1 /* If-conversion for vectorizer.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010
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 a tree level if-conversion of loops. Its
23 initial goal is to help the vectorizer to vectorize loops with
26 A short description of if-conversion:
28 o Decide if a loop is if-convertible or not.
29 o Walk all loop basic blocks in breadth first order (BFS order).
30 o Remove conditional statements (at the end of basic block)
31 and propagate condition into destination basic blocks'
33 o Replace modify expression with conditional modify expression
34 using current basic block's condition.
35 o Merge all basic blocks
36 o Replace phi nodes with conditional modify expr
37 o Merge all basic blocks into header
39 Sample transformation:
44 # i_23 = PHI <0(0), i_18(10)>;
47 if (j_15 > 41) goto <L1>; else goto <L17>;
54 # iftmp.2_4 = PHI <0(8), 42(2)>;
58 if (i_18 <= 15) goto <L19>; else goto <L18>;
68 # i_23 = PHI <0(0), i_18(10)>;
73 iftmp.2_4 = j_15 > 41 ? 42 : 0;
76 if (i_18 <= 15) goto <L19>; else goto <L18>;
86 #include "coretypes.h"
91 #include "basic-block.h"
92 #include "diagnostic.h"
93 #include "tree-pretty-print.h"
94 #include "gimple-pretty-print.h"
95 #include "tree-flow.h"
96 #include "tree-dump.h"
98 #include "tree-chrec.h"
99 #include "tree-data-ref.h"
100 #include "tree-scalar-evolution.h"
101 #include "tree-pass.h"
103 /* List of basic blocks in if-conversion-suitable order. */
104 static basic_block *ifc_bbs;
106 /* Create 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 to the 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 /* Add the 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 COND to the e->aux field. In case the edge
179 destination is a PHI node, this condition will be added to
180 the block predicate to construct a 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 successor edges of BB exits LOOP. */
197 bb_with_exit_edge_p (struct loop *loop, basic_block bb)
202 FOR_EACH_EDGE (e, ei, bb->succs)
203 if (loop_exit_edge_p (loop, e))
209 /* STMT is a GIMPLE_COND. Update two destination's predicate list.
210 Remove COND_EXPR, if it is not the exit condition of LOOP.
211 Otherwise update the exit condition of LOOP appropriately. GSI
212 points to the statement STMT. */
215 tree_if_convert_cond_stmt (struct loop *loop, gimple stmt, tree cond,
216 gimple_stmt_iterator *gsi)
219 edge true_edge, false_edge;
220 location_t loc = gimple_location (stmt);
221 tree c = fold_build2_loc (loc, gimple_cond_code (stmt), boolean_type_node,
222 gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
224 extract_true_false_edges_from_block (gimple_bb (stmt),
225 &true_edge, &false_edge);
227 /* Add new condition into destination's predicate list. */
229 /* If C is true, then TRUE_EDGE is taken. */
230 add_to_dst_predicate_list (loop, true_edge, cond, c, gsi);
232 /* If C is false, then FALSE_EDGE is taken. */
233 c2 = invert_truthvalue_loc (loc, unshare_expr (c));
234 add_to_dst_predicate_list (loop, false_edge, cond, c2, gsi);
236 /* Now this conditional statement is redundant. Remove it. But, do
237 not remove the exit condition! Update the exit condition using
238 the new condition. */
239 if (!bb_with_exit_edge_p (loop, gimple_bb (stmt)))
241 gsi_remove (gsi, true);
246 /* If-convert stmt T which is part of LOOP.
