2 * Copyright © 2014 Intel Corporation
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
24 * Connor Abbott (cwabbott0@gmail.com)
28 #include "nir_control_flow_private.h"
31 * \name Control flow modification
33 * These functions modify the control flow tree while keeping the control flow
34 * graph up-to-date. The invariants respected are:
35 * 1. Each then statement, else statement, or loop body must have at least one
37 * 2. Each if-statement and loop must have one basic block before it and one
39 * 3. Two basic blocks cannot be directly next to each other.
40 * 4. If a basic block has a jump instruction, there must be only one and it
41 * must be at the end of the block.
43 * The purpose of the second one is so that we have places to insert code during
44 * GCM, as well as eliminating the possibility of critical edges.
49 block_add_pred(nir_block
*block
, nir_block
*pred
)
51 _mesa_set_add(block
->predecessors
, pred
);
55 block_remove_pred(nir_block
*block
, nir_block
*pred
)
57 struct set_entry
*entry
= _mesa_set_search(block
->predecessors
, pred
);
61 _mesa_set_remove(block
->predecessors
, entry
);
65 link_blocks(nir_block
*pred
, nir_block
*succ1
, nir_block
*succ2
)
67 pred
->successors
[0] = succ1
;
69 block_add_pred(succ1
, pred
);
71 pred
->successors
[1] = succ2
;
73 block_add_pred(succ2
, pred
);
77 unlink_blocks(nir_block
*pred
, nir_block
*succ
)
79 if (pred
->successors
[0] == succ
) {
80 pred
->successors
[0] = pred
->successors
[1];
81 pred
->successors
[1] = NULL
;
83 assert(pred
->successors
[1] == succ
);
84 pred
->successors
[1] = NULL
;
87 block_remove_pred(succ
, pred
);
91 unlink_block_successors(nir_block
*block
)
93 if (block
->successors
[1] != NULL
)
94 unlink_blocks(block
, block
->successors
[1]);
95 if (block
->successors
[0] != NULL
)
96 unlink_blocks(block
, block
->successors
[0]);
100 link_non_block_to_block(nir_cf_node
*node
, nir_block
*block
)
102 if (node
->type
== nir_cf_node_if
) {
104 * We're trying to link an if to a block after it; this just means linking
105 * the last block of the then and else branches.
108 nir_if
*if_stmt
= nir_cf_node_as_if(node
);
110 nir_block
*last_then_block
= nir_if_last_then_block(if_stmt
);
111 nir_block
*last_else_block
= nir_if_last_else_block(if_stmt
);
113 if (!nir_block_ends_in_jump(last_then_block
)) {
114 unlink_block_successors(last_then_block
);
115 link_blocks(last_then_block
, block
, NULL
);
118 if (!nir_block_ends_in_jump(last_else_block
)) {
119 unlink_block_successors(last_else_block
);
120 link_blocks(last_else_block
, block
, NULL
);
123 assert(node
->type
== nir_cf_node_loop
);
128 link_block_to_non_block(nir_block
*block
, nir_cf_node
*node
)
130 if (node
->type
== nir_cf_node_if
) {
132 * We're trying to link a block to an if after it; this just means linking
133 * the block to the first block of the then and else branches.
136 nir_if
*if_stmt
= nir_cf_node_as_if(node
);
138 nir_block
*first_then_block
= nir_if_first_then_block(if_stmt
);
139 nir_block
*first_else_block
= nir_if_first_else_block(if_stmt
);
141 unlink_block_successors(block
);
142 link_blocks(block
, first_then_block
, first_else_block
);
143 } else if (node
->type
== nir_cf_node_loop
) {
145 * For similar reasons as the corresponding case in
146 * link_non_block_to_block(), don't worry about if the loop header has
147 * any predecessors that need to be unlinked.
