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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 "compiler/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 void handle_loop(class ir_loop
*, bool keep_acp
);
87 virtual ir_visitor_status
visit_enter(class ir_loop
*);
88 virtual ir_visitor_status
visit_enter(class ir_function_signature
*);
89 virtual ir_visitor_status
visit_enter(class ir_function
*);
90 virtual ir_visitor_status
visit_leave(class ir_assignment
*);
91 virtual ir_visitor_status
visit_enter(class ir_call
*);
92 virtual ir_visitor_status
visit_enter(class ir_if
*);
94 void add_copy(ir_assignment
*ir
);
95 void kill(ir_variable
*ir
);
96 void handle_if_block(exec_list
*instructions
);
98 /** List of acp_entry: The available copies to propagate */
101 * List of kill_entry: The variables whose values were killed in this
113 } /* unnamed namespace */
116 ir_copy_propagation_visitor::visit_enter(ir_function_signature
*ir
)
118 /* Treat entry into a function signature as a completely separate
119 * block. Any instructions at global scope will be shuffled into
120 * main() at link time, so they're irrelevant to us.
122 exec_list
*orig_acp
= this->acp
;
123 exec_list
*orig_kills
= this->kills
;
124 bool orig_killed_all
= this->killed_all
;
126 this->acp
= new(mem_ctx
) exec_list
;
127 this->kills
= new(mem_ctx
) exec_list
;
128 this->killed_all
= false;
130 visit_list_elements(this, &ir
->body
);
132 ralloc_free(this->acp
);
133 ralloc_free(this->kills
);
135 this->kills
= orig_kills
;
136 this->acp
= orig_acp
;
137 this->killed_all
= orig_killed_all
;
139 return visit_continue_with_parent
;
143 ir_copy_propagation_visitor::visit_leave(ir_assignment
*ir
)
145 kill(ir
->lhs
->variable_referenced());
149 return visit_continue
;
153 ir_copy_propagation_visitor::visit_enter(ir_function
*ir
)
156 return visit_continue
;
160 * Replaces dereferences of ACP RHS variables with ACP LHS variables.
162 * This is where the actual copy propagation occurs. Note that the
163 * rewriting of ir_dereference means that the ir_dereference instance
164 * must not be shared by multiple IR operations!
167 ir_copy_propagation_visitor::visit(ir_dereference_variable
*ir
)
169 if (this->in_assignee
)
170 return visit_continue
;
172 ir_variable
*var
= ir
->var
;
174 foreach_in_list(acp_entry
, entry
, this->acp
) {
175 if (var
== entry
->lhs
) {
176 ir
->var
= entry
->rhs
;
177 this->progress
= true;
182 return visit_continue
;
187 ir_copy_propagation_visitor::visit_enter(ir_call
*ir
)
189 /* Do copy propagation on call parameters, but skip any out params */
190 foreach_two_lists(formal_node
, &ir
->callee
->parameters
,
191 actual_node
, &ir
->actual_parameters
) {
192 ir_variable
*sig_param
= (ir_variable
*) formal_node
;
193 ir_rvalue
*ir
= (ir_rvalue
*) actual_node
;
194 if (sig_param
->data
.mode
!= ir_var_function_out
195 && sig_param
->data
.mode
!= ir_var_function_inout
) {
200 /* Since we're unlinked, we don't (necessarily) know the side effects of
201 * this call. So kill all copies.
