1 /* Functions to determine/estimate number of iterations of a loop.
2 Copyright (C) 2004 Free Software Foundation, Inc.
4 This file is part of GCC.
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 2, or (at your option) any
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
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING. If not, write to the Free
18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
23 #include "coretypes.h"
28 #include "hard-reg-set.h"
29 #include "basic-block.h"
31 #include "diagnostic.h"
32 #include "tree-flow.h"
33 #include "tree-dump.h"
35 #include "tree-pass.h"
37 #include "tree-chrec.h"
38 #include "tree-scalar-evolution.h"
39 #include "tree-data-ref.h"
42 #include "tree-inline.h"
44 #define SWAP(X, Y) do { void *tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
46 /* Just to shorten the ugly names. */
47 #define EXEC_BINARY nondestructive_fold_binary_to_constant
48 #define EXEC_UNARY nondestructive_fold_unary_to_constant
52 Analysis of number of iterations of an affine exit test.
56 /* Returns true if ARG is either NULL_TREE or constant zero. Unlike
57 integer_zerop, it does not care about overflow flags. */
65 if (TREE_CODE (arg) != INTEGER_CST)
68 return (TREE_INT_CST_LOW (arg) == 0 && TREE_INT_CST_HIGH (arg) == 0);
71 /* Returns true if ARG a nonzero constant. Unlike integer_nonzerop, it does
72 not care about overflow flags. */
80 if (TREE_CODE (arg) != INTEGER_CST)
83 return (TREE_INT_CST_LOW (arg) != 0 || TREE_INT_CST_HIGH (arg) != 0);
86 /* Returns number of zeros at the end of binary representation of X.
88 ??? Use ffs if available? */
91 num_ending_zeros (tree x)
93 unsigned HOST_WIDE_INT fr, nfr;
95 tree type = TREE_TYPE (x);
97 if (TREE_INT_CST_LOW (x) == 0)
99 num = HOST_BITS_PER_WIDE_INT;
100 fr = TREE_INT_CST_HIGH (x);
105 fr = TREE_INT_CST_LOW (x);
108 for (abits = HOST_BITS_PER_WIDE_INT / 2; abits; abits /= 2)
111 if (nfr << abits == fr)
118 if (num > TYPE_PRECISION (type))
119 num = TYPE_PRECISION (type);
121 return build_int_cst_type (type, num);
124 /* Returns inverse of X modulo 2^s, where MASK = 2^s-1. */
127 inverse (tree x, tree mask)
129 tree type = TREE_TYPE (x);
131 unsigned ctr = tree_floor_log2 (mask);
133 if (TYPE_PRECISION (type) <= HOST_BITS_PER_WIDE_INT)
135 unsigned HOST_WIDE_INT ix;
136 unsigned HOST_WIDE_INT imask;
137 unsigned HOST_WIDE_INT irslt = 1;
139 gcc_assert (cst_and_fits_in_hwi (x));
140 gcc_assert (cst_and_fits_in_hwi (mask));
142 ix = int_cst_value (x);
143 imask = int_cst_value (mask);
152 rslt = build_int_cst_type (type, irslt);
156 rslt = build_int_cst_type (type, 1);
159 rslt = EXEC_BINARY (MULT_EXPR, type, rslt, x);
160 x = EXEC_BINARY (MULT_EXPR, type, x, x);
162 rslt = EXEC_BINARY (BIT_AND_EXPR, type, rslt, mask);
168 /* Determine the number of iterations according to condition (for staying
169 inside loop) which compares two induction variables using comparison
170 operator CODE. The induction variable on left side of the comparison
171 has base BASE0 and step STEP0. the right-hand side one has base
172 BASE1 and step STEP1. Both induction variables must have type TYPE,
173 which must be an integer or pointer type. STEP0 and STEP1 must be
174 constants (or NULL_TREE, which is interpreted as constant zero).
176 The results (number of iterations and assumptions as described in
177 comments at struct tree_niter_desc in tree-flow.h) are stored to NITER.
