1 /* If-conversion for vectorizer.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
3 Free Software Foundation, Inc.
4 Contributed by Devang Patel <dpatel@apple.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
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"
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 /* List of basic blocks in if-conversion-suitable order. */
104 static basic_block *ifc_bbs;
106 /* Make a new temp variable of type TYPE. Add GIMPLE_ASSIGN to assign EXP
107 to the new variable. */
110 ifc_temp_var (tree type, tree exp)
112 const char *name = "_ifc_";
116 /* Create new temporary variable. */
117 var = create_tmp_var (type, name);
118 add_referenced_var (var);
120 /* Build new statement to assign EXP to new variable. */
121 stmt = gimple_build_assign (var, exp);
123 /* Get SSA name for the new variable and set make new statement
124 its definition statement. */
125 new_name = make_ssa_name (var, stmt);
126 gimple_assign_set_lhs (stmt, new_name);
127 SSA_NAME_DEF_STMT (new_name) = stmt;
133 /* Add condition NEW_COND into predicate list of basic block BB. */
136 add_to_predicate_list (basic_block bb, tree new_cond)
138 tree cond = (tree) bb->aux;
141 cond = fold_build2_loc (EXPR_LOCATION (cond),
142 TRUTH_OR_EXPR, boolean_type_node,
143 unshare_expr (cond), new_cond);
150 /* And condition COND to the previous condition PREV_COND and add this
151 to the predicate list of the destination of edge E. GSI is the
152 place where the gimplification of the resulting condition should
153 output code. LOOP is the loop to be if-converted. */
156 add_to_dst_predicate_list (struct loop *loop, edge e,
157 tree prev_cond, tree cond,
158 gimple_stmt_iterator *gsi)
160 tree new_cond = NULL_TREE;
162 if (!flow_bb_inside_loop_p (loop, e->dest))
165 if (prev_cond == boolean_true_node || !prev_cond)
166 new_cond = unshare_expr (cond);
170 gimple tmp_stmt = NULL;
172 prev_cond = force_gimple_operand_gsi (gsi, unshare_expr (prev_cond),
173 true, NULL, true, GSI_SAME_STMT);
175 cond = force_gimple_operand_gsi (gsi, unshare_expr (cond),
176 true, NULL, true, GSI_SAME_STMT);
178 /* Add the condition to aux field of the edge. In case edge
179 destination is a PHI node, this condition will be ANDed with
180 block predicate to construct complete condition. */
183 tmp = build2 (TRUTH_AND_EXPR, boolean_type_node,
184 unshare_expr (prev_cond), cond);
185 tmp_stmt = ifc_temp_var (boolean_type_node, tmp);
186 gsi_insert_before (gsi, tmp_stmt, GSI_SAME_STMT);
187 new_cond = gimple_assign_lhs (tmp_stmt);
190 add_to_predicate_list (e->dest, new_cond);
194 /* Return true if one of the basic block BB edge is exit of LOOP. */
197 bb_with_exit_edge_p (struct loop *loop, basic_block bb)
201 bool exit_edge_found = false;
203 FOR_EACH_EDGE (e, ei, bb->succs)
204 if (loop_exit_edge_p (loop, e))
206 exit_edge_found = true;
210 return exit_edge_found;
213 /* STMT is a GIMPLE_COND. Update two destination's predicate list.
214 Remove COND_EXPR, if it is not the loop exit condition. Otherwise
215 update loop exit condition appropriately. GSI is the iterator
216 used to traverse statement list. STMT is part of loop LOOP. */
219 tree_if_convert_cond_stmt (struct loop *loop, gimple stmt, tree cond,
220 gimple_stmt_iterator *gsi)
223 edge true_edge, false_edge;
224 location_t loc = gimple_location (stmt);
225 tree c = fold_build2_loc (loc, gimple_cond_code (stmt), boolean_type_node,
226 gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
228 extract_true_false_edges_from_block (gimple_bb (stmt),
229 &true_edge, &false_edge);
231 /* Add new condition into destination's predicate list. */
233 /* If C is true, then TRUE_EDGE is taken. */
234 add_to_dst_predicate_list (loop, true_edge, cond, c, gsi);
236 /* If C is false, then FALSE_EDGE is taken. */
237 c2 = invert_truthvalue_loc (loc, unshare_expr (c));
238 add_to_dst_predicate_list (loop, false_edge, cond, c2, gsi);
240 /* Now this conditional statement is redundant. Remove it.
