Merge branch 'vendor/GCC47'
[dragonfly.git] / contrib / gcc-4.7 / gcc / tree-if-conv.c
CommitLineData
e4b17023
JM
1/* If-conversion for vectorizer.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
3 Free Software Foundation, Inc.
4 Contributed by Devang Patel <dpatel@apple.com>
5
6This file is part of GCC.
7
8GCC is free software; you can redistribute it and/or modify it under
9the terms of the GNU General Public License as published by the Free
10Software Foundation; either version 3, or (at your option) any later
11version.
12
13GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14WARRANTY; without even the implied warranty of MERCHANTABILITY or
15FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16for more details.
17
18You should have received a copy of the GNU General Public License
19along with GCC; see the file COPYING3. If not see
20<http://www.gnu.org/licenses/>. */
21
22/* This pass implements a tree level if-conversion of loops. Its
23 initial goal is to help the vectorizer to vectorize loops with
24 conditions.
25
26 A short description of if-conversion:
27
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'
32 predicate list.
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
38
39 Sample transformation:
40
41 INPUT
42 -----
43
44 # i_23 = PHI <0(0), i_18(10)>;
45 <L0>:;
46 j_15 = A[i_23];
47 if (j_15 > 41) goto <L1>; else goto <L17>;
48
49 <L17>:;
50 goto <bb 3> (<L3>);
51
52 <L1>:;
53
54 # iftmp.2_4 = PHI <0(8), 42(2)>;
55 <L3>:;
56 A[i_23] = iftmp.2_4;
57 i_18 = i_23 + 1;
58 if (i_18 <= 15) goto <L19>; else goto <L18>;
59
60 <L19>:;
61 goto <bb 1> (<L0>);
62
63 <L18>:;
64
65 OUTPUT
66 ------
67
68 # i_23 = PHI <0(0), i_18(10)>;
69 <L0>:;
70 j_15 = A[i_23];
71
72 <L3>:;
73 iftmp.2_4 = j_15 > 41 ? 42 : 0;
74 A[i_23] = iftmp.2_4;
75 i_18 = i_23 + 1;
76 if (i_18 <= 15) goto <L19>; else goto <L18>;
77
78 <L19>:;
79 goto <bb 1> (<L0>);
80
81 <L18>:;
82*/
83
84#include "config.h"
85#include "system.h"
86#include "coretypes.h"
87#include "tm.h"
88#include "tree.h"
89#include "flags.h"
90#include "timevar.h"
91#include "basic-block.h"
92#include "tree-pretty-print.h"
93#include "gimple-pretty-print.h"
94#include "tree-flow.h"
95#include "tree-dump.h"
96#include "cfgloop.h"
97#include "tree-chrec.h"
98#include "tree-data-ref.h"
99#include "tree-scalar-evolution.h"
100#include "tree-pass.h"
101#include "dbgcnt.h"
102
103/* List of basic blocks in if-conversion-suitable order. */
104static basic_block *ifc_bbs;
105
106/* Structure used to predicate basic blocks. This is attached to the
107 ->aux field of the BBs in the loop to be if-converted. */
108typedef struct bb_predicate_s {
109
110 /* The condition under which this basic block is executed. */
111 tree predicate;
112
113 /* PREDICATE is gimplified, and the sequence of statements is
114 recorded here, in order to avoid the duplication of computations
115 that occur in previous conditions. See PR44483. */
116 gimple_seq predicate_gimplified_stmts;
117} *bb_predicate_p;
118
119/* Returns true when the basic block BB has a predicate. */
120
121static inline bool
122bb_has_predicate (basic_block bb)
123{
124 return bb->aux != NULL;
125}
126
127/* Returns the gimplified predicate for basic block BB. */
128
129static inline tree
130bb_predicate (basic_block bb)
131{
132 return ((bb_predicate_p) bb->aux)->predicate;
133}
134
135/* Sets the gimplified predicate COND for basic block BB. */
136
137static inline void
138set_bb_predicate (basic_block bb, tree cond)
139{
140 gcc_assert ((TREE_CODE (cond) == TRUTH_NOT_EXPR
141 && is_gimple_condexpr (TREE_OPERAND (cond, 0)))
142 || is_gimple_condexpr (cond));
143 ((bb_predicate_p) bb->aux)->predicate = cond;
144}
145
146/* Returns the sequence of statements of the gimplification of the
147 predicate for basic block BB. */
148
149static inline gimple_seq
150bb_predicate_gimplified_stmts (basic_block bb)
151{
152 return ((bb_predicate_p) bb->aux)->predicate_gimplified_stmts;
153}
154
155/* Sets the sequence of statements STMTS of the gimplification of the
156 predicate for basic block BB. */
157
158static inline void
159set_bb_predicate_gimplified_stmts (basic_block bb, gimple_seq stmts)
160{
161 ((bb_predicate_p) bb->aux)->predicate_gimplified_stmts = stmts;
162}
163
164/* Adds the sequence of statements STMTS to the sequence of statements
165 of the predicate for basic block BB. */
166
167static inline void
168add_bb_predicate_gimplified_stmts (basic_block bb, gimple_seq stmts)
169{
170 gimple_seq_add_seq
171 (&(((bb_predicate_p) bb->aux)->predicate_gimplified_stmts), stmts);
172}
173
174/* Initializes to TRUE the predicate of basic block BB. */
175
176static inline void
177init_bb_predicate (basic_block bb)
178{
179 bb->aux = XNEW (struct bb_predicate_s);
180 set_bb_predicate_gimplified_stmts (bb, NULL);
181 set_bb_predicate (bb, boolean_true_node);
182}
183
184/* Free the predicate of basic block BB. */
185
186static inline void
187free_bb_predicate (basic_block bb)
188{
189 gimple_seq stmts;
190
191 if (!bb_has_predicate (bb))
192 return;
193
194 /* Release the SSA_NAMEs created for the gimplification of the
195 predicate. */
196 stmts = bb_predicate_gimplified_stmts (bb);
197 if (stmts)
198 {
199 gimple_stmt_iterator i;
200
201 for (i = gsi_start (stmts); !gsi_end_p (i); gsi_next (&i))
202 free_stmt_operands (gsi_stmt (i));
203 }
204
205 free (bb->aux);
206 bb->aux = NULL;
207}
208
209/* Free the predicate of BB and reinitialize it with the true
210 predicate. */
211
212static inline void
213reset_bb_predicate (basic_block bb)
214{
215 free_bb_predicate (bb);
216 init_bb_predicate (bb);
217}
218
219/* Returns a new SSA_NAME of type TYPE that is assigned the value of
220 the expression EXPR. Inserts the statement created for this
221 computation before GSI and leaves the iterator GSI at the same
222 statement. */
223
224static tree
225ifc_temp_var (tree type, tree expr, gimple_stmt_iterator *gsi)
226{
227 const char *name = "_ifc_";
228 tree var, new_name;
229 gimple stmt;
230
231 /* Create new temporary variable. */
232 var = create_tmp_var (type, name);
233 add_referenced_var (var);
234
235 /* Build new statement to assign EXPR to new variable. */
236 stmt = gimple_build_assign (var, expr);
237
238 /* Get SSA name for the new variable and set make new statement
239 its definition statement. */
240 new_name = make_ssa_name (var, stmt);
241 gimple_assign_set_lhs (stmt, new_name);
242 SSA_NAME_DEF_STMT (new_name) = stmt;
243 update_stmt (stmt);
244
245 gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
