1 /* Functions to determine/estimate number of iterations of a loop.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation,
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 3, or (at your option) any
12 GCC is distributed in the hope that it will be useful, but WITHOUT
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
28 #include "hard-reg-set.h"
29 #include "basic-block.h"
31 #include "diagnostic.h"
33 #include "tree-flow.h"
34 #include "tree-dump.h"
36 #include "tree-pass.h"
38 #include "tree-chrec.h"
39 #include "tree-scalar-evolution.h"
40 #include "tree-data-ref.h"
44 #include "tree-inline.h"
47 #define SWAP(X, Y) do { affine_iv *tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
49 /* The maximum number of dominator BBs we search for conditions
50 of loop header copies we use for simplifying a conditional
52 #define MAX_DOMINATORS_TO_WALK 8
56 Analysis of number of iterations of an affine exit test.
60 /* Bounds on some value, BELOW <= X <= UP. */
68 /* Splits expression EXPR to a variable part VAR and constant OFFSET. */
71 split_to_var_and_offset (tree expr
, tree
*var
, mpz_t offset
)
73 tree type
= TREE_TYPE (expr
);
79 mpz_set_ui (offset
, 0);
81 switch (TREE_CODE (expr
))
88 case POINTER_PLUS_EXPR
:
89 op0
= TREE_OPERAND (expr
, 0);
90 op1
= TREE_OPERAND (expr
, 1);
92 if (TREE_CODE (op1
) != INTEGER_CST
)
96 /* Always sign extend the offset. */
97 off
= double_int_sext (tree_to_double_int (op1
),
98 TYPE_PRECISION (type
));
99 mpz_set_double_int (offset
, off
, false);
103 *var
= build_int_cst_type (type
, 0);
104 off
= tree_to_double_int (expr
);
105 mpz_set_double_int (offset
, off
, TYPE_UNSIGNED (type
));
113 /* Stores estimate on the minimum/maximum value of the expression VAR + OFF
114 in TYPE to MIN and MAX. */
117 determine_value_range (tree type
, tree var
, mpz_t off
,
118 mpz_t min
, mpz_t max
)
120 /* If the expression is a constant, we know its value exactly. */
121 if (integer_zerop (var
))
128 /* If the computation may wrap, we know nothing about the value, except for
129 the range of the type. */
130 get_type_static_bounds (type
, min
, max
);
131 if (!nowrap_type_p (type
))
134 /* Since the addition of OFF does not wrap, if OFF is positive, then we may
135 add it to MIN, otherwise to MAX. */
136 if (mpz_sgn (off
) < 0)
137 mpz_add (max
, max
, off
);
139 mpz_add (min
, min
, off
);
142 /* Stores the bounds on the difference of the values of the expressions
143 (var + X) and (var + Y), computed in TYPE, to BNDS. */
146 bound_difference_of_offsetted_base (tree type
, mpz_t x
, mpz_t y
,
149 int rel
= mpz_cmp (x
, y
);
150 bool may_wrap
= !nowrap_type_p (type
);
153 /* If X == Y, then the expressions are always equal.
154 If X > Y, there are the following possibilities:
155 a) neither of var + X and var + Y overflow or underflow, or both of
156 them do. Then their difference is X - Y.
157 b) var + X overflows, and var + Y does not. Then the values of the
158 expressions are var + X - M and var + Y, where M is the range of
159 the type, and their difference is X - Y - M.
160 c) var + Y underflows and var + X does not. Their difference again
162 Therefore, if the arithmetics in type does not overflow, then the
163 bounds are (X - Y, X - Y), otherwise they are (X - Y - M, X - Y)
164 Similarly, if X < Y, the bounds are either (X - Y, X - Y) or
165 (X - Y, X - Y + M). */
169 mpz_set_ui (bnds
->below
, 0);
170 mpz_set_ui (bnds
->up
, 0);
175 mpz_set_double_int (m
, double_int_mask (TYPE_PRECISION (type
)), true);
176 mpz_add_ui (m
, m
, 1);
177 mpz_sub (bnds
->up
, x
, y
);
178 mpz_set (bnds
->below
, bnds
->up
);
183 mpz_sub (bnds
->below
, bnds
->below
, m
);
185 mpz_add (bnds
->up
, bnds
->up
, m
);
191 /* From condition C0 CMP C1 derives information regarding the
192 difference of values of VARX + OFFX and VARY + OFFY, computed in TYPE,
193 and stores it to BNDS. */
196 refine_bounds_using_guard (tree type
, tree varx
, mpz_t offx
,
197 tree vary
, mpz_t offy
,
198 tree c0
, enum tree_code cmp
, tree c1
,
201 tree varc0
, varc1
, tmp
, ctype
;
202 mpz_t offc0
, offc1
, loffx
, loffy
, bnd
;
204 bool no_wrap
= nowrap_type_p (type
);
213 STRIP_SIGN_NOPS (c0
);
214 STRIP_SIGN_NOPS (c1
);
215 ctype
= TREE_TYPE (c0
);
216 if (!useless_type_conversion_p (ctype
, type
))
222 /* We could derive quite precise information from EQ_EXPR, however, such
223 a guard is unlikely to appear, so we do not bother with handling
228 /* NE_EXPR comparisons do not contain much of useful information, except for
229 special case of comparing with the bounds of the type. */
230 if (TREE_CODE (c1
) != INTEGER_CST
231 || !INTEGRAL_TYPE_P (type
))
234 /* Ensure that the condition speaks about an expression in the same type
236 ctype
= TREE_TYPE (c0
);
237 if (TYPE_PRECISION (ctype
) != TYPE_PRECISION (type
))
239 c0
= fold_convert (type
, c0
);
240 c1
= fold_convert (type
, c1
);
242 if (TYPE_MIN_VALUE (type
)
243 && operand_equal_p (c1
, TYPE_MIN_VALUE (type
), 0))
248 if (TYPE_MAX_VALUE (type
)
249 && operand_equal_p (c1
, TYPE_MAX_VALUE (type
), 0))
262 split_to_var_and_offset (expand_simple_operations (c0
), &varc0
, offc0
);
263 split_to_var_and_offset (expand_simple_operations (c1
), &varc1
, offc1
);
265 /* We are only interested in comparisons of expressions based on VARX and
266 VARY. TODO -- we might also be able to derive some bounds from
267 expressions containing just one of the variables. */
269 if (operand_equal_p (varx
, varc1
, 0))
271 tmp
= varc0
; varc0
= varc1
; varc1
= tmp
;
272 mpz_swap (offc0
, offc1
);
273 cmp
= swap_tree_comparison (cmp
);
276 if (!operand_equal_p (varx
, varc0
, 0)
277 || !operand_equal_p (vary
, varc1
, 0))
280 mpz_init_set (loffx
, offx
);
281 mpz_init_set (loffy
, offy
);
283 if (cmp
== GT_EXPR
|| cmp
== GE_EXPR
)
285 tmp
= varx
; varx
= vary
; vary
= tmp
;
286 mpz_swap (offc0
, offc1
);
287 mpz_swap (loffx
, loffy
);
288 cmp
= swap_tree_comparison (cmp
);
292 /* If there is no overflow, the condition implies that
294 (VARX + OFFX) cmp (VARY + OFFY) + (OFFX - OFFY + OFFC1 - OFFC0).
296 The overflows and underflows may complicate things a bit; each
297 overflow decreases the appropriate offset by M, and underflow
298 increases it by M. The above inequality would not necessarily be
301 -- VARX + OFFX underflows and VARX + OFFC0 does not, or
302 VARX + OFFC0 overflows, but VARX + OFFX does not.
303 This may only happen if OFFX < OFFC0.
304 -- VARY + OFFY overflows and VARY + OFFC1 does not, or
305 VARY + OFFC1 underflows and VARY + OFFY does not.
306 This may only happen if OFFY > OFFC1. */
315 x_ok
= (integer_zerop (varx
)
316 || mpz_cmp (loffx
, offc0
) >= 0);
317 y_ok
= (integer_zerop (vary
)
318 || mpz_cmp (loffy
, offc1
) <= 0);
324 mpz_sub (bnd
, loffx
, loffy
);
325 mpz_add (bnd
, bnd
, offc1
);
326 mpz_sub (bnd
, bnd
, offc0
);
329 mpz_sub_ui (bnd
, bnd
, 1);
334 if (mpz_cmp (bnds
->below
, bnd
) < 0)
335 mpz_set (bnds
->below
, bnd
);
339 if (mpz_cmp (bnd
, bnds
->up
) < 0)
340 mpz_set (bnds
->up
, bnd
);
352 /* Stores the bounds on the value of the expression X - Y in LOOP to BNDS.
353 The subtraction is considered to be performed in arbitrary precision,
356 We do not attempt to be too clever regarding the value ranges of X and
357 Y; most of the time, they are just integers or ssa names offsetted by
358 integer. However, we try to use the information contained in the
359 comparisons before the loop (usually created by loop header copying). */
362 bound_difference (struct loop
*loop
, tree x
, tree y
, bounds
*bnds
)
364 tree type
= TREE_TYPE (x
);
367 mpz_t minx
, maxx
, miny
, maxy
;
375 /* Get rid of unnecessary casts, but preserve the value of
380 mpz_init (bnds
->below
);
384 split_to_var_and_offset (x
, &varx
, offx
);
385 split_to_var_and_offset (y
, &vary
, offy
);
387 if (!integer_zerop (varx
)
388 && operand_equal_p (varx
, vary
, 0))
390 /* Special case VARX == VARY -- we just need to compare the
391 offsets. The matters are a bit more complicated in the
392 case addition of offsets may wrap. */
393 bound_difference_of_offsetted_base (type
, offx
, offy
, bnds
);
397 /* Otherwise, use the value ranges to determine the initial
398 estimates on below and up. */
403 determine_value_range (type
, varx
, offx
, minx
, maxx
);
404 determine_value_range (type
, vary
, offy
, miny
, maxy
);
406 mpz_sub (bnds
->below
, minx
, maxy
);
407 mpz_sub (bnds
->up
, maxx
, miny
);
414 /* If both X and Y are constants, we cannot get any more precise. */
415 if (integer_zerop (varx
) && integer_zerop (vary
))
418 /* Now walk the dominators of the loop header and use the entry
419 guards to refine the estimates. */
420 for (bb
= loop
->header
;
421 bb
!= ENTRY_BLOCK_PTR
&& cnt
< MAX_DOMINATORS_TO_WALK
;
422 bb
= get_immediate_dominator (CDI_DOMINATORS
, bb
))
424 if (!single_pred_p (bb
))
426 e
= single_pred_edge (bb
);
428 if (!(e
->flags
& (EDGE_TRUE_VALUE
| EDGE_FALSE_VALUE
)))
431 cond
= last_stmt (e
->src
);
432 c0
= gimple_cond_lhs (cond
);
433 cmp
= gimple_cond_code (cond
);
434 c1
= gimple_cond_rhs (cond
);
436 if (e
->flags
& EDGE_FALSE_VALUE
)
437 cmp
= invert_tree_comparison (cmp
, false);
439 refine_bounds_using_guard (type
, varx
, offx
, vary
, offy
,
449 /* Update the bounds in BNDS that restrict the value of X to the bounds
450 that restrict the value of X + DELTA. X can be obtained as a
451 difference of two values in TYPE. */
454 bounds_add (bounds
*bnds
, double_int delta
, tree type
)
459 mpz_set_double_int (mdelta
, delta
, false);
462 mpz_set_double_int (max
, double_int_mask (TYPE_PRECISION (type
)), true);
464 mpz_add (bnds
->up
, bnds
->up
, mdelta
);
465 mpz_add (bnds
->below
, bnds
->below
, mdelta
);
467 if (mpz_cmp (bnds
->up
, max
) > 0)
468 mpz_set (bnds
->up
, max
);
471 if (mpz_cmp (bnds
->below
, max
) < 0)
472 mpz_set (bnds
->below
, max
);
478 /* Update the bounds in BNDS that restrict the value of X to the bounds
479 that restrict the value of -X. */
482 bounds_negate (bounds
*bnds
)
486 mpz_init_set (tmp
, bnds
->up
);
487 mpz_neg (bnds
->up
, bnds
->below
);
488 mpz_neg (bnds
->below
, tmp
);
492 /* Returns inverse of X modulo 2^s, where MASK = 2^s-1. */
495 inverse (tree x
, tree mask
)
497 tree type
= TREE_TYPE (x
);
499 unsigned ctr
= tree_floor_log2 (mask
);
501 if (TYPE_PRECISION (type
) <= HOST_BITS_PER_WIDE_INT
)
503 unsigned HOST_WIDE_INT ix
;
504 unsigned HOST_WIDE_INT imask
;
505 unsigned HOST_WIDE_INT irslt
= 1;
507 gcc_assert (cst_and_fits_in_hwi (x
));
508 gcc_assert (cst_and_fits_in_hwi (mask
));
510 ix
= int_cst_value (x
);
511 imask
= int_cst_value (mask
);
520 rslt
= build_int_cst_type (type
, irslt
);
524 rslt
= build_int_cst (type
, 1);
527 rslt
= int_const_binop (MULT_EXPR
, rslt
, x
, 0);
528 x
= int_const_binop (MULT_EXPR
, x
, x
, 0);
530 rslt
= int_const_binop (BIT_AND_EXPR
, rslt
, mask
, 0);
536 /* Derives the upper bound BND on the number of executions of loop with exit
537 condition S * i <> C, assuming that this exit is taken. If
538 NO_OVERFLOW is true, then the control variable of the loop does not
539 overflow. If NO_OVERFLOW is true or BNDS.below >= 0, then BNDS.up