241 But, do not remove exit condition! Update exit condition
242 using new condition. */
243 if (!bb_with_exit_edge_p (loop, gimple_bb (stmt)))
245 gsi_remove (gsi, true);
251 /* If-convert stmt T which is part of LOOP.
252 If T is a GIMPLE_ASSIGN then it is converted into conditional modify
253 expression using COND. For conditional expressions, add condition in the
254 destination basic block's predicate list and remove conditional
255 expression itself. BSI is the iterator used to traverse statements of
256 loop. It is used here when it is required to delete current statement. */
259 tree_if_convert_stmt (struct loop *loop, gimple t, tree cond,
260 gimple_stmt_iterator *gsi)
262 if (dump_file && (dump_flags & TDF_DETAILS))
264 fprintf (dump_file, "------if-convert stmt\n");
265 print_gimple_stmt (dump_file, t, 0, TDF_SLIM);
266 print_generic_stmt (dump_file, cond, TDF_SLIM);
269 switch (gimple_code (t))
271 /* Labels are harmless here. */
276 /* ??? Should there be conditional GIMPLE_DEBUG_BINDs? */
277 if (gimple_debug_bind_p (gsi_stmt (*gsi)))
279 gimple_debug_bind_reset_value (gsi_stmt (*gsi));
280 update_stmt (gsi_stmt (*gsi));
285 /* This GIMPLE_ASSIGN is killing previous value of LHS. Appropriate
286 value will be selected by PHI node based on condition. It is possible
287 that before this transformation, PHI nodes was selecting default
288 value and now it will use this new value. This is OK because it does
289 not change the validity of the program. */
293 /* Update destination blocks' predicate list and remove this
294 condition expression. */
295 tree_if_convert_cond_stmt (loop, t, cond, gsi);
305 /* Return true, iff PHI is if-convertible. PHI is part of loop LOOP
306 and it belongs to basic block BB.
307 PHI is not if-convertible
308 - if it has more than 2 arguments,
309 - virtual PHI is immediately used in another PHI node,
310 - virtual PHI on BB other than header. */
313 if_convertible_phi_p (struct loop *loop, basic_block bb, gimple phi)
315 if (dump_file && (dump_flags & TDF_DETAILS))
317 fprintf (dump_file, "-------------------------\n");
318 print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
321 if (bb != loop->header && gimple_phi_num_args (phi) != 2)
323 if (dump_file && (dump_flags & TDF_DETAILS))
324 fprintf (dump_file, "More than two phi node args.\n");
328 if (!is_gimple_reg (SSA_NAME_VAR (gimple_phi_result (phi))))
330 imm_use_iterator imm_iter;
333 if (bb != loop->header)
335 if (dump_file && (dump_flags & TDF_DETAILS))
336 fprintf (dump_file, "Virtual phi not on loop header.\n");
339 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_phi_result (phi))
341 if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI)
343 if (dump_file && (dump_flags & TDF_DETAILS))
344 fprintf (dump_file, "Difficult to handle this virtual phi.\n");
353 /* Return true, if STMT is if-convertible.
354 GIMPLE_ASSIGN statement is not if-convertible if,
357 - LHS is not var decl.
358 GIMPLE_ASSIGN is part of block BB, which is inside loop LOOP. */
361 if_convertible_gimple_assign_stmt_p (struct loop *loop, basic_block bb,
366 if (!is_gimple_assign (stmt))
369 if (dump_file && (dump_flags & TDF_DETAILS))
371 fprintf (dump_file, "-------------------------\n");
372 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
375 lhs = gimple_assign_lhs (stmt);
377 /* Some of these constrains might be too conservative. */
378 if (stmt_ends_bb_p (stmt)
379 || gimple_has_volatile_ops (stmt)
380 || (TREE_CODE (lhs) == SSA_NAME
381 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
382 || gimple_has_side_effects (stmt))
384 if (dump_file && (dump_flags & TDF_DETAILS))
385 fprintf (dump_file, "stmt not suitable for ifcvt\n");
389 /* See if it needs speculative loading or not. */
390 if (bb != loop->header
391 && gimple_assign_rhs_could_trap_p (stmt))
393 if (dump_file && (dump_flags & TDF_DETAILS))
394 fprintf (dump_file, "tree could trap...\n");
398 if (TREE_CODE (lhs) != SSA_NAME
399 && bb != loop->header
400 && !bb_with_exit_edge_p (loop, bb))
402 if (dump_file && (dump_flags & TDF_DETAILS))
404 fprintf (dump_file, "LHS is not var\n");
405 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
413 /* Return true, iff STMT is if-convertible.
