1 /* If-conversion for vectorizer.
2 Copyright (C) 2004 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
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 COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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'
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:
43 # i_23 = PHI <0(0), i_18(10)>;
46 if (j_15 > 41) goto <L1>; else goto <L17>;
53 # iftmp.2_4 = PHI <0(8), 42(2)>;
57 if (i_18 <= 15) goto <L19>; else goto <L18>;
67 # i_23 = PHI <0(0), i_18(10)>;
72 iftmp.2_4 = j_15 > 41 ? 42 : 0;
75 if (i_18 <= 15) goto <L19>; else goto <L18>;
85 #include "coretypes.h"
94 #include "basic-block.h"
95 #include "diagnostic.h"
96 #include "tree-flow.h"
97 #include "tree-dump.h"
99 #include "tree-chrec.h"
100 #include "tree-data-ref.h"
101 #include "tree-scalar-evolution.h"
102 #include "tree-pass.h"
105 /* local function prototypes */
106 static void main_tree_if_conversion (void);
107 static tree tree_if_convert_stmt (struct loop *loop, tree, tree,
108 block_stmt_iterator *);
109 static void tree_if_convert_cond_expr (struct loop *, tree, tree,
110 block_stmt_iterator *);
111 static bool if_convertible_phi_p (struct loop *, basic_block, tree);
112 static bool if_convertible_modify_expr_p (struct loop *, basic_block, tree);
113 static bool if_convertible_stmt_p (struct loop *, basic_block, tree);
114 static bool if_convertible_bb_p (struct loop *, basic_block, bool);
115 static bool if_convertible_loop_p (struct loop *, bool);
116 static void add_to_predicate_list (basic_block, tree);
117 static tree add_to_dst_predicate_list (struct loop * loop, basic_block, tree, tree,
118 block_stmt_iterator *);
119 static void clean_predicate_lists (struct loop *loop);
120 static basic_block find_phi_replacement_condition (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 (basic_block);
131 /* List of basic blocks in if-conversion-suitable order. */
132 static basic_block *ifc_bbs;
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). */
142 tree_if_conversion (struct loop *loop, bool for_vectorizer)
145 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);
169 /* Do actual work now. */
170 for (i = 0; i < loop->num_nodes; i++)
174 /* Update condition using predicate list. */
177 /* Process all statements in this basic block.
178 Remove conditional expression, if any, and annotate
179 destination basic block(s) appropriately. */
180 for (itr = bsi_start (bb); !bsi_end_p (itr); /* empty */)
182 tree t = bsi_stmt (itr);
183 cond = tree_if_convert_stmt (loop, t, cond, &itr);
184 if (!bsi_end_p (itr))
188 /* If current bb has only one successor, then consider it as an
189 unconditional goto. */
190 if (EDGE_COUNT (bb->succs) == 1)
192 basic_block bb_n = EDGE_SUCC (bb, 0)->dest;
193 if (cond != NULL_TREE)
194 add_to_predicate_list (bb_n, cond);
199 /* Now, all statements are if-converted and basic blocks are
200 annotated appropriately. Combine all basic block into one huge
202 combine_blocks (loop);
205 clean_predicate_lists (loop);
213 /* if-convert stmt T which is part of LOOP.
214 If T is a MODIFY_EXPR than it is converted into conditional modify
215 expression using COND. For conditional expressions, add condition in the
216 destination basic block's predicate list and remove conditional
217 expression itself. BSI is the iterator used to traverse statements of
218 loop. It is used here when it is required to delete current statement. */
221 tree_if_convert_stmt (struct loop * loop, tree t, tree cond,
222 block_stmt_iterator *bsi)
224 if (dump_file && (dump_flags & TDF_DETAILS))
226 fprintf (dump_file, "------if-convert stmt\n");
227 print_generic_stmt (dump_file, t, TDF_SLIM);
228 print_generic_stmt (dump_file, cond, TDF_SLIM);
231 switch (TREE_CODE (t))
233 /* Labels are harmless here. */
238 /* This modify_expr is killing previous value of LHS. Appropriate value will
239 be selected by PHI node based on condition. It is possible that before
240 this transformation, PHI nodes was selecting default value and now it will
241 use this new value. This is OK because it does not change validity the
246 /* Unconditional goto */
247 add_to_predicate_list (bb_for_stmt (TREE_OPERAND (t, 1)), cond);
253 /* Update destination blocks' predicate list and remove this
254 condition expression. */
255 tree_if_convert_cond_expr (loop, t, cond, bsi);
265 /* STMT is COND_EXPR. Update two destination's predicate list.
