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[/] [scarts/] [trunk/] [toolchain/] [scarts-gcc/] [gcc-4.1.1/] [gcc/] [tree-ssa-structalias.c] - Rev 20
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/* Tree based points-to analysis Copyright (C) 2005 Free Software Foundation, Inc. Contributed by Daniel Berlin <dberlin@dberlin.org> This file is part of GCC. GCC is free software; you can redistribute it and/or modify under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, 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; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "ggc.h" #include "obstack.h" #include "bitmap.h" #include "flags.h" #include "rtl.h" #include "tm_p.h" #include "hard-reg-set.h" #include "basic-block.h" #include "output.h" #include "errors.h" #include "diagnostic.h" #include "tree.h" #include "c-common.h" #include "tree-flow.h" #include "tree-inline.h" #include "varray.h" #include "c-tree.h" #include "tree-gimple.h" #include "hashtab.h" #include "function.h" #include "cgraph.h" #include "tree-pass.h" #include "timevar.h" #include "alloc-pool.h" #include "splay-tree.h" #include "tree-ssa-structalias.h" #include "params.h" /* The idea behind this analyzer is to generate set constraints from the program, then solve the resulting constraints in order to generate the points-to sets. Set constraints are a way of modeling program analysis problems that involve sets. They consist of an inclusion constraint language, describing the variables (each variable is a set) and operations that are involved on the variables, and a set of rules that derive facts from these operations. To solve a system of set constraints, you derive all possible facts under the rules, which gives you the correct sets as a consequence. See "Efficient Field-sensitive pointer analysis for C" by "David J. Pearce and Paul H. J. Kelly and Chris Hankin, at http://citeseer.ist.psu.edu/pearce04efficient.html Also see "Ultra-fast Aliasing Analysis using CLA: A Million Lines of C Code in a Second" by ""Nevin Heintze and Olivier Tardieu" at http://citeseer.ist.psu.edu/heintze01ultrafast.html There are three types of constraint expressions, DEREF, ADDRESSOF, and SCALAR. Each constraint expression consists of a constraint type, a variable, and an offset. SCALAR is a constraint expression type used to represent x, whether it appears on the LHS or the RHS of a statement. DEREF is a constraint expression type used to represent *x, whether it appears on the LHS or the RHS of a statement. ADDRESSOF is a constraint expression used to represent &x, whether it appears on the LHS or the RHS of a statement. Each pointer variable in the program is assigned an integer id, and each field of a structure variable is assigned an integer id as well. Structure variables are linked to their list of fields through a "next field" in each variable that points to the next field in offset order. Each variable for a structure field has 1. "size", that tells the size in bits of that field. 2. "fullsize, that tells the size in bits of the entire structure. 3. "offset", that tells the offset in bits from the beginning of the structure to this field. Thus, struct f { int a; int b; } foo; int *bar; looks like foo.a -> id 1, size 32, offset 0, fullsize 64, next foo.b foo.b -> id 2, size 32, offset 32, fullsize 64, next NULL bar -> id 3, size 32, offset 0, fullsize 32, next NULL In order to solve the system of set constraints, the following is done: 1. Each constraint variable x has a solution set associated with it, Sol(x). 2. Constraints are separated into direct, copy, and complex. Direct constraints are ADDRESSOF constraints that require no extra processing, such as P = &Q Copy constraints are those of the form P = Q. Complex constraints are all the constraints involving dereferences. 3. All direct constraints of the form P = &Q are processed, such that Q is added to Sol(P) 4. All complex constraints for a given constraint variable are stored in a linked list attached to that variable's node. 5. A directed graph is built out of the copy constraints. Each constraint variable is a node in the graph, and an edge from Q to P is added for each copy constraint of the form P = Q 6. The graph is then walked, and solution sets are propagated along the copy edges, such that an edge from Q to P causes Sol(P) <- Sol(P) union Sol(Q). 7. As we visit each node, all complex constraints associated with that node are processed by adding appropriate copy edges to the graph, or the appropriate variables to the solution set. 8. The process of walking the graph is iterated until no solution sets change. Prior to walking the graph in steps 6 and 7, We perform static cycle elimination on the constraint graph, as well as off-line variable substitution. TODO: Adding offsets to pointer-to-structures can be handled (IE not punted on and turned into anything), but isn't. You can just see what offset inside the pointed-to struct it's going to access. TODO: Constant bounded arrays can be handled as if they were structs of the same number of elements. TODO: Modeling heap and incoming pointers becomes much better if we add fields to them as we discover them, which we could do. TODO: We could handle unions, but to be honest, it's probably not worth the pain or slowdown. */ static GTY ((if_marked ("tree_map_marked_p"), param_is (struct tree_map))) htab_t heapvar_for_stmt; static bool use_field_sensitive = true; static unsigned int create_variable_info_for (tree, const char *); static struct constraint_expr get_constraint_for (tree, bool *); static void build_constraint_graph (void); static bitmap_obstack ptabitmap_obstack; static bitmap_obstack iteration_obstack; DEF_VEC_P(constraint_t); DEF_VEC_ALLOC_P(constraint_t,heap); static struct constraint_stats { unsigned int total_vars; unsigned int collapsed_vars; unsigned int unified_vars_static; unsigned int unified_vars_dynamic; unsigned int iterations; } stats; struct variable_info { /* ID of this variable */ unsigned int id; /* Name of this variable */ const char *name; /* Tree that this variable is associated with. */ tree decl; /* Offset of this variable, in bits, from the base variable */ unsigned HOST_WIDE_INT offset; /* Size of the variable, in bits. */ unsigned HOST_WIDE_INT size; /* Full size of the base variable, in bits. */ unsigned HOST_WIDE_INT fullsize; /* A link to the variable for the next field in this structure. */ struct variable_info *next; /* Node in the graph that represents the constraints and points-to solution for the variable. */ unsigned int node; /* True if the address of this variable is taken. Needed for variable substitution. */ unsigned int address_taken:1; /* True if this variable is the target of a dereference. Needed for variable substitution. */ unsigned int indirect_target:1; /* True if this is a variable created by the constraint analysis, such as heap variables and constraints we had to break up. */ unsigned int is_artificial_var:1; /* True if this is a special variable whose solution set should not be changed. */ unsigned int is_special_var:1; /* True for variables whose size is not known or variable. */ unsigned int is_unknown_size_var:1; /* True for variables that have unions somewhere in them. */ unsigned int has_union:1; /* True if this is a heap variable. */ unsigned int is_heap_var:1; /* Points-to set for this variable. */ bitmap solution; /* Variable ids represented by this node. */ bitmap variables; /* Vector of complex constraints for this node. Complex constraints are those involving dereferences. */ VEC(constraint_t,heap) *complex; /* Variable id this was collapsed to due to type unsafety. This should be unused completely after build_constraint_graph, or something is broken. */ struct variable_info *collapsed_to; }; typedef struct variable_info *varinfo_t; static varinfo_t first_vi_for_offset (varinfo_t, unsigned HOST_WIDE_INT); /* Pool of variable info structures. */ static alloc_pool variable_info_pool; DEF_VEC_P(varinfo_t); DEF_VEC_ALLOC_P(varinfo_t, heap); /* Table of variable info structures for constraint variables. Indexed directly by variable info id. */ static VEC(varinfo_t,heap) *varmap; /* Return the varmap element N */ static inline varinfo_t get_varinfo (unsigned int n) { return VEC_index(varinfo_t, varmap, n); } /* Return the varmap element N, following the collapsed_to link. */ static inline varinfo_t get_varinfo_fc (unsigned int n) { varinfo_t v = VEC_index(varinfo_t, varmap, n); if (v->collapsed_to) return v->collapsed_to; return v; } /* Variable that represents the unknown pointer. */ static varinfo_t var_anything; static tree anything_tree; static unsigned int anything_id; /* Variable that represents the NULL pointer. */ static varinfo_t var_nothing; static tree nothing_tree; static unsigned int nothing_id; /* Variable that represents read only memory. */ static varinfo_t var_readonly; static tree readonly_tree; static unsigned int readonly_id; /* Variable that represents integers. This is used for when people do things like &0->a.b. */ static varinfo_t var_integer; static tree integer_tree; static unsigned int integer_id; /* Variable that represents arbitrary offsets into an object. Used to represent pointer arithmetic, which may not legally escape the bounds of an object. */ static varinfo_t var_anyoffset; static tree anyoffset_tree; static unsigned int anyoffset_id; /* Lookup a heap var for FROM, and return it if we find one. */ static tree heapvar_lookup (tree from) { struct tree_map *h, in; in.from = from; h = htab_find_with_hash (heapvar_for_stmt, &in, htab_hash_pointer (from)); if (h) return h->to; return NULL_TREE; } /* Insert a mapping FROM->TO in the heap var for statement hashtable. */ static void heapvar_insert (tree from, tree to) { struct tree_map *h; void **loc; h = ggc_alloc (sizeof (struct tree_map)); h->hash = htab_hash_pointer (from); h->from = from; h->to = to; loc = htab_find_slot_with_hash (heapvar_for_stmt, h, h->hash, INSERT); *(struct tree_map **) loc = h; } /* Return a new variable info structure consisting for a variable named NAME, and using constraint graph node NODE. */ static varinfo_t new_var_info (tree t, unsigned int id, const char *name, unsigned int node) { varinfo_t ret = pool_alloc (variable_info_pool); ret->id = id; ret->name = name; ret->decl = t; ret->node = node; ret->address_taken = false; ret->indirect_target = false; ret->is_artificial_var = false; ret->is_heap_var = false; ret->is_special_var = false; ret->is_unknown_size_var = false; ret->has_union = false; ret->solution = BITMAP_ALLOC (&ptabitmap_obstack); bitmap_clear (ret->solution); ret->variables = BITMAP_ALLOC (&ptabitmap_obstack); bitmap_clear (ret->variables); ret->complex = NULL; ret->next = NULL; ret->collapsed_to = NULL; return ret; } typedef enum {SCALAR, DEREF, ADDRESSOF} constraint_expr_type; /* An expression that appears in a constraint. */ struct constraint_expr { /* Constraint type. */ constraint_expr_type type; /* Variable we are referring to in the constraint. */ unsigned int var; /* Offset, in bits, of this constraint from the beginning of variables it ends up referring to. IOW, in a deref constraint, we would deref, get the result set, then add OFFSET to each member. */ unsigned HOST_WIDE_INT offset; }; static struct constraint_expr do_deref (struct constraint_expr); /* Our set constraints are made up of two constraint expressions, one LHS, and one RHS. As described in the introduction, our set constraints each represent an operation between set valued variables. */ struct constraint { struct constraint_expr lhs; struct constraint_expr rhs; }; /* List of constraints that we use to build the constraint graph from. */ static VEC(constraint_t,heap) *constraints; static alloc_pool constraint_pool; /* An edge in the constraint graph. We technically have no use for the src, since it will always be the same node that we are indexing into the pred/succ arrays with, but it's nice for checking purposes. The edges are weighted, with a bit set in weights for each edge from src to dest with that weight. */ struct constraint_edge { unsigned int src; unsigned int dest; bitmap