1 /* If-conversion for vectorizer.
2 Copyright (C) 2004, 2005, 2006, 2007 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 3, or (at your option) any later
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
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
21 /* This pass implements tree level if-conversion transformation of loops.
22 Initial goal is to help vectorizer vectorize loops with conditions.
24 A short description of if-conversion:
26 o Decide if a loop is if-convertible or not.
27 o Walk all loop basic blocks in breadth first order (BFS order).
28 o Remove conditional statements (at the end of basic block)
29 and propagate condition into destination basic blocks'
31 o Replace modify expression with conditional modify expression
32 using current basic block's condition.
33 o Merge all basic blocks
34 o Replace phi nodes with conditional modify expr
35 o Merge all basic blocks into header
37 Sample transformation:
42 # i_23 = PHI <0(0), i_18(10)>;
45 if (j_15 > 41) goto <L1>; else goto <L17>;
52 # iftmp.2_4 = PHI <0(8), 42(2)>;
56 if (i_18 <= 15) goto <L19>; else goto <L18>;
66 # i_23 = PHI <0(0), i_18(10)>;
71 iftmp.2_4 = j_15 > 41 ? 42 : 0;
74 if (i_18 <= 15) goto <L19>; else goto <L18>;
84 #include "coretypes.h"
92 #include "basic-block.h"
93 #include "diagnostic.h"
94 #include "tree-flow.h"
95 #include "tree-dump.h"
97 #include "tree-chrec.h"
98 #include "tree-data-ref.h"
99 #include "tree-scalar-evolution.h"
100 #include "tree-pass.h"
103 /* local function prototypes */
104 static unsigned int main_tree_if_conversion (void);
105 static tree tree_if_convert_stmt (struct loop *loop, tree, tree,
106 block_stmt_iterator *);
107 static void tree_if_convert_cond_expr (struct loop *, tree, tree,
108 block_stmt_iterator *);
109 static bool if_convertible_phi_p (struct loop *, basic_block, tree);
110 static bool if_convertible_gimple_modify_stmt_p (struct loop *, basic_block,
112 static bool if_convertible_stmt_p (struct loop *, basic_block, tree);
113 static bool if_convertible_bb_p (struct loop *, basic_block, basic_block);
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, edge,
118 block_stmt_iterator *);
119 static void clean_predicate_lists (struct loop *loop);
120 static basic_block find_phi_replacement_condition (struct loop *loop,
122 block_stmt_iterator *);
123 static void replace_phi_with_cond_gimple_modify_stmt (tree, tree, basic_block,
124 block_stmt_iterator *);
125 static void process_phi_nodes (struct loop *);
126 static void combine_blocks (struct loop *);
127 static tree ifc_temp_var (tree, tree);
128 static bool pred_blocks_visited_p (basic_block, bitmap *);
129 static basic_block * get_loop_body_in_if_conv_order (const struct loop *loop);
130 static bool bb_with_exit_edge_p (struct loop *, basic_block);
132 /* List of basic blocks in if-conversion-suitable order. */
133 static basic_block *ifc_bbs;
136 Apply if-conversion to the LOOP. Return true if successful otherwise return
137 false. If false is returned then loop remains unchanged.
138 FOR_VECTORIZER is a boolean flag. It indicates whether if-conversion is used
139 for vectorizer or not. If it is used for vectorizer, additional checks are
140 used. (Vectorization checks are not yet implemented). */
143 tree_if_conversion (struct loop *loop, bool for_vectorizer)
146 block_stmt_iterator itr;
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");
162 free_dominance_info (CDI_POST_DOMINATORS);
166 /* Do actual work now. */
167 for (i = 0; i < loop->num_nodes; i++)
173 /* Update condition using predicate list. */
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))
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);
193 /* Successor bb inherits predicate of its predecessor. If there
194 is no predicate in predecessor bb, then consider successor bb
195 as always executed. */
196 if (cond == NULL_TREE)
197 cond = boolean_true_node;
199 add_to_predicate_list (bb_n, cond);
203 /* Now, all statements are if-converted and basic blocks are
204 annotated appropriately. Combine all basic block into one huge
206 combine_blocks (loop);
209 clean_predicate_lists (loop);
216 /* if-convert stmt T which is part of LOOP.
