* defaults.h (FRAME_GROWS_DOWNWARD): Define to 0 if not defined.
[official-gcc.git] / gcc / tree-if-conv.c
blob710fbb6e4f9659980732f2a929ea541ddd099de7
1 /* If-conversion for vectorizer.
2 Copyright (C) 2004, 2005 Free Software Foundation, Inc.
3 Contributed by Devang Patel <dpatel@apple.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
20 02110-1301, USA. */
22 /* This pass implements tree level if-conversion transformation of loops.
23 Initial goal is to help vectorizer vectorize loops with conditions.
25 A short description of if-conversion:
27 o Decide if a loop is if-convertible or not.
28 o Walk all loop basic blocks in breadth first order (BFS order).
29 o Remove conditional statements (at the end of basic block)
30 and propagate condition into destination basic blocks'
31 predicate list.
32 o Replace modify expression with conditional modify expression
33 using current basic block's condition.
34 o Merge all basic blocks
35 o Replace phi nodes with conditional modify expr
36 o Merge all basic blocks into header
38 Sample transformation:
40 INPUT
41 -----
43 # i_23 = PHI <0(0), i_18(10)>;
44 <L0>:;
45 j_15 = A[i_23];
46 if (j_15 > 41) goto <L1>; else goto <L17>;
48 <L17>:;
49 goto <bb 3> (<L3>);
51 <L1>:;
53 # iftmp.2_4 = PHI <0(8), 42(2)>;
54 <L3>:;
55 A[i_23] = iftmp.2_4;
56 i_18 = i_23 + 1;
57 if (i_18 <= 15) goto <L19>; else goto <L18>;
59 <L19>:;
60 goto <bb 1> (<L0>);
62 <L18>:;
64 OUTPUT
65 ------
67 # i_23 = PHI <0(0), i_18(10)>;
68 <L0>:;
69 j_15 = A[i_23];
71 <L3>:;
72 iftmp.2_4 = j_15 > 41 ? 42 : 0;
73 A[i_23] = iftmp.2_4;
74 i_18 = i_23 + 1;
75 if (i_18 <= 15) goto <L19>; else goto <L18>;
77 <L19>:;
78 goto <bb 1> (<L0>);
80 <L18>:;
83 #include "config.h"
84 #include "system.h"
85 #include "coretypes.h"
86 #include "tm.h"
87 #include "tree.h"
88 #include "c-common.h"
89 #include "flags.h"
90 #include "timevar.h"
91 #include "varray.h"
92 #include "rtl.h"
93 #include "basic-block.h"
94 #include "diagnostic.h"
95 #include "tree-flow.h"
96 #include "tree-dump.h"
97 #include "cfgloop.h"
98 #include "tree-chrec.h"
99 #include "tree-data-ref.h"
100 #include "tree-scalar-evolution.h"
101 #include "tree-pass.h"
102 #include "target.h"
104 /* local function prototypes */
105 static void main_tree_if_conversion (void);
106 static tree tree_if_convert_stmt (struct loop *loop, tree, tree,
107 block_stmt_iterator *);
108 static void tree_if_convert_cond_expr (struct loop *, tree, tree,
109 block_stmt_iterator *);
110 static bool if_convertible_phi_p (struct loop *, basic_block, tree);
111 static bool if_convertible_modify_expr_p (struct loop *, basic_block, tree);
112 static bool if_convertible_stmt_p (struct loop *, basic_block, tree);
113 static bool if_convertible_bb_p (struct loop *, basic_block, bool);
114 static bool if_convertible_loop_p (struct loop *, bool);
115 static void add_to_predicate_list (basic_block, tree);
116 static tree add_to_dst_predicate_list (struct loop * loop, basic_block, tree, tree,
117 block_stmt_iterator *);
118 static void clean_predicate_lists (struct loop *loop);
119 static basic_block find_phi_replacement_condition (struct loop *loop,
120 basic_block, tree *,
121 block_stmt_iterator *);
122 static void replace_phi_with_cond_modify_expr (tree, tree, basic_block,
123 block_stmt_iterator *);
124 static void process_phi_nodes (struct loop *);
125 static void combine_blocks (struct loop *);
126 static tree ifc_temp_var (tree, tree);
127 static bool pred_blocks_visited_p (basic_block, bitmap *);
128 static basic_block * get_loop_body_in_if_conv_order (const struct loop *loop);
129 static bool bb_with_exit_edge_p (struct loop *, basic_block);
131 /* List of basic blocks in if-conversion-suitable order. */
132 static basic_block *ifc_bbs;
134 /* Main entry point.