266 Remove COND_EXPR, if it is not the loop exit condition. Otherwise
267 update loop exit condition appropriately. BSI is the iterator
268 used to traverse statement list. STMT is part of loop LOOP. */
271 tree_if_convert_cond_expr (struct loop *loop, tree stmt, tree cond,
272 block_stmt_iterator *bsi)
274 tree c, c2, new_cond;
275 edge true_edge, false_edge;
276 new_cond = NULL_TREE;
278 gcc_assert (TREE_CODE (stmt) == COND_EXPR);
280 c = COND_EXPR_COND (stmt);
282 /* Create temp. for condition. */
283 if (!is_gimple_condexpr (c))
286 new_stmt = ifc_temp_var (TREE_TYPE (c), unshare_expr (c));
287 bsi_insert_before (bsi, new_stmt, BSI_SAME_STMT);
288 c = TREE_OPERAND (new_stmt, 0);
291 extract_true_false_edges_from_block (bb_for_stmt (stmt),
292 &true_edge, &false_edge);
294 /* Add new condition into destination's predicate list. */
296 /* If 'c' is true then TRUE_EDGE is taken. */
297 new_cond = add_to_dst_predicate_list (loop, true_edge->dest, cond,
298 unshare_expr (c), bsi);
300 if (!is_gimple_reg(c) && is_gimple_condexpr (c))
303 new_stmt = ifc_temp_var (TREE_TYPE (c), unshare_expr (c));
304 bsi_insert_before (bsi, new_stmt, BSI_SAME_STMT);
305 c = TREE_OPERAND (new_stmt, 0);
308 /* If 'c' is false then FALSE_EDGE is taken. */
309 c2 = invert_truthvalue (unshare_expr (c));
310 add_to_dst_predicate_list (loop, false_edge->dest, cond, c2, bsi);
312 /* Now this conditional statement is redundant. Remove it.
313 But, do not remove exit condition! Update exit condition
314 using new condition. */
315 if (!bb_with_exit_edge_p (bb_for_stmt (stmt)))
323 /* Return true, iff PHI is if-convertible. PHI is part of loop LOOP
324 and it belongs to basic block BB.
325 PHI is not if-convertible
326 - if it has more than 2 arguments.
327 - Virtual PHI is immediately used in another PHI node. */
330 if_convertible_phi_p (struct loop *loop, basic_block bb, tree phi)
332 if (dump_file && (dump_flags & TDF_DETAILS))
334 fprintf (dump_file, "-------------------------\n");
335 print_generic_stmt (dump_file, phi, TDF_SLIM);
338 if (bb != loop->header && PHI_NUM_ARGS (phi) != 2)
340 if (dump_file && (dump_flags & TDF_DETAILS))
341 fprintf (dump_file, "More than two phi node args.\n");
345 if (!is_gimple_reg (SSA_NAME_VAR (PHI_RESULT (phi))))
348 dataflow_t df = get_immediate_uses (phi);
349 int num_uses = num_immediate_uses (df);
350 for (j = 0; j < num_uses; j++)
352 tree use = immediate_use (df, j);
353 if (TREE_CODE (use) == PHI_NODE)
355 if (dump_file && (dump_flags & TDF_DETAILS))
356 fprintf (dump_file, "Difficult to handle this virtual phi.\n");
365 /* Return true, if M_EXPR is if-convertible.