178 In case we are unable to determine number of iterations, contents of
179 this structure is unchanged. */
182 number_of_iterations_cond (tree type, tree base0, tree step0,
183 enum tree_code code, tree base1, tree step1,
184 struct tree_niter_desc *niter)
186 tree step, delta, mmin, mmax;
187 tree may_xform, bound, s, d, tmp;
188 bool was_sharp = false;
190 tree assumptions = boolean_true_node;
191 tree noloop_assumptions = boolean_false_node;
192 tree niter_type, signed_niter_type;
195 /* The meaning of these assumptions is this:
197 then the rest of information does not have to be valid
198 if noloop_assumptions then the loop does not have to roll
199 (but it is only conservative approximation, i.e. it only says that
200 if !noloop_assumptions, then the loop does not end before the computed
201 number of iterations) */
203 /* Make < comparison from > ones. */
209 code = swap_tree_comparison (code);
212 /* We can handle the case when neither of the sides of the comparison is
213 invariant, provided that the test is NE_EXPR. This rarely occurs in
214 practice, but it is simple enough to manage. */
215 if (!zero_p (step0) && !zero_p (step1))
220 step0 = EXEC_BINARY (MINUS_EXPR, type, step0, step1);
224 /* If the result is a constant, the loop is weird. More precise handling
225 would be possible, but the situation is not common enough to waste time
227 if (zero_p (step0) && zero_p (step1))
230 /* Ignore loops of while (i-- < 10) type. */
233 if (step0 && !tree_expr_nonnegative_p (step0))
236 if (!zero_p (step1) && tree_expr_nonnegative_p (step1))
240 if (POINTER_TYPE_P (type))
242 /* We assume pointer arithmetic never overflows. */
243 mmin = mmax = NULL_TREE;
247 mmin = TYPE_MIN_VALUE (type);
248 mmax = TYPE_MAX_VALUE (type);
251 /* Some more condition normalization. We must record some assumptions
256 /* We want to take care only of <=; this is easy,
257 as in cases the overflow would make the transformation unsafe the loop
258 does not roll. Seemingly it would make more sense to want to take
259 care of <, as NE is more similar to it, but the problem is that here
260 the transformation would be more difficult due to possibly infinite
265 assumption = fold (build2 (EQ_EXPR, boolean_type_node, base0, mmax));
267 assumption = boolean_false_node;
268 if (nonzero_p (assumption))
270 base0 = fold (build2 (PLUS_EXPR, type, base0,
271 build_int_cst_type (type, 1)));
276 assumption = fold (build2 (EQ_EXPR, boolean_type_node, base1, mmin));
278 assumption = boolean_false_node;
279 if (nonzero_p (assumption))
281 base1 = fold (build2 (MINUS_EXPR, type, base1,
282 build_int_cst_type (type, 1)));
284 noloop_assumptions = assumption;
287 /* It will be useful to be able to tell the difference once more in
288 <= -> != reduction. */
292 /* Take care of trivially infinite loops. */
297 && operand_equal_p (base0, mmin, 0))
301 && operand_equal_p (base1, mmax, 0))
305 /* If we can we want to take care of NE conditions instead of size
306 comparisons, as they are much more friendly (most importantly
307 this takes care of special handling of loops with step 1). We can
308 do it if we first check that upper bound is greater or equal to
309 lower bound, their difference is constant c modulo step and that
310 there is not an overflow. */
314 step = EXEC_UNARY (NEGATE_EXPR, type, step1);
317 delta = build2 (MINUS_EXPR, type, base1, base0);
318 delta = fold (build2 (FLOOR_MOD_EXPR, type, delta, step));
319 may_xform = boolean_false_node;
321 if (TREE_CODE (delta) == INTEGER_CST)
323 tmp = EXEC_BINARY (MINUS_EXPR, type, step,
324 build_int_cst_type (type, 1));
326 && operand_equal_p (delta, tmp, 0))
328 /* A special case. We have transformed condition of type
329 for (i = 0; i < 4; i += 4)
