/* Scalar evolution detector.
- Copyright (C) 2003, 2004 Free Software Foundation, Inc.
+ Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
Contributed by Sebastian Pop <s.pop@laposte.net>
This file is part of GCC.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA. */
+
+/*
+ Description:
+
+ This pass analyzes the evolution of scalar variables in loop
+ structures. The algorithm is based on the SSA representation,
+ and on the loop hierarchy tree. This algorithm is not based on
+ the notion of versions of a variable, as it was the case for the
+ previous implementations of the scalar evolution algorithm, but
+ it assumes that each defined name is unique.
+
+ The notation used in this file is called "chains of recurrences",
+ and has been proposed by Eugene Zima, Robert Van Engelen, and
+ others for describing induction variables in programs. For example
+ "b -> {0, +, 2}_1" means that the scalar variable "b" is equal to 0
+ when entering in the loop_1 and has a step 2 in this loop, in other
+ words "for (b = 0; b < N; b+=2);". Note that the coefficients of
+ this chain of recurrence (or chrec [shrek]) can contain the name of
+ other variables, in which case they are called parametric chrecs.
+ For example, "b -> {a, +, 2}_1" means that the initial value of "b"
+ is the value of "a". In most of the cases these parametric chrecs
+ are fully instantiated before their use because symbolic names can
+ hide some difficult cases such as self-references described later
+ (see the Fibonacci example).
+
+ A short sketch of the algorithm is:
+
+ Given a scalar variable to be analyzed, follow the SSA edge to
+ its definition:
+
+ - When the definition is a GIMPLE_MODIFY_STMT: if the right hand side
+ (RHS) of the definition cannot be statically analyzed, the answer
+ of the analyzer is: "don't know".
+ Otherwise, for all the variables that are not yet analyzed in the
+ RHS, try to determine their evolution, and finally try to
+ evaluate the operation of the RHS that gives the evolution
+ function of the analyzed variable.
+
+ - When the definition is a condition-phi-node: determine the
+ evolution function for all the branches of the phi node, and
+ finally merge these evolutions (see chrec_merge).
+
+ - When the definition is a loop-phi-node: determine its initial
+ condition, that is the SSA edge defined in an outer loop, and
+ keep it symbolic. Then determine the SSA edges that are defined
+ in the body of the loop. Follow the inner edges until ending on
+ another loop-phi-node of the same analyzed loop. If the reached
+ loop-phi-node is not the starting loop-phi-node, then we keep
+ this definition under a symbolic form. If the reached
+ loop-phi-node is the same as the starting one, then we compute a
+ symbolic stride on the return path. The result is then the
+ symbolic chrec {initial_condition, +, symbolic_stride}_loop.
+
+ Examples:
+
+ Example 1: Illustration of the basic algorithm.
+
+ | a = 3
+ | loop_1
+ | b = phi (a, c)
+ | c = b + 1
+ | if (c > 10) exit_loop
+ | endloop
+
+ Suppose that we want to know the number of iterations of the
+ loop_1. The exit_loop is controlled by a COND_EXPR (c > 10). We
+ ask the scalar evolution analyzer two questions: what's the
+ scalar evolution (scev) of "c", and what's the scev of "10". For
+ "10" the answer is "10" since it is a scalar constant. For the
+ scalar variable "c", it follows the SSA edge to its definition,
+ "c = b + 1", and then asks again what's the scev of "b".
+ Following the SSA edge, we end on a loop-phi-node "b = phi (a,
+ c)", where the initial condition is "a", and the inner loop edge
+ is "c". The initial condition is kept under a symbolic form (it
+ may be the case that the copy constant propagation has done its
+ work and we end with the constant "3" as one of the edges of the
+ loop-phi-node). The update edge is followed to the end of the
+ loop, and until reaching again the starting loop-phi-node: b -> c
+ -> b. At this point we have drawn a path from "b" to "b" from
+ which we compute the stride in the loop: in this example it is
+ "+1". The resulting scev for "b" is "b -> {a, +, 1}_1". Now
+ that the scev for "b" is known, it is possible to compute the
+ scev for "c", that is "c -> {a + 1, +, 1}_1". In order to
+ determine the number of iterations in the loop_1, we have to
+ instantiate_parameters ({a + 1, +, 1}_1), that gives after some
+ more analysis the scev {4, +, 1}_1, or in other words, this is
+ the function "f (x) = x + 4", where x is the iteration count of
+ the loop_1. Now we have to solve the inequality "x + 4 > 10",
+ and take the smallest iteration number for which the loop is
+ exited: x = 7. This loop runs from x = 0 to x = 7, and in total
+ there are 8 iterations. In terms of loop normalization, we have
+ created a variable that is implicitly defined, "x" or just "_1",
+ and all the other analyzed scalars of the loop are defined in
+ function of this variable:
+
+ a -> 3
+ b -> {3, +, 1}_1
+ c -> {4, +, 1}_1
+
+ or in terms of a C program:
+
+ | a = 3
+ | for (x = 0; x <= 7; x++)
+ | {
+ | b = x + 3
+ | c = x + 4
+ | }
+
+ Example 2: Illustration of the algorithm on nested loops.
+
+ | loop_1
+ | a = phi (1, b)
+ | c = a + 2
+ | loop_2 10 times
+ | b = phi (c, d)
+ | d = b + 3
+ | endloop
+ | endloop
+
+ For analyzing the scalar evolution of "a", the algorithm follows
+ the SSA edge into the loop's body: "a -> b". "b" is an inner
+ loop-phi-node, and its analysis as in Example 1, gives:
+
+ b -> {c, +, 3}_2
+ d -> {c + 3, +, 3}_2
+
+ Following the SSA edge for the initial condition, we end on "c = a
+ + 2", and then on the starting loop-phi-node "a". From this point,
+ the loop stride is computed: back on "c = a + 2" we get a "+2" in
+ the loop_1, then on the loop-phi-node "b" we compute the overall
+ effect of the inner loop that is "b = c + 30", and we get a "+30"
+ in the loop_1. That means that the overall stride in loop_1 is
+ equal to "+32", and the result is:
+
+ a -> {1, +, 32}_1
+ c -> {3, +, 32}_1
+
+ Example 3: Higher degree polynomials.
+
+ | loop_1
+ | a = phi (2, b)
+ | c = phi (5, d)
+ | b = a + 1
+ | d = c + a
+ | endloop
+
+ a -> {2, +, 1}_1
+ b -> {3, +, 1}_1
+ c -> {5, +, a}_1
+ d -> {5 + a, +, a}_1
+
+ instantiate_parameters ({5, +, a}_1) -> {5, +, 2, +, 1}_1
+ instantiate_parameters ({5 + a, +, a}_1) -> {7, +, 3, +, 1}_1
+
+ Example 4: Lucas, Fibonacci, or mixers in general.
+
+ | loop_1
+ | a = phi (1, b)
+ | c = phi (3, d)
+ | b = c
+ | d = c + a
+ | endloop
+
+ a -> (1, c)_1
+ c -> {3, +, a}_1
+
+ The syntax "(1, c)_1" stands for a PEELED_CHREC that has the
+ following semantics: during the first iteration of the loop_1, the
+ variable contains the value 1, and then it contains the value "c".
+ Note that this syntax is close to the syntax of the loop-phi-node:
+ "a -> (1, c)_1" vs. "a = phi (1, c)".
+
+ The symbolic chrec representation contains all the semantics of the
+ original code. What is more difficult is to use this information.
+
+ Example 5: Flip-flops, or exchangers.
+
+ | loop_1
+ | a = phi (1, b)
+ | c = phi (3, d)
+ | b = c
+ | d = a
+ | endloop
+
+ a -> (1, c)_1
+ c -> (3, a)_1
+
+ Based on these symbolic chrecs, it is possible to refine this
+ information into the more precise PERIODIC_CHRECs:
+
+ a -> |1, 3|_1
+ c -> |3, 1|_1
+
+ This transformation is not yet implemented.
+
+ Further readings:
+
+ You can find a more detailed description of the algorithm in:
+ http://icps.u-strasbg.fr/~pop/DEA_03_Pop.pdf
+ http://icps.u-strasbg.fr/~pop/DEA_03_Pop.ps.gz. But note that
+ this is a preliminary report and some of the details of the
+ algorithm have changed. I'm working on a research report that
+ updates the description of the algorithms to reflect the design
+ choices used in this implementation.
+
+ A set of slides show a high level overview of the algorithm and run
+ an example through the scalar evolution analyzer:
+ http://cri.ensmp.fr/~pop/gcc/mar04/slides.pdf
+
+ The slides that I have presented at the GCC Summit'04 are available
+ at: http://cri.ensmp.fr/~pop/gcc/20040604/gccsummit-lno-spop.pdf
+*/
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
-#include "errors.h"
#include "ggc.h"
#include "tree.h"
+#include "real.h"
+
+/* These RTL headers are needed for basic-block.h. */
#include "rtl.h"
#include "basic-block.h"
#include "diagnostic.h"
#include "cfgloop.h"
#include "tree-chrec.h"
#include "tree-scalar-evolution.h"
+#include "tree-pass.h"
+#include "flags.h"
+#include "params.h"
+
+static tree analyze_scalar_evolution_1 (struct loop *, tree, tree);
+static tree resolve_mixers (struct loop *, tree);
+
+/* The cached information about a ssa name VAR, claiming that inside LOOP,
+ the value of VAR can be expressed as CHREC. */
+
+struct scev_info_str
+{
+ tree var;
+ tree chrec;
+};
+
+/* Counters for the scev database. */
+static unsigned nb_set_scev = 0;
+static unsigned nb_get_scev = 0;
+
+/* The following trees are unique elements. Thus the comparison of
+ another element to these elements should be done on the pointer to
+ these trees, and not on their value. */
+
+/* The SSA_NAMEs that are not yet analyzed are qualified with NULL_TREE. */
+tree chrec_not_analyzed_yet;
+
+/* Reserved to the cases where the analyzer has detected an
+ undecidable property at compile time. */
+tree chrec_dont_know;
+
+/* When the analyzer has detected that a property will never
+ happen, then it qualifies it with chrec_known. */
+tree chrec_known;
+
+static bitmap already_instantiated;
+
+static htab_t scalar_evolution_info;
+
+\f
+/* Constructs a new SCEV_INFO_STR structure. */
+
+static inline struct scev_info_str *
+new_scev_info_str (tree var)
+{
+ struct scev_info_str *res;
+
+ res = XNEW (struct scev_info_str);
+ res->var = var;
+ res->chrec = chrec_not_analyzed_yet;
+
+ return res;
+}
+
+/* Computes a hash function for database element ELT. */
+
+static hashval_t
+hash_scev_info (const void *elt)
+{
+ return SSA_NAME_VERSION (((struct scev_info_str *) elt)->var);
+}
+
+/* Compares database elements E1 and E2. */
+
+static int
+eq_scev_info (const void *e1, const void *e2)
+{
+ const struct scev_info_str *elt1 = (const struct scev_info_str *) e1;
+ const struct scev_info_str *elt2 = (const struct scev_info_str *) e2;
+
+ return elt1->var == elt2->var;
+}
+
+/* Deletes database element E. */
+
+static void
+del_scev_info (void *e)
+{
+ free (e);
+}
+
+/* Get the index corresponding to VAR in the current LOOP. If
+ it's the first time we ask for this VAR, then we return
+ chrec_not_analyzed_yet for this VAR and return its index. */
+
+static tree *
+find_var_scev_info (tree var)
+{
+ struct scev_info_str *res;
+ struct scev_info_str tmp;
+ PTR *slot;
+
+ tmp.var = var;
+ slot = htab_find_slot (scalar_evolution_info, &tmp, INSERT);
+
+ if (!*slot)
+ *slot = new_scev_info_str (var);
+ res = (struct scev_info_str *) *slot;
+
+ return &res->chrec;
+}
+
+/* Return true when CHREC contains symbolic names defined in
+ LOOP_NB. */
+
+bool
+chrec_contains_symbols_defined_in_loop (tree chrec, unsigned loop_nb)
+{
+ if (chrec == NULL_TREE)
+ return false;
+
+ if (TREE_INVARIANT (chrec))
+ return false;
+
+ if (TREE_CODE (chrec) == VAR_DECL
+ || TREE_CODE (chrec) == PARM_DECL
+ || TREE_CODE (chrec) == FUNCTION_DECL
+ || TREE_CODE (chrec) == LABEL_DECL
+ || TREE_CODE (chrec) == RESULT_DECL
+ || TREE_CODE (chrec) == FIELD_DECL)
+ return true;
+
+ if (TREE_CODE (chrec) == SSA_NAME)
+ {
+ tree def = SSA_NAME_DEF_STMT (chrec);
+ struct loop *def_loop = loop_containing_stmt (def);
+ struct loop *loop = current_loops->parray[loop_nb];
+
+ if (def_loop == NULL)
+ return false;
+
+ if (loop == def_loop || flow_loop_nested_p (loop, def_loop))
+ return true;
+
+ return false;
+ }
+
+ switch (TREE_CODE_LENGTH (TREE_CODE (chrec)))
+ {
+ case 3:
+ if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (chrec, 2),
+ loop_nb))
+ return true;
+
+ case 2:
+ if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (chrec, 1),
+ loop_nb))
+ return true;
+
+ case 1:
+ if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (chrec, 0),
+ loop_nb))
+ return true;
+
+ default:
+ return false;
+ }
+}
+
+/* Return true when PHI is a loop-phi-node. */
+
+static bool
+loop_phi_node_p (tree phi)
+{
+ /* The implementation of this function is based on the following
+ property: "all the loop-phi-nodes of a loop are contained in the
+ loop's header basic block". */
+
+ return loop_containing_stmt (phi)->header == bb_for_stmt (phi);
+}
+
+/* Compute the scalar evolution for EVOLUTION_FN after crossing LOOP.
