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25 * \file opt_copy_propagation_elements.cpp
27 * Replaces usage of recently-copied components of variables with the
28 * previous copy of the variable.
30 * This pass can be compared with opt_copy_propagation, which operands
31 * on arbitrary whole-variable copies. However, in order to handle
32 * the copy propagation of swizzled variables or writemasked writes,
33 * we want to track things on a channel-wise basis. I found that
34 * trying to mix the swizzled/writemasked support here with the
35 * whole-variable stuff in opt_copy_propagation.cpp just made a mess,
36 * so this is separate despite the ACP handling being somewhat
39 * This should reduce the number of MOV instructions in the generated
40 * programs unless copy propagation is also done on the LIR, and may
41 * help anyway by triggering other optimizations that live in the HIR.
45 #include "ir_rvalue_visitor.h"
46 #include "ir_basic_block.h"
47 #include "ir_optimization.h"
48 #include "glsl_types.h"
50 static bool debug
= false;
52 class acp_entry
: public exec_node
55 acp_entry(ir_variable
*lhs
, ir_variable
*rhs
, int write_mask
, int swizzle
[4])
59 this->write_mask
= write_mask
;
60 memcpy(this->swizzle
, swizzle
, sizeof(this->swizzle
));
63 acp_entry(acp_entry
*a
)
67 this->write_mask
= a
->write_mask
;
68 memcpy(this->swizzle
, a
->swizzle
, sizeof(this->swizzle
));
73 unsigned int write_mask
;
78 class kill_entry
: public exec_node
81 kill_entry(ir_variable
*var
, int write_mask
)
84 this->write_mask
= write_mask
;
88 unsigned int write_mask
;
91 class ir_copy_propagation_elements_visitor
: public ir_rvalue_visitor
{
93 ir_copy_propagation_elements_visitor()
95 this->progress
= false;
96 this->mem_ctx
= ralloc_context(NULL
);
97 this->shader_mem_ctx
= NULL
;
98 this->acp
= new(mem_ctx
) exec_list
;
99 this->kills
= new(mem_ctx
) exec_list
;
101 ~ir_copy_propagation_elements_visitor()
103 ralloc_free(mem_ctx
);
106 virtual ir_visitor_status
visit_enter(class ir_loop
*);
107 virtual ir_visitor_status
visit_enter(class ir_function_signature
*);
108 virtual ir_visitor_status
visit_leave(class ir_assignment
*);
109 virtual ir_visitor_status
visit_enter(class ir_call
*);
110 virtual ir_visitor_status
visit_enter(class ir_if
*);
111 virtual ir_visitor_status
visit_leave(class ir_swizzle
*);
113 void handle_rvalue(ir_rvalue
**rvalue
);
115 void add_copy(ir_assignment
*ir
);
116 void kill(kill_entry
*k
);
117 void handle_if_block(exec_list
*instructions
);
119 /** List of acp_entry: The available copies to propagate */
122 * List of kill_entry: The variables whose values were killed in this
131 /* Context for our local data structures. */
133 /* Context for allocating new shader nodes. */
134 void *shader_mem_ctx
;
138 ir_copy_propagation_elements_visitor::visit_enter(ir_function_signature
*ir
)
140 /* Treat entry into a function signature as a completely separate
141 * block. Any instructions at global scope will be shuffled into
142 * main() at link time, so they're irrelevant to us.
144 exec_list
*orig_acp
= this->acp
;
145 exec_list
*orig_kills
= this->kills
;
146 bool orig_killed_all
= this->killed_all
;
148 this->acp
= new(mem_ctx
) exec_list
;
149 this->kills
= new(mem_ctx
) exec_list
;
150 this->killed_all
= false;
152 visit_list_elements(this, &ir
->body
);
154 this->kills
= orig_kills
;
155 this->acp
= orig_acp
;
156 this->killed_all
= orig_killed_all
;
158 return visit_continue_with_parent
;
162 ir_copy_propagation_elements_visitor::visit_leave(ir_assignment
*ir
)
164 ir_dereference_variable
*lhs
= ir
->lhs
->as_dereference_variable();
165 ir_variable
*var
= ir
->lhs
->variable_referenced();
167 if (var
->type
->is_scalar() || var
->type
->is_vector()) {
171 k
= new(mem_ctx
) kill_entry(var
, ir
->write_mask
);
173 k
= new(mem_ctx
) kill_entry(var
, ~0);
180 return visit_continue
;
184 ir_copy_propagation_elements_visitor::visit_leave(ir_swizzle
*ir
)
186 /* Don't visit the values of swizzles since they are handled while
187 * visiting the swizzle itself.
