ir
->callee
->parameters
,
190 actual_node
, &ir
->actual_parameters
) {
191 ir_variable
*sig_param
= (ir_variable
*) formal_node
;
192 ir_rvalue
*ir
= (ir_rvalue
*) actual_node
;
193 if (sig_param
->data
.mode
!= ir_var_function_out
194 && sig_param
->data
.mode
!= ir_var_function_inout
) {
199 /* Since we're unlinked, we don't (necessarily) know the side effects of
200 * this call. So kill all copies.
203 this->killed_all
= true;
205 return visit_continue_with_parent
;
209 ir_copy_propagation_visitor::handle_if_block(exec_list
*instructions
)
211 exec_list
*orig_acp
= this->acp
;
212 exec_list
*orig_kills
= this->kills
;
213 bool orig_killed_all
= this->killed_all
;
215 this->acp
= new(mem_ctx
) exec_list
;
216 this->kills
= new(mem_ctx
) exec_list
;
217 this->killed_all
= false;
219 /* Populate the initial acp with a copy of the original */
220 foreach_in_list(acp_entry
, a
, orig_acp
) {
221 this->acp
->push_tail(new(this->acp
) acp_entry(a
->lhs
, a
->rhs
));
224 visit_list_elements(this, instructions
);
226 if (this->killed_all
) {
227 orig_acp
->make_empty();
230 exec_list
*new_kills
= this->kills
;
231 this->kills
= orig_kills
;
232 ralloc_free(this->acp
);
233 this->acp
= orig_acp
;
234 this->killed_all
= this->killed_all
|| orig_killed_all
;
236 foreach_in_list(kill_entry
, k
, new_kills
) {
240 ralloc_free(new_kills
);
244 ir_copy_propagation_visitor::visit_enter(ir_if
*ir
)
246 ir
->condition
->accept(this);
248 handle_if_block(&ir
->then_instructions
);
249 handle_if_block(&ir
->else_instructions
);
251 /* handle_if_block() already descended into the children. */
252 return visit_continue_with_parent
;
256 ir_copy_propagation_visitor::visit_enter(ir_loop
*ir
)
258 exec_list
*orig_acp
= this->acp
;
259 exec_list
*orig_kills
= this->kills
;
260 bool orig_killed_all
= this->killed_all
;
262 /* FINISHME: For now, the initial acp for loops is totally empty.
263 * We could go through once, then go through again with the acp
264 * cloned minus the killed entries after the first run through.
266 this->acp
= new(mem_ctx
) exec_list
;
267 this->kills
= new(mem_ctx
) exec_list
;
268 this->killed_all
= false;
270 visit_list_elements(this, &ir
->body_instructions
);
272 if (this->killed_all
) {
273 orig_acp
->make_empty();
276 exec_list
*new_kills
= this->kills
;
277 this->kills
= orig_kills
;
278 ralloc_free(this->acp
);
279 this->acp
= orig_acp
;
280 this->killed_all
= this->killed_all
|| orig_killed_all
;
282 foreach_in_list(kill_entry
, k
, new_kills
) {
286 ralloc_free(new_kills
);
288 /* already descended into the children. */
289 return visit_continue_with_parent
;
293 ir_copy_propagation_visitor::kill(ir_variable
*var
)
297 /* Remove any entries currently in the ACP for this kill. */
298 foreach_in_list_safe(acp_entry
, entry
, acp
) {
299 if (entry
->lhs
== var
|| entry
->rhs
== var
) {
304 /* Add the LHS variable to the list of killed variables in this block.
306 this->kills
->push_tail(new(this->kills
) kill_entry(var
));
310 * Adds an entry to the available copy list if it's a plain assignment
311 * of a variable to a variable.
314 ir_copy_propagation_visitor::add_copy(ir_assignment
*ir
)
321 ir_variable
*lhs_var
= ir
->whole_variable_written();
322 ir_variable
*rhs_var
= ir
->rhs
->whole_variable_referenced();
324 if ((lhs_var
!= NULL
) && (rhs_var
!= NULL
)) {
325 if (lhs_var
== rhs_var
) {
326 /* This is a dumb assignment, but we've conveniently noticed
327 * it here. Removing it now would mess up the loop iteration
328 * calling us. Just flag it to not execute, and someone else
329 * will clean up the mess.
331 ir
->condition
= new(ralloc_parent(ir
)) ir_constant(false);
332 this->progress
= true;
334 entry
= new(this->acp
) acp_entry(lhs_var
, rhs_var
);
335 this->acp
->push_tail(entry
);
341 * Does a copy propagation pass on the code present in the instruction stream.
344 do_copy_propagation(exec_list
*instructions
)
346 ir_copy_propagation_visitor v
;
348 visit_list_elements(&v
, instructions
);