1 /* Functions to determine/estimate number of iterations of a loop.
2 Copyright (C) 2004-2020 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by the
8 Free Software Foundation; either version 3, or (at your option) any
9 later version.
10
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "backend.h"
24 #include "rtl.h"
25 #include "tree.h"
26 #include "gimple.h"
27 #include "tree-pass.h"
28 #include "ssa.h"
29 #include "gimple-pretty-print.h"
30 #include "diagnostic-core.h"
31 #include "stor-layout.h"
32 #include "fold-const.h"
33 #include "calls.h"
34 #include "intl.h"
35 #include "gimplify.h"
36 #include "gimple-iterator.h"
37 #include "tree-cfg.h"
38 #include "tree-ssa-loop-ivopts.h"
39 #include "tree-ssa-loop-niter.h"
40 #include "tree-ssa-loop.h"
41 #include "cfgloop.h"
42 #include "tree-chrec.h"
43 #include "tree-scalar-evolution.h"
44 #include "tree-dfa.h"
45
46
47 /* The maximum number of dominator BBs we search for conditions
48 of loop header copies we use for simplifying a conditional
49 expression. */
50 #define MAX_DOMINATORS_TO_WALK 8
51
52 /*
53
54 Analysis of number of iterations of an affine exit test.
55
56 */
57
58 /* Bounds on some value, BELOW <= X <= UP. */
59
60 struct bounds
61 {
62 mpz_t below, up;
63 };
64
65 static bool number_of_iterations_popcount (loop_p loop, edge exit,
66 enum tree_code code,
67 class tree_niter_desc *niter);
68
69
70 /* Splits expression EXPR to a variable part VAR and constant OFFSET. */
71
72 static void
split_to_var_and_offset(tree expr,tree * var,mpz_t offset)73 split_to_var_and_offset (tree expr, tree *var, mpz_t offset)
74 {
75 tree type = TREE_TYPE (expr);
76 tree op0, op1;
77 bool negate = false;
78
79 *var = expr;
80 mpz_set_ui (offset, 0);
81
82 switch (TREE_CODE (expr))
83 {
84 case MINUS_EXPR:
85 negate = true;
86 /* Fallthru. */
87
88 case PLUS_EXPR:
89 case POINTER_PLUS_EXPR:
90 op0 = TREE_OPERAND (expr, 0);
91 op1 = TREE_OPERAND (expr, 1);
92
93 if (TREE_CODE (op1) != INTEGER_CST)
94 break;
95
96 *var = op0;
97 /* Always sign extend the offset. */
98 wi::to_mpz (wi::to_wide (op1), offset, SIGNED);
99 if (negate)
100 mpz_neg (offset, offset);
101 break;
102
103 case INTEGER_CST:
104 *var = build_int_cst_type (type, 0);
105 wi::to_mpz (wi::to_wide (expr), offset, TYPE_SIGN (type));
106 break;
107
108 default:
109 break;
110 }
111 }
112
113 /* From condition C0 CMP C1 derives information regarding the value range
114 of VAR, which is of TYPE. Results are stored in to BELOW and UP. */
115
116 static void
refine_value_range_using_guard(tree type,tree var,tree c0,enum tree_code cmp,tree c1,mpz_t below,mpz_t up)117 refine_value_range_using_guard (tree type, tree var,
118 tree c0, enum tree_code cmp, tree c1,
119 mpz_t below, mpz_t up)
120 {
121 tree varc0, varc1, ctype;
122 mpz_t offc0, offc1;
123 mpz_t mint, maxt, minc1, maxc1;
124 wide_int minv, maxv;
125 bool no_wrap = nowrap_type_p (type);
126 bool c0_ok, c1_ok;
127 signop sgn = TYPE_SIGN (type);
128
129 switch (cmp)
130 {
131 case LT_EXPR:
132 case LE_EXPR:
133 case GT_EXPR:
134 case GE_EXPR:
135 STRIP_SIGN_NOPS (c0);
136 STRIP_SIGN_NOPS (c1);
137 ctype = TREE_TYPE (c0);
138 if (!useless_type_conversion_p (ctype, type))
139 return;
140
141 break;
142
143 case EQ_EXPR:
144 /* We could derive quite precise information from EQ_EXPR, however,
145 such a guard is unlikely to appear, so we do not bother with
146 handling it. */
147 return;
148
149 case NE_EXPR:
150 /* NE_EXPR comparisons do not contain much of useful information,
151 except for cases of comparing with bounds. */
152 if (TREE_CODE (c1) != INTEGER_CST
153 || !INTEGRAL_TYPE_P (type))
154 return;
155
156 /* Ensure that the condition speaks about an expression in the same
157 type as X and Y. */
158 ctype = TREE_TYPE (c0);
159 if (TYPE_PRECISION (ctype) != TYPE_PRECISION (type))
160 return;
161 c0 = fold_convert (type, c0);
162 c1 = fold_convert (type, c1);
163
164 if (operand_equal_p (var, c0, 0))
165 {
166 mpz_t valc1;
167
168 /* Case of comparing VAR with its below/up bounds. */
169 mpz_init (valc1);
170 wi::to_mpz (wi::to_wide (c1), valc1, TYPE_SIGN (type));
171 if (mpz_cmp (valc1, below) == 0)
172 cmp = GT_EXPR;
173 if (mpz_cmp (valc1, up) == 0)
174 cmp = LT_EXPR;
175
176 mpz_clear (valc1);
177 }
178 else
179 {
180 /* Case of comparing with the bounds of the type. */
181 wide_int min = wi::min_value (type);
182 wide_int max = wi::max_value (type);
183
184 if (wi::to_wide (c1) == min)
185 cmp = GT_EXPR;
186 if (wi::to_wide (c1) == max)
187 cmp = LT_EXPR;
188 }
189
190 /* Quick return if no useful information. */
191 if (cmp == NE_EXPR)
192 return;
193
194 break;
195
196 default:
197 return;
198 }
199
200 mpz_init (offc0);
201 mpz_init (offc1);
202 split_to_var_and_offset (expand_simple_operations (c0), &varc0, offc0);
203 split_to_var_and_offset (expand_simple_operations (c1), &varc1, offc1);
204
205 /* We are only interested in comparisons of expressions based on VAR. */
206 if (operand_equal_p (var, varc1, 0))
207 {
208 std::swap (varc0, varc1);
209 mpz_swap (offc0, offc1);
210 cmp = swap_tree_comparison (cmp);
211 }
212 else if (!operand_equal_p (var, varc0, 0))
213 {
214 mpz_clear (offc0);
215 mpz_clear (offc1);
216 return;
217 }
218
219 mpz_init (mint);
220 mpz_init (maxt);
221 get_type_static_bounds (type, mint, maxt);
222 mpz_init (minc1);
223 mpz_init (maxc1);
224 /* Setup range information for varc1. */
225 if (integer_zerop (varc1))
226 {
227 wi::to_mpz (0, minc1, TYPE_SIGN (type));
228 wi::to_mpz (0, maxc1, TYPE_SIGN (type));
229 }
230 else if (TREE_CODE (varc1) == SSA_NAME
231 && INTEGRAL_TYPE_P (type)
232 && get_range_info (varc1, &minv, &maxv) == VR_RANGE)
233 {
234 gcc_assert (wi::le_p (minv, maxv, sgn));
235 wi::to_mpz (minv, minc1, sgn);
236 wi::to_mpz (maxv, maxc1, sgn);
237 }
238 else
239 {
240 mpz_set (minc1, mint);
241 mpz_set (maxc1, maxt);
242 }
243
244 /* Compute valid range information for varc1 + offc1. Note nothing
245 useful can be derived if it overflows or underflows. Overflow or
246 underflow could happen when:
247
248 offc1 > 0 && varc1 + offc1 > MAX_VAL (type)
249 offc1 < 0 && varc1 + offc1 < MIN_VAL (type). */
250 mpz_add (minc1, minc1, offc1);
251 mpz_add (maxc1, maxc1, offc1);
252 c1_ok = (no_wrap
253 || mpz_sgn (offc1) == 0
254 || (mpz_sgn (offc1) < 0 && mpz_cmp (minc1, mint) >= 0)
255 || (mpz_sgn (offc1) > 0 && mpz_cmp (maxc1, maxt) <= 0));
256 if (!c1_ok)
257 goto end;
258
259 if (mpz_cmp (minc1, mint) < 0)
260 mpz_set (minc1, mint);
261 if (mpz_cmp (maxc1, maxt) > 0)
262 mpz_set (maxc1, maxt);
263
264 if (cmp == LT_EXPR)
265 {
266 cmp = LE_EXPR;
267 mpz_sub_ui (maxc1, maxc1, 1);
268 }
269 if (cmp == GT_EXPR)
270 {
271 cmp = GE_EXPR;
272 mpz_add_ui (minc1, minc1, 1);
273 }
274
275 /* Compute range information for varc0. If there is no overflow,
276 the condition implied that
277
278 (varc0) cmp (varc1 + offc1 - offc0)
279
280 We can possibly improve the upper bound of varc0 if cmp is LE_EXPR,
281 or the below bound if cmp is GE_EXPR.
282
283 To prove there is no overflow/underflow, we need to check below
284 four cases:
285 1) cmp == LE_EXPR && offc0 > 0
286
287 (varc0 + offc0) doesn't overflow
288 && (varc1 + offc1 - offc0) doesn't underflow
289
290 2) cmp == LE_EXPR && offc0 < 0
291
292 (varc0 + offc0) doesn't underflow
293 && (varc1 + offc1 - offc0) doesn't overfloe
294
295 In this case, (varc0 + offc0) will never underflow if we can
296 prove (varc1 + offc1 - offc0) doesn't overflow.
297
298 3) cmp == GE_EXPR && offc0 < 0
299
300 (varc0 + offc0) doesn't underflow
301 && (varc1 + offc1 - offc0) doesn't overflow
302
303 4) cmp == GE_EXPR && offc0 > 0
304
305 (varc0 + offc0) doesn't overflow
306 && (varc1 + offc1 - offc0) doesn't underflow
307
308 In this case, (varc0 + offc0) will never overflow if we can
309 prove (varc1 + offc1 - offc0) doesn't underflow.
310
311 Note we only handle case 2 and 4 in below code. */
312
313 mpz_sub (minc1, minc1, offc0);
314 mpz_sub (maxc1, maxc1, offc0);
315 c0_ok = (no_wrap
316 || mpz_sgn (offc0) == 0
317 || (cmp == LE_EXPR
318 && mpz_sgn (offc0) < 0 && mpz_cmp (maxc1, maxt) <= 0)
319 || (cmp == GE_EXPR
320 && mpz_sgn (offc0) > 0 && mpz_cmp (minc1, mint) >= 0));
321 if (!c0_ok)
322 goto end;
323
324 if (cmp == LE_EXPR)
325 {
326 if (mpz_cmp (up, maxc1) > 0)
327 mpz_set (up, maxc1);
328 }
329 else
330 {
331 if (mpz_cmp (below, minc1) < 0)
332 mpz_set (below, minc1);
333 }
334
335 end:
336 mpz_clear (mint);
337 mpz_clear (maxt);
338 mpz_clear (minc1);
339 mpz_clear (maxc1);
340 mpz_clear (offc0);
341 mpz_clear (offc1);
342 }
343
344 /* Stores estimate on the minimum/maximum value of the expression VAR + OFF
345 in TYPE to MIN and MAX. */
346
347 static void
determine_value_range(class loop * loop,tree type,tree var,mpz_t off,mpz_t min,mpz_t max)348 determine_value_range (class loop *loop, tree type, tree var, mpz_t off,
349 mpz_t min, mpz_t max)
350 {
351 int cnt = 0;
352 mpz_t minm, maxm;
353 basic_block bb;
354 wide_int minv, maxv;
355 enum value_range_kind rtype = VR_VARYING;
356
357 /* If the expression is a constant, we know its value exactly. */
358 if (integer_zerop (var))
359 {
360 mpz_set (min, off);
361 mpz_set (max, off);
362 return;
363 }
364
365 get_type_static_bounds (type, min, max);
366
367 /* See if we have some range info from VRP. */
368 if (TREE_CODE (var) == SSA_NAME && INTEGRAL_TYPE_P (type))
369 {
370 edge e = loop_preheader_edge (loop);
371 signop sgn = TYPE_SIGN (type);
372 gphi_iterator gsi;
373
374 /* Either for VAR itself... */
375 rtype = get_range_info (var, &minv, &maxv);
376 /* Or for PHI results in loop->header where VAR is used as
377 PHI argument from the loop preheader edge. */
378 for (gsi = gsi_start_phis (loop->header); !gsi_end_p (gsi); gsi_next (&gsi))
379 {
380 gphi *phi = gsi.phi ();
381 wide_int minc, maxc;
382 if (PHI_ARG_DEF_FROM_EDGE (phi, e) == var
383 && (get_range_info (gimple_phi_result (phi), &minc, &maxc)
384 == VR_RANGE))
385 {
386 if (rtype != VR_RANGE)
387 {
388 rtype = VR_RANGE;
389 minv = minc;
390 maxv = maxc;
391 }
392 else
393 {
394 minv = wi::max (minv, minc, sgn);
395 maxv = wi::min (maxv, maxc, sgn);
396 /* If the PHI result range are inconsistent with
397 the VAR range, give up on looking at the PHI
398 results. This can happen if VR_UNDEFINED is
399 involved. */
400 if (wi::gt_p (minv, maxv, sgn))
401 {
402 rtype = get_range_info (var, &minv, &maxv);
403 break;
404 }
405 }
406 }
407 }
408 mpz_init (minm);
409 mpz_init (maxm);
410 if (rtype != VR_RANGE)
411 {
412 mpz_set (minm, min);
413 mpz_set (maxm, max);
414 }
415 else
416 {
417 gcc_assert (wi::le_p (minv, maxv, sgn));
418 wi::to_mpz (minv, minm, sgn);
419 wi::to_mpz (maxv, maxm, sgn);
420 }
421 /* Now walk the dominators of the loop header and use the entry
422 guards to refine the estimates. */
423 for (bb = loop->header;
424 bb != ENTRY_BLOCK_PTR_FOR_FN (cfun) && cnt < MAX_DOMINATORS_TO_WALK;
425 bb = get_immediate_dominator (CDI_DOMINATORS, bb))
426 {
427 edge e;
428 tree c0, c1;
429 gimple *cond;
430 enum tree_code cmp;
431
432 if (!single_pred_p (bb))
433 continue;
434 e = single_pred_edge (bb);
435
436 if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
437 continue;
438
439 cond = last_stmt (e->src);
440 c0 = gimple_cond_lhs (cond);
441 cmp = gimple_cond_code (cond);
442 c1 = gimple_cond_rhs (cond);
443
444 if (e->flags & EDGE_FALSE_VALUE)
445 cmp = invert_tree_comparison (cmp, false);
446
447 refine_value_range_using_guard (type, var, c0, cmp, c1, minm, maxm);
448 ++cnt;
449 }
450
451 mpz_add (minm, minm, off);
452 mpz_add (maxm, maxm, off);
453 /* If the computation may not wrap or off is zero, then this
454 is always fine. If off is negative and minv + off isn't
455 smaller than type's minimum, or off is positive and
456 maxv + off isn't bigger than type's maximum, use the more
457 precise range too. */
458 if (nowrap_type_p (type)
459 || mpz_sgn (off) == 0
460 || (mpz_sgn (off) < 0 && mpz_cmp (minm, min) >= 0)
461 || (mpz_sgn (off) > 0 && mpz_cmp (maxm, max) <= 0))
462 {
463 mpz_set (min, minm);
464 mpz_set (max, maxm);
465 mpz_clear (minm);
466 mpz_clear (maxm);
467 return;
468 }
469 mpz_clear (minm);
470 mpz_clear (maxm);
471 }
472
473 /* If the computation may wrap, we know nothing about the value, except for
474 the range of the type. */
475 if (!nowrap_type_p (type))
476 return;
477
478 /* Since the addition of OFF does not wrap, if OFF is positive, then we may
479 add it to MIN, otherwise to MAX. */
480 if (mpz_sgn (off) < 0)
481 mpz_add (max, max, off);
482 else
483 mpz_add (min, min, off);
484 }
485
486 /* Stores the bounds on the difference of the values of the expressions
487 (var + X) and (var + Y), computed in TYPE, to BNDS. */
488
489 static void
bound_difference_of_offsetted_base(tree type,mpz_t x,mpz_t y,bounds * bnds)490 bound_difference_of_offsetted_base (tree type, mpz_t x, mpz_t y,
491 bounds *bnds)
492 {
493 int rel = mpz_cmp (x, y);
494 bool may_wrap = !nowrap_type_p (type);
495 mpz_t m;
496
497 /* If X == Y, then the expressions are always equal.
498 If X > Y, there are the following possibilities:
499 a) neither of var + X and var + Y overflow or underflow, or both of
500 them do. Then their difference is X - Y.
501 b) var + X overflows, and var + Y does not. Then the values of the
502 expressions are var + X - M and var + Y, where M is the range of
503 the type, and their difference is X - Y - M.
504 c) var + Y underflows and var + X does not. Their difference again
505 is M - X + Y.
506 Therefore, if the arithmetics in type does not overflow, then the
507 bounds are (X - Y, X - Y), otherwise they are (X - Y - M, X - Y)
508 Similarly, if X < Y, the bounds are either (X - Y, X - Y) or
509 (X - Y, X - Y + M). */
510
511 if (rel == 0)
512 {
513 mpz_set_ui (bnds->below, 0);
514 mpz_set_ui (bnds->up, 0);
515 return;
516 }
517
518 mpz_init (m);
519 wi::to_mpz (wi::minus_one (TYPE_PRECISION (type)), m, UNSIGNED);
520 mpz_add_ui (m, m, 1);
521 mpz_sub (bnds->up, x, y);
522 mpz_set (bnds->below, bnds->up);
523
524 if (may_wrap)
525 {
526 if (rel > 0)
527 mpz_sub (bnds->below, bnds->below, m);
528 else
529 mpz_add (bnds->up, bnds->up, m);
530 }
531
532 mpz_clear (m);
533 }
534
535 /* From condition C0 CMP C1 derives information regarding the
536 difference of values of VARX + OFFX and VARY + OFFY, computed in TYPE,
537 and stores it to BNDS. */
538
539 static void
refine_bounds_using_guard(tree type,tree varx,mpz_t offx,tree vary,mpz_t offy,tree c0,enum tree_code cmp,tree c1,bounds * bnds)540 refine_bounds_using_guard (tree type, tree varx, mpz_t offx,
541 tree vary, mpz_t offy,
542 tree c0, enum tree_code cmp, tree c1,
543 bounds *bnds)
544 {
545 tree varc0, varc1, ctype;
546 mpz_t offc0, offc1, loffx, loffy, bnd;
547 bool lbound = false;
548 bool no_wrap = nowrap_type_p (type);
549 bool x_ok, y_ok;
550
551 switch (cmp)
552 {
553 case LT_EXPR:
554 case LE_EXPR:
555 case GT_EXPR:
556 case GE_EXPR:
557 STRIP_SIGN_NOPS (c0);
558 STRIP_SIGN_NOPS (c1);
559 ctype = TREE_TYPE (c0);
560 if (!useless_type_conversion_p (ctype, type))
561 return;
562
563 break;
564
565 case EQ_EXPR:
566 /* We could derive quite precise information from EQ_EXPR, however, such
567 a guard is unlikely to appear, so we do not bother with handling
568 it. */
569 return;
570
571 case NE_EXPR:
572 /* NE_EXPR comparisons do not contain much of useful information, except for
573 special case of comparing with the bounds of the type. */
574 if (TREE_CODE (c1) != INTEGER_CST
575 || !INTEGRAL_TYPE_P (type))
576 return;
577
578 /* Ensure that the condition speaks about an expression in the same type
579 as X and Y. */
580 ctype = TREE_TYPE (c0);
581 if (TYPE_PRECISION (ctype) != TYPE_PRECISION (type))
582 return;
583 c0 = fold_convert (type, c0);
584 c1 = fold_convert (type, c1);
585
586 if (TYPE_MIN_VALUE (type)
587 && operand_equal_p (c1, TYPE_MIN_VALUE (type), 0))
588 {
589 cmp = GT_EXPR;
590 break;
591 }
592 if (TYPE_MAX_VALUE (type)
593 && operand_equal_p (c1, TYPE_MAX_VALUE (type), 0))
594 {
595 cmp = LT_EXPR;
596 break;
597 }
598
599 return;
600 default:
601 return;
602 }
603
604 mpz_init (offc0);
605 mpz_init (offc1);
606 split_to_var_and_offset (expand_simple_operations (c0), &varc0, offc0);
607 split_to_var_and_offset (expand_simple_operations (c1), &varc1, offc1);
608
609 /* We are only interested in comparisons of expressions based on VARX and
610 VARY. TODO -- we might also be able to derive some bounds from
611 expressions containing just one of the variables. */
612
613 if (operand_equal_p (varx, varc1, 0))
614 {
615 std::swap (varc0, varc1);
616 mpz_swap (offc0, offc1);
617 cmp = swap_tree_comparison (cmp);
618 }
619
620 if (!operand_equal_p (varx, varc0, 0)
621 || !operand_equal_p (vary, varc1, 0))
622 goto end;
623
624 mpz_init_set (loffx, offx);
625 mpz_init_set (loffy, offy);
626
627 if (cmp == GT_EXPR || cmp == GE_EXPR)
628 {
629 std::swap (varx, vary);
630 mpz_swap (offc0, offc1);
631 mpz_swap (loffx, loffy);
632 cmp = swap_tree_comparison (cmp);
633 lbound = true;
634 }
635
636 /* If there is no overflow, the condition implies that
637
638 (VARX + OFFX) cmp (VARY + OFFY) + (OFFX - OFFY + OFFC1 - OFFC0).
639
640 The overflows and underflows may complicate things a bit; each
641 overflow decreases the appropriate offset by M, and underflow
642 increases it by M. The above inequality would not necessarily be
643 true if
644
645 -- VARX + OFFX underflows and VARX + OFFC0 does not, or
646 VARX + OFFC0 overflows, but VARX + OFFX does not.
647 This may only happen if OFFX < OFFC0.
648 -- VARY + OFFY overflows and VARY + OFFC1 does not, or
649 VARY + OFFC1 underflows and VARY + OFFY does not.
650 This may only happen if OFFY > OFFC1. */
651
652 if (no_wrap)
653 {
654 x_ok = true;
655 y_ok = true;
656 }
657 else
658 {
659 x_ok = (integer_zerop (varx)
660 || mpz_cmp (loffx, offc0) >= 0);
661 y_ok = (integer_zerop (vary)
662 || mpz_cmp (loffy, offc1) <= 0);
663 }
664
665 if (x_ok && y_ok)
666 {
667 mpz_init (bnd);
668 mpz_sub (bnd, loffx, loffy);
669 mpz_add (bnd, bnd, offc1);
670 mpz_sub (bnd, bnd, offc0);
671
672 if (cmp == LT_EXPR)
673 mpz_sub_ui (bnd, bnd, 1);
674
675 if (lbound)
676 {
677 mpz_neg (bnd, bnd);
678 if (mpz_cmp (bnds->below, bnd) < 0)
679 mpz_set (bnds->below, bnd);
680 }
681 else
682 {
683 if (mpz_cmp (bnd, bnds->up) < 0)
684 mpz_set (bnds->up, bnd);
685 }
686 mpz_clear (bnd);
687 }
688
689 mpz_clear (loffx);
690 mpz_clear (loffy);
691 end:
692 mpz_clear (offc0);
693 mpz_clear (offc1);
694 }
695
696 /* Stores the bounds on the value of the expression X - Y in LOOP to BNDS.
697 The subtraction is considered to be performed in arbitrary precision,
698 without overflows.