366 MODIFY_EXPR is not if-convertible if,
369 - LHS is not var decl.
370 MODIFY_EXPR is part of block BB, which is inside loop LOOP.
374 if_convertible_modify_expr_p (struct loop *loop, basic_block bb, tree m_expr)
376 if (dump_file && (dump_flags & TDF_DETAILS))
378 fprintf (dump_file, "-------------------------\n");
379 print_generic_stmt (dump_file, m_expr, TDF_SLIM);
382 /* Be conservative and do not handle immovable expressions. */
383 if (movement_possibility (m_expr) == MOVE_IMPOSSIBLE)
385 if (dump_file && (dump_flags & TDF_DETAILS))
386 fprintf (dump_file, "stmt is movable. Don't take risk\n");
390 /* See if it needs speculative loading or not. */
391 if (bb != loop->header
392 && tree_could_trap_p (TREE_OPERAND (m_expr, 1)))
394 if (dump_file && (dump_flags & TDF_DETAILS))
395 fprintf (dump_file, "tree could trap...\n");
399 if (TREE_CODE (TREE_OPERAND (m_expr, 1)) == CALL_EXPR)
401 if (dump_file && (dump_flags & TDF_DETAILS))
402 fprintf (dump_file, "CALL_EXPR \n");
406 if (TREE_CODE (TREE_OPERAND (m_expr, 0)) != SSA_NAME
407 && bb != loop->header
408 && !bb_with_exit_edge_p (bb))
410 if (dump_file && (dump_flags & TDF_DETAILS))
412 fprintf (dump_file, "LHS is not var\n");
413 print_generic_stmt (dump_file, m_expr, TDF_SLIM);
422 /* Return true, iff STMT is if-convertible.
423 Statement is if-convertible if,
424 - It is if-convertible MODIFY_EXPR
425 - IT is LABEL_EXPR, GOTO_EXPR or COND_EXPR.
426 STMT is inside block BB, which is inside loop LOOP. */
429 if_convertible_stmt_p (struct loop *loop, basic_block bb, tree stmt)
431 switch (TREE_CODE (stmt))
438 if (!if_convertible_modify_expr_p (loop, bb, stmt))
447 /* Don't know what to do with 'em so don't do anything. */
448 if (dump_file && (dump_flags & TDF_DETAILS))
450 fprintf (dump_file, "don't know what to do\n");
451 print_generic_stmt (dump_file, stmt, TDF_SLIM);
460 /* Return true, iff BB is if-convertible.
461 Note: This routine does _not_ check basic block statements and phis.
462 Basic block is not if-convertible if,
463 - Basic block is non-empty and it is after exit block (in BFS order).
464 - Basic block is after exit block but before latch.
465 - Basic block edge(s) is not normal.
466 EXIT_BB_SEEN is true if basic block with exit edge is already seen.
467 BB is inside loop LOOP. */
470 if_convertible_bb_p (struct loop *loop, basic_block bb, bool exit_bb_seen)
475 if (dump_file && (dump_flags & TDF_DETAILS))
476 fprintf (dump_file, "----------[%d]-------------\n", bb->index);
480 if (bb != loop->latch)
482 if (dump_file && (dump_flags & TDF_DETAILS))
483 fprintf (dump_file, "basic block after exit bb but before latch\n");
486 else if (!empty_block_p (bb))
488 if (dump_file && (dump_flags & TDF_DETAILS))
489 fprintf (dump_file, "non empty basic block after exit bb\n");
494 /* Be less adventurous and handle only normal edges. */
495 FOR_EACH_EDGE (e, ei, bb->succs)
497 (EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
499 if (dump_file && (dump_flags & TDF_DETAILS))
500 fprintf (dump_file,"Difficult to handle edges\n");
507 /* Return true, iff LOOP is if-convertible.