135 Apply if-conversion to the LOOP. Return true if successful otherwise return
136 false. If false is returned then loop remains unchanged.
137 FOR_VECTORIZER is a boolean flag. It indicates whether if-conversion is used
138 for vectorizer or not. If it is used for vectorizer, additional checks are
139 used. (Vectorization checks are not yet implemented). */
141 static bool
142 tree_if_conversion (struct loop *loop, bool for_vectorizer)
144 basic_block bb;
145 block_stmt_iterator itr;
146 tree cond;
147 unsigned int i;
149 ifc_bbs = NULL;
151 /* if-conversion is not appropriate for all loops. First, check if loop is
152 if-convertible or not. */
153 if (!if_convertible_loop_p (loop, for_vectorizer))
155 if (dump_file && (dump_flags & TDF_DETAILS))
156 fprintf (dump_file,"-------------------------\n");
157 if (ifc_bbs)
159 free (ifc_bbs);
160 ifc_bbs = NULL;
162 free_dominance_info (CDI_POST_DOMINATORS);
163 return false;
166 cond = NULL_TREE;
168 /* Do actual work now. */
169 for (i = 0; i < loop->num_nodes; i++)
171 bb = ifc_bbs [i];
173 /* Update condition using predicate list. */
174 cond = bb->aux;
176 /* Process all statements in this basic block.
177 Remove conditional expression, if any, and annotate
178 destination basic block(s) appropriately. */
179 for (itr = bsi_start (bb); !bsi_end_p (itr); /* empty */)
181 tree t = bsi_stmt (itr);
182 cond = tree_if_convert_stmt (loop, t, cond, &itr);
183 if (!bsi_end_p (itr))
184 bsi_next (&itr);
187 /* If current bb has only one successor, then consider it as an
188 unconditional goto. */
189 if (single_succ_p (bb))
191 basic_block bb_n = single_succ (bb);
192 if (cond != NULL_TREE)
193 add_to_predicate_list (bb_n, cond);
194 cond = NULL_TREE;
198 /* Now, all statements are if-converted and basic blocks are
199 annotated appropriately. Combine all basic block into one huge
200 basic block. */
201 combine_blocks (loop);
203 /* clean up */
204 clean_predicate_lists (loop);
205 free (ifc_bbs);
206 ifc_bbs = NULL;
208 return true;
211 /* if-convert stmt T which is part of LOOP.
212 If T is a MODIFY_EXPR than it is converted into conditional modify
213 expression using COND. For conditional expressions, add condition in the
214 destination basic block's predicate list and remove conditional
215 expression itself. BSI is the iterator used to traverse statements of
216 loop. It is used here when it is required to delete current statement. */
218 static tree
219 tree_if_convert_stmt (struct loop * loop, tree t, tree cond,
220 block_stmt_iterator *bsi)
222 if (dump_file && (dump_flags & TDF_DETAILS))
224 fprintf (dump_file, "------if-convert stmt\n");
225 print_generic_stmt (dump_file, t, TDF_SLIM);
226 print_generic_stmt (dump_file, cond, TDF_SLIM);
229 switch (TREE_CODE (t))
231 /* Labels are harmless here. */
232 case LABEL_EXPR:
233 break;
235 case MODIFY_EXPR:
236 /* This modify_expr is killing previous value of LHS. Appropriate value will
237 be selected by PHI node based on condition. It is possible that before
238 this transformation, PHI nodes was selecting default value and now it will
239 use this new value. This is OK because it does not change validity the
240 program. */
241 break;
243 case COND_EXPR:
244 /* Update destination blocks' predicate list and remove this
245 condition expression. */
246 tree_if_convert_cond_expr (loop, t, cond, bsi);
247 cond = NULL_TREE;
248 break;
250 default:
251 gcc_unreachable ();
253 return cond;
256 /* STMT is COND_EXPR. Update two destination's predicate list.