331 for (i = 0; i <= 3; i += 4)
332 obviously if the test for overflow during that transformation
333 passed, we cannot overflow here. Most importantly any
334 loop with sharp end condition and step 1 falls into this
335 category, so handling this case specially is definitely
336 worth the troubles. */
337 may_xform = boolean_true_node;
339 else if (zero_p (step0))
342 may_xform = boolean_true_node;
345 bound = EXEC_BINARY (PLUS_EXPR, type, mmin, step);
346 bound = EXEC_BINARY (MINUS_EXPR, type, bound, delta);
347 may_xform = fold (build2 (LE_EXPR, boolean_type_node,
354 may_xform = boolean_true_node;
357 bound = EXEC_BINARY (MINUS_EXPR, type, mmax, step);
358 bound = EXEC_BINARY (PLUS_EXPR, type, bound, delta);
359 may_xform = fold (build2 (LE_EXPR, boolean_type_node,
365 if (!zero_p (may_xform))
367 /* We perform the transformation always provided that it is not
368 completely senseless. This is OK, as we would need this assumption
369 to determine the number of iterations anyway. */
370 if (!nonzero_p (may_xform))
371 assumptions = may_xform;
375 base0 = build2 (PLUS_EXPR, type, base0, delta);
376 base0 = fold (build2 (MINUS_EXPR, type, base0, step));
380 base1 = build2 (MINUS_EXPR, type, base1, delta);
381 base1 = fold (build2 (PLUS_EXPR, type, base1, step));
384 assumption = fold (build2 (GT_EXPR, boolean_type_node, base0, base1));
385 noloop_assumptions = fold (build2 (TRUTH_OR_EXPR, boolean_type_node,
386 noloop_assumptions, assumption));
391 /* Count the number of iterations. */
392 niter_type = unsigned_type_for (type);
393 signed_niter_type = signed_type_for (type);
397 /* Everything we do here is just arithmetics modulo size of mode. This
398 makes us able to do more involved computations of number of iterations
399 than in other cases. First transform the condition into shape
400 s * i <> c, with s positive. */
401 base1 = fold (build2 (MINUS_EXPR, type, base1, base0));
404 step0 = EXEC_UNARY (NEGATE_EXPR, type, step1);
406 if (!tree_expr_nonnegative_p (fold_convert (signed_niter_type, step0)))
408 step0 = EXEC_UNARY (NEGATE_EXPR, type, step0);
409 base1 = fold (build1 (NEGATE_EXPR, type, base1));
412 base1 = fold_convert (niter_type, base1);
413 step0 = fold_convert (niter_type, step0);
415 /* Let nsd (step, size of mode) = d. If d does not divide c, the loop
416 is infinite. Otherwise, the number of iterations is
417 (inverse(s/d) * (c/d)) mod (size of mode/d). */
418 bits = num_ending_zeros (step0);
419 d = EXEC_BINARY (LSHIFT_EXPR, niter_type,
420 build_int_cst_type (niter_type, 1), bits);
421 s = EXEC_BINARY (RSHIFT_EXPR, niter_type, step0, bits);
423 bound = build_low_bits_mask (niter_type,
424 (TYPE_PRECISION (niter_type)
425 - tree_low_cst (bits, 1)));
427 assumption = fold (build2 (FLOOR_MOD_EXPR, niter_type, base1, d));
428 assumption = fold (build2 (EQ_EXPR, boolean_type_node,
430 build_int_cst (niter_type, 0)));
431 assumptions = fold (build2 (TRUTH_AND_EXPR, boolean_type_node,
432 assumptions, assumption));
434 tmp = fold (build2 (EXACT_DIV_EXPR, niter_type, base1, d));
435 tmp = fold (build2 (MULT_EXPR, niter_type, tmp, inverse (s, bound)));
436 niter->niter = fold (build2 (BIT_AND_EXPR, niter_type, tmp, bound));
441 /* Condition in shape a + s * i <= b
442 We must know that b + s does not overflow and a <= b + s and then we
443 can compute number of iterations as (b + s - a) / s. (It might
444 seem that we in fact could be more clever about testing the b + s
445 overflow condition using some information about b - a mod s,
446 but it was already taken into account during LE -> NE transform). */
450 bound = EXEC_BINARY (MINUS_EXPR, type, mmax, step0);
451 assumption = fold (build2 (LE_EXPR, boolean_type_node,
453 assumptions = fold (build2 (TRUTH_AND_EXPR, boolean_type_node,