150 nir_loop
*loop
= nir_cf_node_as_loop(node
);
152 nir_block
*loop_header_block
= nir_loop_first_block(loop
);
154 unlink_block_successors(block
);
155 link_blocks(block
, loop_header_block
, NULL
);
161 * Replace a block's successor with a different one.
164 replace_successor(nir_block
*block
, nir_block
*old_succ
, nir_block
*new_succ
)
166 if (block
->successors
[0] == old_succ
) {
167 block
->successors
[0] = new_succ
;
169 assert(block
->successors
[1] == old_succ
);
170 block
->successors
[1] = new_succ
;
173 block_remove_pred(old_succ
, block
);
174 block_add_pred(new_succ
, block
);
178 * Takes a basic block and inserts a new empty basic block before it, making its
179 * predecessors point to the new block. This essentially splits the block into
180 * an empty header and a body so that another non-block CF node can be inserted
181 * between the two. Note that this does *not* link the two basic blocks, so
182 * some kind of cleanup *must* be performed after this call.
186 split_block_beginning(nir_block
*block
)
188 nir_block
*new_block
= nir_block_create(ralloc_parent(block
));
189 new_block
->cf_node
.parent
= block
->cf_node
.parent
;
190 exec_node_insert_node_before(&block
->cf_node
.node
, &new_block
->cf_node
.node
);
192 set_foreach(block
->predecessors
, entry
) {
193 nir_block
*pred
= (nir_block
*) entry
->key
;
194 replace_successor(pred
, block
, new_block
);
197 /* Any phi nodes must stay part of the new block, or else their
198 * sources will be messed up.
200 nir_foreach_instr_safe(instr
, block
) {
201 if (instr
->type
!= nir_instr_type_phi
)
204 exec_node_remove(&instr
->node
);
205 instr
->block
= new_block
;
206 exec_list_push_tail(&new_block
->instr_list
, &instr
->node
);
213 rewrite_phi_preds(nir_block
*block
, nir_block
*old_pred
, nir_block
*new_pred
)
215 nir_foreach_instr_safe(instr
, block
) {
216 if (instr
->type
!= nir_instr_type_phi
)
219 nir_phi_instr
*phi
= nir_instr_as_phi(instr
);
220 nir_foreach_phi_src(src
, phi
) {
221 if (src
->pred
== old_pred
) {
222 src
->pred
= new_pred
;
230 insert_phi_undef(nir_block
*block
, nir_block
*pred
)
232 nir_function_impl
*impl
= nir_cf_node_get_function(&block
->cf_node
);
233 nir_foreach_instr(instr
, block
) {
234 if (instr
->type
!= nir_instr_type_phi
)
237 nir_phi_instr
*phi
= nir_instr_as_phi(instr
);
238 nir_ssa_undef_instr
*undef
=
239 nir_ssa_undef_instr_create(ralloc_parent(phi
),
240 phi
->dest
.ssa
.num_components
,
241 phi
->dest
.ssa
.bit_size
);
242 nir_instr_insert_before_cf_list(&impl
->body
, &undef
->instr
);
243 nir_phi_src
*src
= ralloc(phi
, nir_phi_src
);
245 src
->src
.parent_instr
= &phi
->instr
;
246 src
->src
.is_ssa
= true;
247 src
->src
.ssa
= &undef
->def
;
249 list_addtail(&src
->src
.use_link
, &undef
->def
.uses
);
251 exec_list_push_tail(&phi
->srcs
, &src
->node
);
256 * Moves the successors of source to the successors of dest, leaving both
257 * successors of source NULL.