699
700 We do not attempt to be too clever regarding the value ranges of X and
701 Y; most of the time, they are just integers or ssa names offsetted by
702 integer. However, we try to use the information contained in the
703 comparisons before the loop (usually created by loop header copying). */
704
705 static void
bound_difference(class loop * loop,tree x,tree y,bounds * bnds)706 bound_difference (class loop *loop, tree x, tree y, bounds *bnds)
707 {
708 tree type = TREE_TYPE (x);
709 tree varx, vary;
710 mpz_t offx, offy;
711 mpz_t minx, maxx, miny, maxy;
712 int cnt = 0;
713 edge e;
714 basic_block bb;
715 tree c0, c1;
716 gimple *cond;
717 enum tree_code cmp;
718
719 /* Get rid of unnecessary casts, but preserve the value of
720 the expressions. */
721 STRIP_SIGN_NOPS (x);
722 STRIP_SIGN_NOPS (y);
723
724 mpz_init (bnds->below);
725 mpz_init (bnds->up);
726 mpz_init (offx);
727 mpz_init (offy);
728 split_to_var_and_offset (x, &varx, offx);
729 split_to_var_and_offset (y, &vary, offy);
730
731 if (!integer_zerop (varx)
732 && operand_equal_p (varx, vary, 0))
733 {
734 /* Special case VARX == VARY -- we just need to compare the
735 offsets. The matters are a bit more complicated in the
736 case addition of offsets may wrap. */
737 bound_difference_of_offsetted_base (type, offx, offy, bnds);
738 }
739 else
740 {
741 /* Otherwise, use the value ranges to determine the initial
742 estimates on below and up. */
743 mpz_init (minx);
744 mpz_init (maxx);
745 mpz_init (miny);
746 mpz_init (maxy);
747 determine_value_range (loop, type, varx, offx, minx, maxx);
748 determine_value_range (loop, type, vary, offy, miny, maxy);
749
750 mpz_sub (bnds->below, minx, maxy);
751 mpz_sub (bnds->up, maxx, miny);
752 mpz_clear (minx);
753 mpz_clear (maxx);
754 mpz_clear (miny);
755 mpz_clear (maxy);
756 }
757
758 /* If both X and Y are constants, we cannot get any more precise. */
759 if (integer_zerop (varx) && integer_zerop (vary))
760 goto end;
761
762 /* Now walk the dominators of the loop header and use the entry
763 guards to refine the estimates. */
764 for (bb = loop->header;
765 bb != ENTRY_BLOCK_PTR_FOR_FN (cfun) && cnt < MAX_DOMINATORS_TO_WALK;
766 bb = get_immediate_dominator (CDI_DOMINATORS, bb))
767 {
768 if (!single_pred_p (bb))
769 continue;
770 e = single_pred_edge (bb);
771
772 if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
773 continue;
774
775 cond = last_stmt (e->src);
776 c0 = gimple_cond_lhs (cond);
777 cmp = gimple_cond_code (cond);
778 c1 = gimple_cond_rhs (cond);
779
780 if (e->flags & EDGE_FALSE_VALUE)
781 cmp = invert_tree_comparison (cmp, false);
782
783 refine_bounds_using_guard (type, varx, offx, vary, offy,
784 c0, cmp, c1, bnds);
785 ++cnt;
786 }
787
788 end:
789 mpz_clear (offx);
790 mpz_clear (offy);
791 }
792
793 /* Update the bounds in BNDS that restrict the value of X to the bounds
794 that restrict the value of X + DELTA. X can be obtained as a
795 difference of two values in TYPE. */
796
797 static void
bounds_add(bounds * bnds,const widest_int & delta,tree type)798 bounds_add (bounds *bnds, const widest_int &delta, tree type)
799 {
800 mpz_t mdelta, max;
801
802 mpz_init (mdelta);
803 wi::to_mpz (delta, mdelta, SIGNED);
804
805 mpz_init (max);
806 wi::to_mpz (wi::minus_one (TYPE_PRECISION (type)), max, UNSIGNED);
807
808 mpz_add (bnds->up, bnds->up, mdelta);
809 mpz_add (bnds->below, bnds->below, mdelta);
810
811 if (mpz_cmp (bnds->up, max) > 0)
812 mpz_set (bnds->up, max);
813
814 mpz_neg (max, max);
815 if (mpz_cmp (bnds->below, max) < 0)
816 mpz_set (bnds->below, max);
817
818 mpz_clear (mdelta);
819 mpz_clear (max);
820 }
821
822 /* Update the bounds in BNDS that restrict the value of X to the bounds
823 that restrict the value of -X. */
824
825 static void
bounds_negate(bounds * bnds)826 bounds_negate (bounds *bnds)
827 {
828 mpz_t tmp;
829
830 mpz_init_set (tmp, bnds->up);
831 mpz_neg (bnds->up, bnds->below);
832 mpz_neg (bnds->below, tmp);
833 mpz_clear (tmp);
834 }
835
836 /* Returns inverse of X modulo 2^s, where MASK = 2^s-1. */
837
838 static tree
inverse(tree x,tree mask)839 inverse (tree x, tree mask)
840 {
841 tree type = TREE_TYPE (x);
842 tree rslt;
843 unsigned ctr = tree_floor_log2 (mask);
844
845 if (TYPE_PRECISION (type) <= HOST_BITS_PER_WIDE_INT)
846 {
847 unsigned HOST_WIDE_INT ix;
848 unsigned HOST_WIDE_INT imask;
849 unsigned HOST_WIDE_INT irslt = 1;
850
851 gcc_assert (cst_and_fits_in_hwi (x));
852 gcc_assert (cst_and_fits_in_hwi (mask));
853
854 ix = int_cst_value (x);
855 imask = int_cst_value (mask);
856
857 for (; ctr; ctr--)
858 {
859 irslt *= ix;
860 ix *= ix;
861 }
862 irslt &= imask;
863
864 rslt = build_int_cst_type (type, irslt);
865 }
866 else
867 {
868 rslt = build_int_cst (type, 1);
869 for (; ctr; ctr--)
870 {
871 rslt = int_const_binop (MULT_EXPR, rslt, x);
872 x = int_const_binop (MULT_EXPR, x, x);
873 }
874 rslt = int_const_binop (BIT_AND_EXPR, rslt, mask);
875 }
876
877 return rslt;
878 }
879
880 /* Derives the upper bound BND on the number of executions of loop with exit
881 condition S * i <> C. If NO_OVERFLOW is true, then the control variable of
882 the loop does not overflow. EXIT_MUST_BE_TAKEN is true if we are guaranteed
883 that the loop ends through this exit, i.e., the induction variable ever
884 reaches the value of C.
885
886 The value C is equal to final - base, where final and base are the final and
887 initial value of the actual induction variable in the analysed loop. BNDS
888 bounds the value of this difference when computed in signed type with
889 unbounded range, while the computation of C is performed in an unsigned
890 type with the range matching the range of the type of the induction variable.
891 In particular, BNDS.up contains an upper bound on C in the following cases:
892 -- if the iv must reach its final value without overflow, i.e., if
893 NO_OVERFLOW && EXIT_MUST_BE_TAKEN is true, or
894 -- if final >= base, which we know to hold when BNDS.below >= 0. */
895
896 static void
number_of_iterations_ne_max(mpz_t bnd,bool no_overflow,tree c,tree s,bounds * bnds,bool exit_must_be_taken)897 number_of_iterations_ne_max (mpz_t bnd, bool no_overflow, tree c, tree s,
898 bounds *bnds, bool exit_must_be_taken)
899 {
900 widest_int max;
901 mpz_t d;
902 tree type = TREE_TYPE (c);
903 bool bnds_u_valid = ((no_overflow && exit_must_be_taken)
904 || mpz_sgn (bnds->below) >= 0);
905
906 if (integer_onep (s)
907 || (TREE_CODE (c) == INTEGER_CST
908 && TREE_CODE (s) == INTEGER_CST
909 && wi::mod_trunc (wi::to_wide (c), wi::to_wide (s),
910 TYPE_SIGN (type)) == 0)
911 || (TYPE_OVERFLOW_UNDEFINED (type)
912 && multiple_of_p (type, c, s)))
913 {
914 /* If C is an exact multiple of S, then its value will be reached before
915 the induction variable overflows (unless the loop is exited in some
916 other way before). Note that the actual induction variable in the
917 loop (which ranges from base to final instead of from 0 to C) may
918 overflow, in which case BNDS.up will not be giving a correct upper
919 bound on C; thus, BNDS_U_VALID had to be computed in advance. */
920 no_overflow = true;
921 exit_must_be_taken = true;
922 }
923
924 /* If the induction variable can overflow, the number of iterations is at
925 most the period of the control variable (or infinite, but in that case
926 the whole # of iterations analysis will fail). */
927 if (!no_overflow)
928 {
929 max = wi::mask <widest_int> (TYPE_PRECISION (type)
930 - wi::ctz (wi::to_wide (s)), false);
931 wi::to_mpz (max, bnd, UNSIGNED);
932 return;
933 }
934
935 /* Now we know that the induction variable does not overflow, so the loop
936 iterates at most (range of type / S) times. */
937 wi::to_mpz (wi::minus_one (TYPE_PRECISION (type)), bnd, UNSIGNED);
938
939 /* If the induction variable is guaranteed to reach the value of C before
940 overflow, ... */
941 if (exit_must_be_taken)
942 {
943 /* ... then we can strengthen this to C / S, and possibly we can use
944 the upper bound on C given by BNDS. */
945 if (TREE_CODE (c) == INTEGER_CST)
946 wi::to_mpz (wi::to_wide (c), bnd, UNSIGNED);
947 else if (bnds_u_valid)
948 mpz_set (bnd, bnds->up);
949 }
950
951 mpz_init (d);
952 wi::to_mpz (wi::to_wide (s), d, UNSIGNED);
953 mpz_fdiv_q (bnd, bnd, d);
954 mpz_clear (d);
955 }
956
957 /* Determines number of iterations of loop whose ending condition
958 is IV <> FINAL. TYPE is the type of the iv. The number of
959 iterations is stored to NITER. EXIT_MUST_BE_TAKEN is true if
960 we know that the exit must be taken eventually, i.e., that the IV
961 ever reaches the value FINAL (we derived this earlier, and possibly set
962 NITER->assumptions to make sure this is the case). BNDS contains the
963 bounds on the difference FINAL - IV->base. */
964
965 static bool
number_of_iterations_ne(class loop * loop,tree type,affine_iv * iv,tree final,class tree_niter_desc * niter,bool exit_must_be_taken,bounds * bnds)966 number_of_iterations_ne (class loop *loop, tree type, affine_iv *iv,
967 tree final, class tree_niter_desc *niter,
968 bool exit_must_be_taken, bounds *bnds)
969 {
970 tree niter_type = unsigned_type_for (type);
971 tree s, c, d, bits, assumption, tmp, bound;
972 mpz_t max;
973
974 niter->control = *iv;
975 niter->bound = final;
976 niter->cmp = NE_EXPR;
977
978 /* Rearrange the terms so that we get inequality S * i <> C, with S
979 positive. Also cast everything to the unsigned type. If IV does
980 not overflow, BNDS bounds the value of C. Also, this is the
981 case if the computation |FINAL - IV->base| does not overflow, i.e.,
982 if BNDS->below in the result is nonnegative. */
983 if (tree_int_cst_sign_bit (iv->step))
984 {
985 s = fold_convert (niter_type,
986 fold_build1 (NEGATE_EXPR, type, iv->step));
987 c = fold_build2 (MINUS_EXPR, niter_type,
988 fold_convert (niter_type, iv->base),
989 fold_convert (niter_type, final));
990 bounds_negate (bnds);
991 }
992 else
993 {
994 s = fold_convert (niter_type, iv->step);
995 c = fold_build2 (MINUS_EXPR, niter_type,
996 fold_convert (niter_type, final),
997 fold_convert (niter_type, iv->base));
998 }
999
1000 mpz_init (max);
1001 number_of_iterations_ne_max (max, iv->no_overflow, c, s, bnds,
1002 exit_must_be_taken);
1003 niter->max = widest_int::from (wi::from_mpz (niter_type, max, false),
1004 TYPE_SIGN (niter_type));
1005 mpz_clear (max);
1006
1007 /* Compute no-overflow information for the control iv. This can be
1008 proven when below two conditions are satisfied:
1009
1010 1) IV evaluates toward FINAL at beginning, i.e:
1011 base <= FINAL ; step > 0
1012 base >= FINAL ; step < 0
1013
1014 2) |FINAL - base| is an exact multiple of step.
1015
1016 Unfortunately, it's hard to prove above conditions after pass loop-ch
1017 because loop with exit condition (IV != FINAL) usually will be guarded
1018 by initial-condition (IV.base - IV.step != FINAL). In this case, we
1019 can alternatively try to prove below conditions:
1020
1021 1') IV evaluates toward FINAL at beginning, i.e:
1022 new_base = base - step < FINAL ; step > 0
1023 && base - step doesn't underflow
1024 new_base = base - step > FINAL ; step < 0
1025 && base - step doesn't overflow
1026
1027 2') |FINAL - new_base| is an exact multiple of step.
1028
1029 Please refer to PR34114 as an example of loop-ch's impact, also refer
1030 to PR72817 as an example why condition 2') is necessary.
1031
1032 Note, for NE_EXPR, base equals to FINAL is a special case, in
1033 which the loop exits immediately, and the iv does not overflow. */
1034 if (!niter->control.no_overflow
1035 && (integer_onep (s) || multiple_of_p (type, c, s)))
1036 {
1037 tree t, cond, new_c, relaxed_cond = boolean_false_node;
1038
1039 if (tree_int_cst_sign_bit (iv->step))
1040 {
1041 cond = fold_build2 (GE_EXPR, boolean_type_node, iv->base, final);
1042 if (TREE_CODE (type) == INTEGER_TYPE)
1043 {
1044 /* Only when base - step doesn't overflow. */
1045 t = TYPE_MAX_VALUE (type);
1046 t = fold_build2 (PLUS_EXPR, type, t, iv->step);
1047 t = fold_build2 (GE_EXPR, boolean_type_node, t, iv->base);
1048 if (integer_nonzerop (t))
1049 {
1050 t = fold_build2 (MINUS_EXPR, type, iv->base, iv->step);
1051 new_c = fold_build2 (MINUS_EXPR, niter_type,
1052 fold_convert (niter_type, t),
1053 fold_convert (niter_type, final));
1054 if (multiple_of_p (type, new_c, s))
1055 relaxed_cond = fold_build2 (GT_EXPR, boolean_type_node,
1056 t, final);
1057 }
1058 }
1059 }
1060 else
1061 {
1062 cond = fold_build2 (LE_EXPR, boolean_type_node, iv->base, final);
1063 if (TREE_CODE (type) == INTEGER_TYPE)
1064 {
1065 /* Only when base - step doesn't underflow. */
1066 t = TYPE_MIN_VALUE (type);
1067 t = fold_build2 (PLUS_EXPR, type, t, iv->step);
1068 t = fold_build2 (LE_EXPR, boolean_type_node, t, iv->base);
1069 if (integer_nonzerop (t))
1070 {
1071 t = fold_build2 (MINUS_EXPR, type, iv->base, iv->step);
1072 new_c = fold_build2 (MINUS_EXPR, niter_type,
1073 fold_convert (niter_type, final),
1074 fold_convert (niter_type, t));
1075 if (multiple_of_p (type, new_c, s))
1076 relaxed_cond = fold_build2 (LT_EXPR, boolean_type_node,
1077 t, final);
1078 }
1079 }
1080 }
1081
1082 t = simplify_using_initial_conditions (loop, cond);
1083 if (!t || !integer_onep (t))
1084 t = simplify_using_initial_conditions (loop, relaxed_cond);
1085
1086 if (t && integer_onep (t))
1087 niter->control.no_overflow = true;
1088 }
1089
1090 /* First the trivial cases -- when the step is 1. */
1091 if (integer_onep (s))
1092 {
1093 niter->niter = c;
1094 return true;
1095 }
1096 if (niter->control.no_overflow && multiple_of_p (type, c, s))
1097 {
1098 niter->niter = fold_build2 (FLOOR_DIV_EXPR, niter_type, c, s);
1099 return true;
1100 }
1101
1102 /* Let nsd (step, size of mode) = d. If d does not divide c, the loop
1103 is infinite. Otherwise, the number of iterations is
1104 (inverse(s/d) * (c/d)) mod (size of mode/d). */
1105 bits = num_ending_zeros (s);
1106 bound = build_low_bits_mask (niter_type,
1107 (TYPE_PRECISION (niter_type)
1108 - tree_to_uhwi (bits)));
1109
1110 d = fold_binary_to_constant (LSHIFT_EXPR, niter_type,
1111 build_int_cst (niter_type, 1), bits);
1112 s = fold_binary_to_constant (RSHIFT_EXPR, niter_type, s, bits);
1113
1114 if (!exit_must_be_taken)
1115 {
1116 /* If we cannot assume that the exit is taken eventually, record the
1117 assumptions for divisibility of c. */
1118 assumption = fold_build2 (FLOOR_MOD_EXPR, niter_type, c, d);
1119 assumption = fold_build2 (EQ_EXPR, boolean_type_node,
1120 assumption, build_int_cst (niter_type, 0));
1121 if (!integer_nonzerop (assumption))
1122 niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
1123 niter->assumptions, assumption);
1124 }
1125
1126 c = fold_build2 (EXACT_DIV_EXPR, niter_type, c, d);
1127 if (integer_onep (s))
1128 {
1129 niter->niter = c;
1130 }
1131 else
1132 {
1133 tmp = fold_build2 (MULT_EXPR, niter_type, c, inverse (s, bound));
1134 niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
1135 }
1136 return true;
1137 }
1138
1139 /* Checks whether we can determine the final value of the control variable
1140 of the loop with ending condition IV0 < IV1 (computed in TYPE).
1141 DELTA is the difference IV1->base - IV0->base, STEP is the absolute value
1142 of the step. The assumptions necessary to ensure that the computation
1143 of the final value does not overflow are recorded in NITER. If we
1144 find the final value, we adjust DELTA and return TRUE. Otherwise
1145 we return false. BNDS bounds the value of IV1->base - IV0->base,
1146 and will be updated by the same amount as DELTA. EXIT_MUST_BE_TAKEN is
1147 true if we know that the exit must be taken eventually. */
1148
1149 static bool
number_of_iterations_lt_to_ne(tree type,affine_iv * iv0,affine_iv * iv1,class tree_niter_desc * niter,tree * delta,tree step,bool exit_must_be_taken,bounds * bnds)1150 number_of_iterations_lt_to_ne (tree type, affine_iv *iv0, affine_iv *iv1,
1151 class tree_niter_desc *niter,
1152 tree *delta, tree step,
1153 bool exit_must_be_taken, bounds *bnds)
1154 {
1155 tree niter_type = TREE_TYPE (step);
1156 tree mod = fold_build2 (FLOOR_MOD_EXPR, niter_type, *delta, step);
1157 tree tmod;
1158 mpz_t mmod;
1159 tree assumption = boolean_true_node, bound, noloop;
1160 bool ret = false, fv_comp_no_overflow;
1161 tree type1 = type;
1162 if (POINTER_TYPE_P (type))
1163 type1 = sizetype;
1164
1165 if (TREE_CODE (mod) != INTEGER_CST)
1166 return false;
1167 if (integer_nonzerop (mod))
1168 mod = fold_build2 (MINUS_EXPR, niter_type, step, mod);
1169 tmod = fold_convert (type1, mod);
1170
1171 mpz_init (mmod);
1172 wi::to_mpz (wi::to_wide (mod), mmod, UNSIGNED);
1173 mpz_neg (mmod, mmod);
1174
1175 /* If the induction variable does not overflow and the exit is taken,
1176 then the computation of the final value does not overflow. This is
1177 also obviously the case if the new final value is equal to the
1178 current one. Finally, we postulate this for pointer type variables,
1179 as the code cannot rely on the object to that the pointer points being
1180 placed at the end of the address space (and more pragmatically,
1181 TYPE_{MIN,MAX}_VALUE is not defined for pointers). */
1182 if (integer_zerop (mod) || POINTER_TYPE_P (type))
1183 fv_comp_no_overflow = true;
1184 else if (!exit_must_be_taken)
1185 fv_comp_no_overflow = false;
1186 else
1187 fv_comp_no_overflow =
1188 (iv0->no_overflow && integer_nonzerop (iv0->step))
1189 || (iv1->no_overflow && integer_nonzerop (iv1->step));
1190
1191 if (integer_nonzerop (iv0->step))
1192 {
1193 /* The final value of the iv is iv1->base + MOD, assuming that this
1194 computation does not overflow, and that
1195 iv0->base <= iv1->base + MOD. */
1196 if (!fv_comp_no_overflow)
1197 {
1198 bound = fold_build2 (MINUS_EXPR, type1,
1199 TYPE_MAX_VALUE (type1), tmod);
1200 assumption = fold_build2 (LE_EXPR, boolean_type_node,
1201 iv1->base, bound);
1202 if (integer_zerop (assumption))
1203 goto end;
1204 }
1205 if (mpz_cmp (mmod, bnds->below) < 0)
1206 noloop = boolean_false_node;
1207 else if (POINTER_TYPE_P (type))
1208 noloop = fold_build2 (GT_EXPR, boolean_type_node,
1209 iv0->base,
1210 fold_build_pointer_plus (iv1->base, tmod));
1211 else
1212 noloop = fold_build2 (GT_EXPR, boolean_type_node,
1213 iv0->base,
1214 fold_build2 (PLUS_EXPR, type1,
1215 iv1->base, tmod));
1216 }
1217 else
1218 {
1219 /* The final value of the iv is iv0->base - MOD, assuming that this
1220 computation does not overflow, and that
1221 iv0->base - MOD <= iv1->base. */
1222 if (!fv_comp_no_overflow)
1223 {
1224 bound = fold_build2 (PLUS_EXPR, type1,
1225 TYPE_MIN_VALUE (type1), tmod);
1226 assumption = fold_build2 (GE_EXPR, boolean_type_node,
1227 iv0->base, bound);
1228 if (integer_zerop (assumption))
1229 goto end;
1230 }
1231 if (mpz_cmp (mmod, bnds->below) < 0)
1232 noloop = boolean_false_node;
1233 else if (POINTER_TYPE_P (type))
1234 noloop = fold_build2 (GT_EXPR, boolean_type_node,
1235 fold_build_pointer_plus (iv0->base,
1236 fold_build1 (NEGATE_EXPR,
1237 type1, tmod)),
1238 iv1->base);
1239 else
1240 noloop = fold_build2 (GT_EXPR, boolean_type_node,
1241 fold_build2 (MINUS_EXPR, type1,
1242 iv0->base, tmod),
1243 iv1->base);
1244 }
1245
1246 if (!integer_nonzerop (assumption))
1247 niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
1248 niter->assumptions,
1249 assumption);
1250 if (!integer_zerop (noloop))
1251 niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
1252 niter->may_be_zero,
1253 noloop);
1254 bounds_add (bnds, wi::to_widest (mod), type);
1255 *delta = fold_build2 (PLUS_EXPR, niter_type, *delta, mod);
1256
1257 ret = true;
1258 end:
1259 mpz_clear (mmod);
1260 return ret;
1261 }
1262
1263 /* Add assertions to NITER that ensure that the control variable of the loop
1264 with ending condition IV0 < IV1 does not overflow. Types of IV0 and IV1
1265 are TYPE. Returns false if we can prove that there is an overflow, true
1266 otherwise. STEP is the absolute value of the step. */
1267
1268 static bool
assert_no_overflow_lt(tree type,affine_iv * iv0,affine_iv * iv1,class tree_niter_desc * niter,tree step)1269 assert_no_overflow_lt (tree type, affine_iv *iv0, affine_iv *iv1,
1270 class tree_niter_desc *niter, tree step)
1271 {
1272 tree bound, d, assumption, diff;
1273 tree niter_type = TREE_TYPE (step);
1274
1275 if (integer_nonzerop (iv0->step))
1276 {
1277 /* for (i = iv0->base; i < iv1->base; i += iv0->step) */
1278 if (iv0->no_overflow)
1279 return true;
1280
1281 /* If iv0->base is a constant, we can determine the last value before
1282 overflow precisely; otherwise we conservatively assume
1283 MAX - STEP + 1. */
1284
1285 if (TREE_CODE (iv0->base) == INTEGER_CST)
1286 {
1287 d = fold_build2 (MINUS_EXPR, niter_type,
1288 fold_convert (niter_type, TYPE_MAX_VALUE (type)),
1289 fold_convert (niter_type, iv0->base));
1290 diff = fold_build2 (FLOOR_MOD_EXPR, niter_type, d, step);
1291 }
1292 else
1293 diff = fold_build2 (MINUS_EXPR, niter_type, step,
1294 build_int_cst (niter_type, 1));
1295 bound = fold_build2 (MINUS_EXPR, type,
1296 TYPE_MAX_VALUE (type), fold_convert (type, diff));
1297 assumption = fold_build2 (LE_EXPR, boolean_type_node,
1298 iv1->base, bound);
1299 }
1300 else
1301 {
1302 /* for (i = iv1->base; i > iv0->base; i += iv1->step) */
1303 if (iv1->no_overflow)
1304 return true;
1305
1306 if (TREE_CODE (iv1->base) == INTEGER_CST)
1307 {
1308 d = fold_build2 (MINUS_EXPR, niter_type,
1309 fold_convert (niter_type, iv1->base),
1310 fold_convert (niter_type, TYPE_MIN_VALUE (type)));
1311 diff = fold_build2 (FLOOR_MOD_EXPR, niter_type, d, step);
1312 }
1313 else
1314 diff = fold_build2 (MINUS_EXPR, niter_type, step,
1315 build_int_cst (niter_type, 1));
1316 bound = fold_build2 (PLUS_EXPR, type,
1317 TYPE_MIN_VALUE (type), fold_convert (type, diff));
1318 assumption = fold_build2 (GE_EXPR, boolean_type_node,
1319 iv0->base, bound);
1320 }
1321
1322 if (integer_zerop (assumption))
1323 return false;
1324 if (!integer_nonzerop (assumption))
1325 niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
1326 niter->assumptions, assumption);
1327
1328 iv0->no_overflow = true;
1329 iv1->no_overflow = true;
1330 return true;
1331 }
1332
1333 /* Add an assumption to NITER that a loop whose ending condition
1334 is IV0 < IV1 rolls. TYPE is the type of the control iv. BNDS
1335 bounds the value of IV1->base - IV0->base. */
1336
1337 static void
assert_loop_rolls_lt(tree type,affine_iv * iv0,affine_iv * iv1,class tree_niter_desc * niter,bounds * bnds)1338 assert_loop_rolls_lt (tree type, affine_iv *iv0, affine_iv *iv1,
1339 class tree_niter_desc *niter, bounds *bnds)
1340 {
1341 tree assumption = boolean_true_node, bound, diff;
1342 tree mbz, mbzl, mbzr, type1;
1343 bool rolls_p, no_overflow_p;
1344 widest_int dstep;
1345 mpz_t mstep, max;
1346
1347 /* We are going to compute the number of iterations as
1348 (iv1->base - iv0->base + step - 1) / step, computed in the unsigned
1349 variant of TYPE. This formula only works if
1350
1351 -step + 1 <= (iv1->base - iv0->base) <= MAX - step + 1
1352
1353 (where MAX is the maximum value of the unsigned variant of TYPE, and
1354 the computations in this formula are performed in full precision,
1355 i.e., without overflows).