248 If T is a GIMPLE_ASSIGN then it is converted into a conditional
249 modify expression using COND. For conditional expressions, add
250 a condition in the destination basic block's predicate list and
251 remove the conditional expression itself. GSI points to the
255 tree_if_convert_stmt (struct loop *loop, gimple t, tree cond,
256 gimple_stmt_iterator *gsi)
258 if (dump_file && (dump_flags & TDF_DETAILS))
260 fprintf (dump_file, "------if-convert stmt\n");
261 print_gimple_stmt (dump_file, t, 0, TDF_SLIM);
262 print_generic_stmt (dump_file, cond, TDF_SLIM);
265 switch (gimple_code (t))
267 /* Labels are harmless here. */
272 /* ??? Should there be conditional GIMPLE_DEBUG_BINDs? */
273 if (gimple_debug_bind_p (gsi_stmt (*gsi)))
275 gimple_debug_bind_reset_value (gsi_stmt (*gsi));
276 update_stmt (gsi_stmt (*gsi));
281 /* This GIMPLE_ASSIGN is killing previous value of LHS. Appropriate
282 value will be selected by PHI node based on condition. It is possible
283 that before this transformation, PHI nodes was selecting default
284 value and now it will use this new value. This is OK because it does
285 not change the validity of the program. */
289 /* Update destination blocks' predicate list and remove this
290 condition expression. */
291 tree_if_convert_cond_stmt (loop, t, cond, gsi);
302 /* Return true when PHI is if-convertible. PHI is part of loop LOOP
303 and it belongs to basic block BB.
305 PHI is not if-convertible if:
306 - it has more than 2 arguments,
307 - virtual PHI is immediately used in another PHI node,
308 - virtual PHI on BB other than header. */
311 if_convertible_phi_p (struct loop *loop, basic_block bb, gimple phi)
313 if (dump_file && (dump_flags & TDF_DETAILS))
315 fprintf (dump_file, "-------------------------\n");
316 print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
319 if (bb != loop->header && gimple_phi_num_args (phi) != 2)
321 if (dump_file && (dump_flags & TDF_DETAILS))
322 fprintf (dump_file, "More than two phi node args.\n");
326 if (!is_gimple_reg (SSA_NAME_VAR (gimple_phi_result (phi))))
328 imm_use_iterator imm_iter;
331 if (bb != loop->header)
333 if (dump_file && (dump_flags & TDF_DETAILS))
334 fprintf (dump_file, "Virtual phi not on loop header.\n");
337 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_phi_result (phi))
339 if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI)
341 if (dump_file && (dump_flags & TDF_DETAILS))
342 fprintf (dump_file, "Difficult to handle this virtual phi.\n");
351 /* Return true when STMT is if-convertible.
353 GIMPLE_ASSIGN statement is not if-convertible if,
356 - 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,
364 tree lhs = gimple_assign_lhs (stmt);
366 if (dump_file && (dump_flags & TDF_DETAILS))
368 fprintf (dump_file, "-------------------------\n");
369 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
372 /* Some of these constrains might be too conservative. */
373 if (stmt_ends_bb_p (stmt)
374 || gimple_has_volatile_ops (stmt)
375 || (TREE_CODE (lhs) == SSA_NAME
376 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
377 || gimple_has_side_effects (stmt))
379 if (dump_file && (dump_flags & TDF_DETAILS))
380 fprintf (dump_file, "stmt not suitable for ifcvt\n");
384 /* See if it needs speculative loading or not. */
385 if (bb != loop->header
386 && gimple_assign_rhs_could_trap_p (stmt))
388 if (dump_file && (dump_flags & TDF_DETAILS))
389 fprintf (dump_file, "tree could trap...\n");
393 if (TREE_CODE (lhs) != SSA_NAME
394 && bb != loop->header
395 && !bb_with_exit_edge_p (loop, bb))
397 if (dump_file && (dump_flags & TDF_DETAILS))
399 fprintf (dump_file, "LHS is not var\n");
400 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
408 /* Return true when STMT is if-convertible.
410 A statement is if-convertible if:
411 - it is an if-convertible GIMPLE_ASSGIN,
412 - it is a GIMPLE_LABEL or a GIMPLE_COND.
414 STMT is inside BB, which is inside loop LOOP. */
417 if_convertible_stmt_p (struct loop *loop, basic_block bb, gimple stmt)
419 switch (gimple_code (stmt))
427 return if_convertible_gimple_assign_stmt_p (loop, bb, stmt);
430 /* Don't know what to do with 'em so don't do anything. */
431 if (dump_file && (dump_flags & TDF_DETAILS))
433 fprintf (dump_file, "don't know what to do\n");
434 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
443 /* Return true when BB is if-convertible. This routine does not check
444 basic block's statements and phis.