257 Remove COND_EXPR, if it is not the loop exit condition. Otherwise
258 update loop exit condition appropriately. BSI is the iterator
259 used to traverse statement list. STMT is part of loop LOOP. */
261 static void
262 tree_if_convert_cond_expr (struct loop *loop, tree stmt, tree cond,
263 block_stmt_iterator *bsi)
265 tree c, c2;
266 edge true_edge, false_edge;
268 gcc_assert (TREE_CODE (stmt) == COND_EXPR);
270 c = COND_EXPR_COND (stmt);
272 extract_true_false_edges_from_block (bb_for_stmt (stmt),
273 &true_edge, &false_edge);
275 /* Add new condition into destination's predicate list. */
277 /* If 'c' is true then TRUE_EDGE is taken. */
278 add_to_dst_predicate_list (loop, true_edge->dest, cond,
279 unshare_expr (c), bsi);
281 /* If 'c' is false then FALSE_EDGE is taken. */
282 c2 = invert_truthvalue (unshare_expr (c));
283 add_to_dst_predicate_list (loop, false_edge->dest, cond, c2, bsi);
285 /* Now this conditional statement is redundant. Remove it.
286 But, do not remove exit condition! Update exit condition
287 using new condition. */
288 if (!bb_with_exit_edge_p (loop, bb_for_stmt (stmt)))
290 bsi_remove (bsi);
291 cond = NULL_TREE;
293 return;
296 /* Return true, iff PHI is if-convertible. PHI is part of loop LOOP
297 and it belongs to basic block BB.
298 PHI is not if-convertible
299 - if it has more than 2 arguments.
300 - Virtual PHI is immediately used in another PHI node. */
302 static bool
303 if_convertible_phi_p (struct loop *loop, basic_block bb, tree phi)
305 if (dump_file && (dump_flags & TDF_DETAILS))
307 fprintf (dump_file, "-------------------------\n");
308 print_generic_stmt (dump_file, phi, TDF_SLIM);
311 if (bb != loop->header && PHI_NUM_ARGS (phi) != 2)
313 if (dump_file && (dump_flags & TDF_DETAILS))
314 fprintf (dump_file, "More than two phi node args.\n");
315 return false;
318 if (!is_gimple_reg (SSA_NAME_VAR (PHI_RESULT (phi))))
320 imm_use_iterator imm_iter;
321 use_operand_p use_p;
322 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, PHI_RESULT (phi))
324 if (TREE_CODE (USE_STMT (use_p)) == PHI_NODE)
326 if (dump_file && (dump_flags & TDF_DETAILS))
327 fprintf (dump_file, "Difficult to handle this virtual phi.\n");
328 return false;
333 return true;
336 /* Return true, if M_EXPR is if-convertible.
337 MODIFY_EXPR is not if-convertible if,
338 - It is not movable.
339 - It could trap.
340 - LHS is not var decl.
341 MODIFY_EXPR is part of block BB, which is inside loop LOOP.
344 static bool
345 if_convertible_modify_expr_p (struct loop *loop, basic_block bb, tree m_expr)
347 if (dump_file && (dump_flags & TDF_DETAILS))
349 fprintf (dump_file, "-------------------------\n");
350 print_generic_stmt (dump_file, m_expr, TDF_SLIM);
353 /* Be conservative and do not handle immovable expressions. */
354 if (movement_possibility (m_expr) == MOVE_IMPOSSIBLE)
356 if (dump_file && (dump_flags & TDF_DETAILS))
357 fprintf (dump_file, "stmt is movable. Don't take risk\n");
358 return false;
361 /* See if it needs speculative loading or not. */
362 if (bb != loop->header
363 && tree_could_trap_p (TREE_OPERAND (m_expr, 1)))
365 if (dump_file && (dump_flags & TDF_DETAILS))
366 fprintf (dump_file, "tree could trap...\n");
367 return false;
370 if (TREE_CODE (TREE_OPERAND (m_expr, 1)) == CALL_EXPR)
372 if (dump_file && (dump_flags & TDF_DETAILS))
373 fprintf (dump_file, "CALL_EXPR \n");
374 return false;
377 if (TREE_CODE (TREE_OPERAND (m_expr, 0)) != SSA_NAME
378 && bb != loop->header
379 && !bb_with_exit_edge_p (loop, bb))
381 if (dump_file && (dump_flags & TDF_DETAILS))
383 fprintf (dump_file, "LHS is not var\n");
384 print_generic_stmt (dump_file, m_expr, TDF_SLIM);
386 return false;
390 return true;
393 /* Return true, iff STMT is if-convertible.
394 Statement is if-convertible if,
395 - It is if-convertible MODIFY_EXPR
396 - IT is LABEL_EXPR or COND_EXPR.
