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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 "compiler/glsl_types.h"
49 #include "util/hash_table.h"
51 static bool debug
= false;
57 /* Class that refers to acp_entry in another exec_list. Used
58 * when making removals based on rhs.
60 class acp_ref
: public exec_node
70 class acp_entry
: public exec_node
73 acp_entry(ir_variable
*lhs
, ir_variable
*rhs
, int write_mask
, int swizzle
[4])
78 this->write_mask
= write_mask
;
79 memcpy(this->swizzle
, swizzle
, sizeof(this->swizzle
));
84 unsigned int write_mask
;
90 class kill_entry
: public exec_node
93 kill_entry(ir_variable
*var
, int write_mask
)
96 this->write_mask
= write_mask
;
100 unsigned int write_mask
;
103 class ir_copy_propagation_elements_visitor
: public ir_rvalue_visitor
{
105 ir_copy_propagation_elements_visitor()
107 this->progress
= false;
108 this->killed_all
= false;
109 this->mem_ctx
= ralloc_context(NULL
);
110 this->shader_mem_ctx
= NULL
;
111 this->kills
= new(mem_ctx
) exec_list
;
115 ~ir_copy_propagation_elements_visitor()
117 ralloc_free(mem_ctx
);
122 lhs_ht
= _mesa_hash_table_create(mem_ctx
, _mesa_hash_pointer
,
123 _mesa_key_pointer_equal
);
124 rhs_ht
= _mesa_hash_table_create(mem_ctx
, _mesa_hash_pointer
,
125 _mesa_key_pointer_equal
);
130 _mesa_hash_table_destroy(lhs_ht
, NULL
);
131 _mesa_hash_table_destroy(rhs_ht
, NULL
);
134 void populate_acp(hash_table
*lhs
, hash_table
*rhs
)
136 struct hash_entry
*entry
;
138 hash_table_foreach(lhs
, entry
) {
139 _mesa_hash_table_insert(lhs_ht
, entry
->key
, entry
->data
);
142 hash_table_foreach(rhs
, entry
) {
143 _mesa_hash_table_insert(rhs_ht
, entry
->key
, entry
->data
);
147 void handle_loop(ir_loop
*, bool keep_acp
);
148 virtual ir_visitor_status
visit_enter(class ir_loop
*);
149 virtual ir_visitor_status
visit_enter(class ir_function_signature
*);
150 virtual ir_visitor_status
visit_leave(class ir_assignment
*);
151 virtual ir_visitor_status
visit_enter(class ir_call
*);
152 virtual ir_visitor_status
visit_enter(class ir_if
*);
153 virtual ir_visitor_status
visit_leave(class ir_swizzle
*);
155 void handle_rvalue(ir_rvalue
**rvalue
);
157 void add_copy(ir_assignment
*ir
);
158 void kill(kill_entry
*k
);
159 void handle_if_block(exec_list
*instructions
);
161 /** Hash of acp_entry: The available copies to propagate */
166 * List of kill_entry: The variables whose values were killed in this
175 /* Context for our local data structures. */
177 /* Context for allocating new shader nodes. */
178 void *shader_mem_ctx
;
181 } /* unnamed namespace */
184 ir_copy_propagation_elements_visitor::visit_enter(ir_function_signature
*ir
)
186 /* Treat entry into a function signature as a completely separate
187 * block. Any instructions at global scope will be shuffled into
188 * main() at link time, so they're irrelevant to us.