261 move_successors(nir_block
*source
, nir_block
*dest
)
263 nir_block
*succ1
= source
->successors
[0];
264 nir_block
*succ2
= source
->successors
[1];
267 unlink_blocks(source
, succ1
);
268 rewrite_phi_preds(succ1
, source
, dest
);
272 unlink_blocks(source
, succ2
);
273 rewrite_phi_preds(succ2
, source
, dest
);
276 unlink_block_successors(dest
);
277 link_blocks(dest
, succ1
, succ2
);
280 /* Given a basic block with no successors that has been inserted into the
281 * control flow tree, gives it the successors it would normally have assuming
282 * it doesn't end in a jump instruction. Also inserts phi sources with undefs
286 block_add_normal_succs(nir_block
*block
)
288 if (exec_node_is_tail_sentinel(block
->cf_node
.node
.next
)) {
289 nir_cf_node
*parent
= block
->cf_node
.parent
;
290 if (parent
->type
== nir_cf_node_if
) {
291 nir_cf_node
*next
= nir_cf_node_next(parent
);
292 nir_block
*next_block
= nir_cf_node_as_block(next
);
294 link_blocks(block
, next_block
, NULL
);
295 } else if (parent
->type
== nir_cf_node_loop
) {
296 nir_loop
*loop
= nir_cf_node_as_loop(parent
);
298 nir_block
*head_block
= nir_loop_first_block(loop
);
300 link_blocks(block
, head_block
, NULL
);
301 insert_phi_undef(head_block
, block
);
303 nir_function_impl
*impl
= nir_cf_node_as_function(parent
);
304 link_blocks(block
, impl
->end_block
, NULL
);
307 nir_cf_node
*next
= nir_cf_node_next(&block
->cf_node
);
308 if (next
->type
== nir_cf_node_if
) {
309 nir_if
*next_if
= nir_cf_node_as_if(next
);
311 nir_block
*first_then_block
= nir_if_first_then_block(next_if
);
312 nir_block
*first_else_block
= nir_if_first_else_block(next_if
);
314 link_blocks(block
, first_then_block
, first_else_block
);
315 } else if (next
->type
== nir_cf_node_loop
) {
316 nir_loop
*next_loop
= nir_cf_node_as_loop(next
);
318 nir_block
*first_block
= nir_loop_first_block(next_loop
);
320 link_blocks(block
, first_block
, NULL
);
321 insert_phi_undef(first_block
, block
);
327 split_block_end(nir_block
*block
)
329 nir_block
*new_block
= nir_block_create(ralloc_parent(block
));
330 new_block
->cf_node
.parent
= block
->cf_node
.parent
;
331 exec_node_insert_after(&block
->cf_node
.node
, &new_block
->cf_node
.node
);
333 if (nir_block_ends_in_jump(block
)) {
334 /* Figure out what successor block would've had if it didn't have a jump
335 * instruction, and make new_block have that successor.
337 block_add_normal_succs(new_block
);
339 move_successors(block
, new_block
);
346 split_block_before_instr(nir_instr
*instr
)
348 assert(instr
->type
!= nir_instr_type_phi
);
349 nir_block
*new_block
= split_block_beginning(instr
->block
);
351 nir_foreach_instr_safe(cur_instr
, instr
->block
) {
352 if (cur_instr
== instr
)
355 exec_node_remove(&cur_instr
->node
);
356 cur_instr
->block
= new_block
;
357 exec_list_push_tail(&new_block
->instr_list
, &cur_instr
->node
);
363 /* Splits a basic block at the point specified by the cursor. The "before" and
364 * "after" arguments are filled out with the blocks resulting from the split
365 * if non-NULL. Note that the "beginning" of the block is actually interpreted
366 * as before the first non-phi instruction, and it's illegal to split a block
367 * before a phi instruction.
371 split_block_cursor(nir_cursor cursor
,
372 nir_block
**_before
, nir_block
**_after
)
374 nir_block
*before
, *after
;
375 switch (cursor
.option
) {
376 case nir_cursor_before_block
:
377 after
= cursor
.block
;
378 before
= split_block_beginning(cursor
.block
);
381 case nir_cursor_after_block
:
382 before
= cursor
.block
;
383 after
= split_block_end(cursor
.block
);
386 case nir_cursor_before_instr
:
387 after
= cursor
.instr
->block
;
388 before
= split_block_before_instr(cursor
.instr
);
391 case nir_cursor_after_instr
:
392 /* We lower this to split_block_before_instr() so that we can keep the
393 * after-a-jump-instr case contained to split_block_end().