414 Statement is if-convertible if,
415 - it is if-convertible GIMPLE_ASSGIN,
416 - it is GIMPLE_LABEL or GIMPLE_COND.
417 STMT is inside block BB, which is inside loop LOOP. */
420 if_convertible_stmt_p (struct loop *loop, basic_block bb, gimple stmt)
422 switch (gimple_code (stmt))
431 if (!if_convertible_gimple_assign_stmt_p (loop, bb, stmt))
439 /* Don't know what to do with 'em so don't do anything. */
440 if (dump_file && (dump_flags & TDF_DETAILS))
442 fprintf (dump_file, "don't know what to do\n");
443 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
452 /* Return true, iff BB is if-convertible.
453 Note: This routine does _not_ check basic block statements and phis.
454 Basic block is not if-convertible if:
455 - basic block is non-empty and it is after exit block (in BFS order),
456 - basic block is after exit block but before latch,
457 - basic block edge(s) is not normal.
458 EXIT_BB_SEEN is true if basic block with exit edge is already seen.
459 BB is inside loop LOOP. */
462 if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
467 if (dump_file && (dump_flags & TDF_DETAILS))
468 fprintf (dump_file, "----------[%d]-------------\n", bb->index);
472 if (bb != loop->latch)
474 if (dump_file && (dump_flags & TDF_DETAILS))
475 fprintf (dump_file, "basic block after exit bb but before latch\n");
478 else if (!empty_block_p (bb))
480 if (dump_file && (dump_flags & TDF_DETAILS))
481 fprintf (dump_file, "non empty basic block after exit bb\n");
484 else if (bb == loop->latch
486 && !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
488 if (dump_file && (dump_flags & TDF_DETAILS))
489 fprintf (dump_file, "latch is not dominated by exit_block\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, all pred blocks of BB are visited.
508 Bitmap VISITED keeps history of visited blocks. */
511 pred_blocks_visited_p (basic_block bb, bitmap *visited)
515 FOR_EACH_EDGE (e, ei, bb->preds)
516 if (!bitmap_bit_p (*visited, e->src->index))
522 /* Get body of a LOOP in suitable order for if-conversion. It is
523 caller's responsibility to deallocate basic block list.
524 If-conversion suitable order is, breadth first sort (BFS) order
525 with an additional constraint: select a block only if all its
526 predecessors are already selected. */
529 get_loop_body_in_if_conv_order (const struct loop *loop)
531 basic_block *blocks, *blocks_in_bfs_order;
534 unsigned int index = 0;
535 unsigned int visited_count = 0;
537 gcc_assert (loop->num_nodes);
538 gcc_assert (loop->latch != EXIT_BLOCK_PTR);
540 blocks = XCNEWVEC (basic_block, loop->num_nodes);
541 visited = BITMAP_ALLOC (NULL);
543 blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
546 while (index < loop->num_nodes)
548 bb = blocks_in_bfs_order [index];
550 if (bb->flags & BB_IRREDUCIBLE_LOOP)
552 free (blocks_in_bfs_order);
553 BITMAP_FREE (visited);
558 if (!bitmap_bit_p (visited, bb->index))
560 if (pred_blocks_visited_p (bb, &visited)
561 || bb == loop->header)
563 /* This block is now visited. */
564 bitmap_set_bit (visited, bb->index);
565 blocks[visited_count++] = bb;
571 if (index == loop->num_nodes
572 && visited_count != loop->num_nodes)
576 free (blocks_in_bfs_order);
577 BITMAP_FREE (visited);
581 /* Return true, iff LOOP is if-convertible.