+ In general, in the case of multivariate evolutions we want to get
+ the evolution in different loops. LOOP specifies the level for
+ which to get the evolution.
+
+ Example:
+
+ | for (j = 0; j < 100; j++)
+ | {
+ | for (k = 0; k < 100; k++)
+ | {
+ | i = k + j; - Here the value of i is a function of j, k.
+ | }
+ | ... = i - Here the value of i is a function of j.
+ | }
+ | ... = i - Here the value of i is a scalar.
+
+ Example:
+
+ | i_0 = ...
+ | loop_1 10 times
+ | i_1 = phi (i_0, i_2)
+ | i_2 = i_1 + 2
+ | endloop
+
+ This loop has the same effect as:
+ LOOP_1 has the same effect as:
+
+ | i_1 = i_0 + 20
+
+ The overall effect of the loop, "i_0 + 20" in the previous example,
+ is obtained by passing in the parameters: LOOP = 1,
+ EVOLUTION_FN = {i_0, +, 2}_1.
+*/
+
+static tree
+compute_overall_effect_of_inner_loop (struct loop *loop, tree evolution_fn)
+{
+ bool val = false;
+
+ if (evolution_fn == chrec_dont_know)
+ return chrec_dont_know;
+
+ else if (TREE_CODE (evolution_fn) == POLYNOMIAL_CHREC)
+ {
+ if (CHREC_VARIABLE (evolution_fn) >= (unsigned) loop->num)
+ {
+ struct loop *inner_loop =
+ current_loops->parray[CHREC_VARIABLE (evolution_fn)];
+ tree nb_iter = number_of_iterations_in_loop (inner_loop);
+
+ if (nb_iter == chrec_dont_know)
+ return chrec_dont_know;
+ else
+ {
+ tree res;
+ tree type = chrec_type (nb_iter);
+
+ /* Number of iterations is off by one (the ssa name we
+ analyze must be defined before the exit). */
+ nb_iter = chrec_fold_minus (type, nb_iter,
+ build_int_cst (type, 1));
+
+ /* evolution_fn is the evolution function in LOOP. Get
+ its value in the nb_iter-th iteration. */
+ res = chrec_apply (inner_loop->num, evolution_fn, nb_iter);
+
+ /* Continue the computation until ending on a parent of LOOP. */
+ return compute_overall_effect_of_inner_loop (loop, res);
+ }
+ }
+ else
+ return evolution_fn;
+ }
+
+ /* If the evolution function is an invariant, there is nothing to do. */
+ else if (no_evolution_in_loop_p (evolution_fn, loop->num, &val) && val)
+ return evolution_fn;
+
+ else
+ return chrec_dont_know;
+}
+
+/* Determine whether the CHREC is always positive/negative. If the expression
+ cannot be statically analyzed, return false, otherwise set the answer into
+ VALUE. */
+
+bool
+chrec_is_positive (tree chrec, bool *value)
+{
+ bool value0, value1, value2;
+ tree type, end_value, nb_iter;
+
+ switch (TREE_CODE (chrec))
+ {
+ case POLYNOMIAL_CHREC:
+ if (!chrec_is_positive (CHREC_LEFT (chrec), &value0)
+ || !chrec_is_positive (CHREC_RIGHT (chrec), &value1))
+ return false;
+
+ /* FIXME -- overflows. */
+ if (value0 == value1)
+ {
+ *value = value0;
+ return true;
+ }
+
+ /* Otherwise the chrec is under the form: "{-197, +, 2}_1",
+ and the proof consists in showing that the sign never
+ changes during the execution of the loop, from 0 to
+ loop->nb_iterations. */
+ if (!evolution_function_is_affine_p (chrec))
+ return false;
+
+ nb_iter = number_of_iterations_in_loop
+ (current_loops->parray[CHREC_VARIABLE (chrec)]);
+
+ if (chrec_contains_undetermined (nb_iter))
+ return false;
+
+ type = chrec_type (nb_iter);
+ nb_iter = chrec_fold_minus (type, nb_iter, build_int_cst (type, 1));
+
+#if 0
+ /* TODO -- If the test is after the exit, we may decrease the number of
+ iterations by one. */
+ if (after_exit)
+ nb_iter = chrec_fold_minus (type, nb_iter, build_int_cst (type, 1));
+#endif
+
+ end_value = chrec_apply (CHREC_VARIABLE (chrec), chrec, nb_iter);
+
+ if (!chrec_is_positive (end_value, &value2))
+ return false;
+
+ *value = value0;
+ return value0 == value1;
+
+ case INTEGER_CST:
+ *value = (tree_int_cst_sgn (chrec) == 1);
+ return true;
+
+ default:
+ return false;
+ }
+}
+
+/* Associate CHREC to SCALAR. */
+
+static void
+set_scalar_evolution (tree scalar, tree chrec)
+{
+ tree *scalar_info;
+
+ if (TREE_CODE (scalar) != SSA_NAME)
+ return;
+
+ scalar_info = find_var_scev_info (scalar);
+
+ if (dump_file)
+ {
+ if (dump_flags & TDF_DETAILS)
+ {
+ fprintf (dump_file, "(set_scalar_evolution \n");
+ fprintf (dump_file, " (scalar = ");
+ print_generic_expr (dump_file, scalar, 0);
+ fprintf (dump_file, ")\n (scalar_evolution = ");
+ print_generic_expr (dump_file, chrec, 0);
+ fprintf (dump_file, "))\n");
+ }
+ if (dump_flags & TDF_STATS)
+ nb_set_scev++;
+ }
+
+ *scalar_info = chrec;
+}
+
+/* Retrieve the chrec associated to SCALAR in the LOOP. */
+
+static tree
+get_scalar_evolution (tree scalar)
+{
+ tree res;
+
+ if (dump_file)
+ {
+ if (dump_flags & TDF_DETAILS)
+ {
+ fprintf (dump_file, "(get_scalar_evolution \n");
+ fprintf (dump_file, " (scalar = ");
+ print_generic_expr (dump_file, scalar, 0);
+ fprintf (dump_file, ")\n");
+ }
+ if (dump_flags & TDF_STATS)
+ nb_get_scev++;
+ }
+
+ switch (TREE_CODE (scalar))
+ {
+ case SSA_NAME:
+ res = *find_var_scev_info (scalar);
+ break;
+
+ case REAL_CST:
+ case INTEGER_CST:
+ res = scalar;
+ break;
+
+ default:
+ res = chrec_not_analyzed_yet;
+ break;
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " (scalar_evolution = ");
+ print_generic_expr (dump_file, res, 0);
+ fprintf (dump_file, "))\n");
+ }
+
+ return res;
+}
+
+/* Helper function for add_to_evolution. Returns the evolution
+ function for an assignment of the form "a = b + c", where "a" and
+ "b" are on the strongly connected component. CHREC_BEFORE is the
+ information that we already have collected up to this point.
+ TO_ADD is the evolution of "c".
+
+ When CHREC_BEFORE has an evolution part in LOOP_NB, add to this
+ evolution the expression TO_ADD, otherwise construct an evolution
+ part for this loop. */
+
+static tree
+add_to_evolution_1 (unsigned loop_nb, tree chrec_before, tree to_add,
+ tree at_stmt)
+{
+ tree type, left, right;
+
+ switch (TREE_CODE (chrec_before))
+ {
+ case POLYNOMIAL_CHREC:
+ if (CHREC_VARIABLE (chrec_before) <= loop_nb)
+ {
+ unsigned var;
+
+ type = chrec_type (chrec_before);
+
+ /* When there is no evolution part in this loop, build it. */
+ if (CHREC_VARIABLE (chrec_before) < loop_nb)
+ {
+ var = loop_nb;
+ left = chrec_before;
+ right = SCALAR_FLOAT_TYPE_P (type)
+ ? build_real (type, dconst0)
+ : build_int_cst (type, 0);
+ }
+ else
+ {
+ var = CHREC_VARIABLE (chrec_before);
+ left = CHREC_LEFT (chrec_before);
+ right = CHREC_RIGHT (chrec_before);
+ }
+
+ to_add = chrec_convert (type, to_add, at_stmt);
+ right = chrec_convert (type, right, at_stmt);
+ right = chrec_fold_plus (type, right, to_add);
+ return build_polynomial_chrec (var, left, right);
+ }
+ else
+ {
+ /* Search the evolution in LOOP_NB. */
+ left = add_to_evolution_1 (loop_nb, CHREC_LEFT (chrec_before),
+ to_add, at_stmt);
+ right = CHREC_RIGHT (chrec_before);
+ right = chrec_convert (chrec_type (left), right, at_stmt);
+ return build_polynomial_chrec (CHREC_VARIABLE (chrec_before),
+ left, right);
+ }
+
+ default:
+ /* These nodes do not depend on a loop. */
+ if (chrec_before == chrec_dont_know)
+ return chrec_dont_know;
+
+ left = chrec_before;
+ right = chrec_convert (chrec_type (left), to_add, at_stmt);
+ return build_polynomial_chrec (loop_nb, left, right);
+ }
+}
+
+/* Add TO_ADD to the evolution part of CHREC_BEFORE in the dimension
+ of LOOP_NB.
+
+ Description (provided for completeness, for those who read code in
+ a plane, and for my poor 62 bytes brain that would have forgotten
+ all this in the next two or three months):
+
+ The algorithm of translation of programs from the SSA representation
+ into the chrecs syntax is based on a pattern matching. After having
+ reconstructed the overall tree expression for a loop, there are only
+ two cases that can arise:
+
+ 1. a = loop-phi (init, a + expr)
+ 2. a = loop-phi (init, expr)
+
+ where EXPR is either a scalar constant with respect to the analyzed
+ loop (this is a degree 0 polynomial), or an expression containing
+ other loop-phi definitions (these are higher degree polynomials).
+
+ Examples:
+
+ 1.
+ | init = ...
+ | loop_1
+ | a = phi (init, a + 5)
+ | endloop
+
+ 2.
+ | inita = ...
+ | initb = ...
+ | loop_1
+ | a = phi (inita, 2 * b + 3)
+ | b = phi (initb, b + 1)
+ | endloop
+
+ For the first case, the semantics of the SSA representation is:
+
+ | a (x) = init + \sum_{j = 0}^{x - 1} expr (j)
+
+ that is, there is a loop index "x" that determines the scalar value
+ of the variable during the loop execution. During the first
+ iteration, the value is that of the initial condition INIT, while
+ during the subsequent iterations, it is the sum of the initial
+ condition with the sum of all the values of EXPR from the initial
+ iteration to the before last considered iteration.
+
+ For the second case, the semantics of the SSA program is:
+
+ | a (x) = init, if x = 0;
+ | expr (x - 1), otherwise.
+
+ The second case corresponds to the PEELED_CHREC, whose syntax is
+ close to the syntax of a loop-phi-node:
+
+ | phi (init, expr) vs. (init, expr)_x
+
+ The proof of the translation algorithm for the first case is a
+ proof by structural induction based on the degree of EXPR.