246 return gimple_assign_lhs (stmt);
247}
248
249/* Return true when COND is a true predicate. */
250
251static inline bool
252is_true_predicate (tree cond)
253{
254 return (cond == NULL_TREE
255 || cond == boolean_true_node
256 || integer_onep (cond));
257}
258
259/* Returns true when BB has a predicate that is not trivial: true or
260 NULL_TREE. */
261
262static inline bool
263is_predicated (basic_block bb)
264{
265 return !is_true_predicate (bb_predicate (bb));
266}
267
268/* Parses the predicate COND and returns its comparison code and
269 operands OP0 and OP1. */
270
271static enum tree_code
272parse_predicate (tree cond, tree *op0, tree *op1)
273{
274 gimple s;
275
276 if (TREE_CODE (cond) == SSA_NAME
277 && is_gimple_assign (s = SSA_NAME_DEF_STMT (cond)))
278 {
279 if (TREE_CODE_CLASS (gimple_assign_rhs_code (s)) == tcc_comparison)
280 {
281 *op0 = gimple_assign_rhs1 (s);
282 *op1 = gimple_assign_rhs2 (s);
283 return gimple_assign_rhs_code (s);
284 }
285
286 else if (gimple_assign_rhs_code (s) == TRUTH_NOT_EXPR)
287 {
288 tree op = gimple_assign_rhs1 (s);
289 tree type = TREE_TYPE (op);
290 enum tree_code code = parse_predicate (op, op0, op1);
291
292 return code == ERROR_MARK ? ERROR_MARK
293 : invert_tree_comparison (code, HONOR_NANS (TYPE_MODE (type)));
294 }
295
296 return ERROR_MARK;
297 }
298
299 if (TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison)
300 {
301 *op0 = TREE_OPERAND (cond, 0);
302 *op1 = TREE_OPERAND (cond, 1);
303 return TREE_CODE (cond);
304 }
305
306 return ERROR_MARK;
307}
308
309/* Returns the fold of predicate C1 OR C2 at location LOC. */
310
311static tree
312fold_or_predicates (location_t loc, tree c1, tree c2)
313{
314 tree op1a, op1b, op2a, op2b;
315 enum tree_code code1 = parse_predicate (c1, &op1a, &op1b);
316 enum tree_code code2 = parse_predicate (c2, &op2a, &op2b);
317
318 if (code1 != ERROR_MARK && code2 != ERROR_MARK)
319 {
320 tree t = maybe_fold_or_comparisons (code1, op1a, op1b,
321 code2, op2a, op2b);
322 if (t)
323 return t;
324 }
325
326 return fold_build2_loc (loc, TRUTH_OR_EXPR, boolean_type_node, c1, c2);
327}
328
329/* Add condition NC to the predicate list of basic block BB. */
330
331static inline void
332add_to_predicate_list (basic_block bb, tree nc)
333{
334 tree bc, *tp;
335
336 if (is_true_predicate (nc))
337 return;
338
339 if (!is_predicated (bb))
340 bc = nc;
341 else
342 {
343 bc = bb_predicate (bb);
344 bc = fold_or_predicates (EXPR_LOCATION (bc), nc, bc);
345 if (is_true_predicate (bc))
346 {
347 reset_bb_predicate (bb);
348 return;
349 }
350 }
351
352 /* Allow a TRUTH_NOT_EXPR around the main predicate. */
353 if (TREE_CODE (bc) == TRUTH_NOT_EXPR)
354 tp = &TREE_OPERAND (bc, 0);
355 else
356 tp = &bc;
357 if (!is_gimple_condexpr (*tp))
358 {
359 gimple_seq stmts;
360 *tp = force_gimple_operand_1 (*tp, &stmts, is_gimple_condexpr, NULL_TREE);
361 add_bb_predicate_gimplified_stmts (bb, stmts);
362 }
363 set_bb_predicate (bb, bc);
364}
365
366/* Add the condition COND to the previous condition PREV_COND, and add
367 this to the predicate list of the destination of edge E. LOOP is
368 the loop to be if-converted. */
369
370static void
371add_to_dst_predicate_list (struct loop *loop, edge e,
372 tree prev_cond, tree cond)
373{
374 if (!flow_bb_inside_loop_p (loop, e->dest))
375 return;
376
377 if (!is_true_predicate (prev_cond))
378 cond = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
379 prev_cond, cond);
380
381 add_to_predicate_list (e->dest, cond);
382}
383
384/* Return true if one of the successor edges of BB exits LOOP. */
385
386static bool
387bb_with_exit_edge_p (struct loop *loop, basic_block bb)
388{
389 edge e;
390 edge_iterator ei;
391
392 FOR_EACH_EDGE (e, ei, bb->succs)
393 if (loop_exit_edge_p (loop, e))
394 return true;
395
396 return false;
397}
398
399/* Return true when PHI is if-convertible. PHI is part of loop LOOP
400 and it belongs to basic block BB.
401
402 PHI is not if-convertible if:
403 - it has more than 2 arguments.
404
405 When the flag_tree_loop_if_convert_stores is not set, PHI is not
406 if-convertible if:
407 - a virtual PHI is immediately used in another PHI node,
408 - there is a virtual PHI in a BB other than the loop->header. */
409
410static bool
411if_convertible_phi_p (struct loop *loop, basic_block bb, gimple phi)
412{
413 if (dump_file && (dump_flags & TDF_DETAILS))
414 {
415 fprintf (dump_file, "-------------------------\n");
416 print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
417 }
418
419 if (bb != loop->header && gimple_phi_num_args (phi) != 2)
420 {
421 if (dump_file && (dump_flags & TDF_DETAILS))
422 fprintf (dump_file, "More than two phi node args.\n");
423 return false;
424 }
425
426 if (flag_tree_loop_if_convert_stores)
427 return true;
428
429 /* When the flag_tree_loop_if_convert_stores is not set, check
430 that there are no memory writes in the branches of the loop to be
431 if-converted. */
432 if (!is_gimple_reg (SSA_NAME_VAR (gimple_phi_result (phi))))
433 {
434 imm_use_iterator imm_iter;
435 use_operand_p use_p;
436
437 if (bb != loop->header)
438 {
439 if (dump_file && (dump_flags & TDF_DETAILS))
440 fprintf (dump_file, "Virtual phi not on loop->header.\n");
441 return false;
442 }
443
444 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_phi_result (phi))
445 {
446 if (gimple_code (USE_STMT (use_p)) == GIMPLE_PHI)
447 {
448 if (dump_file && (dump_flags & TDF_DETAILS))
449 fprintf (dump_file, "Difficult to handle this virtual phi.\n");
450 return false;
451 }
452 }
453 }
454
455 return true;
456}
457
458/* Records the status of a data reference. This struct is attached to
459 each DR->aux field. */
460
461struct ifc_dr {
462 /* -1 when not initialized, 0 when false, 1 when true. */
463 int written_at_least_once;
464
465 /* -1 when not initialized, 0 when false, 1 when true. */
466 int rw_unconditionally;
467};
468
469#define IFC_DR(DR) ((struct ifc_dr *) (DR)->aux)
470#define DR_WRITTEN_AT_LEAST_ONCE(DR) (IFC_DR (DR)->written_at_least_once)
471#define DR_RW_UNCONDITIONALLY(DR) (IFC_DR (DR)->rw_unconditionally)
472
473/* Returns true when the memory references of STMT are read or written
474 unconditionally. In other words, this function returns true when
475 for every data reference A in STMT there exist other accesses to
476 a data reference with the same base with predicates that add up (OR-up) to
477 the true predicate: this ensures that the data reference A is touched
478 (read or written) on every iteration of the if-converted loop. */
479
480static bool