540 contains the upper bound on the value of C. */
543 number_of_iterations_ne_max (mpz_t bnd
, bool no_overflow
, tree c
, tree s
,
549 /* If the control variable does not overflow, the number of iterations is
550 at most c / s. Otherwise it is at most the period of the control
552 if (!no_overflow
&& !multiple_of_p (TREE_TYPE (c
), c
, s
))
554 max
= double_int_mask (TYPE_PRECISION (TREE_TYPE (c
))
555 - tree_low_cst (num_ending_zeros (s
), 1));
556 mpz_set_double_int (bnd
, max
, true);
560 /* Determine the upper bound on C. */
561 if (no_overflow
|| mpz_sgn (bnds
->below
) >= 0)
562 mpz_set (bnd
, bnds
->up
);
563 else if (TREE_CODE (c
) == INTEGER_CST
)
564 mpz_set_double_int (bnd
, tree_to_double_int (c
), true);
566 mpz_set_double_int (bnd
, double_int_mask (TYPE_PRECISION (TREE_TYPE (c
))),
570 mpz_set_double_int (d
, tree_to_double_int (s
), true);
571 mpz_fdiv_q (bnd
, bnd
, d
);
575 /* Determines number of iterations of loop whose ending condition
576 is IV <> FINAL. TYPE is the type of the iv. The number of
577 iterations is stored to NITER. EXIT_MUST_BE_TAKEN is true if
578 we know that the exit must be taken eventually, i.e., that the IV
579 ever reaches the value FINAL (we derived this earlier, and possibly set
580 NITER->assumptions to make sure this is the case). BNDS contains the
581 bounds on the difference FINAL - IV->base. */
584 number_of_iterations_ne (tree type
, affine_iv
*iv
, tree final
,
585 struct tree_niter_desc
*niter
, bool exit_must_be_taken
,
588 tree niter_type
= unsigned_type_for (type
);
589 tree s
, c
, d
, bits
, assumption
, tmp
, bound
;
592 niter
->control
= *iv
;
593 niter
->bound
= final
;
594 niter
->cmp
= NE_EXPR
;
596 /* Rearrange the terms so that we get inequality S * i <> C, with S
597 positive. Also cast everything to the unsigned type. If IV does
598 not overflow, BNDS bounds the value of C. Also, this is the
599 case if the computation |FINAL - IV->base| does not overflow, i.e.,
600 if BNDS->below in the result is nonnegative. */
601 if (tree_int_cst_sign_bit (iv
->step
))
603 s
= fold_convert (niter_type
,
604 fold_build1 (NEGATE_EXPR
, type
, iv
->step
));
605 c
= fold_build2 (MINUS_EXPR
, niter_type
,
606 fold_convert (niter_type
, iv
->base
),
607 fold_convert (niter_type
, final
));
608 bounds_negate (bnds
);
612 s
= fold_convert (niter_type
, iv
->step
);
613 c
= fold_build2 (MINUS_EXPR
, niter_type
,
614 fold_convert (niter_type
, final
),
615 fold_convert (niter_type
, iv
->base
));
619 number_of_iterations_ne_max (max
, iv
->no_overflow
, c
, s
, bnds
);
620 niter
->max
= mpz_get_double_int (niter_type
, max
, false);
623 /* First the trivial cases -- when the step is 1. */
624 if (integer_onep (s
))
630 /* Let nsd (step, size of mode) = d. If d does not divide c, the loop
631 is infinite. Otherwise, the number of iterations is
632 (inverse(s/d) * (c/d)) mod (size of mode/d). */
633 bits
= num_ending_zeros (s
);
634 bound
= build_low_bits_mask (niter_type
,
635 (TYPE_PRECISION (niter_type
)
636 - tree_low_cst (bits
, 1)));
638 d
= fold_binary_to_constant (LSHIFT_EXPR
, niter_type
,
639 build_int_cst (niter_type
, 1), bits
);
640 s
= fold_binary_to_constant (RSHIFT_EXPR
, niter_type
, s
, bits
);
642 if (!exit_must_be_taken
)
644 /* If we cannot assume that the exit is taken eventually, record the
645 assumptions for divisibility of c. */
646 assumption
= fold_build2 (FLOOR_MOD_EXPR
, niter_type
, c
, d
);
647 assumption
= fold_build2 (EQ_EXPR
, boolean_type_node
,
648 assumption
, build_int_cst (niter_type
, 0));
649 if (!integer_nonzerop (assumption
))
650 niter
->assumptions
= fold_build2 (TRUTH_AND_EXPR
, boolean_type_node
,
651 niter
->assumptions
, assumption
);
654 c
= fold_build2 (EXACT_DIV_EXPR
, niter_type
, c
, d
);
655 tmp
= fold_build2 (MULT_EXPR
, niter_type
, c
, inverse (s
, bound
));
656 niter
->niter
= fold_build2 (BIT_AND_EXPR
, niter_type
, tmp
, bound
);
660 /* Checks whether we can determine the final value of the control variable
661 of the loop with ending condition IV0 < IV1 (computed in TYPE).
662 DELTA is the difference IV1->base - IV0->base, STEP is the absolute value
663 of the step. The assumptions necessary to ensure that the computation
664 of the final value does not overflow are recorded in NITER. If we
665 find the final value, we adjust DELTA and return TRUE. Otherwise
666 we return false. BNDS bounds the value of IV1->base - IV0->base,
667 and will be updated by the same amount as DELTA. EXIT_MUST_BE_TAKEN is
668 true if we know that the exit must be taken eventually. */
671 number_of_iterations_lt_to_ne (tree type
, affine_iv
*iv0
, affine_iv
*iv1
,
672 struct tree_niter_desc
*niter
,
673 tree
*delta
, tree step
,
674 bool exit_must_be_taken
, bounds
*bnds
)
676 tree niter_type
= TREE_TYPE (step
);
677 tree mod
= fold_build2 (FLOOR_MOD_EXPR
, niter_type
, *delta
, step
);
680 tree assumption
= boolean_true_node
, bound
, noloop
;
681 bool ret
= false, fv_comp_no_overflow
;
683 if (POINTER_TYPE_P (type
))
686 if (TREE_CODE (mod
) != INTEGER_CST
)
688 if (integer_nonzerop (mod
))
689 mod
= fold_build2 (MINUS_EXPR
, niter_type
, step
, mod
);
690 tmod
= fold_convert (type1
, mod
);
693 mpz_set_double_int (mmod
, tree_to_double_int (mod
), true);
694 mpz_neg (mmod
, mmod
);
696 /* If the induction variable does not overflow and the exit is taken,
697 then the computation of the final value does not overflow. This is
698 also obviously the case if the new final value is equal to the
699 current one. Finally, we postulate this for pointer type variables,
700 as the code cannot rely on the object to that the pointer points being
701 placed at the end of the address space (and more pragmatically,
702 TYPE_{MIN,MAX}_VALUE is not defined for pointers). */
703 if (integer_zerop (mod
) || POINTER_TYPE_P (type
))
704 fv_comp_no_overflow
= true;
705 else if (!exit_must_be_taken
)
706 fv_comp_no_overflow
= false;
708 fv_comp_no_overflow
=
709 (iv0
->no_overflow
&& integer_nonzerop (iv0
->step
))
710 || (iv1
->no_overflow
&& integer_nonzerop (iv1
->step
));
712 if (integer_nonzerop (iv0
->step
))
714 /* The final value of the iv is iv1->base + MOD, assuming that this
715 computation does not overflow, and that
716 iv0->base <= iv1->base + MOD. */
717 if (!fv_comp_no_overflow
)
719 bound
= fold_build2 (MINUS_EXPR
, type1
,
720 TYPE_MAX_VALUE (type1
), tmod
);
721 assumption
= fold_build2 (LE_EXPR
, boolean_type_node
,
723 if (integer_zerop (assumption
))
726 if (mpz_cmp (mmod
, bnds
->below
) < 0)
727 noloop
= boolean_false_node
;
728 else if (POINTER_TYPE_P (type
))
729 noloop
= fold_build2 (GT_EXPR
, boolean_type_node
,
731 fold_build2 (POINTER_PLUS_EXPR
, type
,
734 noloop
= fold_build2 (GT_EXPR
, boolean_type_node
,
736 fold_build2 (PLUS_EXPR
, type1
,
741 /* The final value of the iv is iv0->base - MOD, assuming that this
742 computation does not overflow, and that
743 iv0->base - MOD <= iv1->base. */
744 if (!fv_comp_no_overflow
)
746 bound
= fold_build2 (PLUS_EXPR
, type1
,
747 TYPE_MIN_VALUE (type1
), tmod
);
748 assumption
= fold_build2 (GE_EXPR
, boolean_type_node
,
750 if (integer_zerop (assumption
))
753 if (mpz_cmp (mmod
, bnds
->below
) < 0)
754 noloop
= boolean_false_node
;
755 else if (POINTER_TYPE_P (type
))
756 noloop
= fold_build2 (GT_EXPR
, boolean_type_node
,
757 fold_build2 (POINTER_PLUS_EXPR
, type
,
759 fold_build1 (NEGATE_EXPR
,
763 noloop
= fold_build2 (GT_EXPR
, boolean_type_node
,
764 fold_build2 (MINUS_EXPR
, type1
,
769 if (!integer_nonzerop (assumption
))
770 niter
->assumptions
= fold_build2 (TRUTH_AND_EXPR
, boolean_type_node
,
773 if (!integer_zerop (noloop
))
774 niter
->may_be_zero
= fold_build2 (TRUTH_OR_EXPR
, boolean_type_node
,
777 bounds_add (bnds
, tree_to_double_int (mod
), type
);
778 *delta
= fold_build2 (PLUS_EXPR
, niter_type
, *delta
, mod
);
786 /* Add assertions to NITER that ensure that the control variable of the loop
787 with ending condition IV0 < IV1 does not overflow. Types of IV0 and IV1
788 are TYPE. Returns false if we can prove that there is an overflow, true
789 otherwise. STEP is the absolute value of the step. */
792 assert_no_overflow_lt (tree type
, affine_iv
*iv0
, affine_iv
*iv1
,
793 struct tree_niter_desc
*niter
, tree step
)
795 tree bound
, d
, assumption
, diff
;
796 tree niter_type
= TREE_TYPE (step
);
798 if (integer_nonzerop (iv0
->step
))
800 /* for (i = iv0->base; i < iv1->base; i += iv0->step) */
801 if (iv0
->no_overflow
)
804 /* If iv0->base is a constant, we can determine the last value before
805 overflow precisely; otherwise we conservatively assume
808 if (TREE_CODE (iv0
->base
) == INTEGER_CST
)
810 d
= fold_build2 (MINUS_EXPR
, niter_type
,
811 fold_convert (niter_type
, TYPE_MAX_VALUE (type
)),
812 fold_convert (niter_type
, iv0
->base
));
813 diff
= fold_build2 (FLOOR_MOD_EXPR
, niter_type
, d
, step
);
816 diff
= fold_build2 (MINUS_EXPR
, niter_type
, step
,
817 build_int_cst (niter_type
, 1));
818 bound
= fold_build2 (MINUS_EXPR
, type
,
819 TYPE_MAX_VALUE (type
), fold_convert (type
, diff
));
820 assumption
= fold_build2 (LE_EXPR
, boolean_type_node
,
825 /* for (i = iv1->base; i > iv0->base; i += iv1->step) */
826 if (iv1
->no_overflow
)
829 if (TREE_CODE (iv1
->base
) == INTEGER_CST
)
831 d
= fold_build2 (MINUS_EXPR
, niter_type
,
832 fold_convert (niter_type
, iv1
->base
),
833 fold_convert (niter_type
, TYPE_MIN_VALUE (type
)));
834 diff
= fold_build2 (FLOOR_MOD_EXPR
, niter_type
, d
, step
);
837 diff
= fold_build2 (MINUS_EXPR
, niter_type
, step
,
838 build_int_cst (niter_type
, 1));
839 bound
= fold_build2 (PLUS_EXPR
, type
,
840 TYPE_MIN_VALUE (type
), fold_convert (type
, diff
));
841 assumption
= fold_build2 (GE_EXPR
, boolean_type_node
,
845 if (integer_zerop (assumption
))
847 if (!integer_nonzerop (assumption
))
848 niter
->assumptions
= fold_build2 (TRUTH_AND_EXPR
, boolean_type_node
,
849 niter
->assumptions
, assumption
);
851 iv0
->no_overflow
= true;
852 iv1
->no_overflow
= true;
856 /* Add an assumption to NITER that a loop whose ending condition
857 is IV0 < IV1 rolls. TYPE is the type of the control iv. BNDS
858 bounds the value of IV1->base - IV0->base. */
861 assert_loop_rolls_lt (tree type
, affine_iv
*iv0
, affine_iv
*iv1
,
862 struct tree_niter_desc
*niter
, bounds
*bnds
)
864 tree assumption
= boolean_true_node
, bound
, diff
;
865 tree mbz
, mbzl
, mbzr
, type1
;
866 bool rolls_p
, no_overflow_p
;
870 /* We are going to compute the number of iterations as
871 (iv1->base - iv0->base + step - 1) / step, computed in the unsigned
872 variant of TYPE. This formula only works if
874 -step + 1 <= (iv1->base - iv0->base) <= MAX - step + 1
876 (where MAX is the maximum value of the unsigned variant of TYPE, and
877 the computations in this formula are performed in full precision
880 Usually, for loops with exit condition iv0->base + step * i < iv1->base,
881 we have a condition of form iv0->base - step < iv1->base before the loop,
882 and for loops iv0->base < iv1->base - step * i the condition
883 iv0->base < iv1->base + step, due to loop header copying, which enable us
884 to prove the lower bound.