1356
1357 Usually, for loops with exit condition iv0->base + step * i < iv1->base,
1358 we have a condition of the form iv0->base - step < iv1->base before the loop,
1359 and for loops iv0->base < iv1->base - step * i the condition
1360 iv0->base < iv1->base + step, due to loop header copying, which enable us
1361 to prove the lower bound.
1362
1363 The upper bound is more complicated. Unless the expressions for initial
1364 and final value themselves contain enough information, we usually cannot
1365 derive it from the context. */
1366
1367 /* First check whether the answer does not follow from the bounds we gathered
1368 before. */
1369 if (integer_nonzerop (iv0->step))
1370 dstep = wi::to_widest (iv0->step);
1371 else
1372 {
1373 dstep = wi::sext (wi::to_widest (iv1->step), TYPE_PRECISION (type));
1374 dstep = -dstep;
1375 }
1376
1377 mpz_init (mstep);
1378 wi::to_mpz (dstep, mstep, UNSIGNED);
1379 mpz_neg (mstep, mstep);
1380 mpz_add_ui (mstep, mstep, 1);
1381
1382 rolls_p = mpz_cmp (mstep, bnds->below) <= 0;
1383
1384 mpz_init (max);
1385 wi::to_mpz (wi::minus_one (TYPE_PRECISION (type)), max, UNSIGNED);
1386 mpz_add (max, max, mstep);
1387 no_overflow_p = (mpz_cmp (bnds->up, max) <= 0
1388 /* For pointers, only values lying inside a single object
1389 can be compared or manipulated by pointer arithmetics.
1390 Gcc in general does not allow or handle objects larger
1391 than half of the address space, hence the upper bound
1392 is satisfied for pointers. */
1393 || POINTER_TYPE_P (type));
1394 mpz_clear (mstep);
1395 mpz_clear (max);
1396
1397 if (rolls_p && no_overflow_p)
1398 return;
1399
1400 type1 = type;
1401 if (POINTER_TYPE_P (type))
1402 type1 = sizetype;
1403
1404 /* Now the hard part; we must formulate the assumption(s) as expressions, and
1405 we must be careful not to introduce overflow. */
1406
1407 if (integer_nonzerop (iv0->step))
1408 {
1409 diff = fold_build2 (MINUS_EXPR, type1,
1410 iv0->step, build_int_cst (type1, 1));
1411
1412 /* We need to know that iv0->base >= MIN + iv0->step - 1. Since
1413 0 address never belongs to any object, we can assume this for
1414 pointers. */
1415 if (!POINTER_TYPE_P (type))
1416 {
1417 bound = fold_build2 (PLUS_EXPR, type1,
1418 TYPE_MIN_VALUE (type), diff);
1419 assumption = fold_build2 (GE_EXPR, boolean_type_node,
1420 iv0->base, bound);
1421 }
1422
1423 /* And then we can compute iv0->base - diff, and compare it with
1424 iv1->base. */
1425 mbzl = fold_build2 (MINUS_EXPR, type1,
1426 fold_convert (type1, iv0->base), diff);
1427 mbzr = fold_convert (type1, iv1->base);
1428 }
1429 else
1430 {
1431 diff = fold_build2 (PLUS_EXPR, type1,
1432 iv1->step, build_int_cst (type1, 1));
1433
1434 if (!POINTER_TYPE_P (type))
1435 {
1436 bound = fold_build2 (PLUS_EXPR, type1,
1437 TYPE_MAX_VALUE (type), diff);
1438 assumption = fold_build2 (LE_EXPR, boolean_type_node,
1439 iv1->base, bound);
1440 }
1441
1442 mbzl = fold_convert (type1, iv0->base);
1443 mbzr = fold_build2 (MINUS_EXPR, type1,
1444 fold_convert (type1, iv1->base), diff);
1445 }
1446
1447 if (!integer_nonzerop (assumption))
1448 niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
1449 niter->assumptions, assumption);
1450 if (!rolls_p)
1451 {
1452 mbz = fold_build2 (GT_EXPR, boolean_type_node, mbzl, mbzr);
1453 niter->may_be_zero = fold_build2 (TRUTH_OR_EXPR, boolean_type_node,
1454 niter->may_be_zero, mbz);
1455 }
1456 }
1457
1458 /* Determines number of iterations of loop whose ending condition
1459 is IV0 < IV1. TYPE is the type of the iv. The number of
1460 iterations is stored to NITER. BNDS bounds the difference
1461 IV1->base - IV0->base. EXIT_MUST_BE_TAKEN is true if we know
1462 that the exit must be taken eventually. */
1463
1464 static bool
number_of_iterations_lt(class loop * loop,tree type,affine_iv * iv0,affine_iv * iv1,class tree_niter_desc * niter,bool exit_must_be_taken,bounds * bnds)1465 number_of_iterations_lt (class loop *loop, tree type, affine_iv *iv0,
1466 affine_iv *iv1, class tree_niter_desc *niter,
1467 bool exit_must_be_taken, bounds *bnds)
1468 {
1469 tree niter_type = unsigned_type_for (type);
1470 tree delta, step, s;
1471 mpz_t mstep, tmp;
1472
1473 if (integer_nonzerop (iv0->step))
1474 {
1475 niter->control = *iv0;
1476 niter->cmp = LT_EXPR;
1477 niter->bound = iv1->base;
1478 }
1479 else
1480 {
1481 niter->control = *iv1;
1482 niter->cmp = GT_EXPR;
1483 niter->bound = iv0->base;
1484 }
1485
1486 delta = fold_build2 (MINUS_EXPR, niter_type,
1487 fold_convert (niter_type, iv1->base),
1488 fold_convert (niter_type, iv0->base));
1489
1490 /* First handle the special case that the step is +-1. */
1491 if ((integer_onep (iv0->step) && integer_zerop (iv1->step))
1492 || (integer_all_onesp (iv1->step) && integer_zerop (iv0->step)))
1493 {
1494 /* for (i = iv0->base; i < iv1->base; i++)
1495
1496 or
1497
1498 for (i = iv1->base; i > iv0->base; i--).
1499
1500 In both cases # of iterations is iv1->base - iv0->base, assuming that
1501 iv1->base >= iv0->base.
1502
1503 First try to derive a lower bound on the value of
1504 iv1->base - iv0->base, computed in full precision. If the difference
1505 is nonnegative, we are done, otherwise we must record the
1506 condition. */
1507
1508 if (mpz_sgn (bnds->below) < 0)
1509 niter->may_be_zero = fold_build2 (LT_EXPR, boolean_type_node,
1510 iv1->base, iv0->base);
1511 niter->niter = delta;
1512 niter->max = widest_int::from (wi::from_mpz (niter_type, bnds->up, false),
1513 TYPE_SIGN (niter_type));
1514 niter->control.no_overflow = true;
1515 return true;
1516 }
1517
1518 if (integer_nonzerop (iv0->step))
1519 step = fold_convert (niter_type, iv0->step);
1520 else
1521 step = fold_convert (niter_type,
1522 fold_build1 (NEGATE_EXPR, type, iv1->step));
1523
1524 /* If we can determine the final value of the control iv exactly, we can
1525 transform the condition to != comparison. In particular, this will be
1526 the case if DELTA is constant. */
1527 if (number_of_iterations_lt_to_ne (type, iv0, iv1, niter, &delta, step,
1528 exit_must_be_taken, bnds))
1529 {
1530 affine_iv zps;
1531
1532 zps.base = build_int_cst (niter_type, 0);
1533 zps.step = step;
1534 /* number_of_iterations_lt_to_ne will add assumptions that ensure that
1535 zps does not overflow. */
1536 zps.no_overflow = true;
1537
1538 return number_of_iterations_ne (loop, type, &zps,
1539 delta, niter, true, bnds);
1540 }
1541
1542 /* Make sure that the control iv does not overflow. */
1543 if (!assert_no_overflow_lt (type, iv0, iv1, niter, step))
1544 return false;
1545
1546 /* We determine the number of iterations as (delta + step - 1) / step. For
1547 this to work, we must know that iv1->base >= iv0->base - step + 1,
1548 otherwise the loop does not roll. */
1549 assert_loop_rolls_lt (type, iv0, iv1, niter, bnds);
1550
1551 s = fold_build2 (MINUS_EXPR, niter_type,
1552 step, build_int_cst (niter_type, 1));
1553 delta = fold_build2 (PLUS_EXPR, niter_type, delta, s);
1554 niter->niter = fold_build2 (FLOOR_DIV_EXPR, niter_type, delta, step);
1555
1556 mpz_init (mstep);
1557 mpz_init (tmp);
1558 wi::to_mpz (wi::to_wide (step), mstep, UNSIGNED);
1559 mpz_add (tmp, bnds->up, mstep);
1560 mpz_sub_ui (tmp, tmp, 1);
1561 mpz_fdiv_q (tmp, tmp, mstep);
1562 niter->max = widest_int::from (wi::from_mpz (niter_type, tmp, false),
1563 TYPE_SIGN (niter_type));
1564 mpz_clear (mstep);
1565 mpz_clear (tmp);
1566
1567 return true;
1568 }
1569
1570 /* Determines number of iterations of loop whose ending condition
1571 is IV0 <= IV1. TYPE is the type of the iv. The number of
1572 iterations is stored to NITER. EXIT_MUST_BE_TAKEN is true if
1573 we know that this condition must eventually become false (we derived this
1574 earlier, and possibly set NITER->assumptions to make sure this
1575 is the case). BNDS bounds the difference IV1->base - IV0->base. */
1576
1577 static bool
number_of_iterations_le(class loop * loop,tree type,affine_iv * iv0,affine_iv * iv1,class tree_niter_desc * niter,bool exit_must_be_taken,bounds * bnds)1578 number_of_iterations_le (class loop *loop, tree type, affine_iv *iv0,
1579 affine_iv *iv1, class tree_niter_desc *niter,
1580 bool exit_must_be_taken, bounds *bnds)
1581 {
1582 tree assumption;
1583 tree type1 = type;
1584 if (POINTER_TYPE_P (type))
1585 type1 = sizetype;
1586
1587 /* Say that IV0 is the control variable. Then IV0 <= IV1 iff
1588 IV0 < IV1 + 1, assuming that IV1 is not equal to the greatest
1589 value of the type. This we must know anyway, since if it is
1590 equal to this value, the loop rolls forever. We do not check
1591 this condition for pointer type ivs, as the code cannot rely on
1592 the object to that the pointer points being placed at the end of
1593 the address space (and more pragmatically, TYPE_{MIN,MAX}_VALUE is
1594 not defined for pointers). */
1595
1596 if (!exit_must_be_taken && !POINTER_TYPE_P (type))
1597 {
1598 if (integer_nonzerop (iv0->step))
1599 assumption = fold_build2 (NE_EXPR, boolean_type_node,
1600 iv1->base, TYPE_MAX_VALUE (type));
1601 else
1602 assumption = fold_build2 (NE_EXPR, boolean_type_node,
1603 iv0->base, TYPE_MIN_VALUE (type));
1604
1605 if (integer_zerop (assumption))
1606 return false;
1607 if (!integer_nonzerop (assumption))
1608 niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
1609 niter->assumptions, assumption);
1610 }
1611
1612 if (integer_nonzerop (iv0->step))
1613 {
1614 if (POINTER_TYPE_P (type))
1615 iv1->base = fold_build_pointer_plus_hwi (iv1->base, 1);
1616 else
1617 iv1->base = fold_build2 (PLUS_EXPR, type1, iv1->base,
1618 build_int_cst (type1, 1));
1619 }
1620 else if (POINTER_TYPE_P (type))
1621 iv0->base = fold_build_pointer_plus_hwi (iv0->base, -1);
1622 else
1623 iv0->base = fold_build2 (MINUS_EXPR, type1,
1624 iv0->base, build_int_cst (type1, 1));
1625
1626 bounds_add (bnds, 1, type1);
1627
1628 return number_of_iterations_lt (loop, type, iv0, iv1, niter, exit_must_be_taken,
1629 bnds);
1630 }
1631
1632 /* Dumps description of affine induction variable IV to FILE. */
1633
1634 static void
dump_affine_iv(FILE * file,affine_iv * iv)1635 dump_affine_iv (FILE *file, affine_iv *iv)
1636 {
1637 if (!integer_zerop (iv->step))
1638 fprintf (file, "[");
1639
1640 print_generic_expr (dump_file, iv->base, TDF_SLIM);
1641
1642 if (!integer_zerop (iv->step))
1643 {
1644 fprintf (file, ", + , ");
1645 print_generic_expr (dump_file, iv->step, TDF_SLIM);
1646 fprintf (file, "]%s", iv->no_overflow ? "(no_overflow)" : "");
1647 }
1648 }
1649
1650 /* Given exit condition IV0 CODE IV1 in TYPE, this function adjusts
1651 the condition for loop-until-wrap cases. For example:
1652 (unsigned){8, -1}_loop < 10 => {0, 1} != 9
1653 10 < (unsigned){0, max - 7}_loop => {0, 1} != 8
1654 Return true if condition is successfully adjusted. */
1655
1656 static bool
adjust_cond_for_loop_until_wrap(tree type,affine_iv * iv0,tree_code * code,affine_iv * iv1)1657 adjust_cond_for_loop_until_wrap (tree type, affine_iv *iv0, tree_code *code,
1658 affine_iv *iv1)
1659 {
1660 /* Only support simple cases for the moment. */
1661 if (TREE_CODE (iv0->base) != INTEGER_CST
1662 || TREE_CODE (iv1->base) != INTEGER_CST)
1663 return false;
1664
1665 tree niter_type = unsigned_type_for (type), high, low;
1666 /* Case: i-- < 10. */
1667 if (integer_zerop (iv1->step))
1668 {
1669 /* TODO: Should handle case in which abs(step) != 1. */
1670 if (!integer_minus_onep (iv0->step))
1671 return false;
1672 /* Give up on infinite loop. */
1673 if (*code == LE_EXPR
1674 && tree_int_cst_equal (iv1->base, TYPE_MAX_VALUE (type)))
1675 return false;
1676 high = fold_build2 (PLUS_EXPR, niter_type,
1677 fold_convert (niter_type, iv0->base),
1678 build_int_cst (niter_type, 1));
1679 low = fold_convert (niter_type, TYPE_MIN_VALUE (type));
1680 }
1681 else if (integer_zerop (iv0->step))
1682 {
1683 /* TODO: Should handle case in which abs(step) != 1. */
1684 if (!integer_onep (iv1->step))
1685 return false;
1686 /* Give up on infinite loop. */
1687 if (*code == LE_EXPR
1688 && tree_int_cst_equal (iv0->base, TYPE_MIN_VALUE (type)))
1689 return false;
1690 high = fold_convert (niter_type, TYPE_MAX_VALUE (type));
1691 low = fold_build2 (MINUS_EXPR, niter_type,
1692 fold_convert (niter_type, iv1->base),
1693 build_int_cst (niter_type, 1));
1694 }
1695 else
1696 gcc_unreachable ();
1697
1698 iv0->base = low;
1699 iv0->step = fold_convert (niter_type, integer_one_node);
1700 iv1->base = high;
1701 iv1->step = build_int_cst (niter_type, 0);
1702 *code = NE_EXPR;
1703 return true;
1704 }
1705
1706 /* Determine the number of iterations according to condition (for staying
1707 inside loop) which compares two induction variables using comparison
1708 operator CODE. The induction variable on left side of the comparison
1709 is IV0, the right-hand side is IV1. Both induction variables must have
1710 type TYPE, which must be an integer or pointer type. The steps of the
1711 ivs must be constants (or NULL_TREE, which is interpreted as constant zero).
1712
1713 LOOP is the loop whose number of iterations we are determining.
1714
1715 ONLY_EXIT is true if we are sure this is the only way the loop could be
1716 exited (including possibly non-returning function calls, exceptions, etc.)
1717 -- in this case we can use the information whether the control induction
1718 variables can overflow or not in a more efficient way.
1719
1720 if EVERY_ITERATION is true, we know the test is executed on every iteration.
1721
1722 The results (number of iterations and assumptions as described in
1723 comments at class tree_niter_desc in tree-ssa-loop.h) are stored to NITER.
1724 Returns false if it fails to determine number of iterations, true if it
1725 was determined (possibly with some assumptions). */
1726
1727 static bool
number_of_iterations_cond(class loop * loop,tree type,affine_iv * iv0,enum tree_code code,affine_iv * iv1,class tree_niter_desc * niter,bool only_exit,bool every_iteration)1728 number_of_iterations_cond (class loop *loop,
1729 tree type, affine_iv *iv0, enum tree_code code,
1730 affine_iv *iv1, class tree_niter_desc *niter,
1731 bool only_exit, bool every_iteration)
1732 {
1733 bool exit_must_be_taken = false, ret;
1734 bounds bnds;
1735
1736 /* If the test is not executed every iteration, wrapping may make the test
1737 to pass again.
1738 TODO: the overflow case can be still used as unreliable estimate of upper
1739 bound. But we have no API to pass it down to number of iterations code
1740 and, at present, it will not use it anyway. */
1741 if (!every_iteration
1742 && (!iv0->no_overflow || !iv1->no_overflow
1743 || code == NE_EXPR || code == EQ_EXPR))
1744 return false;
1745
1746 /* The meaning of these assumptions is this:
1747 if !assumptions
1748 then the rest of information does not have to be valid
1749 if may_be_zero then the loop does not roll, even if
1750 niter != 0. */
1751 niter->assumptions = boolean_true_node;
1752 niter->may_be_zero = boolean_false_node;
1753 niter->niter = NULL_TREE;
1754 niter->max = 0;
1755 niter->bound = NULL_TREE;
1756 niter->cmp = ERROR_MARK;
1757
1758 /* Make < comparison from > ones, and for NE_EXPR comparisons, ensure that
1759 the control variable is on lhs. */
1760 if (code == GE_EXPR || code == GT_EXPR
1761 || (code == NE_EXPR && integer_zerop (iv0->step)))
1762 {
1763 std::swap (iv0, iv1);
1764 code = swap_tree_comparison (code);
1765 }
1766
1767 if (POINTER_TYPE_P (type))
1768 {
1769 /* Comparison of pointers is undefined unless both iv0 and iv1 point
1770 to the same object. If they do, the control variable cannot wrap
1771 (as wrap around the bounds of memory will never return a pointer
1772 that would be guaranteed to point to the same object, even if we
1773 avoid undefined behavior by casting to size_t and back). */
1774 iv0->no_overflow = true;
1775 iv1->no_overflow = true;
1776 }
1777
1778 /* If the control induction variable does not overflow and the only exit
1779 from the loop is the one that we analyze, we know it must be taken
1780 eventually. */
1781 if (only_exit)
1782 {
1783 if (!integer_zerop (iv0->step) && iv0->no_overflow)
1784 exit_must_be_taken = true;
1785 else if (!integer_zerop (iv1->step) && iv1->no_overflow)
1786 exit_must_be_taken = true;
1787 }
1788
1789 /* We can handle cases which neither of the sides of the comparison is
1790 invariant:
1791
1792 {iv0.base, iv0.step} cmp_code {iv1.base, iv1.step}
1793 as if:
1794 {iv0.base, iv0.step - iv1.step} cmp_code {iv1.base, 0}
1795
1796 provided that either below condition is satisfied:
1797
1798 a) the test is NE_EXPR;
1799 b) iv0.step - iv1.step is integer and iv0/iv1 don't overflow.