217 If T is a GIMPLE_MODIFY_STMT than it is converted into conditional modify
218 expression using COND. For conditional expressions, add condition in the
219 destination basic block's predicate list and remove conditional
220 expression itself. BSI is the iterator used to traverse statements of
221 loop. It is used here when it is required to delete current statement. */
224 tree_if_convert_stmt (struct loop * loop, tree t, tree cond,
225 block_stmt_iterator *bsi)
227 if (dump_file && (dump_flags & TDF_DETAILS))
229 fprintf (dump_file, "------if-convert stmt\n");
230 print_generic_stmt (dump_file, t, TDF_SLIM);
231 print_generic_stmt (dump_file, cond, TDF_SLIM);
234 switch (TREE_CODE (t))
236 /* Labels are harmless here. */
240 case GIMPLE_MODIFY_STMT:
241 /* This GIMPLE_MODIFY_STMT is killing previous value of LHS. Appropriate
242 value will be selected by PHI node based on condition. It is possible
243 that before this transformation, PHI nodes was selecting default
244 value and now it will use this new value. This is OK because it does
245 not change validity the program. */
249 /* Update destination blocks' predicate list and remove this
250 condition expression. */
251 tree_if_convert_cond_expr (loop, t, cond, bsi);
261 /* STMT is COND_EXPR. Update two destination's predicate list.
262 Remove COND_EXPR, if it is not the loop exit condition. Otherwise
263 update loop exit condition appropriately. BSI is the iterator
264 used to traverse statement list. STMT is part of loop LOOP. */
267 tree_if_convert_cond_expr (struct loop *loop, tree stmt, tree cond,
268 block_stmt_iterator *bsi)
271 edge true_edge, false_edge;
273 gcc_assert (TREE_CODE (stmt) == COND_EXPR);
275 c = COND_EXPR_COND (stmt);
277 extract_true_false_edges_from_block (bb_for_stmt (stmt),
278 &true_edge, &false_edge);
280 /* Add new condition into destination's predicate list. */
282 /* If 'c' is true then TRUE_EDGE is taken. */
283 add_to_dst_predicate_list (loop, true_edge, cond,
284 unshare_expr (c), bsi);
286 /* If 'c' is false then FALSE_EDGE is taken. */
287 c2 = invert_truthvalue (unshare_expr (c));
288 add_to_dst_predicate_list (loop, false_edge, cond, c2, bsi);
290 /* Now this conditional statement is redundant. Remove it.
291 But, do not remove exit condition! Update exit condition
292 using new condition. */
293 if (!bb_with_exit_edge_p (loop, bb_for_stmt (stmt)))
295 bsi_remove (bsi, true);
301 /* Return true, iff PHI is if-convertible. PHI is part of loop LOOP
302 and it belongs to basic block BB.
303 PHI is not if-convertible
304 - if it has more than 2 arguments.
305 - Virtual PHI is immediately used in another PHI node. */
308 if_convertible_phi_p (struct loop *loop, basic_block bb, tree phi)
310 if (dump_file && (dump_flags & TDF_DETAILS))
312 fprintf (dump_file, "-------------------------\n");
313 print_generic_stmt (dump_file, phi, TDF_SLIM);
316 if (bb != loop->header && PHI_NUM_ARGS (phi) != 2)
318 if (dump_file && (dump_flags & TDF_DETAILS))
319 fprintf (dump_file, "More than two phi node args.\n");
323 if (!is_gimple_reg (SSA_NAME_VAR (PHI_RESULT (phi))))
325 imm_use_iterator imm_iter;
327 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, PHI_RESULT (phi))
329 if (TREE_CODE (USE_STMT (use_p)) == PHI_NODE)
331 if (dump_file && (dump_flags & TDF_DETAILS))
332 fprintf (dump_file, "Difficult to handle this virtual phi.\n");
341 /* Return true, if M_EXPR is if-convertible.
342 GIMPLE_MODIFY_STMT is not if-convertible if,
345 - LHS is not var decl.