+
+ Degree 0:
+ When EXPR is a constant with respect to the analyzed loop, or in
+ other words when EXPR is a polynomial of degree 0, the evolution of
+ the variable A in the loop is an affine function with an initial
+ condition INIT, and a step EXPR. In order to show this, we start
+ from the semantics of the SSA representation:
+
+ f (x) = init + \sum_{j = 0}^{x - 1} expr (j)
+
+ and since "expr (j)" is a constant with respect to "j",
+
+ f (x) = init + x * expr
+
+ Finally, based on the semantics of the pure sum chrecs, by
+ identification we get the corresponding chrecs syntax:
+
+ f (x) = init * \binom{x}{0} + expr * \binom{x}{1}
+ f (x) -> {init, +, expr}_x
+
+ Higher degree:
+ Suppose that EXPR is a polynomial of degree N with respect to the
+ analyzed loop_x for which we have already determined that it is
+ written under the chrecs syntax:
+
+ | expr (x) -> {b_0, +, b_1, +, ..., +, b_{n-1}} (x)
+
+ We start from the semantics of the SSA program:
+
+ | f (x) = init + \sum_{j = 0}^{x - 1} expr (j)
+ |
+ | f (x) = init + \sum_{j = 0}^{x - 1}
+ | (b_0 * \binom{j}{0} + ... + b_{n-1} * \binom{j}{n-1})
+ |
+ | f (x) = init + \sum_{j = 0}^{x - 1}
+ | \sum_{k = 0}^{n - 1} (b_k * \binom{j}{k})
+ |
+ | f (x) = init + \sum_{k = 0}^{n - 1}
+ | (b_k * \sum_{j = 0}^{x - 1} \binom{j}{k})
+ |
+ | f (x) = init + \sum_{k = 0}^{n - 1}
+ | (b_k * \binom{x}{k + 1})
+ |
+ | f (x) = init + b_0 * \binom{x}{1} + ...
+ | + b_{n-1} * \binom{x}{n}
+ |
+ | f (x) = init * \binom{x}{0} + b_0 * \binom{x}{1} + ...
+ | + b_{n-1} * \binom{x}{n}
+ |
+
+ And finally from the definition of the chrecs syntax, we identify:
+ | f (x) -> {init, +, b_0, +, ..., +, b_{n-1}}_x
+
+ This shows the mechanism that stands behind the add_to_evolution
+ function. An important point is that the use of symbolic
+ parameters avoids the need of an analysis schedule.
+
+ Example:
+
+ | inita = ...
+ | initb = ...
+ | loop_1
+ | a = phi (inita, a + 2 + b)
+ | b = phi (initb, b + 1)
+ | endloop
+
+ When analyzing "a", the algorithm keeps "b" symbolically:
+
+ | a -> {inita, +, 2 + b}_1
+
+ Then, after instantiation, the analyzer ends on the evolution:
+
+ | a -> {inita, +, 2 + initb, +, 1}_1
+
+*/
+
+static tree
+add_to_evolution (unsigned loop_nb, tree chrec_before, enum tree_code code,
+ tree to_add, tree at_stmt)
+{
+ tree type = chrec_type (to_add);
+ tree res = NULL_TREE;
+
+ if (to_add == NULL_TREE)
+ return chrec_before;
+
+ /* TO_ADD is either a scalar, or a parameter. TO_ADD is not
+ instantiated at this point. */
+ if (TREE_CODE (to_add) == POLYNOMIAL_CHREC)
+ /* This should not happen. */
+ return chrec_dont_know;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "(add_to_evolution \n");
+ fprintf (dump_file, " (loop_nb = %d)\n", loop_nb);
+ fprintf (dump_file, " (chrec_before = ");
+ print_generic_expr (dump_file, chrec_before, 0);
+ fprintf (dump_file, ")\n (to_add = ");
+ print_generic_expr (dump_file, to_add, 0);
+ fprintf (dump_file, ")\n");
+ }
+
+ if (code == MINUS_EXPR)
+ to_add = chrec_fold_multiply (type, to_add, SCALAR_FLOAT_TYPE_P (type)
+ ? build_real (type, dconstm1)
+ : build_int_cst_type (type, -1));
+
+ res = add_to_evolution_1 (loop_nb, chrec_before, to_add, at_stmt);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " (res = ");
+ print_generic_expr (dump_file, res, 0);
+ fprintf (dump_file, "))\n");
+ }
+
+ return res;
+}
+
+/* Helper function. */
+
+static inline tree
+set_nb_iterations_in_loop (struct loop *loop,
+ tree res)
+{
+ tree type = chrec_type (res);
+
+ res = chrec_fold_plus (type, res, build_int_cst (type, 1));
+
+ /* FIXME HWI: However we want to store one iteration less than the
+ count of the loop in order to be compatible with the other
+ nb_iter computations in loop-iv. This also allows the
+ representation of nb_iters that are equal to MAX_INT. */
+ if (TREE_CODE (res) == INTEGER_CST
+ && (TREE_INT_CST_LOW (res) == 0
+ || TREE_OVERFLOW (res)))
+ res = chrec_dont_know;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " (set_nb_iterations_in_loop = ");
+ print_generic_expr (dump_file, res, 0);
+ fprintf (dump_file, "))\n");
+ }
+
+ loop->nb_iterations = res;
+ return res;
+}
+
+\f
+
+/* This section selects the loops that will be good candidates for the
+ scalar evolution analysis. For the moment, greedily select all the
+ loop nests we could analyze. */
+
+/* Return true when it is possible to analyze the condition expression
+ EXPR. */
+
+static bool
+analyzable_condition (tree expr)
+{
+ tree condition;
+
+ if (TREE_CODE (expr) != COND_EXPR)
+ return false;
+
+ condition = TREE_OPERAND (expr, 0);
+
+ switch (TREE_CODE (condition))
+ {
+ case SSA_NAME:
+ return true;
+
+ case LT_EXPR:
+ case LE_EXPR:
+ case GT_EXPR:
+ case GE_EXPR:
+ case EQ_EXPR:
+ case NE_EXPR:
+ return true;
+
+ default:
+ return false;
+ }
+
+ return false;
+}
+
+/* For a loop with a single exit edge, return the COND_EXPR that
+ guards the exit edge. If the expression is too difficult to
+ analyze, then give up. */
+
+tree
+get_loop_exit_condition (struct loop *loop)
+{
+ tree res = NULL_TREE;
+ edge exit_edge = single_exit (loop);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "(get_loop_exit_condition \n ");
+
+ if (exit_edge)
+ {
+ tree expr;
+
+ expr = last_stmt (exit_edge->src);
+ if (analyzable_condition (expr))
+ res = expr;
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ print_generic_expr (dump_file, res, 0);
+ fprintf (dump_file, ")\n");
+ }
+
+ return res;
+}
+
+/* Recursively determine and enqueue the exit conditions for a loop. */
+
+static void
+get_exit_conditions_rec (struct loop *loop,
+ VEC(tree,heap) **exit_conditions)
+{
+ if (!loop)
+ return;
+
+ /* Recurse on the inner loops, then on the next (sibling) loops. */
+ get_exit_conditions_rec (loop->inner, exit_conditions);
+ get_exit_conditions_rec (loop->next, exit_conditions);
+
+ if (single_exit (loop))
+ {
+ tree loop_condition = get_loop_exit_condition (loop);
+
+ if (loop_condition)
+ VEC_safe_push (tree, heap, *exit_conditions, loop_condition);
+ }
+}
+
+/* Select the candidate loop nests for the analysis. This function
+ initializes the EXIT_CONDITIONS array. */
+
+static void
+select_loops_exit_conditions (VEC(tree,heap) **exit_conditions)
+{
+ struct loop *function_body = current_loops->tree_root;
+
+ get_exit_conditions_rec (function_body->inner, exit_conditions);
+}
+
+\f
+/* Depth first search algorithm. */
+
+typedef enum t_bool {
+ t_false,
+ t_true,
+ t_dont_know
+} t_bool;
+
+
+static t_bool follow_ssa_edge (struct loop *loop, tree, tree, tree *, int);
+
+/* Follow the ssa edge into the right hand side RHS of an assignment.
+ Return true if the strongly connected component has been found. */
+
+static t_bool
+follow_ssa_edge_in_rhs (struct loop *loop, tree at_stmt, tree rhs,
+ tree halting_phi, tree *evolution_of_loop, int limit)
+{
+ t_bool res = t_false;
+ tree rhs0, rhs1;
+ tree type_rhs = TREE_TYPE (rhs);
+ tree evol;
+
+ /* The RHS is one of the following cases:
+ - an SSA_NAME,
+ - an INTEGER_CST,
+ - a PLUS_EXPR,
+ - a MINUS_EXPR,
+ - an ASSERT_EXPR,
+ - other cases are not yet handled. */
+ switch (TREE_CODE (rhs))
+ {
+ case NOP_EXPR:
+ /* This assignment is under the form "a_1 = (cast) rhs. */
+ res = follow_ssa_edge_in_rhs (loop, at_stmt, TREE_OPERAND (rhs, 0),
+ halting_phi, evolution_of_loop, limit);
+ *evolution_of_loop = chrec_convert (TREE_TYPE (rhs),
+ *evolution_of_loop, at_stmt);
+ break;
+
+ case INTEGER_CST:
+ /* This assignment is under the form "a_1 = 7". */
+ res = t_false;
+ break;
+
+ case SSA_NAME:
+ /* This assignment is under the form: "a_1 = b_2". */
+ res = follow_ssa_edge
+ (loop, SSA_NAME_DEF_STMT (rhs), halting_phi, evolution_of_loop, limit);
+ break;
+
+ case PLUS_EXPR:
+ /* This case is under the form "rhs0 + rhs1". */
+ rhs0 = TREE_OPERAND (rhs, 0);
+ rhs1 = TREE_OPERAND (rhs, 1);
+ STRIP_TYPE_NOPS (rhs0);
+ STRIP_TYPE_NOPS (rhs1);
+
+ if (TREE_CODE (rhs0) == SSA_NAME)
+ {
+ if (TREE_CODE (rhs1) == SSA_NAME)
+ {
+ /* Match an assignment under the form:
+ "a = b + c". */
+ evol = *evolution_of_loop;
+ res = follow_ssa_edge
+ (loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
+ &evol, limit);
+
+ if (res == t_true)
+ *evolution_of_loop = add_to_evolution
+ (loop->num,
+ chrec_convert (type_rhs, evol, at_stmt),
+ PLUS_EXPR, rhs1, at_stmt);
+
+ else if (res == t_false)
+ {
+ res = follow_ssa_edge
+ (loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
+ evolution_of_loop, limit);
+
+ if (res == t_true)
+ *evolution_of_loop = add_to_evolution
+ (loop->num,
+ chrec_convert (type_rhs, *evolution_of_loop, at_stmt),
+ PLUS_EXPR, rhs0, at_stmt);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
+ }
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
+ }
+
+ else
+ {
+ /* Match an assignment under the form:
+ "a = b + ...". */
+ res = follow_ssa_edge
+ (loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
+ evolution_of_loop, limit);
+ if (res == t_true)
+ *evolution_of_loop = add_to_evolution
+ (loop->num, chrec_convert (type_rhs, *evolution_of_loop,
+ at_stmt),
+ PLUS_EXPR, rhs1, at_stmt);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
+ }
+ }
+
+ else if (TREE_CODE (rhs1) == SSA_NAME)
+ {
+ /* Match an assignment under the form:
+ "a = ... + c". */
+ res = follow_ssa_edge
+ (loop, SSA_NAME_DEF_STMT (rhs1), halting_phi,
+ evolution_of_loop, limit);
+ if (res == t_true)
+ *evolution_of_loop = add_to_evolution
+ (loop->num, chrec_convert (type_rhs, *evolution_of_loop,
+ at_stmt),
+ PLUS_EXPR, rhs0, at_stmt);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
+ }
+
+ else
+ /* Otherwise, match an assignment under the form:
+ "a = ... + ...". */
+ /* And there is nothing to do. */
+ res = t_false;
+
+ break;
+
+ case MINUS_EXPR:
+ /* This case is under the form "opnd0 = rhs0 - rhs1". */
+ rhs0 = TREE_OPERAND (rhs, 0);
+ rhs1 = TREE_OPERAND (rhs, 1);
+ STRIP_TYPE_NOPS (rhs0);
+ STRIP_TYPE_NOPS (rhs1);
+
+ if (TREE_CODE (rhs0) == SSA_NAME)
+ {
+ /* Match an assignment under the form:
+ "a = b - ...". */
+ res = follow_ssa_edge (loop, SSA_NAME_DEF_STMT (rhs0), halting_phi,
+ evolution_of_loop, limit);
+ if (res == t_true)
+ *evolution_of_loop = add_to_evolution
+ (loop->num, chrec_convert (type_rhs, *evolution_of_loop, at_stmt),
+ MINUS_EXPR, rhs1, at_stmt);
+
+ else if (res == t_dont_know)
+ *evolution_of_loop = chrec_dont_know;
+ }
+ else
+ /* Otherwise, match an assignment under the form:
+ "a = ... - ...". */
+ /* And there is nothing to do. */
+ res = t_false;
+
+ break;
+
+ case ASSERT_EXPR:
+ {
+ /* This assignment is of the form: "a_1 = ASSERT_EXPR <a_2, ...>"
+ It must be handled as a copy assignment of the form a_1 = a_2. */
+ tree op0 = ASSERT_EXPR_VAR (rhs);
+ if (TREE_CODE (op0) == SSA_NAME)
+ res = follow_ssa_edge (loop, SSA_NAME_DEF_STMT (op0),
+ halting_phi, evolution_of_loop, limit);
+ else
+ res = t_false;
+ break;
+ }
+
+
+ default:
+ res = t_false;
+ break;
+ }
+
+ return res;
+}
+
+/* Checks whether the I-th argument of a PHI comes from a backedge. */
+
+static bool
+backedge_phi_arg_p (tree phi, int i)
+{
+ edge e = PHI_ARG_EDGE (phi, i);
+
+ /* We would in fact like to test EDGE_DFS_BACK here, but we do not care
+ about updating it anywhere, and this should work as well most of the
+ time. */
+ if (e->flags & EDGE_IRREDUCIBLE_LOOP)
+ return true;
+
+ return false;
+}
+
+/* Helper function for one branch of the condition-phi-node. Return
+ true if the strongly connected component has been found following
+ this path. */
+
+static inline t_bool
+follow_ssa_edge_in_condition_phi_branch (int i,
+ struct loop *loop,
+ tree condition_phi,
+ tree halting_phi,
+ tree *evolution_of_branch,
+ tree init_cond, int limit)
+{
+ tree branch = PHI_ARG_DEF (condition_phi, i);
+ *evolution_of_branch = chrec_dont_know;
+
+ /* Do not follow back edges (they must belong to an irreducible loop, which
+ we really do not want to worry about). */
+ if (backedge_phi_arg_p (condition_phi, i))
+ return t_false;
+
+ if (TREE_CODE (branch) == SSA_NAME)
+ {
+ *evolution_of_branch = init_cond;
+ return follow_ssa_edge (loop, SSA_NAME_DEF_STMT (branch), halting_phi,
+ evolution_of_branch, limit);
+ }
+
+ /* This case occurs when one of the condition branches sets
+ the variable to a constant: i.e. a phi-node like
+ "a_2 = PHI <a_7(5), 2(6)>;".