508 LOOP is if-convertible if,
510 - It has two or more basic blocks.
511 - It has only one exit.
512 - Loop header is not the exit edge.
513 - If its basic blocks and phi nodes are if convertible. See above for
515 FOR_VECTORIZER enables vectorizer specific checks. For example, support
516 for vector conditions, data dependency checks etc.. (Not implemented yet). */
519 if_convertible_loop_p (struct loop *loop, bool for_vectorizer ATTRIBUTE_UNUSED)
523 block_stmt_iterator itr;
527 bool exit_bb_seen = false;
529 /* Handle only inner most loop. */
530 if (!loop || loop->inner)
532 if (dump_file && (dump_flags & TDF_DETAILS))
533 fprintf (dump_file, "not inner most loop\n");
537 flow_loop_scan (loop, LOOP_ALL);
539 /* If only one block, no need for if-conversion. */
540 if (loop->num_nodes <= 2)
542 if (dump_file && (dump_flags & TDF_DETAILS))
543 fprintf (dump_file, "less than 2 basic blocks\n");
547 /* More than one loop exit is too much to handle. */
548 if (loop->num_exits > 1)
550 if (dump_file && (dump_flags & TDF_DETAILS))
551 fprintf (dump_file, "multiple exits\n");
555 /* ??? Check target's vector conditional operation support for vectorizer. */
557 /* If one of the loop header's edge is exit edge then do not apply
559 FOR_EACH_EDGE (e, ei, loop->header->succs)
560 if ( e->flags & EDGE_LOOP_EXIT)
563 compute_immediate_uses (TDFA_USE_OPS|TDFA_USE_VOPS, NULL);
565 calculate_dominance_info (CDI_DOMINATORS);
566 calculate_dominance_info (CDI_POST_DOMINATORS);
568 /* Allow statements that can be handled during if-conversion. */
569 ifc_bbs = get_loop_body_in_if_conv_order (loop);
572 if (dump_file && (dump_flags & TDF_DETAILS))
573 fprintf (dump_file,"Irreducible loop\n");
574 free_dominance_info (CDI_POST_DOMINATORS);
578 for (i = 0; i < loop->num_nodes; i++)
582 if (!if_convertible_bb_p (loop, bb, exit_bb_seen))
585 /* Check statements. */
586 for (itr = bsi_start (bb); !bsi_end_p (itr); bsi_next (&itr))
587 if (!if_convertible_stmt_p (loop, bb, bsi_stmt (itr)))
589 /* ??? Check data dependency for vectorizer. */
591 /* What about phi nodes ? */
592 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
593 if (!if_convertible_phi_p (loop, bb, phi))
596 if (bb_with_exit_edge_p (bb))
600 /* OK. Did not find any potential issues so go ahead in if-convert
601 this loop. Now there is no looking back. */
603 fprintf (dump_file,"Applying if-conversion\n");
605 free_dominance_info (CDI_POST_DOMINATORS);
609 /* Add condition COND into predicate list of basic block BB. */
612 add_to_predicate_list (basic_block bb, tree new_cond)
617 cond = fold (build (TRUTH_OR_EXPR, boolean_type_node,
618 unshare_expr (cond), new_cond));
625 /* Add condition COND into BB's predicate list. PREV_COND is
626 existing condition. */
629 add_to_dst_predicate_list (struct loop * loop, basic_block bb,
630 tree prev_cond, tree cond,
631 block_stmt_iterator *bsi)
633 tree new_cond = NULL_TREE;
635 if (!flow_bb_inside_loop_p (loop, bb))
638 if (prev_cond == boolean_true_node || !prev_cond)
639 new_cond = unshare_expr (cond);
643 /* new_cond == prev_cond AND cond */