395 if (nir_instr_is_last(cursor
.instr
)) {
396 before
= cursor
.instr
->block
;
397 after
= split_block_end(cursor
.instr
->block
);
399 after
= cursor
.instr
->block
;
400 before
= split_block_before_instr(nir_instr_next(cursor
.instr
));
405 unreachable("not reached");
415 * Inserts a non-basic block between two basic blocks and links them together.
419 insert_non_block(nir_block
*before
, nir_cf_node
*node
, nir_block
*after
)
421 node
->parent
= before
->cf_node
.parent
;
422 exec_node_insert_after(&before
->cf_node
.node
, &node
->node
);
423 link_block_to_non_block(before
, node
);
424 link_non_block_to_block(node
, after
);
427 /* walk up the control flow tree to find the innermost enclosed loop */
429 nearest_loop(nir_cf_node
*node
)
431 while (node
->type
!= nir_cf_node_loop
) {
435 return nir_cf_node_as_loop(node
);
439 remove_phi_src(nir_block
*block
, nir_block
*pred
)
441 nir_foreach_instr(instr
, block
) {
442 if (instr
->type
!= nir_instr_type_phi
)
445 nir_phi_instr
*phi
= nir_instr_as_phi(instr
);
446 nir_foreach_phi_src_safe(src
, phi
) {
447 if (src
->pred
== pred
) {
448 list_del(&src
->src
.use_link
);
449 exec_node_remove(&src
->node
);
456 * update the CFG after a jump instruction has been added to the end of a block
460 nir_handle_add_jump(nir_block
*block
)
462 nir_instr
*instr
= nir_block_last_instr(block
);
463 nir_jump_instr
*jump_instr
= nir_instr_as_jump(instr
);
465 if (block
->successors
[0])
466 remove_phi_src(block
->successors
[0], block
);
467 if (block
->successors
[1])
468 remove_phi_src(block
->successors
[1], block
);
469 unlink_block_successors(block
);
471 nir_function_impl
*impl
= nir_cf_node_get_function(&block
->cf_node
);
472 nir_metadata_preserve(impl
, nir_metadata_none
);
474 switch (jump_instr
->type
) {
475 case nir_jump_return
:
476 link_blocks(block
, impl
->end_block
, NULL
);
479 case nir_jump_break
: {
480 nir_loop
*loop
= nearest_loop(&block
->cf_node
);
481 nir_cf_node
*after
= nir_cf_node_next(&loop
->cf_node
);
482 nir_block
*after_block
= nir_cf_node_as_block(after
);
483 link_blocks(block
, after_block
, NULL
);
487 case nir_jump_continue
: {
488 nir_loop
*loop
= nearest_loop(&block
->cf_node
);
489 nir_block
*first_block
= nir_loop_first_block(loop
);
490 link_blocks(block
, first_block
, NULL
);
495 link_blocks(block
, jump_instr
->target
, NULL
);
498 case nir_jump_goto_if
:
499 link_blocks(block
, jump_instr
->else_target
, jump_instr
->target
);
503 unreachable("Invalid jump type");
507 /* Removes the successor of a block with a jump. Note that the jump to be
508 * eliminated may be free-floating.
