/* Common block and equivalence list handling Copyright (C) 2000, 2003, 2004 Free Software Foundation, Inc. Contributed by Canqun Yang This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /* The core algorithm is based on Andy Vaught's g95 tree. Also the way to build UNION_TYPE is borrowed from Richard Henderson. Transform common blocks. An integral part of this is processing equvalence variables. Equivalenced variables that are not in a common block end up in a private block of their own. Each common block or local equivalence list is declared as a union. Variables within the block are represented as a field within the block with the proper offset. So if two variables are equivalenced, they just point to a common area in memory. Mathematically, laying out an equivalence block is equivalent to solving a linear system of equations. The matrix is usually a sparse matrix in which each row contains all zero elements except for a +1 and a -1, a sort of a generalized Vandermonde matrix. The matrix is usually block diagonal. The system can be overdetermined, underdetermined or have a unique solution. If the system is inconsistent, the program is not standard conforming. The solution vector is integral, since all of the pivots are +1 or -1. How we lay out an equivalence block is a little less complicated. In an equivalence list with n elements, there are n-1 conditions to be satisfied. The conditions partition the variables into what we will call segments. If A and B are equivalenced then A and B are in the same segment. If B and C are equivalenced as well, then A, B and C are in a segment and so on. Each segment is a block of memory that has one or more variables equivalenced in some way. A common block is made up of a series of segments that are joined one after the other. In the linear system, a segment is a block diagonal. To lay out a segment we first start with some variable and determine its length. The first variable is assumed to start at offset one and extends to however long it is. We then traverse the list of equivalences to find an unused condition that involves at least one of the variables currently in the segment. Each equivalence condition amounts to the condition B+b=C+c where B and C are the offsets of the B and C variables, and b and c are constants which are nonzero for array elements, substrings or structure components. So for EQUIVALENCE(B(2), C(3)) we have B + 2*size of B's elements = C + 3*size of C's elements. If B and C are known we check to see if the condition already holds. If B is known we can solve for C. Since we know the length of C, we can see if the minimum and maximum extents of the segment are affected. Eventually, we make a full pass through the equivalence list without finding any new conditions and the segment is fully specified. At this point, the segment is added to the current common block. Since we know the minimum extent of the segment, everything in the segment is translated to its position in the common block. The usual case here is that there are no equivalence statements and the common block is series of segments with one variable each, which is a diagonal matrix in the matrix formulation. Each segment is described by a chain of segment_info structures. Each segment_info structure describes the extents of a single varible within the segment. This list is maintained in the order the elements are positioned withing the segment. If two elements have the same starting offset the smaller will come first. If they also have the same size their ordering is undefined. Once all common blocks have been created, the list of equivalences is examined for still-unused equivalence conditions. We create a block for each merged equivalence list. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tree.h" #include "toplev.h" #include "tm.h" #include "gfortran.h" #include "trans.h" #include "trans-types.h" #include "trans-const.h" #include /* Holds a single variable in a equivalence set. */ typedef struct segment_info { gfc_symbol *sym; HOST_WIDE_INT offset; HOST_WIDE_INT length; /* This will contain the field type until the field is created. */ tree field; struct segment_info *next; } segment_info; static segment_info *current_segment, *current_common; static HOST_WIDE_INT current_offset; static gfc_namespace *gfc_common_ns = NULL; #define BLANK_COMMON_NAME "__BLNK__" /* Make a segment_info based on a symbol. */ static segment_info * get_segment_info (gfc_symbol * sym, HOST_WIDE_INT offset) { segment_info *s; /* Make sure we've got the character length. */ if (sym->ts.type == BT_CHARACTER) gfc_conv_const_charlen (sym->ts.cl); /* Create the segment_info and fill it in. */ s = (segment_info *) gfc_getmem (sizeof (segment_info)); s->sym = sym; /* We will use this type when building the segment aggreagate type. */ s->field = gfc_sym_type (sym); s->length = int_size_in_bytes (s->field); s->offset = offset; return s; } /* Add combine segment V and segment LIST. */ static segment_info * add_segments (segment_info *list, segment_info *v) { segment_info *s; segment_info *p; segment_info *next; p = NULL; s = list; while (v) { /* Find the location of the new element. */ while (s) { if (v->offset < s->offset) break; if (v->offset == s->offset && v->length <= s->length) break; p = s; s = s->next; } /* Insert the new element in between p and s. */ next = v->next; v->next = s; if (p == NULL) list = v; else p->next = v; p = v; v = next; } return list; } /* Construct mangled common block name from symbol name. */ static tree gfc_sym_mangled_common_id (const char *name) { int has_underscore; char mangled_name[GFC_MAX_MANGLED_SYMBOL_LEN + 1]; if (strcmp (name, BLANK_COMMON_NAME) == 0) return get_identifier (name); if (gfc_option.flag_underscoring) { has_underscore = strchr (name, '_') != 0; if (gfc_option.flag_second_underscore && has_underscore) snprintf (mangled_name, sizeof mangled_name, "%s__", name); else snprintf (mangled_name, sizeof mangled_name, "%s_", name); return get_identifier (mangled_name); } else return get_identifier (name); } /* Build a field declaration for a common variable or a local equivalence object. */ static void build_field (segment_info *h, tree union_type, record_layout_info rli) { tree field; tree name; HOST_WIDE_INT offset = h->offset; unsigned HOST_WIDE_INT desired_align, known_align; name = get_identifier (h->sym->name); field = build_decl (FIELD_DECL, name, h->field); known_align = (offset & -offset) * BITS_PER_UNIT; if (known_align == 0 || known_align > BIGGEST_ALIGNMENT) known_align = BIGGEST_ALIGNMENT; desired_align = update_alignment_for_field (rli, field, known_align); if (desired_align > known_align) DECL_PACKED (field) = 1; DECL_FIELD_CONTEXT (field) = union_type; DECL_FIELD_OFFSET (field) = size_int (offset); DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node; SET_DECL_OFFSET_ALIGN (field, known_align); rli->offset = size_binop (MAX_EXPR, rli->offset, size_binop (PLUS_EXPR, DECL_FIELD_OFFSET (field), DECL_SIZE_UNIT (field))); h->field = field; } /* Get storage for local equivalence. */ static tree build_equiv_decl (tree union_type, bool is_init) { tree decl; if (is_init) { decl = gfc_create_var (union_type, "equiv"); TREE_STATIC (decl) = 1; return decl; } decl = build_decl (VAR_DECL, NULL, union_type); DECL_ARTIFICIAL (decl) = 1; DECL_COMMON (decl) = 1; TREE_ADDRESSABLE (decl) = 1; TREE_USED (decl) = 1; gfc_add_decl_to_function (decl); return decl; } /* Get storage for common block. */ static tree build_common_decl (gfc_common_head *com, tree union_type, bool is_init) { gfc_symbol *common_sym; tree decl; /* Create a namespace to store symbols for common blocks. */ if (gfc_common_ns == NULL) gfc_common_ns = gfc_get_namespace (NULL); gfc_get_symbol (com->name, gfc_common_ns, &common_sym); decl = common_sym->backend_decl; /* Update the size of this common block as needed. */ if (decl != NULL_TREE) { tree size = TYPE_SIZE_UNIT (union_type); if (tree_int_cst_lt (DECL_SIZE_UNIT (decl), size)) { /* Named common blocks of the same name shall be of the same size in all scoping units of a program in which they appear, but blank common blocks may be of different sizes. */ if (strcmp (com->name, BLANK_COMMON_NAME)) gfc_warning ("Named COMMON block '%s' at %L shall be of the " "same size", com->name, &com->where); DECL_SIZE_UNIT (decl) = size; } } /* If this common block has been declared in a previous program unit, and either it is already initialized or there is no new initialization for it, just return. */ if ((decl != NULL_TREE) && (!is_init || DECL_INITIAL (decl))) return decl; /* If there is no backend_decl for the common block, build it. */ if (decl == NULL_TREE) { decl = build_decl (VAR_DECL, get_identifier (com->name), union_type); SET_DECL_ASSEMBLER_NAME (decl, gfc_sym_mangled_common_id (com->name)); TREE_PUBLIC (decl) = 1; TREE_STATIC (decl) = 1; DECL_ALIGN (decl) = BIGGEST_ALIGNMENT; DECL_USER_ALIGN (decl) = 0; /* Place the back end declaration for this common block in GLOBAL_BINDING_LEVEL. */ common_sym->backend_decl = pushdecl_top_level (decl); } /* Has no initial values. */ if (!is_init) { DECL_INITIAL (decl) = NULL_TREE; DECL_COMMON (decl) = 1; DECL_DEFER_OUTPUT (decl) = 1; } else { DECL_INITIAL (decl) = error_mark_node; DECL_COMMON (decl) = 0; DECL_DEFER_OUTPUT (decl) = 0; } return decl; } /* Declare memory for the common block or local equivalence, and create backend declarations for all of the elements. */ static void create_common (gfc_common_head *com) { segment_info *s, *next_s; tree union_type; tree *field_link; record_layout_info rli; tree decl; bool is_init = false; /* Declare the variables inside the common block. */ union_type = make_node (UNION_TYPE); rli = start_record_layout (union_type); field_link = &TYPE_FIELDS (union_type); for (s = current_common; s; s = s->next) { build_field (s, union_type, rli); /* Link the field into the type. */ *field_link = s->field; field_link = &TREE_CHAIN (s->field); /* Has initial value. */ if (s->sym->value) is_init = true; } finish_record_layout (rli, true); if (com) decl = build_common_decl (com, union_type, is_init); else decl = build_equiv_decl (union_type, is_init); if (is_init) { tree list, ctor, tmp; HOST_WIDE_INT offset = 0; list = NULL_TREE; for (s = current_common; s; s = s->next) { if (s->sym->value) { if (s->offset < offset) { /* We have overlapping initializers. It could either be partially initilalized arrays (legal), or the user specified multiple initial values (illegal). We don't implement this yet, so bail out. */ gfc_todo_error ("Initialization of overlapping variables"); } /* Add the initializer for this field. */ tmp = gfc_conv_initializer (s->sym->value, &s->sym->ts, TREE_TYPE (s->field), s->sym->attr.dimension, s->sym->attr.pointer || s->sym->attr.allocatable); list = tree_cons (s->field, tmp, list); offset = s->offset + s->length; } } assert (list); ctor = build1 (CONSTRUCTOR, union_type, nreverse(list)); TREE_CONSTANT (ctor) = 1; TREE_INVARIANT (ctor) = 1; TREE_STATIC (ctor) = 1; DECL_INITIAL (decl) = ctor; #ifdef ENABLE_CHECKING for (tmp = CONSTRUCTOR_ELTS (ctor); tmp; tmp = TREE_CHAIN (tmp)) assert (TREE_CODE (TREE_PURPOSE (tmp)) == FIELD_DECL); #endif } /* Build component reference for each variable. */ for (s = current_common; s; s = next_s) { s->sym->backend_decl = build (COMPONENT_REF, TREE_TYPE (s->field), decl, s->field, NULL_TREE); next_s = s->next; gfc_free (s); } } /* Given a symbol, find it in the current segment list. Returns NULL if not found. */ static segment_info * find_segment_info (gfc_symbol *symbol) { segment_info *n; for (n = current_segment; n; n = n->next) { if (n->sym == symbol) return n; } return