346 GIMPLE_MODIFY_STMT is part of block BB, which is inside loop LOOP.
350 if_convertible_gimple_modify_stmt_p (struct loop *loop, basic_block bb,
355 if (TREE_CODE (m_expr) != GIMPLE_MODIFY_STMT)
358 if (dump_file && (dump_flags & TDF_DETAILS))
360 fprintf (dump_file, "-------------------------\n");
361 print_generic_stmt (dump_file, m_expr, TDF_SLIM);
364 lhs = GIMPLE_STMT_OPERAND (m_expr, 0);
365 rhs = GIMPLE_STMT_OPERAND (m_expr, 1);
367 /* Some of these constrains might be too conservative. */
368 if (stmt_ends_bb_p (m_expr) || stmt_ann (m_expr)->has_volatile_ops
369 || (TREE_CODE (lhs) == SSA_NAME
370 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
371 || TREE_SIDE_EFFECTS (rhs))
373 if (dump_file && (dump_flags & TDF_DETAILS))
374 fprintf (dump_file, "stmt not suitable for ifcvt\n");
378 /* See if it needs speculative loading or not. */
379 if (bb != loop->header
380 && tree_could_trap_p (GIMPLE_STMT_OPERAND (m_expr, 1)))
382 if (dump_file && (dump_flags & TDF_DETAILS))
383 fprintf (dump_file, "tree could trap...\n");
387 if (TREE_CODE (GIMPLE_STMT_OPERAND (m_expr, 1)) == CALL_EXPR)
389 if (dump_file && (dump_flags & TDF_DETAILS))
390 fprintf (dump_file, "CALL_EXPR \n");
394 if (TREE_CODE (GIMPLE_STMT_OPERAND (m_expr, 0)) != SSA_NAME
395 && bb != loop->header
396 && !bb_with_exit_edge_p (loop, bb))
398 if (dump_file && (dump_flags & TDF_DETAILS))
400 fprintf (dump_file, "LHS is not var\n");
401 print_generic_stmt (dump_file, m_expr, TDF_SLIM);
410 /* Return true, iff STMT is if-convertible.
411 Statement is if-convertible if,
412 - It is if-convertible GIMPLE_MODIFY_STMT
413 - IT is LABEL_EXPR or COND_EXPR.
414 STMT is inside block BB, which is inside loop LOOP. */
417 if_convertible_stmt_p (struct loop *loop, basic_block bb, tree stmt)
419 switch (TREE_CODE (stmt))
424 case GIMPLE_MODIFY_STMT:
426 if (!if_convertible_gimple_modify_stmt_p (loop, bb, stmt))
434 /* Don't know what to do with 'em so don't do anything. */
435 if (dump_file && (dump_flags & TDF_DETAILS))
437 fprintf (dump_file, "don't know what to do\n");
438 print_generic_stmt (dump_file, stmt, TDF_SLIM);
447 /* Return true, iff BB is if-convertible.
448 Note: This routine does _not_ check basic block statements and phis.
449 Basic block is not if-convertible if,
450 - Basic block is non-empty and it is after exit block (in BFS order).
451 - Basic block is after exit block but before latch.
452 - Basic block edge(s) is not normal.
453 EXIT_BB_SEEN is true if basic block with exit edge is already seen.
454 BB is inside loop LOOP. */
457 if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
462 if (dump_file && (dump_flags & TDF_DETAILS))
463 fprintf (dump_file, "----------[%d]-------------\n", bb->index);
467 if (bb != loop->latch)
469 if (dump_file && (dump_flags & TDF_DETAILS))
470 fprintf (dump_file, "basic block after exit bb but before latch\n");
473 else if (!empty_block_p (bb))
475 if (dump_file && (dump_flags & TDF_DETAILS))
476 fprintf (dump_file, "non empty basic block after exit bb\n");
479 else if (bb == loop->latch
481 && !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
483 if (dump_file && (dump_flags & TDF_DETAILS))
484 fprintf (dump_file, "latch is not dominated by exit_block\n");
489 /* Be less adventurous and handle only normal edges. */
490 FOR_EACH_EDGE (e, ei, bb->succs)
492 (EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
494 if (dump_file && (dump_flags & TDF_DETAILS))
495 fprintf (dump_file,"Difficult to handle edges\n");
502 /* Return true, iff LOOP is if-convertible.
503 LOOP is if-convertible if,
505 - It has two or more basic blocks.
506 - It has only one exit.
507 - Loop header is not the exit edge.