190 exec_list
*orig_kills
= this->kills
;
191 bool orig_killed_all
= this->killed_all
;
193 hash_table
*orig_lhs_ht
= lhs_ht
;
194 hash_table
*orig_rhs_ht
= rhs_ht
;
196 this->kills
= new(mem_ctx
) exec_list
;
197 this->killed_all
= false;
201 visit_list_elements(this, &ir
->body
);
203 ralloc_free(this->kills
);
207 this->kills
= orig_kills
;
208 this->killed_all
= orig_killed_all
;
210 lhs_ht
= orig_lhs_ht
;
211 rhs_ht
= orig_rhs_ht
;
213 return visit_continue_with_parent
;
217 ir_copy_propagation_elements_visitor::visit_leave(ir_assignment
*ir
)
219 ir_dereference_variable
*lhs
= ir
->lhs
->as_dereference_variable();
220 ir_variable
*var
= ir
->lhs
->variable_referenced();
222 if (var
->type
->is_scalar() || var
->type
->is_vector()) {
226 k
= new(this->kills
) kill_entry(var
, ir
->write_mask
);
228 k
= new(this->kills
) kill_entry(var
, ~0);
235 return visit_continue
;
239 ir_copy_propagation_elements_visitor::visit_leave(ir_swizzle
*)
241 /* Don't visit the values of swizzles since they are handled while
242 * visiting the swizzle itself.
244 return visit_continue
;
248 * Replaces dereferences of ACP RHS variables with ACP LHS variables.
250 * This is where the actual copy propagation occurs. Note that the
251 * rewriting of ir_dereference means that the ir_dereference instance
252 * must not be shared by multiple IR operations!
255 ir_copy_propagation_elements_visitor::handle_rvalue(ir_rvalue
**ir
)
258 ir_dereference_variable
*deref_var
;
259 ir_variable
*source
[4] = {NULL
, NULL
, NULL
, NULL
};
260 int source_chan
[4] = {0, 0, 0, 0};
262 bool noop_swizzle
= true;
267 ir_swizzle
*swizzle
= (*ir
)->as_swizzle();
269 deref_var
= swizzle
->val
->as_dereference_variable();
273 swizzle_chan
[0] = swizzle
->mask
.x
;
274 swizzle_chan
[1] = swizzle
->mask
.y
;
275 swizzle_chan
[2] = swizzle
->mask
.z
;
276 swizzle_chan
[3] = swizzle
->mask
.w
;
277 chans
= swizzle
->type
->vector_elements
;
279 deref_var
= (*ir
)->as_dereference_variable();
287 chans
= deref_var
->type
->vector_elements
;
290 if (this->in_assignee
)
293 ir_variable
*var
= deref_var
->var
;
295 /* Try to find ACP entries covering swizzle_chan[], hoping they're
296 * the same source variable.
298 hash_entry
*ht_entry
= _mesa_hash_table_search(lhs_ht
, var
);
300 exec_list
*ht_list
= (exec_list
*) ht_entry
->data
;
301 foreach_in_list(acp_entry
, entry
, ht_list
) {
302 for (int c
= 0; c
< chans
; c
++) {
303 if (entry
->write_mask
& (1 << swizzle_chan
[c
])) {
304 source
[c
] = entry
->rhs
;
305 source_chan
[c
] = entry
->swizzle
[swizzle_chan
[c
]];
307 if (source_chan
[c
] != swizzle_chan
[c
])
308 noop_swizzle
= false;
314 /* Make sure all channels are copying from the same source variable. */
317 for (int c
= 1; c
< chans
; c
++) {
318 if (source
[c
] != source
[0])
323 shader_mem_ctx
= ralloc_parent(deref_var
);
325 /* Don't pointlessly replace the rvalue with itself (or a noop swizzle
326 * of itself, which would just be deleted by opt_noop_swizzle).
328 if (source
[0] == var
&& noop_swizzle
)
332 printf("Copy propagation from:\n");
336 deref_var
= new(shader_mem_ctx
) ir_dereference_variable(source
[0]);
337 *ir
= new(shader_mem_ctx
) ir_swizzle(deref_var
,
354 ir_copy_propagation_elements_visitor::visit_enter(ir_call
*ir
)
356 /* Do copy propagation on call parameters, but skip any out params */
357 foreach_two_lists(formal_node
, &ir
->callee
->parameters
,
358 actual_node
, &ir
->actual_parameters
) {
359 ir_variable
*sig_param
= (ir_variable
*) formal_node
;
360 ir_rvalue
*ir
= (ir_rvalue
*) actual_node
;
361 if (sig_param
->data
.mode
!= ir_var_function_out
362 && sig_param
->data
.mode
!= ir_var_function_inout
) {
367 /* Since we're unlinked, we don't (necessarily) know the side effects of
368 * this call. So kill all copies.