397 STMT is inside block BB, which is inside loop LOOP. */
399 static bool
400 if_convertible_stmt_p (struct loop *loop, basic_block bb, tree stmt)
402 switch (TREE_CODE (stmt))
404 case LABEL_EXPR:
405 break;
407 case MODIFY_EXPR:
409 if (!if_convertible_modify_expr_p (loop, bb, stmt))
410 return false;
411 break;
413 case COND_EXPR:
414 break;
416 default:
417 /* Don't know what to do with 'em so don't do anything. */
418 if (dump_file && (dump_flags & TDF_DETAILS))
420 fprintf (dump_file, "don't know what to do\n");
421 print_generic_stmt (dump_file, stmt, TDF_SLIM);
423 return false;
424 break;
427 return true;
430 /* Return true, iff BB is if-convertible.
431 Note: This routine does _not_ check basic block statements and phis.
432 Basic block is not if-convertible if,
433 - Basic block is non-empty and it is after exit block (in BFS order).
434 - Basic block is after exit block but before latch.
435 - Basic block edge(s) is not normal.
436 EXIT_BB_SEEN is true if basic block with exit edge is already seen.
437 BB is inside loop LOOP. */
439 static bool
440 if_convertible_bb_p (struct loop *loop, basic_block bb, bool exit_bb_seen)
442 edge e;
443 edge_iterator ei;
445 if (dump_file && (dump_flags & TDF_DETAILS))
446 fprintf (dump_file, "----------[%d]-------------\n", bb->index);
448 if (exit_bb_seen)
450 if (bb != loop->latch)
452 if (dump_file && (dump_flags & TDF_DETAILS))
453 fprintf (dump_file, "basic block after exit bb but before latch\n");
454 return false;
456 else if (!empty_block_p (bb))
458 if (dump_file && (dump_flags & TDF_DETAILS))
459 fprintf (dump_file, "non empty basic block after exit bb\n");
460 return false;
464 /* Be less adventurous and handle only normal edges. */
465 FOR_EACH_EDGE (e, ei, bb->succs)
466 if (e->flags &
467 (EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
469 if (dump_file && (dump_flags & TDF_DETAILS))
470 fprintf (dump_file,"Difficult to handle edges\n");
471 return false;
474 return true;
477 /* Return true, iff LOOP is if-convertible.
478 LOOP is if-convertible if,
479 - It is innermost.
480 - It has two or more basic blocks.
481 - It has only one exit.
482 - Loop header is not the exit edge.
483 - If its basic blocks and phi nodes are if convertible. See above for
484 more info.
485 FOR_VECTORIZER enables vectorizer specific checks. For example, support
486 for vector conditions, data dependency checks etc.. (Not implemented yet). */
488 static bool
489 if_convertible_loop_p (struct loop *loop, bool for_vectorizer ATTRIBUTE_UNUSED)
491 tree phi;
492 basic_block bb;
493 block_stmt_iterator itr;
494 unsigned int i;
495 edge e;
496 edge_iterator ei;
497 bool exit_bb_seen = false;
499 /* Handle only inner most loop. */
500 if (!loop || loop->inner)
502 if (dump_file && (dump_flags & TDF_DETAILS))
503 fprintf (dump_file, "not inner most loop\n");
504 return false;
507 /* If only one block, no need for if-conversion. */
508 if (loop->num_nodes <= 2)
510 if (dump_file && (dump_flags & TDF_DETAILS))
511 fprintf (dump_file, "less than 2 basic blocks\n");
512 return false;
515 /* More than one loop exit is too much to handle. */
516 if (!loop->single_exit)
518 if (dump_file && (dump_flags & TDF_DETAILS))
519 fprintf (dump_file, "multiple exits\n");
520 return false;
523 /* ??? Check target's vector conditional operation support for vectorizer. */
525 /* If one of the loop header's edge is exit edge then do not apply
526 if-conversion. */
527 FOR_EACH_EDGE (e, ei, loop->header->succs)
529 if (loop_exit_edge_p (loop, e))
530 return false;
533 calculate_dominance_info (CDI_DOMINATORS);
534 calculate_dominance_info (CDI_POST_DOMINATORS);
536 /* Allow statements that can be handled during if-conversion. */
