/* Common block and equivalence list handling Copyright (C) 2000, 2003 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. 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" typedef struct segment_info { gfc_symbol *sym; int offset; int length; tree field; struct segment_info *next; } segment_info; static segment_info *current_segment, *current_common; static int current_length, current_offset; static gfc_namespace *gfc_common_ns = NULL; #define get_segment_info() gfc_getmem (sizeof (segment_info)) #define BLANK_COMMON_NAME "__BLNK__" /* Construct mangled common block name from symbol name. */ static tree gfc_sym_mangled_common_id (gfc_symbol *sym) { int has_underscore; char name[GFC_MAX_MANGLED_SYMBOL_LEN + 1]; if (strcmp (sym->name, BLANK_COMMON_NAME) == 0) return get_identifier (sym->name); if (gfc_option.flag_underscoring) { has_underscore = strchr (sym->name, '_') != 0; if (gfc_option.flag_second_underscore && has_underscore) snprintf (name, sizeof name, "%s__", sym->name); else snprintf (name, sizeof name, "%s_", sym->name); return get_identifier (name); } else return get_identifier (sym->name); } /* Build a filed declaration for a common variable or a local equivalence object. */ static tree build_field (segment_info *h, tree union_type, record_layout_info rli) { tree type = gfc_sym_type (h->sym); tree name = get_identifier (h->sym->name); tree field = build_decl (FIELD_DECL, name, type); HOST_WIDE_INT offset = h->offset; unsigned int desired_align, known_align; 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))); return field; } /* Get storage for local equivalence. */ static tree build_equiv_decl (tree union_type, bool is_init) { tree decl; decl = build_decl (VAR_DECL, NULL, union_type); DECL_ARTIFICIAL (decl) = 1; if (is_init) DECL_COMMON (decl) = 0; else 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_symbol *sym, 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 (sym->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 = build_int_2 (current_length, 0); 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 (sym->name, BLANK_COMMON_NAME)) gfc_warning ("named COMMON block '%s' at %L shall be of the " "same size", sym->name, &sym->declared_at); 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 (sym->name), union_type); SET_DECL_ASSEMBLER_NAME (decl, gfc_sym_mangled_common_id (sym)); TREE_PUBLIC (decl) = 1; TREE_STATIC (decl) = 1; DECL_ALIGN (decl) = BIGGEST_ALIGNMENT; DECL_USER_ALIGN (decl) = 0; } /* Has no initial values. */ if (!is_init) { DECL_INITIAL (decl) = NULL_TREE; DECL_COMMON (decl) = 1; DECL_DEFER_OUTPUT (decl) = 1; /* Place the back end declaration for this common block in GLOBAL_BINDING_LEVEL. */ common_sym->backend_decl = pushdecl_top_level (decl); } else { DECL_INITIAL (decl) = error_mark_node; DECL_COMMON (decl) = 0; DECL_DEFER_OUTPUT (decl) = 0; common_sym->backend_decl = decl; } 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_symbol *sym) { segment_info *h, *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 (h = current_common; h; h = next_s) { tree field; field = build_field (h, union_type, rli); /* Link the field into the type. */ *field_link = field; field_link = &TREE_CHAIN (field); h->field = field; /* Has initial value. */ if (h->sym->value) is_init = true; next_s = h->next; } finish_record_layout (rli, true); if (is_init) gfc_todo_error ("initial values for COMMON or EQUIVALENCE"); if (sym) decl = build_common_decl (sym, union_type, is_init); else decl = build_equiv_decl (union_type, is_init); /* Build component reference for each variable. */ for (h = current_common; h; h = next_s) { h->sym->backend_decl = build (COMPONENT_REF, TREE_TYPE (h->field), decl, h->field); next_s = h->next; gfc_free (h); } } /* 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 a variable symbol, calculate the total length in bytes of the variable. */ static int calculate_length (gfc_symbol *symbol) { int j, element_size; mpz_t elements; if (symbol->ts.type == BT_CHARACTER) gfc_conv_const_charlen (symbol->ts.cl); element_size = int_size_in_bytes (gfc_typenode_for_spec (&symbol->ts)); if (symbol->as == NULL) return element_size; /* Calculate the number of elements in the array */ if (spec_size (symbol->as, &elements) == FAILURE) gfc_internal_error ("calculate_length(): Unable to determine array size"); j = mpz_get_ui (elements); mpz_clear (elements); return j*element_size;; } /* Given an expression node, make sure it is a constant integer and return the mpz_t value. */ static mpz_t * get_mpz (gfc_expr *g) { if (g->expr_type != EXPR_CONSTANT) gfc_internal_error ("get_mpz(): Not an integer constant"); return &g->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 int element_number (gfc_array_ref *ar) { mpz_t multiplier, offset, extent, l; gfc_array_spec *as; int b, rank; as = ar->as; rank = as->rank; mpz_init_set_ui (multiplier, 1); mpz_init_set_ui (offset, 0); mpz_init (extent); mpz_init (l); for (b = 0; b < rank; b++) { if (ar->dimen_type[b] != DIMEN_ELEMENT) gfc_internal_error ("element_number(): Bad dimension type"); mpz_sub (l, *get_mpz (ar->start[b]), *get_mpz (as->lower[b])); mpz_mul (l, l, multiplier); mpz_add (offset, offset, l); mpz_sub (extent, *get_mpz (as->upper[b]), *get_mpz (as->lower[b])); mpz_add_ui (extent, extent, 1); if (mpz_sgn (extent) < 0) mpz_set_ui (extent, 0); mpz_mul (multiplier, multiplier, extent); } b = mpz_get_ui (offset); mpz_clear (multiplier); mpz_clear (offset); mpz_clear (extent); mpz_clear (l); return b; } /* 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 int calculate_offset (gfc_expr *s) { int a, element_size, offset; gfc_typespec *element_type; gfc_ref *reference; offset = 0; element_type = &s->symtree->n.sym->ts; for (reference = s->ref; reference; reference = reference->next) switch (reference->type) { case REF_ARRAY: switch (reference->u.ar.type) { case AR_FULL: break; case AR_ELEMENT: a = 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 += a * element_size; break; default: gfc_error ("bad array reference at %L", &s->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", &s->where); } return offset; } /* Add a new segment_info structure to the current eq1 is already in the list at s1, eq2 is not. */ static void new_condition (segment_info *v, gfc_equiv *eq1, gfc_equiv *eq2) { int offset1, offset2; segment_info *a; offset1 = calculate_offset (eq1->expr); offset2 = calculate_offset (eq2->expr); a = get_segment_info (); a->sym = eq2->expr->symtree->n.sym; a->offset = v->offset + offset1 - offset2; a->length = calculate_length (eq2->expr->symtree->n.sym); a->next = current_segment; 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 *k, gfc_equiv *eq1, segment_info *e, gfc_equiv *eq2) { int offset1, offset2; offset1 = calculate_offset (eq1->expr); offset2 = calculate_offset (eq2->expr); if (k->offset + offset1 != e->offset + offset2) gfc_error ("inconsistent equivalence rules involving '%s' at %L and " "'%s' at %L", k->sym->name, &k->sym->declared_at, e->sym->name, &e->sym->declared_at); } /* At this point we have a new equivalence condition to process. If both variables are already present, then we are confirming that the condition holds. Otherwise we are adding a new variable to the segment list. */ static void add_condition (gfc_equiv *eq1, gfc_equiv *eq2) { segment_info *n, *t; eq1->expr->symtree->n.sym->mark = 1; eq2->expr->symtree->n.sym->mark = 1; eq2->used = 1; n = find_segment_info (eq1->expr->symtree->n.sym); t = find_segment_info (eq2->expr->symtree->n.sym); if (n == NULL && t == NULL) abort (); if (n != NULL && t == NULL) new_condition (n, eq1, eq2); if (n == NULL && t != NULL) new_condition (t, eq2, eq1); if (n != NULL && t != NULL) confirm_condition (n, eq1, t, eq2); } /* Given a symbol, search through the equivalence lists for an unused condition that involves the symbol. If a rule is found, we return nonzero, the rule is marked as used and the eq1 and eq2 pointers point to the rule. */ static int find_equivalence (gfc_symbol *sym, gfc_equiv **eq1, gfc_equiv **eq2) { gfc_equiv *c, *l; for (c = sym->ns->equiv; c; c = c->next) for (l = c->eq; l; l = l->eq) { if (l->used) continue; if (c->expr->symtree->n.sym == sym || l->expr->symtree->n.sym == sym) { *eq1 = c; *eq2 = l; return 1; } } return 0; } /* Function for adding symbols to current segment. Returns zero if the segment was modified. Equivalence rules are considered to be between the first expression in the list and each of the other expressions in the list. Symbols are scanned multiple times because a symbol can be equivalenced more than once. */ static int add_equivalences (void) { int segment_modified; gfc_equiv *eq1, *eq2; segment_info *f; segment_modified = 0; for (f = current_segment; f; f = f->next) if (find_equivalence (f->sym, &eq1, &eq2)) break; if (f != NULL) { add_condition (eq1, eq2); segment_modified = 1; } return segment_modified; } /* 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_symbol *common_sym, gfc_symbol *sym) { segment_info *v; int length; current_segment = get_segment_info (); current_segment->sym = sym; current_segment->offset = current_offset; length = calculate_length (sym); current_segment->length = length; sym->mark = 1; /* Add all object directly or indirectly equivalenced with this common variable. */ while (add_equivalences ()); /* Calculate the storage size to hold the common block. */ for (v = current_segment; v; v = v->next) { if (v->offset < 0) gfc_error ("the equivalence set for '%s' cause an invalid extension " "to COMMON '%s' at %L", sym->name, common_sym->name, &common_sym->declared_at); if (current_length < (v->offset + v->length)) current_length = v->offset + v->length; } /* The offset of the next common variable. */ current_offset += length; /* Append the current segment to the current common. */ v = current_segment; while (v->next != NULL) v = v->next; v->next = current_common; current_common = current_segment; current_segment = NULL; } /* 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; 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_length = 0; current_segment = get_segment_info (); current_segment->sym = sym; current_segment->offset = 0; current_segment->length = calculate_length (sym); sym->mark = 1; /* All object directly or indrectly equivalenced with this symbol. */ while (add_equivalences ()); /* Calculate the minimal offset. */ min_offset = 0; for (v = current_segment; v; v = v->next) min_offset = (min_offset >= v->offset) ? v->offset : min_offset; /* Adjust the offset of each equivalence object, and calculate the maximal storage size to hold them. */ for (v = current_segment; v; v = v->next) { v->offset -= min_offset; if (current_length < (v->offset + v->length)) current_length = v->offset + v->length; } current_common = current_segment; create_common (NULL); break; } } /* Translate a single common block. */ static void translate_common (gfc_symbol *common_sym, gfc_symbol *var_list) { gfc_symbol *sym; current_common = NULL; current_length = 0; current_offset = 0; /* Mark bits indicate which symbols have already been placed in a common area. */ for (sym = var_list; sym; sym = sym->common_next) sym->mark = 0; for (;;) { for (sym = var_list; sym; sym = sym->common_next) if (!sym->mark) break; /* All symbols have been placed in a common. */ if (sym == NULL) break; new_segment (common_sym, sym); } create_common (common_sym); } /* Work function for translating a named common block. */ static void named_common (gfc_symbol *s) { if (s->attr.common) translate_common (s, s->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_symbol *sym; /* Translate the blank common block. */ if (ns->blank_common != NULL) { gfc_get_symbol (BLANK_COMMON_NAME, ns, &sym); translate_common (sym, ns->blank_common); } /* Translate all named common blocks. */ gfc_traverse_ns (ns, named_common); /* Commit the newly created symbols for common blocks. */ gfc_commit_symbols (); /* Translate local equivalence. */ finish_equivalences (ns); }