1800
1801 This rarely occurs in practice, but it is simple enough to manage. */
1802 if (!integer_zerop (iv0->step) && !integer_zerop (iv1->step))
1803 {
1804 tree step_type = POINTER_TYPE_P (type) ? sizetype : type;
1805 tree step = fold_binary_to_constant (MINUS_EXPR, step_type,
1806 iv0->step, iv1->step);
1807
1808 /* No need to check sign of the new step since below code takes care
1809 of this well. */
1810 if (code != NE_EXPR
1811 && (TREE_CODE (step) != INTEGER_CST
1812 || !iv0->no_overflow || !iv1->no_overflow))
1813 return false;
1814
1815 iv0->step = step;
1816 if (!POINTER_TYPE_P (type))
1817 iv0->no_overflow = false;
1818
1819 iv1->step = build_int_cst (step_type, 0);
1820 iv1->no_overflow = true;
1821 }
1822
1823 /* If the result of the comparison is a constant, the loop is weird. More
1824 precise handling would be possible, but the situation is not common enough
1825 to waste time on it. */
1826 if (integer_zerop (iv0->step) && integer_zerop (iv1->step))
1827 return false;
1828
1829 /* If the loop exits immediately, there is nothing to do. */
1830 tree tem = fold_binary (code, boolean_type_node, iv0->base, iv1->base);
1831 if (tem && integer_zerop (tem))
1832 {
1833 if (!every_iteration)
1834 return false;
1835 niter->niter = build_int_cst (unsigned_type_for (type), 0);
1836 niter->max = 0;
1837 return true;
1838 }
1839
1840 /* Handle special case loops: while (i-- < 10) and while (10 < i++) by
1841 adjusting iv0, iv1 and code. */
1842 if (code != NE_EXPR
1843 && (tree_int_cst_sign_bit (iv0->step)
1844 || (!integer_zerop (iv1->step)
1845 && !tree_int_cst_sign_bit (iv1->step)))
1846 && !adjust_cond_for_loop_until_wrap (type, iv0, &code, iv1))
1847 return false;
1848
1849 /* OK, now we know we have a senseful loop. Handle several cases, depending
1850 on what comparison operator is used. */
1851 bound_difference (loop, iv1->base, iv0->base, &bnds);
1852
1853 if (dump_file && (dump_flags & TDF_DETAILS))
1854 {
1855 fprintf (dump_file,
1856 "Analyzing # of iterations of loop %d\n", loop->num);
1857
1858 fprintf (dump_file, " exit condition ");
1859 dump_affine_iv (dump_file, iv0);
1860 fprintf (dump_file, " %s ",
1861 code == NE_EXPR ? "!="
1862 : code == LT_EXPR ? "<"
1863 : "<=");
1864 dump_affine_iv (dump_file, iv1);
1865 fprintf (dump_file, "\n");
1866
1867 fprintf (dump_file, " bounds on difference of bases: ");
1868 mpz_out_str (dump_file, 10, bnds.below);
1869 fprintf (dump_file, " ... ");
1870 mpz_out_str (dump_file, 10, bnds.up);
1871 fprintf (dump_file, "\n");
1872 }
1873
1874 switch (code)
1875 {
1876 case NE_EXPR:
1877 gcc_assert (integer_zerop (iv1->step));
1878 ret = number_of_iterations_ne (loop, type, iv0, iv1->base, niter,
1879 exit_must_be_taken, &bnds);
1880 break;
1881
1882 case LT_EXPR:
1883 ret = number_of_iterations_lt (loop, type, iv0, iv1, niter,
1884 exit_must_be_taken, &bnds);
1885 break;
1886
1887 case LE_EXPR:
1888 ret = number_of_iterations_le (loop, type, iv0, iv1, niter,
1889 exit_must_be_taken, &bnds);
1890 break;
1891
1892 default:
1893 gcc_unreachable ();
1894 }
1895
1896 mpz_clear (bnds.up);
1897 mpz_clear (bnds.below);
1898
1899 if (dump_file && (dump_flags & TDF_DETAILS))
1900 {
1901 if (ret)
1902 {
1903 fprintf (dump_file, " result:\n");
1904 if (!integer_nonzerop (niter->assumptions))
1905 {
1906 fprintf (dump_file, " under assumptions ");
1907 print_generic_expr (dump_file, niter->assumptions, TDF_SLIM);
1908 fprintf (dump_file, "\n");
1909 }
1910
1911 if (!integer_zerop (niter->may_be_zero))
1912 {
1913 fprintf (dump_file, " zero if ");
1914 print_generic_expr (dump_file, niter->may_be_zero, TDF_SLIM);
1915 fprintf (dump_file, "\n");
1916 }
1917
1918 fprintf (dump_file, " # of iterations ");
1919 print_generic_expr (dump_file, niter->niter, TDF_SLIM);
1920 fprintf (dump_file, ", bounded by ");
1921 print_decu (niter->max, dump_file);
1922 fprintf (dump_file, "\n");
1923 }
1924 else
1925 fprintf (dump_file, " failed\n\n");
1926 }
1927 return ret;
1928 }
1929
1930 /* Substitute NEW_TREE for OLD in EXPR and fold the result.
1931 If VALUEIZE is non-NULL then OLD and NEW_TREE are ignored and instead
1932 all SSA names are replaced with the result of calling the VALUEIZE
1933 function with the SSA name as argument. */
1934
1935 tree
simplify_replace_tree(tree expr,tree old,tree new_tree,tree (* valueize)(tree,void *),void * context,bool do_fold)1936 simplify_replace_tree (tree expr, tree old, tree new_tree,
1937 tree (*valueize) (tree, void*), void *context,
1938 bool do_fold)
1939 {
1940 unsigned i, n;
1941 tree ret = NULL_TREE, e, se;
1942
1943 if (!expr)
1944 return NULL_TREE;
1945
1946 /* Do not bother to replace constants. */
1947 if (CONSTANT_CLASS_P (expr))
1948 return expr;
1949
1950 if (valueize)
1951 {
1952 if (TREE_CODE (expr) == SSA_NAME)
1953 {
1954 new_tree = valueize (expr, context);
1955 if (new_tree != expr)
1956 return new_tree;
1957 }
1958 }
1959 else if (expr == old
1960 || operand_equal_p (expr, old, 0))
1961 return unshare_expr (new_tree);
1962
1963 if (!EXPR_P (expr))
1964 return expr;
1965
1966 n = TREE_OPERAND_LENGTH (expr);
1967 for (i = 0; i < n; i++)
1968 {
1969 e = TREE_OPERAND (expr, i);
1970 se = simplify_replace_tree (e, old, new_tree, valueize, context, do_fold);
1971 if (e == se)
1972 continue;
1973
1974 if (!ret)
1975 ret = copy_node (expr);
1976
1977 TREE_OPERAND (ret, i) = se;
1978 }
1979
1980 return (ret ? (do_fold ? fold (ret) : ret) : expr);
1981 }
1982
1983 /* Expand definitions of ssa names in EXPR as long as they are simple
1984 enough, and return the new expression. If STOP is specified, stop
1985 expanding if EXPR equals to it. */
1986
1987 static tree
expand_simple_operations(tree expr,tree stop,hash_map<tree,tree> & cache)1988 expand_simple_operations (tree expr, tree stop, hash_map<tree, tree> &cache)
1989 {
1990 unsigned i, n;
1991 tree ret = NULL_TREE, e, ee, e1;
1992 enum tree_code code;
1993 gimple *stmt;
1994
1995 if (expr == NULL_TREE)
1996 return expr;
1997
1998 if (is_gimple_min_invariant (expr))
1999 return expr;
2000
2001 code = TREE_CODE (expr);
2002 if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code)))
2003 {
2004 n = TREE_OPERAND_LENGTH (expr);
2005 for (i = 0; i < n; i++)
2006 {
2007 e = TREE_OPERAND (expr, i);
2008 /* SCEV analysis feeds us with a proper expression
2009 graph matching the SSA graph. Avoid turning it
2010 into a tree here, thus handle tree sharing
2011 properly.
2012 ??? The SSA walk below still turns the SSA graph
2013 into a tree but until we find a testcase do not
2014 introduce additional tree sharing here. */
2015 bool existed_p;
2016 tree &cee = cache.get_or_insert (e, &existed_p);
2017 if (existed_p)
2018 ee = cee;
2019 else
2020 {
2021 cee = e;
2022 ee = expand_simple_operations (e, stop, cache);
2023 if (ee != e)
2024 *cache.get (e) = ee;
2025 }
2026 if (e == ee)
2027 continue;
2028
2029 if (!ret)
2030 ret = copy_node (expr);
2031
2032 TREE_OPERAND (ret, i) = ee;
2033 }
2034
2035 if (!ret)
2036 return expr;
2037
2038 fold_defer_overflow_warnings ();
2039 ret = fold (ret);
2040 fold_undefer_and_ignore_overflow_warnings ();
2041 return ret;
2042 }
2043
2044 /* Stop if it's not ssa name or the one we don't want to expand. */
2045 if (TREE_CODE (expr) != SSA_NAME || expr == stop)
2046 return expr;
2047
2048 stmt = SSA_NAME_DEF_STMT (expr);
2049 if (gimple_code (stmt) == GIMPLE_PHI)
2050 {
2051 basic_block src, dest;
2052
2053 if (gimple_phi_num_args (stmt) != 1)
2054 return expr;
2055 e = PHI_ARG_DEF (stmt, 0);
2056
2057 /* Avoid propagating through loop exit phi nodes, which
2058 could break loop-closed SSA form restrictions. */
2059 dest = gimple_bb (stmt);
2060 src = single_pred (dest);
2061 if (TREE_CODE (e) == SSA_NAME
2062 && src->loop_father != dest->loop_father)
2063 return expr;
2064
2065 return expand_simple_operations (e, stop, cache);
2066 }
2067 if (gimple_code (stmt) != GIMPLE_ASSIGN)
2068 return expr;
2069
2070 /* Avoid expanding to expressions that contain SSA names that need
2071 to take part in abnormal coalescing. */
2072 ssa_op_iter iter;
2073 FOR_EACH_SSA_TREE_OPERAND (e, stmt, iter, SSA_OP_USE)
2074 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (e))
2075 return expr;
2076
2077 e = gimple_assign_rhs1 (stmt);
2078 code = gimple_assign_rhs_code (stmt);
2079 if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
2080 {
2081 if (is_gimple_min_invariant (e))
2082 return e;
2083
2084 if (code == SSA_NAME)
2085 return expand_simple_operations (e, stop, cache);
2086 else if (code == ADDR_EXPR)
2087 {
2088 poly_int64 offset;
2089 tree base = get_addr_base_and_unit_offset (TREE_OPERAND (e, 0),
2090 &offset);
2091 if (base
2092 && TREE_CODE (base) == MEM_REF)
2093 {
2094 ee = expand_simple_operations (TREE_OPERAND (base, 0), stop,
2095 cache);
2096 return fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (expr), ee,
2097 wide_int_to_tree (sizetype,
2098 mem_ref_offset (base)
2099 + offset));
2100 }
2101 }
2102
2103 return expr;
2104 }
2105
2106 switch (code)
2107 {
2108 CASE_CONVERT:
2109 /* Casts are simple. */
2110 ee = expand_simple_operations (e, stop, cache);
2111 return fold_build1 (code, TREE_TYPE (expr), ee);
2112
2113 case PLUS_EXPR:
2114 case MINUS_EXPR:
2115 if (ANY_INTEGRAL_TYPE_P (TREE_TYPE (expr))
2116 && TYPE_OVERFLOW_TRAPS (TREE_TYPE (expr)))
2117 return expr;
2118 /* Fallthru. */
2119 case POINTER_PLUS_EXPR:
2120 /* And increments and decrements by a constant are simple. */
2121 e1 = gimple_assign_rhs2 (stmt);
2122 if (!is_gimple_min_invariant (e1))
2123 return expr;
2124
2125 ee = expand_simple_operations (e, stop, cache);
2126 return fold_build2 (code, TREE_TYPE (expr), ee, e1);
2127
2128 default:
2129 return expr;
2130 }
2131 }
2132
2133 tree
expand_simple_operations(tree expr,tree stop)2134 expand_simple_operations (tree expr, tree stop)
2135 {
2136 hash_map<tree, tree> cache;
2137 return expand_simple_operations (expr, stop, cache);
2138 }
2139
2140 /* Tries to simplify EXPR using the condition COND. Returns the simplified
2141 expression (or EXPR unchanged, if no simplification was possible). */
2142
2143 static tree
tree_simplify_using_condition_1(tree cond,tree expr)2144 tree_simplify_using_condition_1 (tree cond, tree expr)
2145 {
2146 bool changed;
2147 tree e, e0, e1, e2, notcond;
2148 enum tree_code code = TREE_CODE (expr);
2149
2150 if (code == INTEGER_CST)
2151 return expr;
2152
2153 if (code == TRUTH_OR_EXPR
2154 || code == TRUTH_AND_EXPR
2155 || code == COND_EXPR)
2156 {
2157 changed = false;
2158
2159 e0 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 0));
2160 if (TREE_OPERAND (expr, 0) != e0)
2161 changed = true;
2162
2163 e1 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 1));
2164 if (TREE_OPERAND (expr, 1) != e1)
2165 changed = true;
2166
2167 if (code == COND_EXPR)
2168 {
2169 e2 = tree_simplify_using_condition_1 (cond, TREE_OPERAND (expr, 2));
2170 if (TREE_OPERAND (expr, 2) != e2)
2171 changed = true;
2172 }
2173 else
2174 e2 = NULL_TREE;
2175
2176 if (changed)
2177 {
2178 if (code == COND_EXPR)
2179 expr = fold_build3 (code, boolean_type_node, e0, e1, e2);
2180 else
2181 expr = fold_build2 (code, boolean_type_node, e0, e1);
2182 }
2183
2184 return expr;
2185 }
2186
2187 /* In case COND is equality, we may be able to simplify EXPR by copy/constant
2188 propagation, and vice versa. Fold does not handle this, since it is
2189 considered too expensive. */
2190 if (TREE_CODE (cond) == EQ_EXPR)
2191 {
2192 e0 = TREE_OPERAND (cond, 0);
2193 e1 = TREE_OPERAND (cond, 1);
2194
2195 /* We know that e0 == e1. Check whether we cannot simplify expr
2196 using this fact. */
2197 e = simplify_replace_tree (expr, e0, e1);
2198 if (integer_zerop (e) || integer_nonzerop (e))
2199 return e;
2200
2201 e = simplify_replace_tree (expr, e1, e0);
2202 if (integer_zerop (e) || integer_nonzerop (e))
2203 return e;
2204 }
2205 if (TREE_CODE (expr) == EQ_EXPR)
2206 {
2207 e0 = TREE_OPERAND (expr, 0);
2208 e1 = TREE_OPERAND (expr, 1);
2209
2210 /* If e0 == e1 (EXPR) implies !COND, then EXPR cannot be true. */
2211 e = simplify_replace_tree (cond, e0, e1);
2212 if (integer_zerop (e))
2213 return e;
2214 e = simplify_replace_tree (cond, e1, e0);
2215 if (integer_zerop (e))
2216 return e;
2217 }
2218 if (TREE_CODE (expr) == NE_EXPR)
2219 {
2220 e0 = TREE_OPERAND (expr, 0);
2221 e1 = TREE_OPERAND (expr, 1);
2222
2223 /* If e0 == e1 (!EXPR) implies !COND, then EXPR must be true. */
2224 e = simplify_replace_tree (cond, e0, e1);
2225 if (integer_zerop (e))
2226 return boolean_true_node;
2227 e = simplify_replace_tree (cond, e1, e0);
2228 if (integer_zerop (e))
2229 return boolean_true_node;
2230 }
2231
2232 /* Check whether COND ==> EXPR. */
2233 notcond = invert_truthvalue (cond);
2234 e = fold_binary (TRUTH_OR_EXPR, boolean_type_node, notcond, expr);
2235 if (e && integer_nonzerop (e))
2236 return e;
2237
2238 /* Check whether COND ==> not EXPR. */
2239 e = fold_binary (TRUTH_AND_EXPR, boolean_type_node, cond, expr);
2240 if (e && integer_zerop (e))
2241 return e;
2242
2243 return expr;
2244 }
2245
2246 /* Tries to simplify EXPR using the condition COND. Returns the simplified
2247 expression (or EXPR unchanged, if no simplification was possible).
2248 Wrapper around tree_simplify_using_condition_1 that ensures that chains
2249 of simple operations in definitions of ssa names in COND are expanded,
2250 so that things like casts or incrementing the value of the bound before
2251 the loop do not cause us to fail. */
2252
2253 static tree
tree_simplify_using_condition(tree cond,tree expr)2254 tree_simplify_using_condition (tree cond, tree expr)
2255 {
2256 cond = expand_simple_operations (cond);
2257
2258 return tree_simplify_using_condition_1 (cond, expr);
2259 }
2260
2261 /* Tries to simplify EXPR using the conditions on entry to LOOP.
2262 Returns the simplified expression (or EXPR unchanged, if no
2263 simplification was possible). */
2264
2265 tree
simplify_using_initial_conditions(class loop * loop,tree expr)2266 simplify_using_initial_conditions (class loop *loop, tree expr)
2267 {
2268 edge e;
2269 basic_block bb;
2270 gimple *stmt;
2271 tree cond, expanded, backup;
2272 int cnt = 0;
2273
2274 if (TREE_CODE (expr) == INTEGER_CST)
2275 return expr;
2276
2277 backup = expanded = expand_simple_operations (expr);
2278
2279 /* Limit walking the dominators to avoid quadraticness in
2280 the number of BBs times the number of loops in degenerate
2281 cases. */
2282 for (bb = loop->header;
2283 bb != ENTRY_BLOCK_PTR_FOR_FN (cfun) && cnt < MAX_DOMINATORS_TO_WALK;
2284 bb = get_immediate_dominator (CDI_DOMINATORS, bb))
2285 {
2286 if (!single_pred_p (bb))
2287 continue;
2288 e = single_pred_edge (bb);
2289
2290 if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
2291 continue;
2292
2293 stmt = last_stmt (e->src);
2294 cond = fold_build2 (gimple_cond_code (stmt),
2295 boolean_type_node,
2296 gimple_cond_lhs (stmt),
2297 gimple_cond_rhs (stmt));
2298 if (e->flags & EDGE_FALSE_VALUE)
2299 cond = invert_truthvalue (cond);
2300 expanded = tree_simplify_using_condition (cond, expanded);
2301 /* Break if EXPR is simplified to const values. */
2302 if (expanded
2303 && (integer_zerop (expanded) || integer_nonzerop (expanded)))
2304 return expanded;
2305
2306 ++cnt;
2307 }
2308
2309 /* Return the original expression if no simplification is done. */
2310 return operand_equal_p (backup, expanded, 0) ? expr : expanded;
2311 }
2312
2313 /* Tries to simplify EXPR using the evolutions of the loop invariants
2314 in the superloops of LOOP. Returns the simplified expression
2315 (or EXPR unchanged, if no simplification was possible). */
2316
2317 static tree
simplify_using_outer_evolutions(class loop * loop,tree expr)2318 simplify_using_outer_evolutions (class loop *loop, tree expr)
2319 {
2320 enum tree_code code = TREE_CODE (expr);
2321 bool changed;
2322 tree e, e0, e1, e2;
2323
2324 if (is_gimple_min_invariant (expr))
2325 return expr;
2326
2327 if (code == TRUTH_OR_EXPR
2328 || code == TRUTH_AND_EXPR
2329 || code == COND_EXPR)
2330 {
2331 changed = false;
2332
2333 e0 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 0));
2334 if (TREE_OPERAND (expr, 0) != e0)
2335 changed = true;
2336
2337 e1 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 1));
2338 if (TREE_OPERAND (expr, 1) != e1)
2339 changed = true;
2340
2341 if (code == COND_EXPR)
2342 {
2343 e2 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 2));
2344 if (TREE_OPERAND (expr, 2) != e2)
2345 changed = true;
2346 }
2347 else
2348 e2 = NULL_TREE;
2349
2350 if (changed)
2351 {
2352 if (code == COND_EXPR)
2353 expr = fold_build3 (code, boolean_type_node, e0, e1, e2);
2354 else
2355 expr = fold_build2 (code, boolean_type_node, e0, e1);
2356 }
2357
2358 return expr;
2359 }
2360
2361 e = instantiate_parameters (loop, expr);
2362 if (is_gimple_min_invariant (e))
2363 return e;
2364
2365 return expr;
2366 }
2367
2368 /* Returns true if EXIT is the only possible exit from LOOP. */
2369
2370 bool
loop_only_exit_p(const class loop * loop,basic_block * body,const_edge exit)2371 loop_only_exit_p (const class loop *loop, basic_block *body, const_edge exit)
2372 {
2373 gimple_stmt_iterator bsi;
2374 unsigned i;
2375
2376 if (exit != single_exit (loop))
2377 return false;
2378
2379 for (i = 0; i < loop->num_nodes; i++)
2380 for (bsi = gsi_start_bb (body[i]); !gsi_end_p (bsi); gsi_next (&bsi))
2381 if (stmt_can_terminate_bb_p (gsi_stmt (bsi)))
2382 return false;
2383
2384 return true;
2385 }
2386
2387 /* Stores description of number of iterations of LOOP derived from
2388 EXIT (an exit edge of the LOOP) in NITER. Returns true if some useful
2389 information could be derived (and fields of NITER have meaning described
2390 in comments at class tree_niter_desc declaration), false otherwise.
2391 When EVERY_ITERATION is true, only tests that are known to be executed
2392 every iteration are considered (i.e. only test that alone bounds the loop).
2393 If AT_STMT is not NULL, this function stores LOOP's condition statement in
2394 it when returning true. */
2395
2396 bool
number_of_iterations_exit_assumptions(class loop * loop,edge exit,class tree_niter_desc * niter,gcond ** at_stmt,bool every_iteration,basic_block * body)2397 number_of_iterations_exit_assumptions (class loop *loop, edge exit,
2398 class tree_niter_desc *niter,
2399 gcond **at_stmt, bool every_iteration,
2400 basic_block *body)
2401 {
2402 gimple *last;
2403 gcond *stmt;
2404 tree type;
2405 tree op0, op1;
2406 enum tree_code code;
2407 affine_iv iv0, iv1;
2408 bool safe;
2409
2410 /* The condition at a fake exit (if it exists) does not control its
2411 execution. */
2412 if (exit->flags & EDGE_FAKE)
2413 return false;
2414
2415 /* Nothing to analyze if the loop is known to be infinite. */
2416 if (loop_constraint_set_p (loop, LOOP_C_INFINITE))
2417 return false;
2418
2419 safe = dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src);
2420
2421 if (every_iteration && !safe)
2422 return false;
2423
2424 niter->assumptions = boolean_false_node;
2425 niter->control.base = NULL_TREE;
2426 niter->control.step = NULL_TREE;
2427 niter->control.no_overflow = false;
2428 last = last_stmt (exit->src);
2429 if (!last)
2430 return false;
2431 stmt = dyn_cast <gcond *> (last);
2432 if (!stmt)
2433 return false;
2434
2435 /* We want the condition for staying inside loop. */
2436 code = gimple_cond_code (stmt);
2437 if (exit->flags & EDGE_TRUE_VALUE)
2438 code = invert_tree_comparison (code, false);
2439
2440 switch (code)
2441 {
2442 case GT_EXPR:
2443 case GE_EXPR:
2444 case LT_EXPR:
2445 case LE_EXPR:
2446 case NE_EXPR:
2447 break;
2448
2449 default:
2450 return false;
2451 }
2452
2453 op0 = gimple_cond_lhs (stmt);
2454 op1 = gimple_cond_rhs (stmt);
2455 type = TREE_TYPE (op0);
2456
2457 if (TREE_CODE (type) != INTEGER_TYPE
2458 && !POINTER_TYPE_P (type))
2459 return false;
2460
2461 tree iv0_niters = NULL_TREE;
2462 if (!simple_iv_with_niters (loop, loop_containing_stmt (stmt),
2463 op0, &iv0, safe ? &iv0_niters : NULL, false))
2464 return number_of_iterations_popcount (loop, exit, code, niter);
2465 tree iv1_niters = NULL_TREE;
2466 if (!simple_iv_with_niters (loop, loop_containing_stmt (stmt),
2467 op1, &iv1, safe ? &iv1_niters : NULL, false))
2468 return false;
2469 /* Give up on complicated case. */
2470 if (iv0_niters && iv1_niters)
2471 return false;
2472
2473 /* We don't want to see undefined signed overflow warnings while
2474 computing the number of iterations. */
2475 fold_defer_overflow_warnings ();
2476
2477 iv0.base = expand_simple_operations (iv0.base);
2478 iv1.base = expand_simple_operations (iv1.base);
2479 bool body_from_caller = true;
2480 if (!body)
2481 {
2482 body = get_loop_body (loop);
2483 body_from_caller = false;
2484 }
2485 bool only_exit_p = loop_only_exit_p (loop, body, exit);
2486 if (!body_from_caller)
2487 free (body);
2488 if (!number_of_iterations_cond (loop, type, &iv0, code, &iv1, niter,
2489 only_exit_p, safe))
2490 {
2491 fold_undefer_and_ignore_overflow_warnings ();
2492 return false;
2493 }
2494
2495 /* Incorporate additional assumption implied by control iv. */
2496 tree iv_niters = iv0_niters ? iv0_niters : iv1_niters;
2497 if (iv_niters)
2498 {
2499 tree assumption = fold_build2 (LE_EXPR, boolean_type_node, niter->niter,
2500 fold_convert (TREE_TYPE (niter->niter),
2501 iv_niters));
2502
2503 if (!integer_nonzerop (assumption))
2504 niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
2505 niter->assumptions, assumption);
2506
2507 /* Refine upper bound if possible. */
2508 if (TREE_CODE (iv_niters) == INTEGER_CST
2509 && niter->max > wi::to_widest (iv_niters))
2510 niter->max = wi::to_widest (iv_niters);
2511 }
2512
2513 /* There is no assumptions if the loop is known to be finite. */
2514 if (!integer_zerop (niter->assumptions)
2515 && loop_constraint_set_p (loop, LOOP_C_FINITE))
2516 niter->assumptions = boolean_true_node;
2517
2518 if (optimize >= 3)
2519 {
2520 niter->assumptions = simplify_using_outer_evolutions (loop,
2521 niter->assumptions);
2522 niter->may_be_zero = simplify_using_outer_evolutions (loop,
2523 niter->may_be_zero);
2524 niter->niter = simplify_using_outer_evolutions (loop, niter->niter);
2525 }
2526
2527 niter->assumptions
2528 = simplify_using_initial_conditions (loop,
2529 niter->assumptions);
2530 niter->may_be_zero
2531 = simplify_using_initial_conditions (loop,
2532 niter->may_be_zero);
2533
2534 fold_undefer_and_ignore_overflow_warnings ();
2535
2536 /* If NITER has simplified into a constant, update MAX. */
2537 if (TREE_CODE (niter->niter) == INTEGER_CST)
2538 niter->max = wi::to_widest (niter->niter);
2539
2540 if (at_stmt)
2541 *at_stmt = stmt;
2542
2543 return (!integer_zerop (niter->assumptions));
2544 }
2545
2546
2547 /* Utility function to check if OP is defined by a stmt
2548 that is a val - 1. */
2549
2550 static bool
ssa_defined_by_minus_one_stmt_p(tree op,tree val)2551 ssa_defined_by_minus_one_stmt_p (tree op, tree val)
2552 {
2553 gimple *stmt;
2554 return (TREE_CODE (op) == SSA_NAME
2555 && (stmt = SSA_NAME_DEF_STMT (op))
2556 && is_gimple_assign (stmt)
2557 && (gimple_assign_rhs_code (stmt) == PLUS_EXPR)
2558 && val == gimple_assign_rhs1 (stmt)
2559 && integer_minus_onep (gimple_assign_rhs2 (stmt)));
2560 }
2561
2562
2563 /* See if LOOP is a popcout implementation, determine NITER for the loop
2564
2565 We match:
2566 <bb 2>
2567 goto <bb 4>
2568
2569 <bb 3>
2570 _1 = b_11 + -1
2571 b_6 = _1 & b_11
2572
2573 <bb 4>
2574 b_11 = PHI <b_5(D)(2), b_6(3)>
2575
2576 exit block
2577 if (b_11 != 0)
2578 goto <bb 3>
2579 else
2580 goto <bb 5>
2581
2582 OR we match copy-header version:
2583 if (b_5 != 0)
2584 goto <bb 3>
2585 else
2586 goto <bb 4>
2587
2588 <bb 3>
2589 b_11 = PHI <b_5(2), b_6(3)>
2590 _1 = b_11 + -1
2591 b_6 = _1 & b_11
2592
2593 exit block
2594 if (b_6 != 0)
2595 goto <bb 3>
2596 else
2597 goto <bb 4>
2598
2599 If popcount pattern, update NITER accordingly.
2600 i.e., set NITER to __builtin_popcount (b)
2601 return true if we did, false otherwise.