446 A basic block is not if-convertible if:
447 - it is non-empty and it is after the exit block (in BFS order),
448 - it is after the exit block but before the latch,
449 - its edges are not normal.
451 EXIT_BB is the basic block containing the exit of the LOOP. BB is
455 if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
460 if (dump_file && (dump_flags & TDF_DETAILS))
461 fprintf (dump_file, "----------[%d]-------------\n", bb->index);
465 if (bb != loop->latch)
467 if (dump_file && (dump_flags & TDF_DETAILS))
468 fprintf (dump_file, "basic block after exit bb but before latch\n");
471 else if (!empty_block_p (bb))
473 if (dump_file && (dump_flags & TDF_DETAILS))
474 fprintf (dump_file, "non empty basic block after exit bb\n");
477 else if (bb == loop->latch
479 && !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
481 if (dump_file && (dump_flags & TDF_DETAILS))
482 fprintf (dump_file, "latch is not dominated by exit_block\n");
487 /* Be less adventurous and handle only normal edges. */
488 FOR_EACH_EDGE (e, ei, bb->succs)
490 (EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
492 if (dump_file && (dump_flags & TDF_DETAILS))
493 fprintf (dump_file, "Difficult to handle edges\n");
500 /* Return true when all predecessor blocks of BB are visited. The
501 VISITED bitmap keeps track of the visited blocks. */
504 pred_blocks_visited_p (basic_block bb, bitmap *visited)
508 FOR_EACH_EDGE (e, ei, bb->preds)
509 if (!bitmap_bit_p (*visited, e->src->index))
515 /* Get body of a LOOP in suitable order for if-conversion. It is
516 caller's responsibility to deallocate basic block list.
517 If-conversion suitable order is, breadth first sort (BFS) order
518 with an additional constraint: select a block only if all its
519 predecessors are already selected. */
522 get_loop_body_in_if_conv_order (const struct loop *loop)
524 basic_block *blocks, *blocks_in_bfs_order;
527 unsigned int index = 0;
528 unsigned int visited_count = 0;
530 gcc_assert (loop->num_nodes);
531 gcc_assert (loop->latch != EXIT_BLOCK_PTR);
533 blocks = XCNEWVEC (basic_block, loop->num_nodes);
534 visited = BITMAP_ALLOC (NULL);
536 blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
539 while (index < loop->num_nodes)
541 bb = blocks_in_bfs_order [index];
543 if (bb->flags & BB_IRREDUCIBLE_LOOP)
545 free (blocks_in_bfs_order);
546 BITMAP_FREE (visited);
551 if (!bitmap_bit_p (visited, bb->index))
553 if (pred_blocks_visited_p (bb, &visited)
554 || bb == loop->header)
556 /* This block is now visited. */
557 bitmap_set_bit (visited, bb->index);
558 blocks[visited_count++] = bb;
564 if (index == loop->num_nodes
565 && visited_count != loop->num_nodes)
569 free (blocks_in_bfs_order);
570 BITMAP_FREE (visited);
574 /* Return true when LOOP is if-convertible.