508 - If its basic blocks and phi nodes are if convertible. See above for
510 FOR_VECTORIZER enables vectorizer specific checks. For example, support
511 for vector conditions, data dependency checks etc.. (Not implemented yet). */
514 if_convertible_loop_p (struct loop *loop, bool for_vectorizer ATTRIBUTE_UNUSED)
518 block_stmt_iterator itr;
522 basic_block exit_bb = NULL;
524 /* Handle only inner most loop. */
525 if (!loop || loop->inner)
527 if (dump_file && (dump_flags & TDF_DETAILS))
528 fprintf (dump_file, "not inner most loop\n");
532 /* If only one block, no need for if-conversion. */
533 if (loop->num_nodes <= 2)
535 if (dump_file && (dump_flags & TDF_DETAILS))
536 fprintf (dump_file, "less than 2 basic blocks\n");
540 /* More than one loop exit is too much to handle. */
541 if (!single_exit (loop))
543 if (dump_file && (dump_flags & TDF_DETAILS))
544 fprintf (dump_file, "multiple exits\n");
548 /* ??? Check target's vector conditional operation support for vectorizer. */
550 /* If one of the loop header's edge is exit edge then do not apply
552 FOR_EACH_EDGE (e, ei, loop->header->succs)
554 if (loop_exit_edge_p (loop, e))
558 calculate_dominance_info (CDI_DOMINATORS);
559 calculate_dominance_info (CDI_POST_DOMINATORS);
561 /* Allow statements that can be handled during if-conversion. */
562 ifc_bbs = get_loop_body_in_if_conv_order (loop);
565 if (dump_file && (dump_flags & TDF_DETAILS))
566 fprintf (dump_file,"Irreducible loop\n");
567 free_dominance_info (CDI_POST_DOMINATORS);
571 for (i = 0; i < loop->num_nodes; i++)
575 if (!if_convertible_bb_p (loop, bb, exit_bb))
578 /* Check statements. */
579 for (itr = bsi_start (bb); !bsi_end_p (itr); bsi_next (&itr))
580 if (!if_convertible_stmt_p (loop, bb, bsi_stmt (itr)))
582 /* ??? Check data dependency for vectorizer. */
584 /* What about phi nodes ? */
585 phi = phi_nodes (bb);
587 /* Clear aux field of incoming edges to a bb with a phi node. */
589 FOR_EACH_EDGE (e, ei, bb->preds)
592 /* Check statements. */
593 for (; phi; phi = PHI_CHAIN (phi))
594 if (!if_convertible_phi_p (loop, bb, phi))
597 if (bb_with_exit_edge_p (loop, bb))
601 /* OK. Did not find any potential issues so go ahead in if-convert
602 this loop. Now there is no looking back. */
604 fprintf (dump_file,"Applying if-conversion\n");
606 free_dominance_info (CDI_POST_DOMINATORS);
610 /* Add condition COND into predicate list of basic block BB. */
613 add_to_predicate_list (basic_block bb, tree new_cond)
618 cond = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
619 unshare_expr (cond), new_cond);
626 /* Add condition COND into BB's predicate list. PREV_COND is
627 existing condition. */
630 add_to_dst_predicate_list (struct loop * loop, edge e,
631 tree prev_cond, tree cond,
632 block_stmt_iterator *bsi)
634 tree new_cond = NULL_TREE;
636 if (!flow_bb_inside_loop_p (loop, e->dest))
639 if (prev_cond == boolean_true_node || !prev_cond)
640 new_cond = unshare_expr (cond);
644 tree tmp_stmt = NULL_TREE;
646 prev_cond = force_gimple_operand_bsi (bsi, unshare_expr (prev_cond),
647 true, NULL, true, BSI_SAME_STMT);
649 cond = force_gimple_operand_bsi (bsi, unshare_expr (cond),
650 true, NULL, true, BSI_SAME_STMT);
652 /* Add the condition to aux field of the edge. In case edge
653 destination is a PHI node, this condition will be ANDed with
654 block predicate to construct complete condition. */
657 /* new_cond == prev_cond AND cond */
658 tmp = build2 (TRUTH_AND_EXPR, boolean_type_node,
659 unshare_expr (prev_cond), cond);
660 tmp_stmt = ifc_temp_var (boolean_type_node, tmp);
661 bsi_insert_before (bsi, tmp_stmt, BSI_SAME_STMT);
662 new_cond = GIMPLE_STMT_OPERAND (tmp_stmt, 0);
664 add_to_predicate_list (e->dest, new_cond);
668 /* During if-conversion aux field from basic block structure is used to hold
669 predicate list. Clean each basic block's predicate list for the given LOOP.