2602
2603 */
2604
2605 static bool
number_of_iterations_popcount(loop_p loop,edge exit,enum tree_code code,class tree_niter_desc * niter)2606 number_of_iterations_popcount (loop_p loop, edge exit,
2607 enum tree_code code,
2608 class tree_niter_desc *niter)
2609 {
2610 bool adjust = true;
2611 tree iter;
2612 HOST_WIDE_INT max;
2613 adjust = true;
2614 tree fn = NULL_TREE;
2615
2616 /* Check loop terminating branch is like
2617 if (b != 0). */
2618 gimple *stmt = last_stmt (exit->src);
2619 if (!stmt
2620 || gimple_code (stmt) != GIMPLE_COND
2621 || code != NE_EXPR
2622 || !integer_zerop (gimple_cond_rhs (stmt))
2623 || TREE_CODE (gimple_cond_lhs (stmt)) != SSA_NAME)
2624 return false;
2625
2626 gimple *and_stmt = SSA_NAME_DEF_STMT (gimple_cond_lhs (stmt));
2627
2628 /* Depending on copy-header is performed, feeding PHI stmts might be in
2629 the loop header or loop latch, handle this. */
2630 if (gimple_code (and_stmt) == GIMPLE_PHI
2631 && gimple_bb (and_stmt) == loop->header
2632 && gimple_phi_num_args (and_stmt) == 2
2633 && (TREE_CODE (gimple_phi_arg_def (and_stmt,
2634 loop_latch_edge (loop)->dest_idx))
2635 == SSA_NAME))
2636 {
2637 /* SSA used in exit condition is defined by PHI stmt
2638 b_11 = PHI <b_5(D)(2), b_6(3)>
2639 from the PHI stmt, get the and_stmt
2640 b_6 = _1 & b_11. */
2641 tree t = gimple_phi_arg_def (and_stmt, loop_latch_edge (loop)->dest_idx);
2642 and_stmt = SSA_NAME_DEF_STMT (t);
2643 adjust = false;
2644 }
2645
2646 /* Make sure it is indeed an and stmt (b_6 = _1 & b_11). */
2647 if (!is_gimple_assign (and_stmt)
2648 || gimple_assign_rhs_code (and_stmt) != BIT_AND_EXPR)
2649 return false;
2650
2651 tree b_11 = gimple_assign_rhs1 (and_stmt);
2652 tree _1 = gimple_assign_rhs2 (and_stmt);
2653
2654 /* Check that _1 is defined by _b11 + -1 (_1 = b_11 + -1).
2655 Also make sure that b_11 is the same in and_stmt and _1 defining stmt.
2656 Also canonicalize if _1 and _b11 are revrsed. */
2657 if (ssa_defined_by_minus_one_stmt_p (b_11, _1))
2658 std::swap (b_11, _1);
2659 else if (ssa_defined_by_minus_one_stmt_p (_1, b_11))
2660 ;
2661 else
2662 return false;
2663 /* Check the recurrence:
2664 ... = PHI <b_5(2), b_6(3)>. */
2665 gimple *phi = SSA_NAME_DEF_STMT (b_11);
2666 if (gimple_code (phi) != GIMPLE_PHI
2667 || (gimple_bb (phi) != loop_latch_edge (loop)->dest)
2668 || (gimple_assign_lhs (and_stmt)
2669 != gimple_phi_arg_def (phi, loop_latch_edge (loop)->dest_idx)))
2670 return false;
2671
2672 /* We found a match. Get the corresponding popcount builtin. */
2673 tree src = gimple_phi_arg_def (phi, loop_preheader_edge (loop)->dest_idx);
2674 if (TYPE_PRECISION (TREE_TYPE (src)) == TYPE_PRECISION (integer_type_node))
2675 fn = builtin_decl_implicit (BUILT_IN_POPCOUNT);
2676 else if (TYPE_PRECISION (TREE_TYPE (src)) == TYPE_PRECISION
2677 (long_integer_type_node))
2678 fn = builtin_decl_implicit (BUILT_IN_POPCOUNTL);
2679 else if (TYPE_PRECISION (TREE_TYPE (src)) == TYPE_PRECISION
2680 (long_long_integer_type_node))
2681 fn = builtin_decl_implicit (BUILT_IN_POPCOUNTLL);
2682
2683 /* ??? Support promoting char/short to int. */
2684 if (!fn)
2685 return false;
2686
2687 /* Update NITER params accordingly */
2688 tree utype = unsigned_type_for (TREE_TYPE (src));
2689 src = fold_convert (utype, src);
2690 tree call = fold_convert (utype, build_call_expr (fn, 1, src));
2691 if (adjust)
2692 iter = fold_build2 (MINUS_EXPR, utype,
2693 call,
2694 build_int_cst (utype, 1));
2695 else
2696 iter = call;
2697
2698 if (TREE_CODE (call) == INTEGER_CST)
2699 max = tree_to_uhwi (call);
2700 else
2701 max = TYPE_PRECISION (TREE_TYPE (src));
2702 if (adjust)
2703 max = max - 1;
2704
2705 niter->niter = iter;
2706 niter->assumptions = boolean_true_node;
2707
2708 if (adjust)
2709 {
2710 tree may_be_zero = fold_build2 (EQ_EXPR, boolean_type_node, src,
2711 build_zero_cst
2712 (TREE_TYPE (src)));
2713 niter->may_be_zero =
2714 simplify_using_initial_conditions (loop, may_be_zero);
2715 }
2716 else
2717 niter->may_be_zero = boolean_false_node;
2718
2719 niter->max = max;
2720 niter->bound = NULL_TREE;
2721 niter->cmp = ERROR_MARK;
2722 return true;
2723 }
2724
2725
2726 /* Like number_of_iterations_exit_assumptions, but return TRUE only if
2727 the niter information holds unconditionally. */
2728
2729 bool
number_of_iterations_exit(class loop * loop,edge exit,class tree_niter_desc * niter,bool warn,bool every_iteration,basic_block * body)2730 number_of_iterations_exit (class loop *loop, edge exit,
2731 class tree_niter_desc *niter,
2732 bool warn, bool every_iteration,
2733 basic_block *body)
2734 {
2735 gcond *stmt;
2736 if (!number_of_iterations_exit_assumptions (loop, exit, niter,
2737 &stmt, every_iteration, body))
2738 return false;
2739
2740 if (integer_nonzerop (niter->assumptions))
2741 return true;
2742
2743 if (warn && dump_enabled_p ())
2744 dump_printf_loc (MSG_MISSED_OPTIMIZATION, stmt,
2745 "missed loop optimization: niters analysis ends up "
2746 "with assumptions.\n");
2747
2748 return false;
2749 }
2750
2751 /* Try to determine the number of iterations of LOOP. If we succeed,
2752 expression giving number of iterations is returned and *EXIT is
2753 set to the edge from that the information is obtained. Otherwise
2754 chrec_dont_know is returned. */
2755
2756 tree
find_loop_niter(class loop * loop,edge * exit)2757 find_loop_niter (class loop *loop, edge *exit)
2758 {
2759 unsigned i;
2760 vec<edge> exits = get_loop_exit_edges (loop);
2761 edge ex;
2762 tree niter = NULL_TREE, aniter;
2763 class tree_niter_desc desc;
2764
2765 *exit = NULL;
2766 FOR_EACH_VEC_ELT (exits, i, ex)
2767 {
2768 if (!number_of_iterations_exit (loop, ex, &desc, false))
2769 continue;
2770
2771 if (integer_nonzerop (desc.may_be_zero))
2772 {
2773 /* We exit in the first iteration through this exit.
2774 We won't find anything better. */
2775 niter = build_int_cst (unsigned_type_node, 0);
2776 *exit = ex;
2777 break;
2778 }
2779
2780 if (!integer_zerop (desc.may_be_zero))
2781 continue;
2782
2783 aniter = desc.niter;
2784
2785 if (!niter)
2786 {
2787 /* Nothing recorded yet. */
2788 niter = aniter;
2789 *exit = ex;
2790 continue;
2791 }
2792
2793 /* Prefer constants, the lower the better. */
2794 if (TREE_CODE (aniter) != INTEGER_CST)
2795 continue;
2796
2797 if (TREE_CODE (niter) != INTEGER_CST)
2798 {
2799 niter = aniter;
2800 *exit = ex;
2801 continue;
2802 }
2803
2804 if (tree_int_cst_lt (aniter, niter))
2805 {
2806 niter = aniter;
2807 *exit = ex;
2808 continue;
2809 }
2810 }
2811 exits.release ();
2812
2813 return niter ? niter : chrec_dont_know;
2814 }
2815
2816 /* Return true if loop is known to have bounded number of iterations. */
2817
2818 bool
finite_loop_p(class loop * loop)2819 finite_loop_p (class loop *loop)
2820 {
2821 widest_int nit;
2822 int flags;
2823
2824 flags = flags_from_decl_or_type (current_function_decl);
2825 if ((flags & (ECF_CONST|ECF_PURE)) && !(flags & ECF_LOOPING_CONST_OR_PURE))
2826 {
2827 if (dump_file && (dump_flags & TDF_DETAILS))
2828 fprintf (dump_file, "Found loop %i to be finite: it is within pure or const function.\n",
2829 loop->num);
2830 return true;
2831 }
2832
2833 if (loop->any_upper_bound
2834 || max_loop_iterations (loop, &nit))
2835 {
2836 if (dump_file && (dump_flags & TDF_DETAILS))
2837 fprintf (dump_file, "Found loop %i to be finite: upper bound found.\n",
2838 loop->num);
2839 return true;
2840 }
2841
2842 if (loop->finite_p)
2843 {
2844 unsigned i;
2845 vec<edge> exits = get_loop_exit_edges (loop);
2846 edge ex;
2847
2848 /* If the loop has a normal exit, we can assume it will terminate. */
2849 FOR_EACH_VEC_ELT (exits, i, ex)
2850 if (!(ex->flags & (EDGE_EH | EDGE_ABNORMAL | EDGE_FAKE)))
2851 {
2852 exits.release ();
2853 if (dump_file)
2854 fprintf (dump_file, "Assume loop %i to be finite: it has an exit "
2855 "and -ffinite-loops is on.\n", loop->num);
2856 return true;
2857 }
2858
2859 exits.release ();
2860 }
2861
2862 return false;
2863 }
2864
2865 /*
2866
2867 Analysis of a number of iterations of a loop by a brute-force evaluation.
2868
2869 */
2870
2871 /* Bound on the number of iterations we try to evaluate. */
2872
2873 #define MAX_ITERATIONS_TO_TRACK \
2874 ((unsigned) param_max_iterations_to_track)
2875
2876 /* Returns the loop phi node of LOOP such that ssa name X is derived from its
2877 result by a chain of operations such that all but exactly one of their
2878 operands are constants. */
2879
2880 static gphi *
chain_of_csts_start(class loop * loop,tree x)2881 chain_of_csts_start (class loop *loop, tree x)
2882 {
2883 gimple *stmt = SSA_NAME_DEF_STMT (x);
2884 tree use;
2885 basic_block bb = gimple_bb (stmt);
2886 enum tree_code code;
2887
2888 if (!bb
2889 || !flow_bb_inside_loop_p (loop, bb))
2890 return NULL;
2891
2892 if (gimple_code (stmt) == GIMPLE_PHI)
2893 {
2894 if (bb == loop->header)
2895 return as_a <gphi *> (stmt);
2896
2897 return NULL;
2898 }
2899
2900 if (gimple_code (stmt) != GIMPLE_ASSIGN
2901 || gimple_assign_rhs_class (stmt) == GIMPLE_TERNARY_RHS)
2902 return NULL;
2903
2904 code = gimple_assign_rhs_code (stmt);
2905 if (gimple_references_memory_p (stmt)
2906 || TREE_CODE_CLASS (code) == tcc_reference
2907 || (code == ADDR_EXPR
2908 && !is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
2909 return NULL;
2910
2911 use = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
2912 if (use == NULL_TREE)
2913 return NULL;
2914
2915 return chain_of_csts_start (loop, use);
2916 }
2917
2918 /* Determines whether the expression X is derived from a result of a phi node
2919 in header of LOOP such that
2920
2921 * the derivation of X consists only from operations with constants
2922 * the initial value of the phi node is constant
2923 * the value of the phi node in the next iteration can be derived from the
2924 value in the current iteration by a chain of operations with constants,
2925 or is also a constant
2926
2927 If such phi node exists, it is returned, otherwise NULL is returned. */
2928
2929 static gphi *
get_base_for(class loop * loop,tree x)2930 get_base_for (class loop *loop, tree x)
2931 {
2932 gphi *phi;
2933 tree init, next;
2934
2935 if (is_gimple_min_invariant (x))
2936 return NULL;
2937
2938 phi = chain_of_csts_start (loop, x);
2939 if (!phi)
2940 return NULL;
2941
2942 init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
2943 next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
2944
2945 if (!is_gimple_min_invariant (init))
2946 return NULL;
2947
2948 if (TREE_CODE (next) == SSA_NAME
2949 && chain_of_csts_start (loop, next) != phi)
2950 return NULL;
2951
2952 return phi;
2953 }
2954
2955 /* Given an expression X, then
2956
2957 * if X is NULL_TREE, we return the constant BASE.
2958 * if X is a constant, we return the constant X.
2959 * otherwise X is a SSA name, whose value in the considered loop is derived
2960 by a chain of operations with constant from a result of a phi node in
2961 the header of the loop. Then we return value of X when the value of the
2962 result of this phi node is given by the constant BASE. */
2963
2964 static tree
get_val_for(tree x,tree base)2965 get_val_for (tree x, tree base)
2966 {
2967 gimple *stmt;
2968
2969 gcc_checking_assert (is_gimple_min_invariant (base));
2970
2971 if (!x)
2972 return base;
2973 else if (is_gimple_min_invariant (x))
2974 return x;
2975
2976 stmt = SSA_NAME_DEF_STMT (x);
2977 if (gimple_code (stmt) == GIMPLE_PHI)
2978 return base;
2979
2980 gcc_checking_assert (is_gimple_assign (stmt));
2981
2982 /* STMT must be either an assignment of a single SSA name or an
2983 expression involving an SSA name and a constant. Try to fold that
2984 expression using the value for the SSA name. */
2985 if (gimple_assign_ssa_name_copy_p (stmt))
2986 return get_val_for (gimple_assign_rhs1 (stmt), base);
2987 else if (gimple_assign_rhs_class (stmt) == GIMPLE_UNARY_RHS
2988 && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)
2989 return fold_build1 (gimple_assign_rhs_code (stmt),
2990 gimple_expr_type (stmt),
2991 get_val_for (gimple_assign_rhs1 (stmt), base));
2992 else if (gimple_assign_rhs_class (stmt) == GIMPLE_BINARY_RHS)
2993 {
2994 tree rhs1 = gimple_assign_rhs1 (stmt);
2995 tree rhs2 = gimple_assign_rhs2 (stmt);
2996 if (TREE_CODE (rhs1) == SSA_NAME)
2997 rhs1 = get_val_for (rhs1, base);
2998 else if (TREE_CODE (rhs2) == SSA_NAME)
2999 rhs2 = get_val_for (rhs2, base);
3000 else
3001 gcc_unreachable ();
3002 return fold_build2 (gimple_assign_rhs_code (stmt),
3003 gimple_expr_type (stmt), rhs1, rhs2);
3004 }
3005 else
3006 gcc_unreachable ();
3007 }
3008
3009
3010 /* Tries to count the number of iterations of LOOP till it exits by EXIT
3011 by brute force -- i.e. by determining the value of the operands of the
3012 condition at EXIT in first few iterations of the loop (assuming that
3013 these values are constant) and determining the first one in that the
3014 condition is not satisfied. Returns the constant giving the number
3015 of the iterations of LOOP if successful, chrec_dont_know otherwise. */
3016
3017 tree
loop_niter_by_eval(class loop * loop,edge exit)3018 loop_niter_by_eval (class loop *loop, edge exit)
3019 {
3020 tree acnd;
3021 tree op[2], val[2], next[2], aval[2];
3022 gphi *phi;
3023 gimple *cond;
3024 unsigned i, j;
3025 enum tree_code cmp;
3026
3027 cond = last_stmt (exit->src);
3028 if (!cond || gimple_code (cond) != GIMPLE_COND)
3029 return chrec_dont_know;
3030
3031 cmp = gimple_cond_code (cond);
3032 if (exit->flags & EDGE_TRUE_VALUE)
3033 cmp = invert_tree_comparison (cmp, false);
3034
3035 switch (cmp)
3036 {
3037 case EQ_EXPR:
3038 case NE_EXPR:
3039 case GT_EXPR:
3040 case GE_EXPR:
3041 case LT_EXPR:
3042 case LE_EXPR:
3043 op[0] = gimple_cond_lhs (cond);
3044 op[1] = gimple_cond_rhs (cond);
3045 break;
3046
3047 default:
3048 return chrec_dont_know;
3049 }
3050
3051 for (j = 0; j < 2; j++)
3052 {
3053 if (is_gimple_min_invariant (op[j]))
3054 {
3055 val[j] = op[j];
3056 next[j] = NULL_TREE;
3057 op[j] = NULL_TREE;
3058 }
3059 else
3060 {
3061 phi = get_base_for (loop, op[j]);
3062 if (!phi)
3063 return chrec_dont_know;
3064 val[j] = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
3065 next[j] = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
3066 }
3067 }
3068
3069 /* Don't issue signed overflow warnings. */
3070 fold_defer_overflow_warnings ();
3071
3072 for (i = 0; i < MAX_ITERATIONS_TO_TRACK; i++)
3073 {
3074 for (j = 0; j < 2; j++)
3075 aval[j] = get_val_for (op[j], val[j]);
3076
3077 acnd = fold_binary (cmp, boolean_type_node, aval[0], aval[1]);
3078 if (acnd && integer_zerop (acnd))
3079 {
3080 fold_undefer_and_ignore_overflow_warnings ();
3081 if (dump_file && (dump_flags & TDF_DETAILS))
3082 fprintf (dump_file,
3083 "Proved that loop %d iterates %d times using brute force.\n",
3084 loop->num, i);
3085 return build_int_cst (unsigned_type_node, i);
3086 }
3087
3088 for (j = 0; j < 2; j++)
3089 {
3090 aval[j] = val[j];
3091 val[j] = get_val_for (next[j], val[j]);
3092 if (!is_gimple_min_invariant (val[j]))
3093 {
3094 fold_undefer_and_ignore_overflow_warnings ();
3095 return chrec_dont_know;
3096 }
3097 }
3098
3099 /* If the next iteration would use the same base values
3100 as the current one, there is no point looping further,
3101 all following iterations will be the same as this one. */
3102 if (val[0] == aval[0] && val[1] == aval[1])
3103 break;
3104 }
3105
3106 fold_undefer_and_ignore_overflow_warnings ();
3107
3108 return chrec_dont_know;
3109 }
3110
3111 /* Finds the exit of the LOOP by that the loop exits after a constant
3112 number of iterations and stores the exit edge to *EXIT. The constant
3113 giving the number of iterations of LOOP is returned. The number of
3114 iterations is determined using loop_niter_by_eval (i.e. by brute force
3115 evaluation). If we are unable to find the exit for that loop_niter_by_eval
3116 determines the number of iterations, chrec_dont_know is returned. */
3117
3118 tree
find_loop_niter_by_eval(class loop * loop,edge * exit)3119 find_loop_niter_by_eval (class loop *loop, edge *exit)
3120 {
3121 unsigned i;
3122 vec<edge> exits = get_loop_exit_edges (loop);
3123 edge ex;
3124 tree niter = NULL_TREE, aniter;
3125
3126 *exit = NULL;
3127
3128 /* Loops with multiple exits are expensive to handle and less important. */
3129 if (!flag_expensive_optimizations
3130 && exits.length () > 1)
3131 {
3132 exits.release ();
3133 return chrec_dont_know;
3134 }
3135
3136 FOR_EACH_VEC_ELT (exits, i, ex)
3137 {
3138 if (!just_once_each_iteration_p (loop, ex->src))
3139 continue;
3140
3141 aniter = loop_niter_by_eval (loop, ex);
3142 if (chrec_contains_undetermined (aniter))
3143 continue;
3144
3145 if (niter
3146 && !tree_int_cst_lt (aniter, niter))
3147 continue;
3148
3149 niter = aniter;
3150 *exit = ex;
3151 }
3152 exits.release ();
3153
3154 return niter ? niter : chrec_dont_know;