+
+ FIXME: This case have to be refined correctly:
+ in some cases it is possible to say something better than
+ chrec_dont_know, for example using a wrap-around notation. */
+ return t_false;
+}
+
+/* This function merges the branches of a condition-phi-node in a
+ loop. */
+
+static t_bool
+follow_ssa_edge_in_condition_phi (struct loop *loop,
+ tree condition_phi,
+ tree halting_phi,
+ tree *evolution_of_loop, int limit)
+{
+ int i;
+ tree init = *evolution_of_loop;
+ tree evolution_of_branch;
+ t_bool res = follow_ssa_edge_in_condition_phi_branch (0, loop, condition_phi,
+ halting_phi,
+ &evolution_of_branch,
+ init, limit);
+ if (res == t_false || res == t_dont_know)
+ return res;
+
+ *evolution_of_loop = evolution_of_branch;
+
+ for (i = 1; i < PHI_NUM_ARGS (condition_phi); i++)
+ {
+ /* Quickly give up when the evolution of one of the branches is
+ not known. */
+ if (*evolution_of_loop == chrec_dont_know)
+ return t_true;
+
+ res = follow_ssa_edge_in_condition_phi_branch (i, loop, condition_phi,
+ halting_phi,
+ &evolution_of_branch,
+ init, limit);
+ if (res == t_false || res == t_dont_know)
+ return res;
+
+ *evolution_of_loop = chrec_merge (*evolution_of_loop,
+ evolution_of_branch);
+ }
+
+ return t_true;
+}
+
+/* Follow an SSA edge in an inner loop. It computes the overall
+ effect of the loop, and following the symbolic initial conditions,
+ it follows the edges in the parent loop. The inner loop is
+ considered as a single statement. */
+
+static t_bool
+follow_ssa_edge_inner_loop_phi (struct loop *outer_loop,
+ tree loop_phi_node,
+ tree halting_phi,
+ tree *evolution_of_loop, int limit)
+{
+ struct loop *loop = loop_containing_stmt (loop_phi_node);
+ tree ev = analyze_scalar_evolution (loop, PHI_RESULT (loop_phi_node));
+
+ /* Sometimes, the inner loop is too difficult to analyze, and the
+ result of the analysis is a symbolic parameter. */
+ if (ev == PHI_RESULT (loop_phi_node))
+ {
+ t_bool res = t_false;
+ int i;
+
+ for (i = 0; i < PHI_NUM_ARGS (loop_phi_node); i++)
+ {
+ tree arg = PHI_ARG_DEF (loop_phi_node, i);
+ basic_block bb;
+
+ /* Follow the edges that exit the inner loop. */
+ bb = PHI_ARG_EDGE (loop_phi_node, i)->src;
+ if (!flow_bb_inside_loop_p (loop, bb))
+ res = follow_ssa_edge_in_rhs (outer_loop, loop_phi_node,
+ arg, halting_phi,
+ evolution_of_loop, limit);
+ if (res == t_true)
+ break;
+ }
+
+ /* If the path crosses this loop-phi, give up. */
+ if (res == t_true)
+ *evolution_of_loop = chrec_dont_know;
+
+ return res;
+ }
+
+ /* Otherwise, compute the overall effect of the inner loop. */
+ ev = compute_overall_effect_of_inner_loop (loop, ev);
+ return follow_ssa_edge_in_rhs (outer_loop, loop_phi_node, ev, halting_phi,
+ evolution_of_loop, limit);
+}
+
+/* Follow an SSA edge from a loop-phi-node to itself, constructing a
+ path that is analyzed on the return walk. */
+
+static t_bool
+follow_ssa_edge (struct loop *loop, tree def, tree halting_phi,
+ tree *evolution_of_loop, int limit)
+{
+ struct loop *def_loop;
+
+ if (TREE_CODE (def) == NOP_EXPR)
+ return t_false;
+
+ /* Give up if the path is longer than the MAX that we allow. */
+ if (limit++ > PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
+ return t_dont_know;
+
+ def_loop = loop_containing_stmt (def);
+
+ switch (TREE_CODE (def))
+ {
+ case PHI_NODE:
+ if (!loop_phi_node_p (def))
+ /* DEF is a condition-phi-node. Follow the branches, and
+ record their evolutions. Finally, merge the collected
+ information and set the approximation to the main
+ variable. */
+ return follow_ssa_edge_in_condition_phi
+ (loop, def, halting_phi, evolution_of_loop, limit);
+
+ /* When the analyzed phi is the halting_phi, the
+ depth-first search is over: we have found a path from
+ the halting_phi to itself in the loop. */
+ if (def == halting_phi)
+ return t_true;
+
+ /* Otherwise, the evolution of the HALTING_PHI depends
+ on the evolution of another loop-phi-node, i.e. the
+ evolution function is a higher degree polynomial. */
+ if (def_loop == loop)
+ return t_false;
+
+ /* Inner loop. */
+ if (flow_loop_nested_p (loop, def_loop))
+ return follow_ssa_edge_inner_loop_phi
+ (loop, def, halting_phi, evolution_of_loop, limit);
+
+ /* Outer loop. */
+ return t_false;
+
+ case GIMPLE_MODIFY_STMT:
+ return follow_ssa_edge_in_rhs (loop, def,
+ GIMPLE_STMT_OPERAND (def, 1),
+ halting_phi,
+ evolution_of_loop, limit);
+
+ default:
+ /* At this level of abstraction, the program is just a set
+ of GIMPLE_MODIFY_STMTs and PHI_NODEs. In principle there is no
+ other node to be handled. */
+ return t_false;
+ }
+}
+
+\f
+
+/* Given a LOOP_PHI_NODE, this function determines the evolution
+ function from LOOP_PHI_NODE to LOOP_PHI_NODE in the loop. */
+
+static tree
+analyze_evolution_in_loop (tree loop_phi_node,
+ tree init_cond)
+{
+ int i;
+ tree evolution_function = chrec_not_analyzed_yet;
+ struct loop *loop = loop_containing_stmt (loop_phi_node);
+ basic_block bb;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "(analyze_evolution_in_loop \n");
+ fprintf (dump_file, " (loop_phi_node = ");
+ print_generic_expr (dump_file, loop_phi_node, 0);
+ fprintf (dump_file, ")\n");
+ }
+
+ for (i = 0; i < PHI_NUM_ARGS (loop_phi_node); i++)
+ {
+ tree arg = PHI_ARG_DEF (loop_phi_node, i);
+ tree ssa_chain, ev_fn;
+ t_bool res;
+
+ /* Select the edges that enter the loop body. */
+ bb = PHI_ARG_EDGE (loop_phi_node, i)->src;
+ if (!flow_bb_inside_loop_p (loop, bb))
+ continue;
+
+ if (TREE_CODE (arg) == SSA_NAME)
+ {
+ ssa_chain = SSA_NAME_DEF_STMT (arg);
+
+ /* Pass in the initial condition to the follow edge function. */
+ ev_fn = init_cond;
+ res = follow_ssa_edge (loop, ssa_chain, loop_phi_node, &ev_fn, 0);
+ }
+ else
+ res = t_false;
+
+ /* When it is impossible to go back on the same
+ loop_phi_node by following the ssa edges, the
+ evolution is represented by a peeled chrec, i.e. the
+ first iteration, EV_FN has the value INIT_COND, then
+ all the other iterations it has the value of ARG.
+ For the moment, PEELED_CHREC nodes are not built. */
+ if (res != t_true)
+ ev_fn = chrec_dont_know;
+
+ /* When there are multiple back edges of the loop (which in fact never
+ happens currently, but nevertheless), merge their evolutions. */
+ evolution_function = chrec_merge (evolution_function, ev_fn);
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " (evolution_function = ");
+ print_generic_expr (dump_file, evolution_function, 0);
+ fprintf (dump_file, "))\n");
+ }
+
+ return evolution_function;
+}
+
+/* Given a loop-phi-node, return the initial conditions of the
+ variable on entry of the loop. When the CCP has propagated
+ constants into the loop-phi-node, the initial condition is
+ instantiated, otherwise the initial condition is kept symbolic.