644 tree tmp = build (TRUTH_AND_EXPR, boolean_type_node,
645 unshare_expr (prev_cond), cond);
646 tmp_stmt = ifc_temp_var (boolean_type_node, tmp);
647 bsi_insert_before (bsi, tmp_stmt, BSI_SAME_STMT);
648 new_cond = TREE_OPERAND (tmp_stmt, 0);
650 add_to_predicate_list (bb, new_cond);
654 /* During if-conversion aux field from basic block is used to hold predicate
655 list. Clean each basic block's predicate list for the given LOOP. */
658 clean_predicate_lists (struct loop *loop)
662 bb = get_loop_body (loop);
663 for (i = 0; i < loop->num_nodes; i++)
669 /* Basic block BB has two predecessors. Using predecessor's aux field, set
670 appropriate condition COND for the PHI node replacement. Return true block
671 whose phi arguments are selected when cond is true. */
674 find_phi_replacement_condition (basic_block bb, tree *cond,
675 block_stmt_iterator *bsi)
678 basic_block p1 = NULL;
679 basic_block p2 = NULL;
680 basic_block true_bb = NULL;
684 FOR_EACH_EDGE (e, ei, bb->preds)
695 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
697 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
708 /* Create temp. for the condition. Vectorizer prefers to have gimple
709 value as condition. Various targets use different means to communicate
710 condition in vector compare operation. Using gimple value allows compiler
711 to emit vector compare and select RTL without exposing compare's result. */
712 if (!is_gimple_reg (*cond) && !is_gimple_condexpr (*cond))
716 new_stmt = ifc_temp_var (TREE_TYPE (*cond), unshare_expr (*cond));
717 bsi_insert_after (bsi, new_stmt, BSI_SAME_STMT);
719 *cond = TREE_OPERAND (new_stmt, 0);
728 /* Replace PHI node with conditional modify expr using COND.
729 This routine does not handle PHI nodes with more than two arguments.
731 S1: A = PHI <x1(1), x2(5)
733 S2: A = cond ? x1 : x2;
734 S2 is inserted at the top of basic block's statement list.
735 When COND is true, phi arg from TRUE_BB is selected.
739 replace_phi_with_cond_modify_expr (tree phi, tree cond, basic_block true_bb,
740 block_stmt_iterator *bsi)
747 gcc_assert (TREE_CODE (phi) == PHI_NODE);
749 /* If this is not filtered earlier, then now it is too late. */
750 gcc_assert (PHI_NUM_ARGS (phi) == 2);
752 /* Find basic block and initialize iterator. */
753 bb = bb_for_stmt (phi);
755 new_stmt = NULL_TREE;
759 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
760 if (EDGE_PRED (bb, 1)->src == true_bb)
762 arg_0 = PHI_ARG_DEF (phi, 1);
763 arg_1 = PHI_ARG_DEF (phi, 0);
767 arg_0 = PHI_ARG_DEF (phi, 0);
768 arg_1 = PHI_ARG_DEF (phi, 1);
771 /* Build new RHS using selected condition and arguments. */
772 rhs = build (COND_EXPR, TREE_TYPE (PHI_RESULT (phi)),
773 unshare_expr (cond), unshare_expr (arg_0),
774 unshare_expr (arg_1));
776 /* Create new MODIFY expression using RHS. */
777 new_stmt = build (MODIFY_EXPR, TREE_TYPE (PHI_RESULT (phi)),
778 unshare_expr (PHI_RESULT (phi)), rhs);
780 /* Make new statement definition of the original phi result. */
781 SSA_NAME_DEF_STMT (PHI_RESULT (phi)) = new_stmt;
783 /* Set basic block and insert using iterator. */
784 set_bb_for_stmt (new_stmt, bb);