582 LOOP is if-convertible if:
584 - it has two or more basic blocks,
585 - it has only one exit,
586 - loop header is not the exit edge,
587 - if its basic blocks and phi nodes are if convertible. */
590 if_convertible_loop_p (struct loop *loop)
593 gimple_stmt_iterator itr;
597 basic_block exit_bb = NULL;
599 /* Handle only inner most loop. */
600 if (!loop || loop->inner)
602 if (dump_file && (dump_flags & TDF_DETAILS))
603 fprintf (dump_file, "not inner most loop\n");
607 /* If only one block, no need for if-conversion. */
608 if (loop->num_nodes <= 2)
610 if (dump_file && (dump_flags & TDF_DETAILS))
611 fprintf (dump_file, "less than 2 basic blocks\n");
615 /* More than one loop exit is too much to handle. */
616 if (!single_exit (loop))
618 if (dump_file && (dump_flags & TDF_DETAILS))
619 fprintf (dump_file, "multiple exits\n");
623 /* ??? Check target's vector conditional operation support for vectorizer. */
625 /* If one of the loop header's edge is exit edge then do not apply
627 FOR_EACH_EDGE (e, ei, loop->header->succs)
629 if (loop_exit_edge_p (loop, e))
633 calculate_dominance_info (CDI_DOMINATORS);
634 calculate_dominance_info (CDI_POST_DOMINATORS);
636 /* Allow statements that can be handled during if-conversion. */
637 ifc_bbs = get_loop_body_in_if_conv_order (loop);
640 if (dump_file && (dump_flags & TDF_DETAILS))
641 fprintf (dump_file,"Irreducible loop\n");
642 free_dominance_info (CDI_POST_DOMINATORS);
646 for (i = 0; i < loop->num_nodes; i++)
650 if (!if_convertible_bb_p (loop, bb, exit_bb))
653 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
654 if (!if_convertible_stmt_p (loop, bb, gsi_stmt (itr)))
657 itr = gsi_start_phis (bb);
659 if (!gsi_end_p (itr))
660 FOR_EACH_EDGE (e, ei, bb->preds)
663 for (; !gsi_end_p (itr); gsi_next (&itr))
664 if (!if_convertible_phi_p (loop, bb, gsi_stmt (itr)))
667 if (bb_with_exit_edge_p (loop, bb))
672 fprintf (dump_file,"Applying if-conversion\n");
674 free_dominance_info (CDI_POST_DOMINATORS);
678 /* During if-conversion aux field from basic block structure is used to hold
679 predicate list. Clean each basic block's predicate list for the given LOOP.
680 Also clean aux field of successor edges, used to hold true and false
681 condition from conditional expression. */
684 clean_predicate_lists (struct loop *loop)
691 bb = get_loop_body (loop);
692 for (i = 0; i < loop->num_nodes; i++)
695 FOR_EACH_EDGE (e, ei, bb[i]->succs)
701 /* Basic block BB has two predecessors. Using predecessor's aux field, set
702 appropriate condition COND for the PHI node replacement. Return true block
703 whose phi arguments are selected when cond is true. */
706 find_phi_replacement_condition (struct loop *loop,
707 basic_block bb, tree *cond,
708 gimple_stmt_iterator *gsi)
710 edge first_edge, second_edge;
713 gcc_assert (EDGE_COUNT (bb->preds) == 2);
714 first_edge = EDGE_PRED (bb, 0);
715 second_edge = EDGE_PRED (bb, 1);
717 /* Use condition based on following criteria:
723 S2 is preferred over S1. Make 'b' first_bb and use its condition.
725 2) Do not make loop header first_bb.
728 S1: x = !(c == d)? a : b;
733 S3: x = (c == d) ? b : a;
735 S3 is preferred over S1 and S2*, Make 'b' first_bb and use
738 4) If pred B is dominated by pred A then use pred B's condition.
741 /* Select condition that is not TRUTH_NOT_EXPR. */
742 tmp_cond = (tree) (first_edge->src)->aux;
743 gcc_assert (tmp_cond);
745 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
749 tmp_edge = first_edge;
750 first_edge = second_edge;
751 second_edge = tmp_edge;
754 /* Check if FIRST_BB is loop header or not and make sure that
755 FIRST_BB does not dominate SECOND_BB. */
756 if (first_edge->src == loop->header
757 || dominated_by_p (CDI_DOMINATORS,
758 second_edge->src, first_edge->src))
760 *cond = (tree) (second_edge->src)->aux;
762 /* If there is a condition on an incoming edge,
763 AND it with the incoming bb predicate. */
764 if (second_edge->aux)
765 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
766 *cond, (tree) second_edge->aux);
768 if (TREE_CODE (*cond) == TRUTH_NOT_EXPR)
769 /* We can be smart here and choose inverted
770 condition without switching bbs. */
771 *cond = invert_truthvalue (*cond);
773 /* Select non loop header bb. */
774 first_edge = second_edge;
778 /* FIRST_BB is not loop header */
779 *cond = (tree) (first_edge->src)->aux;
781 /* If there is a condition on an incoming edge,
782 AND it with the incoming bb predicate. */
784 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
785 *cond, (tree) first_edge->aux);
788 /* Create temp. for the condition. Vectorizer prefers to have gimple
789 value as condition. Various targets use different means to communicate
790 condition in vector compare operation. Using gimple value allows
791 compiler to emit vector compare and select RTL without exposing
793 *cond = force_gimple_operand_gsi (gsi, unshare_expr (*cond),
795 true, GSI_SAME_STMT);
796 if (!is_gimple_reg (*cond) && !is_gimple_condexpr (*cond))
800 new_stmt = ifc_temp_var (TREE_TYPE (*cond), unshare_expr (*cond));
801 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
802 *cond = gimple_assign_lhs (new_stmt);
807 return first_edge->src;
811 /* Replace PHI node with conditional modify expr using COND.