481memrefs_read_or_written_unconditionally (gimple stmt,
482 VEC (data_reference_p, heap) *drs)
483{
484 int i, j;
485 data_reference_p a, b;
486 tree ca = bb_predicate (gimple_bb (stmt));
487
488 for (i = 0; VEC_iterate (data_reference_p, drs, i, a); i++)
489 if (DR_STMT (a) == stmt)
490 {
491 bool found = false;
492 int x = DR_RW_UNCONDITIONALLY (a);
493
494 if (x == 0)
495 return false;
496
497 if (x == 1)
498 continue;
499
500 for (j = 0; VEC_iterate (data_reference_p, drs, j, b); j++)
501 {
502 tree ref_base_a = DR_REF (a);
503 tree ref_base_b = DR_REF (b);
504
505 if (DR_STMT (b) == stmt)
506 continue;
507
508 while (TREE_CODE (ref_base_a) == COMPONENT_REF
509 || TREE_CODE (ref_base_a) == IMAGPART_EXPR
510 || TREE_CODE (ref_base_a) == REALPART_EXPR)
511 ref_base_a = TREE_OPERAND (ref_base_a, 0);
512
513 while (TREE_CODE (ref_base_b) == COMPONENT_REF
514 || TREE_CODE (ref_base_b) == IMAGPART_EXPR
515 || TREE_CODE (ref_base_b) == REALPART_EXPR)
516 ref_base_b = TREE_OPERAND (ref_base_b, 0);
517
518 if (!operand_equal_p (ref_base_a, ref_base_b, 0))
519 {
520 tree cb = bb_predicate (gimple_bb (DR_STMT (b)));
521
522 if (DR_RW_UNCONDITIONALLY (b) == 1
523 || is_true_predicate (cb)
524 || is_true_predicate (ca
525 = fold_or_predicates (EXPR_LOCATION (cb), ca, cb)))
526 {
527 DR_RW_UNCONDITIONALLY (a) = 1;
528 DR_RW_UNCONDITIONALLY (b) = 1;
529 found = true;
530 break;
531 }
532 }
533 }
534
535 if (!found)
536 {
537 DR_RW_UNCONDITIONALLY (a) = 0;
538 return false;
539 }
540 }
541
542 return true;
543}
544
545/* Returns true when the memory references of STMT are unconditionally
546 written. In other words, this function returns true when for every
547 data reference A written in STMT, there exist other writes to the
548 same data reference with predicates that add up (OR-up) to the true
549 predicate: this ensures that the data reference A is written on
550 every iteration of the if-converted loop. */
551
552static bool
553write_memrefs_written_at_least_once (gimple stmt,
554 VEC (data_reference_p, heap) *drs)
555{
556 int i, j;
557 data_reference_p a, b;
558 tree ca = bb_predicate (gimple_bb (stmt));
559
560 for (i = 0; VEC_iterate (data_reference_p, drs, i, a); i++)
561 if (DR_STMT (a) == stmt
562 && DR_IS_WRITE (a))
563 {
564 bool found = false;
565 int x = DR_WRITTEN_AT_LEAST_ONCE (a);
566
567 if (x == 0)
568 return false;
569
570 if (x == 1)
571 continue;
572
573 for (j = 0; VEC_iterate (data_reference_p, drs, j, b); j++)
574 if (DR_STMT (b) != stmt
575 && DR_IS_WRITE (b)
576 && same_data_refs_base_objects (a, b))
577 {
578 tree cb = bb_predicate (gimple_bb (DR_STMT (b)));
579
580 if (DR_WRITTEN_AT_LEAST_ONCE (b) == 1
581 || is_true_predicate (cb)
582 || is_true_predicate (ca = fold_or_predicates (EXPR_LOCATION (cb),
583 ca, cb)))
584 {
585 DR_WRITTEN_AT_LEAST_ONCE (a) = 1;
586 DR_WRITTEN_AT_LEAST_ONCE (b) = 1;
587 found = true;
588 break;
589 }
590 }
591
592 if (!found)
593 {
594 DR_WRITTEN_AT_LEAST_ONCE (a) = 0;
595 return false;
596 }
597 }
598
599 return true;
600}
601
602/* Return true when the memory references of STMT won't trap in the
603 if-converted code. There are two things that we have to check for:
604
605 - writes to memory occur to writable memory: if-conversion of
606 memory writes transforms the conditional memory writes into
607 unconditional writes, i.e. "if (cond) A[i] = foo" is transformed
608 into "A[i] = cond ? foo : A[i]", and as the write to memory may not
609 be executed at all in the original code, it may be a readonly
610 memory. To check that A is not const-qualified, we check that
611 there exists at least an unconditional write to A in the current
612 function.
613
614 - reads or writes to memory are valid memory accesses for every
615 iteration. To check that the memory accesses are correctly formed
616 and that we are allowed to read and write in these locations, we
617 check that the memory accesses to be if-converted occur at every
618 iteration unconditionally. */
619
620static bool
621ifcvt_memrefs_wont_trap (gimple stmt, VEC (data_reference_p, heap) *refs)
622{
623 return write_memrefs_written_at_least_once (stmt, refs)
624 && memrefs_read_or_written_unconditionally (stmt, refs);
625}
626
627/* Wrapper around gimple_could_trap_p refined for the needs of the
628 if-conversion. Try to prove that the memory accesses of STMT could
629 not trap in the innermost loop containing STMT. */
630
631static bool
632ifcvt_could_trap_p (gimple stmt, VEC (data_reference_p, heap) *refs)
633{
634 if (gimple_vuse (stmt)
635 && !gimple_could_trap_p_1 (stmt, false, false)
636 && ifcvt_memrefs_wont_trap (stmt, refs))
637 return false;
638
639 return gimple_could_trap_p (stmt);
640}
641
642/* Return true when STMT is if-convertible.
643
644 GIMPLE_ASSIGN statement is not if-convertible if,
645 - it is not movable,
646 - it could trap,
647 - LHS is not var decl. */
648
649static bool
650if_convertible_gimple_assign_stmt_p (gimple stmt,
651 VEC (data_reference_p, heap) *refs)
652{
653 tree lhs = gimple_assign_lhs (stmt);
654 basic_block bb;
655
656 if (dump_file && (dump_flags & TDF_DETAILS))
657 {
658 fprintf (dump_file, "-------------------------\n");
659 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
660 }
661
662 if (!is_gimple_reg_type (TREE_TYPE (lhs)))
663 return false;
664
665 /* Some of these constrains might be too conservative. */
666 if (stmt_ends_bb_p (stmt)
667 || gimple_has_volatile_ops (stmt)
668 || (TREE_CODE (lhs) == SSA_NAME
669 && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
670 || gimple_has_side_effects (stmt))
671 {
672 if (dump_file && (dump_flags & TDF_DETAILS))
673 fprintf (dump_file, "stmt not suitable for ifcvt\n");
674 return false;
675 }
676
677 if (flag_tree_loop_if_convert_stores)
678 {
679 if (ifcvt_could_trap_p (stmt, refs))
680 {
681 if (dump_file && (dump_flags & TDF_DETAILS))
682 fprintf (dump_file, "tree could trap...\n");
683 return false;
684 }
685 return true;
686 }
687
688 if (gimple_assign_rhs_could_trap_p (stmt))
689 {
690 if (dump_file && (dump_flags & TDF_DETAILS))
691 fprintf (dump_file, "tree could trap...\n");
692 return false;
693 }
694
695 bb = gimple_bb (stmt);
696
697 if (TREE_CODE (lhs) != SSA_NAME
698 && bb != bb->loop_father->header
699 && !bb_with_exit_edge_p (bb->loop_father, bb))
700 {
701 if (dump_file && (dump_flags & TDF_DETAILS))
702 {
703 fprintf (dump_file, "LHS is not var\n");
704 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
705 }
706 return false;
707 }
708
709 return true;
710}
711
712/* Return true when STMT is if-convertible.