886 The upper bound is more complicated. Unless the expressions for initial
887 and final value themselves contain enough information, we usually cannot
888 derive it from the context. */
890 /* First check whether the answer does not follow from the bounds we gathered
892 if (integer_nonzerop (iv0
->step
))
893 dstep
= tree_to_double_int (iv0
->step
);
896 dstep
= double_int_sext (tree_to_double_int (iv1
->step
),
897 TYPE_PRECISION (type
));
898 dstep
= double_int_neg (dstep
);
902 mpz_set_double_int (mstep
, dstep
, true);
903 mpz_neg (mstep
, mstep
);
904 mpz_add_ui (mstep
, mstep
, 1);
906 rolls_p
= mpz_cmp (mstep
, bnds
->below
) <= 0;
909 mpz_set_double_int (max
, double_int_mask (TYPE_PRECISION (type
)), true);
910 mpz_add (max
, max
, mstep
);
911 no_overflow_p
= (mpz_cmp (bnds
->up
, max
) <= 0
912 /* For pointers, only values lying inside a single object
913 can be compared or manipulated by pointer arithmetics.
914 Gcc in general does not allow or handle objects larger
915 than half of the address space, hence the upper bound
916 is satisfied for pointers. */
917 || POINTER_TYPE_P (type
));
921 if (rolls_p
&& no_overflow_p
)
925 if (POINTER_TYPE_P (type
))
928 /* Now the hard part; we must formulate the assumption(s) as expressions, and
929 we must be careful not to introduce overflow. */
931 if (integer_nonzerop (iv0
->step
))
933 diff
= fold_build2 (MINUS_EXPR
, type1
,
934 iv0
->step
, build_int_cst (type1
, 1));
936 /* We need to know that iv0->base >= MIN + iv0->step - 1. Since
937 0 address never belongs to any object, we can assume this for
939 if (!POINTER_TYPE_P (type
))
941 bound
= fold_build2 (PLUS_EXPR
, type1
,
942 TYPE_MIN_VALUE (type
), diff
);
943 assumption
= fold_build2 (GE_EXPR
, boolean_type_node
,
947 /* And then we can compute iv0->base - diff, and compare it with
949 mbzl
= fold_build2 (MINUS_EXPR
, type1
,
950 fold_convert (type1
, iv0
->base
), diff
);
951 mbzr
= fold_convert (type1
, iv1
->base
);
955 diff
= fold_build2 (PLUS_EXPR
, type1
,
956 iv1
->step
, build_int_cst (type1
, 1));
958 if (!POINTER_TYPE_P (type
))
960 bound
= fold_build2 (PLUS_EXPR
, type1
,
961 TYPE_MAX_VALUE (type
), diff
);
962 assumption
= fold_build2 (LE_EXPR
, boolean_type_node
,
966 mbzl
= fold_convert (type1
, iv0
->base
);
967 mbzr
= fold_build2 (MINUS_EXPR
, type1
,
968 fold_convert (type1
, iv1
->base
), diff
);
971 if (!integer_nonzerop (assumption
))
972 niter
->assumptions
= fold_build2 (TRUTH_AND_EXPR
, boolean_type_node
,
973 niter
->assumptions
, assumption
);
976 mbz
= fold_build2 (GT_EXPR
, boolean_type_node
, mbzl
, mbzr
);
977 niter
->may_be_zero
= fold_build2 (TRUTH_OR_EXPR
, boolean_type_node
,
978 niter
->may_be_zero
, mbz
);
982 /* Determines number of iterations of loop whose ending condition
983 is IV0 < IV1. TYPE is the type of the iv. The number of
984 iterations is stored to NITER. BNDS bounds the difference
985 IV1->base - IV0->base. EXIT_MUST_BE_TAKEN is true if we know
986 that the exit must be taken eventually. */
989 number_of_iterations_lt (tree type
, affine_iv
*iv0
, affine_iv
*iv1
,
990 struct tree_niter_desc
*niter
,
991 bool exit_must_be_taken
, bounds
*bnds
)
993 tree niter_type
= unsigned_type_for (type
);
997 if (integer_nonzerop (iv0
->step
))
999 niter
->control
= *iv0
;
1000 niter
->cmp
= LT_EXPR
;
1001 niter
->bound
= iv1
->base
;
1005 niter
->control
= *iv1
;
1006 niter
->cmp
= GT_EXPR
;
1007 niter
->bound
= iv0
->base
;
1010 delta
= fold_build2 (MINUS_EXPR
, niter_type
,
1011 fold_convert (niter_type
, iv1
->base
),
1012 fold_convert (niter_type
, iv0
->base
));
1014 /* First handle the special case that the step is +-1. */
1015 if ((integer_onep (iv0
->step
) && integer_zerop (iv1
->step
))
1016 || (integer_all_onesp (iv1
->step
) && integer_zerop (iv0
->step
)))
1018 /* for (i = iv0->base; i < iv1->base; i++)
1022 for (i = iv1->base; i > iv0->base; i--).
1024 In both cases # of iterations is iv1->base - iv0->base, assuming that
1025 iv1->base >= iv0->base.
1027 First try to derive a lower bound on the value of
1028 iv1->base - iv0->base, computed in full precision. If the difference
1029 is nonnegative, we are done, otherwise we must record the
1032 if (mpz_sgn (bnds
->below
) < 0)
1033 niter
->may_be_zero
= fold_build2 (LT_EXPR
, boolean_type_node
,
1034 iv1
->base
, iv0
->base
);
1035 niter
->niter
= delta
;
1036 niter
->max
= mpz_get_double_int (niter_type
, bnds
->up
, false);
1040 if (integer_nonzerop (iv0
->step
))
1041 step
= fold_convert (niter_type
, iv0
->step
);
1043 step
= fold_convert (niter_type
,
1044 fold_build1 (NEGATE_EXPR
, type
, iv1
->step
));
1046 /* If we can determine the final value of the control iv exactly, we can
1047 transform the condition to != comparison. In particular, this will be
1048 the case if DELTA is constant. */
1049 if (number_of_iterations_lt_to_ne (type
, iv0
, iv1
, niter
, &delta
, step
,
1050 exit_must_be_taken
, bnds
))
1054 zps
.base
= build_int_cst (niter_type
, 0);
1056 /* number_of_iterations_lt_to_ne will add assumptions that ensure that
1057 zps does not overflow. */
1058 zps
.no_overflow
= true;
1060 return number_of_iterations_ne (type
, &zps
, delta
, niter
, true, bnds
);
1063 /* Make sure that the control iv does not overflow. */
1064 if (!assert_no_overflow_lt (type
, iv0
, iv1
, niter
, step
))
1067 /* We determine the number of iterations as (delta + step - 1) / step. For
1068 this to work, we must know that iv1->base >= iv0->base - step + 1,
1069 otherwise the loop does not roll. */
1070 assert_loop_rolls_lt (type
, iv0
, iv1
, niter
, bnds
);
1072 s
= fold_build2 (MINUS_EXPR
, niter_type
,
1073 step
, build_int_cst (niter_type
, 1));
1074 delta
= fold_build2 (PLUS_EXPR
, niter_type
, delta
, s
);
1075 niter
->niter
= fold_build2 (FLOOR_DIV_EXPR
, niter_type
, delta
, step
);
1079 mpz_set_double_int (mstep
, tree_to_double_int (step
), true);
1080 mpz_add (tmp
, bnds
->up
, mstep
);
1081 mpz_sub_ui (tmp
, tmp
, 1);
1082 mpz_fdiv_q (tmp
, tmp
, mstep
);
1083 niter
->max
= mpz_get_double_int (niter_type
, tmp
, false);
1090 /* Determines number of iterations of loop whose ending condition
1091 is IV0 <= IV1. TYPE is the type of the iv. The number of
1092 iterations is stored to NITER. EXIT_MUST_BE_TAKEN is true if
1093 we know that this condition must eventually become false (we derived this
1094 earlier, and possibly set NITER->assumptions to make sure this
1095 is the case). BNDS bounds the difference IV1->base - IV0->base. */
1098 number_of_iterations_le (tree type
, affine_iv
*iv0
, affine_iv
*iv1
,
1099 struct tree_niter_desc
*niter
, bool exit_must_be_taken
,
1104 if (POINTER_TYPE_P (type
))
1107 /* Say that IV0 is the control variable. Then IV0 <= IV1 iff
1108 IV0 < IV1 + 1, assuming that IV1 is not equal to the greatest
1109 value of the type. This we must know anyway, since if it is
1110 equal to this value, the loop rolls forever. We do not check
1111 this condition for pointer type ivs, as the code cannot rely on
1112 the object to that the pointer points being placed at the end of
1113 the address space (and more pragmatically, TYPE_{MIN,MAX}_VALUE is
1114 not defined for pointers). */
1116 if (!exit_must_be_taken
&& !POINTER_TYPE_P (type
))
1118 if (integer_nonzerop (iv0
->step
))
1119 assumption
= fold_build2 (NE_EXPR
, boolean_type_node
,
1120 iv1
->base
, TYPE_MAX_VALUE (type
));
1122 assumption
= fold_build2 (NE_EXPR
, boolean_type_node
,
1123 iv0
->base
, TYPE_MIN_VALUE (type
));
1125 if (integer_zerop (assumption
))
1127 if (!integer_nonzerop (assumption
))
1128 niter
->assumptions
= fold_build2 (TRUTH_AND_EXPR
, boolean_type_node
,
1129 niter
->assumptions
, assumption
);
1132 if (integer_nonzerop (iv0
->step
))
1134 if (POINTER_TYPE_P (type
))
1135 iv1
->base
= fold_build2 (POINTER_PLUS_EXPR
, type
, iv1
->base
,
1136 build_int_cst (type1
, 1));
1138 iv1
->base
= fold_build2 (PLUS_EXPR
, type1
, iv1
->base
,
1139 build_int_cst (type1
, 1));
1141 else if (POINTER_TYPE_P (type
))
1142 iv0
->base
= fold_build2 (POINTER_PLUS_EXPR
, type
, iv0
->base
,
1143 fold_build1 (NEGATE_EXPR
, type1
,
1144 build_int_cst (type1
, 1)));
1146 iv0
->base
= fold_build2 (MINUS_EXPR
, type1
,
1147 iv0
->base
, build_int_cst (type1
, 1));
1149 bounds_add (bnds
, double_int_one
, type1
);
1151 return number_of_iterations_lt (type
, iv0
, iv1
, niter
, exit_must_be_taken
,
1155 /* Dumps description of affine induction variable IV to FILE. */
1158 dump_affine_iv (FILE *file
, affine_iv
*iv
)
1160 if (!integer_zerop (iv
->step
))
1161 fprintf (file
, "[");
1163 print_generic_expr (dump_file
, iv
->base
, TDF_SLIM
);
1165 if (!integer_zerop (iv
->step
))
1167 fprintf (file
, ", + , ");
1168 print_generic_expr (dump_file
, iv
->step
, TDF_SLIM
);
1169 fprintf (file
, "]%s", iv
->no_overflow
? "(no_overflow)" : "");
1173 /* Determine the number of iterations according to condition (for staying
1174 inside loop) which compares two induction variables using comparison
1175 operator CODE. The induction variable on left side of the comparison
1176 is IV0, the right-hand side is IV1. Both induction variables must have
1177 type TYPE, which must be an integer or pointer type. The steps of the
1178 ivs must be constants (or NULL_TREE, which is interpreted as constant zero).