3155 }
3156
3157 /*
3158
3159 Analysis of upper bounds on number of iterations of a loop.
3160
3161 */
3162
3163 static widest_int derive_constant_upper_bound_ops (tree, tree,
3164 enum tree_code, tree);
3165
3166 /* Returns a constant upper bound on the value of the right-hand side of
3167 an assignment statement STMT. */
3168
3169 static widest_int
derive_constant_upper_bound_assign(gimple * stmt)3170 derive_constant_upper_bound_assign (gimple *stmt)
3171 {
3172 enum tree_code code = gimple_assign_rhs_code (stmt);
3173 tree op0 = gimple_assign_rhs1 (stmt);
3174 tree op1 = gimple_assign_rhs2 (stmt);
3175
3176 return derive_constant_upper_bound_ops (TREE_TYPE (gimple_assign_lhs (stmt)),
3177 op0, code, op1);
3178 }
3179
3180 /* Returns a constant upper bound on the value of expression VAL. VAL
3181 is considered to be unsigned. If its type is signed, its value must
3182 be nonnegative. */
3183
3184 static widest_int
derive_constant_upper_bound(tree val)3185 derive_constant_upper_bound (tree val)
3186 {
3187 enum tree_code code;
3188 tree op0, op1, op2;
3189
3190 extract_ops_from_tree (val, &code, &op0, &op1, &op2);
3191 return derive_constant_upper_bound_ops (TREE_TYPE (val), op0, code, op1);
3192 }
3193
3194 /* Returns a constant upper bound on the value of expression OP0 CODE OP1,
3195 whose type is TYPE. The expression is considered to be unsigned. If
3196 its type is signed, its value must be nonnegative. */
3197
3198 static widest_int
derive_constant_upper_bound_ops(tree type,tree op0,enum tree_code code,tree op1)3199 derive_constant_upper_bound_ops (tree type, tree op0,
3200 enum tree_code code, tree op1)
3201 {
3202 tree subtype, maxt;
3203 widest_int bnd, max, cst;
3204 gimple *stmt;
3205
3206 if (INTEGRAL_TYPE_P (type))
3207 maxt = TYPE_MAX_VALUE (type);
3208 else
3209 maxt = upper_bound_in_type (type, type);
3210
3211 max = wi::to_widest (maxt);
3212
3213 switch (code)
3214 {
3215 case INTEGER_CST:
3216 return wi::to_widest (op0);
3217
3218 CASE_CONVERT:
3219 subtype = TREE_TYPE (op0);
3220 if (!TYPE_UNSIGNED (subtype)
3221 /* If TYPE is also signed, the fact that VAL is nonnegative implies
3222 that OP0 is nonnegative. */
3223 && TYPE_UNSIGNED (type)
3224 && !tree_expr_nonnegative_p (op0))
3225 {
3226 /* If we cannot prove that the casted expression is nonnegative,
3227 we cannot establish more useful upper bound than the precision
3228 of the type gives us. */
3229 return max;
3230 }
3231
3232 /* We now know that op0 is an nonnegative value. Try deriving an upper
3233 bound for it. */
3234 bnd = derive_constant_upper_bound (op0);
3235
3236 /* If the bound does not fit in TYPE, max. value of TYPE could be
3237 attained. */
3238 if (wi::ltu_p (max, bnd))
3239 return max;
3240
3241 return bnd;
3242
3243 case PLUS_EXPR:
3244 case POINTER_PLUS_EXPR:
3245 case MINUS_EXPR:
3246 if (TREE_CODE (op1) != INTEGER_CST
3247 || !tree_expr_nonnegative_p (op0))
3248 return max;
3249
3250 /* Canonicalize to OP0 - CST. Consider CST to be signed, in order to
3251 choose the most logical way how to treat this constant regardless
3252 of the signedness of the type. */
3253 cst = wi::sext (wi::to_widest (op1), TYPE_PRECISION (type));
3254 if (code != MINUS_EXPR)
3255 cst = -cst;
3256
3257 bnd = derive_constant_upper_bound (op0);
3258
3259 if (wi::neg_p (cst))
3260 {
3261 cst = -cst;
3262 /* Avoid CST == 0x80000... */
3263 if (wi::neg_p (cst))
3264 return max;
3265
3266 /* OP0 + CST. We need to check that
3267 BND <= MAX (type) - CST. */
3268
3269 widest_int mmax = max - cst;
3270 if (wi::leu_p (bnd, mmax))
3271 return max;
3272
3273 return bnd + cst;
3274 }
3275 else
3276 {
3277 /* OP0 - CST, where CST >= 0.
3278
3279 If TYPE is signed, we have already verified that OP0 >= 0, and we
3280 know that the result is nonnegative. This implies that
3281 VAL <= BND - CST.
3282
3283 If TYPE is unsigned, we must additionally know that OP0 >= CST,
3284 otherwise the operation underflows.
3285 */
3286
3287 /* This should only happen if the type is unsigned; however, for
3288 buggy programs that use overflowing signed arithmetics even with
3289 -fno-wrapv, this condition may also be true for signed values. */
3290 if (wi::ltu_p (bnd, cst))
3291 return max;
3292
3293 if (TYPE_UNSIGNED (type))
3294 {
3295 tree tem = fold_binary (GE_EXPR, boolean_type_node, op0,
3296 wide_int_to_tree (type, cst));
3297 if (!tem || integer_nonzerop (tem))
3298 return max;
3299 }
3300
3301 bnd -= cst;
3302 }
3303
3304 return bnd;
3305
3306 case FLOOR_DIV_EXPR:
3307 case EXACT_DIV_EXPR:
3308 if (TREE_CODE (op1) != INTEGER_CST
3309 || tree_int_cst_sign_bit (op1))
3310 return max;
3311
3312 bnd = derive_constant_upper_bound (op0);
3313 return wi::udiv_floor (bnd, wi::to_widest (op1));
3314
3315 case BIT_AND_EXPR:
3316 if (TREE_CODE (op1) != INTEGER_CST
3317 || tree_int_cst_sign_bit (op1))
3318 return max;
3319 return wi::to_widest (op1);
3320
3321 case SSA_NAME:
3322 stmt = SSA_NAME_DEF_STMT (op0);
3323 if (gimple_code (stmt) != GIMPLE_ASSIGN
3324 || gimple_assign_lhs (stmt) != op0)
3325 return max;
3326 return derive_constant_upper_bound_assign (stmt);
3327
3328 default:
3329 return max;
3330 }
3331 }
3332
3333 /* Emit a -Waggressive-loop-optimizations warning if needed. */
3334
3335 static void
do_warn_aggressive_loop_optimizations(class loop * loop,widest_int i_bound,gimple * stmt)3336 do_warn_aggressive_loop_optimizations (class loop *loop,
3337 widest_int i_bound, gimple *stmt)
3338 {
3339 /* Don't warn if the loop doesn't have known constant bound. */
3340 if (!loop->nb_iterations
3341 || TREE_CODE (loop->nb_iterations) != INTEGER_CST
3342 || !warn_aggressive_loop_optimizations
3343 /* To avoid warning multiple times for the same loop,
3344 only start warning when we preserve loops. */
3345 || (cfun->curr_properties & PROP_loops) == 0
3346 /* Only warn once per loop. */
3347 || loop->warned_aggressive_loop_optimizations
3348 /* Only warn if undefined behavior gives us lower estimate than the
3349 known constant bound. */
3350 || wi::cmpu (i_bound, wi::to_widest (loop->nb_iterations)) >= 0
3351 /* And undefined behavior happens unconditionally. */
3352 || !dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (stmt)))
3353 return;
3354
3355 edge e = single_exit (loop);
3356 if (e == NULL)
3357 return;
3358
3359 gimple *estmt = last_stmt (e->src);
3360 char buf[WIDE_INT_PRINT_BUFFER_SIZE];
3361 print_dec (i_bound, buf, TYPE_UNSIGNED (TREE_TYPE (loop->nb_iterations))
3362 ? UNSIGNED : SIGNED);
3363 auto_diagnostic_group d;
3364 if (warning_at (gimple_location (stmt), OPT_Waggressive_loop_optimizations,
3365 "iteration %s invokes undefined behavior", buf))
3366 inform (gimple_location (estmt), "within this loop");
3367 loop->warned_aggressive_loop_optimizations = true;
3368 }
3369
3370 /* Records that AT_STMT is executed at most BOUND + 1 times in LOOP. IS_EXIT
3371 is true if the loop is exited immediately after STMT, and this exit
3372 is taken at last when the STMT is executed BOUND + 1 times.
3373 REALISTIC is true if BOUND is expected to be close to the real number
3374 of iterations. UPPER is true if we are sure the loop iterates at most
3375 BOUND times. I_BOUND is a widest_int upper estimate on BOUND. */
3376
3377 static void
record_estimate(class loop * loop,tree bound,const widest_int & i_bound,gimple * at_stmt,bool is_exit,bool realistic,bool upper)3378 record_estimate (class loop *loop, tree bound, const widest_int &i_bound,
3379 gimple *at_stmt, bool is_exit, bool realistic, bool upper)
3380 {
3381 widest_int delta;
3382
3383 if (dump_file && (dump_flags & TDF_DETAILS))
3384 {
3385 fprintf (dump_file, "Statement %s", is_exit ? "(exit)" : "");
3386 print_gimple_stmt (dump_file, at_stmt, 0, TDF_SLIM);
3387 fprintf (dump_file, " is %sexecuted at most ",
3388 upper ? "" : "probably ");
3389 print_generic_expr (dump_file, bound, TDF_SLIM);
3390 fprintf (dump_file, " (bounded by ");
3391 print_decu (i_bound, dump_file);
3392 fprintf (dump_file, ") + 1 times in loop %d.\n", loop->num);
3393 }
3394
3395 /* If the I_BOUND is just an estimate of BOUND, it rarely is close to the
3396 real number of iterations. */
3397 if (TREE_CODE (bound) != INTEGER_CST)
3398 realistic = false;
3399 else
3400 gcc_checking_assert (i_bound == wi::to_widest (bound));
3401
3402 /* If we have a guaranteed upper bound, record it in the appropriate
3403 list, unless this is an !is_exit bound (i.e. undefined behavior in
3404 at_stmt) in a loop with known constant number of iterations. */
3405 if (upper
3406 && (is_exit
3407 || loop->nb_iterations == NULL_TREE
3408 || TREE_CODE (loop->nb_iterations) != INTEGER_CST))
3409 {
3410 class nb_iter_bound *elt = ggc_alloc<nb_iter_bound> ();
3411
3412 elt->bound = i_bound;
3413 elt->stmt = at_stmt;
3414 elt->is_exit = is_exit;
3415 elt->next = loop->bounds;
3416 loop->bounds = elt;
3417 }
3418
3419 /* If statement is executed on every path to the loop latch, we can directly
3420 infer the upper bound on the # of iterations of the loop. */
3421 if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (at_stmt)))
3422 upper = false;
3423
3424 /* Update the number of iteration estimates according to the bound.
3425 If at_stmt is an exit then the loop latch is executed at most BOUND times,
3426 otherwise it can be executed BOUND + 1 times. We will lower the estimate
3427 later if such statement must be executed on last iteration */
3428 if (is_exit)
3429 delta = 0;
3430 else
3431 delta = 1;
3432 widest_int new_i_bound = i_bound + delta;
3433
3434 /* If an overflow occurred, ignore the result. */
3435 if (wi::ltu_p (new_i_bound, delta))
3436 return;
3437
3438 if (upper && !is_exit)
3439 do_warn_aggressive_loop_optimizations (loop, new_i_bound, at_stmt);
3440 record_niter_bound (loop, new_i_bound, realistic, upper);
3441 }
3442
3443 /* Records the control iv analyzed in NITER for LOOP if the iv is valid
3444 and doesn't overflow. */
3445
3446 static void
record_control_iv(class loop * loop,class tree_niter_desc * niter)3447 record_control_iv (class loop *loop, class tree_niter_desc *niter)
3448 {
3449 struct control_iv *iv;
3450
3451 if (!niter->control.base || !niter->control.step)
3452 return;
3453
3454 if (!integer_onep (niter->assumptions) || !niter->control.no_overflow)
3455 return;
3456
3457 iv = ggc_alloc<control_iv> ();
3458 iv->base = niter->control.base;
3459 iv->step = niter->control.step;
3460 iv->next = loop->control_ivs;
3461 loop->control_ivs = iv;
3462
3463 return;
3464 }
3465
3466 /* This function returns TRUE if below conditions are satisfied:
3467 1) VAR is SSA variable.
3468 2) VAR is an IV:{base, step} in its defining loop.
3469 3) IV doesn't overflow.
3470 4) Both base and step are integer constants.
3471 5) Base is the MIN/MAX value depends on IS_MIN.
3472 Store value of base to INIT correspondingly. */
3473
3474 static bool
get_cst_init_from_scev(tree var,wide_int * init,bool is_min)3475 get_cst_init_from_scev (tree var, wide_int *init, bool is_min)
3476 {
3477 if (TREE_CODE (var) != SSA_NAME)
3478 return false;
3479
3480 gimple *def_stmt = SSA_NAME_DEF_STMT (var);
3481 class loop *loop = loop_containing_stmt (def_stmt);
3482
3483 if (loop == NULL)
3484 return false;
3485
3486 affine_iv iv;
3487 if (!simple_iv (loop, loop, var, &iv, false))
3488 return false;
3489
3490 if (!iv.no_overflow)
3491 return false;
3492
3493 if (TREE_CODE (iv.base) != INTEGER_CST || TREE_CODE (iv.step) != INTEGER_CST)
3494 return false;
3495
3496 if (is_min == tree_int_cst_sign_bit (iv.step))
3497 return false;
3498
3499 *init = wi::to_wide (iv.base);
3500 return true;
3501 }
3502
3503 /* Record the estimate on number of iterations of LOOP based on the fact that
3504 the induction variable BASE + STEP * i evaluated in STMT does not wrap and
3505 its values belong to the range <LOW, HIGH>. REALISTIC is true if the
3506 estimated number of iterations is expected to be close to the real one.
3507 UPPER is true if we are sure the induction variable does not wrap. */
3508
3509 static void
record_nonwrapping_iv(class loop * loop,tree base,tree step,gimple * stmt,tree low,tree high,bool realistic,bool upper)3510 record_nonwrapping_iv (class loop *loop, tree base, tree step, gimple *stmt,
3511 tree low, tree high, bool realistic, bool upper)
3512 {
3513 tree niter_bound, extreme, delta;
3514 tree type = TREE_TYPE (base), unsigned_type;
3515 tree orig_base = base;
3516
3517 if (TREE_CODE (step) != INTEGER_CST || integer_zerop (step))
3518 return;
3519
3520 if (dump_file && (dump_flags & TDF_DETAILS))
3521 {
3522 fprintf (dump_file, "Induction variable (");
3523 print_generic_expr (dump_file, TREE_TYPE (base), TDF_SLIM);
3524 fprintf (dump_file, ") ");
3525 print_generic_expr (dump_file, base, TDF_SLIM);
3526 fprintf (dump_file, " + ");
3527 print_generic_expr (dump_file, step, TDF_SLIM);
3528 fprintf (dump_file, " * iteration does not wrap in statement ");
3529 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
3530 fprintf (dump_file, " in loop %d.\n", loop->num);
3531 }
3532
3533 unsigned_type = unsigned_type_for (type);
3534 base = fold_convert (unsigned_type, base);
3535 step = fold_convert (unsigned_type, step);
3536
3537 if (tree_int_cst_sign_bit (step))
3538 {
3539 wide_int min, max;
3540 extreme = fold_convert (unsigned_type, low);
3541 if (TREE_CODE (orig_base) == SSA_NAME
3542 && TREE_CODE (high) == INTEGER_CST
3543 && INTEGRAL_TYPE_P (TREE_TYPE (orig_base))
3544 && (get_range_info (orig_base, &min, &max) == VR_RANGE
3545 || get_cst_init_from_scev (orig_base, &max, false))
3546 && wi::gts_p (wi::to_wide (high), max))
3547 base = wide_int_to_tree (unsigned_type, max);
3548 else if (TREE_CODE (base) != INTEGER_CST
3549 && dominated_by_p (CDI_DOMINATORS,
3550 loop->latch, gimple_bb (stmt)))
3551 base = fold_convert (unsigned_type, high);
3552 delta = fold_build2 (MINUS_EXPR, unsigned_type, base, extreme);
3553 step = fold_build1 (NEGATE_EXPR, unsigned_type, step);
3554 }
3555 else
3556 {
3557 wide_int min, max;
3558 extreme = fold_convert (unsigned_type, high);
3559 if (TREE_CODE (orig_base) == SSA_NAME
3560 && TREE_CODE (low) == INTEGER_CST
3561 && INTEGRAL_TYPE_P (TREE_TYPE (orig_base))
3562 && (get_range_info (orig_base, &min, &max) == VR_RANGE
3563 || get_cst_init_from_scev (orig_base, &min, true))
3564 && wi::gts_p (min, wi::to_wide (low)))
3565 base = wide_int_to_tree (unsigned_type, min);
3566 else if (TREE_CODE (base) != INTEGER_CST
3567 && dominated_by_p (CDI_DOMINATORS,
3568 loop->latch, gimple_bb (stmt)))
3569 base = fold_convert (unsigned_type, low);
3570 delta = fold_build2 (MINUS_EXPR, unsigned_type, extreme, base);
3571 }
3572
3573 /* STMT is executed at most NITER_BOUND + 1 times, since otherwise the value
3574 would get out of the range. */
3575 niter_bound = fold_build2 (FLOOR_DIV_EXPR, unsigned_type, delta, step);
3576 widest_int max = derive_constant_upper_bound (niter_bound);
3577 record_estimate (loop, niter_bound, max, stmt, false, realistic, upper);
3578 }
3579
3580 /* Determine information about number of iterations a LOOP from the index
3581 IDX of a data reference accessed in STMT. RELIABLE is true if STMT is
3582 guaranteed to be executed in every iteration of LOOP. Callback for
3583 for_each_index. */
3584
3585 struct ilb_data
3586 {
3587 class loop *loop;
3588 gimple *stmt;
3589 };
3590
3591 static bool
idx_infer_loop_bounds(tree base,tree * idx,void * dta)3592 idx_infer_loop_bounds (tree base, tree *idx, void *dta)
3593 {
3594 struct ilb_data *data = (struct ilb_data *) dta;
3595 tree ev, init, step;
3596 tree low, high, type, next;
3597 bool sign, upper = true, at_end = false;
3598 class loop *loop = data->loop;
3599
3600 if (TREE_CODE (base) != ARRAY_REF)
3601 return true;
3602
3603 /* For arrays at the end of the structure, we are not guaranteed that they
3604 do not really extend over their declared size. However, for arrays of
3605 size greater than one, this is unlikely to be intended. */
3606 if (array_at_struct_end_p (base))
3607 {
3608 at_end = true;
3609 upper = false;
3610 }
3611
3612 class loop *dloop = loop_containing_stmt (data->stmt);
3613 if (!dloop)
3614 return true;
3615
3616 ev = analyze_scalar_evolution (dloop, *idx);
3617 ev = instantiate_parameters (loop, ev);
3618 init = initial_condition (ev);
3619 step = evolution_part_in_loop_num (ev, loop->num);
3620
3621 if (!init
3622 || !step
3623 || TREE_CODE (step) != INTEGER_CST
3624 || integer_zerop (step)
3625 || tree_contains_chrecs (init, NULL)
3626 || chrec_contains_symbols_defined_in_loop (init, loop->num))
3627 return true;
3628
3629 low = array_ref_low_bound (base);
3630 high = array_ref_up_bound (base);
3631
3632 /* The case of nonconstant bounds could be handled, but it would be
3633 complicated. */
3634 if (TREE_CODE (low) != INTEGER_CST
3635 || !high
3636 || TREE_CODE (high) != INTEGER_CST)
3637 return true;
3638 sign = tree_int_cst_sign_bit (step);
3639 type = TREE_TYPE (step);
3640
3641 /* The array of length 1 at the end of a structure most likely extends
3642 beyond its bounds. */
3643 if (at_end
3644 && operand_equal_p (low, high, 0))
3645 return true;
3646
3647 /* In case the relevant bound of the array does not fit in type, or
3648 it does, but bound + step (in type) still belongs into the range of the
3649 array, the index may wrap and still stay within the range of the array
3650 (consider e.g. if the array is indexed by the full range of
3651 unsigned char).
3652
3653 To make things simpler, we require both bounds to fit into type, although
3654 there are cases where this would not be strictly necessary. */
3655 if (!int_fits_type_p (high, type)
3656 || !int_fits_type_p (low, type))
3657 return true;
3658 low = fold_convert (type, low);
3659 high = fold_convert (type, high);
3660
3661 if (sign)
3662 next = fold_binary (PLUS_EXPR, type, low, step);
3663 else
3664 next = fold_binary (PLUS_EXPR, type, high, step);
3665
3666 if (tree_int_cst_compare (low, next) <= 0
3667 && tree_int_cst_compare (next, high) <= 0)
3668 return true;
3669
3670 /* If access is not executed on every iteration, we must ensure that overlow
3671 may not make the access valid later. */
3672 if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (data->stmt))
3673 && scev_probably_wraps_p (NULL_TREE,
3674 initial_condition_in_loop_num (ev, loop->num),
3675 step, data->stmt, loop, true))
3676 upper = false;
3677
3678 record_nonwrapping_iv (loop, init, step, data->stmt, low, high, false, upper);
3679 return true;
3680 }
3681
3682 /* Determine information about number of iterations a LOOP from the bounds
3683 of arrays in the data reference REF accessed in STMT. RELIABLE is true if
3684 STMT is guaranteed to be executed in every iteration of LOOP.*/
3685
3686 static void
infer_loop_bounds_from_ref(class loop * loop,gimple * stmt,tree ref)3687 infer_loop_bounds_from_ref (class loop *loop, gimple *stmt, tree ref)
3688 {
3689 struct ilb_data data;
3690
3691 data.loop = loop;
3692 data.stmt = stmt;
3693 for_each_index (&ref, idx_infer_loop_bounds, &data);
3694 }
3695
3696 /* Determine information about number of iterations of a LOOP from the way
3697 arrays are used in STMT. RELIABLE is true if STMT is guaranteed to be
3698 executed in every iteration of LOOP. */
3699
3700 static void
infer_loop_bounds_from_array(class loop * loop,gimple * stmt)3701 infer_loop_bounds_from_array (class loop *loop, gimple *stmt)
3702 {
3703 if (is_gimple_assign (stmt))
3704 {
3705 tree op0 = gimple_assign_lhs (stmt);
3706 tree op1 = gimple_assign_rhs1 (stmt);
3707
3708 /* For each memory access, analyze its access function
3709 and record a bound on the loop iteration domain. */
3710 if (REFERENCE_CLASS_P (op0))
3711 infer_loop_bounds_from_ref (loop, stmt, op0);
3712
3713 if (REFERENCE_CLASS_P (op1))
3714 infer_loop_bounds_from_ref (loop, stmt, op1);
3715 }
3716 else if (is_gimple_call (stmt))
3717 {
3718 tree arg, lhs;
3719 unsigned i, n = gimple_call_num_args (stmt);
3720
3721 lhs = gimple_call_lhs (stmt);
3722 if (lhs && REFERENCE_CLASS_P (lhs))
3723 infer_loop_bounds_from_ref (loop, stmt, lhs);
3724
3725 for (i = 0; i < n; i++)
3726 {
3727 arg = gimple_call_arg (stmt, i);
3728 if (REFERENCE_CLASS_P (arg))
3729 infer_loop_bounds_from_ref (loop, stmt, arg);
3730 }
3731 }
3732 }
3733
3734 /* Determine information about number of iterations of a LOOP from the fact
3735 that pointer arithmetics in STMT does not overflow. */
3736
3737 static void
infer_loop_bounds_from_pointer_arith(class loop * loop,gimple * stmt)3738 infer_loop_bounds_from_pointer_arith (class loop *loop, gimple *stmt)
3739 {
3740 tree def, base, step, scev, type, low, high;
3741 tree var, ptr;
3742
3743 if (!is_gimple_assign (stmt)
3744 || gimple_assign_rhs_code (stmt) != POINTER_PLUS_EXPR)
3745 return;
3746
3747 def = gimple_assign_lhs (stmt);
3748 if (TREE_CODE (def) != SSA_NAME)
3749 return;
3750
3751 type = TREE_TYPE (def);
3752 if (!nowrap_type_p (type))
3753 return;
3754
3755 ptr = gimple_assign_rhs1 (stmt);
3756 if (!expr_invariant_in_loop_p (loop, ptr))
3757 return;
3758
3759 var = gimple_assign_rhs2 (stmt);
3760 if (TYPE_PRECISION (type) != TYPE_PRECISION (TREE_TYPE (var)))
3761 return;
3762
3763 class loop *uloop = loop_containing_stmt (stmt);
3764 scev = instantiate_parameters (loop, analyze_scalar_evolution (uloop, def));
3765 if (chrec_contains_undetermined (scev))
3766 return;
3767
3768 base = initial_condition_in_loop_num (scev, loop->num);
3769 step = evolution_part_in_loop_num (scev, loop->num);
3770
3771 if (!base || !step
3772 || TREE_CODE (step) != INTEGER_CST
3773 || tree_contains_chrecs (base, NULL)
3774 || chrec_contains_symbols_defined_in_loop (base, loop->num))
3775 return;
3776
3777 low = lower_bound_in_type (type, type);
3778 high = upper_bound_in_type (type, type);
3779
3780 /* In C, pointer arithmetic p + 1 cannot use a NULL pointer, and p - 1 cannot
3781 produce a NULL pointer. The contrary would mean NULL points to an object,
3782 while NULL is supposed to compare unequal with the address of all objects.