512 unlink_jump(nir_block
*block
, nir_jump_type type
, bool add_normal_successors
)
514 if (block
->successors
[0])
515 remove_phi_src(block
->successors
[0], block
);
516 if (block
->successors
[1])
517 remove_phi_src(block
->successors
[1], block
);
519 unlink_block_successors(block
);
520 if (add_normal_successors
)
521 block_add_normal_succs(block
);
525 nir_handle_remove_jump(nir_block
*block
, nir_jump_type type
)
527 unlink_jump(block
, type
, true);
529 nir_function_impl
*impl
= nir_cf_node_get_function(&block
->cf_node
);
530 nir_metadata_preserve(impl
, nir_metadata_none
);
534 update_if_uses(nir_cf_node
*node
)
536 if (node
->type
!= nir_cf_node_if
)
539 nir_if
*if_stmt
= nir_cf_node_as_if(node
);
541 if_stmt
->condition
.parent_if
= if_stmt
;
542 if (if_stmt
->condition
.is_ssa
) {
543 list_addtail(&if_stmt
->condition
.use_link
,
544 &if_stmt
->condition
.ssa
->if_uses
);
546 list_addtail(&if_stmt
->condition
.use_link
,
547 &if_stmt
->condition
.reg
.reg
->if_uses
);
552 * Stitch two basic blocks together into one. The aggregate must have the same
553 * predecessors as the first and the same successors as the second.
557 stitch_blocks(nir_block
*before
, nir_block
*after
)
560 * We move after into before, so we have to deal with up to 2 successors vs.
561 * possibly a large number of predecessors.
563 * TODO: special case when before is empty and after isn't?
566 if (nir_block_ends_in_jump(before
)) {
567 assert(exec_list_is_empty(&after
->instr_list
));
568 if (after
->successors
[0])
569 remove_phi_src(after
->successors
[0], after
);
570 if (after
->successors
[1])
571 remove_phi_src(after
->successors
[1], after
);
572 unlink_block_successors(after
);
573 exec_node_remove(&after
->cf_node
.node
);
575 move_successors(after
, before
);
577 foreach_list_typed(nir_instr
, instr
, node
, &after
->instr_list
) {
578 instr
->block
= before
;
581 exec_list_append(&before
->instr_list
, &after
->instr_list
);
582 exec_node_remove(&after
->cf_node
.node
);
587 nir_cf_node_insert(nir_cursor cursor
, nir_cf_node
*node
)
589 nir_block
*before
, *after
;
591 split_block_cursor(cursor
, &before
, &after
);
593 if (node
->type
== nir_cf_node_block
) {
594 nir_block
*block
= nir_cf_node_as_block(node
);
595 exec_node_insert_after(&before
->cf_node
.node
, &block
->cf_node
.node
);
596 block
->cf_node
.parent
= before
->cf_node
.parent
;
597 /* stitch_blocks() assumes that any block that ends with a jump has
598 * already been setup with the correct successors, so we need to set
599 * up jumps here as the block is being inserted.
601 if (nir_block_ends_in_jump(block
))
602 nir_handle_add_jump(block
);
604 stitch_blocks(block
, after
);
605 stitch_blocks(before
, block
);
607 update_if_uses(node
);
608 insert_non_block(before
, node
, after
);
613 replace_ssa_def_uses(nir_ssa_def
*def
, void *void_impl
)
615 nir_function_impl
*impl
= void_impl
;
616 void *mem_ctx
= ralloc_parent(impl
);
618 nir_ssa_undef_instr
*undef
=
619 nir_ssa_undef_instr_create(mem_ctx
, def
->num_components
,
621 nir_instr_insert_before_cf_list(&impl
->body
, &undef
->instr
);
622 nir_ssa_def_rewrite_uses(def
, nir_src_for_ssa(&undef
->def
));
627 cleanup_cf_node(nir_cf_node
*node
, nir_function_impl
*impl
)
629 switch (node
->type
) {
630 case nir_cf_node_block
: {
631 nir_block
*block
= nir_cf_node_as_block(node
);
632 /* We need to walk the instructions and clean up defs/uses */