537 ifc_bbs = get_loop_body_in_if_conv_order (loop);
538 if (!ifc_bbs)
540 if (dump_file && (dump_flags & TDF_DETAILS))
541 fprintf (dump_file,"Irreducible loop\n");
542 free_dominance_info (CDI_POST_DOMINATORS);
543 return false;
546 for (i = 0; i < loop->num_nodes; i++)
548 bb = ifc_bbs[i];
550 if (!if_convertible_bb_p (loop, bb, exit_bb_seen))
551 return false;
553 /* Check statements. */
554 for (itr = bsi_start (bb); !bsi_end_p (itr); bsi_next (&itr))
555 if (!if_convertible_stmt_p (loop, bb, bsi_stmt (itr)))
556 return false;
557 /* ??? Check data dependency for vectorizer. */
559 /* What about phi nodes ? */
560 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
561 if (!if_convertible_phi_p (loop, bb, phi))
562 return false;
564 if (bb_with_exit_edge_p (loop, bb))
565 exit_bb_seen = true;
568 /* OK. Did not find any potential issues so go ahead in if-convert
569 this loop. Now there is no looking back. */
570 if (dump_file)
571 fprintf (dump_file,"Applying if-conversion\n");
573 free_dominance_info (CDI_POST_DOMINATORS);
574 return true;
577 /* Add condition COND into predicate list of basic block BB. */
579 static void
580 add_to_predicate_list (basic_block bb, tree new_cond)
582 tree cond = bb->aux;
584 if (cond)
585 cond = fold (build (TRUTH_OR_EXPR, boolean_type_node,
586 unshare_expr (cond), new_cond));
587 else
588 cond = new_cond;
590 bb->aux = cond;
593 /* Add condition COND into BB's predicate list. PREV_COND is
594 existing condition. */
596 static tree
597 add_to_dst_predicate_list (struct loop * loop, basic_block bb,
598 tree prev_cond, tree cond,
599 block_stmt_iterator *bsi)
601 tree new_cond = NULL_TREE;
603 if (!flow_bb_inside_loop_p (loop, bb))
604 return NULL_TREE;
606 if (prev_cond == boolean_true_node || !prev_cond)
607 new_cond = unshare_expr (cond);
608 else
610 tree tmp;
611 tree tmp_stmt = NULL_TREE;
612 tree tmp_stmts1 = NULL_TREE;
613 tree tmp_stmts2 = NULL_TREE;
614 prev_cond = force_gimple_operand (unshare_expr (prev_cond),
615 &tmp_stmts1, true, NULL);
616 if (tmp_stmts1)
617 bsi_insert_before (bsi, tmp_stmts1, BSI_SAME_STMT);
619 cond = force_gimple_operand (unshare_expr (cond),
620 &tmp_stmts2, true, NULL);
621 if (tmp_stmts2)
622 bsi_insert_before (bsi, tmp_stmts2, BSI_SAME_STMT);
624 /* new_cond == prev_cond AND cond */
625 tmp = build (TRUTH_AND_EXPR, boolean_type_node,
626 unshare_expr (prev_cond), cond);
627 tmp_stmt = ifc_temp_var (boolean_type_node, tmp);
628 bsi_insert_before (bsi, tmp_stmt, BSI_SAME_STMT);
629 new_cond = TREE_OPERAND (tmp_stmt, 0);
631 add_to_predicate_list (bb, new_cond);
632 return new_cond;
635 /* During if-conversion aux field from basic block is used to hold predicate
636 list. Clean each basic block's predicate list for the given LOOP. */
638 static void
639 clean_predicate_lists (struct loop *loop)
641 basic_block *bb;
642 unsigned int i;
643 bb = get_loop_body (loop);
644 for (i = 0; i < loop->num_nodes; i++)
645 bb[i]->aux = NULL;
647 free (bb);
650 /* Basic block BB has two predecessors. Using predecessor's aux field, set
651 appropriate condition COND for the PHI node replacement. Return true block
652 whose phi arguments are selected when cond is true. */
654 static basic_block
655 find_phi_replacement_condition (struct loop *loop,
656 basic_block bb, tree *cond,
657 block_stmt_iterator *bsi)
659 basic_block first_bb = NULL;
660 basic_block second_bb = NULL;
661 tree tmp_cond;
663 gcc_assert (EDGE_COUNT (bb->preds) == 2);
664 first_bb = (EDGE_PRED (bb, 0))->src;
665 second_bb = (EDGE_PRED (bb, 1))->src;
667 /* Use condition based on following criteria:
669 S1: x = !c ? a : b;
671 S2: x = c ? b : a;
673 S2 is preferred over S1. Make 'b' first_bb and use its condition.
675 2) Do not make loop header first_bb.