713
714 A statement is if-convertible if:
715 - it is an if-convertible GIMPLE_ASSGIN,
716 - it is a GIMPLE_LABEL or a GIMPLE_COND. */
717
718static bool
719if_convertible_stmt_p (gimple stmt, VEC (data_reference_p, heap) *refs)
720{
721 switch (gimple_code (stmt))
722 {
723 case GIMPLE_LABEL:
724 case GIMPLE_DEBUG:
725 case GIMPLE_COND:
726 return true;
727
728 case GIMPLE_ASSIGN:
729 return if_convertible_gimple_assign_stmt_p (stmt, refs);
730
731 case GIMPLE_CALL:
732 {
733 tree fndecl = gimple_call_fndecl (stmt);
734 if (fndecl)
735 {
736 int flags = gimple_call_flags (stmt);
737 if ((flags & ECF_CONST)
738 && !(flags & ECF_LOOPING_CONST_OR_PURE)
739 /* We can only vectorize some builtins at the moment,
740 so restrict if-conversion to those. */
741 && DECL_BUILT_IN (fndecl))
742 return true;
743 }
744 return false;
745 }
746
747 default:
748 /* Don't know what to do with 'em so don't do anything. */
749 if (dump_file && (dump_flags & TDF_DETAILS))
750 {
751 fprintf (dump_file, "don't know what to do\n");
752 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
753 }
754 return false;
755 break;
756 }
757
758 return true;
759}
760
e4b17023
JM
761/* Return true when BB is if-convertible. This routine does not check
762 basic block's statements and phis.
763
764 A basic block is not if-convertible if:
765 - it is non-empty and it is after the exit block (in BFS order),
766 - it is after the exit block but before the latch,
767 - its edges are not normal.
768
769 EXIT_BB is the basic block containing the exit of the LOOP. BB is
770 inside LOOP. */
771
772static bool
773if_convertible_bb_p (struct loop *loop, basic_block bb, basic_block exit_bb)
774{
775 edge e;
776 edge_iterator ei;
777
778 if (dump_file && (dump_flags & TDF_DETAILS))
779 fprintf (dump_file, "----------[%d]-------------\n", bb->index);
780
781 if (EDGE_COUNT (bb->preds) > 2
782 || EDGE_COUNT (bb->succs) > 2)
783 return false;
784
785 if (exit_bb)
786 {
787 if (bb != loop->latch)
788 {
789 if (dump_file && (dump_flags & TDF_DETAILS))
790 fprintf (dump_file, "basic block after exit bb but before latch\n");
791 return false;
792 }
793 else if (!empty_block_p (bb))
794 {
795 if (dump_file && (dump_flags & TDF_DETAILS))
796 fprintf (dump_file, "non empty basic block after exit bb\n");
797 return false;
798 }
799 else if (bb == loop->latch
800 && bb != exit_bb
801 && !dominated_by_p (CDI_DOMINATORS, bb, exit_bb))
802 {
803 if (dump_file && (dump_flags & TDF_DETAILS))
804 fprintf (dump_file, "latch is not dominated by exit_block\n");
805 return false;
806 }
807 }
808
809 /* Be less adventurous and handle only normal edges. */
810 FOR_EACH_EDGE (e, ei, bb->succs)
811 if (e->flags &
812 (EDGE_ABNORMAL_CALL | EDGE_EH | EDGE_ABNORMAL | EDGE_IRREDUCIBLE_LOOP))
813 {
814 if (dump_file && (dump_flags & TDF_DETAILS))
815 fprintf (dump_file, "Difficult to handle edges\n");
816 return false;
817 }
818
95d28233
JM
819 /* At least one incoming edge has to be non-critical as otherwise edge
820 predicates are not equal to basic-block predicates of the edge
821 source. */
822 if (EDGE_COUNT (bb->preds) > 1
823 && bb != loop->header)
824 {
825 bool found = false;
826 FOR_EACH_EDGE (e, ei, bb->preds)
827 if (EDGE_COUNT (e->src->succs) == 1)
828 found = true;
829 if (!found)
830 {
831 if (dump_file && (dump_flags & TDF_DETAILS))
832 fprintf (dump_file, "only critical predecessors\n");
833 return false;
834 }
835 }
e4b17023
JM
836
837 return true;
838}
839
840/* Return true when all predecessor blocks of BB are visited. The
841 VISITED bitmap keeps track of the visited blocks. */
842
843static bool
844pred_blocks_visited_p (basic_block bb, bitmap *visited)
845{
846 edge e;
847 edge_iterator ei;
848 FOR_EACH_EDGE (e, ei, bb->preds)
849 if (!bitmap_bit_p (*visited, e->src->index))
850 return false;
851
852 return true;
853}
854
855/* Get body of a LOOP in suitable order for if-conversion. It is
856 caller's responsibility to deallocate basic block list.
857 If-conversion suitable order is, breadth first sort (BFS) order
858 with an additional constraint: select a block only if all its
859 predecessors are already selected. */
860
861static basic_block *
862get_loop_body_in_if_conv_order (const struct loop *loop)
863{
864 basic_block *blocks, *blocks_in_bfs_order;
865 basic_block bb;
866 bitmap visited;
867 unsigned int index = 0;
868 unsigned int visited_count = 0;
869
870 gcc_assert (loop->num_nodes);
871 gcc_assert (loop->latch != EXIT_BLOCK_PTR);
872
873 blocks = XCNEWVEC (basic_block, loop->num_nodes);
874 visited = BITMAP_ALLOC (NULL);
875
876 blocks_in_bfs_order = get_loop_body_in_bfs_order (loop);
877
878 index = 0;
879 while (index < loop->num_nodes)
880 {
881 bb = blocks_in_bfs_order [index];
882
883 if (bb->flags & BB_IRREDUCIBLE_LOOP)
884 {
885 free (blocks_in_bfs_order);
886 BITMAP_FREE (visited);
887 free (blocks);
888 return NULL;
889 }
890
891 if (!bitmap_bit_p (visited, bb->index))
892 {
893 if (pred_blocks_visited_p (bb, &visited)
894 || bb == loop->header)
895 {
896 /* This block is now visited. */
897 bitmap_set_bit (visited, bb->index);
898 blocks[visited_count++] = bb;
899 }
900 }
901
902 index++;
903
904 if (index == loop->num_nodes
905 && visited_count != loop->num_nodes)
906 /* Not done yet. */
907 index = 0;
908 }
909 free (blocks_in_bfs_order);
910 BITMAP_FREE (visited);
911 return blocks;
912}
913
914/* Returns true when the analysis of the predicates for all the basic
915 blocks in LOOP succeeded.
916
917 predicate_bbs first allocates the predicates of the basic blocks.
