1 /* Scalar evolution detector.
2 Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Free Software
4 Contributed by Sebastian Pop <s.pop@laposte.net>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
25 This pass analyzes the evolution of scalar variables in loop
26 structures. The algorithm is based on the SSA representation,
27 and on the loop hierarchy tree. This algorithm is not based on
28 the notion of versions of a variable, as it was the case for the
29 previous implementations of the scalar evolution algorithm, but
30 it assumes that each defined name is unique.
32 The notation used in this file is called "chains of recurrences",
33 and has been proposed by Eugene Zima, Robert Van Engelen, and
34 others for describing induction variables in programs. For example
35 "b -> {0, +, 2}_1" means that the scalar variable "b" is equal to 0
36 when entering in the loop_1 and has a step 2 in this loop, in other
37 words "for (b = 0; b < N; b+=2);". Note that the coefficients of
38 this chain of recurrence (or chrec [shrek]) can contain the name of
39 other variables, in which case they are called parametric chrecs.
40 For example, "b -> {a, +, 2}_1" means that the initial value of "b"
41 is the value of "a". In most of the cases these parametric chrecs
42 are fully instantiated before their use because symbolic names can
43 hide some difficult cases such as self-references described later
44 (see the Fibonacci example).
46 A short sketch of the algorithm is:
48 Given a scalar variable to be analyzed, follow the SSA edge to
51 - When the definition is a GIMPLE_ASSIGN: if the right hand side
52 (RHS) of the definition cannot be statically analyzed, the answer
53 of the analyzer is: "don't know".
54 Otherwise, for all the variables that are not yet analyzed in the
55 RHS, try to determine their evolution, and finally try to
56 evaluate the operation of the RHS that gives the evolution
57 function of the analyzed variable.
59 - When the definition is a condition-phi-node: determine the
60 evolution function for all the branches of the phi node, and
61 finally merge these evolutions (see chrec_merge).
63 - When the definition is a loop-phi-node: determine its initial
64 condition, that is the SSA edge defined in an outer loop, and
65 keep it symbolic. Then determine the SSA edges that are defined
66 in the body of the loop. Follow the inner edges until ending on
67 another loop-phi-node of the same analyzed loop. If the reached
68 loop-phi-node is not the starting loop-phi-node, then we keep
69 this definition under a symbolic form. If the reached
70 loop-phi-node is the same as the starting one, then we compute a
71 symbolic stride on the return path. The result is then the
72 symbolic chrec {initial_condition, +, symbolic_stride}_loop.
76 Example 1: Illustration of the basic algorithm.
82 | if (c > 10) exit_loop
85 Suppose that we want to know the number of iterations of the
86 loop_1. The exit_loop is controlled by a COND_EXPR (c > 10). We
87 ask the scalar evolution analyzer two questions: what's the
88 scalar evolution (scev) of "c", and what's the scev of "10". For
89 "10" the answer is "10" since it is a scalar constant. For the
90 scalar variable "c", it follows the SSA edge to its definition,
91 "c = b + 1", and then asks again what's the scev of "b".
92 Following the SSA edge, we end on a loop-phi-node "b = phi (a,
93 c)", where the initial condition is "a", and the inner loop edge
94 is "c". The initial condition is kept under a symbolic form (it
95 may be the case that the copy constant propagation has done its
96 work and we end with the constant "3" as one of the edges of the
97 loop-phi-node). The update edge is followed to the end of the
98 loop, and until reaching again the starting loop-phi-node: b -> c
99 -> b. At this point we have drawn a path from "b" to "b" from
100 which we compute the stride in the loop: in this example it is
101 "+1". The resulting scev for "b" is "b -> {a, +, 1}_1". Now
102 that the scev for "b" is known, it is possible to compute the
103 scev for "c", that is "c -> {a + 1, +, 1}_1". In order to
104 determine the number of iterations in the loop_1, we have to
105 instantiate_parameters (loop_1, {a + 1, +, 1}_1), that gives after some
106 more analysis the scev {4, +, 1}_1, or in other words, this is
107 the function "f (x) = x + 4", where x is the iteration count of
108 the loop_1. Now we have to solve the inequality "x + 4 > 10",
109 and take the smallest iteration number for which the loop is
110 exited: x = 7. This loop runs from x = 0 to x = 7, and in total
111 there are 8 iterations. In terms of loop normalization, we have
112 created a variable that is implicitly defined, "x" or just "_1",
113 and all the other analyzed scalars of the loop are defined in
114 function of this variable:
120 or in terms of a C program:
123 | for (x = 0; x <= 7; x++)
129 Example 2a: Illustration of the algorithm on nested loops.
140 For analyzing the scalar evolution of "a", the algorithm follows
141 the SSA edge into the loop's body: "a -> b". "b" is an inner
142 loop-phi-node, and its analysis as in Example 1, gives:
147 Following the SSA edge for the initial condition, we end on "c = a
148 + 2", and then on the starting loop-phi-node "a". From this point,
149 the loop stride is computed: back on "c = a + 2" we get a "+2" in
150 the loop_1, then on the loop-phi-node "b" we compute the overall
151 effect of the inner loop that is "b = c + 30", and we get a "+30"
152 in the loop_1. That means that the overall stride in loop_1 is
153 equal to "+32", and the result is:
158 Example 2b: Multivariate chains of recurrences.
171 Analyzing the access function of array A with
172 instantiate_parameters (loop_1, "j + k"), we obtain the
173 instantiation and the analysis of the scalar variables "j" and "k"
174 in loop_1. This leads to the scalar evolution {4, +, 1}_1: the end
175 value of loop_2 for "j" is 4, and the evolution of "k" in loop_1 is
176 {0, +, 1}_1. To obtain the evolution function in loop_3 and
177 instantiate the scalar variables up to loop_1, one has to use:
178 instantiate_scev (block_before_loop (loop_1), loop_3, "j + k").
179 The result of this call is {{0, +, 1}_1, +, 1}_2.
181 Example 3: Higher degree polynomials.
195 instantiate_parameters (loop_1, {5, +, a}_1) -> {5, +, 2, +, 1}_1
196 instantiate_parameters (loop_1, {5 + a, +, a}_1) -> {7, +, 3, +, 1}_1
198 Example 4: Lucas, Fibonacci, or mixers in general.
210 The syntax "(1, c)_1" stands for a PEELED_CHREC that has the
211 following semantics: during the first iteration of the loop_1, the
212 variable contains the value 1, and then it contains the value "c".
213 Note that this syntax is close to the syntax of the loop-phi-node:
214 "a -> (1, c)_1" vs. "a = phi (1, c)".
216 The symbolic chrec representation contains all the semantics of the
217 original code. What is more difficult is to use this information.
219 Example 5: Flip-flops, or exchangers.
231 Based on these symbolic chrecs, it is possible to refine this
232 information into the more precise PERIODIC_CHRECs:
237 This transformation is not yet implemented.
241 You can find a more detailed description of the algorithm in:
242 http://icps.u-strasbg.fr/~pop/DEA_03_Pop.pdf
243 http://icps.u-strasbg.fr/~pop/DEA_03_Pop.ps.gz. But note that
244 this is a preliminary report and some of the details of the
245 algorithm have changed. I'm working on a research report that
246 updates the description of the algorithms to reflect the design
247 choices used in this implementation.
249 A set of slides show a high level overview of the algorithm and run
250 an example through the scalar evolution analyzer:
251 http://cri.ensmp.fr/~pop/gcc/mar04/slides.pdf
253 The slides that I have presented at the GCC Summit'04 are available
254 at: http://cri.ensmp.fr/~pop/gcc/20040604/gccsummit-lno-spop.pdf
259 #include "coretypes.h"
265 /* These RTL headers are needed for basic-block.h. */
267 #include "basic-block.h"
268 #include "diagnostic.h"
269 #include "tree-flow.h"
270 #include "tree-dump.h"
273 #include "tree-chrec.h"
274 #include "tree-scalar-evolution.h"
275 #include "tree-pass.h"
279 static tree analyze_scalar_evolution_1 (struct loop *, tree, tree);
281 /* The cached information about an SSA name VAR, claiming that below
282 basic block INSTANTIATED_BELOW, the value of VAR can be expressed
285 struct scev_info_str GTY(())
287 basic_block instantiated_below;
292 /* Counters for the scev database. */
293 static unsigned nb_set_scev = 0;
294 static unsigned nb_get_scev = 0;
296 /* The following trees are unique elements. Thus the comparison of
297 another element to these elements should be done on the pointer to
298 these trees, and not on their value. */
300 /* The SSA_NAMEs that are not yet analyzed are qualified with NULL_TREE. */
301 tree chrec_not_analyzed_yet;
303 /* Reserved to the cases where the analyzer has detected an
304 undecidable property at compile time. */
305 tree chrec_dont_know;
307 /* When the analyzer has detected that a property will never
308 happen, then it qualifies it with chrec_known. */
311 static GTY ((param_is (struct scev_info_str))) htab_t scalar_evolution_info;
314 /* Constructs a new SCEV_INFO_STR structure for VAR and INSTANTIATED_BELOW. */
316 static inline struct scev_info_str *
317 new_scev_info_str (basic_block instantiated_below, tree var)
319 struct scev_info_str *res;
321 res = GGC_NEW (struct scev_info_str);
323 res->chrec = chrec_not_analyzed_yet;
324 res->instantiated_below = instantiated_below;
329 /* Computes a hash function for database element ELT. */
332 hash_scev_info (const void *elt)
334 return SSA_NAME_VERSION (((const struct scev_info_str *) elt)->var);
337 /* Compares database elements E1 and E2. */
340 eq_scev_info (const void *e1, const void *e2)
342 const struct scev_info_str *elt1 = (const struct scev_info_str *) e1;
343 const struct scev_info_str *elt2 = (const struct scev_info_str *) e2;
345 return (elt1->var == elt2->var
346 && elt1->instantiated_below == elt2->instantiated_below);
349 /* Deletes database element E. */
352 del_scev_info (void *e)
357 /* Get the scalar evolution of VAR for INSTANTIATED_BELOW basic block.