678 S1: x = !(c == d)? a : b;
680 S21: t1 = c == d;
681 S22: x = t1 ? b : a;
683 S3: x = (c == d) ? b : a;
685 S3 is preferred over S1 and S2*, Make 'b' first_bb and use
686 its condition. */
688 /* Select condition that is not TRUTH_NOT_EXPR. */
689 tmp_cond = first_bb->aux;
690 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
692 basic_block tmp_bb;
693 tmp_bb = first_bb;
694 first_bb = second_bb;
695 second_bb = tmp_bb;
698 /* Check if FIRST_BB is loop header or not. */
699 if (first_bb == loop->header)
701 tmp_cond = second_bb->aux;
702 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
704 /* Select non loop header condition but do not switch basic blocks. */
705 *cond = invert_truthvalue (unshare_expr (tmp_cond));
707 else
709 /* Select non loop header condition. */
710 first_bb = second_bb;
711 *cond = first_bb->aux;
714 else
715 /* FIRST_BB is not loop header */
716 *cond = first_bb->aux;
718 /* Create temp. for the condition. Vectorizer prefers to have gimple
719 value as condition. Various targets use different means to communicate
720 condition in vector compare operation. Using gimple value allows compiler
721 to emit vector compare and select RTL without exposing compare's result. */
722 if (!is_gimple_reg (*cond) && !is_gimple_condexpr (*cond))
724 tree new_stmt;
726 new_stmt = ifc_temp_var (TREE_TYPE (*cond), unshare_expr (*cond));
727 bsi_insert_after (bsi, new_stmt, BSI_SAME_STMT);
728 bsi_next (bsi);
729 *cond = TREE_OPERAND (new_stmt, 0);
732 gcc_assert (*cond);
734 return first_bb;
738 /* Replace PHI node with conditional modify expr using COND.
739 This routine does not handle PHI nodes with more than two arguments.
740 For example,
741 S1: A = PHI <x1(1), x2(5)
742 is converted into,
743 S2: A = cond ? x1 : x2;
744 S2 is inserted at the top of basic block's statement list.
745 When COND is true, phi arg from TRUE_BB is selected.
748 static void
749 replace_phi_with_cond_modify_expr (tree phi, tree cond, basic_block true_bb,
750 block_stmt_iterator *bsi)
752 tree new_stmt;
753 basic_block bb;
754 tree rhs;
755 tree arg_0, arg_1;
757 gcc_assert (TREE_CODE (phi) == PHI_NODE);
759 /* If this is not filtered earlier, then now it is too late. */
760 gcc_assert (PHI_NUM_ARGS (phi) == 2);
762 /* Find basic block and initialize iterator. */
763 bb = bb_for_stmt (phi);
765 new_stmt = NULL_TREE;
766 arg_0 = NULL_TREE;
767 arg_1 = NULL_TREE;
769 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
770 if (EDGE_PRED (bb, 1)->src == true_bb)
772 arg_0 = PHI_ARG_DEF (phi, 1);
773 arg_1 = PHI_ARG_DEF (phi, 0);
775 else
777 arg_0 = PHI_ARG_DEF (phi, 0);
778 arg_1 = PHI_ARG_DEF (phi, 1);
781 /* Build new RHS using selected condition and arguments. */
782 rhs = build (COND_EXPR, TREE_TYPE (PHI_RESULT (phi)),
783 unshare_expr (cond), unshare_expr (arg_0),
784 unshare_expr (arg_1));
786 /* Create new MODIFY expression using RHS. */
787 new_stmt = build (MODIFY_EXPR, TREE_TYPE (PHI_RESULT (phi)),
788 unshare_expr (PHI_RESULT (phi)), rhs);
790 /* Make new statement definition of the original phi result. */
791 SSA_NAME_DEF_STMT (PHI_RESULT (phi)) = new_stmt;
793 /* Insert using iterator. */
794 bsi_insert_after (bsi, new_stmt, BSI_SAME_STMT);
795 bsi_next (bsi);
797 update_stmt (new_stmt);
799 if (dump_file && (dump_flags & TDF_DETAILS))
801 fprintf (dump_file, "new phi replacement stmt\n");
802 print_generic_stmt (dump_file, new_stmt, TDF_SLIM);
806 /* Process phi nodes for the given LOOP. Replace phi nodes with cond
807 modify expr. */
809 static void
810 process_phi_nodes (struct loop *loop)
812 basic_block bb;
