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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 this->kills
= orig_kills
;
132 this->acp
= orig_acp
;
133 this->killed_all
= orig_killed_all
;
135 return visit_continue_with_parent
;
139 ir_copy_propagation_visitor::visit_leave(ir_assignment
*ir
)
141 kill(ir
->lhs
->variable_referenced());
145 return visit_continue
;
149 ir_copy_propagation_visitor::visit_enter(ir_function
*ir
)
152 return visit_continue
;
156 * Replaces dereferences of ACP RHS variables with ACP LHS variables.
158 * This is where the actual copy propagation occurs. Note that the
159 * rewriting of ir_dereference means that the ir_dereference instance
160 * must not be shared by multiple IR operations!
163 ir_copy_propagation_visitor::visit(ir_dereference_variable
*ir
)
165 if (this->in_assignee
)
166 return visit_continue
;
168 ir_variable
*var
= ir
->var
;
170 foreach_list(n
, this->acp
) {
171 acp_entry
*entry
= (acp_entry
*) n
;
173 if (var
== entry
->lhs
) {
174 ir
->var
= entry
->rhs
;
175 this->progress
= true;
180 return visit_continue
;
185 ir_copy_propagation_visitor::visit_enter(ir_call
*ir
)
187 /* Do copy propagation on call parameters, but skip any out params */
188 foreach_two_lists(formal_node
, &ir
->callee
->parameters
,
189 actual_node
, &ir
->actual_parameters
) {
190 ir_variable
*sig_param
= (ir_variable
*) formal_node
;
191 ir_rvalue
*ir
= (ir_rvalue
*) actual_node
;
192 if (sig_param
->data
.mode
!= ir_var_function_out
193 && sig_param
->data
.mode
!= ir_var_function_inout
) {
198 /* Since we're unlinked, we don't (necessarily) know the side effects of
199 * this call. So kill all copies.
202 this->killed_all
= true;
204 return visit_continue_with_parent
;
208 ir_copy_propagation_visitor::handle_if_block(exec_list
*instructions
)
210 exec_list
*orig_acp
= this->acp
;
211 exec_list
*orig_kills
= this->kills
;
212 bool orig_killed_all
= this->killed_all
;
214 this->acp
= new(mem_ctx
) exec_list
;
215 this->kills
= new(mem_ctx
) exec_list
;
216 this->killed_all
= false;
218 /* Populate the initial acp with a copy of the original */
219 foreach_list(n
, orig_acp
) {
220 acp_entry
*a
= (acp_entry
*) n
;
221 this->acp
->push_tail(new(this->mem_ctx
) 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 this->acp
= orig_acp
;
233 this->killed_all
= this->killed_all
|| orig_killed_all
;
235 foreach_list(n
, new_kills
) {
236 kill_entry
*k
= (kill_entry
*) n
;
242 ir_copy_propagation_visitor::visit_enter(ir_if
*ir
)
244 ir
->condition
->accept(this);
246 handle_if_block(&ir
->then_instructions
);
247 handle_if_block(&ir
->else_instructions
);
249 /* handle_if_block() already descended into the children. */
250 return visit_continue_with_parent
;
254 ir_copy_propagation_visitor::visit_enter(ir_loop
*ir
)
256 exec_list
*orig_acp
= this->acp
;
257 exec_list
*orig_kills
= this->kills
;
258 bool orig_killed_all
= this->killed_all
;
260 /* FINISHME: For now, the initial acp for loops is totally empty.
261 * We could go through once, then go through again with the acp
262 * cloned minus the killed entries after the first run through.
264 this->acp
= new(mem_ctx
) exec_list
;
265 this->kills
= new(mem_ctx
) exec_list
;
266 this->killed_all
= false;
268 visit_list_elements(this, &ir
->body_instructions
);
270 if (this->killed_all
) {
271 orig_acp
->make_empty();
274 exec_list
*new_kills
= this->kills
;
275 this->kills
= orig_kills
;
276 this->acp
= orig_acp
;
277 this->killed_all
= this->killed_all
|| orig_killed_all
;
279 foreach_list(n
, new_kills
) {
280 kill_entry
*k
= (kill_entry
*) n
;
284 /* already descended into the children. */
285 return visit_continue_with_parent
;
289 ir_copy_propagation_visitor::kill(ir_variable
*var
)
293 /* Remove any entries currently in the ACP for this kill. */
294 foreach_list_safe(n
, acp
) {
295 acp_entry
*entry
= (acp_entry
*) n
;
297 if (entry
->lhs
== var
|| entry
->rhs
== var
) {
302 /* Add the LHS variable to the list of killed variables in this block.
304 this->kills
->push_tail(new(this->mem_ctx
) kill_entry(var
));
308 * Adds an entry to the available copy list if it's a plain assignment
309 * of a variable to a variable.
312 ir_copy_propagation_visitor::add_copy(ir_assignment
*ir
)
319 ir_variable
*lhs_var
= ir
->whole_variable_written();
320 ir_variable
*rhs_var
= ir
->rhs
->whole_variable_referenced();
322 if ((lhs_var
!= NULL
) && (rhs_var
!= NULL
)) {
323 if (lhs_var
== rhs_var
) {
324 /* This is a dumb assignment, but we've conveniently noticed
325 * it here. Removing it now would mess up the loop iteration
326 * calling us. Just flag it to not execute, and someone else
327 * will clean up the mess.
329 ir
->condition
= new(ralloc_parent(ir
)) ir_constant(false);
330 this->progress
= true;
332 entry
= new(this->mem_ctx
) acp_entry(lhs_var
, rhs_var
);
333 this->acp
->push_tail(entry
);
339 * Does a copy propagation pass on the code present in the instruction stream.
342 do_copy_propagation(exec_list
*instructions
)
344 ir_copy_propagation_visitor v
;
346 visit_list_elements(&v
, instructions
);