358 A first query on VAR returns chrec_not_analyzed_yet. */
361 find_var_scev_info (basic_block instantiated_below, tree var)
363 struct scev_info_str *res;
364 struct scev_info_str tmp;
368 tmp.instantiated_below = instantiated_below;
369 slot = htab_find_slot (scalar_evolution_info, &tmp, INSERT);
372 *slot = new_scev_info_str (instantiated_below, var);
373 res = (struct scev_info_str *) *slot;
378 /* Return true when CHREC contains symbolic names defined in
382 chrec_contains_symbols_defined_in_loop (const_tree chrec, unsigned loop_nb)
386 if (chrec == NULL_TREE)
389 if (is_gimple_min_invariant (chrec))
392 if (TREE_CODE (chrec) == VAR_DECL
393 || TREE_CODE (chrec) == PARM_DECL
394 || TREE_CODE (chrec) == FUNCTION_DECL
395 || TREE_CODE (chrec) == LABEL_DECL
396 || TREE_CODE (chrec) == RESULT_DECL
397 || TREE_CODE (chrec) == FIELD_DECL)
400 if (TREE_CODE (chrec) == SSA_NAME)
402 gimple def = SSA_NAME_DEF_STMT (chrec);
403 struct loop *def_loop = loop_containing_stmt (def);
404 struct loop *loop = get_loop (loop_nb);
406 if (def_loop == NULL)
409 if (loop == def_loop || flow_loop_nested_p (loop, def_loop))
415 n = TREE_OPERAND_LENGTH (chrec);
416 for (i = 0; i < n; i++)
417 if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (chrec, i),
423 /* Return true when PHI is a loop-phi-node. */
426 loop_phi_node_p (gimple phi)
428 /* The implementation of this function is based on the following
429 property: "all the loop-phi-nodes of a loop are contained in the
430 loop's header basic block". */
432 return loop_containing_stmt (phi)->header == gimple_bb (phi);
435 /* Compute the scalar evolution for EVOLUTION_FN after crossing LOOP.
436 In general, in the case of multivariate evolutions we want to get
437 the evolution in different loops. LOOP specifies the level for
438 which to get the evolution.
442 | for (j = 0; j < 100; j++)
444 | for (k = 0; k < 100; k++)
446 | i = k + j; - Here the value of i is a function of j, k.
448 | ... = i - Here the value of i is a function of j.
450 | ... = i - Here the value of i is a scalar.
456 | i_1 = phi (i_0, i_2)
460 This loop has the same effect as:
461 LOOP_1 has the same effect as:
465 The overall effect of the loop, "i_0 + 20" in the previous example,
466 is obtained by passing in the parameters: LOOP = 1,
467 EVOLUTION_FN = {i_0, +, 2}_1.
471 compute_overall_effect_of_inner_loop (struct loop *loop, tree evolution_fn)
475 if (evolution_fn == chrec_dont_know)
476 return chrec_dont_know;
478 else if (TREE_CODE (evolution_fn) == POLYNOMIAL_CHREC)
480 struct loop *inner_loop = get_chrec_loop (evolution_fn);
482 if (inner_loop == loop
483 || flow_loop_nested_p (loop, inner_loop))
485 tree nb_iter = number_of_latch_executions (inner_loop);
487 if (nb_iter == chrec_dont_know)
488 return chrec_dont_know;
493 /* evolution_fn is the evolution function in LOOP. Get
494 its value in the nb_iter-th iteration. */
495 res = chrec_apply (inner_loop->num, evolution_fn, nb_iter);
497 /* Continue the computation until ending on a parent of LOOP. */
498 return compute_overall_effect_of_inner_loop (loop, res);
505 /* If the evolution function is an invariant, there is nothing to do. */
506 else if (no_evolution_in_loop_p (evolution_fn, loop->num, &val) && val)
510 return chrec_dont_know;
513 /* Determine whether the CHREC is always positive/negative. If the expression
514 cannot be statically analyzed, return false, otherwise set the answer into
518 chrec_is_positive (tree chrec, bool *value)
520 bool value0, value1, value2;
521 tree end_value, nb_iter;
523 switch (TREE_CODE (chrec))
525 case POLYNOMIAL_CHREC:
526 if (!chrec_is_positive (CHREC_LEFT (chrec), &value0)
527 || !chrec_is_positive (CHREC_RIGHT (chrec), &value1))
530 /* FIXME -- overflows. */
531 if (value0 == value1)
537 /* Otherwise the chrec is under the form: "{-197, +, 2}_1",
538 and the proof consists in showing that the sign never
539 changes during the execution of the loop, from 0 to
540 loop->nb_iterations. */
541 if (!evolution_function_is_affine_p (chrec))
544 nb_iter = number_of_latch_executions (get_chrec_loop (chrec));
545 if (chrec_contains_undetermined (nb_iter))
549 /* TODO -- If the test is after the exit, we may decrease the number of
550 iterations by one. */
552 nb_iter = chrec_fold_minus (type, nb_iter, build_int_cst (type, 1));
555 end_value = chrec_apply (CHREC_VARIABLE (chrec), chrec, nb_iter);
557 if (!chrec_is_positive (end_value, &value2))
561 return value0 == value1;
564 *value = (tree_int_cst_sgn (chrec) == 1);
572 /* Associate CHREC to SCALAR. */
575 set_scalar_evolution (basic_block instantiated_below, tree scalar, tree chrec)
579 if (TREE_CODE (scalar) != SSA_NAME)
582 scalar_info = find_var_scev_info (instantiated_below, scalar);
586 if (dump_flags & TDF_DETAILS)
588 fprintf (dump_file, "(set_scalar_evolution \n");
589 fprintf (dump_file, " instantiated_below = %d \n",
590 instantiated_below->index);
591 fprintf (dump_file, " (scalar = ");
592 print_generic_expr (dump_file, scalar, 0);
593 fprintf (dump_file, ")\n (scalar_evolution = ");
594 print_generic_expr (dump_file, chrec, 0);
595 fprintf (dump_file, "))\n");
597 if (dump_flags & TDF_STATS)
601 *scalar_info = chrec;
604 /* Retrieve the chrec associated to SCALAR instantiated below
605 INSTANTIATED_BELOW block. */
608 get_scalar_evolution (basic_block instantiated_below, tree scalar)
614 if (dump_flags & TDF_DETAILS)
616 fprintf (dump_file, "(get_scalar_evolution \n");
617 fprintf (dump_file, " (scalar = ");
618 print_generic_expr (dump_file, scalar, 0);
619 fprintf (dump_file, ")\n");
621 if (dump_flags & TDF_STATS)
625 switch (TREE_CODE (scalar))
628 res = *find_var_scev_info (instantiated_below, scalar);
638 res = chrec_not_analyzed_yet;
642 if (dump_file && (dump_flags & TDF_DETAILS))
644 fprintf (dump_file, " (scalar_evolution = ");
645 print_generic_expr (dump_file, res, 0);
646 fprintf (dump_file, "))\n");
652 /* Helper function for add_to_evolution. Returns the evolution
653 function for an assignment of the form "a = b + c", where "a" and
654 "b" are on the strongly connected component. CHREC_BEFORE is the
655 information that we already have collected up to this point.
656 TO_ADD is the evolution of "c".
658 When CHREC_BEFORE has an evolution part in LOOP_NB, add to this
659 evolution the expression TO_ADD, otherwise construct an evolution
660 part for this loop. */
663 add_to_evolution_1 (unsigned loop_nb, tree chrec_before, tree to_add,
666 tree type, left, right;
667 struct loop *loop = get_loop (loop_nb), *chloop;
669 switch (TREE_CODE (chrec_before))
671 case POLYNOMIAL_CHREC:
672 chloop = get_chrec_loop (chrec_before);
674 || flow_loop_nested_p (chloop, loop))
678 type = chrec_type (chrec_before);
680 /* When there is no evolution part in this loop, build it. */
685 right = SCALAR_FLOAT_TYPE_P (type)
686 ? build_real (type, dconst0)
687 : build_int_cst (type, 0);
691 var = CHREC_VARIABLE (chrec_before);
692 left = CHREC_LEFT (chrec_before);
693 right = CHREC_RIGHT (chrec_before);
696 to_add = chrec_convert (type, to_add, at_stmt);
697 right = chrec_convert_rhs (type, right, at_stmt);
698 right = chrec_fold_plus (chrec_type (right), right, to_add);
699 return build_polynomial_chrec (var, left, right);
703 gcc_assert (flow_loop_nested_p (loop, chloop));
705 /* Search the evolution in LOOP_NB. */
706 left = add_to_evolution_1 (loop_nb, CHREC_LEFT (chrec_before),
708 right = CHREC_RIGHT (chrec_before);
709 right = chrec_convert_rhs (chrec_type (left), right, at_stmt);
710 return build_polynomial_chrec (CHREC_VARIABLE (chrec_before),
715 /* These nodes do not depend on a loop. */
716 if (chrec_before == chrec_dont_know)
717 return chrec_dont_know;
720 right = chrec_convert_rhs (chrec_type (left), to_add, at_stmt);
721 return build_polynomial_chrec (loop_nb, left, right);
725 /* Add TO_ADD to the evolution part of CHREC_BEFORE in the dimension
728 Description (provided for completeness, for those who read code in
729 a plane, and for my poor 62 bytes brain that would have forgotten
730 all this in the next two or three months):
732 The algorithm of translation of programs from the SSA representation
733 into the chrecs syntax is based on a pattern matching. After having
734 reconstructed the overall tree expression for a loop, there are only
735 two cases that can arise:
737 1. a = loop-phi (init, a + expr)
738 2. a = loop-phi (init, expr)
740 where EXPR is either a scalar constant with respect to the analyzed
741 loop (this is a degree 0 polynomial), or an expression containing
742 other loop-phi definitions (these are higher degree polynomials).
749 | a = phi (init, a + 5)
756 | a = phi (inita, 2 * b + 3)
757 | b = phi (initb, b + 1)
760 For the first case, the semantics of the SSA representation is:
762 | a (x) = init + \sum_{j = 0}^{x - 1} expr (j)
764 that is, there is a loop index "x" that determines the scalar value
765 of the variable during the loop execution. During the first
766 iteration, the value is that of the initial condition INIT, while
767 during the subsequent iterations, it is the sum of the initial
768 condition with the sum of all the values of EXPR from the initial
769 iteration to the before last considered iteration.
771 For the second case, the semantics of the SSA program is:
773 | a (x) = init, if x = 0;
774 | expr (x - 1), otherwise.
776 The second case corresponds to the PEELED_CHREC, whose syntax is
777 close to the syntax of a loop-phi-node:
779 | phi (init, expr) vs. (init, expr)_x
781 The proof of the translation algorithm for the first case is a
782 proof by structural induction based on the degree of EXPR.