813 unsigned int orig_loop_num_nodes = loop->num_nodes;
814 unsigned int i;
816 /* Replace phi nodes with cond. modify expr. */
817 for (i = 1; i < orig_loop_num_nodes; i++)
819 tree phi, cond;
820 block_stmt_iterator bsi;
821 basic_block true_bb = NULL;
822 bb = ifc_bbs[i];
824 if (bb == loop->header)
825 continue;
827 phi = phi_nodes (bb);
828 bsi = bsi_after_labels (bb);
830 /* BB has two predecessors. Using predecessor's aux field, set
831 appropriate condition for the PHI node replacement. */
832 if (phi)
833 true_bb = find_phi_replacement_condition (loop, bb, &cond, &bsi);
835 while (phi)
837 tree next = PHI_CHAIN (phi);
838 replace_phi_with_cond_modify_expr (phi, cond, true_bb, &bsi);
839 release_phi_node (phi);
840 phi = next;
842 bb->phi_nodes = NULL;
844 return;
847 /* Combine all basic block from the given LOOP into one or two super
848 basic block. Replace PHI nodes with conditional modify expression. */
850 static void
851 combine_blocks (struct loop *loop)
853 basic_block bb, exit_bb, merge_target_bb;
854 unsigned int orig_loop_num_nodes = loop->num_nodes;
855 unsigned int i;
856 unsigned int n_exits;
858 get_loop_exit_edges (loop, &n_exits);
859 /* Process phi nodes to prepare blocks for merge. */
860 process_phi_nodes (loop);
862 exit_bb = NULL;
864 /* Merge basic blocks */
865 merge_target_bb = loop->header;
866 for (i = 1; i < orig_loop_num_nodes; i++)
868 edge e;
869 block_stmt_iterator bsi;
870 tree_stmt_iterator last;
872 bb = ifc_bbs[i];
874 if (!exit_bb && bb_with_exit_edge_p (loop, bb))
875 exit_bb = bb;
877 if (bb == exit_bb)
879 edge_iterator ei;
881 /* Connect this node with loop header. */
882 make_edge (ifc_bbs[0], bb, EDGE_FALLTHRU);
883 set_immediate_dominator (CDI_DOMINATORS, bb, ifc_bbs[0]);
885 if (exit_bb != loop->latch)
887 /* Redirect non-exit edge to loop->latch. */
888 FOR_EACH_EDGE (e, ei, bb->succs)
890 if (!loop_exit_edge_p (loop, e))
892 redirect_edge_and_branch (e, loop->latch);
893 set_immediate_dominator (CDI_DOMINATORS, loop->latch, bb);
897 continue;
900 if (bb == loop->latch && empty_block_p (bb))
901 continue;
903 /* It is time to remove this basic block. First remove edges. */
904 while (EDGE_COUNT (bb->preds) > 0)
905 remove_edge (EDGE_PRED (bb, 0));
907 /* This is loop latch and loop does not have exit then do not
908 delete this basic block. Just remove its PREDS and reconnect
909 loop->header and loop->latch blocks. */
910 if (bb == loop->latch && n_exits == 0)
912 make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
913 set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
914 continue;
917 while (EDGE_COUNT (bb->succs) > 0)
918 remove_edge (EDGE_SUCC (bb, 0));
920 /* Remove labels and make stmts member of loop->header. */
921 for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
923 if (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR)
924 bsi_remove (&bsi);
925 else
927 set_bb_for_stmt (bsi_stmt (bsi), merge_target_bb);
928 bsi_next (&bsi);
932 /* Update stmt list. */
933 last = tsi_last (merge_target_bb->stmt_list);
934 tsi_link_after (&last, bb->stmt_list, TSI_NEW_STMT);
935 bb->stmt_list = NULL;
937 /* Update dominator info. */
938 if (dom_computed[CDI_DOMINATORS])
939 delete_from_dominance_info (CDI_DOMINATORS, bb);
940 if (dom_computed[CDI_POST_DOMINATORS])
941 delete_from_dominance_info (CDI_POST_DOMINATORS, bb);
943 /* Remove basic block. */
944 if (bb == loop->latch)
945 loop->latch = merge_target_bb;
946 remove_bb_from_loops (bb);
947 expunge_block (bb);
950 /* Now if possible, merge loop header and block with exit edge.