918 These fields are then initialized with the tree expressions
919 representing the predicates under which a basic block is executed
920 in the LOOP. As the loop->header is executed at each iteration, it
921 has the "true" predicate. Other statements executed under a
922 condition are predicated with that condition, for example
923
924 | if (x)
925 | S1;
926 | else
927 | S2;
928
929 S1 will be predicated with "x", and
930 S2 will be predicated with "!x". */
931
932static bool
933predicate_bbs (loop_p loop)
934{
935 unsigned int i;
936
937 for (i = 0; i < loop->num_nodes; i++)
938 init_bb_predicate (ifc_bbs[i]);
939
940 for (i = 0; i < loop->num_nodes; i++)
941 {
942 basic_block bb = ifc_bbs[i];
943 tree cond;
944 gimple_stmt_iterator itr;
945
946 /* The loop latch is always executed and has no extra conditions
947 to be processed: skip it. */
948 if (bb == loop->latch)
949 {
950 reset_bb_predicate (loop->latch);
951 continue;
952 }
953
954 cond = bb_predicate (bb);
955
956 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
957 {
958 gimple stmt = gsi_stmt (itr);
959
960 switch (gimple_code (stmt))
961 {
962 case GIMPLE_LABEL:
963 case GIMPLE_ASSIGN:
964 case GIMPLE_CALL:
965 case GIMPLE_DEBUG:
966 break;
967
968 case GIMPLE_COND:
969 {
970 tree c2, tem;
971 edge true_edge, false_edge;
972 location_t loc = gimple_location (stmt);
973 tree c = fold_build2_loc (loc, gimple_cond_code (stmt),
974 boolean_type_node,
975 gimple_cond_lhs (stmt),
976 gimple_cond_rhs (stmt));
977
978 /* Add new condition into destination's predicate list. */
979 extract_true_false_edges_from_block (gimple_bb (stmt),
980 &true_edge, &false_edge);
981
982 /* If C is true, then TRUE_EDGE is taken. */
983 add_to_dst_predicate_list (loop, true_edge,
984 unshare_expr (cond),
985 unshare_expr (c));
986
987 /* If C is false, then FALSE_EDGE is taken. */
988 c2 = invert_truthvalue_loc (loc, unshare_expr (c));
989 tem = canonicalize_cond_expr_cond (c2);
990 if (tem)
991 c2 = tem;
992 add_to_dst_predicate_list (loop, false_edge,
993 unshare_expr (cond), c2);
994
995 cond = NULL_TREE;
996 break;
997 }
998
999 default:
1000 /* Not handled yet in if-conversion. */
1001 return false;
1002 }
1003 }
1004
1005 /* If current bb has only one successor, then consider it as an
1006 unconditional goto. */
1007 if (single_succ_p (bb))
1008 {
1009 basic_block bb_n = single_succ (bb);
1010
1011 /* The successor bb inherits the predicate of its
1012 predecessor. If there is no predicate in the predecessor
1013 bb, then consider the successor bb as always executed. */
1014 if (cond == NULL_TREE)
1015 cond = boolean_true_node;
1016
1017 add_to_predicate_list (bb_n, cond);
1018 }
1019 }
1020
1021 /* The loop header is always executed. */
1022 reset_bb_predicate (loop->header);
1023 gcc_assert (bb_predicate_gimplified_stmts (loop->header) == NULL
1024 && bb_predicate_gimplified_stmts (loop->latch) == NULL);
1025
1026 return true;
1027}
1028
1029/* Return true when LOOP is if-convertible. This is a helper function
1030 for if_convertible_loop_p. REFS and DDRS are initialized and freed
1031 in if_convertible_loop_p. */
1032
1033static bool
1034if_convertible_loop_p_1 (struct loop *loop,
1035 VEC (loop_p, heap) **loop_nest,
1036 VEC (data_reference_p, heap) **refs,
1037 VEC (ddr_p, heap) **ddrs)
1038{
1039 bool res;
1040 unsigned int i;
1041 basic_block exit_bb = NULL;
1042
1043 /* Don't if-convert the loop when the data dependences cannot be
1044 computed: the loop won't be vectorized in that case. */
1045 res = compute_data_dependences_for_loop (loop, true, loop_nest, refs, ddrs);
1046 if (!res)
1047 return false;
1048
1049 calculate_dominance_info (CDI_DOMINATORS);
e4b17023
JM
1050
1051 /* Allow statements that can be handled during if-conversion. */
1052 ifc_bbs = get_loop_body_in_if_conv_order (loop);
1053 if (!ifc_bbs)
1054 {
1055 if (dump_file && (dump_flags & TDF_DETAILS))
1056 fprintf (dump_file, "Irreducible loop\n");
1057 return false;
1058 }
1059
1060 for (i = 0; i < loop->num_nodes; i++)
1061 {
1062 basic_block bb = ifc_bbs[i];
1063
1064 if (!if_convertible_bb_p (loop, bb, exit_bb))
1065 return false;
1066
1067 if (bb_with_exit_edge_p (loop, bb))
1068 exit_bb = bb;
1069 }
1070
1071 res = predicate_bbs (loop);
1072 if (!res)
1073 return false;
1074
1075 if (flag_tree_loop_if_convert_stores)
1076 {
1077 data_reference_p dr;
1078
1079 for (i = 0; VEC_iterate (data_reference_p, *refs, i, dr); i++)
1080 {
1081 dr->aux = XNEW (struct ifc_dr);
1082 DR_WRITTEN_AT_LEAST_ONCE (dr) = -1;
1083 DR_RW_UNCONDITIONALLY (dr) = -1;
1084 }
1085 }
1086
1087 for (i = 0; i < loop->num_nodes; i++)
1088 {
1089 basic_block bb = ifc_bbs[i];
1090 gimple_stmt_iterator itr;
1091
1092 for (itr = gsi_start_phis (bb); !gsi_end_p (itr); gsi_next (&itr))
1093 if (!if_convertible_phi_p (loop, bb, gsi_stmt (itr)))
1094 return false;
1095
1096 /* Check the if-convertibility of statements in predicated BBs. */
1097 if (is_predicated (bb))
1098 for (itr = gsi_start_bb (bb); !gsi_end_p (itr); gsi_next (&itr))
1099 if (!if_convertible_stmt_p (gsi_stmt (itr), *refs))
1100 return false;
1101 }
1102
1103 if (dump_file)
1104 fprintf (dump_file, "Applying if-conversion\n");
1105
1106 return true;
1107}
1108
1109/* Return true when LOOP is if-convertible.