1180 LOOP is the loop whose number of iterations we are determining.
1182 ONLY_EXIT is true if we are sure this is the only way the loop could be
1183 exited (including possibly non-returning function calls, exceptions, etc.)
1184 -- in this case we can use the information whether the control induction
1185 variables can overflow or not in a more efficient way.
1187 The results (number of iterations and assumptions as described in
1188 comments at struct tree_niter_desc in tree-flow.h) are stored to NITER.
1189 Returns false if it fails to determine number of iterations, true if it
1190 was determined (possibly with some assumptions). */
1193 number_of_iterations_cond (struct loop
*loop
,
1194 tree type
, affine_iv
*iv0
, enum tree_code code
,
1195 affine_iv
*iv1
, struct tree_niter_desc
*niter
,
1198 bool exit_must_be_taken
= false, ret
;
1201 /* The meaning of these assumptions is this:
1203 then the rest of information does not have to be valid
1204 if may_be_zero then the loop does not roll, even if
1206 niter
->assumptions
= boolean_true_node
;
1207 niter
->may_be_zero
= boolean_false_node
;
1208 niter
->niter
= NULL_TREE
;
1209 niter
->max
= double_int_zero
;
1211 niter
->bound
= NULL_TREE
;
1212 niter
->cmp
= ERROR_MARK
;
1214 /* Make < comparison from > ones, and for NE_EXPR comparisons, ensure that
1215 the control variable is on lhs. */
1216 if (code
== GE_EXPR
|| code
== GT_EXPR
1217 || (code
== NE_EXPR
&& integer_zerop (iv0
->step
)))
1220 code
= swap_tree_comparison (code
);
1223 if (POINTER_TYPE_P (type
))
1225 /* Comparison of pointers is undefined unless both iv0 and iv1 point
1226 to the same object. If they do, the control variable cannot wrap
1227 (as wrap around the bounds of memory will never return a pointer
1228 that would be guaranteed to point to the same object, even if we
1229 avoid undefined behavior by casting to size_t and back). */
1230 iv0
->no_overflow
= true;
1231 iv1
->no_overflow
= true;
1234 /* If the control induction variable does not overflow and the only exit
1235 from the loop is the one that we analyze, we know it must be taken
1239 if (!integer_zerop (iv0
->step
) && iv0
->no_overflow
)
1240 exit_must_be_taken
= true;
1241 else if (!integer_zerop (iv1
->step
) && iv1
->no_overflow
)
1242 exit_must_be_taken
= true;
1245 /* We can handle the case when neither of the sides of the comparison is
1246 invariant, provided that the test is NE_EXPR. This rarely occurs in
1247 practice, but it is simple enough to manage. */
1248 if (!integer_zerop (iv0
->step
) && !integer_zerop (iv1
->step
))
1250 if (code
!= NE_EXPR
)
1253 iv0
->step
= fold_binary_to_constant (MINUS_EXPR
, type
,
1254 iv0
->step
, iv1
->step
);
1255 iv0
->no_overflow
= false;
1256 iv1
->step
= build_int_cst (type
, 0);
1257 iv1
->no_overflow
= true;
1260 /* If the result of the comparison is a constant, the loop is weird. More
1261 precise handling would be possible, but the situation is not common enough
1262 to waste time on it. */
1263 if (integer_zerop (iv0
->step
) && integer_zerop (iv1
->step
))
1266 /* Ignore loops of while (i-- < 10) type. */
1267 if (code
!= NE_EXPR
)
1269 if (iv0
->step
&& tree_int_cst_sign_bit (iv0
->step
))
1272 if (!integer_zerop (iv1
->step
) && !tree_int_cst_sign_bit (iv1
->step
))
1276 /* If the loop exits immediately, there is nothing to do. */
1277 if (integer_zerop (fold_build2 (code
, boolean_type_node
, iv0
->base
, iv1
->base
)))
1279 niter
->niter
= build_int_cst (unsigned_type_for (type
), 0);
1280 niter
->max
= double_int_zero
;
1284 /* OK, now we know we have a senseful loop. Handle several cases, depending
1285 on what comparison operator is used. */
1286 bound_difference (loop
, iv1
->base
, iv0
->base
, &bnds
);
1288 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1291 "Analyzing # of iterations of loop %d\n", loop
->num
);
1293 fprintf (dump_file
, " exit condition ");
1294 dump_affine_iv (dump_file
, iv0
);
1295 fprintf (dump_file
, " %s ",
1296 code
== NE_EXPR
? "!="
1297 : code
== LT_EXPR
? "<"
1299 dump_affine_iv (dump_file
, iv1
);
1300 fprintf (dump_file
, "\n");
1302 fprintf (dump_file
, " bounds on difference of bases: ");
1303 mpz_out_str (dump_file
, 10, bnds
.below
);
1304 fprintf (dump_file
, " ... ");
1305 mpz_out_str (dump_file
, 10, bnds
.up
);
1306 fprintf (dump_file
, "\n");
1312 gcc_assert (integer_zerop (iv1
->step
));
1313 ret
= number_of_iterations_ne (type
, iv0
, iv1
->base
, niter
,
1314 exit_must_be_taken
, &bnds
);
1318 ret
= number_of_iterations_lt (type
, iv0
, iv1
, niter
, exit_must_be_taken
,
1323 ret
= number_of_iterations_le (type
, iv0
, iv1
, niter
, exit_must_be_taken
,
1331 mpz_clear (bnds
.up
);
1332 mpz_clear (bnds
.below
);
1334 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1338 fprintf (dump_file
, " result:\n");
1339 if (!integer_nonzerop (niter
->assumptions
))
1341 fprintf (dump_file
, " under assumptions ");
1342 print_generic_expr (dump_file
, niter
->assumptions
, TDF_SLIM
);
1343 fprintf (dump_file
, "\n");
1346 if (!integer_zerop (niter
->may_be_zero
))
1348 fprintf (dump_file
, " zero if ");
1349 print_generic_expr (dump_file
, niter
->may_be_zero
, TDF_SLIM
);
1350 fprintf (dump_file
, "\n");
1353 fprintf (dump_file
, " # of iterations ");
1354 print_generic_expr (dump_file
, niter
->niter
, TDF_SLIM
);
1355 fprintf (dump_file
, ", bounded by ");
1356 dump_double_int (dump_file
, niter
->max
, true);
1357 fprintf (dump_file
, "\n");
1360 fprintf (dump_file
, " failed\n\n");
1365 /* Substitute NEW for OLD in EXPR and fold the result. */
1368 simplify_replace_tree (tree expr
, tree old
, tree new_tree
)
1371 tree ret
= NULL_TREE
, e
, se
;
1377 || operand_equal_p (expr
, old
, 0))
1378 return unshare_expr (new_tree
);
1383 n
= TREE_OPERAND_LENGTH (expr
);
1384 for (i
= 0; i
< n
; i
++)
1386 e
= TREE_OPERAND (expr
, i
);
1387 se
= simplify_replace_tree (e
, old
, new_tree
);
1392 ret
= copy_node (expr
);
1394 TREE_OPERAND (ret
, i
) = se
;
1397 return (ret
? fold (ret
) : expr
);
1400 /* Expand definitions of ssa names in EXPR as long as they are simple
1401 enough, and return the new expression. */
1404 expand_simple_operations (tree expr
)
1407 tree ret
= NULL_TREE
, e
, ee
, e1
;
1408 enum tree_code code
;
1411 if (expr
== NULL_TREE
)
1414 if (is_gimple_min_invariant (expr
))
1417 code
= TREE_CODE (expr
);
1418 if (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (code
)))
1420 n
= TREE_OPERAND_LENGTH (expr
);
1421 for (i
= 0; i
< n
; i
++)
1423 e
= TREE_OPERAND (expr
, i
);
1424 ee
= expand_simple_operations (e
);
1429 ret
= copy_node (expr
);
1431 TREE_OPERAND (ret
, i
) = ee
;
1437 fold_defer_overflow_warnings ();
1439 fold_undefer_and_ignore_overflow_warnings ();
1443 if (TREE_CODE (expr
) != SSA_NAME
)
1446 stmt
= SSA_NAME_DEF_STMT (expr
);
1447 if (gimple_code (stmt
) == GIMPLE_PHI
)
1449 basic_block src
, dest
;
1451 if (gimple_phi_num_args (stmt
) != 1)
1453 e
= PHI_ARG_DEF (stmt
, 0);
1455 /* Avoid propagating through loop exit phi nodes, which
1456 could break loop-closed SSA form restrictions. */
1457 dest
= gimple_bb (stmt
);
1458 src
= single_pred (dest
);
1459 if (TREE_CODE (e
) == SSA_NAME
1460 && src
->loop_father
!= dest
->loop_father
)
1463 return expand_simple_operations (e
);
1465 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
1468 e
= gimple_assign_rhs1 (stmt
);
1469 code
= gimple_assign_rhs_code (stmt
);
1470 if (get_gimple_rhs_class (code
) == GIMPLE_SINGLE_RHS
)
1472 if (is_gimple_min_invariant (e
))
1475 if (code
== SSA_NAME
)
1476 return expand_simple_operations (e
);
1484 /* Casts are simple. */
1485 ee
= expand_simple_operations (e
);
1486 return fold_build1 (code
, TREE_TYPE (expr
), ee
);
1490 case POINTER_PLUS_EXPR
:
1491 /* And increments and decrements by a constant are simple. */
1492 e1
= gimple_assign_rhs2 (stmt
);
1493 if (!is_gimple_min_invariant (e1
))
1496 ee
= expand_simple_operations (e
);
1497 return fold_build2 (code
, TREE_TYPE (expr
), ee
, e1
);
1504 /* Tries to simplify EXPR using the condition COND. Returns the simplified
1505 expression (or EXPR unchanged, if no simplification was possible). */
1508 tree_simplify_using_condition_1 (tree cond
, tree expr
)
1511 tree e
, te
, e0
, e1
, e2
, notcond
;
1512 enum tree_code code
= TREE_CODE (expr
);
1514 if (code
== INTEGER_CST
)
1517 if (code
== TRUTH_OR_EXPR
1518 || code
== TRUTH_AND_EXPR
1519 || code
== COND_EXPR
)
1523 e0
= tree_simplify_using_condition_1 (cond
, TREE_OPERAND (expr
, 0));
1524 if (TREE_OPERAND (expr
, 0) != e0
)
1527 e1
= tree_simplify_using_condition_1 (cond
, TREE_OPERAND (expr
, 1));
1528 if (TREE_OPERAND (expr
, 1) != e1
)
1531 if (code
== COND_EXPR
)
1533 e2
= tree_simplify_using_condition_1 (cond
, TREE_OPERAND (expr
, 2));
1534 if (TREE_OPERAND (expr
, 2) != e2
)
1542 if (code
== COND_EXPR
)
1543 expr
= fold_build3 (code
, boolean_type_node
, e0
, e1
, e2
);
1545 expr
= fold_build2 (code
, boolean_type_node
, e0
, e1
);
1551 /* In case COND is equality, we may be able to simplify EXPR by copy/constant
1552 propagation, and vice versa. Fold does not handle this, since it is
1553 considered too expensive. */
1554 if (TREE_CODE (cond
) == EQ_EXPR
)
1556 e0
= TREE_OPERAND (cond
, 0);
1557 e1
= TREE_OPERAND (cond
, 1);
1559 /* We know that e0 == e1. Check whether we cannot simplify expr
1561 e
= simplify_replace_tree (expr
, e0
, e1
);
1562 if (integer_zerop (e
) || integer_nonzerop (e
))
1565 e
= simplify_replace_tree (expr
, e1
, e0
);
1566 if (integer_zerop (e
) || integer_nonzerop (e
))
1569 if (TREE_CODE (expr
) == EQ_EXPR
)
1571 e0
= TREE_OPERAND (expr
, 0);
1572 e1
= TREE_OPERAND (expr
, 1);
1574 /* If e0 == e1 (EXPR) implies !COND, then EXPR cannot be true. */
1575 e
= simplify_replace_tree (cond
, e0
, e1
);
1576 if (integer_zerop (e
))
1578 e
= simplify_replace_tree (cond
, e1
, e0
);
1579 if (integer_zerop (e
))
1582 if (TREE_CODE (expr
) == NE_EXPR
)
1584 e0
= TREE_OPERAND (expr
, 0);
1585 e1
= TREE_OPERAND (expr
, 1);
1587 /* If e0 == e1 (!EXPR) implies !COND, then EXPR must be true. */
1588 e
= simplify_replace_tree (cond
, e0
, e1
);
1589 if (integer_zerop (e
))
1590 return boolean_true_node
;
1591 e
= simplify_replace_tree (cond
, e1
, e0
);
1592 if (integer_zerop (e
))
1593 return boolean_true_node
;
1596 te
= expand_simple_operations (expr
);
1598 /* Check whether COND ==> EXPR. */
1599 notcond
= invert_truthvalue (cond
);
1600 e
= fold_binary (TRUTH_OR_EXPR
, boolean_type_node
, notcond
, te
);
1601 if (e
&& integer_nonzerop (e
))
1604 /* Check whether COND ==> not EXPR. */
1605 e
= fold_binary (TRUTH_AND_EXPR
, boolean_type_node
, cond
, te
);
1606 if (e
&& integer_zerop (e
))
1612 /* Tries to simplify EXPR using the condition COND. Returns the simplified
1613 expression (or EXPR unchanged, if no simplification was possible).