weights; }; typedef struct constraint_edge *constraint_edge_t; static alloc_pool constraint_edge_pool; /* Return a new constraint edge from SRC to DEST. */ static constraint_edge_t new_constraint_edge (unsigned int src, unsigned int dest) { constraint_edge_t ret = pool_alloc (constraint_edge_pool); ret->src = src; ret->dest = dest; ret->weights = NULL; return ret; } DEF_VEC_P(constraint_edge_t); DEF_VEC_ALLOC_P(constraint_edge_t,heap); /* The constraint graph is simply a set of adjacency vectors, one per variable. succs[x] is the vector of successors for variable x, and preds[x] is the vector of predecessors for variable x. IOW, all edges are "forward" edges, which is not like our CFG. So remember that preds[x]->src == x, and succs[x]->src == x. */ struct constraint_graph { VEC(constraint_edge_t,heap) **succs; VEC(constraint_edge_t,heap) **preds; }; typedef struct constraint_graph *constraint_graph_t; static constraint_graph_t graph; /* Create a new constraint consisting of LHS and RHS expressions. */ static constraint_t new_constraint (const struct constraint_expr lhs, const struct constraint_expr rhs) { constraint_t ret = pool_alloc (constraint_pool); ret->lhs = lhs; ret->rhs = rhs; return ret; } /* Print out constraint C to FILE. */ void dump_constraint (FILE *file, constraint_t c) { if (c->lhs.type == ADDRESSOF) fprintf (file, "&"); else if (c->lhs.type == DEREF) fprintf (file, "*"); fprintf (file, "%s", get_varinfo_fc (c->lhs.var)->name); if (c->lhs.offset != 0) fprintf (file, " + " HOST_WIDE_INT_PRINT_DEC, c->lhs.offset); fprintf (file, " = "); if (c->rhs.type == ADDRESSOF) fprintf (file, "&"); else if (c->rhs.type == DEREF) fprintf (file, "*"); fprintf (file, "%s", get_varinfo_fc (c->rhs.var)->name); if (c->rhs.offset != 0) fprintf (file, " + " HOST_WIDE_INT_PRINT_DEC, c->rhs.offset); fprintf (file, "\n"); } /* Print out constraint C to stderr. */ void debug_constraint (constraint_t c) { dump_constraint (stderr, c); } /* Print out all constraints to FILE */ void dump_constraints (FILE *file) { int i; constraint_t c; for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++) dump_constraint (file, c); } /* Print out all constraints to stderr. */ void debug_constraints (void) { dump_constraints (stderr); } /* SOLVER FUNCTIONS The solver is a simple worklist solver, that works on the following algorithm: sbitmap changed_nodes = all ones; changed_count = number of nodes; For each node that was already collapsed: changed_count--; while (changed_count > 0) { compute topological ordering for constraint graph find and collapse cycles in the constraint graph (updating changed if necessary) for each node (n) in the graph in topological order: changed_count--; Process each complex constraint associated with the node, updating changed if necessary. For each outgoing edge from n, propagate the solution from n to the destination of the edge, updating changed as necessary. } */ /* Return true if two constraint expressions A and B are equal. */ static bool constraint_expr_equal (struct constraint_expr a, struct constraint_expr b) { return a.type == b.type && a.var == b.var && a.offset == b.offset; } /* Return true if constraint expression A is less than constraint expression B. This is just arbitrary, but consistent, in order to give them an ordering. */ static bool constraint_expr_less (struct constraint_expr a, struct constraint_expr b) { if (a.type == b.type) { if (a.var == b.var) return a.offset < b.offset; else return a.var < b.var; } else return a.type < b.type; } /* Return true if constraint A is less than constraint B. This is just arbitrary, but consistent, in order to give them an ordering. */ static bool constraint_less (const constraint_t a, const constraint_t b) { if (constraint_expr_less (a->lhs, b->lhs)) return true; else if (constraint_expr_less (b->lhs, a->lhs)) return false; else return constraint_expr_less (a->rhs, b->rhs); } /* Return true if two constraints A and B are equal. */ static bool constraint_equal (struct constraint a, struct constraint b) { return constraint_expr_equal (a.lhs, b.lhs) && constraint_expr_equal (a.rhs, b.rhs); } /* Find a constraint LOOKFOR in the sorted constraint vector VEC */ static constraint_t constraint_vec_find (VEC(constraint_t,heap) *vec, struct constraint lookfor) { unsigned int place; constraint_t found; if (vec == NULL) return NULL; place = VEC_lower_bound (constraint_t, vec, &lookfor, constraint_less); if (place >= VEC_length (constraint_t, vec)) return NULL; found = VEC_index (constraint_t, vec, place); if (!constraint_equal (*found, lookfor)) return NULL; return found; } /* Union two constraint vectors, TO and FROM. Put the result in TO. */ static void constraint_set_union (VEC(constraint_t,heap) **to, VEC(constraint_t,heap) **from) { int i; constraint_t c; for (i = 0; VEC_iterate (constraint_t, *from, i, c); i++) { if (constraint_vec_find (*to, *c) == NULL) { unsigned int place = VEC_lower_bound (constraint_t, *to, c, constraint_less); VEC_safe_insert (constraint_t, heap, *to, place, c); } } } /* Take a solution set SET, add OFFSET to each member of the set, and overwrite SET with the result when done. */ static void solution_set_add (bitmap set, unsigned HOST_WIDE_INT offset) { bitmap result = BITMAP_ALLOC (&iteration_obstack); unsigned int i; bitmap_iterator bi; EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi) { /* If this is a properly sized variable, only add offset if it's less than end. Otherwise, it is globbed to a single variable. */ if ((get_varinfo (i)->offset + offset) < get_varinfo (i)->fullsize) { unsigned HOST_WIDE_INT fieldoffset = get_varinfo (i)->offset + offset; varinfo_t v = first_vi_for_offset (get_varinfo (i), fieldoffset); if (!v) continue; bitmap_set_bit (result, v->id); } else if (get_varinfo (i)->is_artificial_var || get_varinfo (i)->has_union || get_varinfo (i)->is_unknown_size_var) { bitmap_set_bit (result, i); } } bitmap_copy (set, result); BITMAP_FREE (result); } /* Union solution sets TO and FROM, and add INC to each member of FROM in the process. */ static bool set_union_with_increment (bitmap to, bitmap from, unsigned HOST_WIDE_INT inc) { if (inc == 0) return bitmap_ior_into (to, from); else { bitmap tmp; bool res; tmp = BITMAP_ALLOC (&iteration_obstack); bitmap_copy (tmp, from); solution_set_add (tmp, inc); res = bitmap_ior_into (to, tmp); BITMAP_FREE (tmp); return res; } } /* Insert constraint C into the list of complex constraints for VAR. */ static void insert_into_complex (unsigned int var, constraint_t c) { varinfo_t vi = get_varinfo (var); unsigned int place = VEC_lower_bound (constraint_t, vi->complex, c, constraint_less); VEC_safe_insert (constraint_t, heap, vi->complex, place, c); } /* Compare two constraint edges A and B, return true if they are equal. */ static bool constraint_edge_equal (struct constraint_edge a, struct constraint_edge b) { return a.src == b.src && a.dest == b.dest; } /* Compare two constraint edges, return true if A is less than B */ static bool constraint_edge_less (const constraint_edge_t a, const constraint_edge_t b) { if (a->dest < b->dest) return true; else if (a->dest == b->dest) return a->src < b->src; else return false; } /* Find the constraint edge that matches LOOKFOR, in VEC. Return the edge, if found, NULL otherwise. */ static constraint_edge_t constraint_edge_vec_find (VEC(constraint_edge_t,heap) *vec, struct constraint_edge lookfor) { unsigned int place; constraint_edge_t edge; place = VEC_lower_bound (constraint_edge_t, vec, &lookfor, constraint_edge_less); edge = VEC_index (constraint_edge_t, vec, place); if (!constraint_edge_equal (*edge, lookfor)) return NULL; return edge; } /* Condense two variable nodes into a single variable node, by moving all associated info from SRC to TO. */ static void condense_varmap_nodes (unsigned int to, unsigned int src) { varinfo_t tovi = get_varinfo (to); varinfo_t srcvi = get_varinfo (src); unsigned int i; constraint_t c; bitmap_iterator bi; /* the src node, and all its variables, are now the to node. */ srcvi->node = to; EXECUTE_IF_SET_IN_BITMAP (srcvi->variables, 0, i, bi) get_varinfo (i)->node = to; /* Merge the src node variables and the to node variables. */ bitmap_set_bit (tovi->variables, src); bitmap_ior_into (tovi->variables, srcvi->variables); bitmap_clear (srcvi->variables); /* Move all complex constraints from src node into to node */ for (i = 0; VEC_iterate (constraint_t, srcvi->complex, i, c); i++) { /* In complex constraints for node src, we may have either a = *src, and *src = a. */ if (c->rhs.type == DEREF) c->rhs.var = to; else c->lhs.var = to; } constraint_set_union (&tovi->complex, &srcvi->complex); VEC_free (constraint_t, heap, srcvi->complex); srcvi->complex = NULL; } /* Erase EDGE from GRAPH. This routine only handles self-edges (e.g. an edge from a to a). */ static void erase_graph_self_edge (constraint_graph_t graph, struct constraint_edge edge) { VEC(constraint_edge_t,heap) *predvec = graph->preds[edge.src]; VEC(constraint_edge_t,heap) *succvec = graph->succs[edge.dest]; unsigned int place; gcc_assert (edge.src == edge.dest); /* Remove from the successors. */ place = VEC_lower_bound (constraint_edge_t, succvec, &edge, constraint_edge_less); /* Make sure we found the edge. */ #ifdef ENABLE_CHECKING { constraint_edge_t tmp = VEC_index (constraint_edge_t, succvec, place); gcc_assert (constraint_edge_equal (*tmp, edge)); } #endif VEC_ordered_remove (constraint_edge_t, succvec, place); /* Remove from the predecessors. */ place = VEC_lower_bound (constraint_edge_t, predvec, &edge, constraint_edge_less); /* Make sure we found the edge. */ #ifdef ENABLE_CHECKING { constraint_edge_t tmp = VEC_index (constraint_edge_t, predvec, place); gcc_assert (constraint_edge_equal (*tmp, edge)); } #endif VEC_ordered_remove (constraint_edge_t, predvec, place); } /* Remove edges involving NODE from GRAPH. */ static void clear_edges_for_node (constraint_graph_t graph, unsigned int node) { VEC(constraint_edge_t,heap) *succvec = graph->succs[node]; VEC(constraint_edge_t,heap) *predvec = graph->preds[node]; constraint_edge_t c; int i; /* Walk the successors, erase the associated preds. */ for (i = 0; VEC_iterate (constraint_edge_t, succvec, i, c); i++) if (c->dest != node) { unsigned int place; struct constraint_edge lookfor; lookfor.src = c->dest; lookfor.dest = node; place = VEC_lower_bound (constraint_edge_t, graph->preds[c->dest], &lookfor, constraint_edge_less); VEC_ordered_remove (constraint_edge_t, graph->preds[c->dest], place); } /* Walk the preds, erase the associated succs. */ for (i =0; VEC_iterate (constraint_edge_t, predvec, i, c); i++) if (c->dest != node) { unsigned int place; struct constraint_edge lookfor; lookfor.src = c->dest; lookfor.dest = node; place = VEC_lower_bound (constraint_edge_t, graph->succs[c->dest], &lookfor, constraint_edge_less); VEC_ordered_remove (constraint_edge_t, graph->succs[c->dest], place); } VEC_free (constraint_edge_t, heap, graph->preds[node]); VEC_free (constraint_edge_t, heap, graph->succs[node]); graph->preds[node] = NULL; graph->succs[node] = NULL; } static bool edge_added = false; /* Add edge NEWE to the graph. */ static bool add_graph_edge (constraint_graph_t graph, struct constraint_edge newe) { unsigned int place; unsigned int src = newe.src; unsigned int dest = newe.dest; VEC(constraint_edge_t,heap) *vec; vec = graph->preds[src]; place = VEC_lower_bound (constraint_edge_t, vec, &newe, constraint_edge_less); if (place == VEC_length (constraint_edge_t, vec) || VEC_index (constraint_edge_t, vec, place)->dest != dest) { constraint_edge_t edge = new_constraint_edge (src, dest); bitmap weightbitmap; weightbitmap = BITMAP_ALLOC (&ptabitmap_obstack); edge->weights = weightbitmap; VEC_safe_insert (constraint_edge_t, heap, graph->preds[edge->src], place, edge); edge = new_constraint_edge (dest, src); edge->weights = weightbitmap; place = VEC_lower_bound (constraint_edge_t, graph->succs[edge->src], edge, constraint_edge_less); VEC_safe_insert (constraint_edge_t, heap, graph->succs[edge->src], place, edge); edge_added = true; return true; } else return false; } /* Return the bitmap representing the weights of edge LOOKFOR */ static bitmap get_graph_weights (constraint_graph_t graph, struct constraint_edge lookfor) { constraint_edge_t edge; unsigned int src = lookfor.src; VEC(constraint_edge_t,heap) *vec; vec = graph->preds[src]; edge = constraint_edge_vec_find (vec, lookfor); gcc_assert (edge != NULL); return edge->weights; } /* Merge GRAPH nodes FROM and TO into node TO. */ static void merge_graph_nodes (constraint_graph_t graph, unsigned int to, unsigned int from) { VEC(constraint_edge_t,heap) *succvec = graph->succs[from]; VEC(constraint_edge_t,heap) *predvec = graph->preds[from]; int i; constraint_edge_t c; /* Merge all the predecessor edges. */ for (i = 0; VEC_iterate (constraint_edge_t, predvec, i, c); i++) { unsigned int d = c->dest; struct constraint_edge olde; struct constraint_edge newe; bitmap temp; bitmap weights; if (c->dest == from) d = to; newe.src = to; newe.dest = d; add_graph_edge (graph, newe); olde.src = from; olde.dest = c->dest; olde.weights = NULL; temp = get_graph_weights (graph, olde); weights = get_graph_weights (graph, newe); bitmap_ior_into (weights, temp); } /* Merge all the successor edges. */ for (i = 0; VEC_iterate (constraint_edge_t, succvec, i, c); i++) { unsigned int d = c->dest; struct constraint_edge olde; struct constraint_edge newe; bitmap temp; bitmap weights; if (c->dest == from) d = to; newe.src = d; newe.dest = to; add_graph_edge (graph, newe); olde.src = c->dest; olde.dest = from; olde.weights = NULL; temp = get_graph_weights (graph, olde); weights = get_graph_weights (graph, newe); bitmap_ior_into (weights, temp); } clear_edges_for_node (graph, from); } /* Add a graph edge to GRAPH, going from TO to FROM, with WEIGHT, if it doesn't exist in the graph already. Return false if the edge already existed, true otherwise. */ static bool int_add_graph_edge (constraint_graph_t graph, unsigned int to, unsigned int from, unsigned HOST_WIDE_INT weight) { if (to == from && weight == 0) { return false; } else { bool r; struct constraint_edge edge; edge.src = to; edge.dest = from; edge.weights = NULL; r = add_graph_edge (graph, edge); r |= !bitmap_bit_p (get_graph_weights (graph, edge), weight); bitmap_set_bit (get_graph_weights (graph, edge), weight); return r; } } /* Return true if LOOKFOR is an existing graph edge. */ static bool valid_graph_edge (constraint_graph_t graph, struct constraint_edge lookfor) { return constraint_edge_vec_find (graph->preds[lookfor.src], lookfor) != NULL; } /* Build the constraint graph. */ static void build_constraint_graph (void) { int i = 0; constraint_t c; graph = xmalloc (sizeof (struct constraint_graph)); graph->succs = xcalloc (VEC_length (varinfo_t, varmap), sizeof (*graph->succs)); graph->preds = xcalloc (VEC_length (varinfo_t, varmap), sizeof (*graph->preds)); for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++) { struct constraint_expr lhs = c->lhs; struct constraint_expr rhs = c->rhs; unsigned int lhsvar = get_varinfo_fc (lhs.var)->id; unsigned int rhsvar = get_varinfo_fc (rhs.var)->id; if (lhs.type == DEREF) { /* *x = y or *x = &y (complex) */ if (rhs.type == ADDRESSOF || rhsvar > anything_id) insert_into_complex (lhsvar, c); } else if (rhs.type == DEREF) { /* !special var= *y */ if (!(get_varinfo (lhsvar)->is_special_var)) insert_into_complex (rhsvar, c); } else if (rhs.type == ADDRESSOF) { /* x = &y */ bitmap_set_bit (get_varinfo (lhsvar)->solution, rhsvar); } else if (lhsvar > anything_id) { /* Ignore 0 weighted self edges, as they can't possibly contribute anything */ if (lhsvar != rhsvar || rhs.offset != 0 || lhs.offset != 0) { struct constraint_edge edge; edge.src = lhsvar; edge.dest = rhsvar; /* x = y (simple) */ add_graph_edge (graph, edge); bitmap_set_bit (get_graph_weights (graph, edge), rhs.offset); } } } } /* Changed variables on the last iteration. */ static unsigned int changed_count; static sbitmap changed; DEF_VEC_I(unsigned); DEF_VEC_ALLOC_I(unsigned,heap); /* Strongly Connected Component visitation info. */ struct scc_info { sbitmap visited; sbitmap in_component; int current_index; unsigned int *visited_index; VEC(unsigned,heap) *scc_stack; VEC(unsigned,heap) *unification_queue; }; /* Recursive routine to find strongly connected components in GRAPH. SI is the SCC info to store the information in, and N is the id of current graph node we are processing. This is Tarjan's strongly connected component finding algorithm, as modified by Nuutila to keep only non-root nodes on the stack. The algorithm can be found in "On finding the strongly connected connected components in a directed graph" by Esko Nuutila and Eljas Soisalon-Soininen, in Information Processing Letters volume 49, number 1, pages 9-14. */ static void scc_visit (constraint_graph_t graph, struct scc_info *si, unsigned int n) { constraint_edge_t c; int i; gcc_assert (get_varinfo (n)->node == n); SET_BIT (si->visited, n); RESET_BIT (si->in_component, n); si->visited_index[n] = si->current_index ++; /* Visit all the successors. */ for (i = 0; VEC_iterate (constraint_edge_t, graph->succs[n], i, c); i++) { /* We only want to find and collapse the zero weight edges. */ if (bitmap_bit_p (c->weights, 0)) { unsigned int w = c->dest; if (!TEST_BIT (si->visited, w)) scc_visit (graph, si, w); if (!TEST_BIT (si->in_component, w)) { unsigned int t = get_varinfo (w)->node; unsigned int nnode = get_varinfo (n)->node; if (si->visited_index[t] < si->visited_index[nnode]) get_varinfo (n)->node = t; } } } /* See if any components have been identified. */ if (get_varinfo (n)->node == n) { unsigned int t = si->visited_index[n]; SET_BIT (si->in_component, n); while (VEC_length (unsigned, si->scc_stack) != 0 && t < si->visited_index[VEC_last (unsigned, si->scc_stack)]) { unsigned int w = VEC_pop (unsigned, si->scc_stack); get_varinfo (w)->node = n; SET_BIT (si->in_component, w); /* Mark this node for collapsing. */ VEC_safe_push (unsigned, heap, si->unification_queue, w); } } else VEC_safe_push (unsigned, heap, si->scc_stack, n); } /* Collapse two variables into one variable. */ static void collapse_nodes (constraint_graph_t graph, unsigned int to, unsigned int from) { bitmap tosol, fromsol; struct constraint_edge edge; condense_varmap_nodes (to, from); tosol = get_varinfo (to)->solution; fromsol = get_varinfo (from)->solution; bitmap_ior_into (tosol, fromsol); merge_graph_nodes (graph, to, from); edge.src = to; edge.dest = to; edge.weights = NULL; if (valid_graph_edge (graph, edge)) { bitmap weights = get_graph_weights (graph, edge); bitmap_clear_bit (weights, 0); if (bitmap_empty_p (weights)) erase_graph_self_edge (graph, edge); } bitmap_clear (fromsol); get_varinfo (to)->address_taken |= get_varinfo (from)->address_taken; get_varinfo (to)->indirect_target |= get_varinfo (from)->indirect_target; } /* Unify nodes in GRAPH that we have found to be part of a cycle. SI is the Strongly Connected Components information structure that tells us what components to unify. UPDATE_CHANGED should be set to true if the changed sbitmap and changed count should be updated to reflect the unification. */ static void process_unification_queue (constraint_graph_t graph, struct scc_info *si, bool update_changed) { size_t i = 0; bitmap tmp = BITMAP_ALLOC (update_changed ? &iteration_obstack : NULL); bitmap_clear (tmp); /* We proceed as follows: For each component in the queue (components are delineated by when current_queue_element->node != next_queue_element->node): rep = representative node for component For each node (tounify) to be unified in the component, merge the solution for tounify into tmp bitmap clear solution for tounify merge edges from tounify into rep merge complex constraints from tounify into rep update changed count to note that tounify will never change again Merge tmp into solution for rep, marking rep changed if this changed rep's solution. Delete any 0 weighted self-edges we now have for rep. */ while (i != VEC_length (unsigned, si->unification_queue)) { unsigned int tounify = VEC_index (unsigned, si->unification_queue, i); unsigned int n = get_varinfo (tounify)->node; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Unifying %s to %s\n", get_varinfo (tounify)->name, get_varinfo (n)->name); if (update_changed) stats.unified_vars_dynamic++; else stats.unified_vars_static++; bitmap_ior_into (tmp, get_varinfo (tounify)->solution); merge_graph_nodes (graph, n, tounify); condense_varmap_nodes (n, tounify); if (update_changed && TEST_BIT (changed, tounify)) { RESET_BIT (changed, tounify); if (!TEST_BIT (changed, n)) SET_BIT (changed, n); else { gcc_assert (changed_count > 0); changed_count--; } } bitmap_clear (get_varinfo (tounify)->solution); ++i; /* If we've either finished processing the entire queue, or finished processing all nodes for component n, update the solution for n. */ if (i == VEC_length (unsigned, si->unification_queue) || get_varinfo (VEC_index (unsigned, si->unification_queue, i))->node != n) { struct constraint_edge edge; /* If the solution changes because of the merging, we need to mark the variable as changed. */ if (bitmap_ior_into (get_varinfo (n)->solution, tmp)) { if (update_changed && !TEST_BIT (changed, n)) { SET_BIT (changed, n); changed_count++; } } bitmap_clear (tmp); edge.src = n; edge.dest = n; edge.weights = NULL; if (valid_graph_edge (graph, edge)) { bitmap weights = get_graph_weights (graph, edge); bitmap_clear_bit (weights, 0); if (bitmap_empty_p (weights)) erase_graph_self_edge (graph, edge); } } } BITMAP_FREE (tmp); } /* Information needed to compute the topological ordering of a graph. */ struct topo_info { /* sbitmap of visited nodes. */ sbitmap visited; /* Array that stores the topological order of the graph, *in reverse*. */ VEC(unsigned,heap) *topo_order; }; /* Initialize and return a topological info structure. */ static struct topo_info * init_topo_info (void) { size_t size = VEC_length (varinfo_t, varmap); struct topo_info *ti = xmalloc (sizeof (struct topo_info)); ti->visited = sbitmap_alloc (size); sbitmap_zero (ti->visited); ti->topo_order = VEC_alloc (unsigned, heap, 1); return ti; } /* Free the topological sort info pointed to by TI. */ static void free_topo_info (struct topo_info *ti) { sbitmap_free (ti->visited); VEC_free (unsigned, heap, ti->topo_order); free (ti); } /* Visit the graph in topological order, and store the order in the topo_info structure. */ static void topo_visit (constraint_graph_t graph, struct topo_info *ti, unsigned int n) { VEC(constraint_edge_t,heap) *succs = graph->succs[n]; constraint_edge_t c; int i; SET_BIT (ti->visited, n); for (i = 0; VEC_iterate (constraint_edge_t, succs, i, c); i++) { if (!TEST_BIT (ti->visited, c->dest)) topo_visit (graph, ti, c->dest); } VEC_safe_push (unsigned, heap, ti->topo_order, n); } /* Return true if variable N + OFFSET is a legal field of N. */ static bool type_safe (unsigned int n, unsigned HOST_WIDE_INT *offset) { varinfo_t ninfo = get_varinfo (n); /* For things we've globbed to single variables, any offset into the variable acts like the entire variable, so that it becomes offset 0. */ if (ninfo->is_special_var || ninfo->is_artificial_var || ninfo->is_unknown_size_var) { *offset = 0; return true; } return (get_varinfo (n)->offset + *offset) < get_varinfo (n)->fullsize; } /* Process a constraint C that represents *x = &y. */ static void do_da_constraint (constraint_graph_t graph ATTRIBUTE_UNUSED, constraint_t c, bitmap delta) { unsigned int rhs = c->rhs.var; unsigned int j; bitmap_iterator bi; /* For each member j of Delta (Sol(x)), add x to Sol(j) */ EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi) { unsigned HOST_WIDE_INT offset = c->lhs.offset; if (type_safe (j, &offset) && !(get_varinfo (j)->is_special_var)) { /* *x != NULL && *x != ANYTHING*/ varinfo_t v; unsigned int t; bitmap sol; unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + offset; v = first_vi_for_offset (get_varinfo (j), fieldoffset); if (!v) continue; t = v->node; sol = get_varinfo (t)->solution; if (!bitmap_bit_p (sol, rhs)) { bitmap_set_bit (sol, rhs); if (!TEST_BIT (changed, t)) { SET_BIT (changed, t); changed_count++; } } } else if (dump_file && !(get_varinfo (j)->is_special_var)) fprintf (dump_file, "Untypesafe usage in do_da_constraint.