670 Also clean aux field of successor edges, used to hold true and false
671 condition from conditional expression. */
674 clean_predicate_lists (struct loop *loop)
681 bb = get_loop_body (loop);
682 for (i = 0; i < loop->num_nodes; i++)
685 FOR_EACH_EDGE (e, ei, bb[i]->succs)
691 /* Basic block BB has two predecessors. Using predecessor's aux field, set
692 appropriate condition COND for the PHI node replacement. Return true block
693 whose phi arguments are selected when cond is true. */
696 find_phi_replacement_condition (struct loop *loop,
697 basic_block bb, tree *cond,
698 block_stmt_iterator *bsi)
700 edge first_edge, second_edge;
703 gcc_assert (EDGE_COUNT (bb->preds) == 2);
704 first_edge = EDGE_PRED (bb, 0);
705 second_edge = EDGE_PRED (bb, 1);
707 /* Use condition based on following criteria:
713 S2 is preferred over S1. Make 'b' first_bb and use its condition.
715 2) Do not make loop header first_bb.
718 S1: x = !(c == d)? a : b;
723 S3: x = (c == d) ? b : a;
725 S3 is preferred over S1 and S2*, Make 'b' first_bb and use
728 4) If pred B is dominated by pred A then use pred B's condition.
731 /* Select condition that is not TRUTH_NOT_EXPR. */
732 tmp_cond = (first_edge->src)->aux;
733 gcc_assert (tmp_cond);
735 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
739 tmp_edge = first_edge;
740 first_edge = second_edge;
741 second_edge = tmp_edge;
744 /* Check if FIRST_BB is loop header or not and make sure that
745 FIRST_BB does not dominate SECOND_BB. */
746 if (first_edge->src == loop->header
747 || dominated_by_p (CDI_DOMINATORS,
748 second_edge->src, first_edge->src))
750 *cond = (second_edge->src)->aux;
752 /* If there is a condition on an incoming edge,
753 AND it with the incoming bb predicate. */
754 if (second_edge->aux)
755 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
756 *cond, second_edge->aux);
758 if (TREE_CODE (*cond) == TRUTH_NOT_EXPR)
759 /* We can be smart here and choose inverted
760 condition without switching bbs. */
761 *cond = invert_truthvalue (*cond);
763 /* Select non loop header bb. */
764 first_edge = second_edge;
768 /* FIRST_BB is not loop header */
769 *cond = (first_edge->src)->aux;
771 /* If there is a condition on an incoming edge,
772 AND it with the incoming bb predicate. */
774 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
775 *cond, first_edge->aux);
778 /* Create temp. for the condition. Vectorizer prefers to have gimple
779 value as condition. Various targets use different means to communicate
780 condition in vector compare operation. Using gimple value allows
781 compiler to emit vector compare and select RTL without exposing
783 *cond = force_gimple_operand_bsi (bsi, unshare_expr (*cond),
785 true, BSI_SAME_STMT);
786 if (!is_gimple_reg (*cond) && !is_gimple_condexpr (*cond))
790 new_stmt = ifc_temp_var (TREE_TYPE (*cond), unshare_expr (*cond));
791 bsi_insert_before (bsi, new_stmt, BSI_SAME_STMT);
792 *cond = GIMPLE_STMT_OPERAND (new_stmt, 0);
797 return first_edge->src;
801 /* Replace PHI node with conditional modify expr using COND.