1614 Wrapper around tree_simplify_using_condition_1 that ensures that chains
1615 of simple operations in definitions of ssa names in COND are expanded,
1616 so that things like casts or incrementing the value of the bound before
1617 the loop do not cause us to fail. */
1620 tree_simplify_using_condition (tree cond
, tree expr
)
1622 cond
= expand_simple_operations (cond
);
1624 return tree_simplify_using_condition_1 (cond
, expr
);
1627 /* Tries to simplify EXPR using the conditions on entry to LOOP.
1628 Returns the simplified expression (or EXPR unchanged, if no
1629 simplification was possible).*/
1632 simplify_using_initial_conditions (struct loop
*loop
, tree expr
)
1640 if (TREE_CODE (expr
) == INTEGER_CST
)
1643 /* Limit walking the dominators to avoid quadraticness in
1644 the number of BBs times the number of loops in degenerate
1646 for (bb
= loop
->header
;
1647 bb
!= ENTRY_BLOCK_PTR
&& cnt
< MAX_DOMINATORS_TO_WALK
;
1648 bb
= get_immediate_dominator (CDI_DOMINATORS
, bb
))
1650 if (!single_pred_p (bb
))
1652 e
= single_pred_edge (bb
);
1654 if (!(e
->flags
& (EDGE_TRUE_VALUE
| EDGE_FALSE_VALUE
)))
1657 stmt
= last_stmt (e
->src
);
1658 cond
= fold_build2 (gimple_cond_code (stmt
),
1660 gimple_cond_lhs (stmt
),
1661 gimple_cond_rhs (stmt
));
1662 if (e
->flags
& EDGE_FALSE_VALUE
)
1663 cond
= invert_truthvalue (cond
);
1664 expr
= tree_simplify_using_condition (cond
, expr
);
1671 /* Tries to simplify EXPR using the evolutions of the loop invariants
1672 in the superloops of LOOP. Returns the simplified expression
1673 (or EXPR unchanged, if no simplification was possible). */
1676 simplify_using_outer_evolutions (struct loop
*loop
, tree expr
)
1678 enum tree_code code
= TREE_CODE (expr
);
1682 if (is_gimple_min_invariant (expr
))
1685 if (code
== TRUTH_OR_EXPR
1686 || code
== TRUTH_AND_EXPR
1687 || code
== COND_EXPR
)
1691 e0
= simplify_using_outer_evolutions (loop
, TREE_OPERAND (expr
, 0));
1692 if (TREE_OPERAND (expr
, 0) != e0
)
1695 e1
= simplify_using_outer_evolutions (loop
, TREE_OPERAND (expr
, 1));
1696 if (TREE_OPERAND (expr
, 1) != e1
)
1699 if (code
== COND_EXPR
)
1701 e2
= simplify_using_outer_evolutions (loop
, TREE_OPERAND (expr
, 2));
1702 if (TREE_OPERAND (expr
, 2) != e2
)
1710 if (code
== COND_EXPR
)
1711 expr
= fold_build3 (code
, boolean_type_node
, e0
, e1
, e2
);
1713 expr
= fold_build2 (code
, boolean_type_node
, e0
, e1
);
1719 e
= instantiate_parameters (loop
, expr
);
1720 if (is_gimple_min_invariant (e
))
1726 /* Returns true if EXIT is the only possible exit from LOOP. */
1729 loop_only_exit_p (const struct loop
*loop
, const_edge exit
)
1732 gimple_stmt_iterator bsi
;
1736 if (exit
!= single_exit (loop
))
1739 body
= get_loop_body (loop
);
1740 for (i
= 0; i
< loop
->num_nodes
; i
++)
1742 for (bsi
= gsi_start_bb (body
[i
]); !gsi_end_p (bsi
); gsi_next (&bsi
))
1744 call
= gsi_stmt (bsi
);
1745 if (gimple_code (call
) != GIMPLE_CALL
)
1748 if (gimple_has_side_effects (call
))
1760 /* Stores description of number of iterations of LOOP derived from
1761 EXIT (an exit edge of the LOOP) in NITER. Returns true if some
1762 useful information could be derived (and fields of NITER has
1763 meaning described in comments at struct tree_niter_desc
1764 declaration), false otherwise. If WARN is true and
1765 -Wunsafe-loop-optimizations was given, warn if the optimizer is going to use
1766 potentially unsafe assumptions. */
1769 number_of_iterations_exit (struct loop
*loop
, edge exit
,
1770 struct tree_niter_desc
*niter
,
1776 enum tree_code code
;
1779 if (!dominated_by_p (CDI_DOMINATORS
, loop
->latch
, exit
->src
))
1782 niter
->assumptions
= boolean_false_node
;
1783 stmt
= last_stmt (exit
->src
);
1784 if (!stmt
|| gimple_code (stmt
) != GIMPLE_COND
)
1787 /* We want the condition for staying inside loop. */
1788 code
= gimple_cond_code (stmt
);
1789 if (exit
->flags
& EDGE_TRUE_VALUE
)
1790 code
= invert_tree_comparison (code
, false);
1805 op0
= gimple_cond_lhs (stmt
);
1806 op1
= gimple_cond_rhs (stmt
);
1807 type
= TREE_TYPE (op0
);
1809 if (TREE_CODE (type
) != INTEGER_TYPE
1810 && !POINTER_TYPE_P (type
))
1813 if (!simple_iv (loop
, loop_containing_stmt (stmt
), op0
, &iv0
, false))
1815 if (!simple_iv (loop
, loop_containing_stmt (stmt
), op1
, &iv1
, false))
1818 /* We don't want to see undefined signed overflow warnings while
1819 computing the number of iterations. */
1820 fold_defer_overflow_warnings ();
1822 iv0
.base
= expand_simple_operations (iv0
.base
);
1823 iv1
.base
= expand_simple_operations (iv1
.base
);
1824 if (!number_of_iterations_cond (loop
, type
, &iv0
, code
, &iv1
, niter
,
1825 loop_only_exit_p (loop
, exit
)))
1827 fold_undefer_and_ignore_overflow_warnings ();
1833 niter
->assumptions
= simplify_using_outer_evolutions (loop
,
1834 niter
->assumptions
);
1835 niter
->may_be_zero
= simplify_using_outer_evolutions (loop
,
1836 niter
->may_be_zero
);
1837 niter
->niter
= simplify_using_outer_evolutions (loop
, niter
->niter
);
1841 = simplify_using_initial_conditions (loop
,
1842 niter
->assumptions
);
1844 = simplify_using_initial_conditions (loop
,
1845 niter
->may_be_zero
);
1847 fold_undefer_and_ignore_overflow_warnings ();
1849 if (integer_onep (niter
->assumptions
))
1852 /* With -funsafe-loop-optimizations we assume that nothing bad can happen.
1853 But if we can prove that there is overflow or some other source of weird
1854 behavior, ignore the loop even with -funsafe-loop-optimizations. */
1855 if (integer_zerop (niter
->assumptions
))
1858 if (flag_unsafe_loop_optimizations
)
1859 niter
->assumptions
= boolean_true_node
;
1863 const char *wording
;
1864 location_t loc
= gimple_location (stmt
);
1866 /* We can provide a more specific warning if one of the operator is
1867 constant and the other advances by +1 or -1. */
1868 if (!integer_zerop (iv1
.step
)
1869 ? (integer_zerop (iv0
.step
)
1870 && (integer_onep (iv1
.step
) || integer_all_onesp (iv1
.step
)))
1871 : (integer_onep (iv0
.step
) || integer_all_onesp (iv0
.step
)))
1873 flag_unsafe_loop_optimizations
1874 ? N_("assuming that the loop is not infinite")
1875 : N_("cannot optimize possibly infinite loops");
1878 flag_unsafe_loop_optimizations
1879 ? N_("assuming that the loop counter does not overflow")
1880 : N_("cannot optimize loop, the loop counter may overflow");
1882 warning_at ((LOCATION_LINE (loc
) > 0) ? loc
: input_location
,
1883 OPT_Wunsafe_loop_optimizations
, "%s", gettext (wording
));
1886 return flag_unsafe_loop_optimizations
;
1889 /* Try to determine the number of iterations of LOOP. If we succeed,
1890 expression giving number of iterations is returned and *EXIT is
1891 set to the edge from that the information is obtained. Otherwise
1892 chrec_dont_know is returned. */
1895 find_loop_niter (struct loop
*loop
, edge
*exit
)
1898 VEC (edge
, heap
) *exits
= get_loop_exit_edges (loop
);
1900 tree niter
= NULL_TREE
, aniter
;
1901 struct tree_niter_desc desc
;
1904 for (i
= 0; VEC_iterate (edge
, exits
, i
, ex
); i
++)
1906 if (!just_once_each_iteration_p (loop
, ex
->src
))
1909 if (!number_of_iterations_exit (loop
, ex
, &desc
, false))
1912 if (integer_nonzerop (desc
.may_be_zero
))
1914 /* We exit in the first iteration through this exit.
1915 We won't find anything better. */
1916 niter
= build_int_cst (unsigned_type_node
, 0);
1921 if (!integer_zerop (desc
.may_be_zero
))
1924 aniter
= desc
.niter
;
1928 /* Nothing recorded yet. */
1934 /* Prefer constants, the lower the better. */
1935 if (TREE_CODE (aniter
) != INTEGER_CST
)
1938 if (TREE_CODE (niter
) != INTEGER_CST
)
1945 if (tree_int_cst_lt (aniter
, niter
))
1952 VEC_free (edge
, heap
, exits
);
1954 return niter
? niter
: chrec_dont_know
;
1957 /* Return true if loop is known to have bounded number of iterations. */
1960 finite_loop_p (struct loop
*loop
)
1963 VEC (edge
, heap
) *exits
= get_loop_exit_edges (loop
);
1965 struct tree_niter_desc desc
;
1966 bool finite
= false;
1968 if (flag_unsafe_loop_optimizations
)
1970 if ((TREE_READONLY (current_function_decl
)
1971 || DECL_PURE_P (current_function_decl
))
1972 && !DECL_LOOPING_CONST_OR_PURE_P (current_function_decl
))
1974 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1975 fprintf (dump_file
, "Found loop %i to be finite: it is within pure or const function.\n",
1980 exits
= get_loop_exit_edges (loop
);
1981 for (i
= 0; VEC_iterate (edge
, exits
, i
, ex
); i
++)
1983 if (!just_once_each_iteration_p (loop
, ex
->src
))
1986 if (number_of_iterations_exit (loop
, ex
, &desc
, false))
1988 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1990 fprintf (dump_file
, "Found loop %i to be finite: iterating ", loop
->num
);
1991 print_generic_expr (dump_file
, desc
.niter
, TDF_SLIM
);
1992 fprintf (dump_file
, " times\n");
1998 VEC_free (edge
, heap
, exits
);
2004 Analysis of a number of iterations of a loop by a brute-force evaluation.
2008 /* Bound on the number of iterations we try to evaluate. */
2010 #define MAX_ITERATIONS_TO_TRACK \
2011 ((unsigned) PARAM_VALUE (PARAM_MAX_ITERATIONS_TO_TRACK))
2013 /* Returns the loop phi node of LOOP such that ssa name X is derived from its
2014 result by a chain of operations such that all but exactly one of their
2015 operands are constants. */
2018 chain_of_csts_start (struct loop
*loop
, tree x
)
2020 gimple stmt
= SSA_NAME_DEF_STMT (x
);
2022 basic_block bb
= gimple_bb (stmt
);
2023 enum tree_code code
;
2026 || !flow_bb_inside_loop_p (loop
, bb
))
2029 if (gimple_code (stmt
) == GIMPLE_PHI
)
2031 if (bb
== loop
->header
)
2037 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
2040 code
= gimple_assign_rhs_code (stmt
);
2041 if (gimple_references_memory_p (stmt
)
2042 || TREE_CODE_CLASS (code
) == tcc_reference
2043 || (code
== ADDR_EXPR
2044 && !is_gimple_min_invariant (gimple_assign_rhs1 (stmt
))))
2047 use
= SINGLE_SSA_TREE_OPERAND (stmt
, SSA_OP_USE
);
2048 if (use
== NULL_TREE
)
2051 return chain_of_csts_start (loop
, use
);
2054 /* Determines whether the expression X is derived from a result of a phi node
2055 in header of LOOP such that
2057 * the derivation of X consists only from operations with constants
2058 * the initial value of the phi node is constant
2059 * the value of the phi node in the next iteration can be derived from the
2060 value in the current iteration by a chain of operations with constants.