\n"); } } /* Process a constraint C that represents x = *y, using DELTA as the starting solution. */ static void do_sd_constraint (constraint_graph_t graph, constraint_t c, bitmap delta) { unsigned int lhs = get_varinfo (c->lhs.var)->node; bool flag = false; bitmap sol = get_varinfo (lhs)->solution; unsigned int j; bitmap_iterator bi; /* For each variable j in delta (Sol(y)), add an edge in the graph from j to x, and union Sol(j) into Sol(x). */ EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi) { unsigned HOST_WIDE_INT roffset = c->rhs.offset; if (type_safe (j, &roffset)) { varinfo_t v; unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + roffset; unsigned int t; v = first_vi_for_offset (get_varinfo (j), fieldoffset); if (!v) continue; t = v->node; if (int_add_graph_edge (graph, lhs, t, 0)) flag |= bitmap_ior_into (sol, get_varinfo (t)->solution); } else if (dump_file && !(get_varinfo (j)->is_special_var)) fprintf (dump_file, "Untypesafe usage in do_sd_constraint\n"); } /* If the LHS solution changed, mark the var as changed. */ if (flag) { get_varinfo (lhs)->solution = sol; if (!TEST_BIT (changed, lhs)) { SET_BIT (changed, lhs); changed_count++; } } } /* Process a constraint C that represents *x = y. */ static void do_ds_constraint (constraint_graph_t graph, constraint_t c, bitmap delta) { unsigned int rhs = get_varinfo (c->rhs.var)->node; unsigned HOST_WIDE_INT roff = c->rhs.offset; bitmap sol = get_varinfo (rhs)->solution; unsigned int j; bitmap_iterator bi; /* For each member j of delta (Sol(x)), add an edge from y to j and union Sol(y) into Sol(j) */ EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi) { unsigned HOST_WIDE_INT loff = c->lhs.offset; if (type_safe (j, &loff) && !(get_varinfo(j)->is_special_var)) { varinfo_t v; unsigned int t; unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + loff; v = first_vi_for_offset (get_varinfo (j), fieldoffset); if (!v) continue; t = v->node; if (int_add_graph_edge (graph, t, rhs, roff)) { bitmap tmp = get_varinfo (t)->solution; if (set_union_with_increment (tmp, sol, roff)) { get_varinfo (t)->solution = tmp; if (t == rhs) { sol = get_varinfo (rhs)->solution; } if (!TEST_BIT (changed, t)) { SET_BIT (changed, t); changed_count++; } } } } else if (dump_file && !(get_varinfo (j)->is_special_var)) fprintf (dump_file, "Untypesafe usage in do_ds_constraint\n"); } } /* Handle a non-simple (simple meaning requires no iteration), non-copy constraint (IE *x = &y, x = *y, and *x = y). */ static void do_complex_constraint (constraint_graph_t graph, constraint_t c, bitmap delta) { if (c->lhs.type == DEREF) { if (c->rhs.type == ADDRESSOF) { /* *x = &y */ do_da_constraint (graph, c, delta); } else { /* *x = y */ do_ds_constraint (graph, c, delta); } } else { /* x = *y */ if (!(get_varinfo (c->lhs.var)->is_special_var)) do_sd_constraint (graph, c, delta); } } /* Initialize and return a new SCC info structure. */ static struct scc_info * init_scc_info (void) { struct scc_info *si = xmalloc (sizeof (struct scc_info)); size_t size = VEC_length (varinfo_t, varmap); si->current_index = 0; si->visited = sbitmap_alloc (size); sbitmap_zero (si->visited); si->in_component = sbitmap_alloc (size); sbitmap_ones (si->in_component); si->visited_index = xcalloc (sizeof (unsigned int), size + 1); si->scc_stack = VEC_alloc (unsigned, heap, 1); si->unification_queue = VEC_alloc (unsigned, heap, 1); return si; } /* Free an SCC info structure pointed to by SI */ static void free_scc_info (struct scc_info *si) { sbitmap_free (si->visited); sbitmap_free (si->in_component); free (si->visited_index); VEC_free (unsigned, heap, si->scc_stack); VEC_free (unsigned, heap, si->unification_queue); free(si); } /* Find cycles in GRAPH that occur, using strongly connected components, and collapse the cycles into a single representative node. if UPDATE_CHANGED is true, then update the changed sbitmap to note those nodes whose solutions have changed as a result of collapsing. */ static void find_and_collapse_graph_cycles (constraint_graph_t graph, bool update_changed) { unsigned int i; unsigned int size = VEC_length (varinfo_t, varmap); struct scc_info *si = init_scc_info (); for (i = 0; i != size; ++i) if (!TEST_BIT (si->visited, i) && get_varinfo (i)->node == i) scc_visit (graph, si, i); process_unification_queue (graph, si, update_changed); free_scc_info (si); } /* Compute a topological ordering for GRAPH, and store the result in the topo_info structure TI. */ static void compute_topo_order (constraint_graph_t graph, struct topo_info *ti) { unsigned int i; unsigned int size = VEC_length (varinfo_t, varmap); for (i = 0; i != size; ++i) if (!TEST_BIT (ti->visited, i) && get_varinfo (i)->node == i) topo_visit (graph, ti, i); } /* Return true if bitmap B is empty, or a bitmap other than bit 0 is set. */ static bool bitmap_other_than_zero_bit_set (bitmap b) { unsigned int i; bitmap_iterator bi; if (bitmap_empty_p (b)) return false; EXECUTE_IF_SET_IN_BITMAP (b, 1, i, bi) return true; return false; } /* Perform offline variable substitution. This is a linear time way of identifying variables that must have equivalent points-to sets, including those caused by static cycles, and single entry subgraphs, in the constraint graph. The technique is described in "Off-line variable substitution for scaling points-to analysis" by Atanas Rountev and Satish Chandra, in "ACM SIGPLAN Notices" volume 35, number 5, pages 47-56. */ static void perform_var_substitution (constraint_graph_t graph) { struct topo_info *ti = init_topo_info (); /* Compute the topological ordering of the graph, then visit each node in topological order. */ compute_topo_order (graph, ti); while (VEC_length (unsigned, ti->topo_order) != 0) { unsigned int i = VEC_pop (unsigned, ti->topo_order); unsigned int pred; varinfo_t vi = get_varinfo (i); bool okay_to_elim = false; unsigned int root = VEC_length (varinfo_t, varmap); VEC(constraint_edge_t,heap) *predvec = graph->preds[i]; constraint_edge_t ce; bitmap tmp; /* We can't eliminate things whose address is taken, or which is the target of a dereference. */ if (vi->address_taken || vi->indirect_target) continue; /* See if all predecessors of I are ripe for elimination */ for (pred = 0; VEC_iterate (constraint_edge_t, predvec, pred, ce); pred++) { bitmap weight; unsigned int w; weight = get_graph_weights (graph, *ce); /* We can't eliminate variables that have nonzero weighted edges between them. */ if (bitmap_other_than_zero_bit_set (weight)) { okay_to_elim = false; break; } w = get_varinfo (ce->dest)->node; /* We can't eliminate the node if one of the predecessors is part of a different strongly connected component. */ if (!okay_to_elim) { root = w; okay_to_elim = true; } else if (w != root) { okay_to_elim = false; break; } /* Theorem 4 in Rountev and Chandra: If i is a direct node, then Solution(i) is a subset of Solution (w), where w is a predecessor in the graph. Corollary: If all predecessors of i have the same points-to set, then i has that same points-to set as those predecessors. */ tmp = BITMAP_ALLOC (NULL); bitmap_and_compl (tmp, get_varinfo (i)->solution, get_varinfo (w)->solution); if (!bitmap_empty_p (tmp)) { okay_to_elim = false; BITMAP_FREE (tmp); break; } BITMAP_FREE (tmp); } /* See if the root is different than the original node. If so, we've found an equivalence. */ if (root != get_varinfo (i)->node && okay_to_elim) { /* Found an equivalence */ get_varinfo (i)->node = root; collapse_nodes (graph, root, i); if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Collapsing %s into %s\n", get_varinfo (i)->name, get_varinfo (root)->name); stats.collapsed_vars++; } } free_topo_info (ti); } /* Solve the constraint graph GRAPH using our worklist solver. This is based on the PW* family of solvers from the "Efficient Field Sensitive Pointer Analysis for C" paper. It works by iterating over all the graph nodes, processing the complex constraints and propagating the copy constraints, until everything stops changed. This corresponds to steps 6-8 in the solving list given above. */ static void solve_graph (constraint_graph_t graph) { unsigned int size = VEC_length (varinfo_t, varmap); unsigned int i; changed_count = size; changed = sbitmap_alloc (size); sbitmap_ones (changed); /* The already collapsed/unreachable nodes will never change, so we need to account for them in changed_count. */ for (i = 0; i < size; i++) if (get_varinfo (i)->node != i) changed_count--; while (changed_count > 0) { unsigned int i; struct topo_info *ti = init_topo_info (); stats.iterations++; bitmap_obstack_initialize (&iteration_obstack); if (edge_added) { /* We already did cycle elimination once, when we did variable substitution, so we don't need it again for the first iteration. */ if (stats.iterations > 1) find_and_collapse_graph_cycles (graph, true); edge_added = false; } compute_topo_order (graph, ti); while (VEC_length (unsigned, ti->topo_order) != 0) { i = VEC_pop (unsigned, ti->topo_order); gcc_assert (get_varinfo (i)->node == i); /* If the node has changed, we need to process the complex constraints and outgoing edges again. */ if (TEST_BIT (changed, i)) { unsigned int j; constraint_t c; constraint_edge_t e; bitmap solution; VEC(constraint_t,heap) *complex = get_varinfo (i)->complex; VEC(constraint_edge_t,heap) *succs; RESET_BIT (changed, i); changed_count--; /* Process the complex constraints */ solution = get_varinfo (i)->solution; for (j = 0; VEC_iterate (constraint_t, complex, j, c); j++) do_complex_constraint (graph, c, solution); /* Propagate solution to all successors. */ succs = graph->succs[i]; for (j = 0; VEC_iterate (constraint_edge_t, succs, j, e); j++) { bitmap tmp = get_varinfo (e->dest)->solution; bool flag = false; unsigned int k; bitmap weights = e->weights; bitmap_iterator bi; gcc_assert (!bitmap_empty_p (weights)); EXECUTE_IF_SET_IN_BITMAP (weights, 0, k, bi) flag |= set_union_with_increment (tmp, solution, k); if (flag) { get_varinfo (e->dest)->solution = tmp; if (!TEST_BIT (changed, e->dest)) { SET_BIT (changed, e->dest); changed_count++; } } } } } free_topo_info (ti); bitmap_obstack_release (&iteration_obstack); } sbitmap_free (changed); } /* CONSTRAINT AND VARIABLE GENERATION FUNCTIONS */ /* Map from trees to variable ids. */ static htab_t id_for_tree; typedef struct tree_id { tree t; unsigned int id; } *tree_id_t; /* Hash a tree id structure. */ static hashval_t tree_id_hash (const void *p) { const tree_id_t ta = (tree_id_t) p; return htab_hash_pointer (ta->t); } /* Return true if the tree in P1 and the tree in P2 are the same. */ static int tree_id_eq (const void *p1, const void *p2) { const tree_id_t ta1 = (tree_id_t) p1; const tree_id_t ta2 = (tree_id_t) p2; return ta1->t == ta2->t; } /* Insert ID as the variable id for tree T in the hashtable. */ static void insert_id_for_tree (tree t, int id) { void **slot; struct tree_id finder; tree_id_t new_pair; finder.t = t; slot = htab_find_slot (id_for_tree, &finder, INSERT); gcc_assert (*slot == NULL); new_pair = xmalloc (sizeof (struct tree_id)); new_pair->t = t; new_pair->id = id; *slot = (void *)new_pair; } /* Find the variable id for tree T in ID_FOR_TREE. If T does not exist in the hash table, return false, otherwise, return true and set *ID to the id we found. */ static bool lookup_id_for_tree (tree t, unsigned int *id) { tree_id_t pair; struct tree_id finder; finder.t = t; pair = htab_find (id_for_tree, &finder); if (pair == NULL) return false; *id = pair->id; return true; } /* Return a printable name for DECL */ static const char * alias_get_name (tree decl) { const char *res = get_name (decl); char *temp; int num_printed = 0; if (res != NULL) return res; res = "NULL"; if (TREE_CODE (decl) == SSA_NAME) { num_printed = asprintf (&temp, "%s_%u", alias_get_name (SSA_NAME_VAR (decl)), SSA_NAME_VERSION (decl)); } else if (DECL_P (decl)) { num_printed = asprintf (&temp, "D.