802 This routine does not handle PHI nodes with more than two arguments.
804 S1: A = PHI <x1(1), x2(5)
806 S2: A = cond ? x1 : x2;
807 S2 is inserted at the top of basic block's statement list.
808 When COND is true, phi arg from TRUE_BB is selected.
812 replace_phi_with_cond_gimple_modify_stmt (tree phi, tree cond,
814 block_stmt_iterator *bsi)
821 gcc_assert (TREE_CODE (phi) == PHI_NODE);
823 /* If this is not filtered earlier, then now it is too late. */
824 gcc_assert (PHI_NUM_ARGS (phi) == 2);
826 /* Find basic block and initialize iterator. */
827 bb = bb_for_stmt (phi);
829 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
830 if (EDGE_PRED (bb, 1)->src == true_bb)
832 arg_0 = PHI_ARG_DEF (phi, 1);
833 arg_1 = PHI_ARG_DEF (phi, 0);
837 arg_0 = PHI_ARG_DEF (phi, 0);
838 arg_1 = PHI_ARG_DEF (phi, 1);
841 /* Build new RHS using selected condition and arguments. */
842 rhs = build3 (COND_EXPR, TREE_TYPE (PHI_RESULT (phi)),
843 unshare_expr (cond), unshare_expr (arg_0),
844 unshare_expr (arg_1));
846 /* Create new MODIFY expression using RHS. */
847 new_stmt = build_gimple_modify_stmt (unshare_expr (PHI_RESULT (phi)), rhs);
849 /* Make new statement definition of the original phi result. */
850 SSA_NAME_DEF_STMT (PHI_RESULT (phi)) = new_stmt;
852 /* Insert using iterator. */
853 bsi_insert_before (bsi, new_stmt, BSI_SAME_STMT);
854 update_stmt (new_stmt);
856 if (dump_file && (dump_flags & TDF_DETAILS))
858 fprintf (dump_file, "new phi replacement stmt\n");
859 print_generic_stmt (dump_file, new_stmt, TDF_SLIM);
863 /* Process phi nodes for the given LOOP. Replace phi nodes with cond
867 process_phi_nodes (struct loop *loop)
870 unsigned int orig_loop_num_nodes = loop->num_nodes;
873 /* Replace phi nodes with cond. modify expr. */
874 for (i = 1; i < orig_loop_num_nodes; i++)
877 block_stmt_iterator bsi;
878 basic_block true_bb = NULL;
881 if (bb == loop->header)
884 phi = phi_nodes (bb);
885 bsi = bsi_after_labels (bb);
887 /* BB has two predecessors. Using predecessor's aux field, set
888 appropriate condition for the PHI node replacement. */
890 true_bb = find_phi_replacement_condition (loop, bb, &cond, &bsi);
894 tree next = PHI_CHAIN (phi);
895 replace_phi_with_cond_gimple_modify_stmt (phi, cond, true_bb, &bsi);
896 release_phi_node (phi);
899 set_phi_nodes (bb, NULL_TREE);
904 /* Combine all basic block from the given LOOP into one or two super
905 basic block. Replace PHI nodes with conditional modify expression. */
908 combine_blocks (struct loop *loop)
910 basic_block bb, exit_bb, merge_target_bb;
911 unsigned int orig_loop_num_nodes = loop->num_nodes;
916 /* Process phi nodes to prepare blocks for merge. */
917 process_phi_nodes (loop);
919 /* Merge basic blocks. First remove all the edges in the loop, except
920 for those from the exit block. */
922 for (i = 0; i < orig_loop_num_nodes; i++)
925 if (bb_with_exit_edge_p (loop, bb))
931 gcc_assert (exit_bb != loop->latch);
933 for (i = 1; i < orig_loop_num_nodes; i++)
937 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei));)
939 if (e->src == exit_bb)
948 if (exit_bb != loop->header)
950 /* Connect this node with loop header. */
951 make_edge (loop->header, exit_bb, EDGE_FALLTHRU);
952 set_immediate_dominator (CDI_DOMINATORS, exit_bb, loop->header);
955 /* Redirect non-exit edges to loop->latch. */
956 FOR_EACH_EDGE (e, ei, exit_bb->succs)
958 if (!loop_exit_edge_p (loop, e))
959 redirect_edge_and_branch (e, loop->latch);
961 set_immediate_dominator (CDI_DOMINATORS, loop->latch, exit_bb);
965 /* If the loop does not have exit then reconnect header and latch. */
966 make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
967 set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
970 merge_target_bb = loop->header;
971 for (i = 1; i < orig_loop_num_nodes; i++)
973 block_stmt_iterator bsi;
974 tree_stmt_iterator last;
978 if (bb == exit_bb || bb == loop->latch)
981 /* Remove labels and make stmts member of loop->header. */
982 for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
984 if (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR)
985 bsi_remove (&bsi, true);
988 set_bb_for_stmt (bsi_stmt (bsi), merge_target_bb);
993 /* Update stmt list. */
994 last = tsi_last (bb_stmt_list (merge_target_bb));
995 tsi_link_after (&last, bb_stmt_list (bb), TSI_NEW_STMT);
996 set_bb_stmt_list (bb, alloc_stmt_list());
998 delete_basic_block (bb);
1001 /* Now if possible, merge loop header and block with exit edge.