454 assumptions, assumption));
458 tmp = fold (build2 (PLUS_EXPR, type, base1, step0));
459 assumption = fold (build2 (GT_EXPR, boolean_type_node, base0, tmp));
460 delta = fold (build2 (PLUS_EXPR, type, base1, step));
461 delta = fold (build2 (MINUS_EXPR, type, delta, base0));
462 delta = fold_convert (niter_type, delta);
466 /* Condition in shape a <= b - s * i
467 We must know that a - s does not overflow and a - s <= b and then
468 we can again compute number of iterations as (b - (a - s)) / s. */
471 bound = EXEC_BINARY (MINUS_EXPR, type, mmin, step1);
472 assumption = fold (build2 (LE_EXPR, boolean_type_node,
474 assumptions = fold (build2 (TRUTH_AND_EXPR, boolean_type_node,
475 assumptions, assumption));
477 step = fold (build1 (NEGATE_EXPR, type, step1));
478 tmp = fold (build2 (PLUS_EXPR, type, base0, step1));
479 assumption = fold (build2 (GT_EXPR, boolean_type_node, tmp, base1));
480 delta = fold (build2 (MINUS_EXPR, type, base0, step));
481 delta = fold (build2 (MINUS_EXPR, type, base1, delta));
482 delta = fold_convert (niter_type, delta);
484 noloop_assumptions = fold (build2 (TRUTH_OR_EXPR, boolean_type_node,
485 noloop_assumptions, assumption));
486 delta = fold (build2 (FLOOR_DIV_EXPR, niter_type, delta,
487 fold_convert (niter_type, step)));
488 niter->niter = delta;
491 niter->assumptions = assumptions;
492 niter->may_be_zero = noloop_assumptions;
496 niter->assumptions = boolean_true_node;
497 niter->may_be_zero = boolean_true_node;
498 niter->niter = build_int_cst_type (type, 0);
502 /* Tries to simplify EXPR using the evolutions of the loop invariants
503 in the superloops of LOOP. Returns the simplified expression
504 (or EXPR unchanged, if no simplification was possible). */
507 simplify_using_outer_evolutions (struct loop *loop, tree expr)
509 enum tree_code code = TREE_CODE (expr);
513 if (is_gimple_min_invariant (expr))
516 if (code == TRUTH_OR_EXPR
517 || code == TRUTH_AND_EXPR
518 || code == COND_EXPR)
522 e0 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 0));
523 if (TREE_OPERAND (expr, 0) != e0)
526 e1 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 1));
527 if (TREE_OPERAND (expr, 1) != e1)
530 if (code == COND_EXPR)
532 e2 = simplify_using_outer_evolutions (loop, TREE_OPERAND (expr, 2));
533 if (TREE_OPERAND (expr, 2) != e2)
541 if (code == COND_EXPR)
542 expr = build3 (code, boolean_type_node, e0, e1, e2);
544 expr = build2 (code, boolean_type_node, e0, e1);
551 e = instantiate_parameters (loop, expr);
552 if (is_gimple_min_invariant (e))
558 /* Tries to simplify EXPR using the condition COND. Returns the simplified
559 expression (or EXPR unchanged, if no simplification was possible).*/
562 tree_simplify_using_condition (tree cond, tree expr)
565 tree e, e0, e1, e2, notcond;
566 enum tree_code code = TREE_CODE (expr);
568 if (code == INTEGER_CST)
571 if (code == TRUTH_OR_EXPR
572 || code == TRUTH_AND_EXPR
573 || code == COND_EXPR)
577 e0 = tree_simplify_using_condition (cond, TREE_OPERAND (expr, 0));
578 if (TREE_OPERAND (expr, 0) != e0)
581 e1 = tree_simplify_using_condition (cond, TREE_OPERAND (expr, 1));
582 if (TREE_OPERAND (expr, 1) != e1)
585 if (code == COND_EXPR)
587 e2 = tree_simplify_using_condition (cond, TREE_OPERAND (expr, 2));
588 if (TREE_OPERAND (expr, 2) != e2)
596 if (code == COND_EXPR)
597 expr = build3 (code, boolean_type_node, e0, e1, e2);
599 expr = build2 (code, boolean_type_node, e0, e1);
606 /* Check whether COND ==> EXPR. */
607 notcond = invert_truthvalue (cond);
608 e = fold (build2 (TRUTH_OR_EXPR, boolean_type_node,
613 /* Check whether COND ==> not EXPR. */
614 e = fold (build2 (TRUTH_AND_EXPR, boolean_type_node,
622 /* Tries to simplify EXPR using the conditions on entry to LOOP.
