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. See above for
589 FOR_VECTORIZER enables vectorizer specific checks, for example, support
590 for vector conditions, data dependency checks, etc.
591 (Not implemented yet). */
594 if_convertible_loop_p (struct loop *loop, bool for_vectorizer ATTRIBUTE_UNUSED)
597 gimple_stmt_iterator itr;
601 basic_block exit_bb = NULL;
603 /* Handle only inner most loop. */
604 if (!loop || loop->inner)
606 if (dump_file && (dump_flags & TDF_DETAILS))
607 fprintf (dump_file, "not inner most loop\n");
611 /* If only one block, no need for if-conversion. */
612 if (loop->num_nodes <= 2)
614 if (dump_file && (dump_flags & TDF_DETAILS))
615 fprintf (dump_file, "less than 2 basic blocks\n");
619 /* More than one loop exit is too much to handle. */
620 if (!single_exit (loop))
622 if (dump_file && (dump_flags & TDF_DETAILS))
623 fprintf (dump_file, "multiple exits\n");
627 /* ??? Check target's vector conditional operation support for vectorizer. */
629 /* If one of the loop header's edge is exit edge then do not apply
631 FOR_EACH_EDGE (e, ei, loop->header->succs)
633 if (loop_exit_edge_p (loop, e))
637 calculate_dominance_info (CDI_DOMINATORS);
638 calculate_dominance_info (CDI_POST_DOMINATORS);
640 /* Allow statements that can be handled during if-conversion. */
641 ifc_bbs = get_loop_body_in_if_conv_order (loop);
644 if (dump_file && (dump_flags & TDF_DETAILS))
645 fprintf (dump_file,"Irreducible loop\n");
646 free_dominance_info (CDI_POST_DOMINATORS);
650 for (i = 0; i < loop->num_nodes; i++)
654 if (!if_convertible_bb_p (loop, bb, exit_bb))
657 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
658 if (!if_convertible_stmt_p (loop, bb, gsi_stmt (itr)))
661 itr = gsi_start_phis (bb);
663 if (!gsi_end_p (itr))
664 FOR_EACH_EDGE (e, ei, bb->preds)
667 for (; !gsi_end_p (itr); gsi_next (&itr))
668 if (!if_convertible_phi_p (loop, bb, gsi_stmt (itr)))
671 if (bb_with_exit_edge_p (loop, bb))
676 fprintf (dump_file,"Applying if-conversion\n");
678 free_dominance_info (CDI_POST_DOMINATORS);
682 /* During if-conversion aux field from basic block structure is used to hold
683 predicate list. Clean each basic block's predicate list for the given LOOP.
684 Also clean aux field of successor edges, used to hold true and false
685 condition from conditional expression. */
688 clean_predicate_lists (struct loop *loop)
695 bb = get_loop_body (loop);
696 for (i = 0; i < loop->num_nodes; i++)
699 FOR_EACH_EDGE (e, ei, bb[i]->succs)
705 /* Basic block BB has two predecessors. Using predecessor's aux field, set
706 appropriate condition COND for the PHI node replacement. Return true block
707 whose phi arguments are selected when cond is true. */
710 find_phi_replacement_condition (struct loop *loop,
711 basic_block bb, tree *cond,
712 gimple_stmt_iterator *gsi)
714 edge first_edge, second_edge;
717 gcc_assert (EDGE_COUNT (bb->preds) == 2);
718 first_edge = EDGE_PRED (bb, 0);
719 second_edge = EDGE_PRED (bb, 1);
721 /* Use condition based on following criteria:
727 S2 is preferred over S1. Make 'b' first_bb and use its condition.
729 2) Do not make loop header first_bb.
732 S1: x = !(c == d)? a : b;
737 S3: x = (c == d) ? b : a;
739 S3 is preferred over S1 and S2*, Make 'b' first_bb and use
742 4) If pred B is dominated by pred A then use pred B's condition.