785 When EXPR is a constant with respect to the analyzed loop, or in
786 other words when EXPR is a polynomial of degree 0, the evolution of
787 the variable A in the loop is an affine function with an initial
788 condition INIT, and a step EXPR. In order to show this, we start
789 from the semantics of the SSA representation:
791 f (x) = init + \sum_{j = 0}^{x - 1} expr (j)
793 and since "expr (j)" is a constant with respect to "j",
795 f (x) = init + x * expr
797 Finally, based on the semantics of the pure sum chrecs, by
798 identification we get the corresponding chrecs syntax:
800 f (x) = init * \binom{x}{0} + expr * \binom{x}{1}
801 f (x) -> {init, +, expr}_x
804 Suppose that EXPR is a polynomial of degree N with respect to the
805 analyzed loop_x for which we have already determined that it is
806 written under the chrecs syntax:
808 | expr (x) -> {b_0, +, b_1, +, ..., +, b_{n-1}} (x)
810 We start from the semantics of the SSA program:
812 | f (x) = init + \sum_{j = 0}^{x - 1} expr (j)
814 | f (x) = init + \sum_{j = 0}^{x - 1}
815 | (b_0 * \binom{j}{0} + ... + b_{n-1} * \binom{j}{n-1})
817 | f (x) = init + \sum_{j = 0}^{x - 1}
818 | \sum_{k = 0}^{n - 1} (b_k * \binom{j}{k})
820 | f (x) = init + \sum_{k = 0}^{n - 1}
821 | (b_k * \sum_{j = 0}^{x - 1} \binom{j}{k})
823 | f (x) = init + \sum_{k = 0}^{n - 1}
824 | (b_k * \binom{x}{k + 1})
826 | f (x) = init + b_0 * \binom{x}{1} + ...
827 | + b_{n-1} * \binom{x}{n}
829 | f (x) = init * \binom{x}{0} + b_0 * \binom{x}{1} + ...
830 | + b_{n-1} * \binom{x}{n}
833 And finally from the definition of the chrecs syntax, we identify:
834 | f (x) -> {init, +, b_0, +, ..., +, b_{n-1}}_x
836 This shows the mechanism that stands behind the add_to_evolution
837 function. An important point is that the use of symbolic
838 parameters avoids the need of an analysis schedule.
845 | a = phi (inita, a + 2 + b)
846 | b = phi (initb, b + 1)
849 When analyzing "a", the algorithm keeps "b" symbolically:
851 | a -> {inita, +, 2 + b}_1
853 Then, after instantiation, the analyzer ends on the evolution:
855 | a -> {inita, +, 2 + initb, +, 1}_1
860 add_to_evolution (unsigned loop_nb, tree chrec_before, enum tree_code code,
861 tree to_add, gimple at_stmt)
863 tree type = chrec_type (to_add);
864 tree res = NULL_TREE;
866 if (to_add == NULL_TREE)
869 /* TO_ADD is either a scalar, or a parameter. TO_ADD is not
870 instantiated at this point. */
871 if (TREE_CODE (to_add) == POLYNOMIAL_CHREC)
872 /* This should not happen. */
873 return chrec_dont_know;
875 if (dump_file && (dump_flags & TDF_DETAILS))
877 fprintf (dump_file, "(add_to_evolution \n");
878 fprintf (dump_file, " (loop_nb = %d)\n", loop_nb);
879 fprintf (dump_file, " (chrec_before = ");
880 print_generic_expr (dump_file, chrec_before, 0);
881 fprintf (dump_file, ")\n (to_add = ");
882 print_generic_expr (dump_file, to_add, 0);
883 fprintf (dump_file, ")\n");
886 if (code == MINUS_EXPR)
887 to_add = chrec_fold_multiply (type, to_add, SCALAR_FLOAT_TYPE_P (type)
888 ? build_real (type, dconstm1)
889 : build_int_cst_type (type, -1));
891 res = add_to_evolution_1 (loop_nb, chrec_before, to_add, at_stmt);
893 if (dump_file && (dump_flags & TDF_DETAILS))
895 fprintf (dump_file, " (res = ");
896 print_generic_expr (dump_file, res, 0);
897 fprintf (dump_file, "))\n");
903 /* Helper function. */
906 set_nb_iterations_in_loop (struct loop *loop,
909 if (dump_file && (dump_flags & TDF_DETAILS))
911 fprintf (dump_file, " (set_nb_iterations_in_loop = ");
912 print_generic_expr (dump_file, res, 0);
913 fprintf (dump_file, "))\n");
916 loop->nb_iterations = res;
922 /* This section selects the loops that will be good candidates for the
923 scalar evolution analysis. For the moment, greedily select all the
924 loop nests we could analyze. */
926 /* For a loop with a single exit edge, return the COND_EXPR that
927 guards the exit edge. If the expression is too difficult to
928 analyze, then give up. */
931 get_loop_exit_condition (const struct loop *loop)
934 edge exit_edge = single_exit (loop);
936 if (dump_file && (dump_flags & TDF_DETAILS))
937 fprintf (dump_file, "(get_loop_exit_condition \n ");
943 stmt = last_stmt (exit_edge->src);
944 if (gimple_code (stmt) == GIMPLE_COND)
948 if (dump_file && (dump_flags & TDF_DETAILS))
950 print_gimple_stmt (dump_file, res, 0, 0);
951 fprintf (dump_file, ")\n");
957 /* Recursively determine and enqueue the exit conditions for a loop. */
960 get_exit_conditions_rec (struct loop *loop,
961 VEC(gimple,heap) **exit_conditions)
966 /* Recurse on the inner loops, then on the next (sibling) loops. */
967 get_exit_conditions_rec (loop->inner, exit_conditions);
968 get_exit_conditions_rec (loop->next, exit_conditions);
970 if (single_exit (loop))
972 gimple loop_condition = get_loop_exit_condition (loop);
975 VEC_safe_push (gimple, heap, *exit_conditions, loop_condition);
979 /* Select the candidate loop nests for the analysis. This function
980 initializes the EXIT_CONDITIONS array. */
983 select_loops_exit_conditions (VEC(gimple,heap) **exit_conditions)
985 struct loop *function_body = current_loops->tree_root;
987 get_exit_conditions_rec (function_body->inner, exit_conditions);
991 /* Depth first search algorithm. */
993 typedef enum t_bool {
1000 static t_bool follow_ssa_edge (struct loop *loop, gimple, gimple, tree *, int);
1002 /* Follow the ssa edge into the binary expression RHS0 CODE RHS1.
1003 Return true if the strongly connected component has been found. */
1006 follow_ssa_edge_binary (struct loop *loop, gimple at_stmt,
1007 tree type, tree rhs0, enum tree_code code, tree rhs1,
1008 gimple halting_phi, tree *evolution_of_loop, int limit)
1010 t_bool res = t_false;
1015 case POINTER_PLUS_EXPR:
1017 if (TREE_CODE (rhs0) == SSA_NAME)
1019 if (TREE_CODE (rhs1) == SSA_NAME)
1021 /* Match an assignment under the form:
1024 /* We want only assignments of form "name + name" contribute to
1025 LIMIT, as the other cases do not necessarily contribute to
1026 the complexity of the expression. */
1029 evol = *evolution_of_loop;
1030 res = follow_ssa_edge
1031 (loop, SSA_NAME_DEF_STMT (rhs0), halting_phi, &evol, limit);
1034 *evolution_of_loop = add_to_evolution
1036 chrec_convert (type, evol, at_stmt),
1037 code, rhs1, at_stmt);
1039 else if (res == t_false)
1041 res = follow_ssa_edge
1042 (loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
1043 evolution_of_loop, limit);
1046 *evolution_of_loop = add_to_evolution
1048 chrec_convert (type, *evolution_of_loop, at_stmt),
1049 code, rhs0, at_stmt);
1051 else if (res == t_dont_know)
1052 *evolution_of_loop = chrec_dont_know;
1055 else if (res == t_dont_know)
1056 *evolution_of_loop = chrec_dont_know;
1061 /* Match an assignment under the form:
1063 res = follow_ssa_edge
1064 (loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
1065 evolution_of_loop, limit);
1067 *evolution_of_loop = add_to_evolution
1068 (loop->num, chrec_convert (type, *evolution_of_loop,
1070 code, rhs1, at_stmt);
1072 else if (res == t_dont_know)
1073 *evolution_of_loop = chrec_dont_know;
1077 else if (TREE_CODE (rhs1) == SSA_NAME)
1079 /* Match an assignment under the form:
1081 res = follow_ssa_edge
1082 (loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
1083 evolution_of_loop, limit);
1085 *evolution_of_loop = add_to_evolution
1086 (loop->num, chrec_convert (type, *evolution_of_loop,
1088 code, rhs0, at_stmt);
1090 else if (res == t_dont_know)
1091 *evolution_of_loop = chrec_dont_know;
1095 /* Otherwise, match an assignment under the form:
1097 /* And there is nothing to do. */
1102 /* This case is under the form "opnd0 = rhs0 - rhs1". */
1103 if (TREE_CODE (rhs0) == SSA_NAME)
1105 /* Match an assignment under the form:
1108 /* We want only assignments of form "name - name" contribute to
1109 LIMIT, as the other cases do not necessarily contribute to
1110 the complexity of the expression. */
1111 if (TREE_CODE (rhs1) == SSA_NAME)
1114 res = follow_ssa_edge (loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
1115 evolution_of_loop, limit);
1117 *evolution_of_loop = add_to_evolution
1118 (loop->num, chrec_convert (type, *evolution_of_loop, at_stmt),
1119 MINUS_EXPR, rhs1, at_stmt);
1121 else if (res == t_dont_know)
1122 *evolution_of_loop = chrec_dont_know;
1125 /* Otherwise, match an assignment under the form:
1127 /* And there is nothing to do. */
1138 /* Follow the ssa edge into the expression EXPR.
1139 Return true if the strongly connected component has been found. */
1142 follow_ssa_edge_expr (struct loop *loop, gimple at_stmt, tree expr,
1143 gimple halting_phi, tree *evolution_of_loop, int limit)
1145 t_bool res = t_false;
1147 tree type = TREE_TYPE (expr);
1148 enum tree_code code;
1150 /* The EXPR is one of the following cases:
1154 - a POINTER_PLUS_EXPR,
1157 - other cases are not yet handled. */
1158 code = TREE_CODE (expr);
1162 /* This assignment is under the form "a_1 = (cast) rhs. */
1163 res = follow_ssa_edge_expr (loop, at_stmt, TREE_OPERAND (expr, 0),
1164 halting_phi, evolution_of_loop, limit);
1165 *evolution_of_loop = chrec_convert (type, *evolution_of_loop, at_stmt);
1169 /* This assignment is under the form "a_1 = 7". */
1174 /* This assignment is under the form: "a_1 = b_2". */
1175 res = follow_ssa_edge
1176 (loop, SSA_NAME_DEF_STMT (expr), halting_phi, evolution_of_loop, limit);
1179 case POINTER_PLUS_EXPR:
1182 /* This case is under the form "rhs0 +- rhs1". */
1183 rhs0 = TREE_OPERAND (expr, 0);
1184 rhs1 = TREE_OPERAND (expr, 1);
1185 STRIP_TYPE_NOPS (rhs0);
1186 STRIP_TYPE_NOPS (rhs1);
1187 return follow_ssa_edge_binary (loop, at_stmt, type, rhs0, code, rhs1,
1188 halting_phi, evolution_of_loop, limit);
1192 /* This assignment is of the form: "a_1 = ASSERT_EXPR <a_2, ...>"
1193 It must be handled as a copy assignment of the form a_1 = a_2. */
1194 tree op0 = ASSERT_EXPR_VAR (expr);
1195 if (TREE_CODE (op0) == SSA_NAME)
1196 res = follow_ssa_edge (loop, SSA_NAME_DEF_STMT (op0),
1197 halting_phi, evolution_of_loop, limit);
1212 /* Follow the ssa edge into the right hand side of an assignment STMT.