3783 Furthermore, p + 1 cannot produce a NULL pointer and p - 1 cannot use a
3784 NULL pointer since that would mean wrapping, which we assume here not to
3785 happen. So, we can exclude NULL from the valid range of pointer
3786 arithmetic. */
3787 if (flag_delete_null_pointer_checks && int_cst_value (low) == 0)
3788 low = build_int_cstu (TREE_TYPE (low), TYPE_ALIGN_UNIT (TREE_TYPE (type)));
3789
3790 record_nonwrapping_iv (loop, base, step, stmt, low, high, false, true);
3791 }
3792
3793 /* Determine information about number of iterations of a LOOP from the fact
3794 that signed arithmetics in STMT does not overflow. */
3795
3796 static void
infer_loop_bounds_from_signedness(class loop * loop,gimple * stmt)3797 infer_loop_bounds_from_signedness (class loop *loop, gimple *stmt)
3798 {
3799 tree def, base, step, scev, type, low, high;
3800
3801 if (gimple_code (stmt) != GIMPLE_ASSIGN)
3802 return;
3803
3804 def = gimple_assign_lhs (stmt);
3805
3806 if (TREE_CODE (def) != SSA_NAME)
3807 return;
3808
3809 type = TREE_TYPE (def);
3810 if (!INTEGRAL_TYPE_P (type)
3811 || !TYPE_OVERFLOW_UNDEFINED (type))
3812 return;
3813
3814 scev = instantiate_parameters (loop, analyze_scalar_evolution (loop, def));
3815 if (chrec_contains_undetermined (scev))
3816 return;
3817
3818 base = initial_condition_in_loop_num (scev, loop->num);
3819 step = evolution_part_in_loop_num (scev, loop->num);
3820
3821 if (!base || !step
3822 || TREE_CODE (step) != INTEGER_CST
3823 || tree_contains_chrecs (base, NULL)
3824 || chrec_contains_symbols_defined_in_loop (base, loop->num))
3825 return;
3826
3827 low = lower_bound_in_type (type, type);
3828 high = upper_bound_in_type (type, type);
3829 wide_int minv, maxv;
3830 if (get_range_info (def, &minv, &maxv) == VR_RANGE)
3831 {
3832 low = wide_int_to_tree (type, minv);
3833 high = wide_int_to_tree (type, maxv);
3834 }
3835
3836 record_nonwrapping_iv (loop, base, step, stmt, low, high, false, true);
3837 }
3838
3839 /* The following analyzers are extracting informations on the bounds
3840 of LOOP from the following undefined behaviors:
3841
3842 - data references should not access elements over the statically
3843 allocated size,
3844
3845 - signed variables should not overflow when flag_wrapv is not set.
3846 */
3847
3848 static void
infer_loop_bounds_from_undefined(class loop * loop,basic_block * bbs)3849 infer_loop_bounds_from_undefined (class loop *loop, basic_block *bbs)
3850 {
3851 unsigned i;
3852 gimple_stmt_iterator bsi;
3853 basic_block bb;
3854 bool reliable;
3855
3856 for (i = 0; i < loop->num_nodes; i++)
3857 {
3858 bb = bbs[i];
3859
3860 /* If BB is not executed in each iteration of the loop, we cannot
3861 use the operations in it to infer reliable upper bound on the
3862 # of iterations of the loop. However, we can use it as a guess.
3863 Reliable guesses come only from array bounds. */
3864 reliable = dominated_by_p (CDI_DOMINATORS, loop->latch, bb);
3865
3866 for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
3867 {
3868 gimple *stmt = gsi_stmt (bsi);
3869
3870 infer_loop_bounds_from_array (loop, stmt);
3871
3872 if (reliable)
3873 {
3874 infer_loop_bounds_from_signedness (loop, stmt);
3875 infer_loop_bounds_from_pointer_arith (loop, stmt);
3876 }
3877 }
3878
3879 }
3880 }
3881
3882 /* Compare wide ints, callback for qsort. */
3883
3884 static int
wide_int_cmp(const void * p1,const void * p2)3885 wide_int_cmp (const void *p1, const void *p2)
3886 {
3887 const widest_int *d1 = (const widest_int *) p1;
3888 const widest_int *d2 = (const widest_int *) p2;
3889 return wi::cmpu (*d1, *d2);
3890 }
3891
3892 /* Return index of BOUND in BOUNDS array sorted in increasing order.
3893 Lookup by binary search. */
3894
3895 static int
bound_index(vec<widest_int> bounds,const widest_int & bound)3896 bound_index (vec<widest_int> bounds, const widest_int &bound)
3897 {
3898 unsigned int end = bounds.length ();
3899 unsigned int begin = 0;
3900
3901 /* Find a matching index by means of a binary search. */
3902 while (begin != end)
3903 {
3904 unsigned int middle = (begin + end) / 2;
3905 widest_int index = bounds[middle];
3906
3907 if (index == bound)
3908 return middle;
3909 else if (wi::ltu_p (index, bound))
3910 begin = middle + 1;
3911 else
3912 end = middle;
3913 }
3914 gcc_unreachable ();
3915 }
3916
3917 /* We recorded loop bounds only for statements dominating loop latch (and thus
3918 executed each loop iteration). If there are any bounds on statements not
3919 dominating the loop latch we can improve the estimate by walking the loop
3920 body and seeing if every path from loop header to loop latch contains
3921 some bounded statement. */
3922
3923 static void
discover_iteration_bound_by_body_walk(class loop * loop)3924 discover_iteration_bound_by_body_walk (class loop *loop)
3925 {
3926 class nb_iter_bound *elt;
3927 auto_vec<widest_int> bounds;
3928 vec<vec<basic_block> > queues = vNULL;
3929 vec<basic_block> queue = vNULL;
3930 ptrdiff_t queue_index;
3931 ptrdiff_t latch_index = 0;
3932
3933 /* Discover what bounds may interest us. */
3934 for (elt = loop->bounds; elt; elt = elt->next)
3935 {
3936 widest_int bound = elt->bound;
3937
3938 /* Exit terminates loop at given iteration, while non-exits produce undefined
3939 effect on the next iteration. */
3940 if (!elt->is_exit)
3941 {
3942 bound += 1;
3943 /* If an overflow occurred, ignore the result. */
3944 if (bound == 0)
3945 continue;
3946 }
3947
3948 if (!loop->any_upper_bound
3949 || wi::ltu_p (bound, loop->nb_iterations_upper_bound))
3950 bounds.safe_push (bound);
3951 }
3952
3953 /* Exit early if there is nothing to do. */
3954 if (!bounds.exists ())
3955 return;
3956
3957 if (dump_file && (dump_flags & TDF_DETAILS))
3958 fprintf (dump_file, " Trying to walk loop body to reduce the bound.\n");
3959
3960 /* Sort the bounds in decreasing order. */
3961 bounds.qsort (wide_int_cmp);
3962
3963 /* For every basic block record the lowest bound that is guaranteed to
3964 terminate the loop. */
3965
3966 hash_map<basic_block, ptrdiff_t> bb_bounds;
3967 for (elt = loop->bounds; elt; elt = elt->next)
3968 {
3969 widest_int bound = elt->bound;
3970 if (!elt->is_exit)
3971 {
3972 bound += 1;
3973 /* If an overflow occurred, ignore the result. */
3974 if (bound == 0)
3975 continue;
3976 }
3977
3978 if (!loop->any_upper_bound
3979 || wi::ltu_p (bound, loop->nb_iterations_upper_bound))
3980 {
3981 ptrdiff_t index = bound_index (bounds, bound);
3982 ptrdiff_t *entry = bb_bounds.get (gimple_bb (elt->stmt));
3983 if (!entry)
3984 bb_bounds.put (gimple_bb (elt->stmt), index);
3985 else if ((ptrdiff_t)*entry > index)
3986 *entry = index;
3987 }
3988 }
3989
3990 hash_map<basic_block, ptrdiff_t> block_priority;
3991
3992 /* Perform shortest path discovery loop->header ... loop->latch.
3993
3994 The "distance" is given by the smallest loop bound of basic block
3995 present in the path and we look for path with largest smallest bound
3996 on it.
3997
3998 To avoid the need for fibonacci heap on double ints we simply compress
3999 double ints into indexes to BOUNDS array and then represent the queue
4000 as arrays of queues for every index.
4001 Index of BOUNDS.length() means that the execution of given BB has
4002 no bounds determined.
4003
4004 VISITED is a pointer map translating basic block into smallest index
4005 it was inserted into the priority queue with. */
4006 latch_index = -1;
4007
4008 /* Start walk in loop header with index set to infinite bound. */
4009 queue_index = bounds.length ();
4010 queues.safe_grow_cleared (queue_index + 1);
4011 queue.safe_push (loop->header);
4012 queues[queue_index] = queue;
4013 block_priority.put (loop->header, queue_index);
4014
4015 for (; queue_index >= 0; queue_index--)
4016 {
4017 if (latch_index < queue_index)
4018 {
4019 while (queues[queue_index].length ())
4020 {
4021 basic_block bb;
4022 ptrdiff_t bound_index = queue_index;
4023 edge e;
4024 edge_iterator ei;
4025
4026 queue = queues[queue_index];
4027 bb = queue.pop ();
4028
4029 /* OK, we later inserted the BB with lower priority, skip it. */
4030 if (*block_priority.get (bb) > queue_index)
4031 continue;
4032
4033 /* See if we can improve the bound. */
4034 ptrdiff_t *entry = bb_bounds.get (bb);
4035 if (entry && *entry < bound_index)
4036 bound_index = *entry;
4037
4038 /* Insert succesors into the queue, watch for latch edge
4039 and record greatest index we saw. */
4040 FOR_EACH_EDGE (e, ei, bb->succs)
4041 {
4042 bool insert = false;
4043
4044 if (loop_exit_edge_p (loop, e))
4045 continue;
4046
4047 if (e == loop_latch_edge (loop)
4048 && latch_index < bound_index)
4049 latch_index = bound_index;
4050 else if (!(entry = block_priority.get (e->dest)))
4051 {
4052 insert = true;
4053 block_priority.put (e->dest, bound_index);
4054 }
4055 else if (*entry < bound_index)
4056 {
4057 insert = true;
4058 *entry = bound_index;
4059 }
4060
4061 if (insert)
4062 queues[bound_index].safe_push (e->dest);
4063 }
4064 }
4065 }
4066 queues[queue_index].release ();
4067 }
4068
4069 gcc_assert (latch_index >= 0);
4070 if ((unsigned)latch_index < bounds.length ())
4071 {
4072 if (dump_file && (dump_flags & TDF_DETAILS))
4073 {
4074 fprintf (dump_file, "Found better loop bound ");
4075 print_decu (bounds[latch_index], dump_file);
4076 fprintf (dump_file, "\n");
4077 }
4078 record_niter_bound (loop, bounds[latch_index], false, true);
4079 }
4080
4081 queues.release ();
4082 }
4083
4084 /* See if every path cross the loop goes through a statement that is known
4085 to not execute at the last iteration. In that case we can decrese iteration
4086 count by 1. */
4087
4088 static void
maybe_lower_iteration_bound(class loop * loop)4089 maybe_lower_iteration_bound (class loop *loop)
4090 {
4091 hash_set<gimple *> *not_executed_last_iteration = NULL;
4092 class nb_iter_bound *elt;
4093 bool found_exit = false;
4094 auto_vec<basic_block> queue;
4095 bitmap visited;
4096
4097 /* Collect all statements with interesting (i.e. lower than
4098 nb_iterations_upper_bound) bound on them.
4099
4100 TODO: Due to the way record_estimate choose estimates to store, the bounds
4101 will be always nb_iterations_upper_bound-1. We can change this to record
4102 also statements not dominating the loop latch and update the walk bellow
4103 to the shortest path algorithm. */
4104 for (elt = loop->bounds; elt; elt = elt->next)
4105 {
4106 if (!elt->is_exit
4107 && wi::ltu_p (elt->bound, loop->nb_iterations_upper_bound))
4108 {
4109 if (!not_executed_last_iteration)
4110 not_executed_last_iteration = new hash_set<gimple *>;
4111 not_executed_last_iteration->add (elt->stmt);
4112 }
4113 }
4114 if (!not_executed_last_iteration)
4115 return;
4116
4117 /* Start DFS walk in the loop header and see if we can reach the
4118 loop latch or any of the exits (including statements with side
4119 effects that may terminate the loop otherwise) without visiting
4120 any of the statements known to have undefined effect on the last
4121 iteration. */
4122 queue.safe_push (loop->header);
4123 visited = BITMAP_ALLOC (NULL);
4124 bitmap_set_bit (visited, loop->header->index);
4125 found_exit = false;
4126
4127 do
4128 {
4129 basic_block bb = queue.pop ();
4130 gimple_stmt_iterator gsi;
4131 bool stmt_found = false;
4132
4133 /* Loop for possible exits and statements bounding the execution. */
4134 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
4135 {
4136 gimple *stmt = gsi_stmt (gsi);
4137 if (not_executed_last_iteration->contains (stmt))
4138 {
4139 stmt_found = true;
4140 break;
4141 }
4142 if (gimple_has_side_effects (stmt))
4143 {
4144 found_exit = true;
4145 break;
4146 }
4147 }
4148 if (found_exit)
4149 break;
4150
4151 /* If no bounding statement is found, continue the walk. */
4152 if (!stmt_found)
4153 {
4154 edge e;
4155 edge_iterator ei;
4156
4157 FOR_EACH_EDGE (e, ei, bb->succs)
4158 {
4159 if (loop_exit_edge_p (loop, e)
4160 || e == loop_latch_edge (loop))
4161 {
4162 found_exit = true;
4163 break;
4164 }
4165 if (bitmap_set_bit (visited, e->dest->index))
4166 queue.safe_push (e->dest);
4167 }
4168 }
4169 }
4170 while (queue.length () && !found_exit);
4171
4172 /* If every path through the loop reach bounding statement before exit,
4173 then we know the last iteration of the loop will have undefined effect
4174 and we can decrease number of iterations. */
4175
4176 if (!found_exit)
4177 {
4178 if (dump_file && (dump_flags & TDF_DETAILS))
4179 fprintf (dump_file, "Reducing loop iteration estimate by 1; "
4180 "undefined statement must be executed at the last iteration.\n");
4181 record_niter_bound (loop, loop->nb_iterations_upper_bound - 1,
4182 false, true);
4183 }
4184
4185 BITMAP_FREE (visited);
4186 delete not_executed_last_iteration;
4187 }
4188
4189 /* Get expected upper bound for number of loop iterations for
4190 BUILT_IN_EXPECT_WITH_PROBABILITY for a condition COND. */
4191
4192 static tree
get_upper_bound_based_on_builtin_expr_with_prob(gcond * cond)4193 get_upper_bound_based_on_builtin_expr_with_prob (gcond *cond)
4194 {
4195 if (cond == NULL)
4196 return NULL_TREE;
4197
4198 tree lhs = gimple_cond_lhs (cond);
4199 if (TREE_CODE (lhs) != SSA_NAME)
4200 return NULL_TREE;
4201
4202 gimple *stmt = SSA_NAME_DEF_STMT (gimple_cond_lhs (cond));
4203 gcall *def = dyn_cast<gcall *> (stmt);
4204 if (def == NULL)
4205 return NULL_TREE;
4206
4207 tree decl = gimple_call_fndecl (def);
4208 if (!decl
4209 || !fndecl_built_in_p (decl, BUILT_IN_EXPECT_WITH_PROBABILITY)
4210 || gimple_call_num_args (stmt) != 3)
4211 return NULL_TREE;
4212
4213 tree c = gimple_call_arg (def, 1);
4214 tree condt = TREE_TYPE (lhs);
4215 tree res = fold_build2 (gimple_cond_code (cond),
4216 condt, c,
4217 gimple_cond_rhs (cond));
4218 if (TREE_CODE (res) != INTEGER_CST)
4219 return NULL_TREE;
4220
4221
4222 tree prob = gimple_call_arg (def, 2);
4223 tree t = TREE_TYPE (prob);
4224 tree one
4225 = build_real_from_int_cst (t,
4226 integer_one_node);
4227 if (integer_zerop (res))
4228 prob = fold_build2 (MINUS_EXPR, t, one, prob);
4229 tree r = fold_build2 (RDIV_EXPR, t, one, prob);
4230 if (TREE_CODE (r) != REAL_CST)
4231 return NULL_TREE;
4232
4233 HOST_WIDE_INT probi
4234 = real_to_integer (TREE_REAL_CST_PTR (r));
4235 return build_int_cst (condt, probi);
4236 }
4237
4238 /* Records estimates on numbers of iterations of LOOP. If USE_UNDEFINED_P
4239 is true also use estimates derived from undefined behavior. */
4240
4241 void
estimate_numbers_of_iterations(class loop * loop)4242 estimate_numbers_of_iterations (class loop *loop)
4243 {
4244 vec<edge> exits;
4245 tree niter, type;
4246 unsigned i;
4247 class tree_niter_desc niter_desc;
4248 edge ex;
4249 widest_int bound;
4250 edge likely_exit;
4251
4252 /* Give up if we already have tried to compute an estimation. */
4253 if (loop->estimate_state != EST_NOT_COMPUTED)
4254 return;
4255
4256 loop->estimate_state = EST_AVAILABLE;
4257
4258 /* If we have a measured profile, use it to estimate the number of
4259 iterations. Normally this is recorded by branch_prob right after
4260 reading the profile. In case we however found a new loop, record the
4261 information here.
4262
4263 Explicitly check for profile status so we do not report
4264 wrong prediction hitrates for guessed loop iterations heuristics.