623 Record the conditions used for simplification to CONDS_USED.
624 Returns the simplified expression (or EXPR unchanged, if no
625 simplification was possible).*/
628 simplify_using_initial_conditions (struct loop *loop, tree expr,
635 if (TREE_CODE (expr) == INTEGER_CST)
638 for (bb = loop->header;
639 bb != ENTRY_BLOCK_PTR;
640 bb = get_immediate_dominator (CDI_DOMINATORS, bb))
642 e = EDGE_PRED (bb, 0);
643 if (EDGE_COUNT (bb->preds) > 1)
646 if (!(e->flags & (EDGE_TRUE_VALUE | EDGE_FALSE_VALUE)))
649 cond = COND_EXPR_COND (last_stmt (e->src));
650 if (e->flags & EDGE_FALSE_VALUE)
651 cond = invert_truthvalue (cond);
652 exp = tree_simplify_using_condition (cond, expr);
655 *conds_used = fold (build2 (TRUTH_AND_EXPR,
666 /* Stores description of number of iterations of LOOP derived from
667 EXIT (an exit edge of the LOOP) in NITER. Returns true if some
668 useful information could be derived (and fields of NITER has
669 meaning described in comments at struct tree_niter_desc
670 declaration), false otherwise. */
673 number_of_iterations_exit (struct loop *loop, edge exit,
674 struct tree_niter_desc *niter)
676 tree stmt, cond, type;
677 tree op0, base0, step0;
678 tree op1, base1, step1;
681 if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit->src))
684 niter->assumptions = boolean_false_node;
685 stmt = last_stmt (exit->src);
686 if (!stmt || TREE_CODE (stmt) != COND_EXPR)
689 /* We want the condition for staying inside loop. */
690 cond = COND_EXPR_COND (stmt);
691 if (exit->flags & EDGE_TRUE_VALUE)
692 cond = invert_truthvalue (cond);
694 code = TREE_CODE (cond);
708 op0 = TREE_OPERAND (cond, 0);
709 op1 = TREE_OPERAND (cond, 1);
710 type = TREE_TYPE (op0);
712 if (TREE_CODE (type) != INTEGER_TYPE
713 && !POINTER_TYPE_P (type))
716 if (!simple_iv (loop, stmt, op0, &base0, &step0))
718 if (!simple_iv (loop, stmt, op1, &base1, &step1))
721 niter->niter = NULL_TREE;
722 number_of_iterations_cond (type, base0, step0, code, base1, step1,
727 niter->assumptions = simplify_using_outer_evolutions (loop,
729 niter->may_be_zero = simplify_using_outer_evolutions (loop,
731 niter->niter = simplify_using_outer_evolutions (loop, niter->niter);
733 niter->additional_info = boolean_true_node;
735 = simplify_using_initial_conditions (loop,
737 &niter->additional_info);
739 = simplify_using_initial_conditions (loop,
741 &niter->additional_info);
742 return integer_onep (niter->assumptions);
747 Analysis of a number of iterations of a loop by a brute-force evaluation.
751 /* Bound on the number of iterations we try to evaluate. */
753 #define MAX_ITERATIONS_TO_TRACK \
754 ((unsigned) PARAM_VALUE (PARAM_MAX_ITERATIONS_TO_TRACK))
756 /* Returns the loop phi node of LOOP such that ssa name X is derived from its
757 result by a chain of operations such that all but exactly one of their
758 operands are constants. */
761 chain_of_csts_start (struct loop *loop, tree x)
763 tree stmt = SSA_NAME_DEF_STMT (x);
764 basic_block bb = bb_for_stmt (stmt);
768 || !flow_bb_inside_loop_p (loop, bb))
771 if (TREE_CODE (stmt) == PHI_NODE)
773 if (bb == loop->header)
779 if (TREE_CODE (stmt) != MODIFY_EXPR)
782 get_stmt_operands (stmt);
783 if (NUM_VUSES (STMT_VUSE_OPS (stmt)) > 0)
785 if (NUM_V_MAY_DEFS (STMT_V_MAY_DEF_OPS (stmt)) > 0)
787 if (NUM_V_MUST_DEFS (STMT_V_MUST_DEF_OPS (stmt)) > 0)
789 if (NUM_DEFS (STMT_DEF_OPS (stmt)) > 1)
791 uses = STMT_USE_OPS (stmt);
792 if (NUM_USES (uses) != 1)
795 return chain_of_csts_start (loop, USE_OP (uses, 0));
798 /* Determines whether the expression X is derived from a result of a phi node
799 in header of LOOP such that
801 * the derivation of X consists only from operations with constants
802 * the initial value of the phi node is constant
803 * the value of the phi node in the next iteration can be derived from the
804 value in the current iteration by a chain of operations with constants.
806 If such phi node exists, it is returned. If X is a constant, X is returned
807 unchanged. Otherwise NULL_TREE is returned. */
810 get_base_for (struct loop *loop, tree x)
812 tree phi, init, next;
814 if (is_gimple_min_invariant (x))
817 phi = chain_of_csts_start (loop, x);
821 init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
822 next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
824 if (TREE_CODE (next) != SSA_NAME)
827 if (!is_gimple_min_invariant (init))
830 if (chain_of_csts_start (loop, next) != phi)
836 /* Given an expression X, then
838 * if BASE is NULL_TREE, X must be a constant and we return X.
