| /* Scalar evolution detector. |
| Copyright (C) 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. |
| Contributed by Sebastian Pop <s.pop@laposte.net> |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify it under |
| the terms of the GNU General Public License as published by the Free |
| Software Foundation; either version 2, or (at your option) any later |
| version. |
| |
| GCC is distributed in the hope that it will be useful, but WITHOUT ANY |
| WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| for more details. |
| |
| 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, 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 MODIFY_EXPR: 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 "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 "tree-flow.h" |
| #include "tree-dump.h" |
| #include "timevar.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; |
| |
| |
| /* 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; |
| } |
| |
| |
| |
| /* 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 = loop->single_exit; |
| |
| |
| 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 (loop->single_exit) |
| { |
| 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 (struct loops *loops, |
| VEC(tree,heap) **exit_conditions) |
| { |
| struct loop *function_body = loops->parray[0]; |
| |
| get_exit_conditions_rec (function_body->inner, exit_conditions); |
| } |
| |
| |
| /* 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 MODIFY_EXPR: |
| return follow_ssa_edge_in_rhs (loop, def, |
| TREE_OPERAND (def, 1), |
| halting_phi, |
| evolution_of_loop, limit); |
| |
| default: |
| /* At this level of abstraction, the program is just a set |
| of MODIFY_EXPRs and PHI_NODEs. In principle there is no |
| other node to be handled. */ |
| return t_false; |
| } |
| } |
| |
| |
| |
| /* 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 modify_expr OPND1. If we didn't |
| analyze this node before, follow the definitions until ending |
| either on an analyzed modify_expr, 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_expr (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; |
| } |
| |
| |
| |
| /* 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) != MODIFY_EXPR) |
| continue; |
| |
| rhs = TREE_OPERAND (stmt, 1); |
| if (!COMPARISON_CLASS_P (rhs)) |
| continue; |
| |
| if (TREE_OPERAND (stmt, 0) == ptr |
| || TREE_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_expr (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 MODIFY_EXPR: |
| res = interpret_rhs_modify_expr (loop, def, TREE_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 = loop->single_exit; |
| 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, |
| tree 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 = loop->single_exit; |
| 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); |
| } |
| } |
| |
| |
| |
| /* 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); |
| } |
| |
| |
| |
| /* 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 (struct loops *loops) |
| { |
| unsigned i; |
| current_loops = loops; |
| |
| 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 < loops->num; i++) |
| if (loops->parray[i]) |
| 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 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, tree stmt, tree op, affine_iv *iv, |
| bool allow_nonconstant_step) |
| { |
| 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 && TYPE_OVERFLOW_UNDEFINED (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 (current_loops, &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 = loop->single_exit; |
| 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 (MODIFY_EXPR, 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); |
| } |
| TREE_OPERAND (ass, 1) = def; |
| update_stmt (ass); |
| } |
| } |
| return 0; |
| } |