%u", DECL_UID (decl)); } if (num_printed > 0) { res = ggc_strdup (temp); free (temp); } return res; } /* Find the variable id for tree T in the hashtable. If T doesn't exist in the hash table, create an entry for it. */ static unsigned int get_id_for_tree (tree t) { tree_id_t pair; struct tree_id finder; finder.t = t; pair = htab_find (id_for_tree, &finder); if (pair == NULL) return create_variable_info_for (t, alias_get_name (t)); return pair->id; } /* Get a constraint expression from an SSA_VAR_P node. */ static struct constraint_expr get_constraint_exp_from_ssa_var (tree t) { struct constraint_expr cexpr; gcc_assert (SSA_VAR_P (t) || DECL_P (t)); /* For parameters, get at the points-to set for the actual parm decl. */ if (TREE_CODE (t) == SSA_NAME && TREE_CODE (SSA_NAME_VAR (t)) == PARM_DECL && default_def (SSA_NAME_VAR (t)) == t) return get_constraint_exp_from_ssa_var (SSA_NAME_VAR (t)); cexpr.type = SCALAR; cexpr.var = get_id_for_tree (t); /* If we determine the result is "anything", and we know this is readonly, say it points to readonly memory instead. */ if (cexpr.var == anything_id && TREE_READONLY (t)) { cexpr.type = ADDRESSOF; cexpr.var = readonly_id; } cexpr.offset = 0; return cexpr; } /* Process a completed constraint T, and add it to the constraint list. */ static void process_constraint (constraint_t t) { struct constraint_expr rhs = t->rhs; struct constraint_expr lhs = t->lhs; gcc_assert (rhs.var < VEC_length (varinfo_t, varmap)); gcc_assert (lhs.var < VEC_length (varinfo_t, varmap)); /* ANYTHING == ANYTHING is pointless. */ if (lhs.var == anything_id && rhs.var == anything_id) return; /* If we have &ANYTHING = something, convert to SOMETHING = &ANYTHING) */ else if (lhs.var == anything_id && lhs.type == ADDRESSOF) { rhs = t->lhs; t->lhs = t->rhs; t->rhs = rhs; process_constraint (t); } /* This can happen in our IR with things like n->a = *p */ else if (rhs.type == DEREF && lhs.type == DEREF && rhs.var != anything_id) { /* Split into tmp = *rhs, *lhs = tmp */ tree rhsdecl = get_varinfo (rhs.var)->decl; tree pointertype = TREE_TYPE (rhsdecl); tree pointedtotype = TREE_TYPE (pointertype); tree tmpvar = create_tmp_var_raw (pointedtotype, "doubledereftmp"); struct constraint_expr tmplhs = get_constraint_exp_from_ssa_var (tmpvar); /* If this is an aggregate of known size, we should have passed this off to do_structure_copy, and it should have broken it up. */ gcc_assert (!AGGREGATE_TYPE_P (pointedtotype) || get_varinfo (rhs.var)->is_unknown_size_var); process_constraint (new_constraint (tmplhs, rhs)); process_constraint (new_constraint (lhs, tmplhs)); } else if (rhs.type == ADDRESSOF) { varinfo_t vi; gcc_assert (rhs.offset == 0); for (vi = get_varinfo (rhs.var); vi != NULL; vi = vi->next) vi->address_taken = true; VEC_safe_push (constraint_t, heap, constraints, t); } else { if (lhs.type != DEREF && rhs.type == DEREF) get_varinfo (lhs.var)->indirect_target = true; VEC_safe_push (constraint_t, heap, constraints, t); } } /* Return the position, in bits, of FIELD_DECL from the beginning of its structure. */ static unsigned HOST_WIDE_INT bitpos_of_field (const tree fdecl) { if (TREE_CODE (DECL_FIELD_OFFSET (fdecl)) != INTEGER_CST || TREE_CODE (DECL_FIELD_BIT_OFFSET (fdecl)) != INTEGER_CST) return -1; return (tree_low_cst (DECL_FIELD_OFFSET (fdecl), 1) * 8) + tree_low_cst (DECL_FIELD_BIT_OFFSET (fdecl), 1); } /* Return true if an access to [ACCESSPOS, ACCESSSIZE] overlaps with a field at [FIELDPOS, FIELDSIZE] */ static bool offset_overlaps_with_access (const unsigned HOST_WIDE_INT fieldpos, const unsigned HOST_WIDE_INT fieldsize, const unsigned HOST_WIDE_INT accesspos, const unsigned HOST_WIDE_INT accesssize) { if (fieldpos == accesspos && fieldsize == accesssize) return true; if (accesspos >= fieldpos && accesspos < (fieldpos + fieldsize)) return true; if (accesspos < fieldpos && (accesspos + accesssize > fieldpos)) return true; return false; } /* Given a COMPONENT_REF T, return the constraint_expr for it. */ static struct constraint_expr get_constraint_for_component_ref (tree t, bool *need_anyoffset) { struct constraint_expr result; HOST_WIDE_INT bitsize = -1; HOST_WIDE_INT bitpos; tree offset = NULL_TREE; enum machine_mode mode; int unsignedp; int volatilep; tree forzero; result.offset = 0; result.type = SCALAR; result.var = 0; /* Some people like to do cute things like take the address of &0->a.b */ forzero = t; while (!SSA_VAR_P (forzero) && !CONSTANT_CLASS_P (forzero)) forzero = TREE_OPERAND (forzero, 0); if (CONSTANT_CLASS_P (forzero) && integer_zerop (forzero)) { result.offset = 0; result.var = integer_id; result.type = SCALAR; return result; } t = get_inner_reference (t, &bitsize, &bitpos, &offset, &mode, &unsignedp, &volatilep, false); result = get_constraint_for (t, need_anyoffset); /* This can also happen due to weird offsetof type macros. */ if (TREE_CODE (t) != ADDR_EXPR && result.type == ADDRESSOF) result.type = SCALAR; /* If we know where this goes, then yay. Otherwise, booo. */ if (offset == NULL && bitsize != -1) { result.offset = bitpos; } else if (need_anyoffset) { result.offset = 0; *need_anyoffset = true; } else { result.var = anything_id; result.offset = 0; } if (result.type == SCALAR) { /* In languages like C, you can access one past the end of an array. You aren't allowed to dereference it, so we can ignore this constraint. When we handle pointer subtraction, we may have to do something cute here. */ if (result.offset < get_varinfo (result.var)->fullsize && bitsize != 0) { /* It's also not true that the constraint will actually start at the right offset, it may start in some padding. We only care about setting the constraint to the first actual field it touches, so walk to find it. */ varinfo_t curr; for (curr = get_varinfo (result.var); curr; curr = curr->next) { if (offset_overlaps_with_access (curr->offset, curr->size, result.offset, bitsize)) { result.var = curr->id; break; } } /* assert that we found *some* field there. The user couldn't be accessing *only* padding. */ gcc_assert (curr); } else if (bitsize == 0) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Access to zero-sized part of variable," "ignoring\n"); } else if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Access to past the end of variable, ignoring\n"); result.offset = 0; } return result; } /* Dereference the constraint expression CONS, and return the result. DEREF (ADDRESSOF) = SCALAR DEREF (SCALAR) = DEREF DEREF (DEREF) = (temp = DEREF1; result = DEREF(temp)) This is needed so that we can handle dereferencing DEREF constraints. */ static struct constraint_expr do_deref (struct constraint_expr cons) { if (cons.type == SCALAR) { cons.type = DEREF; return cons; } else if (cons.type == ADDRESSOF) { cons.type = SCALAR; return cons; } else if (cons.type == DEREF) { tree tmpvar = create_tmp_var_raw (ptr_type_node, "derefmp"); struct constraint_expr tmplhs = get_constraint_exp_from_ssa_var (tmpvar); process_constraint (new_constraint (tmplhs, cons)); cons.var = tmplhs.var; return cons; } gcc_unreachable (); } /* Given a tree T, return the constraint expression for it. */ static struct constraint_expr get_constraint_for (tree t, bool *need_anyoffset) { struct constraint_expr temp; /* x = integer is all glommed to a single variable, which doesn't point to anything by itself. That is, of course, unless it is an integer constant being treated as a pointer, in which case, we will return that this is really the addressof anything. This happens below, since it will fall into the default case. The only case we know something about an integer treated like a pointer is when it is the NULL pointer, and then we just say it points to NULL. */ if (TREE_CODE (t) == INTEGER_CST && !POINTER_TYPE_P (TREE_TYPE (t))) { temp.var = integer_id; temp.type = SCALAR; temp.offset = 0; return temp; } else if (TREE_CODE (t) == INTEGER_CST && integer_zerop (t)) { temp.var = nothing_id; temp.type = ADDRESSOF; temp.offset = 0; return temp; } switch (TREE_CODE_CLASS (TREE_CODE (t))) { case tcc_expression: { switch (TREE_CODE (t)) { case ADDR_EXPR: { temp = get_constraint_for (TREE_OPERAND (t, 0), need_anyoffset); if (temp.type == DEREF) temp.type = SCALAR; else temp.type = ADDRESSOF; return temp; } break; case CALL_EXPR: /* XXX: In interprocedural mode, if we didn't have the body, we would need to do *each pointer argument = &ANYTHING added. */ if (call_expr_flags (t) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)) { varinfo_t vi; tree heapvar = heapvar_lookup (t); if (heapvar == NULL) { heapvar = create_tmp_var_raw (ptr_type_node, "HEAP"); DECL_EXTERNAL (heapvar) = 1; add_referenced_tmp_var (heapvar); heapvar_insert (t, heapvar); } temp.var = create_variable_info_for (heapvar, alias_get_name (heapvar)); vi = get_varinfo (temp.var); vi->is_artificial_var = 1; vi->is_heap_var = 1; temp.type = ADDRESSOF; temp.offset = 0; return temp; } /* FALLTHRU */ default: { temp.type = ADDRESSOF; temp.var = anything_id; temp.offset = 0; return temp; } } } case tcc_reference: { switch (TREE_CODE (t)) { case INDIRECT_REF: { temp = get_constraint_for (TREE_OPERAND (t, 0), need_anyoffset); temp = do_deref (temp); return temp; } case ARRAY_REF: case ARRAY_RANGE_REF: case COMPONENT_REF: temp = get_constraint_for_component_ref (t, need_anyoffset); return temp; default: { temp.type = ADDRESSOF; temp.var = anything_id; temp.offset = 0; return temp; } } } case tcc_unary: { switch (TREE_CODE (t)) { case NOP_EXPR: case CONVERT_EXPR: case NON_LVALUE_EXPR: { tree op = TREE_OPERAND (t, 0); /* Cast from non-pointer to pointers are bad news for us. Anything else, we see through */ if (!(POINTER_TYPE_P (TREE_TYPE (t)) && ! POINTER_TYPE_P (TREE_TYPE (op)))) return get_constraint_for (op, need_anyoffset); /* FALLTHRU */ } default: { temp.type = ADDRESSOF; temp.var = anything_id; temp.offset = 0; return temp; } } } case tcc_exceptional: { switch (TREE_CODE (t)) { case PHI_NODE: return get_constraint_for (PHI_RESULT (t), need_anyoffset); case SSA_NAME: return get_constraint_exp_from_ssa_var (t); default: { temp.type = ADDRESSOF; temp.var = anything_id; temp.offset = 0; return temp; } } } case tcc_declaration: return get_constraint_exp_from_ssa_var (t); default: { temp.type = ADDRESSOF; temp.var = anything_id; temp.offset = 0; return temp; } } } /* Handle the structure copy case where we have a simple structure copy between LHS and RHS that is of SIZE (in bits) For each field of the lhs variable (lhsfield) For each field of the rhs variable at lhsfield.offset (rhsfield) add the constraint lhsfield = rhsfield If we fail due to some kind of type unsafety or other thing we can't handle, return false. We expect the caller to collapse the variable in that case. */ static bool do_simple_structure_copy (const struct constraint_expr lhs, const struct constraint_expr rhs, const unsigned HOST_WIDE_INT size) { varinfo_t p = get_varinfo (lhs.var); unsigned HOST_WIDE_INT pstart, last; pstart = p->offset; last = p->offset + size; for (; p && p->offset < last; p = p->next) { varinfo_t q; struct constraint_expr templhs = lhs; struct constraint_expr temprhs = rhs; unsigned HOST_WIDE_INT fieldoffset; templhs.var = p->id; q = get_varinfo (temprhs.var); fieldoffset = p->offset - pstart; q = first_vi_for_offset (q, q->offset + fieldoffset); if (!q) return false; temprhs.var = q->id; process_constraint (new_constraint (templhs, temprhs)); } return true; } /* Handle the structure copy case where we have a structure copy between a aggregate on the LHS and a dereference of a pointer on the RHS that is of SIZE (in bits) For each field of the lhs variable (lhsfield) rhs.offset = lhsfield->offset add the constraint lhsfield = rhs */ static void do_rhs_deref_structure_copy (const struct constraint_expr lhs, const struct constraint_expr rhs, const unsigned HOST_WIDE_INT size) { varinfo_t p = get_varinfo (lhs.var); unsigned HOST_WIDE_INT pstart,last; pstart = p->offset; last = p->offset + size; for (; p && p->offset < last; p = p->next) { varinfo_t q; struct constraint_expr templhs = lhs; struct constraint_expr temprhs = rhs; unsigned HOST_WIDE_INT fieldoffset; if (templhs.type == SCALAR) templhs.var = p->id; else templhs.offset = p->offset; q = get_varinfo (temprhs.var); fieldoffset = p->offset - pstart; temprhs.offset += fieldoffset; process_constraint (new_constraint (templhs, temprhs)); } } /* Handle the structure copy case where we have a structure copy between a aggregate