812 This routine does not handle PHI nodes with more than two arguments.
814 S1: A = PHI <x1(1), x2(5)
816 S2: A = cond ? x1 : x2;
817 S2 is inserted at the top of basic block's statement list.
818 When COND is true, phi arg from TRUE_BB is selected.
822 replace_phi_with_cond_gimple_assign_stmt (gimple phi, tree cond,
824 gimple_stmt_iterator *gsi)
831 gcc_assert (gimple_code (phi) == GIMPLE_PHI);
833 /* If this is not filtered earlier, then now it is too late. */
834 gcc_assert (gimple_phi_num_args (phi) == 2);
836 /* Find basic block and initialize iterator. */
837 bb = gimple_bb (phi);
839 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
840 if (EDGE_PRED (bb, 1)->src == true_bb)
842 arg_0 = gimple_phi_arg_def (phi, 1);
843 arg_1 = gimple_phi_arg_def (phi, 0);
847 arg_0 = gimple_phi_arg_def (phi, 0);
848 arg_1 = gimple_phi_arg_def (phi, 1);
851 /* Build new RHS using selected condition and arguments. */
852 rhs = build3 (COND_EXPR, TREE_TYPE (PHI_RESULT (phi)),
853 unshare_expr (cond), unshare_expr (arg_0),
854 unshare_expr (arg_1));
856 /* Create new GIMPLE_ASSIGN statement using RHS. */
857 new_stmt = gimple_build_assign (unshare_expr (PHI_RESULT (phi)), rhs);
859 /* Make new statement definition of the original phi result. */
860 SSA_NAME_DEF_STMT (gimple_phi_result (phi)) = new_stmt;
862 /* Insert using iterator. */
863 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
864 update_stmt (new_stmt);
866 if (dump_file && (dump_flags & TDF_DETAILS))
868 fprintf (dump_file, "new phi replacement stmt\n");
869 print_gimple_stmt (dump_file, new_stmt, 0, TDF_SLIM);
873 /* Process phi nodes for the given LOOP. Replace phi nodes with
874 conditional modify expressions. */
877 process_phi_nodes (struct loop *loop)
880 unsigned int orig_loop_num_nodes = loop->num_nodes;
883 for (i = 1; i < orig_loop_num_nodes; i++)
886 tree cond = NULL_TREE;
887 gimple_stmt_iterator gsi, phi_gsi;
888 basic_block true_bb = NULL;
891 if (bb == loop->header)
894 phi_gsi = gsi_start_phis (bb);
895 gsi = gsi_after_labels (bb);
897 /* BB has two predecessors. Using predecessor's aux field, set
898 appropriate condition for the PHI node replacement. */
899 if (!gsi_end_p (phi_gsi))
900 true_bb = find_phi_replacement_condition (loop, bb, &cond, &gsi);
902 while (!gsi_end_p (phi_gsi))
904 phi = gsi_stmt (phi_gsi);
905 replace_phi_with_cond_gimple_assign_stmt (phi, cond, true_bb, &gsi);
906 release_phi_node (phi);
909 set_phi_nodes (bb, NULL);
914 /* Combine all the basic blocks from LOOP into one or two super basic
915 blocks. Replace PHI nodes with conditional modify expressions. */
918 combine_blocks (struct loop *loop)
920 basic_block bb, exit_bb, merge_target_bb;
921 unsigned int orig_loop_num_nodes = loop->num_nodes;
926 /* Process phi nodes to prepare blocks for merge. */
927 process_phi_nodes (loop);
929 /* Merge basic blocks. First remove all the edges in the loop, except
930 for those from the exit block. */
932 for (i = 0; i < orig_loop_num_nodes; i++)
935 if (bb_with_exit_edge_p (loop, bb))
941 gcc_assert (exit_bb != loop->latch);
943 for (i = 1; i < orig_loop_num_nodes; i++)
947 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei));)
949 if (e->src == exit_bb)
958 if (exit_bb != loop->header)
960 /* Connect this node with loop header. */
961 make_edge (loop->header, exit_bb, EDGE_FALLTHRU);
962 set_immediate_dominator (CDI_DOMINATORS, exit_bb, loop->header);
965 /* Redirect non-exit edges to loop->latch. */
966 FOR_EACH_EDGE (e, ei, exit_bb->succs)
968 if (!loop_exit_edge_p (loop, e))
969 redirect_edge_and_branch (e, loop->latch);