1110 LOOP is if-convertible if:
1111 - it is innermost,
1112 - it has two or more basic blocks,
1113 - it has only one exit,
1114 - loop header is not the exit edge,
1115 - if its basic blocks and phi nodes are if convertible. */
1116
1117static bool
1118if_convertible_loop_p (struct loop *loop)
1119{
1120 edge e;
1121 edge_iterator ei;
1122 bool res = false;
1123 VEC (data_reference_p, heap) *refs;
1124 VEC (ddr_p, heap) *ddrs;
1125 VEC (loop_p, heap) *loop_nest;
1126
1127 /* Handle only innermost loop. */
1128 if (!loop || loop->inner)
1129 {
1130 if (dump_file && (dump_flags & TDF_DETAILS))
1131 fprintf (dump_file, "not innermost loop\n");
1132 return false;
1133 }
1134
1135 /* If only one block, no need for if-conversion. */
1136 if (loop->num_nodes <= 2)
1137 {
1138 if (dump_file && (dump_flags & TDF_DETAILS))
1139 fprintf (dump_file, "less than 2 basic blocks\n");
1140 return false;
1141 }
1142
1143 /* More than one loop exit is too much to handle. */
1144 if (!single_exit (loop))
1145 {
1146 if (dump_file && (dump_flags & TDF_DETAILS))
1147 fprintf (dump_file, "multiple exits\n");
1148 return false;
1149 }
1150
1151 /* If one of the loop header's edge is an exit edge then do not
1152 apply if-conversion. */
1153 FOR_EACH_EDGE (e, ei, loop->header->succs)
1154 if (loop_exit_edge_p (loop, e))
1155 return false;
1156
1157 refs = VEC_alloc (data_reference_p, heap, 5);
1158 ddrs = VEC_alloc (ddr_p, heap, 25);
1159 loop_nest = VEC_alloc (loop_p, heap, 3);
1160 res = if_convertible_loop_p_1 (loop, &loop_nest, &refs, &ddrs);
1161
1162 if (flag_tree_loop_if_convert_stores)
1163 {
1164 data_reference_p dr;
1165 unsigned int i;
1166
1167 for (i = 0; VEC_iterate (data_reference_p, refs, i, dr); i++)
1168 free (dr->aux);
1169 }
1170
1171 VEC_free (loop_p, heap, loop_nest);
1172 free_data_refs (refs);
1173 free_dependence_relations (ddrs);
1174 return res;
1175}
1176
1177/* Basic block BB has two predecessors. Using predecessor's bb
1178 predicate, set an appropriate condition COND for the PHI node
1179 replacement. Return the true block whose phi arguments are
1180 selected when cond is true. LOOP is the loop containing the
1181 if-converted region, GSI is the place to insert the code for the
1182 if-conversion. */
1183
1184static basic_block
95d28233 1185find_phi_replacement_condition (basic_block bb, tree *cond,
e4b17023
JM
1186 gimple_stmt_iterator *gsi)
1187{
1188 edge first_edge, second_edge;
1189 tree tmp_cond;
1190
1191 gcc_assert (EDGE_COUNT (bb->preds) == 2);
1192 first_edge = EDGE_PRED (bb, 0);
1193 second_edge = EDGE_PRED (bb, 1);
1194
95d28233
JM
1195 /* Prefer an edge with a not negated predicate.
1196 ??? That's a very weak cost model. */
e4b17023
JM
1197 tmp_cond = bb_predicate (first_edge->src);
1198 gcc_assert (tmp_cond);
e4b17023
JM
1199 if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
1200 {
1201 edge tmp_edge;
1202
1203 tmp_edge = first_edge;
1204 first_edge = second_edge;
1205 second_edge = tmp_edge;
1206 }
1207
95d28233
JM
1208 /* Check if the edge we take the condition from is not critical.
1209 We know that at least one non-critical edge exists. */
1210 if (EDGE_COUNT (first_edge->src->succs) > 1)
e4b17023
JM
1211 {
1212 *cond = bb_predicate (second_edge->src);
1213
1214 if (TREE_CODE (*cond) == TRUTH_NOT_EXPR)
1215 *cond = TREE_OPERAND (*cond, 0);
1216 else
1217 /* Select non loop header bb. */
1218 first_edge = second_edge;
1219 }
1220 else
1221 *cond = bb_predicate (first_edge->src);
1222
1223 /* Gimplify the condition to a valid cond-expr conditonal operand. */
1224 *cond = force_gimple_operand_gsi_1 (gsi, unshare_expr (*cond),
1225 is_gimple_condexpr, NULL_TREE,
1226 true, GSI_SAME_STMT);
1227
1228 return first_edge->src;
1229}
1230
1231/* Replace a scalar PHI node with a COND_EXPR using COND as condition.
1232 This routine does not handle PHI nodes with more than two
1233 arguments.
1234
1235 For example,
1236 S1: A = PHI <x1(1), x2(5)>
1237 is converted into,
1238 S2: A = cond ? x1 : x2;
1239
1240 The generated code is inserted at GSI that points to the top of
1241 basic block's statement list. When COND is true, phi arg from
1242 TRUE_BB is selected. */
1243
1244static void
1245predicate_scalar_phi (gimple phi, tree cond,
1246 basic_block true_bb,
1247 gimple_stmt_iterator *gsi)
1248{
1249 gimple new_stmt;
1250 basic_block bb;
1251 tree rhs, res, arg, scev;
1252
1253 gcc_assert (gimple_code (phi) == GIMPLE_PHI
1254 && gimple_phi_num_args (phi) == 2);
1255
1256 res = gimple_phi_result (phi);
1257 /* Do not handle virtual phi nodes. */
1258 if (!is_gimple_reg (SSA_NAME_VAR (res)))
1259 return;
1260
1261 bb = gimple_bb (phi);
1262
1263 if ((arg = degenerate_phi_result (phi))
1264 || ((scev = analyze_scalar_evolution (gimple_bb (phi)->loop_father,
1265 res))
1266 && !chrec_contains_undetermined (scev)
1267 && scev != res
1268 && (arg = gimple_phi_arg_def (phi, 0))))
1269 rhs = arg;
1270 else
1271 {
1272 tree arg_0, arg_1;
1273 /* Use condition that is not TRUTH_NOT_EXPR in conditional modify expr. */
1274 if (EDGE_PRED (bb, 1)->src == true_bb)
1275 {
1276 arg_0 = gimple_phi_arg_def (phi, 1);
1277 arg_1 = gimple_phi_arg_def (phi, 0);
1278 }
1279 else
1280 {
1281 arg_0 = gimple_phi_arg_def (phi, 0);
1282 arg_1 = gimple_phi_arg_def (phi, 1);
1283 }
1284
e4b17023
JM
1285 /* Build new RHS using selected condition and arguments. */
1286 rhs = build3 (COND_EXPR, TREE_TYPE (res),
1287 unshare_expr (cond), arg_0, arg_1);
1288 }
1289
1290 new_stmt = gimple_build_assign (res, rhs);
1291 SSA_NAME_DEF_STMT (gimple_phi_result (phi)) = new_stmt;
1292 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
1293 update_stmt (new_stmt);
1294
1295 if (dump_file && (dump_flags & TDF_DETAILS))
1296 {
1297 fprintf (dump_file, "new phi replacement stmt\n");
1298 print_gimple_stmt (dump_file, new_stmt, 0, TDF_SLIM);
1299 }
1300}
1301
1302/* Replaces in LOOP all the scalar phi nodes other than those in the
1303 LOOP->header block with conditional modify expressions. */
1304
1305static void
1306predicate_all_scalar_phis (struct loop *loop)
1307{
1308 basic_block bb;
1309 unsigned int orig_loop_num_nodes = loop->num_nodes;
1310 unsigned int i;
1311
1312 for (i = 1; i < orig_loop_num_nodes; i++)
1313 {
1314 gimple phi;
1315 tree cond = NULL_TREE;
1316 gimple_stmt_iterator gsi, phi_gsi;
1317 basic_block true_bb = NULL;
1318 bb = ifc_bbs[i];
1319
1320 if (bb == loop->header)
1321 continue;
1322
1323 phi_gsi = gsi_start_phis (bb);
1324 if (gsi_end_p (phi_gsi))
1325 continue;
1326
1327 /* BB has two predecessors. Using predecessor's aux field, set
1328 appropriate condition for the PHI node replacement. */
1329 gsi = gsi_after_labels (bb);
95d28233 1330 true_bb = find_phi_replacement_condition (bb, &cond, &gsi);
e4b17023
JM
1331
1332 while (!gsi_end_p (phi_gsi))
1333 {
1334 phi = gsi_stmt (phi_gsi);
1335 predicate_scalar_phi (phi, cond, true_bb, &gsi);
1336 release_phi_node (phi);
1337 gsi_next (&phi_gsi);
1338 }
1339
1340 set_phi_nodes (bb, NULL);
1341 }
1342}
1343
1344/* Insert in each basic block of LOOP the statements produced by the
1345 gimplification of the predicates. */
1346
1347static void
1348insert_gimplified_predicates (loop_p loop)
1349{
1350 unsigned int i;
1351
1352 for (i = 0; i < loop->num_nodes; i++)
1353 {
1354 basic_block bb = ifc_bbs[i];
1355 gimple_seq stmts;
1356
1357 if (!is_predicated (bb))
1358 {
1359 /* Do not insert statements for a basic block that is not
1360 predicated. Also make sure that the predicate of the
1361 basic block is set to true. */
1362 reset_bb_predicate (bb);
1363 continue;
1364 }
1365
1366 stmts = bb_predicate_gimplified_stmts (bb);
1367 if (stmts)
1368 {
1369 if (flag_tree_loop_if_convert_stores)
1370 {
1371 /* Insert the predicate of the BB just after the label,
1372 as the if-conversion of memory writes will use this
1373 predicate. */
1374 gimple_stmt_iterator gsi = gsi_after_labels (bb);
1375 gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
1376 }
1377 else
1378 {
1379 /* Insert the predicate of the BB at the end of the BB
1380 as this would reduce the register pressure: the only
1381 use of this predicate will be in successor BBs. */
1382 gimple_stmt_iterator gsi = gsi_last_bb (bb);
1383
1384 if (gsi_end_p (gsi)
1385 || stmt_ends_bb_p (gsi_stmt (gsi)))
1386 gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
1387 else
1388 gsi_insert_seq_after (&gsi, stmts, GSI_SAME_STMT);
1389 }
1390
1391 /* Once the sequence is code generated, set it to NULL. */
1392 set_bb_predicate_gimplified_stmts (bb, NULL);
1393 }
1394 }
1395}
1396
1397/* Predicate each write to memory in LOOP.