633 nir_foreach_instr_safe(instr
, block
) {
634 if (instr
->type
== nir_instr_type_jump
) {
635 nir_jump_instr
*jump
= nir_instr_as_jump(instr
);
636 unlink_jump(block
, jump
->type
, false);
637 if (jump
->type
== nir_jump_goto_if
)
638 nir_instr_rewrite_src(instr
, &jump
->condition
, NIR_SRC_INIT
);
640 nir_foreach_ssa_def(instr
, replace_ssa_def_uses
, impl
);
641 nir_instr_remove(instr
);
647 case nir_cf_node_if
: {
648 nir_if
*if_stmt
= nir_cf_node_as_if(node
);
649 foreach_list_typed(nir_cf_node
, child
, node
, &if_stmt
->then_list
)
650 cleanup_cf_node(child
, impl
);
651 foreach_list_typed(nir_cf_node
, child
, node
, &if_stmt
->else_list
)
652 cleanup_cf_node(child
, impl
);
654 list_del(&if_stmt
->condition
.use_link
);
658 case nir_cf_node_loop
: {
659 nir_loop
*loop
= nir_cf_node_as_loop(node
);
660 foreach_list_typed(nir_cf_node
, child
, node
, &loop
->body
)
661 cleanup_cf_node(child
, impl
);
664 case nir_cf_node_function
: {
665 nir_function_impl
*impl
= nir_cf_node_as_function(node
);
666 foreach_list_typed(nir_cf_node
, child
, node
, &impl
->body
)
667 cleanup_cf_node(child
, impl
);
671 unreachable("Invalid CF node type");
676 nir_cf_extract(nir_cf_list
*extracted
, nir_cursor begin
, nir_cursor end
)
678 nir_block
*block_begin
, *block_end
, *block_before
, *block_after
;
680 if (nir_cursors_equal(begin
, end
)) {
681 exec_list_make_empty(&extracted
->list
);
682 extracted
->impl
= NULL
; /* we shouldn't need this */
686 /* In the case where begin points to an instruction in some basic block and
687 * end points to the end of the same basic block, we rely on the fact that
688 * splitting on an instruction moves earlier instructions into a new basic
689 * block. If the later instructions were moved instead, then the end cursor
690 * would be pointing to the same place that begin used to point to, which
691 * is obviously not what we want.
693 split_block_cursor(begin
, &block_before
, &block_begin
);
694 split_block_cursor(end
, &block_end
, &block_after
);
696 extracted
->impl
= nir_cf_node_get_function(&block_begin
->cf_node
);
697 exec_list_make_empty(&extracted
->list
);
699 /* Dominance and other block-related information is toast. */
700 nir_metadata_preserve(extracted
->impl
, nir_metadata_none
);
702 nir_cf_node
*cf_node
= &block_begin
->cf_node
;
703 nir_cf_node
*cf_node_end
= &block_end
->cf_node
;
705 nir_cf_node
*next
= nir_cf_node_next(cf_node
);
707 exec_node_remove(&cf_node
->node
);
708 cf_node
->parent
= NULL
;
709 exec_list_push_tail(&extracted
->list
, &cf_node
->node
);
711 if (cf_node
== cf_node_end
)
717 stitch_blocks(block_before
, block_after
);
721 nir_cf_reinsert(nir_cf_list
*cf_list
, nir_cursor cursor
)
723 nir_block
*before
, *after
;
725 if (exec_list_is_empty(&cf_list
->list
))
728 split_block_cursor(cursor
, &before
, &after
);
730 foreach_list_typed_safe(nir_cf_node
, node
, node
, &cf_list
->list
) {
731 exec_node_remove(&node
->node
);
732 node
->parent
= before
->cf_node
.parent
;
733 exec_node_insert_node_before(&after
->cf_node
.node
, &node
->node
);
736 stitch_blocks(before
,
737 nir_cf_node_as_block(nir_cf_node_next(&before
->cf_node
)));
738 stitch_blocks(nir_cf_node_as_block(nir_cf_node_prev(&after
->cf_node
)),
743 nir_cf_delete(nir_cf_list
*cf_list
)
745 foreach_list_typed(nir_cf_node
, node
, node
, &cf_list
->list
) {
746 cleanup_cf_node(node
, cf_list
->impl
);