1213 Return true if the strongly connected component has been found. */
1216 follow_ssa_edge_in_rhs (struct loop *loop, gimple stmt,
1217 gimple halting_phi, tree *evolution_of_loop, int limit)
1219 tree type = TREE_TYPE (gimple_assign_lhs (stmt));
1220 enum tree_code code = gimple_assign_rhs_code (stmt);
1222 switch (get_gimple_rhs_class (code))
1224 case GIMPLE_BINARY_RHS:
1225 return follow_ssa_edge_binary (loop, stmt, type,
1226 gimple_assign_rhs1 (stmt), code,
1227 gimple_assign_rhs2 (stmt),
1228 halting_phi, evolution_of_loop, limit);
1229 case GIMPLE_SINGLE_RHS:
1230 return follow_ssa_edge_expr (loop, stmt, gimple_assign_rhs1 (stmt),
1231 halting_phi, evolution_of_loop, limit);
1232 case GIMPLE_UNARY_RHS:
1233 if (code == NOP_EXPR)
1235 /* This assignment is under the form "a_1 = (cast) rhs. */
1237 = follow_ssa_edge_expr (loop, stmt, gimple_assign_rhs1 (stmt),
1238 halting_phi, evolution_of_loop, limit);
1239 *evolution_of_loop = chrec_convert (type, *evolution_of_loop, stmt);
1249 /* Checks whether the I-th argument of a PHI comes from a backedge. */
1252 backedge_phi_arg_p (gimple phi, int i)
1254 const_edge e = gimple_phi_arg_edge (phi, i);
1256 /* We would in fact like to test EDGE_DFS_BACK here, but we do not care
1257 about updating it anywhere, and this should work as well most of the
1259 if (e->flags & EDGE_IRREDUCIBLE_LOOP)
1265 /* Helper function for one branch of the condition-phi-node. Return
1266 true if the strongly connected component has been found following
1269 static inline t_bool
1270 follow_ssa_edge_in_condition_phi_branch (int i,
1272 gimple condition_phi,
1274 tree *evolution_of_branch,
1275 tree init_cond, int limit)
1277 tree branch = PHI_ARG_DEF (condition_phi, i);
1278 *evolution_of_branch = chrec_dont_know;
1280 /* Do not follow back edges (they must belong to an irreducible loop, which
1281 we really do not want to worry about). */
1282 if (backedge_phi_arg_p (condition_phi, i))
1285 if (TREE_CODE (branch) == SSA_NAME)
1287 *evolution_of_branch = init_cond;
1288 return follow_ssa_edge (loop, SSA_NAME_DEF_STMT (branch), halting_phi,
1289 evolution_of_branch, limit);
1292 /* This case occurs when one of the condition branches sets
1293 the variable to a constant: i.e. a phi-node like
1294 "a_2 = PHI <a_7(5), 2(6)>;".
1296 FIXME: This case have to be refined correctly:
1297 in some cases it is possible to say something better than
1298 chrec_dont_know, for example using a wrap-around notation. */
1302 /* This function merges the branches of a condition-phi-node in a
1306 follow_ssa_edge_in_condition_phi (struct loop *loop,
1307 gimple condition_phi,
1309 tree *evolution_of_loop, int limit)
1312 tree init = *evolution_of_loop;
1313 tree evolution_of_branch;
1314 t_bool res = follow_ssa_edge_in_condition_phi_branch (0, loop, condition_phi,
1316 &evolution_of_branch,
1318 if (res == t_false || res == t_dont_know)
1321 *evolution_of_loop = evolution_of_branch;
1323 /* If the phi node is just a copy, do not increase the limit. */
1324 n = gimple_phi_num_args (condition_phi);
1328 for (i = 1; i < n; i++)
1330 /* Quickly give up when the evolution of one of the branches is
1332 if (*evolution_of_loop == chrec_dont_know)
1335 res = follow_ssa_edge_in_condition_phi_branch (i, loop, condition_phi,
1337 &evolution_of_branch,
1339 if (res == t_false || res == t_dont_know)
1342 *evolution_of_loop = chrec_merge (*evolution_of_loop,
1343 evolution_of_branch);
1349 /* Follow an SSA edge in an inner loop. It computes the overall
1350 effect of the loop, and following the symbolic initial conditions,
1351 it follows the edges in the parent loop. The inner loop is
1352 considered as a single statement. */
1355 follow_ssa_edge_inner_loop_phi (struct loop *outer_loop,
1356 gimple loop_phi_node,
1358 tree *evolution_of_loop, int limit)
1360 struct loop *loop = loop_containing_stmt (loop_phi_node);
1361 tree ev = analyze_scalar_evolution (loop, PHI_RESULT (loop_phi_node));
1363 /* Sometimes, the inner loop is too difficult to analyze, and the
1364 result of the analysis is a symbolic parameter. */
1365 if (ev == PHI_RESULT (loop_phi_node))
1367 t_bool res = t_false;
1368 int i, n = gimple_phi_num_args (loop_phi_node);
1370 for (i = 0; i < n; i++)
1372 tree arg = PHI_ARG_DEF (loop_phi_node, i);
1375 /* Follow the edges that exit the inner loop. */
1376 bb = gimple_phi_arg_edge (loop_phi_node, i)->src;
1377 if (!flow_bb_inside_loop_p (loop, bb))
1378 res = follow_ssa_edge_expr (outer_loop, loop_phi_node,
1380 evolution_of_loop, limit);
1385 /* If the path crosses this loop-phi, give up. */
1387 *evolution_of_loop = chrec_dont_know;
1392 /* Otherwise, compute the overall effect of the inner loop. */
1393 ev = compute_overall_effect_of_inner_loop (loop, ev);
1394 return follow_ssa_edge_expr (outer_loop, loop_phi_node, ev, halting_phi,
1395 evolution_of_loop, limit);
1398 /* Follow an SSA edge from a loop-phi-node to itself, constructing a
1399 path that is analyzed on the return walk. */
1402 follow_ssa_edge (struct loop *loop, gimple def, gimple halting_phi,
1403 tree *evolution_of_loop, int limit)
1405 struct loop *def_loop;
1407 if (gimple_nop_p (def))
1410 /* Give up if the path is longer than the MAX that we allow. */
1411 if (limit > PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
1414 def_loop = loop_containing_stmt (def);
1416 switch (gimple_code (def))
1419 if (!loop_phi_node_p (def))
1420 /* DEF is a condition-phi-node. Follow the branches, and
1421 record their evolutions. Finally, merge the collected
1422 information and set the approximation to the main
1424 return follow_ssa_edge_in_condition_phi
1425 (loop, def, halting_phi, evolution_of_loop, limit);
1427 /* When the analyzed phi is the halting_phi, the
1428 depth-first search is over: we have found a path from
1429 the halting_phi to itself in the loop. */
1430 if (def == halting_phi)
1433 /* Otherwise, the evolution of the HALTING_PHI depends
1434 on the evolution of another loop-phi-node, i.e. the
1435 evolution function is a higher degree polynomial. */
1436 if (def_loop == loop)
1440 if (flow_loop_nested_p (loop, def_loop))
1441 return follow_ssa_edge_inner_loop_phi
1442 (loop, def, halting_phi, evolution_of_loop, limit + 1);
1448 return follow_ssa_edge_in_rhs (loop, def, halting_phi,
1449 evolution_of_loop, limit);
1452 /* At this level of abstraction, the program is just a set
1453 of GIMPLE_ASSIGNs and PHI_NODEs. In principle there is no
1454 other node to be handled. */
1461 /* Given a LOOP_PHI_NODE, this function determines the evolution
1462 function from LOOP_PHI_NODE to LOOP_PHI_NODE in the loop. */
1465 analyze_evolution_in_loop (gimple loop_phi_node,
1468 int i, n = gimple_phi_num_args (loop_phi_node);
1469 tree evolution_function = chrec_not_analyzed_yet;
1470 struct loop *loop = loop_containing_stmt (loop_phi_node);
1473 if (dump_file && (dump_flags & TDF_DETAILS))
1475 fprintf (dump_file, "(analyze_evolution_in_loop \n");
1476 fprintf (dump_file, " (loop_phi_node = ");
1477 print_gimple_stmt (dump_file, loop_phi_node, 0, 0);
1478 fprintf (dump_file, ")\n");
1481 for (i = 0; i < n; i++)
1483 tree arg = PHI_ARG_DEF (loop_phi_node, i);
1488 /* Select the edges that enter the loop body. */
1489 bb = gimple_phi_arg_edge (loop_phi_node, i)->src;
1490 if (!flow_bb_inside_loop_p (loop, bb))
1493 if (TREE_CODE (arg) == SSA_NAME)
1495 ssa_chain = SSA_NAME_DEF_STMT (arg);
1497 /* Pass in the initial condition to the follow edge function. */
1499 res = follow_ssa_edge (loop, ssa_chain, loop_phi_node, &ev_fn, 0);
1504 /* When it is impossible to go back on the same
1505 loop_phi_node by following the ssa edges, the
1506 evolution is represented by a peeled chrec, i.e. the
1507 first iteration, EV_FN has the value INIT_COND, then
1508 all the other iterations it has the value of ARG.
1509 For the moment, PEELED_CHREC nodes are not built. */
1511 ev_fn = chrec_dont_know;
1513 /* When there are multiple back edges of the loop (which in fact never
1514 happens currently, but nevertheless), merge their evolutions. */
1515 evolution_function = chrec_merge (evolution_function, ev_fn);
1518 if (dump_file && (dump_flags & TDF_DETAILS))
1520 fprintf (dump_file, " (evolution_function = ");
1521 print_generic_expr (dump_file, evolution_function, 0);
1522 fprintf (dump_file, "))\n");
1525 return evolution_function;
1528 /* Given a loop-phi-node, return the initial conditions of the
1529 variable on entry of the loop. When the CCP has propagated
1530 constants into the loop-phi-node, the initial condition is
1531 instantiated, otherwise the initial condition is kept symbolic.