189 return visit_continue
;
193 * Replaces dereferences of ACP RHS variables with ACP LHS variables.
195 * This is where the actual copy propagation occurs. Note that the
196 * rewriting of ir_dereference means that the ir_dereference instance
197 * must not be shared by multiple IR operations!
200 ir_copy_propagation_elements_visitor::handle_rvalue(ir_rvalue
**ir
)
203 ir_dereference_variable
*deref_var
;
204 ir_variable
*source
[4] = {NULL
, NULL
, NULL
, NULL
};
211 ir_swizzle
*swizzle
= (*ir
)->as_swizzle();
213 deref_var
= swizzle
->val
->as_dereference_variable();
217 swizzle_chan
[0] = swizzle
->mask
.x
;
218 swizzle_chan
[1] = swizzle
->mask
.y
;
219 swizzle_chan
[2] = swizzle
->mask
.z
;
220 swizzle_chan
[3] = swizzle
->mask
.w
;
221 chans
= swizzle
->type
->vector_elements
;
223 deref_var
= (*ir
)->as_dereference_variable();
231 chans
= deref_var
->type
->vector_elements
;
234 if (this->in_assignee
)
237 ir_variable
*var
= deref_var
->var
;
239 /* Try to find ACP entries covering swizzle_chan[], hoping they're
240 * the same source variable.
242 foreach_iter(exec_list_iterator
, iter
, *this->acp
) {
243 acp_entry
*entry
= (acp_entry
*)iter
.get();
245 if (var
== entry
->lhs
) {
246 for (int c
= 0; c
< chans
; c
++) {
247 if (entry
->write_mask
& (1 << swizzle_chan
[c
])) {
248 source
[c
] = entry
->rhs
;
249 source_chan
[c
] = entry
->swizzle
[swizzle_chan
[c
]];
255 /* Make sure all channels are copying from the same source variable. */
258 for (int c
= 1; c
< chans
; c
++) {
259 if (source
[c
] != source
[0])
264 shader_mem_ctx
= ralloc_parent(deref_var
);
267 printf("Copy propagation from:\n");
271 deref_var
= new(shader_mem_ctx
) ir_dereference_variable(source
[0]);
272 *ir
= new(shader_mem_ctx
) ir_swizzle(deref_var
,
288 ir_copy_propagation_elements_visitor::visit_enter(ir_call
*ir
)
290 /* Do copy propagation on call parameters, but skip any out params */
291 exec_list_iterator sig_param_iter
= ir
->get_callee()->parameters
.iterator();
292 foreach_iter(exec_list_iterator
, iter
, ir
->actual_parameters
) {
293 ir_variable
*sig_param
= (ir_variable
*)sig_param_iter
.get();
294 ir_instruction
*ir
= (ir_instruction
*)iter
.get();
295 if (sig_param
->mode
!= ir_var_out
&& sig_param
->mode
!= ir_var_inout
) {
298 sig_param_iter
.next();
301 /* Since we're unlinked, we don't (necessarily) know the side effects of
302 * this call. So kill all copies.
305 this->killed_all
= true;
307 return visit_continue_with_parent
;
311 ir_copy_propagation_elements_visitor::handle_if_block(exec_list
*instructions
)
313 exec_list
*orig_acp
= this->acp
;
314 exec_list
*orig_kills
= this->kills
;
315 bool orig_killed_all
= this->killed_all
;
317 this->acp
= new(mem_ctx
) exec_list
;
318 this->kills
= new(mem_ctx
) exec_list
;
319 this->killed_all
= false;
321 /* Populate the initial acp with a copy of the original */
322 foreach_iter(exec_list_iterator
, iter
, *orig_acp
) {
323 acp_entry
*a
= (acp_entry
*)iter
.get();
324 this->acp
->push_tail(new(this->mem_ctx
) acp_entry(a
));
327 visit_list_elements(this, instructions
);
329 if (this->killed_all
) {
330 orig_acp
->make_empty();
333 exec_list
*new_kills
= this->kills
;
334 this->kills
= orig_kills
;
335 this->acp
= orig_acp
;
336 this->killed_all
= this->killed_all
|| orig_killed_all
;
338 /* Move the new kills into the parent block's list, removing them
339 * from the parent's ACP list in the process.