on the RHS and a dereference of a pointer on the LHS that is of SIZE (in bits) For each field of the rhs variable (rhsfield) lhs.offset = rhsfield->offset add the constraint lhs = rhsfield */ static void do_lhs_deref_structure_copy (const struct constraint_expr lhs, const struct constraint_expr rhs, const unsigned HOST_WIDE_INT size) { varinfo_t p = get_varinfo (rhs.var); unsigned HOST_WIDE_INT pstart,last; pstart = p->offset; last = p->offset + size; for (; p && p->offset < last; p = p->next) { varinfo_t q; struct constraint_expr templhs = lhs; struct constraint_expr temprhs = rhs; unsigned HOST_WIDE_INT fieldoffset; if (temprhs.type == SCALAR) temprhs.var = p->id; else temprhs.offset = p->offset; q = get_varinfo (templhs.var); fieldoffset = p->offset - pstart; templhs.offset += fieldoffset; process_constraint (new_constraint (templhs, temprhs)); } } /* Sometimes, frontends like to give us bad type information. This function will collapse all the fields from VAR to the end of VAR, into VAR, so that we treat those fields as a single variable. We return the variable they were collapsed into. */ static unsigned int collapse_rest_of_var (unsigned int var) { varinfo_t currvar = get_varinfo (var); varinfo_t field; for (field = currvar->next; field; field = field->next) { if (dump_file) fprintf (dump_file, "Type safety: Collapsing var %s into %s\n", field->name, currvar->name); gcc_assert (!field->collapsed_to); field->collapsed_to = currvar; } currvar->next = NULL; currvar->size = currvar->fullsize - currvar->offset; return currvar->id; } /* Handle aggregate copies by expanding into copies of the respective fields of the structures. */ static void do_structure_copy (tree lhsop, tree rhsop) { struct constraint_expr lhs, rhs, tmp; varinfo_t p; unsigned HOST_WIDE_INT lhssize; unsigned HOST_WIDE_INT rhssize; lhs = get_constraint_for (lhsop, NULL); rhs = get_constraint_for (rhsop, NULL); /* If we have special var = x, swap it around. */ if (lhs.var <= integer_id && !(get_varinfo (rhs.var)->is_special_var)) { tmp = lhs; lhs = rhs; rhs = tmp; } /* This is fairly conservative for the RHS == ADDRESSOF case, in that it's possible it's something we could handle. However, most cases falling into this are dealing with transparent unions, which are slightly weird. */ if (rhs.type == ADDRESSOF && !(get_varinfo (rhs.var)->is_special_var)) { rhs.type = ADDRESSOF; rhs.var = anything_id; } /* If the RHS is a special var, or an addressof, set all the LHS fields to that special var. */ if (rhs.var <= integer_id) { for (p = get_varinfo (lhs.var); p; p = p->next) { struct constraint_expr templhs = lhs; struct constraint_expr temprhs = rhs; if (templhs.type == SCALAR ) templhs.var = p->id; else templhs.offset += p->offset; process_constraint (new_constraint (templhs, temprhs)); } } else { tree rhstype = TREE_TYPE (rhsop); tree lhstype = TREE_TYPE (lhsop); tree rhstypesize = TYPE_SIZE (rhstype); tree lhstypesize = TYPE_SIZE (lhstype); /* If we have a variably sized types on the rhs or lhs, and a deref constraint, add the constraint, lhsconstraint = &ANYTHING. This is conservatively correct because either the lhs is an unknown sized var (if the constraint is SCALAR), or the lhs is a DEREF constraint, and every variable it can point to must be unknown sized anyway, so we don't need to worry about fields at all. */ if ((rhs.type == DEREF && TREE_CODE (rhstypesize) != INTEGER_CST) || (lhs.type == DEREF && TREE_CODE (lhstypesize) != INTEGER_CST)) { rhs.var = anything_id; rhs.type = ADDRESSOF; rhs.offset = 0; process_constraint (new_constraint (lhs, rhs)); return; } /* The size only really matters insofar as we don't set more or less of the variable. If we hit an unknown size var, the size should be the whole darn thing. */ if (get_varinfo (rhs.var)->is_unknown_size_var) rhssize = ~0; else rhssize = TREE_INT_CST_LOW (rhstypesize); if (get_varinfo (lhs.var)->is_unknown_size_var) lhssize = ~0; else lhssize = TREE_INT_CST_LOW (lhstypesize); if (rhs.type == SCALAR && lhs.type == SCALAR) { if (!do_simple_structure_copy (lhs, rhs, MIN (lhssize, rhssize))) { lhs.var = collapse_rest_of_var (lhs.var); rhs.var = collapse_rest_of_var (rhs.var); lhs.offset = 0; rhs.offset = 0; lhs.type = SCALAR; rhs.type = SCALAR; process_constraint (new_constraint (lhs, rhs)); } } else if (lhs.type != DEREF && rhs.type == DEREF) do_rhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize)); else if (lhs.type == DEREF && rhs.type != DEREF) do_lhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize)); else { tree pointedtotype = lhstype; tree tmpvar; gcc_assert (rhs.type == DEREF && lhs.type == DEREF); tmpvar = create_tmp_var_raw (pointedtotype, "structcopydereftmp"); do_structure_copy (tmpvar, rhsop); do_structure_copy (lhsop, tmpvar); } } } /* Update related alias information kept in AI. This is used when building name tags, alias sets and deciding grouping heuristics. STMT is the statement to process. This function also updates ADDRESSABLE_VARS. */ static void update_alias_info (tree stmt, struct alias_info *ai) { bitmap addr_taken; use_operand_p use_p; ssa_op_iter iter; bool stmt_escapes_p = is_escape_site (stmt, ai); tree op; /* Mark all the variables whose address are taken by the statement. */ addr_taken = addresses_taken (stmt); if (addr_taken) { bitmap_ior_into (addressable_vars, addr_taken); /* If STMT is an escape point, all the addresses taken by it are call-clobbered. */ if (stmt_escapes_p) { bitmap_iterator bi; unsigned i; EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi) mark_call_clobbered (referenced_var (i)); } } /* Process each operand use. If an operand may be aliased, keep track of how many times it's being used. For pointers, determine whether they are dereferenced by the statement, or whether their value escapes, etc. */ FOR_EACH_PHI_OR_STMT_USE (use_p, stmt, iter, SSA_OP_USE) { tree op, var; var_ann_t v_ann; struct ptr_info_def *pi; bool is_store, is_potential_deref; unsigned num_uses, num_derefs; op = USE_FROM_PTR (use_p); /* If STMT is a PHI node, OP may be an ADDR_EXPR. If so, add it to the set of addressable variables. */ if (TREE_CODE (op) == ADDR_EXPR) { gcc_assert (TREE_CODE (stmt) == PHI_NODE); /* PHI nodes don't have annotations for pinning the set of addresses taken, so we collect them here. FIXME, should we allow PHI nodes to have annotations so that they can be treated like regular statements? Currently, they are treated as second-class statements. */ add_to_addressable_set (TREE_OPERAND (op, 0), &addressable_vars); continue; } /* Ignore constants. */ if (TREE_CODE (op) != SSA_NAME) continue; var = SSA_NAME_VAR (op); v_ann = var_ann (var); /* If the operand's variable may be aliased, keep track of how many times we've referenced it. This is used for alias grouping in compute_flow_insensitive_aliasing. */ if (may_be_aliased (var)) NUM_REFERENCES_INC (v_ann); /* We are only interested in pointers. */ if (!POINTER_TYPE_P (TREE_TYPE (op))) continue; pi = get_ptr_info (op); /* Add OP to AI->PROCESSED_PTRS, if it's not there already. */ if (!TEST_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (op))) { SET_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (op)); VARRAY_PUSH_TREE (ai->processed_ptrs, op); } /* If STMT is a PHI node, then it will not have pointer dereferences and it will not be an escape point. */ if (TREE_CODE (stmt) == PHI_NODE) continue; /* Determine whether OP is a dereferenced pointer, and if STMT is an escape point, whether OP escapes. */ count_uses_and_derefs (op, stmt, &num_uses, &num_derefs, &is_store); /* Handle a corner case involving address expressions of the form '&PTR->FLD'. The problem with these expressions is that they do not represent a dereference of PTR. However, if some other transformation propagates them into an INDIRECT_REF expression, we end up with '*(&PTR->FLD)' which is folded into 'PTR->FLD'. So, if the original code had no other dereferences of PTR, the aliaser will not create memory tags for it, and when &PTR->FLD gets propagated to INDIRECT_REF expressions, the memory operations will receive no V_MAY_DEF/VUSE operands. One solution would be to have count_uses_and_derefs consider &PTR->FLD a dereference of PTR. But that is wrong, since it is not really a dereference but an offset calculation. What we do here is to recognize these special ADDR_EXPR nodes. Since these expressions are never GIMPLE values (they are not GIMPLE invariants), they can only appear on the RHS of an assignment and their base address is always an INDIRECT_REF expression. */ is_potential_deref = false; if (TREE_CODE (stmt) == MODIFY_EXPR && TREE_CODE (TREE_OPERAND (stmt, 1)) == ADDR_EXPR && !is_gimple_val (TREE_OPERAND (stmt, 1))) { /* If the RHS if of the form &PTR->FLD and PTR == OP, then this represents a potential dereference of PTR. */ tree rhs = TREE_OPERAND (stmt, 1); tree base = get_base_address (TREE_OPERAND (rhs, 0)); if (TREE_CODE (base) == INDIRECT_REF && TREE_OPERAND (base, 0) == op) is_potential_deref = true; } if (num_derefs > 0 || is_potential_deref) { /* Mark OP as dereferenced. In a subsequent pass, dereferenced pointers that point to a set of variables will be assigned a name tag to alias all the variables OP points to. */ pi->is_dereferenced = 1; /* Keep track of how many time we've dereferenced each pointer. */ NUM_REFERENCES_INC (v_ann); /* If this is a store operation, mark OP as being dereferenced to store, otherwise mark it as being dereferenced to load. */ if (is_store) bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var)); else bitmap_set_bit (ai->dereferenced_ptrs_load, DECL_UID (var)); } if (stmt_escapes_p && num_derefs < num_uses) { /* If STMT is an escape point and STMT contains at least one direct use of OP, then the value of OP escapes and so the pointed-to variables need to be marked call-clobbered. */ pi->value_escapes_p = 1; /* If the statement makes a function call, assume that pointer OP will be dereferenced in a store operation inside the called function. */ if (get_call_expr_in (stmt)) { bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var)); pi->is_dereferenced = 1; } } } if (TREE_CODE (stmt) == PHI_NODE) return; /* Update reference counter for definitions to any potentially aliased variable. This is used in the alias grouping heuristics. */ FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF) { tree var = SSA_NAME_VAR (op); var_ann_t ann = var_ann (var); bitmap_set_bit (ai->written_vars, DECL_UID (var)); if (may_be_aliased (var)) NUM_REFERENCES_INC (ann); } /* Mark variables in V_MAY_DEF operands as being written to. */ FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS) { tree var = DECL_P (op) ? op : SSA_NAME_VAR (op); bitmap_set_bit (ai->written_vars, DECL_UID (var)); } } /* Handle pointer arithmetic EXPR when creating aliasing constraints. Expressions of the type PTR + CST can be handled in two ways: 1- If the constraint for PTR is ADDRESSOF for a non-structure variable, then we can use it directly because adding or subtracting a constant may not alter the original ADDRESSOF constraint (i.e., pointer arithmetic may not legally go outside an object's boundaries). 