1532 This analyzer does not analyze the evolution outside the current
1533 loop, and leaves this task to the on-demand tree reconstructor. */
1536 analyze_initial_condition (gimple loop_phi_node)
1539 tree init_cond = chrec_not_analyzed_yet;
1540 struct loop *loop = loop_containing_stmt (loop_phi_node);
1542 if (dump_file && (dump_flags & TDF_DETAILS))
1544 fprintf (dump_file, "(analyze_initial_condition \n");
1545 fprintf (dump_file, " (loop_phi_node = \n");
1546 print_gimple_stmt (dump_file, loop_phi_node, 0, 0);
1547 fprintf (dump_file, ")\n");
1550 n = gimple_phi_num_args (loop_phi_node);
1551 for (i = 0; i < n; i++)
1553 tree branch = PHI_ARG_DEF (loop_phi_node, i);
1554 basic_block bb = gimple_phi_arg_edge (loop_phi_node, i)->src;
1556 /* When the branch is oriented to the loop's body, it does
1557 not contribute to the initial condition. */
1558 if (flow_bb_inside_loop_p (loop, bb))
1561 if (init_cond == chrec_not_analyzed_yet)
1567 if (TREE_CODE (branch) == SSA_NAME)
1569 init_cond = chrec_dont_know;
1573 init_cond = chrec_merge (init_cond, branch);
1576 /* Ooops -- a loop without an entry??? */
1577 if (init_cond == chrec_not_analyzed_yet)
1578 init_cond = chrec_dont_know;
1580 if (dump_file && (dump_flags & TDF_DETAILS))
1582 fprintf (dump_file, " (init_cond = ");
1583 print_generic_expr (dump_file, init_cond, 0);
1584 fprintf (dump_file, "))\n");
1590 /* Analyze the scalar evolution for LOOP_PHI_NODE. */
1593 interpret_loop_phi (struct loop *loop, gimple loop_phi_node)
1596 struct loop *phi_loop = loop_containing_stmt (loop_phi_node);
1599 if (phi_loop != loop)
1601 struct loop *subloop;
1602 tree evolution_fn = analyze_scalar_evolution
1603 (phi_loop, PHI_RESULT (loop_phi_node));
1605 /* Dive one level deeper. */
1606 subloop = superloop_at_depth (phi_loop, loop_depth (loop) + 1);
1608 /* Interpret the subloop. */
1609 res = compute_overall_effect_of_inner_loop (subloop, evolution_fn);
1613 /* Otherwise really interpret the loop phi. */
1614 init_cond = analyze_initial_condition (loop_phi_node);
1615 res = analyze_evolution_in_loop (loop_phi_node, init_cond);
1620 /* This function merges the branches of a condition-phi-node,
1621 contained in the outermost loop, and whose arguments are already
1625 interpret_condition_phi (struct loop *loop, gimple condition_phi)
1627 int i, n = gimple_phi_num_args (condition_phi);
1628 tree res = chrec_not_analyzed_yet;
1630 for (i = 0; i < n; i++)
1634 if (backedge_phi_arg_p (condition_phi, i))
1636 res = chrec_dont_know;
1640 branch_chrec = analyze_scalar_evolution
1641 (loop, PHI_ARG_DEF (condition_phi, i));
1643 res = chrec_merge (res, branch_chrec);
1649 /* Interpret the operation RHS1 OP RHS2. If we didn't
1650 analyze this node before, follow the definitions until ending
1651 either on an analyzed GIMPLE_ASSIGN, or on a loop-phi-node. On the
1652 return path, this function propagates evolutions (ala constant copy
1653 propagation). OPND1 is not a GIMPLE expression because we could
1654 analyze the effect of an inner loop: see interpret_loop_phi. */
1657 interpret_rhs_expr (struct loop *loop, gimple at_stmt,
1658 tree type, tree rhs1, enum tree_code code, tree rhs2)
1660 tree res, chrec1, chrec2;
1662 if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
1664 if (is_gimple_min_invariant (rhs1))
1665 return chrec_convert (type, rhs1, at_stmt);
1667 if (code == SSA_NAME)
1668 return chrec_convert (type, analyze_scalar_evolution (loop, rhs1),
1671 if (code == ASSERT_EXPR)
1673 rhs1 = ASSERT_EXPR_VAR (rhs1);
1674 return chrec_convert (type, analyze_scalar_evolution (loop, rhs1),
1678 return chrec_dont_know;
1683 case POINTER_PLUS_EXPR:
1684 chrec1 = analyze_scalar_evolution (loop, rhs1);
1685 chrec2 = analyze_scalar_evolution (loop, rhs2);
1686 chrec1 = chrec_convert (type, chrec1, at_stmt);
1687 chrec2 = chrec_convert (sizetype, chrec2, at_stmt);
1688 res = chrec_fold_plus (type, chrec1, chrec2);
1692 chrec1 = analyze_scalar_evolution (loop, rhs1);
1693 chrec2 = analyze_scalar_evolution (loop, rhs2);
1694 chrec1 = chrec_convert (type, chrec1, at_stmt);
1695 chrec2 = chrec_convert (type, chrec2, at_stmt);
1696 res = chrec_fold_plus (type, chrec1, chrec2);
1700 chrec1 = analyze_scalar_evolution (loop, rhs1);
1701 chrec2 = analyze_scalar_evolution (loop, rhs2);
1702 chrec1 = chrec_convert (type, chrec1, at_stmt);
1703 chrec2 = chrec_convert (type, chrec2, at_stmt);
1704 res = chrec_fold_minus (type, chrec1, chrec2);
1708 chrec1 = analyze_scalar_evolution (loop, rhs1);
1709 chrec1 = chrec_convert (type, chrec1, at_stmt);
1710 /* TYPE may be integer, real or complex, so use fold_convert. */
1711 res = chrec_fold_multiply (type, chrec1,
1712 fold_convert (type, integer_minus_one_node));
1716 chrec1 = analyze_scalar_evolution (loop, rhs1);
1717 chrec2 = analyze_scalar_evolution (loop, rhs2);
1718 chrec1 = chrec_convert (type, chrec1, at_stmt);
1719 chrec2 = chrec_convert (type, chrec2, at_stmt);
1720 res = chrec_fold_multiply (type, chrec1, chrec2);
1724 chrec1 = analyze_scalar_evolution (loop, rhs1);
1725 res = chrec_convert (type, chrec1, at_stmt);
1729 res = chrec_dont_know;
1736 /* Interpret the expression EXPR. */
1739 interpret_expr (struct loop *loop, gimple at_stmt, tree expr)
1741 enum tree_code code;
1742 tree type = TREE_TYPE (expr), op0, op1;
1744 if (automatically_generated_chrec_p (expr))
1747 if (TREE_CODE (expr) == POLYNOMIAL_CHREC)
1748 return chrec_dont_know;
1750 extract_ops_from_tree (expr, &code, &op0, &op1);
1752 return interpret_rhs_expr (loop, at_stmt, type,
1756 /* Interpret the rhs of the assignment STMT. */
1759 interpret_gimple_assign (struct loop *loop, gimple stmt)
1761 tree type = TREE_TYPE (gimple_assign_lhs (stmt));
1762 enum tree_code code = gimple_assign_rhs_code (stmt);
1764 return interpret_rhs_expr (loop, stmt, type,
1765 gimple_assign_rhs1 (stmt), code,
1766 gimple_assign_rhs2 (stmt));
1771 /* This section contains all the entry points:
1772 - number_of_iterations_in_loop,
1773 - analyze_scalar_evolution,
1774 - instantiate_parameters.
1777 /* Compute and return the evolution function in WRTO_LOOP, the nearest
1778 common ancestor of DEF_LOOP and USE_LOOP. */
1781 compute_scalar_evolution_in_loop (struct loop *wrto_loop,
1782 struct loop *def_loop,
1786 if (def_loop == wrto_loop)
1789 def_loop = superloop_at_depth (def_loop, loop_depth (wrto_loop) + 1);
1790 res = compute_overall_effect_of_inner_loop (def_loop, ev);
1792 return analyze_scalar_evolution_1 (wrto_loop, res, chrec_not_analyzed_yet);
1795 /* Helper recursive function. */
1798 analyze_scalar_evolution_1 (struct loop *loop, tree var, tree res)
1800 tree type = TREE_TYPE (var);
1803 struct loop *def_loop;
1805 if (loop == NULL || TREE_CODE (type) == VECTOR_TYPE)
1806 return chrec_dont_know;
1808 if (TREE_CODE (var) != SSA_NAME)
1809 return interpret_expr (loop, NULL, var);
1811 def = SSA_NAME_DEF_STMT (var);
1812 bb = gimple_bb (def);
1813 def_loop = bb ? bb->loop_father : NULL;
1816 || !flow_bb_inside_loop_p (loop, bb))
1818 /* Keep the symbolic form. */
1823 if (res != chrec_not_analyzed_yet)
1825 if (loop != bb->loop_father)
1826 res = compute_scalar_evolution_in_loop
1827 (find_common_loop (loop, bb->loop_father), bb->loop_father, res);
1832 if (loop != def_loop)
1834 res = analyze_scalar_evolution_1 (def_loop, var, chrec_not_analyzed_yet);
1835 res = compute_scalar_evolution_in_loop (loop, def_loop, res);
1840 switch (gimple_code (def))
1843 res = interpret_gimple_assign (loop, def);
1847 if (loop_phi_node_p (def))
1848 res = interpret_loop_phi (loop, def);
1850 res = interpret_condition_phi (loop, def);
1854 res = chrec_dont_know;
1860 /* Keep the symbolic form. */
1861 if (res == chrec_dont_know)
1864 if (loop == def_loop)
1865 set_scalar_evolution (block_before_loop (loop), var, res);
1870 /* Entry point for the scalar evolution analyzer.