+ This analyzer does not analyze the evolution outside the current
+ loop, and leaves this task to the on-demand tree reconstructor. */
+
+static tree
+analyze_initial_condition (tree loop_phi_node)
+{
+ int i;
+ tree init_cond = chrec_not_analyzed_yet;
+ struct loop *loop = bb_for_stmt (loop_phi_node)->loop_father;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "(analyze_initial_condition \n");
+ fprintf (dump_file, " (loop_phi_node = \n");
+ print_generic_expr (dump_file, loop_phi_node, 0);
+ fprintf (dump_file, ")\n");
+ }
+
+ for (i = 0; i < PHI_NUM_ARGS (loop_phi_node); i++)
+ {
+ tree branch = PHI_ARG_DEF (loop_phi_node, i);
+ basic_block bb = PHI_ARG_EDGE (loop_phi_node, i)->src;
+
+ /* When the branch is oriented to the loop's body, it does
+ not contribute to the initial condition. */
+ if (flow_bb_inside_loop_p (loop, bb))
+ continue;
+
+ if (init_cond == chrec_not_analyzed_yet)
+ {
+ init_cond = branch;
+ continue;
+ }
+
+ if (TREE_CODE (branch) == SSA_NAME)
+ {
+ init_cond = chrec_dont_know;
+ break;
+ }
+
+ init_cond = chrec_merge (init_cond, branch);
+ }
+
+ /* Ooops -- a loop without an entry??? */
+ if (init_cond == chrec_not_analyzed_yet)
+ init_cond = chrec_dont_know;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " (init_cond = ");
+ print_generic_expr (dump_file, init_cond, 0);
+ fprintf (dump_file, "))\n");
+ }
+
+ return init_cond;
+}
+
+/* Analyze the scalar evolution for LOOP_PHI_NODE. */
+
+static tree
+interpret_loop_phi (struct loop *loop, tree loop_phi_node)
+{
+ tree res;
+ struct loop *phi_loop = loop_containing_stmt (loop_phi_node);
+ tree init_cond;
+
+ if (phi_loop != loop)
+ {
+ struct loop *subloop;
+ tree evolution_fn = analyze_scalar_evolution
+ (phi_loop, PHI_RESULT (loop_phi_node));
+
+ /* Dive one level deeper. */
+ subloop = superloop_at_depth (phi_loop, loop->depth + 1);
+
+ /* Interpret the subloop. */
+ res = compute_overall_effect_of_inner_loop (subloop, evolution_fn);
+ return res;
+ }
+
+ /* Otherwise really interpret the loop phi. */
+ init_cond = analyze_initial_condition (loop_phi_node);
+ res = analyze_evolution_in_loop (loop_phi_node, init_cond);
+
+ return res;
+}
+
+/* This function merges the branches of a condition-phi-node,
+ contained in the outermost loop, and whose arguments are already
+ analyzed. */
+
+static tree
+interpret_condition_phi (struct loop *loop, tree condition_phi)
+{
+ int i;
+ tree res = chrec_not_analyzed_yet;
+
+ for (i = 0; i < PHI_NUM_ARGS (condition_phi); i++)
+ {
+ tree branch_chrec;
+
+ if (backedge_phi_arg_p (condition_phi, i))
+ {
+ res = chrec_dont_know;
+ break;
+ }
+
+ branch_chrec = analyze_scalar_evolution
+ (loop, PHI_ARG_DEF (condition_phi, i));
+
+ res = chrec_merge (res, branch_chrec);
+ }
+
+ return res;
+}
+
+/* Interpret the right hand side of a GIMPLE_MODIFY_STMT OPND1. If we didn't
+ analyze this node before, follow the definitions until ending
+ either on an analyzed GIMPLE_MODIFY_STMT, or on a loop-phi-node. On the
+ return path, this function propagates evolutions (ala constant copy
+ propagation). OPND1 is not a GIMPLE expression because we could
+ analyze the effect of an inner loop: see interpret_loop_phi. */
+
+static tree
+interpret_rhs_modify_stmt (struct loop *loop, tree at_stmt,
+ tree opnd1, tree type)
+{
+ tree res, opnd10, opnd11, chrec10, chrec11;
+
+ if (is_gimple_min_invariant (opnd1))
+ return chrec_convert (type, opnd1, at_stmt);
+
+ switch (TREE_CODE (opnd1))
+ {
+ case PLUS_EXPR:
+ opnd10 = TREE_OPERAND (opnd1, 0);
+ opnd11 = TREE_OPERAND (opnd1, 1);
+ chrec10 = analyze_scalar_evolution (loop, opnd10);
+ chrec11 = analyze_scalar_evolution (loop, opnd11);
+ chrec10 = chrec_convert (type, chrec10, at_stmt);
+ chrec11 = chrec_convert (type, chrec11, at_stmt);
+ res = chrec_fold_plus (type, chrec10, chrec11);
+ break;
+
+ case MINUS_EXPR:
+ opnd10 = TREE_OPERAND (opnd1, 0);
+ opnd11 = TREE_OPERAND (opnd1, 1);
+ chrec10 = analyze_scalar_evolution (loop, opnd10);
+ chrec11 = analyze_scalar_evolution (loop, opnd11);
+ chrec10 = chrec_convert (type, chrec10, at_stmt);
+ chrec11 = chrec_convert (type, chrec11, at_stmt);
+ res = chrec_fold_minus (type, chrec10, chrec11);
+ break;
+
+ case NEGATE_EXPR:
+ opnd10 = TREE_OPERAND (opnd1, 0);
+ chrec10 = analyze_scalar_evolution (loop, opnd10);
+ chrec10 = chrec_convert (type, chrec10, at_stmt);
+ /* TYPE may be integer, real or complex, so use fold_convert. */
+ res = chrec_fold_multiply (type, chrec10,
+ fold_convert (type, integer_minus_one_node));
+ break;
+
+ case MULT_EXPR:
+ opnd10 = TREE_OPERAND (opnd1, 0);
+ opnd11 = TREE_OPERAND (opnd1, 1);
+ chrec10 = analyze_scalar_evolution (loop, opnd10);
+ chrec11 = analyze_scalar_evolution (loop, opnd11);
+ chrec10 = chrec_convert (type, chrec10, at_stmt);
+ chrec11 = chrec_convert (type, chrec11, at_stmt);
+ res = chrec_fold_multiply (type, chrec10, chrec11);
+ break;
+
+ case SSA_NAME:
+ res = chrec_convert (type, analyze_scalar_evolution (loop, opnd1),
+ at_stmt);
+ break;
+
+ case ASSERT_EXPR:
+ opnd10 = ASSERT_EXPR_VAR (opnd1);
+ res = chrec_convert (type, analyze_scalar_evolution (loop, opnd10),
+ at_stmt);
+ break;
+
+ case NOP_EXPR:
+ case CONVERT_EXPR:
+ opnd10 = TREE_OPERAND (opnd1, 0);
+ chrec10 = analyze_scalar_evolution (loop, opnd10);
+ res = chrec_convert (type, chrec10, at_stmt);
+ break;
+
+ default:
+ res = chrec_dont_know;
+ break;
+ }
+
+ return res;
+}
+
+\f
+
+/* This section contains all the entry points:
+ - number_of_iterations_in_loop,
+ - analyze_scalar_evolution,
+ - instantiate_parameters.
+*/
+
+/* Compute and return the evolution function in WRTO_LOOP, the nearest
+ common ancestor of DEF_LOOP and USE_LOOP. */
+
+static tree
+compute_scalar_evolution_in_loop (struct loop *wrto_loop,
+ struct loop *def_loop,
+ tree ev)
+{
+ tree res;
+ if (def_loop == wrto_loop)
+ return ev;
+
+ def_loop = superloop_at_depth (def_loop, wrto_loop->depth + 1);
+ res = compute_overall_effect_of_inner_loop (def_loop, ev);
+
+ return analyze_scalar_evolution_1 (wrto_loop, res, chrec_not_analyzed_yet);
+}
+
+/* Folds EXPR, if it is a cast to pointer, assuming that the created
+ polynomial_chrec does not wrap. */
+
+static tree
+fold_used_pointer_cast (tree expr)
+{
+ tree op;
+ tree type, inner_type;
+
+ if (TREE_CODE (expr) != NOP_EXPR && TREE_CODE (expr) != CONVERT_EXPR)
+ return expr;
+
+ op = TREE_OPERAND (expr, 0);
+ if (TREE_CODE (op) != POLYNOMIAL_CHREC)
+ return expr;
+
+ type = TREE_TYPE (expr);
+ inner_type = TREE_TYPE (op);
+
+ if (!INTEGRAL_TYPE_P (inner_type)
+ || TYPE_PRECISION (inner_type) != TYPE_PRECISION (type))
+ return expr;
+
+ return build_polynomial_chrec (CHREC_VARIABLE (op),
+ chrec_convert (type, CHREC_LEFT (op), NULL_TREE),
+ chrec_convert (type, CHREC_RIGHT (op), NULL_TREE));
+}
+
+/* Returns true if EXPR is an expression corresponding to offset of pointer
+ in p + offset. */
+
+static bool
+pointer_offset_p (tree expr)
+{
+ if (TREE_CODE (expr) == INTEGER_CST)
+ return true;
+
+ if ((TREE_CODE (expr) == NOP_EXPR || TREE_CODE (expr) == CONVERT_EXPR)
+ && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (expr, 0))))
+ return true;
+
+ return false;
+}
+
+/* EXPR is a scalar evolution of a pointer that is dereferenced or used in
+ comparison. This means that it must point to a part of some object in
+ memory, which enables us to argue about overflows and possibly simplify
+ the EXPR. AT_STMT is the statement in which this conversion has to be
+ performed. Returns the simplified value.
+
+ Currently, for
+
+ int i, n;
+ int *p;
+
+ for (i = -n; i < n; i++)
+ *(p + i) = ...;
+
+ We generate the following code (assuming that size of int and size_t is
+ 4 bytes):
+
+ for (i = -n; i < n; i++)
+ {
+ size_t tmp1, tmp2;
+ int *tmp3, *tmp4;
+
+ tmp1 = (size_t) i; (1)
+ tmp2 = 4 * tmp1; (2)
+ tmp3 = (int *) tmp2; (3)
+ tmp4 = p + tmp3; (4)
+
+ *tmp4 = ...;
+ }
+
+ We in general assume that pointer arithmetics does not overflow (since its
+ behavior is undefined in that case). One of the problems is that our
+ translation does not capture this property very well -- (int *) is
+ considered unsigned, hence the computation in (4) does overflow if i is
+ negative.
+
+ This impreciseness creates complications in scev analysis. The scalar
+ evolution of i is [-n, +, 1]. Since int and size_t have the same precision
+ (in this example), and size_t is unsigned (so we do not care about
+ overflows), we succeed to derive that scev of tmp1 is [(size_t) -n, +, 1]
+ and scev of tmp2 is [4 * (size_t) -n, +, 4]. With tmp3, we run into
+ problem -- [(int *) (4 * (size_t) -n), +, 4] wraps, and since we on several
+ places assume that this is not the case for scevs with pointer type, we
+ cannot use this scev for tmp3; hence, its scev is
+ (int *) [(4 * (size_t) -n), +, 4], and scev of tmp4 is
+ p + (int *) [(4 * (size_t) -n), +, 4]. Most of the optimizers are unable to
+ work with scevs of this shape.
+
+ However, since tmp4 is dereferenced, all its values must belong to a single
+ object, and taking into account that the precision of int * and size_t is
+ the same, it is impossible for its scev to wrap. Hence, we can derive that
+ its evolution is [p + (int *) (4 * (size_t) -n), +, 4], which the optimizers
+ can work with.