2- If the constraint for PTR is ADDRESSOF for a structure variable, then if CST is a compile-time constant that can be used as an offset, we can determine which sub-variable will be pointed-to by the expression. Return true if the expression is handled. For any other kind of expression, return false so that each operand can be added as a separate constraint by the caller. */ static bool handle_ptr_arith (struct constraint_expr lhs, tree expr) { tree op0, op1; struct constraint_expr base, offset; if (TREE_CODE (expr) != PLUS_EXPR && TREE_CODE (expr) != MINUS_EXPR) return false; op0 = TREE_OPERAND (expr, 0); op1 = TREE_OPERAND (expr, 1); base = get_constraint_for (op0, NULL); offset.var = anyoffset_id; offset.type = ADDRESSOF; offset.offset = 0; process_constraint (new_constraint (lhs, base)); process_constraint (new_constraint (lhs, offset)); return true; } /* Walk statement T setting up aliasing constraints according to the references found in T. This function is the main part of the constraint builder. AI points to auxiliary alias information used when building alias sets and computing alias grouping heuristics. */ static void find_func_aliases (tree t, struct alias_info *ai) { struct constraint_expr lhs, rhs; /* Update various related attributes like escaped addresses, pointer dereferences for loads and stores. This is used when creating name tags and alias sets. */ update_alias_info (t, ai); /* Now build constraints expressions. */ if (TREE_CODE (t) == PHI_NODE) { /* Only care about pointers and structures containing pointers. */ if (POINTER_TYPE_P (TREE_TYPE (PHI_RESULT (t))) || AGGREGATE_TYPE_P (TREE_TYPE (PHI_RESULT (t)))) { int i; lhs = get_constraint_for (PHI_RESULT (t), NULL); for (i = 0; i < PHI_NUM_ARGS (t); i++) { bool need_anyoffset = false; tree anyoffsetrhs = PHI_ARG_DEF (t, i); rhs = get_constraint_for (PHI_ARG_DEF (t, i), &need_anyoffset); process_constraint (new_constraint (lhs, rhs)); STRIP_NOPS (anyoffsetrhs); /* When taking the address of an aggregate type, from the LHS we can access any field of the RHS. */ if (need_anyoffset || (rhs.type == ADDRESSOF && !(get_varinfo (rhs.var)->is_special_var) && AGGREGATE_TYPE_P (TREE_TYPE (TREE_TYPE (anyoffsetrhs))))) { rhs.var = anyoffset_id; rhs.type = ADDRESSOF; rhs.offset = 0; process_constraint (new_constraint (lhs, rhs)); } } } } else if (TREE_CODE (t) == MODIFY_EXPR) { tree lhsop = TREE_OPERAND (t, 0); tree rhsop = TREE_OPERAND (t, 1); int i; if (AGGREGATE_TYPE_P (TREE_TYPE (lhsop)) && AGGREGATE_TYPE_P (TREE_TYPE (rhsop))) { do_structure_copy (lhsop, rhsop); } else { /* Only care about operations with pointers, structures containing pointers, dereferences, and call expressions. */ if (POINTER_TYPE_P (TREE_TYPE (lhsop)) || AGGREGATE_TYPE_P (TREE_TYPE (lhsop)) || TREE_CODE (rhsop) == CALL_EXPR) { lhs = get_constraint_for (lhsop, NULL); switch (TREE_CODE_CLASS (TREE_CODE (rhsop))) { /* RHS that consist of unary operations, exceptional types, or bare decls/constants, get handled directly by get_constraint_for. */ case tcc_reference: case tcc_declaration: case tcc_constant: case tcc_exceptional: case tcc_expression: case tcc_unary: { tree anyoffsetrhs = rhsop; bool need_anyoffset = false; rhs = get_constraint_for (rhsop, &need_anyoffset); process_constraint (new_constraint (lhs, rhs)); STRIP_NOPS (anyoffsetrhs); /* When taking the address of an aggregate type, from the LHS we can access any field of the RHS. */ if (need_anyoffset || (rhs.type == ADDRESSOF && !(get_varinfo (rhs.var)->is_special_var) && (POINTER_TYPE_P (TREE_TYPE (anyoffsetrhs)) || TREE_CODE (TREE_TYPE (anyoffsetrhs)) == ARRAY_TYPE) && AGGREGATE_TYPE_P (TREE_TYPE (TREE_TYPE (anyoffsetrhs))))) { rhs.var = anyoffset_id; rhs.type = ADDRESSOF; rhs.offset = 0; process_constraint (new_constraint (lhs, rhs)); } } break; case tcc_binary: { /* For pointer arithmetic of the form PTR + CST, we can simply use PTR's constraint because pointer arithmetic is not allowed to go out of bounds. */ if (handle_ptr_arith (lhs, rhsop)) break; } /* FALLTHRU */ /* Otherwise, walk each operand. Notice that we can't use the operand interface because we need to process expressions other than simple operands (e.g. INDIRECT_REF, ADDR_EXPR, CALL_EXPR). */ default: for (i = 0; i < TREE_CODE_LENGTH (TREE_CODE (rhsop)); i++) { tree op = TREE_OPERAND (rhsop, i); rhs = get_constraint_for (op, NULL); process_constraint (new_constraint (lhs, rhs)); } } } } } /* After promoting variables and computing aliasing we will need to re-scan most statements. FIXME: Try to minimize the number of statements re-scanned. It's not really necessary to re-scan *all* statements. */ mark_stmt_modified (t); } /* Find the first varinfo in the same variable as START that overlaps with OFFSET. Effectively, walk the chain of fields for the variable START to find the first field that overlaps with OFFSET. Return NULL if we can't find one. */ static varinfo_t first_vi_for_offset (varinfo_t start, unsigned HOST_WIDE_INT offset) { varinfo_t curr = start; while (curr) { /* We may not find a variable in the field list with the actual offset when when we have glommed a structure to a variable. In that case, however, offset should still be within the size of the variable. */ if (offset >= curr->offset && offset < (curr->offset + curr->size)) return curr; curr = curr->next; } return NULL; } /* Insert the varinfo FIELD into the field list for BASE, ordered by offset. */ static void insert_into_field_list (varinfo_t base, varinfo_t field) { varinfo_t prev = base; varinfo_t curr = base->next; if (curr == NULL) { prev->next = field; field->next = NULL; } else { while (curr) { if (field->offset <= curr->offset) break; prev = curr; curr = curr->next; } field->next = prev->next; prev->next = field; } } /* qsort comparison function for two fieldoff's PA and PB */ static int fieldoff_compare (const void *pa, const void *pb) { const fieldoff_s *foa = (const fieldoff_s *)pa; const fieldoff_s *fob = (const fieldoff_s *)pb; HOST_WIDE_INT foasize, fobsize; if (foa->offset != fob->offset) return foa->offset - fob->offset; foasize = TREE_INT_CST_LOW (DECL_SIZE (foa->field)); fobsize = TREE_INT_CST_LOW (DECL_SIZE (fob->field)); return foasize - fobsize; } /* Sort a fieldstack according to the field offset and sizes. */ void sort_fieldstack (VEC(fieldoff_s,heap) *fieldstack) { qsort (VEC_address (fieldoff_s, fieldstack), VEC_length (fieldoff_s, fieldstack), sizeof (fieldoff_s), fieldoff_compare); } /* Given a TYPE, and a vector of field offsets FIELDSTACK, push all the fields of TYPE onto fieldstack, recording their offsets along the way. OFFSET is used to keep track of the offset in this entire structure, rather than just the immediately containing structure. Returns the number of fields pushed. HAS_UNION is set to true if we find a union type as a field of TYPE. */ int push_fields_onto_fieldstack (tree type, VEC(fieldoff_s,heap) **fieldstack, HOST_WIDE_INT offset, bool *has_union) { tree field; int count = 0; for (field = TYPE_FIELDS (type); field; field = TREE_CHAIN (field)) if (TREE_CODE (field) == FIELD_DECL) { bool push = false; int pushed = 0; if (has_union && (TREE_CODE (TREE_TYPE (field)) == QUAL_UNION_TYPE || TREE_CODE (TREE_TYPE (field)) == UNION_TYPE)) *has_union = true; if (!var_can_have_subvars (field)) push = true; else if (!(pushed = push_fields_onto_fieldstack (TREE_TYPE (field), fieldstack, offset + bitpos_of_field (field), has_union)) && DECL_SIZE (field) && !integer_zerop (DECL_SIZE (field))) /* Empty structures may have actual size, like in C++. So see if we didn't push any subfields and the size is nonzero, push the field onto the stack */ push = true; if (push) { fieldoff_s *pair; pair = VEC_safe_push (fieldoff_s, heap, *fieldstack, NULL); pair->field = field; pair->offset = offset + bitpos_of_field (field); count++; } else count += pushed; } return count; } static void make_constraint_to_anything (varinfo_t vi) { struct constraint_expr lhs, rhs; lhs.var = vi->id; lhs.offset = 0; lhs.type = SCALAR; rhs.var = anything_id; rhs.offset =0 ; rhs.type = ADDRESSOF; process_constraint (new_constraint (lhs, rhs)); } /* Return true if FIELDSTACK contains fields that overlap. FIELDSTACK is assumed to be sorted by offset. */ static bool check_for_overlaps (VEC (fieldoff_s,heap) *fieldstack) { fieldoff_s *fo = NULL; unsigned int i; HOST_WIDE_INT lastoffset = -1; for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++) { if (fo->offset == lastoffset) return true; lastoffset = fo->offset; } return false; } /* Create a varinfo structure for NAME and DECL, and add it to VARMAP. This will also create any varinfo structures necessary for fields of DECL. */ static unsigned int create_variable_info_for (tree decl, const char *name) { unsigned int index = VEC_length (varinfo_t, varmap); varinfo_t vi; tree decltype = TREE_TYPE (decl); bool notokay = false; bool hasunion; bool is_global = DECL_P (decl) ? is_global_var (decl) : false; VEC (fieldoff_s,heap) *fieldstack = NULL; hasunion = TREE_CODE (decltype) == UNION_TYPE || TREE_CODE (decltype) == QUAL_UNION_TYPE; if (var_can_have_subvars (decl) && use_field_sensitive && !hasunion) { push_fields_onto_fieldstack (decltype, &fieldstack, 0, &hasunion); if (hasunion) { VEC_free (fieldoff_s, heap, fieldstack); notokay = true; } } /* If the variable doesn't have subvars, we may end up needing to sort the field list and create fake variables for all the fields. */ vi = new_var_info (decl, index, name, index); vi->decl = decl; vi->offset = 0; vi->has_union = hasunion; if (!TYPE_SIZE (decltype) || TREE_CODE (TYPE_SIZE (decltype)) != INTEGER_CST || TREE_CODE (decltype) == ARRAY_TYPE || TREE_CODE (decltype) == UNION_TYPE || TREE_CODE (decltype) == QUAL_UNION_TYPE) { vi->is_unknown_size_var = true; vi->fullsize = ~0; vi->size = ~0; } else { vi->fullsize = TREE_INT_CST_LOW (TYPE_SIZE (decltype)); vi->size = vi->fullsize; } insert_id_for_tree (vi->decl, index); VEC_safe_push (varinfo_t, heap, varmap, vi); if (is_global) make_constraint_to_anything (vi); stats.total_vars++; if (use_field_sensitive && !notokay && !vi->is_unknown_size_var && var_can_have_subvars (decl) && VEC_length (fieldoff_s, fieldstack) <= MAX_FIELDS_FOR_FIELD_SENSITIVE) { unsigned int newindex = VEC_length (varinfo_t, varmap); fieldoff_s *fo = NULL; unsigned int i; tree field; for (i = 0; !notokay && VEC_iterate (fieldoff_s, fieldstack, i, fo); i++) { if (!DECL_SIZE (fo->field) || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE || fo->offset < 0) { notokay = true; break; } } /* We can't sort them if we have a field with a variable sized type, which will make notokay = true. In that case, we are going to return without creating varinfos for the fields anyway, so sorting them is a waste to boot. */ if (!notokay) { sort_fieldstack (fieldstack); /* Due to some C++ FE issues, like PR 22488, we might end up what appear to be overlapping fields even though they, in reality, do not overlap. Until the C++ FE is fixed, we will simply disable field-sensitivity for these cases. */ notokay = check_for_overlaps (fieldstack); } if (VEC_length (fieldoff_s, fieldstack) != 0) fo = VEC_index (fieldoff_s, fieldstack, 0); if (fo == NULL || notokay) { vi->is_unknown_size_var = 1; vi->fullsize = ~0; vi->size = ~0; VEC_free (fieldoff_s, heap, fieldstack); return index; } field = fo->field; vi->size = TREE_INT_CST_LOW (DECL_SIZE (field)); vi->offset = fo->offset; for (i = 1; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++) { varinfo_t newvi; const char *newname; char *tempname; field = fo->field; newindex = VEC_length (varinfo_t, varmap); asprintf (&tempname, "%s.