1871 Analyzes and returns the scalar evolution of the ssa_name VAR.
1872 LOOP_NB is the identifier number of the loop in which the variable
1875 Example of use: having a pointer VAR to a SSA_NAME node, STMT a
1876 pointer to the statement that uses this variable, in order to
1877 determine the evolution function of the variable, use the following
1880 unsigned loop_nb = loop_containing_stmt (stmt)->num;
1881 tree chrec_with_symbols = analyze_scalar_evolution (loop_nb, var);
1882 tree chrec_instantiated = instantiate_parameters (loop, chrec_with_symbols);
1886 analyze_scalar_evolution (struct loop *loop, tree var)
1890 if (dump_file && (dump_flags & TDF_DETAILS))
1892 fprintf (dump_file, "(analyze_scalar_evolution \n");
1893 fprintf (dump_file, " (loop_nb = %d)\n", loop->num);
1894 fprintf (dump_file, " (scalar = ");
1895 print_generic_expr (dump_file, var, 0);
1896 fprintf (dump_file, ")\n");
1899 res = get_scalar_evolution (block_before_loop (loop), var);
1900 res = analyze_scalar_evolution_1 (loop, var, res);
1902 if (dump_file && (dump_flags & TDF_DETAILS))
1903 fprintf (dump_file, ")\n");
1908 /* Analyze scalar evolution of use of VERSION in USE_LOOP with respect to
1909 WRTO_LOOP (which should be a superloop of both USE_LOOP and definition
1912 FOLDED_CASTS is set to true if resolve_mixers used
1913 chrec_convert_aggressive (TODO -- not really, we are way too conservative
1914 at the moment in order to keep things simple). */
1917 analyze_scalar_evolution_in_loop (struct loop *wrto_loop, struct loop *use_loop,
1918 tree version, bool *folded_casts)
1921 tree ev = version, tmp;
1924 *folded_casts = false;
1927 tmp = analyze_scalar_evolution (use_loop, ev);
1928 ev = resolve_mixers (use_loop, tmp);
1930 if (folded_casts && tmp != ev)
1931 *folded_casts = true;
1933 if (use_loop == wrto_loop)
1936 /* If the value of the use changes in the inner loop, we cannot express
1937 its value in the outer loop (we might try to return interval chrec,
1938 but we do not have a user for it anyway) */
1939 if (!no_evolution_in_loop_p (ev, use_loop->num, &val)
1941 return chrec_dont_know;
1943 use_loop = loop_outer (use_loop);
1947 /* Returns from CACHE the value for VERSION instantiated below
1948 INSTANTIATED_BELOW block. */
1951 get_instantiated_value (htab_t cache, basic_block instantiated_below,
1954 struct scev_info_str *info, pattern;
1956 pattern.var = version;
1957 pattern.instantiated_below = instantiated_below;
1958 info = (struct scev_info_str *) htab_find (cache, &pattern);
1966 /* Sets in CACHE the value of VERSION instantiated below basic block
1967 INSTANTIATED_BELOW to VAL. */
1970 set_instantiated_value (htab_t cache, basic_block instantiated_below,
1971 tree version, tree val)
1973 struct scev_info_str *info, pattern;
1976 pattern.var = version;
1977 pattern.instantiated_below = instantiated_below;
1978 slot = htab_find_slot (cache, &pattern, INSERT);
1981 *slot = new_scev_info_str (instantiated_below, version);
1982 info = (struct scev_info_str *) *slot;
1986 /* Return the closed_loop_phi node for VAR. If there is none, return
1990 loop_closed_phi_def (tree var)
1995 gimple_stmt_iterator psi;
1997 if (var == NULL_TREE
1998 || TREE_CODE (var) != SSA_NAME)
2001 loop = loop_containing_stmt (SSA_NAME_DEF_STMT (var));
2002 exit = single_exit (loop);
2006 for (psi = gsi_start_phis (exit->dest); !gsi_end_p (psi); gsi_next (&psi))
2008 phi = gsi_stmt (psi);
2009 if (PHI_ARG_DEF_FROM_EDGE (phi, exit) == var)
2010 return PHI_RESULT (phi);
2016 /* Analyze all the parameters of the chrec, between INSTANTIATE_BELOW
2017 and EVOLUTION_LOOP, that were left under a symbolic form.
2019 CHREC is the scalar evolution to instantiate.
2021 CACHE is the cache of already instantiated values.
2023 FOLD_CONVERSIONS should be set to true when the conversions that
2024 may wrap in signed/pointer type are folded, as long as the value of
2025 the chrec is preserved.
2027 SIZE_EXPR is used for computing the size of the expression to be
2028 instantiated, and to stop if it exceeds some limit. */
2031 instantiate_scev_1 (basic_block instantiate_below,
2032 struct loop *evolution_loop, tree chrec,
2033 bool fold_conversions, htab_t cache, int size_expr)
2035 tree res, op0, op1, op2;
2037 struct loop *def_loop;
2038 tree type = chrec_type (chrec);
2040 /* Give up if the expression is larger than the MAX that we allow. */
2041 if (size_expr++ > PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
2042 return chrec_dont_know;
2044 if (automatically_generated_chrec_p (chrec)
2045 || is_gimple_min_invariant (chrec))
2048 switch (TREE_CODE (chrec))
2051 def_bb = gimple_bb (SSA_NAME_DEF_STMT (chrec));
2053 /* A parameter (or loop invariant and we do not want to include
2054 evolutions in outer loops), nothing to do. */
2056 || loop_depth (def_bb->loop_father) == 0
2057 || dominated_by_p (CDI_DOMINATORS, instantiate_below, def_bb))
2060 /* We cache the value of instantiated variable to avoid exponential
2061 time complexity due to reevaluations. We also store the convenient
2062 value in the cache in order to prevent infinite recursion -- we do
2063 not want to instantiate the SSA_NAME if it is in a mixer
2064 structure. This is used for avoiding the instantiation of
2065 recursively defined functions, such as:
2067 | a_2 -> {0, +, 1, +, a_2}_1 */
2069 res = get_instantiated_value (cache, instantiate_below, chrec);
2073 res = chrec_dont_know;
2074 set_instantiated_value (cache, instantiate_below, chrec, res);
2076 def_loop = find_common_loop (evolution_loop, def_bb->loop_father);
2078 /* If the analysis yields a parametric chrec, instantiate the
2080 res = analyze_scalar_evolution (def_loop, chrec);
2082 /* Don't instantiate loop-closed-ssa phi nodes. */
2083 if (TREE_CODE (res) == SSA_NAME
2084 && (loop_containing_stmt (SSA_NAME_DEF_STMT (res)) == NULL
2085 || (loop_depth (loop_containing_stmt (SSA_NAME_DEF_STMT (res)))
2086 > loop_depth (def_loop))))
2089 res = loop_closed_phi_def (chrec);
2093 if (res == NULL_TREE)
2094 res = chrec_dont_know;
2097 else if (res != chrec_dont_know)
2098 res = instantiate_scev_1 (instantiate_below, evolution_loop, res,
2099 fold_conversions, cache, size_expr);
2101 /* Store the correct value to the cache. */
2102 set_instantiated_value (cache, instantiate_below, chrec, res);
2105 case POLYNOMIAL_CHREC:
2106 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2107 CHREC_LEFT (chrec), fold_conversions, cache,
2109 if (op0 == chrec_dont_know)
2110 return chrec_dont_know;
2112 op1 = instantiate_scev_1 (instantiate_below, evolution_loop,
2113 CHREC_RIGHT (chrec), fold_conversions, cache,
2115 if (op1 == chrec_dont_know)
2116 return chrec_dont_know;
2118 if (CHREC_LEFT (chrec) != op0
2119 || CHREC_RIGHT (chrec) != op1)
2121 op1 = chrec_convert_rhs (chrec_type (op0), op1, NULL);
2122 chrec = build_polynomial_chrec (CHREC_VARIABLE (chrec), op0, op1);
2126 case POINTER_PLUS_EXPR:
2128 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2129 TREE_OPERAND (chrec, 0), fold_conversions, cache,
2131 if (op0 == chrec_dont_know)
2132 return chrec_dont_know;
2134 op1 = instantiate_scev_1 (instantiate_below, evolution_loop,
2135 TREE_OPERAND (chrec, 1), fold_conversions, cache,
2137 if (op1 == chrec_dont_know)
2138 return chrec_dont_know;
2140 if (TREE_OPERAND (chrec, 0) != op0
2141 || TREE_OPERAND (chrec, 1) != op1)
2143 op0 = chrec_convert (type, op0, NULL);
2144 op1 = chrec_convert_rhs (type, op1, NULL);
2145 chrec = chrec_fold_plus (type, op0, op1);
2150 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2151 TREE_OPERAND (chrec, 0), fold_conversions, cache,
2153 if (op0 == chrec_dont_know)
2154 return chrec_dont_know;
2156 op1 = instantiate_scev_1 (instantiate_below, evolution_loop,
2157 TREE_OPERAND (chrec, 1),
2158 fold_conversions, cache, size_expr);
2159 if (op1 == chrec_dont_know)
2160 return chrec_dont_know;
2162 if (TREE_OPERAND (chrec, 0) != op0
2163 || TREE_OPERAND (chrec, 1) != op1)
2165 op0 = chrec_convert (type, op0, NULL);
2166 op1 = chrec_convert (type, op1, NULL);
2167 chrec = chrec_fold_minus (type, op0, op1);
2172 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2173 TREE_OPERAND (chrec, 0),
2174 fold_conversions, cache, size_expr);
2175 if (op0 == chrec_dont_know)
2176 return chrec_dont_know;
2178 op1 = instantiate_scev_1 (instantiate_below, evolution_loop,
2179 TREE_OPERAND (chrec, 1),
2180 fold_conversions, cache, size_expr);
2181 if (op1 == chrec_dont_know)
2182 return chrec_dont_know;
2184 if (TREE_OPERAND (chrec, 0) != op0
2185 || TREE_OPERAND (chrec, 1) != op1)
2187 op0 = chrec_convert (type, op0, NULL);
2188 op1 = chrec_convert (type, op1, NULL);
2189 chrec = chrec_fold_multiply (type, op0, op1);
2194 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2195 TREE_OPERAND (chrec, 0),
2196 fold_conversions, cache, size_expr);
2197 if (op0 == chrec_dont_know)
2198 return chrec_dont_know;
2200 if (fold_conversions)
2202 tree tmp = chrec_convert_aggressive (TREE_TYPE (chrec), op0);
2207 if (op0 == TREE_OPERAND (chrec, 0))
2210 /* If we used chrec_convert_aggressive, we can no longer assume that
2211 signed chrecs do not overflow, as chrec_convert does, so avoid
2212 calling it in that case. */
2213 if (fold_conversions)
2214 return fold_convert (TREE_TYPE (chrec), op0);
2216 return chrec_convert (TREE_TYPE (chrec), op0, NULL);
2218 case SCEV_NOT_KNOWN:
2219 return chrec_dont_know;
2228 if (VL_EXP_CLASS_P (chrec))
2229 return chrec_dont_know;
2231 switch (TREE_CODE_LENGTH (TREE_CODE (chrec)))
2234 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2235 TREE_OPERAND (chrec, 0),
2236 fold_conversions, cache, size_expr);
2237 if (op0 == chrec_dont_know)
2238 return chrec_dont_know;
2240 op1 = instantiate_scev_1 (instantiate_below, evolution_loop,
2241 TREE_OPERAND (chrec, 1),
2242 fold_conversions, cache, size_expr);
2243 if (op1 == chrec_dont_know)
2244 return chrec_dont_know;
2246 op2 = instantiate_scev_1 (instantiate_below, evolution_loop,
2247 TREE_OPERAND (chrec, 2),
2248 fold_conversions, cache, size_expr);
2249 if (op2 == chrec_dont_know)
2250 return chrec_dont_know;
2252 if (op0 == TREE_OPERAND (chrec, 0)
2253 && op1 == TREE_OPERAND (chrec, 1)
2254 && op2 == TREE_OPERAND (chrec, 2))
2257 return fold_build3 (TREE_CODE (chrec),
2258 TREE_TYPE (chrec), op0, op1, op2);
2261 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2262 TREE_OPERAND (chrec, 0),
2263 fold_conversions, cache, size_expr);
2264 if (op0 == chrec_dont_know)
2265 return chrec_dont_know;
2267 op1 = instantiate_scev_1 (instantiate_below, evolution_loop,
2268 TREE_OPERAND (chrec, 1),
2269 fold_conversions, cache, size_expr);
2270 if (op1 == chrec_dont_know)
2271 return chrec_dont_know;
2273 if (op0 == TREE_OPERAND (chrec, 0)
2274 && op1 == TREE_OPERAND (chrec, 1))
2276 return fold_build2 (TREE_CODE (chrec), TREE_TYPE (chrec), op0, op1);
2279 op0 = instantiate_scev_1 (instantiate_below, evolution_loop,
2280 TREE_OPERAND (chrec, 0),
2281 fold_conversions, cache, size_expr);
2282 if (op0 == chrec_dont_know)
2283 return chrec_dont_know;
2284 if (op0 == TREE_OPERAND (chrec, 0))
2286 return fold_build1 (TREE_CODE (chrec), TREE_TYPE (chrec), op0);
2295 /* Too complicated to handle. */
2296 return chrec_dont_know;
2299 /* Analyze all the parameters of the chrec that were left under a
2300 symbolic form. INSTANTIATE_BELOW is the basic block that stops the
2301 recursive instantiation of parameters: a parameter is a variable
2302 that is defined in a basic block that dominates INSTANTIATE_BELOW or
2303 a function parameter. */
2306 instantiate_scev (basic_block instantiate_below, struct loop *evolution_loop,
2310 htab_t cache = htab_create (10, hash_scev_info, eq_scev_info, del_scev_info);
2312 if (dump_file && (dump_flags & TDF_DETAILS))
2314 fprintf (dump_file, "(instantiate_scev \n");
2315 fprintf (dump_file, " (instantiate_below = %d)\n", instantiate_below->index);
2316 fprintf (dump_file, " (evolution_loop = %d)\n", evolution_loop->num);
2317 fprintf (dump_file, " (chrec = ");
2318 print_generic_expr (dump_file, chrec, 0);
2319 fprintf (dump_file, ")\n");
2322 res = instantiate_scev_1 (instantiate_below, evolution_loop, chrec, false,
2325 if (dump_file && (dump_flags & TDF_DETAILS))
2327 fprintf (dump_file, " (res = ");
2328 print_generic_expr (dump_file, res, 0);
2329 fprintf (dump_file, "))\n");
2332 htab_delete (cache);
2337 /* Similar to instantiate_parameters, but does not introduce the
2338 evolutions in outer loops for LOOP invariants in CHREC, and does not
2339 care about causing overflows, as long as they do not affect value
2340 of an expression. */
2343 resolve_mixers (struct loop *loop, tree chrec)
2345 htab_t cache = htab_create (10, hash_scev_info, eq_scev_info, del_scev_info);
2346 tree ret = instantiate_scev_1 (block_before_loop (loop), loop, chrec, true,
2348 htab_delete (cache);
2352 /* Entry point for the analysis of the number of iterations pass.