839 * otherwise X is a SSA name, whose value in the considered loop is derived
840 by a chain of operations with constant from a result of a phi node in
841 the header of the loop. Then we return value of X when the value of the
842 result of this phi node is given by the constant BASE. */
845 get_val_for (tree x, tree base)
854 stmt = SSA_NAME_DEF_STMT (x);
855 if (TREE_CODE (stmt) == PHI_NODE)
858 uses = STMT_USE_OPS (stmt);
859 op = USE_OP_PTR (uses, 0);
861 nx = USE_FROM_PTR (op);
862 val = get_val_for (nx, base);
864 val = fold (TREE_OPERAND (stmt, 1));
870 /* Tries to count the number of iterations of LOOP till it exits by EXIT
871 by brute force -- i.e. by determining the value of the operands of the
872 condition at EXIT in first few iterations of the loop (assuming that
873 these values are constant) and determining the first one in that the
874 condition is not satisfied. Returns the constant giving the number
875 of the iterations of LOOP if successful, chrec_dont_know otherwise. */
878 loop_niter_by_eval (struct loop *loop, edge exit)
880 tree cond, cnd, acnd;
881 tree op[2], val[2], next[2], aval[2], phi[2];
885 cond = last_stmt (exit->src);
886 if (!cond || TREE_CODE (cond) != COND_EXPR)
887 return chrec_dont_know;
889 cnd = COND_EXPR_COND (cond);
890 if (exit->flags & EDGE_TRUE_VALUE)
891 cnd = invert_truthvalue (cnd);
893 cmp = TREE_CODE (cnd);
902 for (j = 0; j < 2; j++)
903 op[j] = TREE_OPERAND (cnd, j);
907 return chrec_dont_know;
910 for (j = 0; j < 2; j++)
912 phi[j] = get_base_for (loop, op[j]);
914 return chrec_dont_know;
917 for (j = 0; j < 2; j++)
919 if (TREE_CODE (phi[j]) == PHI_NODE)
921 val[j] = PHI_ARG_DEF_FROM_EDGE (phi[j], loop_preheader_edge (loop));
922 next[j] = PHI_ARG_DEF_FROM_EDGE (phi[j], loop_latch_edge (loop));
932 for (i = 0; i < MAX_ITERATIONS_TO_TRACK; i++)
934 for (j = 0; j < 2; j++)
935 aval[j] = get_val_for (op[j], val[j]);
937 acnd = fold (build2 (cmp, boolean_type_node, aval[0], aval[1]));
940 if (dump_file && (dump_flags & TDF_DETAILS))
942 "Proved that loop %d iterates %d times using brute force.\n",
944 return build_int_cst (unsigned_type_node, i);
947 for (j = 0; j < 2; j++)
948 val[j] = get_val_for (next[j], val[j]);
951 return chrec_dont_know;
954 /* Finds the exit of the LOOP by that the loop exits after a constant
955 number of iterations and stores the exit edge to *EXIT. The constant
956 giving the number of iterations of LOOP is returned. The number of
957 iterations is determined using loop_niter_by_eval (i.e. by brute force
958 evaluation). If we are unable to find the exit for that loop_niter_by_eval
959 determines the number of iterations, chrec_dont_know is returned. */
962 find_loop_niter_by_eval (struct loop *loop, edge *exit)
965 edge *exits = get_loop_exit_edges (loop, &n_exits);
967 tree niter = NULL_TREE, aniter;
970 for (i = 0; i < n_exits; i++)
973 if (!just_once_each_iteration_p (loop, ex->src))
976 aniter = loop_niter_by_eval (loop, ex);
977 if (chrec_contains_undetermined (aniter)
978 || TREE_CODE (aniter) != INTEGER_CST)
982 && !nonzero_p (fold (build2 (LT_EXPR, boolean_type_node,
991 return niter ? niter : chrec_dont_know;