+
+ ??? Maybe we should use different representation for pointer arithmetics,
+ however that is a long-term project with a lot of potential for creating
+ bugs. */
+
+static tree
+fold_used_pointer (tree expr, tree at_stmt)
+{
+ tree op0, op1, new0, new1;
+ enum tree_code code = TREE_CODE (expr);
+
+ if (code == PLUS_EXPR
+ || code == MINUS_EXPR)
+ {
+ op0 = TREE_OPERAND (expr, 0);
+ op1 = TREE_OPERAND (expr, 1);
+
+ if (pointer_offset_p (op1))
+ {
+ new0 = fold_used_pointer (op0, at_stmt);
+ new1 = fold_used_pointer_cast (op1);
+ }
+ else if (code == PLUS_EXPR && pointer_offset_p (op0))
+ {
+ new0 = fold_used_pointer_cast (op0);
+ new1 = fold_used_pointer (op1, at_stmt);
+ }
+ else
+ return expr;
+
+ if (new0 == op0 && new1 == op1)
+ return expr;
+
+ new0 = chrec_convert (TREE_TYPE (expr), new0, at_stmt);
+ new1 = chrec_convert (TREE_TYPE (expr), new1, at_stmt);
+
+ if (code == PLUS_EXPR)
+ expr = chrec_fold_plus (TREE_TYPE (expr), new0, new1);
+ else
+ expr = chrec_fold_minus (TREE_TYPE (expr), new0, new1);
+
+ return expr;
+ }
+ else
+ return fold_used_pointer_cast (expr);
+}
+
+/* Returns true if PTR is dereferenced, or used in comparison. */
+
+static bool
+pointer_used_p (tree ptr)
+{
+ use_operand_p use_p;
+ imm_use_iterator imm_iter;
+ tree stmt, rhs;
+ struct ptr_info_def *pi = get_ptr_info (ptr);
+ var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
+
+ /* Check whether the pointer has a memory tag; if it does, it is
+ (or at least used to be) dereferenced. */
+ if ((pi != NULL && pi->name_mem_tag != NULL)
+ || v_ann->symbol_mem_tag)
+ return true;
+
+ FOR_EACH_IMM_USE_FAST (use_p, imm_iter, ptr)
+ {
+ stmt = USE_STMT (use_p);
+ if (TREE_CODE (stmt) == COND_EXPR)
+ return true;
+
+ if (TREE_CODE (stmt) != GIMPLE_MODIFY_STMT)
+ continue;
+
+ rhs = GIMPLE_STMT_OPERAND (stmt, 1);
+ if (!COMPARISON_CLASS_P (rhs))
+ continue;
+
+ if (GIMPLE_STMT_OPERAND (stmt, 0) == ptr
+ || GIMPLE_STMT_OPERAND (stmt, 1) == ptr)
+ return true;
+ }
+
+ return false;
+}
+
+/* Helper recursive function. */
+
+static tree
+analyze_scalar_evolution_1 (struct loop *loop, tree var, tree res)
+{
+ tree def, type = TREE_TYPE (var);
+ basic_block bb;
+ struct loop *def_loop;
+
+ if (loop == NULL || TREE_CODE (type) == VECTOR_TYPE)
+ return chrec_dont_know;
+
+ if (TREE_CODE (var) != SSA_NAME)
+ return interpret_rhs_modify_stmt (loop, NULL_TREE, var, type);
+
+ def = SSA_NAME_DEF_STMT (var);
+ bb = bb_for_stmt (def);
+ def_loop = bb ? bb->loop_father : NULL;
+
+ if (bb == NULL
+ || !flow_bb_inside_loop_p (loop, bb))
+ {
+ /* Keep the symbolic form. */
+ res = var;
+ goto set_and_end;
+ }
+
+ if (res != chrec_not_analyzed_yet)
+ {
+ if (loop != bb->loop_father)
+ res = compute_scalar_evolution_in_loop
+ (find_common_loop (loop, bb->loop_father), bb->loop_father, res);
+
+ goto set_and_end;
+ }
+
+ if (loop != def_loop)
+ {
+ res = analyze_scalar_evolution_1 (def_loop, var, chrec_not_analyzed_yet);
+ res = compute_scalar_evolution_in_loop (loop, def_loop, res);
+
+ goto set_and_end;
+ }
+
+ switch (TREE_CODE (def))
+ {
+ case GIMPLE_MODIFY_STMT:
+ res = interpret_rhs_modify_stmt (loop, def,
+ GIMPLE_STMT_OPERAND (def, 1), type);
+
+ if (POINTER_TYPE_P (type)
+ && !automatically_generated_chrec_p (res)
+ && pointer_used_p (var))
+ res = fold_used_pointer (res, def);
+ break;
+
+ case PHI_NODE:
+ if (loop_phi_node_p (def))
+ res = interpret_loop_phi (loop, def);
+ else
+ res = interpret_condition_phi (loop, def);
+ break;
+
+ default:
+ res = chrec_dont_know;
+ break;
+ }
+
+ set_and_end:
+
+ /* Keep the symbolic form. */
+ if (res == chrec_dont_know)
+ res = var;
+
+ if (loop == def_loop)
+ set_scalar_evolution (var, res);
+
+ return res;
+}
+
+/* Entry point for the scalar evolution analyzer.
+ Analyzes and returns the scalar evolution of the ssa_name VAR.
+ LOOP_NB is the identifier number of the loop in which the variable
+ is used.
+
+ Example of use: having a pointer VAR to a SSA_NAME node, STMT a
+ pointer to the statement that uses this variable, in order to
+ determine the evolution function of the variable, use the following
+ calls:
+
+ unsigned loop_nb = loop_containing_stmt (stmt)->num;
+ tree chrec_with_symbols = analyze_scalar_evolution (loop_nb, var);
+ tree chrec_instantiated = instantiate_parameters
+ (loop_nb, chrec_with_symbols);
+*/
+
+tree
+analyze_scalar_evolution (struct loop *loop, tree var)
+{
+ tree res;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "(analyze_scalar_evolution \n");
+ fprintf (dump_file, " (loop_nb = %d)\n", loop->num);
+ fprintf (dump_file, " (scalar = ");
+ print_generic_expr (dump_file, var, 0);
+ fprintf (dump_file, ")\n");
+ }
+
+ res = analyze_scalar_evolution_1 (loop, var, get_scalar_evolution (var));
+
+ if (TREE_CODE (var) == SSA_NAME && res == chrec_dont_know)
+ res = var;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, ")\n");
+
+ return res;
+}
+
+/* Analyze scalar evolution of use of VERSION in USE_LOOP with respect to
+ WRTO_LOOP (which should be a superloop of both USE_LOOP and definition
+ of VERSION).
+
+ FOLDED_CASTS is set to true if resolve_mixers used
+ chrec_convert_aggressive (TODO -- not really, we are way too conservative
+ at the moment in order to keep things simple). */
+
+static tree
+analyze_scalar_evolution_in_loop (struct loop *wrto_loop, struct loop *use_loop,
+ tree version, bool *folded_casts)
+{
+ bool val = false;
+ tree ev = version, tmp;
+
+ if (folded_casts)
+ *folded_casts = false;
+ while (1)
+ {
+ tmp = analyze_scalar_evolution (use_loop, ev);
+ ev = resolve_mixers (use_loop, tmp);
+
+ if (folded_casts && tmp != ev)
+ *folded_casts = true;
+
+ if (use_loop == wrto_loop)
+ return ev;
+
+ /* If the value of the use changes in the inner loop, we cannot express
+ its value in the outer loop (we might try to return interval chrec,
+ but we do not have a user for it anyway) */
+ if (!no_evolution_in_loop_p (ev, use_loop->num, &val)
+ || !val)
+ return chrec_dont_know;
+
+ use_loop = use_loop->outer;
+ }
+}
+
+/* Returns instantiated value for VERSION in CACHE. */
+
+static tree
+get_instantiated_value (htab_t cache, tree version)
+{
+ struct scev_info_str *info, pattern;
+
+ pattern.var = version;
+ info = (struct scev_info_str *) htab_find (cache, &pattern);
+
+ if (info)
+ return info->chrec;
+ else
+ return NULL_TREE;
+}
+
+/* Sets instantiated value for VERSION to VAL in CACHE. */
+
+static void
+set_instantiated_value (htab_t cache, tree version, tree val)
+{
+ struct scev_info_str *info, pattern;
+ PTR *slot;
+
+ pattern.var = version;
+ slot = htab_find_slot (cache, &pattern, INSERT);
+
+ if (!*slot)
+ *slot = new_scev_info_str (version);
+ info = (struct scev_info_str *) *slot;
+ info->chrec = val;
+}
+
+/* Return the closed_loop_phi node for VAR. If there is none, return
+ NULL_TREE. */
+
+static tree
+loop_closed_phi_def (tree var)
+{
+ struct loop *loop;
+ edge exit;
+ tree phi;
+
+ if (var == NULL_TREE
+ || TREE_CODE (var) != SSA_NAME)
+ return NULL_TREE;
+
+ loop = loop_containing_stmt (SSA_NAME_DEF_STMT (var));
+ exit = single_exit (loop);
+ if (!exit)
+ return NULL_TREE;
+
+ for (phi = phi_nodes (exit->dest); phi; phi = PHI_CHAIN (phi))
+ if (PHI_ARG_DEF_FROM_EDGE (phi, exit) == var)
+ return PHI_RESULT (phi);
+
+ return NULL_TREE;
+}
+
+/* Analyze all the parameters of the chrec that were left under a symbolic form,
+ with respect to LOOP. CHREC is the chrec to instantiate. CACHE is the cache
+ of already instantiated values. FLAGS modify the way chrecs are
+ instantiated. SIZE_EXPR is used for computing the size of the expression to
+ be instantiated, and to stop if it exceeds some limit. */
+
+/* Values for FLAGS. */
+enum
+{
+ INSERT_SUPERLOOP_CHRECS = 1, /* Loop invariants are replaced with chrecs
+ in outer loops. */
+ FOLD_CONVERSIONS = 2 /* The conversions that may wrap in
+ signed/pointer type are folded, as long as the
+ value of the chrec is preserved. */
+};
+
+static tree
+instantiate_parameters_1 (struct loop *loop, tree chrec, int flags, htab_t cache,
+ int size_expr)
+{
+ tree res, op0, op1, op2;
+ basic_block def_bb;
+ struct loop *def_loop;
+ tree type = chrec_type (chrec);
+
+ /* Give up if the expression is larger than the MAX that we allow. */
+ if (size_expr++ > PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
+ return chrec_dont_know;
+
+ if (automatically_generated_chrec_p (chrec)
+ || is_gimple_min_invariant (chrec))
+ return chrec;
+
+ switch (TREE_CODE (chrec))
+ {
+ case SSA_NAME:
+ def_bb = bb_for_stmt (SSA_NAME_DEF_STMT (chrec));
+
+ /* A parameter (or loop invariant and we do not want to include
+ evolutions in outer loops), nothing to do. */
+ if (!def_bb
+ || (!(flags & INSERT_SUPERLOOP_CHRECS)
+ && !flow_bb_inside_loop_p (loop, def_bb)))
+ return chrec;
+
+ /* We cache the value of instantiated variable to avoid exponential
+ time complexity due to reevaluations. We also store the convenient
+ value in the cache in order to prevent infinite recursion -- we do
+ not want to instantiate the SSA_NAME if it is in a mixer
+ structure. This is used for avoiding the instantiation of
+ recursively defined functions, such as:
+
+ | a_2 -> {0, +, 1, +, a_2}_1 */
+
+ res = get_instantiated_value (cache, chrec);
+ if (res)
+ return res;
+
+ /* Store the convenient value for chrec in the structure. If it
+ is defined outside of the loop, we may just leave it in symbolic
+ form, otherwise we need to admit that we do not know its behavior
+ inside the loop. */
+ res = !flow_bb_inside_loop_p (loop, def_bb) ? chrec : chrec_dont_know;
+ set_instantiated_value (cache, chrec, res);
+
+ /* To make things even more complicated, instantiate_parameters_1
+ calls analyze_scalar_evolution that may call # of iterations
+ analysis that may in turn call instantiate_parameters_1 again.