370 _mesa_hash_table_clear(lhs_ht
, NULL
);
371 _mesa_hash_table_clear(rhs_ht
, NULL
);
373 this->killed_all
= true;
375 return visit_continue_with_parent
;
379 ir_copy_propagation_elements_visitor::handle_if_block(exec_list
*instructions
)
381 exec_list
*orig_kills
= this->kills
;
382 bool orig_killed_all
= this->killed_all
;
384 hash_table
*orig_lhs_ht
= lhs_ht
;
385 hash_table
*orig_rhs_ht
= rhs_ht
;
387 this->kills
= new(mem_ctx
) exec_list
;
388 this->killed_all
= false;
392 /* Populate the initial acp with a copy of the original */
393 populate_acp(orig_lhs_ht
, orig_rhs_ht
);
395 visit_list_elements(this, instructions
);
397 if (this->killed_all
) {
398 _mesa_hash_table_clear(orig_lhs_ht
, NULL
);
399 _mesa_hash_table_clear(orig_rhs_ht
, NULL
);
402 exec_list
*new_kills
= this->kills
;
403 this->kills
= orig_kills
;
404 this->killed_all
= this->killed_all
|| orig_killed_all
;
408 lhs_ht
= orig_lhs_ht
;
409 rhs_ht
= orig_rhs_ht
;
411 /* Move the new kills into the parent block's list, removing them
412 * from the parent's ACP list in the process.
414 foreach_in_list_safe(kill_entry
, k
, new_kills
) {
418 ralloc_free(new_kills
);
422 ir_copy_propagation_elements_visitor::visit_enter(ir_if
*ir
)
424 ir
->condition
->accept(this);
426 handle_if_block(&ir
->then_instructions
);
427 handle_if_block(&ir
->else_instructions
);
429 /* handle_if_block() already descended into the children. */
430 return visit_continue_with_parent
;
434 ir_copy_propagation_elements_visitor::handle_loop(ir_loop
*ir
, bool keep_acp
)
436 exec_list
*orig_kills
= this->kills
;
437 bool orig_killed_all
= this->killed_all
;
439 hash_table
*orig_lhs_ht
= lhs_ht
;
440 hash_table
*orig_rhs_ht
= rhs_ht
;
442 /* FINISHME: For now, the initial acp for loops is totally empty.
443 * We could go through once, then go through again with the acp
444 * cloned minus the killed entries after the first run through.
446 this->kills
= new(mem_ctx
) exec_list
;
447 this->killed_all
= false;
452 /* Populate the initial acp with a copy of the original */
453 populate_acp(orig_lhs_ht
, orig_rhs_ht
);
456 visit_list_elements(this, &ir
->body_instructions
);
458 if (this->killed_all
) {
459 _mesa_hash_table_clear(orig_lhs_ht
, NULL
);
460 _mesa_hash_table_clear(orig_rhs_ht
, NULL
);
463 exec_list
*new_kills
= this->kills
;
464 this->kills
= orig_kills
;
465 this->killed_all
= this->killed_all
|| orig_killed_all
;
469 lhs_ht
= orig_lhs_ht
;
470 rhs_ht
= orig_rhs_ht
;
472 foreach_in_list_safe(kill_entry
, k
, new_kills
) {
476 ralloc_free(new_kills
);
480 ir_copy_propagation_elements_visitor::visit_enter(ir_loop
*ir
)
482 handle_loop(ir
, false);
483 handle_loop(ir
, true);
485 /* already descended into the children. */
486 return visit_continue_with_parent
;
489 /* Remove any entries currently in the ACP for this kill. */
491 ir_copy_propagation_elements_visitor::kill(kill_entry
*k
)
493 /* removal of lhs entries */
494 hash_entry
*ht_entry
= _mesa_hash_table_search(lhs_ht
, k
->var
);
496 exec_list
*lhs_list
= (exec_list
*) ht_entry
->data
;
497 foreach_in_list_safe(acp_entry
, entry
, lhs_list
) {
498 entry
->write_mask
= entry
->write_mask
& ~k
->write_mask
;
499 if (entry
->write_mask
== 0) {
506 /* removal of rhs entries */
507 ht_entry
= _mesa_hash_table_search(rhs_ht
, k
->var
);
509 exec_list
*rhs_list
= (exec_list
*) ht_entry
->data
;
512 while ((ref
= (acp_ref
*) rhs_list
->pop_head()) != NULL
) {
513 acp_entry
*entry
= ref
->entry
;
515 /* If entry is still in a list (not already removed by lhs entry
516 * removal above), remove it.