341 foreach_list_safe(node
, new_kills
) {
342 kill_entry
*k
= (kill_entry
*)node
;
348 ir_copy_propagation_elements_visitor::visit_enter(ir_if
*ir
)
350 ir
->condition
->accept(this);
352 handle_if_block(&ir
->then_instructions
);
353 handle_if_block(&ir
->else_instructions
);
355 /* handle_if_block() already descended into the children. */
356 return visit_continue_with_parent
;
360 ir_copy_propagation_elements_visitor::visit_enter(ir_loop
*ir
)
362 exec_list
*orig_acp
= this->acp
;
363 exec_list
*orig_kills
= this->kills
;
364 bool orig_killed_all
= this->killed_all
;
366 /* FINISHME: For now, the initial acp for loops is totally empty.
367 * We could go through once, then go through again with the acp
368 * cloned minus the killed entries after the first run through.
370 this->acp
= new(mem_ctx
) exec_list
;
371 this->kills
= new(mem_ctx
) exec_list
;
372 this->killed_all
= false;
374 visit_list_elements(this, &ir
->body_instructions
);
376 if (this->killed_all
) {
377 orig_acp
->make_empty();
380 exec_list
*new_kills
= this->kills
;
381 this->kills
= orig_kills
;
382 this->acp
= orig_acp
;
383 this->killed_all
= this->killed_all
|| orig_killed_all
;
385 foreach_list_safe(node
, new_kills
) {
386 kill_entry
*k
= (kill_entry
*)node
;
390 /* already descended into the children. */
391 return visit_continue_with_parent
;
394 /* Remove any entries currently in the ACP for this kill. */
396 ir_copy_propagation_elements_visitor::kill(kill_entry
*k
)
398 foreach_list_safe(node
, acp
) {
399 acp_entry
*entry
= (acp_entry
*)node
;
401 if (entry
->lhs
== k
->var
) {
402 entry
->write_mask
= entry
->write_mask
& ~k
->write_mask
;
403 if (entry
->write_mask
== 0) {
408 if (entry
->rhs
== k
->var
) {
413 /* If we were on a list, remove ourselves before inserting */
417 this->kills
->push_tail(k
);
421 * Adds directly-copied channels between vector variables to the available
422 * copy propagation list.
425 ir_copy_propagation_elements_visitor::add_copy(ir_assignment
*ir
)
428 int orig_swizzle
[4] = {0, 1, 2, 3};
434 ir_dereference_variable
*lhs
= ir
->lhs
->as_dereference_variable();
435 if (!lhs
|| !(lhs
->type
->is_scalar() || lhs
->type
->is_vector()))
438 ir_dereference_variable
*rhs
= ir
->rhs
->as_dereference_variable();
440 ir_swizzle
*swiz
= ir
->rhs
->as_swizzle();
444 rhs
= swiz
->val
->as_dereference_variable();
448 orig_swizzle
[0] = swiz
->mask
.x
;
449 orig_swizzle
[1] = swiz
->mask
.y
;
450 orig_swizzle
[2] = swiz
->mask
.z
;
451 orig_swizzle
[3] = swiz
->mask
.w
;
454 /* Move the swizzle channels out to the positions they match in the
455 * destination. We don't want to have to rewrite the swizzle[]
456 * array every time we clear a bit of the write_mask.
459 for (int i
= 0; i
< 4; i
++) {
460 if (ir
->write_mask
& (1 << i
))
461 swizzle
[i
] = orig_swizzle
[j
++];
464 int write_mask
= ir
->write_mask
;
465 if (lhs
->var
== rhs
->var
) {
466 /* If this is a copy from the variable to itself, then we need
467 * to be sure not to include the updated channels from this
468 * instruction in the set of new source channels to be
469 * copy-propagated from.
471 for (int i
= 0; i
< 4; i
++) {
472 if (ir
->write_mask
& (1 << orig_swizzle
[i
]))
473 write_mask
&= ~(1 << i
);
477 entry
= new(this->mem_ctx
) acp_entry(lhs
->var
, rhs
->var
, write_mask
,
479 this->acp
->push_tail(entry
);
483 do_copy_propagation_elements(exec_list
*instructions
)
485 ir_copy_propagation_elements_visitor v
;
487 visit_list_elements(&v
, instructions
);