575 LOOP is if-convertible if:
577 - it has two or more basic blocks,
578 - it has only one exit,
579 - loop header is not the exit edge,
580 - if its basic blocks and phi nodes are if convertible. */
583 if_convertible_loop_p (struct loop *loop)
586 gimple_stmt_iterator itr;
590 basic_block exit_bb = NULL;
592 /* Handle only innermost loop. */
593 if (!loop || loop->inner)
595 if (dump_file && (dump_flags & TDF_DETAILS))
596 fprintf (dump_file, "not innermost loop\n");
600 /* If only one block, no need for if-conversion. */
601 if (loop->num_nodes <= 2)
603 if (dump_file && (dump_flags & TDF_DETAILS))
604 fprintf (dump_file, "less than 2 basic blocks\n");
608 /* More than one loop exit is too much to handle. */
609 if (!single_exit (loop))
611 if (dump_file && (dump_flags & TDF_DETAILS))
612 fprintf (dump_file, "multiple exits\n");
616 /* ??? Check target's vector conditional operation support for vectorizer. */
618 /* If one of the loop header's edge is exit edge then do not apply
620 FOR_EACH_EDGE (e, ei, loop->header->succs)
622 if (loop_exit_edge_p (loop, e))
626 calculate_dominance_info (CDI_DOMINATORS);
628 /* Allow statements that can be handled during if-conversion. */
629 ifc_bbs = get_loop_body_in_if_conv_order (loop);
632 if (dump_file && (dump_flags & TDF_DETAILS))
633 fprintf (dump_file, "Irreducible loop\n");
637 for (i = 0; i < loop->num_nodes; i++)
641 if (!if_convertible_bb_p (loop, bb, exit_bb))
644 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
645 if (!if_convertible_stmt_p (loop, bb, gsi_stmt (itr)))
648 itr = gsi_start_phis (bb);
650 if (!gsi_end_p (itr))
651 FOR_EACH_EDGE (e, ei, bb->preds)
654 for (; !gsi_end_p (itr); gsi_next (&itr))
655 if (!if_convertible_phi_p (loop, bb, gsi_stmt (itr)))
658 if (bb_with_exit_edge_p (loop, bb))
663 fprintf (dump_file, "Applying if-conversion\n");
668 /* During if-conversion, the bb->aux field is used to hold a predicate
669 list. This function cleans for all the basic blocks in the given
670 LOOP their predicate list. It also cleans up the e->aux field of
671 all the successor edges: e->aux is used to hold the true and false
672 conditions for conditional expressions. */
675 clean_predicate_lists (struct loop *loop)
682 bb = get_loop_body (loop);
683 for (i = 0; i < loop->num_nodes; i++)
686 FOR_EACH_EDGE (e, ei, bb[i]->succs)
692 /* Basic block BB has two predecessors. Using predecessor's bb->aux
693 field, set appropriate condition COND for the PHI node replacement.
694 Return true block whose phi arguments are selected when cond is
695 true. LOOP is the loop containing the if-converted region, GSI is
696 the place to insert the code for the if-conversion. */
699 find_phi_replacement_condition (struct loop *loop,
700 basic_block bb, tree *cond,
701 gimple_stmt_iterator *gsi)
703 edge first_edge, second_edge;
706 gcc_assert (EDGE_COUNT (bb->preds) == 2);
707 first_edge = EDGE_PRED (bb, 0);
708 second_edge = EDGE_PRED (bb, 1);
710 /* Use condition based on following criteria:
716 S2 is preferred over S1. Make 'b' first_bb and use its condition.
718 2) Do not make loop header first_bb.
721 S1: x = !(c == d)? a : b;
726 S3: x = (c == d) ? b : a;
728 S3 is preferred over S1 and S2*, Make 'b' first_bb and use
731 4) If pred B is dominated by pred A then use pred B's condition.
734 /* Select condition that is not TRUTH_NOT_EXPR. */
735 tmp_cond = (tree) (first_edge->src)->aux;
736 gcc_assert (tmp_cond);
738 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
742 tmp_edge = first_edge;
743 first_edge = second_edge;
744 second_edge = tmp_edge;
747 /* Check if FIRST_BB is loop header or not and make sure that
748 FIRST_BB does not dominate SECOND_BB. */
749 if (first_edge->src == loop->header
750 || dominated_by_p (CDI_DOMINATORS,
751 second_edge->src, first_edge->src))
753 *cond = (tree) (second_edge->src)->aux;
755 /* If there is a condition on an incoming edge, add it to the
756 incoming bb predicate. */
757 if (second_edge->aux)