786 bsi_insert_after (bsi, new_stmt, BSI_SAME_STMT);
789 modify_stmt (new_stmt);
791 if (dump_file && (dump_flags & TDF_DETAILS))
793 fprintf (dump_file, "new phi replacement stmt\n");
794 print_generic_stmt (dump_file, new_stmt, TDF_SLIM);
798 /* Process phi nodes for the given LOOP. Replace phi nodes with cond
802 process_phi_nodes (struct loop *loop)
805 unsigned int orig_loop_num_nodes = loop->num_nodes;
808 /* Replace phi nodes with cond. modify expr. */
809 for (i = 1; i < orig_loop_num_nodes; i++)
812 block_stmt_iterator bsi;
813 basic_block true_bb = NULL;
816 if (bb == loop->header)
819 phi = phi_nodes (bb);
820 bsi = bsi_start (bb);
822 /* BB has two predecessors. Using predecessor's aux field, set
823 appropriate condition for the PHI node replacement. */
825 true_bb = find_phi_replacement_condition (bb, &cond, &bsi);
829 tree next = PHI_CHAIN (phi);
830 replace_phi_with_cond_modify_expr (phi, cond, true_bb, &bsi);
831 release_phi_node (phi);
834 bb_ann (bb)->phi_nodes = NULL;
839 /* Combine all basic block from the given LOOP into one or two super
840 basic block. Replace PHI nodes with conditional modify expression. */
843 combine_blocks (struct loop *loop)
845 basic_block bb, exit_bb, merge_target_bb;
846 unsigned int orig_loop_num_nodes = loop->num_nodes;
849 /* Process phi nodes to prepare blocks for merge. */
850 process_phi_nodes (loop);
854 /* Merge basic blocks */
855 merge_target_bb = loop->header;
856 for (i = 1; i < orig_loop_num_nodes; i++)
859 block_stmt_iterator bsi;
860 tree_stmt_iterator last;
864 if (!exit_bb && bb_with_exit_edge_p (bb))
872 /* Connect this node with loop header. */
873 new_e = make_edge (ifc_bbs[0], bb, EDGE_FALLTHRU);
874 set_immediate_dominator (CDI_DOMINATORS, bb, ifc_bbs[0]);
876 if (exit_bb != loop->latch)
878 /* Redirect non-exit edge to loop->latch. */
879 FOR_EACH_EDGE (e, ei, bb->succs)
880 if (!(e->flags & EDGE_LOOP_EXIT))
882 redirect_edge_and_branch (e, loop->latch);
883 set_immediate_dominator (CDI_DOMINATORS, loop->latch, bb);
889 if (bb == loop->latch && empty_block_p (bb))
892 /* It is time to remove this basic block. First remove edges. */
893 while (EDGE_COUNT (bb->succs) > 0)
894 remove_edge (EDGE_SUCC (bb, 0));
895 while (EDGE_COUNT (bb->preds) > 0)
896 remove_edge (EDGE_PRED (bb, 0));
898 /* Remove labels and make stmts member of loop->header. */
899 for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
901 if (TREE_CODE (bsi_stmt (bsi)) == LABEL_EXPR)
905 set_bb_for_stmt (bsi_stmt (bsi), merge_target_bb);
910 /* Update stmt list. */
911 last = tsi_last (merge_target_bb->stmt_list);
912 tsi_link_after (&last, bb->stmt_list, TSI_NEW_STMT);
913 bb->stmt_list = NULL;
915 /* Update dominator info. */
916 if (dom_computed[CDI_DOMINATORS])
917 delete_from_dominance_info (CDI_DOMINATORS, bb);
918 if (dom_computed[CDI_POST_DOMINATORS])
919 delete_from_dominance_info (CDI_POST_DOMINATORS, bb);
921 /* Remove basic block. */
922 if (bb == loop->latch)
923 loop->latch = merge_target_bb;
924 remove_bb_from_loops (bb);
928 /* Now if possible, merge loop header and block with exit edge.