996 Analysis of upper bounds on number of iterations of a loop.
1000 /* Records that AT_STMT is executed at most BOUND times in LOOP. The
1001 additional condition ADDITIONAL is recorded with the bound. */
1004 record_estimate (struct loop *loop, tree bound, tree additional, tree at_stmt)
1006 struct nb_iter_bound *elt = xmalloc (sizeof (struct nb_iter_bound));
1008 if (dump_file && (dump_flags & TDF_DETAILS))
1010 fprintf (dump_file, "Statements after ");
1011 print_generic_expr (dump_file, at_stmt, TDF_SLIM);
1012 fprintf (dump_file, " are executed at most ");
1013 print_generic_expr (dump_file, bound, TDF_SLIM);
1014 fprintf (dump_file, " times in loop %d.\n", loop->num);
1018 elt->at_stmt = at_stmt;
1019 elt->additional = additional;
1020 elt->next = loop->bounds;
1024 /* Records estimates on numbers of iterations of LOOP. */
1027 estimate_numbers_of_iterations_loop (struct loop *loop)
1031 unsigned i, n_exits;
1032 struct tree_niter_desc niter_desc;
1034 exits = get_loop_exit_edges (loop, &n_exits);
1035 for (i = 0; i < n_exits; i++)
1037 if (!number_of_iterations_exit (loop, exits[i], &niter_desc))
1040 niter = niter_desc.niter;
1041 type = TREE_TYPE (niter);
1042 if (!zero_p (niter_desc.may_be_zero)
1043 && !nonzero_p (niter_desc.may_be_zero))
1044 niter = build3 (COND_EXPR, type, niter_desc.may_be_zero,
1045 build_int_cst_type (type, 0),
1047 record_estimate (loop, niter,
1048 niter_desc.additional_info,
1049 last_stmt (exits[i]->src));
1053 /* Analyzes the bounds of arrays accessed in the loop. */
1054 if (loop->estimated_nb_iterations == NULL_TREE)
1056 varray_type datarefs;
1057 VARRAY_GENERIC_PTR_INIT (datarefs, 3, "datarefs");
1058 find_data_references_in_loop (loop, &datarefs);
1059 free_data_refs (datarefs);
1063 /* Records estimates on numbers of iterations of LOOPS. */
1066 estimate_numbers_of_iterations (struct loops *loops)
1071 for (i = 1; i < loops->num; i++)
1073 loop = loops->parray[i];
1075 estimate_numbers_of_iterations_loop (loop);
1079 /* If A > B, returns -1. If A == B, returns 0. If A < B, returns 1.
1080 If neither of these relations can be proved, returns 2. */
1083 compare_trees (tree a, tree b)
1085 tree typea = TREE_TYPE (a), typeb = TREE_TYPE (b);
1088 if (TYPE_PRECISION (typea) > TYPE_PRECISION (typeb))
1093 a = fold_convert (type, a);
1094 b = fold_convert (type, b);
1096 if (nonzero_p (fold (build2 (EQ_EXPR, boolean_type_node, a, b))))
1098 if (nonzero_p (fold (build2 (LT_EXPR, boolean_type_node, a, b))))
1100 if (nonzero_p (fold (build2 (GT_EXPR, boolean_type_node, a, b))))
1106 /* Returns the largest value obtainable by casting something in INNER type to
1110 upper_bound_in_type (tree outer, tree inner)
1112 unsigned HOST_WIDE_INT lo, hi;
1113 unsigned bits = TYPE_PRECISION (inner);
1115 if (TYPE_UNSIGNED (outer) || TYPE_UNSIGNED (inner))
1117 /* Zero extending in these cases. */
1118 if (bits <= HOST_BITS_PER_WIDE_INT)
1121 lo = (~(unsigned HOST_WIDE_INT) 0)
1122 >> (HOST_BITS_PER_WIDE_INT - bits);
1126 hi = (~(unsigned HOST_WIDE_INT) 0)
1127 >> (2 * HOST_BITS_PER_WIDE_INT - bits);
1128 lo = ~(unsigned HOST_WIDE_INT) 0;
1133 /* Sign extending in these cases. */
1134 if (bits <= HOST_BITS_PER_WIDE_INT)
1137 lo = (~(unsigned HOST_WIDE_INT) 0)
1138 >> (HOST_BITS_PER_WIDE_INT - bits) >> 1;
1142 hi = (~(unsigned HOST_WIDE_INT) 0)
1143 >> (2 * HOST_BITS_PER_WIDE_INT - bits) >> 1;
1144 lo = ~(unsigned HOST_WIDE_INT) 0;
1148 return fold_convert (outer,
1149 build_int_cst_wide (inner, lo, hi));
1152 /* Returns the smallest value obtainable by casting something in INNER type to
1156 lower_bound_in_type (tree outer, tree inner)
1158 unsigned HOST_WIDE_INT lo, hi;
1159 unsigned bits = TYPE_PRECISION (inner);
1161 if (TYPE_UNSIGNED (outer) || TYPE_UNSIGNED (inner))
1163 else if (bits <= HOST_BITS_PER_WIDE_INT)
1165 hi = ~(unsigned HOST_WIDE_INT) 0;
1166 lo = (~(unsigned HOST_WIDE_INT) 0) << (bits - 1);
1170 hi = (~(unsigned HOST_WIDE_INT) 0) << (bits - HOST_BITS_PER_WIDE_INT - 1);
1174 return fold_convert (outer,
1175 build_int_cst_wide (inner, lo, hi));
1178 /* Returns true if statement S1 dominates statement S2. */
1181 stmt_dominates_stmt_p (tree s1, tree s2)
1183 basic_block bb1 = bb_for_stmt (s1), bb2 = bb_for_stmt (s2);
1191 block_stmt_iterator bsi;
1193 for (bsi = bsi_start (bb1); bsi_stmt (bsi) != s2; bsi_next (&bsi))
1194 if (bsi_stmt (bsi) == s1)
1200 return dominated_by_p (CDI_DOMINATORS, bb2, bb1);
1203 /* Checks whether it is correct to count the induction variable BASE + STEP * I
1204 at AT_STMT in wider TYPE, using the fact that statement OF is executed at
1205 most BOUND times in the loop. If it is possible, return the value of step
1206 of the induction variable in the TYPE, otherwise return NULL_TREE.