758 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
759 *cond, (tree) second_edge->aux);
761 if (TREE_CODE (*cond) == TRUTH_NOT_EXPR)
762 *cond = invert_truthvalue (*cond);
764 /* Select non loop header bb. */
765 first_edge = second_edge;
769 *cond = (tree) (first_edge->src)->aux;
771 /* If there is a condition on an incoming edge, add it to the
772 incoming bb predicate. */
774 *cond = build2 (TRUTH_AND_EXPR, boolean_type_node,
775 *cond, (tree) first_edge->aux);
778 /* Gimplify the condition: the vectorizer prefers to have gimple
779 values as conditions. Various targets use different means to
780 communicate conditions in vector compare operations. Using a
781 gimple value allows the compiler to emit vector compare and
782 select RTL without exposing compare's result. */
783 *cond = force_gimple_operand_gsi (gsi, unshare_expr (*cond),
785 true, GSI_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 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
792 *cond = gimple_assign_lhs (new_stmt);
797 return first_edge->src;
800 /* Replace PHI node with conditional modify expr using COND. This
801 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;
808 The generated code is inserted at GSI that points to the top of
809 basic block's statement list. When COND is true, phi arg from
810 TRUE_BB is selected. */
813 replace_phi_with_cond_gimple_assign_stmt (gimple phi, tree cond,
815 gimple_stmt_iterator *gsi)
822 gcc_assert (gimple_code (phi) == GIMPLE_PHI
823 && gimple_phi_num_args (phi) == 2);
825 bb = gimple_bb (phi);
827 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
828 if (EDGE_PRED (bb, 1)->src == true_bb)
830 arg_0 = gimple_phi_arg_def (phi, 1);
831 arg_1 = gimple_phi_arg_def (phi, 0);
835 arg_0 = gimple_phi_arg_def (phi, 0);
836 arg_1 = gimple_phi_arg_def (phi, 1);
839 /* Build new RHS using selected condition and arguments. */
840 rhs = build3 (COND_EXPR, TREE_TYPE (PHI_RESULT (phi)),
841 unshare_expr (cond), unshare_expr (arg_0),
842 unshare_expr (arg_1));
844 new_stmt = gimple_build_assign (unshare_expr (PHI_RESULT (phi)), rhs);
845 SSA_NAME_DEF_STMT (gimple_phi_result (phi)) = new_stmt;
846 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
847 update_stmt (new_stmt);
849 if (dump_file && (dump_flags & TDF_DETAILS))
851 fprintf (dump_file, "new phi replacement stmt\n");
852 print_gimple_stmt (dump_file, new_stmt, 0, TDF_SLIM);
856 /* Process phi nodes for the given LOOP. Replace phi nodes with
857 conditional modify expressions. */
860 process_phi_nodes (struct loop *loop)
863 unsigned int orig_loop_num_nodes = loop->num_nodes;
866 for (i = 1; i < orig_loop_num_nodes; i++)
869 tree cond = NULL_TREE;
870 gimple_stmt_iterator gsi, phi_gsi;
871 basic_block true_bb = NULL;
874 if (bb == loop->header)
877 phi_gsi = gsi_start_phis (bb);
878 gsi = gsi_after_labels (bb);
880 /* BB has two predecessors. Using predecessor's aux field, set
881 appropriate condition for the PHI node replacement. */
882 if (!gsi_end_p (phi_gsi))
883 true_bb = find_phi_replacement_condition (loop, bb, &cond, &gsi);
885 while (!gsi_end_p (phi_gsi))
887 phi = gsi_stmt (phi_gsi);
888 replace_phi_with_cond_gimple_assign_stmt (phi, cond, true_bb, &gsi);
889 release_phi_node (phi);
892 set_phi_nodes (bb, NULL);
896 /* Combine all the basic blocks from LOOP into one or two super basic
897 blocks. Replace PHI nodes with conditional modify expressions. */
900 combine_blocks (struct loop *loop)
902 basic_block bb, exit_bb, merge_target_bb;
903 unsigned int orig_loop_num_nodes = loop->num_nodes;
908 /* Process phi nodes to prepare blocks for merge. */
909 process_phi_nodes (loop);
911 /* Merge basic blocks: first remove all the edges in the loop,
912 except for those from the exit block. */
914 for (i = 0; i < orig_loop_num_nodes; i++)
917 if (bb_with_exit_edge_p (loop, bb))
923 gcc_assert (exit_bb != loop->latch);
925 for (i = 1; i < orig_loop_num_nodes; i++)