745 /* Select condition that is not TRUTH_NOT_EXPR. */
746 tmp_cond = (tree) (first_edge->src)->aux;
747 gcc_assert (tmp_cond);
749 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
753 tmp_edge = first_edge;
754 first_edge = second_edge;
755 second_edge = tmp_edge;
758 /* Check if FIRST_BB is loop header or not and make sure that
759 FIRST_BB does not dominate SECOND_BB. */
760 if (first_edge->src == loop->header
761 || dominated_by_p (CDI_DOMINATORS,
762 second_edge->src, first_edge->src))
764 *cond = (tree) (second_edge->src)->aux;
766 /* If there is a condition on an incoming edge,
767 AND it with the incoming bb predicate. */
768 if (second_edge->aux)
769 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
770 *cond, (tree) second_edge->aux);
772 if (TREE_CODE (*cond) == TRUTH_NOT_EXPR)
773 /* We can be smart here and choose inverted
774 condition without switching bbs. */
775 *cond = invert_truthvalue (*cond);
777 /* Select non loop header bb. */
778 first_edge = second_edge;
782 /* FIRST_BB is not loop header */
783 *cond = (tree) (first_edge->src)->aux;
785 /* If there is a condition on an incoming edge,
786 AND it with the incoming bb predicate. */
788 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
789 *cond, (tree) first_edge->aux);
792 /* Create temp. for the condition. Vectorizer prefers to have gimple
793 value as condition. Various targets use different means to communicate
794 condition in vector compare operation. Using gimple value allows
795 compiler to emit vector compare and select RTL without exposing
797 *cond = force_gimple_operand_gsi (gsi, unshare_expr (*cond),
799 true, GSI_SAME_STMT);
800 if (!is_gimple_reg (*cond) && !is_gimple_condexpr (*cond))
804 new_stmt = ifc_temp_var (TREE_TYPE (*cond), unshare_expr (*cond));
805 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
806 *cond = gimple_assign_lhs (new_stmt);
811 return first_edge->src;
815 /* Replace PHI node with conditional modify expr using COND.
816 This routine does not handle PHI nodes with more than two arguments.
818 S1: A = PHI <x1(1), x2(5)
820 S2: A = cond ? x1 : x2;
821 S2 is inserted at the top of basic block's statement list.
822 When COND is true, phi arg from TRUE_BB is selected.
826 replace_phi_with_cond_gimple_assign_stmt (gimple phi, tree cond,
828 gimple_stmt_iterator *gsi)
835 gcc_assert (gimple_code (phi) == GIMPLE_PHI);
837 /* If this is not filtered earlier, then now it is too late. */
838 gcc_assert (gimple_phi_num_args (phi) == 2);
840 /* Find basic block and initialize iterator. */
841 bb = gimple_bb (phi);
843 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
844 if (EDGE_PRED (bb, 1)->src == true_bb)
846 arg_0 = gimple_phi_arg_def (phi, 1);
847 arg_1 = gimple_phi_arg_def (phi, 0);
851 arg_0 = gimple_phi_arg_def (phi, 0);
852 arg_1 = gimple_phi_arg_def (phi, 1);
855 /* Build new RHS using selected condition and arguments. */
856 rhs = build3 (COND_EXPR, TREE_TYPE (PHI_RESULT (phi)),
857 unshare_expr (cond), unshare_expr (arg_0),
858 unshare_expr (arg_1));
860 /* Create new GIMPLE_ASSIGN statement using RHS. */
861 new_stmt = gimple_build_assign (unshare_expr (PHI_RESULT (phi)), rhs);
863 /* Make new statement definition of the original phi result. */
864 SSA_NAME_DEF_STMT (gimple_phi_result (phi)) = new_stmt;
866 /* Insert using iterator. */
867 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
868 update_stmt (new_stmt);
870 if (dump_file && (dump_flags & TDF_DETAILS))
872 fprintf (dump_file, "new phi replacement stmt\n");
873 print_gimple_stmt (dump_file, new_stmt, 0, TDF_SLIM);
877 /* Process phi nodes for the given LOOP. Replace phi nodes with
878 conditional modify expressions. */
881 process_phi_nodes (struct loop *loop)
884 unsigned int orig_loop_num_nodes = loop->num_nodes;
887 for (i = 1; i < orig_loop_num_nodes; i++)
890 tree cond = NULL_TREE;
891 gimple_stmt_iterator gsi, phi_gsi;
892 basic_block true_bb = NULL;
895 if (bb == loop->header)
898 phi_gsi = gsi_start_phis (bb);
899 gsi = gsi_after_labels (bb);
901 /* BB has two predecessors. Using predecessor's aux field, set
902 appropriate condition for the PHI node replacement. */
903 if (!gsi_end_p (phi_gsi))
904 true_bb = find_phi_replacement_condition (loop, bb, &cond, &gsi);
906 while (!gsi_end_p (phi_gsi))
908 phi = gsi_stmt (phi_gsi);
909 replace_phi_with_cond_gimple_assign_stmt (phi, cond, true_bb, &gsi);
910 release_phi_node (phi);
913 set_phi_nodes (bb, NULL);
918 /* Combine all the basic blocks from LOOP into one or two super basic
919 blocks. Replace PHI nodes with conditional modify expressions. */
922 combine_blocks (struct loop *loop)
924 basic_block bb, exit_bb, merge_target_bb;
925 unsigned int orig_loop_num_nodes = loop->num_nodes;