2062 If such phi node exists, it is returned, otherwise NULL is returned. */
2065 get_base_for (struct loop
*loop
, tree x
)
2070 if (is_gimple_min_invariant (x
))
2073 phi
= chain_of_csts_start (loop
, x
);
2077 init
= PHI_ARG_DEF_FROM_EDGE (phi
, loop_preheader_edge (loop
));
2078 next
= PHI_ARG_DEF_FROM_EDGE (phi
, loop_latch_edge (loop
));
2080 if (TREE_CODE (next
) != SSA_NAME
)
2083 if (!is_gimple_min_invariant (init
))
2086 if (chain_of_csts_start (loop
, next
) != phi
)
2092 /* Given an expression X, then
2094 * if X is NULL_TREE, we return the constant BASE.
2095 * otherwise X is a SSA name, whose value in the considered loop is derived
2096 by a chain of operations with constant from a result of a phi node in
2097 the header of the loop. Then we return value of X when the value of the
2098 result of this phi node is given by the constant BASE. */
2101 get_val_for (tree x
, tree base
)
2105 gcc_assert (is_gimple_min_invariant (base
));
2110 stmt
= SSA_NAME_DEF_STMT (x
);
2111 if (gimple_code (stmt
) == GIMPLE_PHI
)
2114 gcc_assert (is_gimple_assign (stmt
));
2116 /* STMT must be either an assignment of a single SSA name or an
2117 expression involving an SSA name and a constant. Try to fold that
2118 expression using the value for the SSA name. */
2119 if (gimple_assign_ssa_name_copy_p (stmt
))
2120 return get_val_for (gimple_assign_rhs1 (stmt
), base
);
2121 else if (gimple_assign_rhs_class (stmt
) == GIMPLE_UNARY_RHS
2122 && TREE_CODE (gimple_assign_rhs1 (stmt
)) == SSA_NAME
)
2124 return fold_build1 (gimple_assign_rhs_code (stmt
),
2125 gimple_expr_type (stmt
),
2126 get_val_for (gimple_assign_rhs1 (stmt
), base
));
2128 else if (gimple_assign_rhs_class (stmt
) == GIMPLE_BINARY_RHS
)
2130 tree rhs1
= gimple_assign_rhs1 (stmt
);
2131 tree rhs2
= gimple_assign_rhs2 (stmt
);
2132 if (TREE_CODE (rhs1
) == SSA_NAME
)
2133 rhs1
= get_val_for (rhs1
, base
);
2134 else if (TREE_CODE (rhs2
) == SSA_NAME
)
2135 rhs2
= get_val_for (rhs2
, base
);
2138 return fold_build2 (gimple_assign_rhs_code (stmt
),
2139 gimple_expr_type (stmt
), rhs1
, rhs2
);
2146 /* Tries to count the number of iterations of LOOP till it exits by EXIT
2147 by brute force -- i.e. by determining the value of the operands of the
2148 condition at EXIT in first few iterations of the loop (assuming that
2149 these values are constant) and determining the first one in that the
2150 condition is not satisfied. Returns the constant giving the number
2151 of the iterations of LOOP if successful, chrec_dont_know otherwise. */
2154 loop_niter_by_eval (struct loop
*loop
, edge exit
)
2157 tree op
[2], val
[2], next
[2], aval
[2];
2162 cond
= last_stmt (exit
->src
);
2163 if (!cond
|| gimple_code (cond
) != GIMPLE_COND
)
2164 return chrec_dont_know
;
2166 cmp
= gimple_cond_code (cond
);
2167 if (exit
->flags
& EDGE_TRUE_VALUE
)
2168 cmp
= invert_tree_comparison (cmp
, false);
2178 op
[0] = gimple_cond_lhs (cond
);
2179 op
[1] = gimple_cond_rhs (cond
);
2183 return chrec_dont_know
;
2186 for (j
= 0; j
< 2; j
++)
2188 if (is_gimple_min_invariant (op
[j
]))
2191 next
[j
] = NULL_TREE
;
2196 phi
= get_base_for (loop
, op
[j
]);
2198 return chrec_dont_know
;
2199 val
[j
] = PHI_ARG_DEF_FROM_EDGE (phi
, loop_preheader_edge (loop
));
2200 next
[j
] = PHI_ARG_DEF_FROM_EDGE (phi
, loop_latch_edge (loop
));
2204 /* Don't issue signed overflow warnings. */
2205 fold_defer_overflow_warnings ();
2207 for (i
= 0; i
< MAX_ITERATIONS_TO_TRACK
; i
++)
2209 for (j
= 0; j
< 2; j
++)
2210 aval
[j
] = get_val_for (op
[j
], val
[j
]);
2212 acnd
= fold_binary (cmp
, boolean_type_node
, aval
[0], aval
[1]);
2213 if (acnd
&& integer_zerop (acnd
))
2215 fold_undefer_and_ignore_overflow_warnings ();
2216 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2218 "Proved that loop %d iterates %d times using brute force.\n",
2220 return build_int_cst (unsigned_type_node
, i
);
2223 for (j
= 0; j
< 2; j
++)
2225 val
[j
] = get_val_for (next
[j
], val
[j
]);
2226 if (!is_gimple_min_invariant (val
[j
]))
2228 fold_undefer_and_ignore_overflow_warnings ();
2229 return chrec_dont_know
;
2234 fold_undefer_and_ignore_overflow_warnings ();
2236 return chrec_dont_know
;
2239 /* Finds the exit of the LOOP by that the loop exits after a constant
2240 number of iterations and stores the exit edge to *EXIT. The constant
2241 giving the number of iterations of LOOP is returned. The number of
2242 iterations is determined using loop_niter_by_eval (i.e. by brute force
2243 evaluation). If we are unable to find the exit for that loop_niter_by_eval
2244 determines the number of iterations, chrec_dont_know is returned. */
2247 find_loop_niter_by_eval (struct loop
*loop
, edge
*exit
)
2250 VEC (edge
, heap
) *exits
= get_loop_exit_edges (loop
);
2252 tree niter
= NULL_TREE
, aniter
;
2256 /* Loops with multiple exits are expensive to handle and less important. */
2257 if (!flag_expensive_optimizations
2258 && VEC_length (edge
, exits
) > 1)
2259 return chrec_dont_know
;
2261 for (i
= 0; VEC_iterate (edge
, exits
, i
, ex
); i
++)
2263 if (!just_once_each_iteration_p (loop
, ex
->src
))
2266 aniter
= loop_niter_by_eval (loop
, ex
);
2267 if (chrec_contains_undetermined (aniter
))
2271 && !tree_int_cst_lt (aniter
, niter
))
2277 VEC_free (edge
, heap
, exits
);
2279 return niter
? niter
: chrec_dont_know
;
2284 Analysis of upper bounds on number of iterations of a loop.
2288 static double_int
derive_constant_upper_bound_ops (tree
, tree
,
2289 enum tree_code
, tree
);
2291 /* Returns a constant upper bound on the value of the right-hand side of
2292 an assignment statement STMT. */
2295 derive_constant_upper_bound_assign (gimple stmt
)
2297 enum tree_code code
= gimple_assign_rhs_code (stmt
);
2298 tree op0
= gimple_assign_rhs1 (stmt
);
2299 tree op1
= gimple_assign_rhs2 (stmt
);
2301 return derive_constant_upper_bound_ops (TREE_TYPE (gimple_assign_lhs (stmt
)),
2305 /* Returns a constant upper bound on the value of expression VAL. VAL
2306 is considered to be unsigned. If its type is signed, its value must
2310 derive_constant_upper_bound (tree val
)
2312 enum tree_code code
;
2315 extract_ops_from_tree (val
, &code
, &op0
, &op1
);
2316 return derive_constant_upper_bound_ops (TREE_TYPE (val
), op0
, code
, op1
);
2319 /* Returns a constant upper bound on the value of expression OP0 CODE OP1,
2320 whose type is TYPE. The expression is considered to be unsigned. If
2321 its type is signed, its value must be nonnegative. */
2324 derive_constant_upper_bound_ops (tree type
, tree op0
,
2325 enum tree_code code
, tree op1
)
2328 double_int bnd
, max
, mmax
, cst
;
2331 if (INTEGRAL_TYPE_P (type
))
2332 maxt
= TYPE_MAX_VALUE (type
);
2334 maxt
= upper_bound_in_type (type
, type
);
2336 max
= tree_to_double_int (maxt
);
2341 return tree_to_double_int (op0
);
2344 subtype
= TREE_TYPE (op0
);
2345 if (!TYPE_UNSIGNED (subtype
)
2346 /* If TYPE is also signed, the fact that VAL is nonnegative implies
2347 that OP0 is nonnegative. */
2348 && TYPE_UNSIGNED (type
)
2349 && !tree_expr_nonnegative_p (op0
))
2351 /* If we cannot prove that the casted expression is nonnegative,
2352 we cannot establish more useful upper bound than the precision
2353 of the type gives us. */
2357 /* We now know that op0 is an nonnegative value. Try deriving an upper
2359 bnd
= derive_constant_upper_bound (op0
);
2361 /* If the bound does not fit in TYPE, max. value of TYPE could be
2363 if (double_int_ucmp (max
, bnd
) < 0)
2369 case POINTER_PLUS_EXPR
:
2371 if (TREE_CODE (op1
) != INTEGER_CST
2372 || !tree_expr_nonnegative_p (op0
))
2375 /* Canonicalize to OP0 - CST. Consider CST to be signed, in order to
2376 choose the most logical way how to treat this constant regardless
2377 of the signedness of the type. */
2378 cst
= tree_to_double_int (op1
);
2379 cst
= double_int_sext (cst
, TYPE_PRECISION (type
));
2380 if (code
!= MINUS_EXPR
)
2381 cst
= double_int_neg (cst
);
2383 bnd
= derive_constant_upper_bound (op0
);
2385 if (double_int_negative_p (cst
))
2387 cst
= double_int_neg (cst
);
2388 /* Avoid CST == 0x80000... */
2389 if (double_int_negative_p (cst
))
2392 /* OP0 + CST. We need to check that
2393 BND <= MAX (type) - CST. */
2395 mmax
= double_int_add (max
, double_int_neg (cst
));
2396 if (double_int_ucmp (bnd
, mmax
) > 0)
2399 return double_int_add (bnd
, cst
);
2403 /* OP0 - CST, where CST >= 0.
2405 If TYPE is signed, we have already verified that OP0 >= 0, and we
2406 know that the result is nonnegative. This implies that
2409 If TYPE is unsigned, we must additionally know that OP0 >= CST,
2410 otherwise the operation underflows.
2413 /* This should only happen if the type is unsigned; however, for
2414 buggy programs that use overflowing signed arithmetics even with
2415 -fno-wrapv, this condition may also be true for signed values. */
2416 if (double_int_ucmp (bnd
, cst
) < 0)
2419 if (TYPE_UNSIGNED (type
))
2421 tree tem
= fold_binary (GE_EXPR
, boolean_type_node
, op0
,
2422 double_int_to_tree (type
, cst
));
2423 if (!tem
|| integer_nonzerop (tem
))
2427 bnd
= double_int_add (bnd
, double_int_neg (cst
));
2432 case FLOOR_DIV_EXPR
:
2433 case EXACT_DIV_EXPR
:
2434 if (TREE_CODE (op1
) != INTEGER_CST
2435 || tree_int_cst_sign_bit (op1
))
2438 bnd
= derive_constant_upper_bound (op0
);
2439 return double_int_udiv (bnd
, tree_to_double_int (op1
), FLOOR_DIV_EXPR
);
2442 if (TREE_CODE (op1
) != INTEGER_CST
2443 || tree_int_cst_sign_bit (op1
))
2445 return tree_to_double_int (op1
);
2448 stmt
= SSA_NAME_DEF_STMT (op0
);
2449 if (gimple_code (stmt
) != GIMPLE_ASSIGN
2450 || gimple_assign_lhs (stmt
) != op0
)
2452 return derive_constant_upper_bound_assign (stmt
);
2459 /* Records that every statement in LOOP is executed I_BOUND times.