929 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei));)
931 if (e->src == exit_bb)
940 if (exit_bb != loop->header)
942 /* Connect this node to loop header. */
943 make_edge (loop->header, exit_bb, EDGE_FALLTHRU);
944 set_immediate_dominator (CDI_DOMINATORS, exit_bb, loop->header);
947 /* Redirect non-exit edges to loop->latch. */
948 FOR_EACH_EDGE (e, ei, exit_bb->succs)
950 if (!loop_exit_edge_p (loop, e))
951 redirect_edge_and_branch (e, loop->latch);
953 set_immediate_dominator (CDI_DOMINATORS, loop->latch, exit_bb);
957 /* If the loop does not have an exit, reconnect header and latch. */
958 make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
959 set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
962 merge_target_bb = loop->header;
963 for (i = 1; i < orig_loop_num_nodes; i++)
965 gimple_stmt_iterator gsi;
966 gimple_stmt_iterator last;
970 if (bb == exit_bb || bb == loop->latch)
973 /* Remove labels and make stmts member of loop->header. */
974 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
976 if (gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL)
977 gsi_remove (&gsi, true);
980 gimple_set_bb (gsi_stmt (gsi), merge_target_bb);
985 /* Update stmt list. */
986 last = gsi_last_bb (merge_target_bb);
987 gsi_insert_seq_after (&last, bb_seq (bb), GSI_NEW_STMT);
988 set_bb_seq (bb, NULL);
990 delete_basic_block (bb);
993 /* If possible, merge loop header to the block with the exit edge.
994 This reduces the number of basic blocks to two, to please the
995 vectorizer that handles only loops with two nodes.
997 FIXME: Call cleanup_tree_cfg. */
999 && exit_bb != loop->header
1000 && can_merge_blocks_p (loop->header, exit_bb))
1001 merge_blocks (loop->header, exit_bb);
1004 /* If-convert LOOP when it is legal. For the moment this pass has no
1005 profitability analysis. */
1008 tree_if_conversion (struct loop *loop)
1010 gimple_stmt_iterator itr;
1015 /* If-conversion is not appropriate for all loops. First, check if
1016 the loop is if-convertible. */
1017 if (!if_convertible_loop_p (loop))
1019 if (dump_file && (dump_flags & TDF_DETAILS))
1020 fprintf (dump_file, "-------------------------\n");
1029 for (i = 0; i < loop->num_nodes; i++)
1031 basic_block bb = ifc_bbs [i];
1032 tree cond = (tree) bb->aux;
1034 /* Process all the statements in this basic block.
1035 Remove conditional expression, if any, and annotate
1036 destination basic block(s) appropriately. */
1037 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); /* empty */)
1039 gimple t = gsi_stmt (itr);
1040 cond = tree_if_convert_stmt (loop, t, cond, &itr);
1041 if (!gsi_end_p (itr))
1045 /* If current bb has only one successor, then consider it as an
1046 unconditional goto. */
1047 if (single_succ_p (bb))
1049 basic_block bb_n = single_succ (bb);
1051 /* The successor bb inherits the predicate of its
1052 predecessor. If there is no predicate in the predecessor
1053 bb, then consider the successor bb as always executed. */
1054 if (cond == NULL_TREE)
1055 cond = boolean_true_node;
1057 add_to_predicate_list (bb_n, cond);
1061 /* Now, all statements are if-converted and basic blocks are
1062 annotated appropriately. Combine all the basic blocks into one
1063 huge basic block. */
1064 combine_blocks (loop);
1067 clean_predicate_lists (loop);
1072 /* Tree if-conversion pass management. */
1075 main_tree_if_conversion (void)
1080 if (number_of_loops () <= 1)
1083 FOR_EACH_LOOP (li, loop, 0)
1084 tree_if_conversion (loop);
1090 gate_tree_if_conversion (void)
1092 return flag_tree_vectorize != 0;
1095 struct gimple_opt_pass pass_if_conversion =
1100 gate_tree_if_conversion, /* gate */
1101 main_tree_if_conversion, /* execute */
1104 0, /* static_pass_number */
1105 TV_NONE, /* tv_id */
1106 PROP_cfg | PROP_ssa, /* properties_required */
1107 0, /* properties_provided */
1108 0, /* properties_destroyed */
1109 0, /* todo_flags_start */
1110 TODO_dump_func | TODO_verify_stmts | TODO_verify_flow
1111 /* todo_flags_finish */