2353 This function tries to safely approximate the number of iterations
2354 the loop will run. When this property is not decidable at compile
2355 time, the result is chrec_dont_know. Otherwise the result is
2356 a scalar or a symbolic parameter.
2358 Example of analysis: suppose that the loop has an exit condition:
2360 "if (b > 49) goto end_loop;"
2362 and that in a previous analysis we have determined that the
2363 variable 'b' has an evolution function:
2365 "EF = {23, +, 5}_2".
2367 When we evaluate the function at the point 5, i.e. the value of the
2368 variable 'b' after 5 iterations in the loop, we have EF (5) = 48,
2369 and EF (6) = 53. In this case the value of 'b' on exit is '53' and
2370 the loop body has been executed 6 times. */
2373 number_of_latch_executions (struct loop *loop)
2377 struct tree_niter_desc niter_desc;
2379 /* Determine whether the number_of_iterations_in_loop has already
2381 res = loop->nb_iterations;
2384 res = chrec_dont_know;
2386 if (dump_file && (dump_flags & TDF_DETAILS))
2387 fprintf (dump_file, "(number_of_iterations_in_loop\n");
2389 exit = single_exit (loop);
2393 if (!number_of_iterations_exit (loop, exit, &niter_desc, false))
2396 type = TREE_TYPE (niter_desc.niter);
2397 if (integer_nonzerop (niter_desc.may_be_zero))
2398 res = build_int_cst (type, 0);
2399 else if (integer_zerop (niter_desc.may_be_zero))
2400 res = niter_desc.niter;
2402 res = chrec_dont_know;
2405 return set_nb_iterations_in_loop (loop, res);
2408 /* Returns the number of executions of the exit condition of LOOP,
2409 i.e., the number by one higher than number_of_latch_executions.
2410 Note that unlike number_of_latch_executions, this number does
2411 not necessarily fit in the unsigned variant of the type of
2412 the control variable -- if the number of iterations is a constant,
2413 we return chrec_dont_know if adding one to number_of_latch_executions
2414 overflows; however, in case the number of iterations is symbolic
2415 expression, the caller is responsible for dealing with this
2416 the possible overflow. */
2419 number_of_exit_cond_executions (struct loop *loop)
2421 tree ret = number_of_latch_executions (loop);
2422 tree type = chrec_type (ret);
2424 if (chrec_contains_undetermined (ret))
2427 ret = chrec_fold_plus (type, ret, build_int_cst (type, 1));
2428 if (TREE_CODE (ret) == INTEGER_CST
2429 && TREE_OVERFLOW (ret))
2430 return chrec_dont_know;
2435 /* One of the drivers for testing the scalar evolutions analysis.
2436 This function computes the number of iterations for all the loops
2437 from the EXIT_CONDITIONS array. */
2440 number_of_iterations_for_all_loops (VEC(gimple,heap) **exit_conditions)
2443 unsigned nb_chrec_dont_know_loops = 0;
2444 unsigned nb_static_loops = 0;
2447 for (i = 0; VEC_iterate (gimple, *exit_conditions, i, cond); i++)
2449 tree res = number_of_latch_executions (loop_containing_stmt (cond));
2450 if (chrec_contains_undetermined (res))
2451 nb_chrec_dont_know_loops++;
2458 fprintf (dump_file, "\n(\n");
2459 fprintf (dump_file, "-----------------------------------------\n");
2460 fprintf (dump_file, "%d\tnb_chrec_dont_know_loops\n", nb_chrec_dont_know_loops);
2461 fprintf (dump_file, "%d\tnb_static_loops\n", nb_static_loops);
2462 fprintf (dump_file, "%d\tnb_total_loops\n", number_of_loops ());
2463 fprintf (dump_file, "-----------------------------------------\n");
2464 fprintf (dump_file, ")\n\n");
2466 print_loops (dump_file, 3);
2472 /* Counters for the stats. */
2478 unsigned nb_affine_multivar;
2479 unsigned nb_higher_poly;
2480 unsigned nb_chrec_dont_know;
2481 unsigned nb_undetermined;
2484 /* Reset the counters. */
2487 reset_chrecs_counters (struct chrec_stats *stats)
2489 stats->nb_chrecs = 0;
2490 stats->nb_affine = 0;
2491 stats->nb_affine_multivar = 0;
2492 stats->nb_higher_poly = 0;
2493 stats->nb_chrec_dont_know = 0;
2494 stats->nb_undetermined = 0;
2497 /* Dump the contents of a CHREC_STATS structure. */
2500 dump_chrecs_stats (FILE *file, struct chrec_stats *stats)
2502 fprintf (file, "\n(\n");
2503 fprintf (file, "-----------------------------------------\n");
2504 fprintf (file, "%d\taffine univariate chrecs\n", stats->nb_affine);
2505 fprintf (file, "%d\taffine multivariate chrecs\n", stats->nb_affine_multivar);
2506 fprintf (file, "%d\tdegree greater than 2 polynomials\n",
2507 stats->nb_higher_poly);
2508 fprintf (file, "%d\tchrec_dont_know chrecs\n", stats->nb_chrec_dont_know);
2509 fprintf (file, "-----------------------------------------\n");
2510 fprintf (file, "%d\ttotal chrecs\n", stats->nb_chrecs);
2511 fprintf (file, "%d\twith undetermined coefficients\n",
2512 stats->nb_undetermined);
2513 fprintf (file, "-----------------------------------------\n");
2514 fprintf (file, "%d\tchrecs in the scev database\n",
2515 (int) htab_elements (scalar_evolution_info));
2516 fprintf (file, "%d\tsets in the scev database\n", nb_set_scev);
2517 fprintf (file, "%d\tgets in the scev database\n", nb_get_scev);
2518 fprintf (file, "-----------------------------------------\n");
2519 fprintf (file, ")\n\n");
2522 /* Gather statistics about CHREC. */
2525 gather_chrec_stats (tree chrec, struct chrec_stats *stats)
2527 if (dump_file && (dump_flags & TDF_STATS))
2529 fprintf (dump_file, "(classify_chrec ");
2530 print_generic_expr (dump_file, chrec, 0);
2531 fprintf (dump_file, "\n");
2536 if (chrec == NULL_TREE)
2538 stats->nb_undetermined++;
2542 switch (TREE_CODE (chrec))
2544 case POLYNOMIAL_CHREC:
2545 if (evolution_function_is_affine_p (chrec))
2547 if (dump_file && (dump_flags & TDF_STATS))
2548 fprintf (dump_file, " affine_univariate\n");
2551 else if (evolution_function_is_affine_multivariate_p (chrec, 0))
2553 if (dump_file && (dump_flags & TDF_STATS))
2554 fprintf (dump_file, " affine_multivariate\n");
2555 stats->nb_affine_multivar++;
2559 if (dump_file && (dump_flags & TDF_STATS))
2560 fprintf (dump_file, " higher_degree_polynomial\n");
2561 stats->nb_higher_poly++;
2570 if (chrec_contains_undetermined (chrec))
2572 if (dump_file && (dump_flags & TDF_STATS))
2573 fprintf (dump_file, " undetermined\n");
2574 stats->nb_undetermined++;
2577 if (dump_file && (dump_flags & TDF_STATS))
2578 fprintf (dump_file, ")\n");
2581 /* One of the drivers for testing the scalar evolutions analysis.