930 /* Process phi nodes to prepare blocks for merge. */
931 process_phi_nodes (loop);
933 /* Merge basic blocks. First remove all the edges in the loop, except
934 for those from the exit block. */
936 for (i = 0; i < orig_loop_num_nodes; i++)
939 if (bb_with_exit_edge_p (loop, bb))
945 gcc_assert (exit_bb != loop->latch);
947 for (i = 1; i < orig_loop_num_nodes; i++)
951 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei));)
953 if (e->src == exit_bb)
962 if (exit_bb != loop->header)
964 /* Connect this node with loop header. */
965 make_edge (loop->header, exit_bb, EDGE_FALLTHRU);
966 set_immediate_dominator (CDI_DOMINATORS, exit_bb, loop->header);
969 /* Redirect non-exit edges to loop->latch. */
970 FOR_EACH_EDGE (e, ei, exit_bb->succs)
972 if (!loop_exit_edge_p (loop, e))
973 redirect_edge_and_branch (e, loop->latch);
975 set_immediate_dominator (CDI_DOMINATORS, loop->latch, exit_bb);
979 /* If the loop does not have exit then reconnect header and latch. */
980 make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
981 set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
984 merge_target_bb = loop->header;
985 for (i = 1; i < orig_loop_num_nodes; i++)
987 gimple_stmt_iterator gsi;
988 gimple_stmt_iterator last;
992 if (bb == exit_bb || bb == loop->latch)
995 /* Remove labels and make stmts member of loop->header. */
996 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
998 if (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL)
999 gsi_remove (&gsi, true);
1002 gimple_set_bb (gsi_stmt (gsi), merge_target_bb);
1007 /* Update stmt list. */
1008 last = gsi_last_bb (merge_target_bb);
1009 gsi_insert_seq_after (&last, bb_seq (bb), GSI_NEW_STMT);
1010 set_bb_seq (bb, NULL);
1012 delete_basic_block (bb);
1015 /* Now if possible, merge loop header and block with exit edge.
1016 This reduces number of basic blocks to 2. Auto vectorizer addresses
1017 loops with two nodes only. FIXME: Use cleanup_tree_cfg(). */
1019 && exit_bb != loop->header
1020 && can_merge_blocks_p (loop->header, exit_bb))
1021 merge_blocks (loop->header, exit_bb);
1024 /* Main entry point. Apply if-conversion to the LOOP. Return true if
1025 successful otherwise return false. If false is returned then loop
1026 remains unchanged. FOR_VECTORIZER is a boolean flag. It indicates
1027 whether if-conversion is used for vectorizer or not. If it is used
1028 for vectorizer, additional checks are used. (Vectorization checks
1029 are not yet implemented). */
1032 tree_if_conversion (struct loop *loop, bool for_vectorizer)
1035 gimple_stmt_iterator itr;
1040 /* If-conversion is not appropriate for all loops. First, check if
1041 loop is if-convertible or not. */
1042 if (!if_convertible_loop_p (loop, for_vectorizer))
1044 if (dump_file && (dump_flags & TDF_DETAILS))
1045 fprintf (dump_file,"-------------------------\n");
1051 free_dominance_info (CDI_POST_DOMINATORS);
1055 /* Do actual work now. */
1056 for (i = 0; i < loop->num_nodes; i++)
1062 /* Update condition using predicate list. */
1063 cond = (tree) bb->aux;
1065 /* Process all statements in this basic block.
1066 Remove conditional expression, if any, and annotate
1067 destination basic block(s) appropriately. */
1068 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); /* empty */)
1070 gimple t = gsi_stmt (itr);
1071 cond = tree_if_convert_stmt (loop, t, cond, &itr);
1072 if (!gsi_end_p (itr))
1076 /* If current bb has only one successor, then consider it as an
1077 unconditional goto. */
1078 if (single_succ_p (bb))
1080 basic_block bb_n = single_succ (bb);
1082 /* Successor bb inherits predicate of its predecessor. If there
1083 is no predicate in predecessor bb, then consider successor bb
1084 as always executed. */
1085 if (cond == NULL_TREE)
1086 cond = boolean_true_node;
1088 add_to_predicate_list (bb_n, cond);
1092 /* Now, all statements are if-converted and basic blocks are
1093 annotated appropriately. Combine all basic block into one huge
1095 combine_blocks (loop);
1098 clean_predicate_lists (loop);
1105 /* Tree if-conversion pass management. */
1108 main_tree_if_conversion (void)
1113 if (number_of_loops () <= 1)
1116 FOR_EACH_LOOP (li, loop, 0)
1118 tree_if_conversion (loop, true);
1124 gate_tree_if_conversion (void)
1126 return flag_tree_vectorize != 0;
1129 struct gimple_opt_pass pass_if_conversion =
1134 gate_tree_if_conversion, /* gate */
1135 main_tree_if_conversion, /* execute */
1138 0, /* static_pass_number */
1139 TV_NONE, /* tv_id */
1140 PROP_cfg | PROP_ssa, /* properties_required */
1141 0, /* properties_provided */
1142 0, /* properties_destroyed */
1143 0, /* todo_flags_start */
1144 TODO_dump_func | TODO_verify_stmts | TODO_verify_flow
1145 /* todo_flags_finish */