518 if (entry
->prev
|| entry
->next
)
523 /* If we were on a list, remove ourselves before inserting */
527 ralloc_steal(this->kills
, k
);
528 this->kills
->push_tail(k
);
532 * Adds directly-copied channels between vector variables to the available
533 * copy propagation list.
536 ir_copy_propagation_elements_visitor::add_copy(ir_assignment
*ir
)
539 int orig_swizzle
[4] = {0, 1, 2, 3};
545 ir_dereference_variable
*lhs
= ir
->lhs
->as_dereference_variable();
546 if (!lhs
|| !(lhs
->type
->is_scalar() || lhs
->type
->is_vector()))
549 ir_dereference_variable
*rhs
= ir
->rhs
->as_dereference_variable();
551 ir_swizzle
*swiz
= ir
->rhs
->as_swizzle();
555 rhs
= swiz
->val
->as_dereference_variable();
559 orig_swizzle
[0] = swiz
->mask
.x
;
560 orig_swizzle
[1] = swiz
->mask
.y
;
561 orig_swizzle
[2] = swiz
->mask
.z
;
562 orig_swizzle
[3] = swiz
->mask
.w
;
565 /* Move the swizzle channels out to the positions they match in the
566 * destination. We don't want to have to rewrite the swizzle[]
567 * array every time we clear a bit of the write_mask.
570 for (int i
= 0; i
< 4; i
++) {
571 if (ir
->write_mask
& (1 << i
))
572 swizzle
[i
] = orig_swizzle
[j
++];
575 int write_mask
= ir
->write_mask
;
576 if (lhs
->var
== rhs
->var
) {
577 /* If this is a copy from the variable to itself, then we need
578 * to be sure not to include the updated channels from this
579 * instruction in the set of new source channels to be
580 * copy-propagated from.
582 for (int i
= 0; i
< 4; i
++) {
583 if (ir
->write_mask
& (1 << orig_swizzle
[i
]))
584 write_mask
&= ~(1 << i
);
588 if (lhs
->var
->data
.precise
!= rhs
->var
->data
.precise
)
591 entry
= new(this->mem_ctx
) acp_entry(lhs
->var
, rhs
->var
, write_mask
,
594 /* lhs hash, hash of lhs -> acp_entry lists */
595 hash_entry
*ht_entry
= _mesa_hash_table_search(lhs_ht
, lhs
->var
);
597 exec_list
*lhs_list
= (exec_list
*) ht_entry
->data
;
598 lhs_list
->push_tail(entry
);
600 exec_list
*lhs_list
= new(mem_ctx
) exec_list
;
601 lhs_list
->push_tail(entry
);
602 _mesa_hash_table_insert(lhs_ht
, lhs
->var
, lhs_list
);
605 /* rhs hash, hash of rhs -> acp_entry pointers to lhs lists */
606 ht_entry
= _mesa_hash_table_search(rhs_ht
, rhs
->var
);
608 exec_list
*rhs_list
= (exec_list
*) ht_entry
->data
;
609 rhs_list
->push_tail(&entry
->rhs_node
);
611 exec_list
*rhs_list
= new(mem_ctx
) exec_list
;
612 rhs_list
->push_tail(&entry
->rhs_node
);
613 _mesa_hash_table_insert(rhs_ht
, rhs
->var
, rhs_list
);
618 do_copy_propagation_elements(exec_list
*instructions
)
620 ir_copy_propagation_elements_visitor v
;
622 visit_list_elements(&v
, instructions
);