NULL; } /* Given an expression node, make sure it is a constant integer and return the mpz_t value. */ static mpz_t * get_mpz (gfc_expr *e) { if (e->expr_type != EXPR_CONSTANT) gfc_internal_error ("get_mpz(): Not an integer constant"); return &e->value.integer; } /* Given an array specification and an array reference, figure out the array element number (zero based). Bounds and elements are guaranteed to be constants. If something goes wrong we generate an error and return zero. */ static HOST_WIDE_INT element_number (gfc_array_ref *ar) { mpz_t multiplier, offset, extent, n; gfc_array_spec *as; HOST_WIDE_INT i, rank; as = ar->as; rank = as->rank; mpz_init_set_ui (multiplier, 1); mpz_init_set_ui (offset, 0); mpz_init (extent); mpz_init (n); for (i = 0; i < rank; i++) { if (ar->dimen_type[i] != DIMEN_ELEMENT) gfc_internal_error ("element_number(): Bad dimension type"); mpz_sub (n, *get_mpz (ar->start[i]), *get_mpz (as->lower[i])); mpz_mul (n, n, multiplier); mpz_add (offset, offset, n); mpz_sub (extent, *get_mpz (as->upper[i]), *get_mpz (as->lower[i])); mpz_add_ui (extent, extent, 1); if (mpz_sgn (extent) < 0) mpz_set_ui (extent, 0); mpz_mul (multiplier, multiplier, extent); } i = mpz_get_ui (offset); mpz_clear (multiplier); mpz_clear (offset); mpz_clear (extent); mpz_clear (n); return i; } /* Given a single element of an equivalence list, figure out the offset from the base symbol. For simple variables or full arrays, this is simply zero. For an array element we have to calculate the array element number and multiply by the element size. For a substring we have to calculate the further reference. */ static HOST_WIDE_INT calculate_offset (gfc_expr *e) { HOST_WIDE_INT n, element_size, offset; gfc_typespec *element_type; gfc_ref *reference; offset = 0; element_type = &e->symtree->n.sym->ts; for (reference = e->ref; reference; reference = reference->next) switch (reference->type) { case REF_ARRAY: switch (reference->u.ar.type) { case AR_FULL: break; case AR_ELEMENT: n = element_number (&reference->u.ar); if (element_type->type == BT_CHARACTER) gfc_conv_const_charlen (element_type->cl); element_size = int_size_in_bytes (gfc_typenode_for_spec (element_type)); offset += n * element_size; break; default: gfc_error ("Bad array reference at %L", &e->where); } break; case REF_SUBSTRING: if (reference->u.ss.start != NULL) offset += mpz_get_ui (*get_mpz (reference->u.ss.start)) - 1; break; default: gfc_error ("Illegal reference type at %L as EQUIVALENCE object", &e->where); } return offset; } /* Add a new segment_info structure to the current segment. eq1 is already in the list, eq2 is not. */ static void new_condition (segment_info *v, gfc_equiv *eq1, gfc_equiv *eq2) { HOST_WIDE_INT offset1, offset2; segment_info *a; offset1 = calculate_offset (eq1->expr); offset2 = calculate_offset (eq2->expr); a = get_segment_info (eq2->expr->symtree->n.sym, v->offset + offset1 - offset2); current_segment = add_segments (current_segment, a); } /* Given two equivalence structures that are both already in the list, make sure that this new condition is not violated, generating an error if it is. */ static void confirm_condition (segment_info *s1, gfc_equiv *eq1, segment_info *s2, gfc_equiv *eq2) { HOST_WIDE_INT offset1, offset2; offset1 = calculate_offset (eq1->expr); offset2 = calculate_offset (eq2->expr); if (s1->offset + offset1 != s2->offset + offset2) gfc_error ("Inconsistent equivalence rules involving '%s' at %L and " "'%s' at %L", s1->sym->name, &s1->sym->declared_at, s2->sym->name, &s2->sym->declared_at); } /* Process a new equivalence condition. eq1 is know to be in segment f. If eq2 is also present then confirm that the condition holds. Otherwise add a new variable to the segment list. */ static void add_condition (segment_info *f, gfc_equiv *eq1, gfc_equiv *eq2) { segment_info *n; n = find_segment_info (eq2->expr->symtree->n.sym); if (n == NULL) new_condition (f, eq1, eq2); else confirm_condition (f, eq1, n, eq2); } /* Given a segment element, search through the equivalence lists for unused conditions that involve the symbol. Add these rules to the segment. Only checks for rules involving the first symbol in the equivalence set. */ static bool find_equivalence (segment_info *n) { gfc_equiv *e1, *e2, *eq, *other; bool found; found = FALSE; for (e1 = n->sym->ns->equiv; e1; e1 = e1->next) { other = NULL; for (e2 = e1->eq; e2; e2 = e2->eq) { if (e2->used) continue; if (e1->expr->symtree->n.sym == n->sym) { eq = e1; other = e2; } else if (e2->expr->symtree->n.sym == n->sym) { eq = e2; other = e1; } else eq = NULL; if (eq) { add_condition (n, eq, other); eq->used = 1; found = TRUE; /* If this symbol is the first in the chain we may find other matches. Otherwise we can skip to the next equivalence. */ if (eq == e2) break; } } } return found; } /* Add all symbols equivalenced within a segment. We need to scan the segment list multiple times to include indirect equivalences. */ static void add_equivalences (void) { segment_info *f; bool more; more = TRUE; while (more) { more = FALSE; for (f = current_segment; f; f = f->next) { if (!f->sym->equiv_built) { f->sym->equiv_built = 1; more = find_equivalence (f); } } } } /* Given a seed symbol, create a new segment consisting of that symbol and all of the symbols equivalenced with that symbol. */ static void new_segment (gfc_common_head *common, gfc_symbol *sym) { current_segment = get_segment_info (sym, current_offset); /* The offset of the next common variable. */ current_offset += current_segment->length; /* Add all object directly or indirectly equivalenced with this common variable. */ add_equivalences (); if (current_segment->offset < 0) gfc_error ("The equivalence set for '%s' cause an invalid " "extension to COMMON '%s' at %L", sym->name, common->name, &common->where); /* Add these to the common block. */ current_common = add_segments (current_common, current_segment); } /* Create a new block for each merged equivalence list. */ static void finish_equivalences (gfc_namespace *ns) { gfc_equiv *z, *y; gfc_symbol *sym; segment_info *v; HOST_WIDE_INT min_offset; for (z = ns->equiv; z; z = z->next) for (y = z->eq; y; y = y->eq) { if (y->used) continue; sym = z->expr->symtree->n.sym; current_segment = get_segment_info (sym, 0); /* All objects directly or indrectly equivalenced with this symbol. */ add_equivalences (); /* Calculate the minimal offset. */ min_offset = current_segment->offset; /* Adjust the offset of each equivalence object. */ for (v = current_segment; v; v = v->next) v->offset -= min_offset; current_common = current_segment; create_common (NULL); break; } } /* Translate a single common block. */ static void translate_common (gfc_common_head *common, gfc_symbol *var_list) { gfc_symbol *sym; current_common = NULL; current_offset = 0; /* Add symbols to the segment. */ for (sym = var_list; sym; sym = sym->common_next) { if (! sym->equiv_built) new_segment (common, sym); } create_common (common); } /* Work function for translating a named common block. */ static void named_common (gfc_symtree *st) { translate_common (st->n.common, st->n.common->head); } /* Translate the common blocks in a namespace. Unlike other variables, these have to be created before code, because the backend_decl depends on the rest of the common block. */ void gfc_trans_common (gfc_namespace *ns) { gfc_common_head *c; /* Translate the blank common block. */ if (ns->blank_common.head != NULL) { c = gfc_get_common_head (); strcpy (c->name, BLANK_COMMON_NAME); translate_common (c, ns->blank_common.head); } /* Translate all named common blocks. */ gfc_traverse_symtree (ns->common_root, named_common); /* Commit the newly created symbols for common blocks. */ gfc_commit_symbols (); /* Translate local equivalence. */ finish_equivalences (ns); }