204 this->killed_all
= true;
206 return visit_continue_with_parent
;
210 ir_copy_propagation_visitor::handle_if_block(exec_list
*instructions
)
212 exec_list
*orig_acp
= this->acp
;
213 exec_list
*orig_kills
= this->kills
;
214 bool orig_killed_all
= this->killed_all
;
216 this->acp
= new(mem_ctx
) exec_list
;
217 this->kills
= new(mem_ctx
) exec_list
;
218 this->killed_all
= false;
220 /* Populate the initial acp with a copy of the original */
221 foreach_in_list(acp_entry
, a
, orig_acp
) {
222 this->acp
->push_tail(new(this->acp
) acp_entry(a
->lhs
, a
->rhs
));
225 visit_list_elements(this, instructions
);
227 if (this->killed_all
) {
228 orig_acp
->make_empty();
231 exec_list
*new_kills
= this->kills
;
232 this->kills
= orig_kills
;
233 ralloc_free(this->acp
);
234 this->acp
= orig_acp
;
235 this->killed_all
= this->killed_all
|| orig_killed_all
;
237 foreach_in_list(kill_entry
, k
, new_kills
) {
241 ralloc_free(new_kills
);
245 ir_copy_propagation_visitor::visit_enter(ir_if
*ir
)
247 ir
->condition
->accept(this);
249 handle_if_block(&ir
->then_instructions
);
250 handle_if_block(&ir
->else_instructions
);
252 /* handle_if_block() already descended into the children. */
253 return visit_continue_with_parent
;
257 ir_copy_propagation_visitor::handle_loop(ir_loop
*ir
, bool keep_acp
)
259 exec_list
*orig_acp
= this->acp
;
260 exec_list
*orig_kills
= this->kills
;
261 bool orig_killed_all
= this->killed_all
;
263 this->acp
= new(mem_ctx
) exec_list
;
264 this->kills
= new(mem_ctx
) exec_list
;
265 this->killed_all
= false;
268 /* Populate the initial acp with a copy of the original */
269 foreach_in_list(acp_entry
, a
, orig_acp
) {
270 this->acp
->push_tail(new(this->acp
) acp_entry(a
->lhs
, a
->rhs
));
274 visit_list_elements(this, &ir
->body_instructions
);
276 if (this->killed_all
) {
277 orig_acp
->make_empty();
280 exec_list
*new_kills
= this->kills
;
281 this->kills
= orig_kills
;
282 ralloc_free(this->acp
);
283 this->acp
= orig_acp
;
284 this->killed_all
= this->killed_all
|| orig_killed_all
;
286 foreach_in_list(kill_entry
, k
, new_kills
) {
290 ralloc_free(new_kills
);
294 ir_copy_propagation_visitor::visit_enter(ir_loop
*ir
)
296 /* Make a conservative first pass over the loop with an empty ACP set.
297 * This also removes any killed entries from the original ACP set.
299 handle_loop(ir
, false);
301 /* Then, run it again with the real ACP set, minus any killed entries.
302 * This takes care of propagating values from before the loop into it.
304 handle_loop(ir
, true);
306 /* already descended into the children. */
307 return visit_continue_with_parent
;
311 ir_copy_propagation_visitor::kill(ir_variable
*var
)
315 /* Remove any entries currently in the ACP for this kill. */
316 foreach_in_list_safe(acp_entry
, entry
, acp
) {
317 if (entry
->lhs
== var
|| entry
->rhs
== var
) {
322 /* Add the LHS variable to the list of killed variables in this block.
324 this->kills
->push_tail(new(this->kills
) kill_entry(var
));
328 * Adds an entry to the available copy list if it's a plain assignment
329 * of a variable to a variable.
332 ir_copy_propagation_visitor::add_copy(ir_assignment
*ir
)
339 ir_variable
*lhs_var
= ir
->whole_variable_written();
340 ir_variable
*rhs_var
= ir
->rhs
->whole_variable_referenced();
342 if ((lhs_var
!= NULL
) && (rhs_var
!= NULL
)) {
343 if (lhs_var
== rhs_var
) {
344 /* This is a dumb assignment, but we've conveniently noticed
345 * it here. Removing it now would mess up the loop iteration
346 * calling us. Just flag it to not execute, and someone else
347 * will clean up the mess.
349 ir
->condition
= new(ralloc_parent(ir
)) ir_constant(false);
350 this->progress
= true;
351 } else if (lhs_var
->data
.mode
!= ir_var_shader_storage
&&
352 lhs_var
->data
.mode
!= ir_var_shader_shared
&&
353 lhs_var
->data
.precise
== rhs_var
->data
.precise
) {
354 entry
= new(this->acp
) acp_entry(lhs_var
, rhs_var
);
355 this->acp
->push_tail(entry
);
361 * Does a copy propagation pass on the code present in the instruction stream.
364 do_copy_propagation(exec_list
*instructions
)
366 ir_copy_propagation_visitor v
;
368 visit_list_elements(&v
, instructions
);