951 This reduces number of basic blocks to 2. Auto vectorizer addresses
952 loops with two nodes only. FIXME: Use cleanup_tree_cfg(). */
953 if (exit_bb
954 && loop->header != loop->latch
955 && exit_bb != loop->latch
956 && empty_block_p (loop->latch))
958 if (can_merge_blocks_p (loop->header, exit_bb))
960 remove_bb_from_loops (exit_bb);
961 merge_blocks (loop->header, exit_bb);
966 /* Make new temp variable of type TYPE. Add MODIFY_EXPR to assign EXP
967 to the new variable. */
969 static tree
970 ifc_temp_var (tree type, tree exp)
972 const char *name = "_ifc_";
973 tree var, stmt, new_name;
975 if (is_gimple_reg (exp))
976 return exp;
978 /* Create new temporary variable. */
979 var = create_tmp_var (type, name);
980 add_referenced_tmp_var (var);
982 /* Build new statement to assign EXP to new variable. */
983 stmt = build (MODIFY_EXPR, type, var, exp);
985 /* Get SSA name for the new variable and set make new statement
986 its definition statement. */
987 new_name = make_ssa_name (var, stmt);
988 TREE_OPERAND (stmt, 0) = new_name;
989 SSA_NAME_DEF_STMT (new_name) = stmt;
991 return stmt;
995 /* Return TRUE iff, all pred blocks of BB are visited.
996 Bitmap VISITED keeps history of visited blocks. */
998 static bool
999 pred_blocks_visited_p (basic_block bb, bitmap *visited)
1001 edge e;
1002 edge_iterator ei;
1003 FOR_EACH_EDGE (e, ei, bb->preds)
1004 if (!bitmap_bit_p (*visited, e->src->index))
1005 return false;
1007 return true;
1010 /* Get body of a LOOP in suitable order for if-conversion.
1011 It is caller's responsibility to deallocate basic block
1012 list. If-conversion suitable order is, BFS order with one
1013 additional constraint. Select block in BFS block, if all
1014 pred are already selected. */
1016 static basic_block *
1017 get_loop_body_in_if_conv_order (const struct loop *loop)
1019 basic_block *blocks, *blocks_in_bfs_order;
1020 basic_block bb;
1021 bitmap visited;
1022 unsigned int index = 0;
1023 unsigned int visited_count = 0;
1025 gcc_assert (loop->num_nodes);
1026 gcc_assert (loop->latch != EXIT_BLOCK_PTR);
1028 blocks = xcalloc (loop->num_nodes, sizeof (basic_block));
1029 visited = BITMAP_ALLOC (NULL);
1031 blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
1033 index = 0;
1034 while (index < loop->num_nodes)
1036 bb = blocks_in_bfs_order [index];
1038 if (bb->flags & BB_IRREDUCIBLE_LOOP)
1040 free (blocks_in_bfs_order);
1041 BITMAP_FREE (visited);
1042 free (blocks);
1043 return NULL;
1045 if (!bitmap_bit_p (visited, bb->index))
1047 if (pred_blocks_visited_p (bb, &visited)
1048 || bb == loop->header)
1050 /* This block is now visited. */
1051 bitmap_set_bit (visited, bb->index);
1052 blocks[visited_count++] = bb;
1055 index++;
1056 if (index == loop->num_nodes
1057 && visited_count != loop->num_nodes)
1059 /* Not done yet. */
1060 index = 0;
1063 free (blocks_in_bfs_order);
1064 BITMAP_FREE (visited);
1065 return blocks;
1068 /* Return true if one of the basic block BB edge is exit of LOOP. */
1070 static bool
1071 bb_with_exit_edge_p (struct loop *loop, basic_block bb)
1073 edge e;
1074 edge_iterator ei;
1075 bool exit_edge_found = false;
1077 FOR_EACH_EDGE (e, ei, bb->succs)
1078 if (loop_exit_edge_p (loop, e))
1080 exit_edge_found = true;
1081 break;
1084 return exit_edge_found;
1087 /* Tree if-conversion pass management. */
1089 static void
1090 main_tree_if_conversion (void)
1092 unsigned i, loop_num;
1093 struct loop *loop;
1095 if (!current_loops)
1096 return;
1098 loop_num = current_loops->num;
1099 for (i = 0; i < loop_num; i++)
1101 loop = current_loops->parray[i];
1102 if (!loop)
1103 continue;
1105 tree_if_conversion (loop, true);
1110 static bool
1111 gate_tree_if_conversion (void)
1113 return flag_tree_vectorize != 0;
1116 struct tree_opt_pass pass_if_conversion =
1118 "ifcvt", /* name */
1119 gate_tree_if_conversion, /* gate */
1120 main_tree_if_conversion, /* execute */
1121 NULL, /* sub */
1122 NULL, /* next */
1123 0, /* static_pass_number */
1124 0, /* tv_id */
1125 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1126 0, /* properties_provided */
1127 0, /* properties_destroyed */
1128 0, /* todo_flags_start */
1129 TODO_dump_func | TODO_verify_loops | TODO_verify_stmts | TODO_verify_flow,
1130 /* todo_flags_finish */
1131 0 /* letter */