1208 ADDITIONAL is the additional condition recorded for operands of the bound.
1209 This is useful in the following case, created by loop header copying:
1218 If the n > 0 condition is taken into account, the number of iterations of the
1219 loop can be expressed as n - 1. If the type of n is signed, the ADDITIONAL
1220 assumption "n > 0" says us that the value of the number of iterations is at
1221 most MAX_TYPE - 1 (without this assumption, it might overflow). */
1224 can_count_iv_in_wider_type_bound (tree type, tree base, tree step,
1230 tree inner_type = TREE_TYPE (base), b, bplusstep, new_step, new_step_abs;
1231 tree valid_niter, extreme, unsigned_type, delta, bound_type;
1234 b = fold_convert (type, base);
1235 bplusstep = fold_convert (type,
1236 fold (build2 (PLUS_EXPR, inner_type, base, step)));
1237 new_step = fold (build2 (MINUS_EXPR, type, bplusstep, b));
1238 if (TREE_CODE (new_step) != INTEGER_CST)
1241 switch (compare_trees (bplusstep, b))
1244 extreme = upper_bound_in_type (type, inner_type);
1245 delta = fold (build2 (MINUS_EXPR, type, extreme, b));
1246 new_step_abs = new_step;
1250 extreme = lower_bound_in_type (type, inner_type);
1251 new_step_abs = fold (build1 (NEGATE_EXPR, type, new_step));
1252 delta = fold (build2 (MINUS_EXPR, type, b, extreme));
1262 unsigned_type = unsigned_type_for (type);
1263 delta = fold_convert (unsigned_type, delta);
1264 new_step_abs = fold_convert (unsigned_type, new_step_abs);
1265 valid_niter = fold (build2 (FLOOR_DIV_EXPR, unsigned_type,
1266 delta, new_step_abs));
1268 bound_type = TREE_TYPE (bound);
1269 if (TYPE_PRECISION (type) > TYPE_PRECISION (bound_type))
1270 bound = fold_convert (unsigned_type, bound);
1272 valid_niter = fold_convert (bound_type, valid_niter);
1274 if (at_stmt && stmt_dominates_stmt_p (of, at_stmt))
1276 /* After the statement OF we know that anything is executed at most
1278 cond = build2 (GE_EXPR, boolean_type_node, valid_niter, bound);
1282 /* Before the statement OF we know that anything is executed at most
1284 cond = build2 (GT_EXPR, boolean_type_node, valid_niter, bound);
1288 if (nonzero_p (cond))
1291 /* Try taking additional conditions into account. */
1292 cond = build2 (TRUTH_OR_EXPR, boolean_type_node,
1293 invert_truthvalue (additional),
1296 if (nonzero_p (cond))
1302 /* Checks whether it is correct to count the induction variable BASE + STEP * I
1303 at AT_STMT in wider TYPE, using the bounds on numbers of iterations of a
1304 LOOP. If it is possible, return the value of step of the induction variable
1305 in the TYPE, otherwise return NULL_TREE. */
1308 can_count_iv_in_wider_type (struct loop *loop, tree type, tree base, tree step,
1311 struct nb_iter_bound *bound;
1314 for (bound = loop->bounds; bound; bound = bound->next)
1316 new_step = can_count_iv_in_wider_type_bound (type, base, step,
1329 /* Frees the information on upper bounds on numbers of iterations of LOOP. */
1332 free_numbers_of_iterations_estimates_loop (struct loop *loop)
1334 struct nb_iter_bound *bound, *next;
1336 for (bound = loop->bounds; bound; bound = next)
1342 loop->bounds = NULL;
1345 /* Frees the information on upper bounds on numbers of iterations of LOOPS. */
1348 free_numbers_of_iterations_estimates (struct loops *loops)
1353 for (i = 1; i < loops->num; i++)
1355 loop = loops->parray[i];
1357 free_numbers_of_iterations_estimates_loop (loop);