971 set_immediate_dominator (CDI_DOMINATORS, loop->latch, exit_bb);
975 /* If the loop does not have exit then reconnect header and latch. */
976 make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
977 set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
980 merge_target_bb = loop->header;
981 for (i = 1; i < orig_loop_num_nodes; i++)
983 gimple_stmt_iterator gsi;
984 gimple_stmt_iterator last;
988 if (bb == exit_bb || bb == loop->latch)
991 /* Remove labels and make stmts member of loop->header. */
992 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
994 if (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL)
995 gsi_remove (&gsi, true);
998 gimple_set_bb (gsi_stmt (gsi), merge_target_bb);
1003 /* Update stmt list. */
1004 last = gsi_last_bb (merge_target_bb);
1005 gsi_insert_seq_after (&last, bb_seq (bb), GSI_NEW_STMT);
1006 set_bb_seq (bb, NULL);
1008 delete_basic_block (bb);
1011 /* Now if possible, merge loop header and block with exit edge.
1012 This reduces number of basic blocks to 2. Auto vectorizer addresses
1013 loops with two nodes only. FIXME: Use cleanup_tree_cfg(). */
1015 && exit_bb != loop->header
1016 && can_merge_blocks_p (loop->header, exit_bb))
1017 merge_blocks (loop->header, exit_bb);
1020 /* Main entry point. Apply if-conversion to the LOOP. Return true if
1021 successful otherwise return false. If false is returned then loop
1022 remains unchanged. */
1025 tree_if_conversion (struct loop *loop)
1028 gimple_stmt_iterator itr;
1033 /* If-conversion is not appropriate for all loops. First, check if
1034 loop is if-convertible or not. */
1035 if (!if_convertible_loop_p (loop))
1037 if (dump_file && (dump_flags & TDF_DETAILS))
1038 fprintf (dump_file,"-------------------------\n");
1044 free_dominance_info (CDI_POST_DOMINATORS);
1048 /* Do actual work now. */
1049 for (i = 0; i < loop->num_nodes; i++)
1055 /* Update condition using predicate list. */
1056 cond = (tree) bb->aux;
1058 /* Process all statements in this basic block.
1059 Remove conditional expression, if any, and annotate
1060 destination basic block(s) appropriately. */
1061 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); /* empty */)
1063 gimple t = gsi_stmt (itr);
1064 cond = tree_if_convert_stmt (loop, t, cond, &itr);
1065 if (!gsi_end_p (itr))
1069 /* If current bb has only one successor, then consider it as an
1070 unconditional goto. */
1071 if (single_succ_p (bb))
1073 basic_block bb_n = single_succ (bb);
1075 /* Successor bb inherits predicate of its predecessor. If there
1076 is no predicate in predecessor bb, then consider successor bb
1077 as always executed. */
1078 if (cond == NULL_TREE)
1079 cond = boolean_true_node;
1081 add_to_predicate_list (bb_n, cond);
1085 /* Now, all statements are if-converted and basic blocks are
1086 annotated appropriately. Combine all basic block into one huge
1088 combine_blocks (loop);
1091 clean_predicate_lists (loop);
1098 /* Tree if-conversion pass management. */
1101 main_tree_if_conversion (void)
1106 if (number_of_loops () <= 1)
1109 FOR_EACH_LOOP (li, loop, 0)
1110 tree_if_conversion (loop);
1116 gate_tree_if_conversion (void)
1118 return flag_tree_vectorize != 0;
1121 struct gimple_opt_pass pass_if_conversion =
1126 gate_tree_if_conversion, /* gate */
1127 main_tree_if_conversion, /* execute */
1130 0, /* static_pass_number */
1131 TV_NONE, /* tv_id */
1132 PROP_cfg | PROP_ssa, /* properties_required */
1133 0, /* properties_provided */
1134 0, /* properties_destroyed */
1135 0, /* todo_flags_start */
1136 TODO_dump_func | TODO_verify_stmts | TODO_verify_flow
1137 /* todo_flags_finish */