2582 This function analyzes the scalar evolution of all the scalars
2583 defined as loop phi nodes in one of the loops from the
2584 EXIT_CONDITIONS array.
2586 TODO Optimization: A loop is in canonical form if it contains only
2587 a single scalar loop phi node. All the other scalars that have an
2588 evolution in the loop are rewritten in function of this single
2589 index. This allows the parallelization of the loop. */
2592 analyze_scalar_evolution_for_all_loop_phi_nodes (VEC(gimple,heap) **exit_conditions)
2595 struct chrec_stats stats;
2597 gimple_stmt_iterator psi;
2599 reset_chrecs_counters (&stats);
2601 for (i = 0; VEC_iterate (gimple, *exit_conditions, i, cond); i++)
2607 loop = loop_containing_stmt (cond);
2610 for (psi = gsi_start_phis (bb); !gsi_end_p (psi); gsi_next (&psi))
2612 phi = gsi_stmt (psi);
2613 if (is_gimple_reg (PHI_RESULT (phi)))
2615 chrec = instantiate_parameters
2617 analyze_scalar_evolution (loop, PHI_RESULT (phi)));
2619 if (dump_file && (dump_flags & TDF_STATS))
2620 gather_chrec_stats (chrec, &stats);
2625 if (dump_file && (dump_flags & TDF_STATS))
2626 dump_chrecs_stats (dump_file, &stats);
2629 /* Callback for htab_traverse, gathers information on chrecs in the
2633 gather_stats_on_scev_database_1 (void **slot, void *stats)
2635 struct scev_info_str *entry = (struct scev_info_str *) *slot;
2637 gather_chrec_stats (entry->chrec, (struct chrec_stats *) stats);
2642 /* Classify the chrecs of the whole database. */
2645 gather_stats_on_scev_database (void)
2647 struct chrec_stats stats;
2652 reset_chrecs_counters (&stats);
2654 htab_traverse (scalar_evolution_info, gather_stats_on_scev_database_1,
2657 dump_chrecs_stats (dump_file, &stats);
2665 initialize_scalar_evolutions_analyzer (void)
2667 /* The elements below are unique. */
2668 if (chrec_dont_know == NULL_TREE)
2670 chrec_not_analyzed_yet = NULL_TREE;
2671 chrec_dont_know = make_node (SCEV_NOT_KNOWN);
2672 chrec_known = make_node (SCEV_KNOWN);
2673 TREE_TYPE (chrec_dont_know) = void_type_node;
2674 TREE_TYPE (chrec_known) = void_type_node;
2678 /* Initialize the analysis of scalar evolutions for LOOPS. */
2681 scev_initialize (void)
2686 scalar_evolution_info = htab_create_alloc (100,
2693 initialize_scalar_evolutions_analyzer ();
2695 FOR_EACH_LOOP (li, loop, 0)
2697 loop->nb_iterations = NULL_TREE;
2701 /* Cleans up the information cached by the scalar evolutions analysis. */
2709 if (!scalar_evolution_info || !current_loops)
2712 htab_empty (scalar_evolution_info);
2713 FOR_EACH_LOOP (li, loop, 0)
2715 loop->nb_iterations = NULL_TREE;
2719 /* Checks whether OP behaves as a simple affine iv of LOOP in STMT and returns
2720 its base and step in IV if possible. If ALLOW_NONCONSTANT_STEP is true, we
2721 want step to be invariant in LOOP. Otherwise we require it to be an
2722 integer constant. IV->no_overflow is set to true if we are sure the iv cannot
2723 overflow (e.g. because it is computed in signed arithmetics). */
2726 simple_iv (struct loop *loop, gimple stmt, tree op, affine_iv *iv,
2727 bool allow_nonconstant_step)
2729 basic_block bb = gimple_bb (stmt);
2733 iv->base = NULL_TREE;
2734 iv->step = NULL_TREE;
2735 iv->no_overflow = false;
2737 type = TREE_TYPE (op);
2738 if (TREE_CODE (type) != INTEGER_TYPE
2739 && TREE_CODE (type) != POINTER_TYPE)
2742 ev = analyze_scalar_evolution_in_loop (loop, bb->loop_father, op,
2744 if (chrec_contains_undetermined (ev))
2747 if (tree_does_not_contain_chrecs (ev)
2748 && !chrec_contains_symbols_defined_in_loop (ev, loop->num))
2751 iv->step = build_int_cst (TREE_TYPE (ev), 0);
2752 iv->no_overflow = true;
2756 if (TREE_CODE (ev) != POLYNOMIAL_CHREC
2757 || CHREC_VARIABLE (ev) != (unsigned) loop->num)
2760 iv->step = CHREC_RIGHT (ev);
2761 if (allow_nonconstant_step)
2763 if (tree_contains_chrecs (iv->step, NULL)
2764 || chrec_contains_symbols_defined_in_loop (iv->step, loop->num))
2767 else if (TREE_CODE (iv->step) != INTEGER_CST)
2770 iv->base = CHREC_LEFT (ev);
2771 if (tree_contains_chrecs (iv->base, NULL)
2772 || chrec_contains_symbols_defined_in_loop (iv->base, loop->num))
2775 iv->no_overflow = !folded_casts && TYPE_OVERFLOW_UNDEFINED (type);
2780 /* Runs the analysis of scalar evolutions. */
2783 scev_analysis (void)
2785 VEC(gimple,heap) *exit_conditions;
2787 exit_conditions = VEC_alloc (gimple, heap, 37);
2788 select_loops_exit_conditions (&exit_conditions);
2790 if (dump_file && (dump_flags & TDF_STATS))
2791 analyze_scalar_evolution_for_all_loop_phi_nodes (&exit_conditions);
2793 number_of_iterations_for_all_loops (&exit_conditions);
2794 VEC_free (gimple, heap, exit_conditions);
2797 /* Finalize the scalar evolution analysis. */
2800 scev_finalize (void)
2802 if (!scalar_evolution_info)
2804 htab_delete (scalar_evolution_info);
2805 scalar_evolution_info = NULL;
2808 /* Returns true if the expression EXPR is considered to be too expensive
2809 for scev_const_prop. */
2812 expression_expensive_p (tree expr)
2814 enum tree_code code;
2816 if (is_gimple_val (expr))
2819 code = TREE_CODE (expr);
2820 if (code == TRUNC_DIV_EXPR
2821 || code == CEIL_DIV_EXPR
2822 || code == FLOOR_DIV_EXPR
2823 || code == ROUND_DIV_EXPR
2824 || code == TRUNC_MOD_EXPR
2825 || code == CEIL_MOD_EXPR
2826 || code == FLOOR_MOD_EXPR
2827 || code == ROUND_MOD_EXPR
2828 || code == EXACT_DIV_EXPR)
2830 /* Division by power of two is usually cheap, so we allow it.
2831 Forbid anything else. */
2832 if (!integer_pow2p (TREE_OPERAND (expr, 1)))
2836 switch (TREE_CODE_CLASS (code))
2839 case tcc_comparison:
2840 if (expression_expensive_p (TREE_OPERAND (expr, 1)))
2845 return expression_expensive_p (TREE_OPERAND (expr, 0));
2852 /* Replace ssa names for that scev can prove they are constant by the
2853 appropriate constants. Also perform final value replacement in loops,
2854 in case the replacement expressions are cheap.
2856 We only consider SSA names defined by phi nodes; rest is left to the
2857 ordinary constant propagation pass. */
2860 scev_const_prop (void)
2863 tree name, type, ev;
2865 struct loop *loop, *ex_loop;
2866 bitmap ssa_names_to_remove = NULL;
2869 gimple_stmt_iterator psi;
2871 if (number_of_loops () <= 1)
2876 loop = bb->loop_father;
2878 for (psi = gsi_start_phis (bb); !gsi_end_p (psi); gsi_next (&psi))
2880 phi = gsi_stmt (psi);
2881 name = PHI_RESULT (phi);
2883 if (!is_gimple_reg (name))
2886 type = TREE_TYPE (name);
2888 if (!POINTER_TYPE_P (type)
2889 && !INTEGRAL_TYPE_P (type))
2892 ev = resolve_mixers (loop, analyze_scalar_evolution (loop, name));
2893 if (!is_gimple_min_invariant (ev)
2894 || !may_propagate_copy (name, ev))
2897 /* Replace the uses of the name. */
2899 replace_uses_by (name, ev);
2901 if (!ssa_names_to_remove)
2902 ssa_names_to_remove = BITMAP_ALLOC (NULL);
2903 bitmap_set_bit (ssa_names_to_remove, SSA_NAME_VERSION (name));
2907 /* Remove the ssa names that were replaced by constants. We do not
2908 remove them directly in the previous cycle, since this
2909 invalidates scev cache. */
2910 if (ssa_names_to_remove)
2914 EXECUTE_IF_SET_IN_BITMAP (ssa_names_to_remove, 0, i, bi)
2916 gimple_stmt_iterator psi;
2917 name = ssa_name (i);
2918 phi = SSA_NAME_DEF_STMT (name);
2920 gcc_assert (gimple_code (phi) == GIMPLE_PHI);
2921 psi = gsi_for_stmt (phi);
2922 remove_phi_node (&psi, true);
2925 BITMAP_FREE (ssa_names_to_remove);
2929 /* Now the regular final value replacement. */
2930 FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
2933 tree def, rslt, niter;
2934 gimple_stmt_iterator bsi;
2936 /* If we do not know exact number of iterations of the loop, we cannot
2937 replace the final value. */
2938 exit = single_exit (loop);
2942 niter = number_of_latch_executions (loop);
2943 if (niter == chrec_dont_know)
2946 /* Ensure that it is possible to insert new statements somewhere. */
2947 if (!single_pred_p (exit->dest))
2948 split_loop_exit_edge (exit);
2949 bsi = gsi_after_labels (exit->dest);
2951 ex_loop = superloop_at_depth (loop,
2952 loop_depth (exit->dest->loop_father) + 1);
2954 for (psi = gsi_start_phis (exit->dest); !gsi_end_p (psi); )
2956 phi = gsi_stmt (psi);
2957 rslt = PHI_RESULT (phi);
2958 def = PHI_ARG_DEF_FROM_EDGE (phi, exit);
2959 if (!is_gimple_reg (def))
2965 if (!POINTER_TYPE_P (TREE_TYPE (def))
2966 && !INTEGRAL_TYPE_P (TREE_TYPE (def)))
2972 def = analyze_scalar_evolution_in_loop (ex_loop, loop, def, NULL);
2973 def = compute_overall_effect_of_inner_loop (ex_loop, def);
2974 if (!tree_does_not_contain_chrecs (def)
2975 || chrec_contains_symbols_defined_in_loop (def, ex_loop->num)
2976 /* Moving the computation from the loop may prolong life range
2977 of some ssa names, which may cause problems if they appear
2978 on abnormal edges. */
2979 || contains_abnormal_ssa_name_p (def)
2980 /* Do not emit expensive expressions. The rationale is that
2981 when someone writes a code like
2983 while (n > 45) n -= 45;
2985 he probably knows that n is not large, and does not want it
2986 to be turned into n %= 45. */
2987 || expression_expensive_p (def))
2993 /* Eliminate the PHI node and replace it by a computation outside
2995 def = unshare_expr (def);
2996 remove_phi_node (&psi, false);
2998 def = force_gimple_operand_gsi (&bsi, def, false, NULL_TREE,
2999 true, GSI_SAME_STMT);
3000 ass = gimple_build_assign (rslt, def);
3001 gsi_insert_before (&bsi, ass, GSI_SAME_STMT);
3007 #include "gt-tree-scalar-evolution.h"