2460 REALISTIC is true if I_BOUND is expected to be close to the real number
2461 of iterations. UPPER is true if we are sure the loop iterates at most
2465 record_niter_bound (struct loop
*loop
, double_int i_bound
, bool realistic
,
2468 /* Update the bounds only when there is no previous estimation, or when the current
2469 estimation is smaller. */
2471 && (!loop
->any_upper_bound
2472 || double_int_ucmp (i_bound
, loop
->nb_iterations_upper_bound
) < 0))
2474 loop
->any_upper_bound
= true;
2475 loop
->nb_iterations_upper_bound
= i_bound
;
2478 && (!loop
->any_estimate
2479 || double_int_ucmp (i_bound
, loop
->nb_iterations_estimate
) < 0))
2481 loop
->any_estimate
= true;
2482 loop
->nb_iterations_estimate
= i_bound
;
2486 /* Records that AT_STMT is executed at most BOUND + 1 times in LOOP. IS_EXIT
2487 is true if the loop is exited immediately after STMT, and this exit
2488 is taken at last when the STMT is executed BOUND + 1 times.
2489 REALISTIC is true if BOUND is expected to be close to the real number
2490 of iterations. UPPER is true if we are sure the loop iterates at most
2491 BOUND times. I_BOUND is an unsigned double_int upper estimate on BOUND. */
2494 record_estimate (struct loop
*loop
, tree bound
, double_int i_bound
,
2495 gimple at_stmt
, bool is_exit
, bool realistic
, bool upper
)
2500 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2502 fprintf (dump_file
, "Statement %s", is_exit
? "(exit)" : "");
2503 print_gimple_stmt (dump_file
, at_stmt
, 0, TDF_SLIM
);
2504 fprintf (dump_file
, " is %sexecuted at most ",
2505 upper
? "" : "probably ");
2506 print_generic_expr (dump_file
, bound
, TDF_SLIM
);
2507 fprintf (dump_file
, " (bounded by ");
2508 dump_double_int (dump_file
, i_bound
, true);
2509 fprintf (dump_file
, ") + 1 times in loop %d.\n", loop
->num
);
2512 /* If the I_BOUND is just an estimate of BOUND, it rarely is close to the
2513 real number of iterations. */
2514 if (TREE_CODE (bound
) != INTEGER_CST
)
2516 if (!upper
&& !realistic
)
2519 /* If we have a guaranteed upper bound, record it in the appropriate
2523 struct nb_iter_bound
*elt
= GGC_NEW (struct nb_iter_bound
);
2525 elt
->bound
= i_bound
;
2526 elt
->stmt
= at_stmt
;
2527 elt
->is_exit
= is_exit
;
2528 elt
->next
= loop
->bounds
;
2532 /* Update the number of iteration estimates according to the bound.
2533 If at_stmt is an exit, then every statement in the loop is
2534 executed at most BOUND + 1 times. If it is not an exit, then
2535 some of the statements before it could be executed BOUND + 2
2536 times, if an exit of LOOP is before stmt. */
2537 exit
= single_exit (loop
);
2540 && dominated_by_p (CDI_DOMINATORS
,
2541 exit
->src
, gimple_bb (at_stmt
))))
2542 delta
= double_int_one
;
2544 delta
= double_int_two
;
2545 i_bound
= double_int_add (i_bound
, delta
);
2547 /* If an overflow occurred, ignore the result. */
2548 if (double_int_ucmp (i_bound
, delta
) < 0)
2551 record_niter_bound (loop
, i_bound
, realistic
, upper
);
2554 /* Record the estimate on number of iterations of LOOP based on the fact that
2555 the induction variable BASE + STEP * i evaluated in STMT does not wrap and
2556 its values belong to the range <LOW, HIGH>. REALISTIC is true if the
2557 estimated number of iterations is expected to be close to the real one.
2558 UPPER is true if we are sure the induction variable does not wrap. */
2561 record_nonwrapping_iv (struct loop
*loop
, tree base
, tree step
, gimple stmt
,
2562 tree low
, tree high
, bool realistic
, bool upper
)
2564 tree niter_bound
, extreme
, delta
;
2565 tree type
= TREE_TYPE (base
), unsigned_type
;
2568 if (TREE_CODE (step
) != INTEGER_CST
|| integer_zerop (step
))
2571 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2573 fprintf (dump_file
, "Induction variable (");
2574 print_generic_expr (dump_file
, TREE_TYPE (base
), TDF_SLIM
);
2575 fprintf (dump_file
, ") ");
2576 print_generic_expr (dump_file
, base
, TDF_SLIM
);
2577 fprintf (dump_file
, " + ");
2578 print_generic_expr (dump_file
, step
, TDF_SLIM
);
2579 fprintf (dump_file
, " * iteration does not wrap in statement ");
2580 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
2581 fprintf (dump_file
, " in loop %d.\n", loop
->num
);
2584 unsigned_type
= unsigned_type_for (type
);
2585 base
= fold_convert (unsigned_type
, base
);
2586 step
= fold_convert (unsigned_type
, step
);
2588 if (tree_int_cst_sign_bit (step
))
2590 extreme
= fold_convert (unsigned_type
, low
);
2591 if (TREE_CODE (base
) != INTEGER_CST
)
2592 base
= fold_convert (unsigned_type
, high
);
2593 delta
= fold_build2 (MINUS_EXPR
, unsigned_type
, base
, extreme
);
2594 step
= fold_build1 (NEGATE_EXPR
, unsigned_type
, step
);
2598 extreme
= fold_convert (unsigned_type
, high
);
2599 if (TREE_CODE (base
) != INTEGER_CST
)
2600 base
= fold_convert (unsigned_type
, low
);
2601 delta
= fold_build2 (MINUS_EXPR
, unsigned_type
, extreme
, base
);
2604 /* STMT is executed at most NITER_BOUND + 1 times, since otherwise the value
2605 would get out of the range. */
2606 niter_bound
= fold_build2 (FLOOR_DIV_EXPR
, unsigned_type
, delta
, step
);
2607 max
= derive_constant_upper_bound (niter_bound
);
2608 record_estimate (loop
, niter_bound
, max
, stmt
, false, realistic
, upper
);
2611 /* Returns true if REF is a reference to an array at the end of a dynamically
2612 allocated structure. If this is the case, the array may be allocated larger
2613 than its upper bound implies. */
2616 array_at_struct_end_p (tree ref
)
2618 tree base
= get_base_address (ref
);
2621 /* Unless the reference is through a pointer, the size of the array matches
2623 if (!base
|| !INDIRECT_REF_P (base
))
2626 for (;handled_component_p (ref
); ref
= parent
)
2628 parent
= TREE_OPERAND (ref
, 0);
2630 if (TREE_CODE (ref
) == COMPONENT_REF
)
2632 /* All fields of a union are at its end. */
2633 if (TREE_CODE (TREE_TYPE (parent
)) == UNION_TYPE
)
2636 /* Unless the field is at the end of the struct, we are done. */
2637 field
= TREE_OPERAND (ref
, 1);
2638 if (TREE_CHAIN (field
))
2642 /* The other options are ARRAY_REF, ARRAY_RANGE_REF, VIEW_CONVERT_EXPR.
2643 In all these cases, we might be accessing the last element, and
2644 although in practice this will probably never happen, it is legal for
2645 the indices of this last element to exceed the bounds of the array.
2646 Therefore, continue checking. */
2649 gcc_assert (INDIRECT_REF_P (ref
));
2653 /* Determine information about number of iterations a LOOP from the index
2654 IDX of a data reference accessed in STMT. RELIABLE is true if STMT is
2655 guaranteed to be executed in every iteration of LOOP. Callback for
2666 idx_infer_loop_bounds (tree base
, tree
*idx
, void *dta
)
2668 struct ilb_data
*data
= (struct ilb_data
*) dta
;
2669 tree ev
, init
, step
;
2670 tree low
, high
, type
, next
;
2671 bool sign
, upper
= data
->reliable
, at_end
= false;
2672 struct loop
*loop
= data
->loop
;
2674 if (TREE_CODE (base
) != ARRAY_REF
)
2677 /* For arrays at the end of the structure, we are not guaranteed that they
2678 do not really extend over their declared size. However, for arrays of
2679 size greater than one, this is unlikely to be intended. */
2680 if (array_at_struct_end_p (base
))
2686 ev
= instantiate_parameters (loop
, analyze_scalar_evolution (loop
, *idx
));
2687 init
= initial_condition (ev
);
2688 step
= evolution_part_in_loop_num (ev
, loop
->num
);
2692 || TREE_CODE (step
) != INTEGER_CST
2693 || integer_zerop (step
)
2694 || tree_contains_chrecs (init
, NULL
)
2695 || chrec_contains_symbols_defined_in_loop (init
, loop
->num
))
2698 low
= array_ref_low_bound (base
);
2699 high
= array_ref_up_bound (base
);
2701 /* The case of nonconstant bounds could be handled, but it would be
2703 if (TREE_CODE (low
) != INTEGER_CST
2705 || TREE_CODE (high
) != INTEGER_CST
)
2707 sign
= tree_int_cst_sign_bit (step
);
2708 type
= TREE_TYPE (step
);
2710 /* The array of length 1 at the end of a structure most likely extends
2711 beyond its bounds. */
2713 && operand_equal_p (low
, high
, 0))
2716 /* In case the relevant bound of the array does not fit in type, or
2717 it does, but bound + step (in type) still belongs into the range of the
2718 array, the index may wrap and still stay within the range of the array
2719 (consider e.g. if the array is indexed by the full range of
2722 To make things simpler, we require both bounds to fit into type, although
2723 there are cases where this would not be strictly necessary. */
2724 if (!int_fits_type_p (high
, type
)
2725 || !int_fits_type_p (low
, type
))
2727 low
= fold_convert (type
, low
);
2728 high
= fold_convert (type
, high
);
2731 next
= fold_binary (PLUS_EXPR
, type
, low
, step
);
2733 next
= fold_binary (PLUS_EXPR
, type
, high
, step
);
2735 if (tree_int_cst_compare (low
, next
) <= 0
2736 && tree_int_cst_compare (next
, high
) <= 0)
2739 record_nonwrapping_iv (loop
, init
, step
, data
->stmt
, low
, high
, true, upper
);
2743 /* Determine information about number of iterations a LOOP from the bounds
2744 of arrays in the data reference REF accessed in STMT. RELIABLE is true if
2745 STMT is guaranteed to be executed in every iteration of LOOP.*/
2748 infer_loop_bounds_from_ref (struct loop
*loop
, gimple stmt
, tree ref
,
2751 struct ilb_data data
;
2755 data
.reliable
= reliable
;
2756 for_each_index (&ref
, idx_infer_loop_bounds
, &data
);
2759 /* Determine information about number of iterations of a LOOP from the way
2760 arrays are used in STMT. RELIABLE is true if STMT is guaranteed to be
2761 executed in every iteration of LOOP. */
2764 infer_loop_bounds_from_array (struct loop
*loop
, gimple stmt
, bool reliable
)
2766 if (is_gimple_assign (stmt
))
2768 tree op0
= gimple_assign_lhs (stmt
);
2769 tree op1
= gimple_assign_rhs1 (stmt
);
2771 /* For each memory access, analyze its access function
2772 and record a bound on the loop iteration domain. */
2773 if (REFERENCE_CLASS_P (op0
))
2774 infer_loop_bounds_from_ref (loop
, stmt
, op0
, reliable
);
2776 if (REFERENCE_CLASS_P (op1
))
2777 infer_loop_bounds_from_ref (loop
, stmt
, op1
, reliable
);
2779 else if (is_gimple_call (stmt
))
2782 unsigned i
, n
= gimple_call_num_args (stmt
);
2784 lhs
= gimple_call_lhs (stmt
);
2785 if (lhs
&& REFERENCE_CLASS_P (lhs
))
2786 infer_loop_bounds_from_ref (loop
, stmt
, lhs
, reliable
);
2788 for (i
= 0; i
< n
; i
++)
2790 arg
= gimple_call_arg (stmt
, i
);
2791 if (REFERENCE_CLASS_P (arg
))
2792 infer_loop_bounds_from_ref (loop
, stmt
, arg
, reliable
);
2797 /* Determine information about number of iterations of a LOOP from the fact
2798 that signed arithmetics in STMT does not overflow. */
2801 infer_loop_bounds_from_signedness (struct loop
*loop
, gimple stmt
)
2803 tree def
, base
, step
, scev
, type
, low
, high
;
2805 if (gimple_code (stmt
) != GIMPLE_ASSIGN
)
2808 def
= gimple_assign_lhs (stmt
);
2810 if (TREE_CODE (def
) != SSA_NAME
)
2813 type
= TREE_TYPE (def
);
2814 if (!INTEGRAL_TYPE_P (type
)
2815 || !TYPE_OVERFLOW_UNDEFINED (type
))
2818 scev
= instantiate_parameters (loop
, analyze_scalar_evolution (loop
, def
));
2819 if (chrec_contains_undetermined (scev
))
2822 base
= initial_condition_in_loop_num (scev
, loop
->num
);
2823 step
= evolution_part_in_loop_num (scev
, loop
->num
);
2826 || TREE_CODE (step
) != INTEGER_CST
2827 || tree_contains_chrecs (base
, NULL
)
2828 || chrec_contains_symbols_defined_in_loop (base
, loop
->num
))
2831 low
= lower_bound_in_type (type
, type
);
2832 high
= upper_bound_in_type (type
, type
);
2834 record_nonwrapping_iv (loop
, base
, step
, stmt
, low
, high
, false, true);
2837 /* The following analyzers are extracting informations on the bounds
2838 of LOOP from the following undefined behaviors:
2840 - data references should not access elements over the statically
2843 - signed variables should not overflow when flag_wrapv is not set.