+ To prevent the infinite recursion, keep also the bitmap of
+ ssa names that are being instantiated globally. */
+ if (bitmap_bit_p (already_instantiated, SSA_NAME_VERSION (chrec)))
+ return res;
+
+ def_loop = find_common_loop (loop, def_bb->loop_father);
+
+ /* If the analysis yields a parametric chrec, instantiate the
+ result again. */
+ bitmap_set_bit (already_instantiated, SSA_NAME_VERSION (chrec));
+ res = analyze_scalar_evolution (def_loop, chrec);
+
+ /* Don't instantiate loop-closed-ssa phi nodes. */
+ if (TREE_CODE (res) == SSA_NAME
+ && (loop_containing_stmt (SSA_NAME_DEF_STMT (res)) == NULL
+ || (loop_containing_stmt (SSA_NAME_DEF_STMT (res))->depth
+ > def_loop->depth)))
+ {
+ if (res == chrec)
+ res = loop_closed_phi_def (chrec);
+ else
+ res = chrec;
+
+ if (res == NULL_TREE)
+ res = chrec_dont_know;
+ }
+
+ else if (res != chrec_dont_know)
+ res = instantiate_parameters_1 (loop, res, flags, cache, size_expr);
+
+ bitmap_clear_bit (already_instantiated, SSA_NAME_VERSION (chrec));
+
+ /* Store the correct value to the cache. */
+ set_instantiated_value (cache, chrec, res);
+ return res;
+
+ case POLYNOMIAL_CHREC:
+ op0 = instantiate_parameters_1 (loop, CHREC_LEFT (chrec),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+
+ op1 = instantiate_parameters_1 (loop, CHREC_RIGHT (chrec),
+ flags, cache, size_expr);
+ if (op1 == chrec_dont_know)
+ return chrec_dont_know;
+
+ if (CHREC_LEFT (chrec) != op0
+ || CHREC_RIGHT (chrec) != op1)
+ {
+ op1 = chrec_convert (chrec_type (op0), op1, NULL_TREE);
+ chrec = build_polynomial_chrec (CHREC_VARIABLE (chrec), op0, op1);
+ }
+ return chrec;
+
+ case PLUS_EXPR:
+ op0 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 0),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+
+ op1 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 1),
+ flags, cache, size_expr);
+ if (op1 == chrec_dont_know)
+ return chrec_dont_know;
+
+ if (TREE_OPERAND (chrec, 0) != op0
+ || TREE_OPERAND (chrec, 1) != op1)
+ {
+ op0 = chrec_convert (type, op0, NULL_TREE);
+ op1 = chrec_convert (type, op1, NULL_TREE);
+ chrec = chrec_fold_plus (type, op0, op1);
+ }
+ return chrec;
+
+ case MINUS_EXPR:
+ op0 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 0),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+
+ op1 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 1),
+ flags, cache, size_expr);
+ if (op1 == chrec_dont_know)
+ return chrec_dont_know;
+
+ if (TREE_OPERAND (chrec, 0) != op0
+ || TREE_OPERAND (chrec, 1) != op1)
+ {
+ op0 = chrec_convert (type, op0, NULL_TREE);
+ op1 = chrec_convert (type, op1, NULL_TREE);
+ chrec = chrec_fold_minus (type, op0, op1);
+ }
+ return chrec;
+
+ case MULT_EXPR:
+ op0 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 0),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+
+ op1 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 1),
+ flags, cache, size_expr);
+ if (op1 == chrec_dont_know)
+ return chrec_dont_know;
+
+ if (TREE_OPERAND (chrec, 0) != op0
+ || TREE_OPERAND (chrec, 1) != op1)
+ {
+ op0 = chrec_convert (type, op0, NULL_TREE);
+ op1 = chrec_convert (type, op1, NULL_TREE);
+ chrec = chrec_fold_multiply (type, op0, op1);
+ }
+ return chrec;
+
+ case NOP_EXPR:
+ case CONVERT_EXPR:
+ case NON_LVALUE_EXPR:
+ op0 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 0),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+
+ if (flags & FOLD_CONVERSIONS)
+ {
+ tree tmp = chrec_convert_aggressive (TREE_TYPE (chrec), op0);
+ if (tmp)
+ return tmp;
+ }
+
+ if (op0 == TREE_OPERAND (chrec, 0))
+ return chrec;
+
+ /* If we used chrec_convert_aggressive, we can no longer assume that
+ signed chrecs do not overflow, as chrec_convert does, so avoid
+ calling it in that case. */
+ if (flags & FOLD_CONVERSIONS)
+ return fold_convert (TREE_TYPE (chrec), op0);
+
+ return chrec_convert (TREE_TYPE (chrec), op0, NULL_TREE);
+
+ case SCEV_NOT_KNOWN:
+ return chrec_dont_know;
+
+ case SCEV_KNOWN:
+ return chrec_known;
+
+ default:
+ break;
+ }
+
+ switch (TREE_CODE_LENGTH (TREE_CODE (chrec)))
+ {
+ case 3:
+ op0 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 0),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+
+ op1 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 1),
+ flags, cache, size_expr);
+ if (op1 == chrec_dont_know)
+ return chrec_dont_know;
+
+ op2 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 2),
+ flags, cache, size_expr);
+ if (op2 == chrec_dont_know)
+ return chrec_dont_know;
+
+ if (op0 == TREE_OPERAND (chrec, 0)
+ && op1 == TREE_OPERAND (chrec, 1)
+ && op2 == TREE_OPERAND (chrec, 2))
+ return chrec;
+
+ return fold_build3 (TREE_CODE (chrec),
+ TREE_TYPE (chrec), op0, op1, op2);
+
+ case 2:
+ op0 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 0),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+
+ op1 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 1),
+ flags, cache, size_expr);
+ if (op1 == chrec_dont_know)
+ return chrec_dont_know;
+
+ if (op0 == TREE_OPERAND (chrec, 0)
+ && op1 == TREE_OPERAND (chrec, 1))
+ return chrec;
+ return fold_build2 (TREE_CODE (chrec), TREE_TYPE (chrec), op0, op1);
+
+ case 1:
+ op0 = instantiate_parameters_1 (loop, TREE_OPERAND (chrec, 0),
+ flags, cache, size_expr);
+ if (op0 == chrec_dont_know)
+ return chrec_dont_know;
+ if (op0 == TREE_OPERAND (chrec, 0))
+ return chrec;
+ return fold_build1 (TREE_CODE (chrec), TREE_TYPE (chrec), op0);
+
+ case 0:
+ return chrec;
+
+ default:
+ break;
+ }
+
+ /* Too complicated to handle. */
+ return chrec_dont_know;
+}
/* Analyze all the parameters of the chrec that were left under a
symbolic form. LOOP is the loop in which symbolic names have to
be analyzed and instantiated. */
tree
-instantiate_parameters (struct loop *loop ATTRIBUTE_UNUSED,
+instantiate_parameters (struct loop *loop,
tree chrec)
{
- /* Just a dummy definition for now. */
- return chrec;
+ tree res;
+ htab_t cache = htab_create (10, hash_scev_info, eq_scev_info, del_scev_info);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "(instantiate_parameters \n");
+ fprintf (dump_file, " (loop_nb = %d)\n", loop->num);
+ fprintf (dump_file, " (chrec = ");
+ print_generic_expr (dump_file, chrec, 0);
+ fprintf (dump_file, ")\n");
+ }
+
+ res = instantiate_parameters_1 (loop, chrec, INSERT_SUPERLOOP_CHRECS, cache,
+ 0);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " (res = ");
+ print_generic_expr (dump_file, res, 0);
+ fprintf (dump_file, "))\n");
+ }
+
+ htab_delete (cache);
+
+ return res;
+}
+
+/* Similar to instantiate_parameters, but does not introduce the
+ evolutions in outer loops for LOOP invariants in CHREC, and does not
+ care about causing overflows, as long as they do not affect value
+ of an expression. */
+
+static tree
+resolve_mixers (struct loop *loop, tree chrec)
+{
+ htab_t cache = htab_create (10, hash_scev_info, eq_scev_info, del_scev_info);
+ tree ret = instantiate_parameters_1 (loop, chrec, FOLD_CONVERSIONS, cache, 0);
+ htab_delete (cache);
+ return ret;
+}
+
+/* Entry point for the analysis of the number of iterations pass.
+ This function tries to safely approximate the number of iterations
+ the loop will run. When this property is not decidable at compile
+ time, the result is chrec_dont_know. Otherwise the result is
+ a scalar or a symbolic parameter.
+
+ Example of analysis: suppose that the loop has an exit condition:
+
+ "if (b > 49) goto end_loop;"
+
+ and that in a previous analysis we have determined that the
+ variable 'b' has an evolution function:
+
+ "EF = {23, +, 5}_2".
+
+ When we evaluate the function at the point 5, i.e. the value of the
+ variable 'b' after 5 iterations in the loop, we have EF (5) = 48,
+ and EF (6) = 53. In this case the value of 'b' on exit is '53' and
+ the loop body has been executed 6 times. */
+
+tree
+number_of_iterations_in_loop (struct loop *loop)
+{
+ tree res, type;
+ edge exit;
+ struct tree_niter_desc niter_desc;
+
+ /* Determine whether the number_of_iterations_in_loop has already
+ been computed. */
+ res = loop->nb_iterations;
+ if (res)
+ return res;
+ res = chrec_dont_know;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "(number_of_iterations_in_loop\n");
+
+ exit = single_exit (loop);
+ if (!exit)
+ goto end;
+
+ if (!number_of_iterations_exit (loop, exit, &niter_desc, false))
+ goto end;
+
+ type = TREE_TYPE (niter_desc.niter);
+ if (integer_nonzerop (niter_desc.may_be_zero))
+ res = build_int_cst (type, 0);
+ else if (integer_zerop (niter_desc.may_be_zero))
+ res = niter_desc.niter;
+ else
+ res = chrec_dont_know;
+
+end:
+ return set_nb_iterations_in_loop (loop, res);
+}
+
+/* One of the drivers for testing the scalar evolutions analysis.
+ This function computes the number of iterations for all the loops
+ from the EXIT_CONDITIONS array. */
+
+static void
+number_of_iterations_for_all_loops (VEC(tree,heap) **exit_conditions)
+{
+ unsigned int i;
+ unsigned nb_chrec_dont_know_loops = 0;
+ unsigned nb_static_loops = 0;
+ tree cond;
+
+ for (i = 0; VEC_iterate (tree, *exit_conditions, i, cond); i++)
+ {
+ tree res = number_of_iterations_in_loop (loop_containing_stmt (cond));
+ if (chrec_contains_undetermined (res))
+ nb_chrec_dont_know_loops++;
+ else
+ nb_static_loops++;
+ }
+
+ if (dump_file)
+ {
+ fprintf (dump_file, "\n(\n");
+ fprintf (dump_file, "-----------------------------------------\n");
+ fprintf (dump_file, "%d\tnb_chrec_dont_know_loops\n", nb_chrec_dont_know_loops);
+ fprintf (dump_file, "%d\tnb_static_loops\n", nb_static_loops);
+ fprintf (dump_file, "%d\tnb_total_loops\n", current_loops->num);
+ fprintf (dump_file, "-----------------------------------------\n");
+ fprintf (dump_file, ")\n\n");
+
+ print_loop_ir (dump_file);
+ }
+}
+
+\f
+
+/* Counters for the stats. */
+
+struct chrec_stats
+{
+ unsigned nb_chrecs;
+ unsigned nb_affine;
+ unsigned nb_affine_multivar;
+ unsigned nb_higher_poly;
+ unsigned nb_chrec_dont_know;
+ unsigned nb_undetermined;
+};
+
+/* Reset the counters. */
+
+static inline void
+reset_chrecs_counters (struct chrec_stats *stats)
+{
+ stats->nb_chrecs = 0;
+ stats->nb_affine = 0;
+ stats->nb_affine_multivar = 0;
+ stats->nb_higher_poly = 0;
+ stats->nb_chrec_dont_know = 0;
+ stats->nb_undetermined = 0;
+}
+
+/* Dump the contents of a CHREC_STATS structure. */
+
+static void
+dump_chrecs_stats (FILE *file, struct chrec_stats *stats)
+{
+ fprintf (file, "\n(\n");
+ fprintf (file, "-----------------------------------------\n");
+ fprintf (file, "%d\taffine univariate chrecs\n", stats->nb_affine);
+ fprintf (file, "%d\taffine multivariate chrecs\n", stats->nb_affine_multivar);
+ fprintf (file, "%d\tdegree greater than 2 polynomials\n",
+ stats->nb_higher_poly);
+ fprintf (file, "%d\tchrec_dont_know chrecs\n", stats->nb_chrec_dont_know);
+ fprintf (file, "-----------------------------------------\n");
+ fprintf (file, "%d\ttotal chrecs\n", stats->nb_chrecs);
+ fprintf (file, "%d\twith undetermined coefficients\n",
+ stats->nb_undetermined);
+ fprintf (file, "-----------------------------------------\n");
+ fprintf (file, "%d\tchrecs in the scev database\n",
+ (int) htab_elements (scalar_evolution_info));
+ fprintf (file, "%d\tsets in the scev database\n", nb_set_scev);
+ fprintf (file, "%d\tgets in the scev database\n", nb_get_scev);
+ fprintf (file, "-----------------------------------------\n");
+ fprintf (file, ")\n\n");
+}
+
+/* Gather statistics about CHREC. */
+
+static void
+gather_chrec_stats (tree chrec, struct chrec_stats *stats)
+{
+ if (dump_file && (dump_flags & TDF_STATS))
+ {
+ fprintf (dump_file, "(classify_chrec ");
+ print_generic_expr (dump_file, chrec, 0);
+ fprintf (dump_file, "\n");
+ }
+
+ stats->nb_chrecs++;
+
+ if (chrec == NULL_TREE)
+ {
+ stats->nb_undetermined++;
+ return;
+ }
+
+ switch (TREE_CODE (chrec))
+ {
+ case POLYNOMIAL_CHREC:
+ if (evolution_function_is_affine_p (chrec))
+ {
+ if (dump_file && (dump_flags & TDF_STATS))
+ fprintf (dump_file, " affine_univariate\n");
+ stats->nb_affine++;
+ }
+ else if (evolution_function_is_affine_multivariate_p (chrec))
+ {
+ if (dump_file && (dump_flags & TDF_STATS))
+ fprintf (dump_file, " affine_multivariate\n");
+ stats->nb_affine_multivar++;
+ }
+ else
+ {
+ if (dump_file && (dump_flags & TDF_STATS))
+ fprintf (dump_file, " higher_degree_polynomial\n");
+ stats->nb_higher_poly++;
+ }
+
+ break;
+
+ default:
+ break;
+ }
+
+ if (chrec_contains_undetermined (chrec))
+ {
+ if (dump_file && (dump_flags & TDF_STATS))
+ fprintf (dump_file, " undetermined\n");
+ stats->nb_undetermined++;
+ }
+
+ if (dump_file && (dump_flags & TDF_STATS))
+ fprintf (dump_file, ")\n");
+}
+
+/* One of the drivers for testing the scalar evolutions analysis.