1398
1399 This function transforms control flow constructs containing memory
1400 writes of the form:
1401
1402 | for (i = 0; i < N; i++)
1403 | if (cond)
1404 | A[i] = expr;
1405
1406 into the following form that does not contain control flow:
1407
1408 | for (i = 0; i < N; i++)
1409 | A[i] = cond ? expr : A[i];
1410
1411 The original CFG looks like this:
1412
1413 | bb_0
1414 | i = 0
1415 | end_bb_0
1416 |
1417 | bb_1
1418 | if (i < N) goto bb_5 else goto bb_2
1419 | end_bb_1
1420 |
1421 | bb_2
1422 | cond = some_computation;
1423 | if (cond) goto bb_3 else goto bb_4
1424 | end_bb_2
1425 |
1426 | bb_3
1427 | A[i] = expr;
1428 | goto bb_4
1429 | end_bb_3
1430 |
1431 | bb_4
1432 | goto bb_1
1433 | end_bb_4
1434
1435 insert_gimplified_predicates inserts the computation of the COND
1436 expression at the beginning of the destination basic block:
1437
1438 | bb_0
1439 | i = 0
1440 | end_bb_0
1441 |
1442 | bb_1
1443 | if (i < N) goto bb_5 else goto bb_2
1444 | end_bb_1
1445 |
1446 | bb_2
1447 | cond = some_computation;
1448 | if (cond) goto bb_3 else goto bb_4
1449 | end_bb_2
1450 |
1451 | bb_3
1452 | cond = some_computation;
1453 | A[i] = expr;
1454 | goto bb_4
1455 | end_bb_3
1456 |
1457 | bb_4
1458 | goto bb_1
1459 | end_bb_4
1460
1461 predicate_mem_writes is then predicating the memory write as follows:
1462
1463 | bb_0
1464 | i = 0
1465 | end_bb_0
1466 |
1467 | bb_1
1468 | if (i < N) goto bb_5 else goto bb_2
1469 | end_bb_1
1470 |
1471 | bb_2
1472 | if (cond) goto bb_3 else goto bb_4
1473 | end_bb_2
1474 |
1475 | bb_3
1476 | cond = some_computation;
1477 | A[i] = cond ? expr : A[i];
1478 | goto bb_4
1479 | end_bb_3
1480 |
1481 | bb_4
1482 | goto bb_1
1483 | end_bb_4
1484
1485 and finally combine_blocks removes the basic block boundaries making
1486 the loop vectorizable:
1487
1488 | bb_0
1489 | i = 0
1490 | if (i < N) goto bb_5 else goto bb_1
1491 | end_bb_0
1492 |
1493 | bb_1
1494 | cond = some_computation;
1495 | A[i] = cond ? expr : A[i];
1496 | if (i < N) goto bb_5 else goto bb_4
1497 | end_bb_1
1498 |
1499 | bb_4
1500 | goto bb_1
1501 | end_bb_4
1502*/
1503
1504static void
1505predicate_mem_writes (loop_p loop)
1506{
1507 unsigned int i, orig_loop_num_nodes = loop->num_nodes;
1508
1509 for (i = 1; i < orig_loop_num_nodes; i++)
1510 {
1511 gimple_stmt_iterator gsi;
1512 basic_block bb = ifc_bbs[i];
1513 tree cond = bb_predicate (bb);
1514 bool swap;
1515 gimple stmt;
1516
1517 if (is_true_predicate (cond))
1518 continue;
1519
1520 swap = false;
1521 if (TREE_CODE (cond) == TRUTH_NOT_EXPR)
1522 {
1523 swap = true;
1524 cond = TREE_OPERAND (cond, 0);
1525 }
1526
1527 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1528 if ((stmt = gsi_stmt (gsi))
1529 && gimple_assign_single_p (stmt)
1530 && gimple_vdef (stmt))
1531 {
1532 tree lhs = gimple_assign_lhs (stmt);
1533 tree rhs = gimple_assign_rhs1 (stmt);
1534 tree type = TREE_TYPE (lhs);
1535
1536 lhs = ifc_temp_var (type, unshare_expr (lhs), &gsi);
1537 rhs = ifc_temp_var (type, unshare_expr (rhs), &gsi);
1538 if (swap)
1539 {
1540 tree tem = lhs;
1541 lhs = rhs;
1542 rhs = tem;
1543 }
1544 cond = force_gimple_operand_gsi_1 (&gsi, unshare_expr (cond),
1545 is_gimple_condexpr, NULL_TREE,
1546 true, GSI_SAME_STMT);
1547 rhs = build3 (COND_EXPR, type, unshare_expr (cond), rhs, lhs);
1548 gimple_assign_set_rhs1 (stmt, ifc_temp_var (type, rhs, &gsi));
1549 update_stmt (stmt);
1550 }
1551 }
1552}
1553
1554/* Remove all GIMPLE_CONDs and GIMPLE_LABELs of all the basic blocks
1555 other than the exit and latch of the LOOP. Also resets the
1556 GIMPLE_DEBUG information. */
1557
1558static void
1559remove_conditions_and_labels (loop_p loop)
1560{
1561 gimple_stmt_iterator gsi;
1562 unsigned int i;
1563
1564 for (i = 0; i < loop->num_nodes; i++)
1565 {
1566 basic_block bb = ifc_bbs[i];
1567
1568 if (bb_with_exit_edge_p (loop, bb)
1569 || bb == loop->latch)
1570 continue;
1571
1572 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
1573 switch (gimple_code (gsi_stmt (gsi)))
1574 {
1575 case GIMPLE_COND:
1576 case GIMPLE_LABEL:
1577 gsi_remove (&gsi, true);
1578 break;
1579
1580 case GIMPLE_DEBUG:
1581 /* ??? Should there be conditional GIMPLE_DEBUG_BINDs? */
1582 if (gimple_debug_bind_p (gsi_stmt (gsi)))
1583 {
1584 gimple_debug_bind_reset_value (gsi_stmt (gsi));
1585 update_stmt (gsi_stmt (gsi));
1586 }
1587 gsi_next (&gsi);
1588 break;
1589
1590 default:
1591 gsi_next (&gsi);
1592 }
1593 }
1594}
1595
1596/* Combine all the basic blocks from LOOP into one or two super basic
1597 blocks. Replace PHI nodes with conditional modify expressions. */
1598
1599static void
1600combine_blocks (struct loop *loop)
1601{
1602 basic_block bb, exit_bb, merge_target_bb;
1603 unsigned int orig_loop_num_nodes = loop->num_nodes;
1604 unsigned int i;
1605 edge e;
1606 edge_iterator ei;
1607
1608 remove_conditions_and_labels (loop);