2847 infer_loop_bounds_from_undefined (struct loop
*loop
)
2851 gimple_stmt_iterator bsi
;
2855 bbs
= get_loop_body (loop
);
2857 for (i
= 0; i
< loop
->num_nodes
; i
++)
2861 /* If BB is not executed in each iteration of the loop, we cannot
2862 use the operations in it to infer reliable upper bound on the
2863 # of iterations of the loop. However, we can use it as a guess. */
2864 reliable
= dominated_by_p (CDI_DOMINATORS
, loop
->latch
, bb
);
2866 for (bsi
= gsi_start_bb (bb
); !gsi_end_p (bsi
); gsi_next (&bsi
))
2868 gimple stmt
= gsi_stmt (bsi
);
2870 infer_loop_bounds_from_array (loop
, stmt
, reliable
);
2873 infer_loop_bounds_from_signedness (loop
, stmt
);
2881 /* Converts VAL to double_int. */
2884 gcov_type_to_double_int (gcov_type val
)
2888 ret
.low
= (unsigned HOST_WIDE_INT
) val
;
2889 /* If HOST_BITS_PER_WIDE_INT == HOST_BITS_PER_WIDEST_INT, avoid shifting by
2890 the size of type. */
2891 val
>>= HOST_BITS_PER_WIDE_INT
- 1;
2893 ret
.high
= (unsigned HOST_WIDE_INT
) val
;
2898 /* Records estimates on numbers of iterations of LOOP. */
2901 estimate_numbers_of_iterations_loop (struct loop
*loop
)
2903 VEC (edge
, heap
) *exits
;
2906 struct tree_niter_desc niter_desc
;
2910 /* Give up if we already have tried to compute an estimation. */
2911 if (loop
->estimate_state
!= EST_NOT_COMPUTED
)
2913 loop
->estimate_state
= EST_AVAILABLE
;
2914 loop
->any_upper_bound
= false;
2915 loop
->any_estimate
= false;
2917 exits
= get_loop_exit_edges (loop
);
2918 for (i
= 0; VEC_iterate (edge
, exits
, i
, ex
); i
++)
2920 if (!number_of_iterations_exit (loop
, ex
, &niter_desc
, false))
2923 niter
= niter_desc
.niter
;
2924 type
= TREE_TYPE (niter
);
2925 if (TREE_CODE (niter_desc
.may_be_zero
) != INTEGER_CST
)
2926 niter
= build3 (COND_EXPR
, type
, niter_desc
.may_be_zero
,
2927 build_int_cst (type
, 0),
2929 record_estimate (loop
, niter
, niter_desc
.max
,
2930 last_stmt (ex
->src
),
2933 VEC_free (edge
, heap
, exits
);
2935 infer_loop_bounds_from_undefined (loop
);
2937 /* If we have a measured profile, use it to estimate the number of
2939 if (loop
->header
->count
!= 0)
2941 gcov_type nit
= expected_loop_iterations_unbounded (loop
) + 1;
2942 bound
= gcov_type_to_double_int (nit
);
2943 record_niter_bound (loop
, bound
, true, false);
2946 /* If an upper bound is smaller than the realistic estimate of the
2947 number of iterations, use the upper bound instead. */
2948 if (loop
->any_upper_bound
2949 && loop
->any_estimate
2950 && double_int_ucmp (loop
->nb_iterations_upper_bound
,
2951 loop
->nb_iterations_estimate
) < 0)
2952 loop
->nb_iterations_estimate
= loop
->nb_iterations_upper_bound
;
2955 /* Records estimates on numbers of iterations of loops. */
2958 estimate_numbers_of_iterations (void)
2963 /* We don't want to issue signed overflow warnings while getting
2964 loop iteration estimates. */
2965 fold_defer_overflow_warnings ();
2967 FOR_EACH_LOOP (li
, loop
, 0)
2969 estimate_numbers_of_iterations_loop (loop
);
2972 fold_undefer_and_ignore_overflow_warnings ();
2975 /* Returns true if statement S1 dominates statement S2. */
2978 stmt_dominates_stmt_p (gimple s1
, gimple s2
)
2980 basic_block bb1
= gimple_bb (s1
), bb2
= gimple_bb (s2
);
2988 gimple_stmt_iterator bsi
;
2990 if (gimple_code (s2
) == GIMPLE_PHI
)
2993 if (gimple_code (s1
) == GIMPLE_PHI
)
2996 for (bsi
= gsi_start_bb (bb1
); gsi_stmt (bsi
) != s2
; gsi_next (&bsi
))
2997 if (gsi_stmt (bsi
) == s1
)
3003 return dominated_by_p (CDI_DOMINATORS
, bb2
, bb1
);
3006 /* Returns true when we can prove that the number of executions of
3007 STMT in the loop is at most NITER, according to the bound on
3008 the number of executions of the statement NITER_BOUND->stmt recorded in
3009 NITER_BOUND. If STMT is NULL, we must prove this bound for all
3010 statements in the loop. */
3013 n_of_executions_at_most (gimple stmt
,
3014 struct nb_iter_bound
*niter_bound
,
3017 double_int bound
= niter_bound
->bound
;
3018 tree nit_type
= TREE_TYPE (niter
), e
;
3021 gcc_assert (TYPE_UNSIGNED (nit_type
));
3023 /* If the bound does not even fit into NIT_TYPE, it cannot tell us that
3024 the number of iterations is small. */
3025 if (!double_int_fits_to_tree_p (nit_type
, bound
))
3028 /* We know that NITER_BOUND->stmt is executed at most NITER_BOUND->bound + 1
3029 times. This means that:
3031 -- if NITER_BOUND->is_exit is true, then everything before
3032 NITER_BOUND->stmt is executed at most NITER_BOUND->bound + 1
3033 times, and everything after it at most NITER_BOUND->bound times.
3035 -- If NITER_BOUND->is_exit is false, then if we can prove that when STMT
3036 is executed, then NITER_BOUND->stmt is executed as well in the same
3037 iteration (we conclude that if both statements belong to the same
3038 basic block, or if STMT is after NITER_BOUND->stmt), then STMT
3039 is executed at most NITER_BOUND->bound + 1 times. Otherwise STMT is
3040 executed at most NITER_BOUND->bound + 2 times. */
3042 if (niter_bound
->is_exit
)
3045 && stmt
!= niter_bound
->stmt
3046 && stmt_dominates_stmt_p (niter_bound
->stmt
, stmt
))
3054 || (gimple_bb (stmt
) != gimple_bb (niter_bound
->stmt
)
3055 && !stmt_dominates_stmt_p (niter_bound
->stmt
, stmt
)))
3057 bound
= double_int_add (bound
, double_int_one
);
3058 if (double_int_zero_p (bound
)
3059 || !double_int_fits_to_tree_p (nit_type
, bound
))
3065 e
= fold_binary (cmp
, boolean_type_node
,
3066 niter
, double_int_to_tree (nit_type
, bound
));
3067 return e
&& integer_nonzerop (e
);
3070 /* Returns true if the arithmetics in TYPE can be assumed not to wrap. */
3073 nowrap_type_p (tree type
)
3075 if (INTEGRAL_TYPE_P (type
)
3076 && TYPE_OVERFLOW_UNDEFINED (type
))
3079 if (POINTER_TYPE_P (type
))
3085 /* Return false only when the induction variable BASE + STEP * I is
3086 known to not overflow: i.e. when the number of iterations is small
3087 enough with respect to the step and initial condition in order to
3088 keep the evolution confined in TYPEs bounds. Return true when the
3089 iv is known to overflow or when the property is not computable.
3091 USE_OVERFLOW_SEMANTICS is true if this function should assume that
3092 the rules for overflow of the given language apply (e.g., that signed
3093 arithmetics in C does not overflow). */
3096 scev_probably_wraps_p (tree base
, tree step
,
3097 gimple at_stmt
, struct loop
*loop
,
3098 bool use_overflow_semantics
)
3100 struct nb_iter_bound
*bound
;
3101 tree delta
, step_abs
;
3102 tree unsigned_type
, valid_niter
;
3103 tree type
= TREE_TYPE (step
);
3105 /* FIXME: We really need something like
3106 http://gcc.gnu.org/ml/gcc-patches/2005-06/msg02025.html.
3108 We used to test for the following situation that frequently appears
3109 during address arithmetics:
3111 D.1621_13 = (long unsigned intD.4) D.1620_12;
3112 D.1622_14 = D.1621_13 * 8;
3113 D.1623_15 = (doubleD.29 *) D.1622_14;
3115 And derived that the sequence corresponding to D_14
3116 can be proved to not wrap because it is used for computing a
3117 memory access; however, this is not really the case -- for example,
3118 if D_12 = (unsigned char) [254,+,1], then D_14 has values
3119 2032, 2040, 0, 8, ..., but the code is still legal. */
3121 if (chrec_contains_undetermined (base
)
3122 || chrec_contains_undetermined (step
))
3125 if (integer_zerop (step
))
3128 /* If we can use the fact that signed and pointer arithmetics does not
3129 wrap, we are done. */
3130 if (use_overflow_semantics
&& nowrap_type_p (TREE_TYPE (base
)))
3133 /* To be able to use estimates on number of iterations of the loop,
3134 we must have an upper bound on the absolute value of the step. */
3135 if (TREE_CODE (step
) != INTEGER_CST
)
3138 /* Don't issue signed overflow warnings. */
3139 fold_defer_overflow_warnings ();
3141 /* Otherwise, compute the number of iterations before we reach the
3142 bound of the type, and verify that the loop is exited before this
3144 unsigned_type
= unsigned_type_for (type
);
3145 base
= fold_convert (unsigned_type
, base
);
3147 if (tree_int_cst_sign_bit (step
))
3149 tree extreme
= fold_convert (unsigned_type
,
3150 lower_bound_in_type (type
, type
));
3151 delta
= fold_build2 (MINUS_EXPR
, unsigned_type
, base
, extreme
);
3152 step_abs
= fold_build1 (NEGATE_EXPR
, unsigned_type
,
3153 fold_convert (unsigned_type
, step
));
3157 tree extreme
= fold_convert (unsigned_type
,
3158 upper_bound_in_type (type
, type
));
3159 delta
= fold_build2 (MINUS_EXPR
, unsigned_type
, extreme
, base
);
3160 step_abs
= fold_convert (unsigned_type
, step
);
3163 valid_niter
= fold_build2 (FLOOR_DIV_EXPR
, unsigned_type
, delta
, step_abs
);
3165 estimate_numbers_of_iterations_loop (loop
);
3166 for (bound
= loop
->bounds
; bound
; bound
= bound
->next
)
3168 if (n_of_executions_at_most (at_stmt
, bound
, valid_niter
))
3170 fold_undefer_and_ignore_overflow_warnings ();
3175 fold_undefer_and_ignore_overflow_warnings ();
3177 /* At this point we still don't have a proof that the iv does not
3178 overflow: give up. */
3182 /* Frees the information on upper bounds on numbers of iterations of LOOP. */
3185 free_numbers_of_iterations_estimates_loop (struct loop
*loop
)
3187 struct nb_iter_bound
*bound
, *next
;
3189 loop
->nb_iterations
= NULL
;
3190 loop
->estimate_state
= EST_NOT_COMPUTED
;
3191 for (bound
= loop
->bounds
; bound
; bound
= next
)
3197 loop
->bounds
= NULL
;
3200 /* Frees the information on upper bounds on numbers of iterations of loops. */
3203 free_numbers_of_iterations_estimates (void)
3208 FOR_EACH_LOOP (li
, loop
, 0)
3210 free_numbers_of_iterations_estimates_loop (loop
);
3214 /* Substitute value VAL for ssa name NAME inside expressions held
3218 substitute_in_loop_info (struct loop
*loop
, tree name
, tree val
)
3220 loop
->nb_iterations
= simplify_replace_tree (loop
->nb_iterations
, name
, val
);