%s", vi->name, alias_get_name (field)); newname = ggc_strdup (tempname); free (tempname); newvi = new_var_info (decl, newindex, newname, newindex); newvi->offset = fo->offset; newvi->size = TREE_INT_CST_LOW (DECL_SIZE (field)); newvi->fullsize = vi->fullsize; insert_into_field_list (vi, newvi); VEC_safe_push (varinfo_t, heap, varmap, newvi); if (is_global) make_constraint_to_anything (newvi); stats.total_vars++; } VEC_free (fieldoff_s, heap, fieldstack); } return index; } /* Print out the points-to solution for VAR to FILE. */ void dump_solution_for_var (FILE *file, unsigned int var) { varinfo_t vi = get_varinfo (var); unsigned int i; bitmap_iterator bi; fprintf (file, "%s = { ", vi->name); EXECUTE_IF_SET_IN_BITMAP (get_varinfo (vi->node)->solution, 0, i, bi) { fprintf (file, "%s ", get_varinfo (i)->name); } fprintf (file, "}\n"); } /* Print the points-to solution for VAR to stdout. */ void debug_solution_for_var (unsigned int var) { dump_solution_for_var (stdout, var); } /* Create varinfo structures for all of the variables in the function for intraprocedural mode. */ static void intra_create_variable_infos (void) { tree t; /* For each incoming argument arg, ARG = &ANYTHING */ for (t = DECL_ARGUMENTS (current_function_decl); t; t = TREE_CHAIN (t)) { struct constraint_expr lhs; struct constraint_expr rhs; varinfo_t p; lhs.offset = 0; lhs.type = SCALAR; lhs.var = create_variable_info_for (t, alias_get_name (t)); rhs.var = anything_id; rhs.type = ADDRESSOF; rhs.offset = 0; for (p = get_varinfo (lhs.var); p; p = p->next) { struct constraint_expr temp = lhs; temp.var = p->id; process_constraint (new_constraint (temp, rhs)); } } } /* Set bits in INTO corresponding to the variable uids in solution set FROM */ static void set_uids_in_ptset (bitmap into, bitmap from) { unsigned int i; bitmap_iterator bi; bool found_anyoffset = false; subvar_t sv; EXECUTE_IF_SET_IN_BITMAP (from, 0, i, bi) { varinfo_t vi = get_varinfo (i); /* If we find ANYOFFSET in the solution and the solution includes SFTs for some structure, then all the SFTs in that structure will need to be added to the alias set. */ if (vi->id == anyoffset_id) { found_anyoffset = true; continue; } /* The only artificial variables that are allowed in a may-alias set are heap variables. */ if (vi->is_artificial_var && !vi->is_heap_var) continue; if (vi->has_union && get_subvars_for_var (vi->decl) != NULL) { /* Variables containing unions may need to be converted to their SFT's, because SFT's can have unions and we cannot. */ for (sv = get_subvars_for_var (vi->decl); sv; sv = sv->next) bitmap_set_bit (into, DECL_UID (sv->var)); } else if (TREE_CODE (vi->decl) == VAR_DECL || TREE_CODE (vi->decl) == PARM_DECL) { if (found_anyoffset && var_can_have_subvars (vi->decl) && get_subvars_for_var (vi->decl)) { /* If ANYOFFSET is in the solution set and VI->DECL is an aggregate variable with sub-variables, then any of the SFTs inside VI->DECL may have been accessed. Add all the sub-vars for VI->DECL. */ for (sv = get_subvars_for_var (vi->decl); sv; sv = sv->next) bitmap_set_bit (into, DECL_UID (sv->var)); } else if (var_can_have_subvars (vi->decl) && get_subvars_for_var (vi->decl)) { /* If VI->DECL is an aggregate for which we created SFTs, add the SFT corresponding to VI->OFFSET. */ tree sft = get_subvar_at (vi->decl, vi->offset); bitmap_set_bit (into, DECL_UID (sft)); } else { /* Otherwise, just add VI->DECL to the alias set. */ bitmap_set_bit (into, DECL_UID (vi->decl)); } } } } static bool have_alias_info = false; /* Given a pointer variable P, fill in its points-to set, or return false if we can't. */ bool find_what_p_points_to (tree p) { unsigned int id = 0; if (!have_alias_info) return false; if (lookup_id_for_tree (p, &id)) { varinfo_t vi = get_varinfo (id); if (vi->is_artificial_var) return false; /* See if this is a field or a structure. */ if (vi->size != vi->fullsize) { /* Nothing currently asks about structure fields directly, but when they do, we need code here to hand back the points-to set. */ if (!var_can_have_subvars (vi->decl) || get_subvars_for_var (vi->decl) == NULL) return false; } else { struct ptr_info_def *pi = get_ptr_info (p); unsigned int i; bitmap_iterator bi; /* This variable may have been collapsed, let's get the real variable. */ vi = get_varinfo (vi->node); /* Translate artificial variables into SSA_NAME_PTR_INFO attributes. */ EXECUTE_IF_SET_IN_BITMAP (vi->solution, 0, i, bi) { varinfo_t vi = get_varinfo (i); if (vi->is_artificial_var) { /* FIXME. READONLY should be handled better so that flow insensitive aliasing can disregard writable aliases. */ if (vi->id == nothing_id) pi->pt_null = 1; else if (vi->id == anything_id) pi->pt_anything = 1; else if (vi->id == readonly_id) pi->pt_anything = 1; else if (vi->id == integer_id) pi->pt_anything = 1; else if (vi->is_heap_var) pi->pt_global_mem = 1; } } if (pi->pt_anything) return false; if (!pi->pt_vars) pi->pt_vars = BITMAP_GGC_ALLOC (); set_uids_in_ptset (pi->pt_vars, vi->solution); if (bitmap_empty_p (pi->pt_vars)) pi->pt_vars = NULL; return true; } } return false; } /* Initialize things necessary to perform PTA */ static void init_alias_vars (void) { bitmap_obstack_initialize (&ptabitmap_obstack); } /* Dump points-to information to OUTFILE. */ void dump_sa_points_to_info (FILE *outfile) { unsigned int i; fprintf (outfile, "\nPoints-to sets\n\n"); if (dump_flags & TDF_STATS) { fprintf (outfile, "Stats:\n"); fprintf (outfile, "Total vars: %d\n", stats.total_vars); fprintf (outfile, "Statically unified vars: %d\n", stats.unified_vars_static); fprintf (outfile, "Collapsed vars: %d\n", stats.collapsed_vars); fprintf (outfile, "Dynamically unified vars: %d\n", stats.unified_vars_dynamic); fprintf (outfile, "Iterations: %d\n", stats.iterations); } for (i = 0; i < VEC_length (varinfo_t, varmap); i++) dump_solution_for_var (outfile, i); } /* Debug points-to information to stderr. */ void debug_sa_points_to_info (void) { dump_sa_points_to_info (stderr); } /* Initialize the always-existing constraint variables for NULL ANYTHING, READONLY, and INTEGER */ static void init_base_vars (void) { struct constraint_expr lhs, rhs; /* Create the NULL variable, used to represent that a variable points to NULL. */ nothing_tree = create_tmp_var_raw (void_type_node, "NULL"); var_nothing = new_var_info (nothing_tree, 0, "NULL", 0); insert_id_for_tree (nothing_tree, 0); var_nothing->is_artificial_var = 1; var_nothing->offset = 0; var_nothing->size = ~0; var_nothing->fullsize = ~0; var_nothing->is_special_var = 1; nothing_id = 0; VEC_safe_push (varinfo_t, heap, varmap, var_nothing); /* Create the ANYTHING variable, used to represent that a variable points to some unknown piece of memory. */ anything_tree = create_tmp_var_raw (void_type_node, "ANYTHING"); var_anything = new_var_info (anything_tree, 1, "ANYTHING", 1); insert_id_for_tree (anything_tree, 1); var_anything->is_artificial_var = 1; var_anything->size = ~0; var_anything->offset = 0; var_anything->next = NULL; var_anything->fullsize = ~0; var_anything->is_special_var = 1; anything_id = 1; /* Anything points to anything. This makes deref constraints just work in the presence of linked list and other p = *p type loops, by saying that *ANYTHING = ANYTHING. */ VEC_safe_push (varinfo_t, heap, varmap, var_anything); lhs.type = SCALAR; lhs.var = anything_id; lhs.offset = 0; rhs.type = ADDRESSOF; rhs.var = anything_id; rhs.offset = 0; var_anything->address_taken = true; /* This specifically does not use process_constraint because process_constraint ignores all anything = anything constraints, since all but this one are redundant. */ VEC_safe_push (constraint_t, heap, constraints, new_constraint (lhs, rhs)); /* Create the READONLY variable, used to represent that a variable points to readonly memory. */ readonly_tree = create_tmp_var_raw (void_type_node, "READONLY"); var_readonly = new_var_info (readonly_tree, 2, "READONLY", 2); var_readonly->is_artificial_var = 1; var_readonly->offset = 0; var_readonly->size = ~0; var_readonly->fullsize = ~0; var_readonly->next = NULL; var_readonly->is_special_var = 1; insert_id_for_tree (readonly_tree, 2); readonly_id = 2; VEC_safe_push (varinfo_t, heap, varmap, var_readonly); /* readonly memory points to anything, in order to make deref easier. In reality, it points to anything the particular readonly variable can point to, but we don't track this separately. */ lhs.type = SCALAR; lhs.var = readonly_id; lhs.offset = 0; rhs.type = ADDRESSOF; rhs.var = anything_id; rhs.offset = 0; process_constraint (new_constraint (lhs, rhs)); /* Create the INTEGER variable, used to represent that a variable points to an INTEGER. */ integer_tree = create_tmp_var_raw (void_type_node, "INTEGER"); var_integer = new_var_info (integer_tree, 3, "INTEGER", 3); insert_id_for_tree (integer_tree, 3); var_integer->is_artificial_var = 1; var_integer->size = ~0; var_integer->fullsize = ~0; var_integer->offset = 0; var_integer->next = NULL; var_integer->is_special_var = 1; integer_id = 3; VEC_safe_push (varinfo_t, heap, varmap, var_integer); /* *INTEGER = ANYTHING, because we don't know where a dereference of a random integer will point to. */ lhs.type = SCALAR; lhs.var = integer_id; lhs.offset = 0; rhs.type = ADDRESSOF; rhs.var = anything_id; rhs.offset = 0; process_constraint (new_constraint (lhs, rhs)); /* Create the ANYOFFSET variable, used to represent an arbitrary offset inside an object. This is similar to ANYTHING, but less drastic. It means that the pointer can point anywhere inside an object, but not outside of it. */ anyoffset_tree = create_tmp_var_raw (void_type_node, "ANYOFFSET"); anyoffset_id = 4; var_anyoffset = new_var_info (anyoffset_tree, anyoffset_id, "ANYOFFSET", anyoffset_id); insert_id_for_tree (anyoffset_tree, anyoffset_id); var_anyoffset->is_artificial_var = 1; var_anyoffset->size = ~0; var_anyoffset->offset = 0; var_anyoffset->next = NULL; var_anyoffset->fullsize = ~0; var_anyoffset->is_special_var = 1; VEC_safe_push (varinfo_t, heap, varmap, var_anyoffset); /* ANYOFFSET points to ANYOFFSET. */ lhs.type = SCALAR; lhs.var = anyoffset_id; lhs.offset = 0; rhs.type = ADDRESSOF; rhs.var = anyoffset_id; rhs.offset = 0; process_constraint (new_constraint (lhs, rhs)); } /* Return true if we actually need to solve the constraint graph in order to get our points-to sets. This is false when, for example, no addresses are taken other than special vars, or all points-to sets with members already contain the anything variable and there are no predecessors for other sets. */ static bool need_to_solve (void) { int i; varinfo_t v; bool found_address_taken = false; bool found_non_anything = false; for (i = 0; VEC_iterate (varinfo_t, varmap, i, v); i++) { if (v->is_special_var) continue; if (v->address_taken) found_address_taken = true; if (v->solution && !bitmap_empty_p (v->solution) && !bitmap_bit_p (v->solution, anything_id)) found_non_anything = true; else if (bitmap_empty_p (v->solution) && VEC_length (constraint_edge_t, graph->preds[v->id]) != 0) found_non_anything = true; if (found_address_taken && found_non_anything) return true; } return false; } /* Create points-to sets for the current function. See the comments at the start of the file for an algorithmic overview. */ void compute_points_to_sets (struct alias_info *ai) { basic_block bb; timevar_push (TV_TREE_PTA); init_alias_vars (); constraint_pool = create_alloc_pool ("Constraint pool", sizeof (struct constraint), 30); variable_info_pool = create_alloc_pool ("Variable info pool", sizeof (struct variable_info), 30); constraint_edge_pool = create_alloc_pool ("Constraint edges", sizeof (struct constraint_edge), 30); constraints = VEC_alloc (constraint_t, heap, 8); varmap = VEC_alloc (varinfo_t, heap, 8); id_for_tree = htab_create (10, tree_id_hash, tree_id_eq, free); memset (&stats, 0, sizeof (stats)); init_base_vars (); intra_create_variable_infos (); /* Now walk all statements and derive aliases. */ FOR_EACH_BB (bb) { block_stmt_iterator bsi; tree phi; for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi)) if (is_gimple_reg (PHI_RESULT (phi))) find_func_aliases (phi, ai); for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) find_func_aliases (bsi_stmt (bsi), ai); } build_constraint_graph (); if (dump_file) { fprintf (dump_file, "Points-to analysis\n\nConstraints:\n\n"); dump_constraints (dump_file); } if (need_to_solve ()) { if (dump_file) fprintf (dump_file, "\nCollapsing static cycles and doing variable " "substitution:\n"); find_and_collapse_graph_cycles (graph, false); perform_var_substitution (graph); if (dump_file) fprintf (dump_file, "\nSolving graph:\n"); solve_graph (graph); } if (dump_file) dump_sa_points_to_info (dump_file); have_alias_info = true; timevar_pop (TV_TREE_PTA); } /* Delete created points-to sets. */ void delete_points_to_sets (void) { varinfo_t v; int i; htab_delete (id_for_tree); bitmap_obstack_release (&ptabitmap_obstack); VEC_free (constraint_t, heap, constraints); for (i = 0; VEC_iterate (varinfo_t, varmap, i, v); i++) { VEC_free (constraint_edge_t, heap, graph->succs[i]); VEC_free (constraint_edge_t, heap, graph->preds[i]); VEC_free (constraint_t, heap, v->complex); } free (graph->succs); free (graph->preds); free (graph); VEC_free (varinfo_t, heap, varmap); free_alloc_pool (variable_info_pool); free_alloc_pool (constraint_pool); free_alloc_pool (constraint_edge_pool); have_alias_info = false; } /* Initialize the heapvar for statement mapping. */ void init_alias_heapvars (void) { heapvar_for_stmt = htab_create_ggc (11, tree_map_hash, tree_map_eq, NULL); } void delete_alias_heapvars (void) { htab_delete (heapvar_for_stmt); } #include "gt-tree-ssa-structalias.h"
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