+ This function analyzes the scalar evolution of all the scalars
+ defined as loop phi nodes in one of the loops from the
+ EXIT_CONDITIONS array.
+
+ TODO Optimization: A loop is in canonical form if it contains only
+ a single scalar loop phi node. All the other scalars that have an
+ evolution in the loop are rewritten in function of this single
+ index. This allows the parallelization of the loop. */
+
+static void
+analyze_scalar_evolution_for_all_loop_phi_nodes (VEC(tree,heap) **exit_conditions)
+{
+ unsigned int i;
+ struct chrec_stats stats;
+ tree cond;
+
+ reset_chrecs_counters (&stats);
+
+ for (i = 0; VEC_iterate (tree, *exit_conditions, i, cond); i++)
+ {
+ struct loop *loop;
+ basic_block bb;
+ tree phi, chrec;
+
+ loop = loop_containing_stmt (cond);
+ bb = loop->header;
+
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+ if (is_gimple_reg (PHI_RESULT (phi)))
+ {
+ chrec = instantiate_parameters
+ (loop,
+ analyze_scalar_evolution (loop, PHI_RESULT (phi)));
+
+ if (dump_file && (dump_flags & TDF_STATS))
+ gather_chrec_stats (chrec, &stats);
+ }
+ }
+
+ if (dump_file && (dump_flags & TDF_STATS))
+ dump_chrecs_stats (dump_file, &stats);
+}
+
+/* Callback for htab_traverse, gathers information on chrecs in the
+ hashtable. */
+
+static int
+gather_stats_on_scev_database_1 (void **slot, void *stats)
+{
+ struct scev_info_str *entry = (struct scev_info_str *) *slot;
+
+ gather_chrec_stats (entry->chrec, (struct chrec_stats *) stats);
+
+ return 1;
+}
+
+/* Classify the chrecs of the whole database. */
+
+void
+gather_stats_on_scev_database (void)
+{
+ struct chrec_stats stats;
+
+ if (!dump_file)
+ return;
+
+ reset_chrecs_counters (&stats);
+
+ htab_traverse (scalar_evolution_info, gather_stats_on_scev_database_1,
+ &stats);
+
+ dump_chrecs_stats (dump_file, &stats);
+}
+
+\f
+
+/* Initializer. */
+
+static void
+initialize_scalar_evolutions_analyzer (void)
+{
+ /* The elements below are unique. */
+ if (chrec_dont_know == NULL_TREE)
+ {
+ chrec_not_analyzed_yet = NULL_TREE;
+ chrec_dont_know = make_node (SCEV_NOT_KNOWN);
+ chrec_known = make_node (SCEV_KNOWN);
+ TREE_TYPE (chrec_dont_know) = void_type_node;
+ TREE_TYPE (chrec_known) = void_type_node;
+ }
+}
+
+/* Initialize the analysis of scalar evolutions for LOOPS. */
+
+void
+scev_initialize (void)
+{
+ unsigned i;
+
+ scalar_evolution_info = htab_create (100, hash_scev_info,
+ eq_scev_info, del_scev_info);
+ already_instantiated = BITMAP_ALLOC (NULL);
+
+ initialize_scalar_evolutions_analyzer ();
+
+ for (i = 1; i < current_loops->num; i++)
+ if (current_loops->parray[i])
+ current_loops->parray[i]->nb_iterations = NULL_TREE;
+}
+
+/* Cleans up the information cached by the scalar evolutions analysis. */
+
+void
+scev_reset (void)
+{
+ unsigned i;
+ struct loop *loop;
+
+ if (!scalar_evolution_info || !current_loops)
+ return;
+
+ htab_empty (scalar_evolution_info);
+ for (i = 1; i < current_loops->num; i++)
+ {
+ loop = current_loops->parray[i];
+ if (loop)
+ loop->nb_iterations = NULL_TREE;
+ }
}
/* Checks whether OP behaves as a simple affine iv of LOOP in STMT and returns
- its BASE and STEP if possible. */
+ its base and step in IV if possible. If ALLOW_NONCONSTANT_STEP is true, we
+ want step to be invariant in LOOP. Otherwise we require it to be an
+ integer constant. IV->no_overflow is set to true if we are sure the iv cannot
+ overflow (e.g. because it is computed in signed arithmetics). */
bool
-simple_iv (struct loop *loop ATTRIBUTE_UNUSED, tree stmt ATTRIBUTE_UNUSED,
- tree op ATTRIBUTE_UNUSED, tree *base ATTRIBUTE_UNUSED,
- tree *step ATTRIBUTE_UNUSED)
+simple_iv (struct loop *loop, tree stmt, tree op, affine_iv *iv,
+ bool allow_nonconstant_step)
{
- /* Just a dummy definition for now. */
- return false;
+ basic_block bb = bb_for_stmt (stmt);
+ tree type, ev;
+ bool folded_casts;
+
+ iv->base = NULL_TREE;
+ iv->step = NULL_TREE;
+ iv->no_overflow = false;
+
+ type = TREE_TYPE (op);
+ if (TREE_CODE (type) != INTEGER_TYPE
+ && TREE_CODE (type) != POINTER_TYPE)
+ return false;
+
+ ev = analyze_scalar_evolution_in_loop (loop, bb->loop_father, op,
+ &folded_casts);
+ if (chrec_contains_undetermined (ev))
+ return false;
+
+ if (tree_does_not_contain_chrecs (ev)
+ && !chrec_contains_symbols_defined_in_loop (ev, loop->num))
+ {
+ iv->base = ev;
+ iv->no_overflow = true;
+ return true;
+ }
+
+ if (TREE_CODE (ev) != POLYNOMIAL_CHREC
+ || CHREC_VARIABLE (ev) != (unsigned) loop->num)
+ return false;
+
+ iv->step = CHREC_RIGHT (ev);
+ if (allow_nonconstant_step)
+ {
+ if (tree_contains_chrecs (iv->step, NULL)
+ || chrec_contains_symbols_defined_in_loop (iv->step, loop->num))
+ return false;
+ }
+ else if (TREE_CODE (iv->step) != INTEGER_CST)
+ return false;
+
+ iv->base = CHREC_LEFT (ev);
+ if (tree_contains_chrecs (iv->base, NULL)
+ || chrec_contains_symbols_defined_in_loop (iv->base, loop->num))
+ return false;
+
+ iv->no_overflow = (!folded_casts
+ && !flag_wrapv
+ && !TYPE_UNSIGNED (type));
+ return true;
+}
+
+/* Runs the analysis of scalar evolutions. */
+
+void
+scev_analysis (void)
+{
+ VEC(tree,heap) *exit_conditions;
+
+ exit_conditions = VEC_alloc (tree, heap, 37);
+ select_loops_exit_conditions (&exit_conditions);
+
+ if (dump_file && (dump_flags & TDF_STATS))
+ analyze_scalar_evolution_for_all_loop_phi_nodes (&exit_conditions);
+
+ number_of_iterations_for_all_loops (&exit_conditions);
+ VEC_free (tree, heap, exit_conditions);
+}
+
+/* Finalize the scalar evolution analysis. */
+
+void
+scev_finalize (void)
+{
+ htab_delete (scalar_evolution_info);
+ BITMAP_FREE (already_instantiated);
+}
+
+/* Returns true if EXPR looks expensive. */
+
+static bool
+expression_expensive_p (tree expr)
+{
+ return force_expr_to_var_cost (expr) >= target_spill_cost;
+}
+
+/* Replace ssa names for that scev can prove they are constant by the
+ appropriate constants. Also perform final value replacement in loops,
+ in case the replacement expressions are cheap.
+
+ We only consider SSA names defined by phi nodes; rest is left to the
+ ordinary constant propagation pass. */
+
+unsigned int
+scev_const_prop (void)
+{
+ basic_block bb;
+ tree name, phi, next_phi, type, ev;
+ struct loop *loop, *ex_loop;
+ bitmap ssa_names_to_remove = NULL;
+ unsigned i;
+
+ if (!current_loops)
+ return 0;
+
+ FOR_EACH_BB (bb)
+ {
+ loop = bb->loop_father;
+
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+ {
+ name = PHI_RESULT (phi);
+
+ if (!is_gimple_reg (name))
+ continue;
+
+ type = TREE_TYPE (name);
+
+ if (!POINTER_TYPE_P (type)
+ && !INTEGRAL_TYPE_P (type))
+ continue;
+
+ ev = resolve_mixers (loop, analyze_scalar_evolution (loop, name));
+ if (!is_gimple_min_invariant (ev)
+ || !may_propagate_copy (name, ev))
+ continue;
+
+ /* Replace the uses of the name. */
+ if (name != ev)
+ replace_uses_by (name, ev);
+
+ if (!ssa_names_to_remove)
+ ssa_names_to_remove = BITMAP_ALLOC (NULL);
+ bitmap_set_bit (ssa_names_to_remove, SSA_NAME_VERSION (name));
+ }
+ }
+
+ /* Remove the ssa names that were replaced by constants. We do not remove them
+ directly in the previous cycle, since this invalidates scev cache. */
+ if (ssa_names_to_remove)
+ {
+ bitmap_iterator bi;
+ unsigned i;
+
+ EXECUTE_IF_SET_IN_BITMAP (ssa_names_to_remove, 0, i, bi)
+ {
+ name = ssa_name (i);
+ phi = SSA_NAME_DEF_STMT (name);
+
+ gcc_assert (TREE_CODE (phi) == PHI_NODE);
+ remove_phi_node (phi, NULL);
+ }
+
+ BITMAP_FREE (ssa_names_to_remove);
+ scev_reset ();
+ }
+
+ /* Now the regular final value replacement. */
+ for (i = current_loops->num - 1; i > 0; i--)
+ {
+ edge exit;
+ tree def, rslt, ass, niter;
+ block_stmt_iterator bsi;
+
+ loop = current_loops->parray[i];
+ if (!loop)
+ continue;
+
+ /* If we do not know exact number of iterations of the loop, we cannot
+ replace the final value. */
+ exit = single_exit (loop);
+ if (!exit)
+ continue;
+
+ niter = number_of_iterations_in_loop (loop);
+ if (niter == chrec_dont_know
+ /* If computing the number of iterations is expensive, it may be
+ better not to introduce computations involving it. */
+ || expression_expensive_p (niter))
+ continue;
+
+ /* Ensure that it is possible to insert new statements somewhere. */
+ if (!single_pred_p (exit->dest))
+ split_loop_exit_edge (exit);
+ tree_block_label (exit->dest);
+ bsi = bsi_after_labels (exit->dest);
+
+ ex_loop = superloop_at_depth (loop, exit->dest->loop_father->depth + 1);
+
+ for (phi = phi_nodes (exit->dest); phi; phi = next_phi)
+ {
+ next_phi = PHI_CHAIN (phi);
+ rslt = PHI_RESULT (phi);
+ def = PHI_ARG_DEF_FROM_EDGE (phi, exit);
+ if (!is_gimple_reg (def))
+ continue;
+
+ if (!POINTER_TYPE_P (TREE_TYPE (def))
+ && !INTEGRAL_TYPE_P (TREE_TYPE (def)))
+ continue;
+
+ def = analyze_scalar_evolution_in_loop (ex_loop, loop, def, NULL);
+ def = compute_overall_effect_of_inner_loop (ex_loop, def);
+ if (!tree_does_not_contain_chrecs (def)
+ || chrec_contains_symbols_defined_in_loop (def, ex_loop->num)
+ /* Moving the computation from the loop may prolong life range
+ of some ssa names, which may cause problems if they appear
+ on abnormal edges. */
+ || contains_abnormal_ssa_name_p (def))
+ continue;
+
+ /* Eliminate the phi node and replace it by a computation outside
+ the loop. */
+ def = unshare_expr (def);
+ SET_PHI_RESULT (phi, NULL_TREE);
+ remove_phi_node (phi, NULL_TREE);
+
+ ass = build2 (GIMPLE_MODIFY_STMT, void_type_node, rslt, NULL_TREE);
+ SSA_NAME_DEF_STMT (rslt) = ass;
+ {
+ block_stmt_iterator dest = bsi;
+ bsi_insert_before (&dest, ass, BSI_NEW_STMT);
+ def = force_gimple_operand_bsi (&dest, def, false, NULL_TREE);
+ }
+ GIMPLE_STMT_OPERAND (ass, 1) = def;
+ update_stmt (ass);
+ }
+ }
+ return 0;
}
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