4265 Do not recompute already recorded bounds - we ought to be better on
4266 updating iteration bounds than updating profile in general and thus
4267 recomputing iteration bounds later in the compilation process will just
4268 introduce random roundoff errors. */
4269 if (!loop->any_estimate
4270 && loop->header->count.reliable_p ())
4271 {
4272 gcov_type nit = expected_loop_iterations_unbounded (loop);
4273 bound = gcov_type_to_wide_int (nit);
4274 record_niter_bound (loop, bound, true, false);
4275 }
4276
4277 /* Ensure that loop->nb_iterations is computed if possible. If it turns out
4278 to be constant, we avoid undefined behavior implied bounds and instead
4279 diagnose those loops with -Waggressive-loop-optimizations. */
4280 number_of_latch_executions (loop);
4281
4282 basic_block *body = get_loop_body (loop);
4283 exits = get_loop_exit_edges (loop, body);
4284 likely_exit = single_likely_exit (loop, exits);
4285 FOR_EACH_VEC_ELT (exits, i, ex)
4286 {
4287 if (ex == likely_exit)
4288 {
4289 gimple *stmt = last_stmt (ex->src);
4290 if (stmt != NULL)
4291 {
4292 gcond *cond = dyn_cast<gcond *> (stmt);
4293 tree niter_bound
4294 = get_upper_bound_based_on_builtin_expr_with_prob (cond);
4295 if (niter_bound != NULL_TREE)
4296 {
4297 widest_int max = derive_constant_upper_bound (niter_bound);
4298 record_estimate (loop, niter_bound, max, cond,
4299 true, true, false);
4300 }
4301 }
4302 }
4303
4304 if (!number_of_iterations_exit (loop, ex, &niter_desc,
4305 false, false, body))
4306 continue;
4307
4308 niter = niter_desc.niter;
4309 type = TREE_TYPE (niter);
4310 if (TREE_CODE (niter_desc.may_be_zero) != INTEGER_CST)
4311 niter = build3 (COND_EXPR, type, niter_desc.may_be_zero,
4312 build_int_cst (type, 0),
4313 niter);
4314 record_estimate (loop, niter, niter_desc.max,
4315 last_stmt (ex->src),
4316 true, ex == likely_exit, true);
4317 record_control_iv (loop, &niter_desc);
4318 }
4319 exits.release ();
4320
4321 if (flag_aggressive_loop_optimizations)
4322 infer_loop_bounds_from_undefined (loop, body);
4323
4324 discover_iteration_bound_by_body_walk (loop);
4325
4326 maybe_lower_iteration_bound (loop);
4327
4328 /* If we know the exact number of iterations of this loop, try to
4329 not break code with undefined behavior by not recording smaller
4330 maximum number of iterations. */
4331 if (loop->nb_iterations
4332 && TREE_CODE (loop->nb_iterations) == INTEGER_CST)
4333 {
4334 loop->any_upper_bound = true;
4335 loop->nb_iterations_upper_bound = wi::to_widest (loop->nb_iterations);
4336 }
4337 }
4338
4339 /* Sets NIT to the estimated number of executions of the latch of the
4340 LOOP. If CONSERVATIVE is true, we must be sure that NIT is at least as
4341 large as the number of iterations. If we have no reliable estimate,
4342 the function returns false, otherwise returns true. */
4343
4344 bool
estimated_loop_iterations(class loop * loop,widest_int * nit)4345 estimated_loop_iterations (class loop *loop, widest_int *nit)
4346 {
4347 /* When SCEV information is available, try to update loop iterations
4348 estimate. Otherwise just return whatever we recorded earlier. */
4349 if (scev_initialized_p ())
4350 estimate_numbers_of_iterations (loop);
4351
4352 return (get_estimated_loop_iterations (loop, nit));
4353 }
4354
4355 /* Similar to estimated_loop_iterations, but returns the estimate only
4356 if it fits to HOST_WIDE_INT. If this is not the case, or the estimate
4357 on the number of iterations of LOOP could not be derived, returns -1. */
4358
4359 HOST_WIDE_INT
estimated_loop_iterations_int(class loop * loop)4360 estimated_loop_iterations_int (class loop *loop)
4361 {
4362 widest_int nit;
4363 HOST_WIDE_INT hwi_nit;
4364
4365 if (!estimated_loop_iterations (loop, &nit))
4366 return -1;
4367
4368 if (!wi::fits_shwi_p (nit))
4369 return -1;
4370 hwi_nit = nit.to_shwi ();
4371
4372 return hwi_nit < 0 ? -1 : hwi_nit;
4373 }
4374
4375
4376 /* Sets NIT to an upper bound for the maximum number of executions of the
4377 latch of the LOOP. If we have no reliable estimate, the function returns
4378 false, otherwise returns true. */
4379
4380 bool
max_loop_iterations(class loop * loop,widest_int * nit)4381 max_loop_iterations (class loop *loop, widest_int *nit)
4382 {
4383 /* When SCEV information is available, try to update loop iterations
4384 estimate. Otherwise just return whatever we recorded earlier. */
4385 if (scev_initialized_p ())
4386 estimate_numbers_of_iterations (loop);
4387
4388 return get_max_loop_iterations (loop, nit);
4389 }
4390
4391 /* Similar to max_loop_iterations, but returns the estimate only
4392 if it fits to HOST_WIDE_INT. If this is not the case, or the estimate
4393 on the number of iterations of LOOP could not be derived, returns -1. */
4394
4395 HOST_WIDE_INT
max_loop_iterations_int(class loop * loop)4396 max_loop_iterations_int (class loop *loop)
4397 {
4398 widest_int nit;
4399 HOST_WIDE_INT hwi_nit;
4400
4401 if (!max_loop_iterations (loop, &nit))
4402 return -1;
4403
4404 if (!wi::fits_shwi_p (nit))
4405 return -1;
4406 hwi_nit = nit.to_shwi ();
4407
4408 return hwi_nit < 0 ? -1 : hwi_nit;
4409 }
4410
4411 /* Sets NIT to an likely upper bound for the maximum number of executions of the
4412 latch of the LOOP. If we have no reliable estimate, the function returns
4413 false, otherwise returns true. */
4414
4415 bool
likely_max_loop_iterations(class loop * loop,widest_int * nit)4416 likely_max_loop_iterations (class loop *loop, widest_int *nit)
4417 {
4418 /* When SCEV information is available, try to update loop iterations
4419 estimate. Otherwise just return whatever we recorded earlier. */
4420 if (scev_initialized_p ())
4421 estimate_numbers_of_iterations (loop);
4422
4423 return get_likely_max_loop_iterations (loop, nit);
4424 }
4425
4426 /* Similar to max_loop_iterations, but returns the estimate only
4427 if it fits to HOST_WIDE_INT. If this is not the case, or the estimate
4428 on the number of iterations of LOOP could not be derived, returns -1. */
4429
4430 HOST_WIDE_INT
likely_max_loop_iterations_int(class loop * loop)4431 likely_max_loop_iterations_int (class loop *loop)
4432 {
4433 widest_int nit;
4434 HOST_WIDE_INT hwi_nit;
4435
4436 if (!likely_max_loop_iterations (loop, &nit))
4437 return -1;
4438
4439 if (!wi::fits_shwi_p (nit))
4440 return -1;
4441 hwi_nit = nit.to_shwi ();
4442
4443 return hwi_nit < 0 ? -1 : hwi_nit;
4444 }
4445
4446 /* Returns an estimate for the number of executions of statements
4447 in the LOOP. For statements before the loop exit, this exceeds
4448 the number of execution of the latch by one. */
4449
4450 HOST_WIDE_INT
estimated_stmt_executions_int(class loop * loop)4451 estimated_stmt_executions_int (class loop *loop)
4452 {
4453 HOST_WIDE_INT nit = estimated_loop_iterations_int (loop);
4454 HOST_WIDE_INT snit;
4455
4456 if (nit == -1)
4457 return -1;
4458
4459 snit = (HOST_WIDE_INT) ((unsigned HOST_WIDE_INT) nit + 1);
4460
4461 /* If the computation overflows, return -1. */
4462 return snit < 0 ? -1 : snit;
4463 }
4464
4465 /* Sets NIT to the maximum number of executions of the latch of the
4466 LOOP, plus one. If we have no reliable estimate, the function returns
4467 false, otherwise returns true. */
4468
4469 bool
max_stmt_executions(class loop * loop,widest_int * nit)4470 max_stmt_executions (class loop *loop, widest_int *nit)
4471 {
4472 widest_int nit_minus_one;
4473
4474 if (!max_loop_iterations (loop, nit))
4475 return false;
4476
4477 nit_minus_one = *nit;
4478
4479 *nit += 1;
4480
4481 return wi::gtu_p (*nit, nit_minus_one);
4482 }
4483
4484 /* Sets NIT to the estimated maximum number of executions of the latch of the
4485 LOOP, plus one. If we have no likely estimate, the function returns
4486 false, otherwise returns true. */
4487
4488 bool
likely_max_stmt_executions(class loop * loop,widest_int * nit)4489 likely_max_stmt_executions (class loop *loop, widest_int *nit)
4490 {
4491 widest_int nit_minus_one;
4492
4493 if (!likely_max_loop_iterations (loop, nit))
4494 return false;
4495
4496 nit_minus_one = *nit;
4497
4498 *nit += 1;
4499
4500 return wi::gtu_p (*nit, nit_minus_one);
4501 }
4502
4503 /* Sets NIT to the estimated number of executions of the latch of the
4504 LOOP, plus one. If we have no reliable estimate, the function returns
4505 false, otherwise returns true. */
4506
4507 bool
estimated_stmt_executions(class loop * loop,widest_int * nit)4508 estimated_stmt_executions (class loop *loop, widest_int *nit)
4509 {
4510 widest_int nit_minus_one;
4511
4512 if (!estimated_loop_iterations (loop, nit))
4513 return false;
4514
4515 nit_minus_one = *nit;
4516
4517 *nit += 1;
4518
4519 return wi::gtu_p (*nit, nit_minus_one);
4520 }
4521
4522 /* Records estimates on numbers of iterations of loops. */
4523
4524 void
estimate_numbers_of_iterations(function * fn)4525 estimate_numbers_of_iterations (function *fn)
4526 {
4527 class loop *loop;
4528
4529 /* We don't want to issue signed overflow warnings while getting
4530 loop iteration estimates. */
4531 fold_defer_overflow_warnings ();
4532
4533 FOR_EACH_LOOP_FN (fn, loop, 0)
4534 estimate_numbers_of_iterations (loop);
4535
4536 fold_undefer_and_ignore_overflow_warnings ();
4537 }
4538
4539 /* Returns true if statement S1 dominates statement S2. */
4540
4541 bool
stmt_dominates_stmt_p(gimple * s1,gimple * s2)4542 stmt_dominates_stmt_p (gimple *s1, gimple *s2)
4543 {
4544 basic_block bb1 = gimple_bb (s1), bb2 = gimple_bb (s2);
4545
4546 if (!bb1
4547 || s1 == s2)
4548 return true;
4549
4550 if (bb1 == bb2)
4551 {
4552 gimple_stmt_iterator bsi;
4553
4554 if (gimple_code (s2) == GIMPLE_PHI)
4555 return false;
4556
4557 if (gimple_code (s1) == GIMPLE_PHI)
4558 return true;
4559
4560 for (bsi = gsi_start_bb (bb1); gsi_stmt (bsi) != s2; gsi_next (&bsi))
4561 if (gsi_stmt (bsi) == s1)
4562 return true;
4563
4564 return false;
4565 }
4566
4567 return dominated_by_p (CDI_DOMINATORS, bb2, bb1);
4568 }
4569
4570 /* Returns true when we can prove that the number of executions of
4571 STMT in the loop is at most NITER, according to the bound on
4572 the number of executions of the statement NITER_BOUND->stmt recorded in
4573 NITER_BOUND and fact that NITER_BOUND->stmt dominate STMT.
4574
4575 ??? This code can become quite a CPU hog - we can have many bounds,
4576 and large basic block forcing stmt_dominates_stmt_p to be queried
4577 many times on a large basic blocks, so the whole thing is O(n^2)
4578 for scev_probably_wraps_p invocation (that can be done n times).
4579
4580 It would make more sense (and give better answers) to remember BB
4581 bounds computed by discover_iteration_bound_by_body_walk. */
4582
4583 static bool
n_of_executions_at_most(gimple * stmt,class nb_iter_bound * niter_bound,tree niter)4584 n_of_executions_at_most (gimple *stmt,
4585 class nb_iter_bound *niter_bound,
4586 tree niter)
4587 {
4588 widest_int bound = niter_bound->bound;
4589 tree nit_type = TREE_TYPE (niter), e;
4590 enum tree_code cmp;
4591
4592 gcc_assert (TYPE_UNSIGNED (nit_type));
4593
4594 /* If the bound does not even fit into NIT_TYPE, it cannot tell us that
4595 the number of iterations is small. */
4596 if (!wi::fits_to_tree_p (bound, nit_type))
4597 return false;
4598
4599 /* We know that NITER_BOUND->stmt is executed at most NITER_BOUND->bound + 1
4600 times. This means that:
4601
4602 -- if NITER_BOUND->is_exit is true, then everything after
4603 it at most NITER_BOUND->bound times.
4604
4605 -- If NITER_BOUND->is_exit is false, then if we can prove that when STMT
4606 is executed, then NITER_BOUND->stmt is executed as well in the same
4607 iteration then STMT is executed at most NITER_BOUND->bound + 1 times.
4608
4609 If we can determine that NITER_BOUND->stmt is always executed
4610 after STMT, then STMT is executed at most NITER_BOUND->bound + 2 times.
4611 We conclude that if both statements belong to the same
4612 basic block and STMT is before NITER_BOUND->stmt and there are no
4613 statements with side effects in between. */
4614
4615 if (niter_bound->is_exit)
4616 {
4617 if (stmt == niter_bound->stmt
4618 || !stmt_dominates_stmt_p (niter_bound->stmt, stmt))
4619 return false;
4620 cmp = GE_EXPR;
4621 }
4622 else
4623 {
4624 if (!stmt_dominates_stmt_p (niter_bound->stmt, stmt))
4625 {
4626 gimple_stmt_iterator bsi;
4627 if (gimple_bb (stmt) != gimple_bb (niter_bound->stmt)
4628 || gimple_code (stmt) == GIMPLE_PHI
4629 || gimple_code (niter_bound->stmt) == GIMPLE_PHI)
4630 return false;
4631
4632 /* By stmt_dominates_stmt_p we already know that STMT appears
4633 before NITER_BOUND->STMT. Still need to test that the loop
4634 cannot be terinated by a side effect in between. */
4635 for (bsi = gsi_for_stmt (stmt); gsi_stmt (bsi) != niter_bound->stmt;
4636 gsi_next (&bsi))
4637 if (gimple_has_side_effects (gsi_stmt (bsi)))
4638 return false;
4639 bound += 1;
4640 if (bound == 0
4641 || !wi::fits_to_tree_p (bound, nit_type))
4642 return false;
4643 }
4644 cmp = GT_EXPR;
4645 }
4646
4647 e = fold_binary (cmp, boolean_type_node,
4648 niter, wide_int_to_tree (nit_type, bound));
4649 return e && integer_nonzerop (e);
4650 }
4651
4652 /* Returns true if the arithmetics in TYPE can be assumed not to wrap. */
4653
4654 bool
nowrap_type_p(tree type)4655 nowrap_type_p (tree type)
4656 {
4657 if (ANY_INTEGRAL_TYPE_P (type)
4658 && TYPE_OVERFLOW_UNDEFINED (type))
4659 return true;
4660
4661 if (POINTER_TYPE_P (type))
4662 return true;
4663
4664 return false;
4665 }
4666
4667 /* Return true if we can prove LOOP is exited before evolution of induction
4668 variable {BASE, STEP} overflows with respect to its type bound. */
4669
4670 static bool
loop_exits_before_overflow(tree base,tree step,gimple * at_stmt,class loop * loop)4671 loop_exits_before_overflow (tree base, tree step,
4672 gimple *at_stmt, class loop *loop)
4673 {
4674 widest_int niter;
4675 struct control_iv *civ;
4676 class nb_iter_bound *bound;
4677 tree e, delta, step_abs, unsigned_base;
4678 tree type = TREE_TYPE (step);
4679 tree unsigned_type, valid_niter;
4680
4681 /* Don't issue signed overflow warnings. */
4682 fold_defer_overflow_warnings ();
4683
4684 /* Compute the number of iterations before we reach the bound of the
4685 type, and verify that the loop is exited before this occurs. */
4686 unsigned_type = unsigned_type_for (type);
4687 unsigned_base = fold_convert (unsigned_type, base);
4688
4689 if (tree_int_cst_sign_bit (step))
4690 {
4691 tree extreme = fold_convert (unsigned_type,
4692 lower_bound_in_type (type, type));
4693 delta = fold_build2 (MINUS_EXPR, unsigned_type, unsigned_base, extreme);
4694 step_abs = fold_build1 (NEGATE_EXPR, unsigned_type,
4695 fold_convert (unsigned_type, step));
4696 }
4697 else
4698 {
4699 tree extreme = fold_convert (unsigned_type,
4700 upper_bound_in_type (type, type));
4701 delta = fold_build2 (MINUS_EXPR, unsigned_type, extreme, unsigned_base);
4702 step_abs = fold_convert (unsigned_type, step);
4703 }
4704
4705 valid_niter = fold_build2 (FLOOR_DIV_EXPR, unsigned_type, delta, step_abs);
4706
4707 estimate_numbers_of_iterations (loop);
4708
4709 if (max_loop_iterations (loop, &niter)
4710 && wi::fits_to_tree_p (niter, TREE_TYPE (valid_niter))
4711 && (e = fold_binary (GT_EXPR, boolean_type_node, valid_niter,
4712 wide_int_to_tree (TREE_TYPE (valid_niter),
4713 niter))) != NULL
4714 && integer_nonzerop (e))
4715 {
4716 fold_undefer_and_ignore_overflow_warnings ();
4717 return true;
4718 }
4719 if (at_stmt)
4720 for (bound = loop->bounds; bound; bound = bound->next)
4721 {
4722 if (n_of_executions_at_most (at_stmt, bound, valid_niter))
4723 {
4724 fold_undefer_and_ignore_overflow_warnings ();
4725 return true;
4726 }
4727 }
4728 fold_undefer_and_ignore_overflow_warnings ();
4729
4730 /* Try to prove loop is exited before {base, step} overflows with the
4731 help of analyzed loop control IV. This is done only for IVs with
4732 constant step because otherwise we don't have the information. */
4733 if (TREE_CODE (step) == INTEGER_CST)
4734 {
4735 for (civ = loop->control_ivs; civ; civ = civ->next)
4736 {
4737 enum tree_code code;
4738 tree civ_type = TREE_TYPE (civ->step);
4739
4740 /* Have to consider type difference because operand_equal_p ignores
4741 that for constants. */
4742 if (TYPE_UNSIGNED (type) != TYPE_UNSIGNED (civ_type)
4743 || element_precision (type) != element_precision (civ_type))
4744 continue;
4745
4746 /* Only consider control IV with same step. */
4747 if (!operand_equal_p (step, civ->step, 0))
4748 continue;
4749
4750 /* Done proving if this is a no-overflow control IV. */
4751 if (operand_equal_p (base, civ->base, 0))
4752 return true;
4753
4754 /* Control IV is recorded after expanding simple operations,
4755 Here we expand base and compare it too. */
4756 tree expanded_base = expand_simple_operations (base);
4757 if (operand_equal_p (expanded_base, civ->base, 0))
4758 return true;
4759
4760 /* If this is a before stepping control IV, in other words, we have
4761
4762 {civ_base, step} = {base + step, step}
4763
4764 Because civ {base + step, step} doesn't overflow during loop
4765 iterations, {base, step} will not overflow if we can prove the
4766 operation "base + step" does not overflow. Specifically, we try
4767 to prove below conditions are satisfied:
4768
4769 base <= UPPER_BOUND (type) - step ;;step > 0
4770 base >= LOWER_BOUND (type) - step ;;step < 0
4771
4772 by proving the reverse conditions are false using loop's initial
4773 condition. */
4774 if (POINTER_TYPE_P (TREE_TYPE (base)))
4775 code = POINTER_PLUS_EXPR;
4776 else
4777 code = PLUS_EXPR;
4778
4779 tree stepped = fold_build2 (code, TREE_TYPE (base), base, step);
4780 tree expanded_stepped = fold_build2 (code, TREE_TYPE (base),
4781 expanded_base, step);
4782 if (operand_equal_p (stepped, civ->base, 0)
4783 || operand_equal_p (expanded_stepped, civ->base, 0))
4784 {
4785 tree extreme;
4786
4787 if (tree_int_cst_sign_bit (step))
4788 {
4789 code = LT_EXPR;
4790 extreme = lower_bound_in_type (type, type);
4791 }
4792 else
4793 {
4794 code = GT_EXPR;
4795 extreme = upper_bound_in_type (type, type);
4796 }
4797 extreme = fold_build2 (MINUS_EXPR, type, extreme, step);
4798 e = fold_build2 (code, boolean_type_node, base, extreme);
4799 e = simplify_using_initial_conditions (loop, e);
4800 if (integer_zerop (e))
4801 return true;
4802 }
4803 }
4804 }
4805
4806 return false;
4807 }
4808
4809 /* VAR is scev variable whose evolution part is constant STEP, this function
4810 proves that VAR can't overflow by using value range info. If VAR's value
4811 range is [MIN, MAX], it can be proven by:
4812 MAX + step doesn't overflow ; if step > 0
4813 or
4814 MIN + step doesn't underflow ; if step < 0.
4815
4816 We can only do this if var is computed in every loop iteration, i.e, var's
4817 definition has to dominate loop latch. Consider below example:
4818
4819 {
4820 unsigned int i;
4821
4822 <bb 3>:
4823
4824 <bb 4>:
4825 # RANGE [0, 4294967294] NONZERO 65535
4826 # i_21 = PHI <0(3), i_18(9)>
4827 if (i_21 != 0)
4828 goto <bb 6>;
4829 else
4830 goto <bb 8>;
4831
4832 <bb 6>:
4833 # RANGE [0, 65533] NONZERO 65535
4834 _6 = i_21 + 4294967295;
4835 # RANGE [0, 65533] NONZERO 65535
4836 _7 = (long unsigned int) _6;
4837 # RANGE [0, 524264] NONZERO 524280
4838 _8 = _7 * 8;
4839 # PT = nonlocal escaped
4840 _9 = a_14 + _8;
4841 *_9 = 0;
4842
4843 <bb 8>:
4844 # RANGE [1, 65535] NONZERO 65535
4845 i_18 = i_21 + 1;
4846 if (i_18 >= 65535)
4847 goto <bb 10>;
4848 else
4849 goto <bb 9>;
4850
4851 <bb 9>:
4852 goto <bb 4>;
4853
4854 <bb 10>:
4855 return;
4856 }
4857
4858 VAR _6 doesn't overflow only with pre-condition (i_21 != 0), here we
4859 can't use _6 to prove no-overlfow for _7. In fact, var _7 takes value
4860 sequence (4294967295, 0, 1, ..., 65533) in loop life time, rather than
4861 (4294967295, 4294967296, ...). */
4862
4863 static bool
scev_var_range_cant_overflow(tree var,tree step,class loop * loop)4864 scev_var_range_cant_overflow (tree var, tree step, class loop *loop)
4865 {
4866 tree type;
4867 wide_int minv, maxv, diff, step_wi;
4868 enum value_range_kind rtype;
4869
4870 if (TREE_CODE (step) != INTEGER_CST || !INTEGRAL_TYPE_P (TREE_TYPE (var)))
4871 return false;
4872
4873 /* Check if VAR evaluates in every loop iteration. It's not the case
4874 if VAR is default definition or does not dominate loop's latch. */
4875 basic_block def_bb = gimple_bb (SSA_NAME_DEF_STMT (var));
4876 if (!def_bb || !dominated_by_p (CDI_DOMINATORS, loop->latch, def_bb))
4877 return false;
4878
4879 rtype = get_range_info (var, &minv, &maxv);
4880 if (rtype != VR_RANGE)
4881 return false;
4882
4883 /* VAR is a scev whose evolution part is STEP and value range info
4884 is [MIN, MAX], we can prove its no-overflowness by conditions:
4885
4886 type_MAX - MAX >= step ; if step > 0
4887 MIN - type_MIN >= |step| ; if step < 0.
4888
4889 Or VAR must take value outside of value range, which is not true. */
4890 step_wi = wi::to_wide (step);
4891 type = TREE_TYPE (var);
4892 if (tree_int_cst_sign_bit (step))
4893 {
4894 diff = minv - wi::to_wide (lower_bound_in_type (type, type));
4895 step_wi = - step_wi;
4896 }
4897 else
4898 diff = wi::to_wide (upper_bound_in_type (type, type)) - maxv;
4899
4900 return (wi::geu_p (diff, step_wi));
4901 }
4902
4903 /* Return false only when the induction variable BASE + STEP * I is
4904 known to not overflow: i.e. when the number of iterations is small
4905 enough with respect to the step and initial condition in order to
4906 keep the evolution confined in TYPEs bounds. Return true when the
4907 iv is known to overflow or when the property is not computable.
4908
4909 USE_OVERFLOW_SEMANTICS is true if this function should assume that
4910 the rules for overflow of the given language apply (e.g., that signed
4911 arithmetics in C does not overflow).
4912
4913 If VAR is a ssa variable, this function also returns false if VAR can
4914 be proven not overflow with value range info. */
4915
4916 bool
scev_probably_wraps_p(tree var,tree base,tree step,gimple * at_stmt,class loop * loop,bool use_overflow_semantics)4917 scev_probably_wraps_p (tree var, tree base, tree step,
4918 gimple *at_stmt, class loop *loop,
4919 bool use_overflow_semantics)
4920 {
4921 /* FIXME: We really need something like
4922 http://gcc.gnu.org/ml/gcc-patches/2005-06/msg02025.html.
4923
4924 We used to test for the following situation that frequently appears
4925 during address arithmetics:
4926
4927 D.1621_13 = (long unsigned intD.4) D.1620_12;
4928 D.1622_14 = D.1621_13 * 8;
4929 D.1623_15 = (doubleD.29 *) D.1622_14;
4930
4931 And derived that the sequence corresponding to D_14
4932 can be proved to not wrap because it is used for computing a
4933 memory access; however, this is not really the case -- for example,
4934 if D_12 = (unsigned char) [254,+,1], then D_14 has values
4935 2032, 2040, 0, 8, ..., but the code is still legal. */
4936
4937 if (chrec_contains_undetermined (base)
4938 || chrec_contains_undetermined (step))
4939 return true;
4940
4941 if (integer_zerop (step))
4942 return false;
4943
4944 /* If we can use the fact that signed and pointer arithmetics does not
4945 wrap, we are done. */
4946 if (use_overflow_semantics && nowrap_type_p (TREE_TYPE (base)))
4947 return false;
4948
4949 /* To be able to use estimates on number of iterations of the loop,
4950 we must have an upper bound on the absolute value of the step. */
4951 if (TREE_CODE (step) != INTEGER_CST)
4952 return true;
4953
4954 /* Check if var can be proven not overflow with value range info. */
4955 if (var && TREE_CODE (var) == SSA_NAME
4956 && scev_var_range_cant_overflow (var, step, loop))
4957 return false;
4958
4959 if (loop_exits_before_overflow (base, step, at_stmt, loop))
4960 return false;
4961
4962 /* At this point we still don't have a proof that the iv does not
4963 overflow: give up. */
4964 return true;
4965 }
4966
4967 /* Frees the information on upper bounds on numbers of iterations of LOOP. */
4968
4969 void
free_numbers_of_iterations_estimates(class loop * loop)4970 free_numbers_of_iterations_estimates (class loop *loop)
4971 {
4972 struct control_iv *civ;
4973 class nb_iter_bound *bound;
4974
4975 loop->nb_iterations = NULL;
4976 loop->estimate_state = EST_NOT_COMPUTED;
4977 for (bound = loop->bounds; bound;)
4978 {
4979 class nb_iter_bound *next = bound->next;
4980 ggc_free (bound);
4981 bound = next;
4982 }
4983 loop->bounds = NULL;
4984
4985 for (civ = loop->control_ivs; civ;)
4986 {
4987 struct control_iv *next = civ->next;
4988 ggc_free (civ);
4989 civ = next;
4990 }
4991 loop->control_ivs = NULL;
4992 }
4993
4994 /* Frees the information on upper bounds on numbers of iterations of loops. */
4995
4996 void
free_numbers_of_iterations_estimates(function * fn)4997 free_numbers_of_iterations_estimates (function *fn)
4998 {
4999 class loop *loop;
5000
5001 FOR_EACH_LOOP_FN (fn, loop, 0)
5002 free_numbers_of_iterations_estimates (loop);
5003 }
5004
5005 /* Substitute value VAL for ssa name NAME inside expressions held
5006 at LOOP. */
5007
5008 void
substitute_in_loop_info(class loop * loop,tree name,tree val)5009 substitute_in_loop_info (class loop *loop, tree name, tree val)
5010 {
5011 loop->nb_iterations = simplify_replace_tree (loop->nb_iterations, name, val);
5012 }
5013