929 This reduces number of basic blocks to 2. Auto vectorizer addresses
930 loops with two nodes only. FIXME: Use cleanup_tree_cfg(). */
932 && loop->header != loop->latch
933 && exit_bb != loop->latch
934 && empty_block_p (loop->latch))
936 if (can_merge_blocks_p (loop->header, exit_bb))
938 remove_bb_from_loops (exit_bb);
939 merge_blocks (loop->header, exit_bb);
944 /* Make new temp variable of type TYPE. Add MODIFY_EXPR to assign EXP
945 to the new variable. */
948 ifc_temp_var (tree type, tree exp)
950 const char *name = "_ifc_";
951 tree var, stmt, new_name;
953 if (is_gimple_reg (exp))
956 /* Create new temporary variable. */
957 var = create_tmp_var (type, name);
958 add_referenced_tmp_var (var);
960 /* Build new statement to assign EXP to new variable. */
961 stmt = build (MODIFY_EXPR, type, var, exp);
963 /* Get SSA name for the new variable and set make new statement
964 its definition statment. */
965 new_name = make_ssa_name (var, stmt);
966 TREE_OPERAND (stmt, 0) = new_name;
967 SSA_NAME_DEF_STMT (new_name) = stmt;
973 /* Return TRUE iff, all pred blocks of BB are visited.
974 Bitmap VISITED keeps history of visited blocks. */
977 pred_blocks_visited_p (basic_block bb, bitmap *visited)
981 FOR_EACH_EDGE (e, ei, bb->preds)
982 if (!bitmap_bit_p (*visited, e->src->index))
988 /* Get body of a LOOP in suitable order for if-conversion.
989 It is caller's responsibility to deallocate basic block
990 list. If-conversion suitable order is, BFS order with one
991 additional constraint. Select block in BFS block, if all
992 pred are already selected. */
995 get_loop_body_in_if_conv_order (const struct loop *loop)
997 basic_block *blocks, *blocks_in_bfs_order;
1000 unsigned int index = 0;
1001 unsigned int visited_count = 0;
1003 gcc_assert (loop->num_nodes);
1004 gcc_assert (loop->latch != EXIT_BLOCK_PTR);
1006 blocks = xcalloc (loop->num_nodes, sizeof (basic_block));
1007 visited = BITMAP_XMALLOC ();
1009 blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
1012 while (index < loop->num_nodes)
1014 bb = blocks_in_bfs_order [index];
1016 if (bb->flags & BB_IRREDUCIBLE_LOOP)
1018 free (blocks_in_bfs_order);
1019 BITMAP_XFREE (visited);
1023 if (!bitmap_bit_p (visited, bb->index))
1025 if (pred_blocks_visited_p (bb, &visited)
1026 || bb == loop->header)
1028 /* This block is now visited. */
1029 bitmap_set_bit (visited, bb->index);
1030 blocks[visited_count++] = bb;
1034 if (index == loop->num_nodes
1035 && visited_count != loop->num_nodes)
1041 free (blocks_in_bfs_order);
1042 BITMAP_XFREE (visited);
1046 /* Return true if one of the basic block BB edge is loop exit. */
1049 bb_with_exit_edge_p (basic_block bb)
1053 bool exit_edge_found = false;
1055 FOR_EACH_EDGE (e, ei, bb->succs)
1056 if (e->flags & EDGE_LOOP_EXIT)
1058 exit_edge_found = true;
1062 return exit_edge_found;
1065 /* Tree if-conversion pass management. */
1068 main_tree_if_conversion (void)
1070 unsigned i, loop_num;
1076 loop_num = current_loops->num;
1077 for (i = 0; i < loop_num; i++)
1079 loop = current_loops->parray[i];
1083 tree_if_conversion (loop, true);
1089 gate_tree_if_conversion (void)
1091 return flag_tree_vectorize != 0;
1094 struct tree_opt_pass pass_if_conversion =
1097 gate_tree_if_conversion, /* gate */
1098 main_tree_if_conversion, /* execute */
1101 0, /* static_pass_number */
1103 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
1104 0, /* properties_provided */
1105 0, /* properties_destroyed */
1106 TODO_dump_func, /* todo_flags_start */
1110 | TODO_verify_flow, /* todo_flags_finish */