1609 insert_gimplified_predicates (loop);
1610 predicate_all_scalar_phis (loop);
1611
1612 if (flag_tree_loop_if_convert_stores)
1613 predicate_mem_writes (loop);
1614
1615 /* Merge basic blocks: first remove all the edges in the loop,
1616 except for those from the exit block. */
1617 exit_bb = NULL;
1618 for (i = 0; i < orig_loop_num_nodes; i++)
1619 {
1620 bb = ifc_bbs[i];
1621 free_bb_predicate (bb);
1622 if (bb_with_exit_edge_p (loop, bb))
1623 {
1624 exit_bb = bb;
1625 break;
1626 }
1627 }
1628 gcc_assert (exit_bb != loop->latch);
1629
1630 for (i = 1; i < orig_loop_num_nodes; i++)
1631 {
1632 bb = ifc_bbs[i];
1633
1634 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei));)
1635 {
1636 if (e->src == exit_bb)
1637 ei_next (&ei);
1638 else
1639 remove_edge (e);
1640 }
1641 }
1642
1643 if (exit_bb != NULL)
1644 {
1645 if (exit_bb != loop->header)
1646 {
1647 /* Connect this node to loop header. */
1648 make_edge (loop->header, exit_bb, EDGE_FALLTHRU);
1649 set_immediate_dominator (CDI_DOMINATORS, exit_bb, loop->header);
1650 }
1651
1652 /* Redirect non-exit edges to loop->latch. */
1653 FOR_EACH_EDGE (e, ei, exit_bb->succs)
1654 {
1655 if (!loop_exit_edge_p (loop, e))
1656 redirect_edge_and_branch (e, loop->latch);
1657 }
1658 set_immediate_dominator (CDI_DOMINATORS, loop->latch, exit_bb);
1659 }
1660 else
1661 {
1662 /* If the loop does not have an exit, reconnect header and latch. */
1663 make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
1664 set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
1665 }
1666
1667 merge_target_bb = loop->header;
1668 for (i = 1; i < orig_loop_num_nodes; i++)
1669 {
1670 gimple_stmt_iterator gsi;
1671 gimple_stmt_iterator last;
1672
1673 bb = ifc_bbs[i];
1674
1675 if (bb == exit_bb || bb == loop->latch)
1676 continue;
1677
1678 /* Make stmts member of loop->header. */
1679 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1680 gimple_set_bb (gsi_stmt (gsi), merge_target_bb);
1681
1682 /* Update stmt list. */
1683 last = gsi_last_bb (merge_target_bb);
1684 gsi_insert_seq_after (&last, bb_seq (bb), GSI_NEW_STMT);
1685 set_bb_seq (bb, NULL);
1686
1687 delete_basic_block (bb);
1688 }
1689
1690 /* If possible, merge loop header to the block with the exit edge.
1691 This reduces the number of basic blocks to two, to please the
1692 vectorizer that handles only loops with two nodes. */
1693 if (exit_bb
1694 && exit_bb != loop->header
1695 && can_merge_blocks_p (loop->header, exit_bb))
1696 merge_blocks (loop->header, exit_bb);
1697
1698 free (ifc_bbs);
1699 ifc_bbs = NULL;
1700}
1701
1702/* If-convert LOOP when it is legal. For the moment this pass has no
1703 profitability analysis. Returns true when something changed. */
1704
1705static bool
1706tree_if_conversion (struct loop *loop)
1707{
1708 bool changed = false;
1709 ifc_bbs = NULL;
1710
1711 if (!if_convertible_loop_p (loop)
1712 || !dbg_cnt (if_conversion_tree))
1713 goto cleanup;
1714
1715 /* Now all statements are if-convertible. Combine all the basic
1716 blocks into one huge basic block doing the if-conversion
1717 on-the-fly. */
1718 combine_blocks (loop);
1719
1720 if (flag_tree_loop_if_convert_stores)
1721 mark_sym_for_renaming (gimple_vop (cfun));
1722
1723 changed = true;
1724
1725 cleanup:
1726 if (ifc_bbs)
1727 {
1728 unsigned int i;
1729
1730 for (i = 0; i < loop->num_nodes; i++)
1731 free_bb_predicate (ifc_bbs[i]);
1732
1733 free (ifc_bbs);
1734 ifc_bbs = NULL;
1735 }
1736
1737 return changed;
1738}
1739
1740/* Tree if-conversion pass management. */
1741
1742static unsigned int
1743main_tree_if_conversion (void)
1744{
1745 loop_iterator li;
1746 struct loop *loop;
1747 bool changed = false;
1748 unsigned todo = 0;
1749
1750 if (number_of_loops () <= 1)
1751 return 0;
1752
1753 FOR_EACH_LOOP (li, loop, 0)
1754 changed |= tree_if_conversion (loop);
1755
1756 if (changed)
1757 todo |= TODO_cleanup_cfg;
1758
1759 if (changed && flag_tree_loop_if_convert_stores)
1760 todo |= TODO_update_ssa_only_virtuals;
1761
e4b17023
JM
1762 return todo;
1763}
1764
1765/* Returns true when the if-conversion pass is enabled. */
1766
1767static bool
1768gate_tree_if_conversion (void)
1769{
1770 return ((flag_tree_vectorize && flag_tree_loop_if_convert != 0)
1771 || flag_tree_loop_if_convert == 1
1772 || flag_tree_loop_if_convert_stores == 1);
1773}
1774
1775struct gimple_opt_pass pass_if_conversion =
1776{
1777 {
1778 GIMPLE_PASS,
1779 "ifcvt", /* name */
1780 gate_tree_if_conversion, /* gate */
1781 main_tree_if_conversion, /* execute */
1782 NULL, /* sub */
1783 NULL, /* next */
1784 0, /* static_pass_number */
1785 TV_NONE, /* tv_id */
1786 PROP_cfg | PROP_ssa, /* properties_required */
1787 0, /* properties_provided */
1788 0, /* properties_destroyed */
1789 0, /* todo_flags_start */
1790 TODO_verify_stmts | TODO_verify_flow
1791 /* todo_flags_finish */
1792 }
1793};