1002 This reduces number of basic blocks to 2. Auto vectorizer addresses
1003 loops with two nodes only. FIXME: Use cleanup_tree_cfg(). */
1005 && exit_bb != loop->header
1006 && can_merge_blocks_p (loop->header, exit_bb))
1007 merge_blocks (loop->header, exit_bb);
1010 /* Make new temp variable of type TYPE. Add GIMPLE_MODIFY_STMT to assign EXP
1011 to the new variable. */
1014 ifc_temp_var (tree type, tree exp)
1016 const char *name = "_ifc_";
1017 tree var, stmt, new_name;
1019 if (is_gimple_reg (exp))
1022 /* Create new temporary variable. */
1023 var = create_tmp_var (type, name);
1024 add_referenced_var (var);
1026 /* Build new statement to assign EXP to new variable. */
1027 stmt = build_gimple_modify_stmt (var, exp);
1029 /* Get SSA name for the new variable and set make new statement
1030 its definition statement. */
1031 new_name = make_ssa_name (var, stmt);
1032 GIMPLE_STMT_OPERAND (stmt, 0) = new_name;
1033 SSA_NAME_DEF_STMT (new_name) = stmt;
1039 /* Return TRUE iff, all pred blocks of BB are visited.
1040 Bitmap VISITED keeps history of visited blocks. */
1043 pred_blocks_visited_p (basic_block bb, bitmap *visited)
1047 FOR_EACH_EDGE (e, ei, bb->preds)
1048 if (!bitmap_bit_p (*visited, e->src->index))
1054 /* Get body of a LOOP in suitable order for if-conversion.
1055 It is caller's responsibility to deallocate basic block
1056 list. If-conversion suitable order is, BFS order with one
1057 additional constraint. Select block in BFS block, if all
1058 pred are already selected. */
1060 static basic_block *
1061 get_loop_body_in_if_conv_order (const struct loop *loop)
1063 basic_block *blocks, *blocks_in_bfs_order;
1066 unsigned int index = 0;
1067 unsigned int visited_count = 0;
1069 gcc_assert (loop->num_nodes);
1070 gcc_assert (loop->latch != EXIT_BLOCK_PTR);
1072 blocks = XCNEWVEC (basic_block, loop->num_nodes);
1073 visited = BITMAP_ALLOC (NULL);
1075 blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
1078 while (index < loop->num_nodes)
1080 bb = blocks_in_bfs_order [index];
1082 if (bb->flags & BB_IRREDUCIBLE_LOOP)
1084 free (blocks_in_bfs_order);
1085 BITMAP_FREE (visited);
1089 if (!bitmap_bit_p (visited, bb->index))
1091 if (pred_blocks_visited_p (bb, &visited)
1092 || bb == loop->header)
1094 /* This block is now visited. */
1095 bitmap_set_bit (visited, bb->index);
1096 blocks[visited_count++] = bb;
1100 if (index == loop->num_nodes
1101 && visited_count != loop->num_nodes)
1107 free (blocks_in_bfs_order);
1108 BITMAP_FREE (visited);
1112 /* Return true if one of the basic block BB edge is exit of LOOP. */
1115 bb_with_exit_edge_p (struct loop *loop, basic_block bb)
1119 bool exit_edge_found = false;
1121 FOR_EACH_EDGE (e, ei, bb->succs)
1122 if (loop_exit_edge_p (loop, e))
1124 exit_edge_found = true;
1128 return exit_edge_found;
1131 /* Tree if-conversion pass management. */
1134 main_tree_if_conversion (void)
1139 if (number_of_loops () <= 1)
1142 FOR_EACH_LOOP (li, loop, 0)
1144 tree_if_conversion (loop, true);
1150 gate_tree_if_conversion (void)
1152 return flag_tree_vectorize != 0;
1155 struct tree_opt_pass pass_if_conversion =
1158 gate_tree_if_conversion, /* gate */
1159 main_tree_if_conversion, /* execute */
1162 0, /* static_pass_number */
1164 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1165 0, /* properties_provided */
1166 0, /* properties_destroyed */
1167 0, /* todo_flags_start */
1168 TODO_dump_func | TODO_verify_loops | TODO_verify_stmts | TODO_verify_flow,
1169 /* todo_flags_finish */