/* Build expressions with type checking for C compiler. Copyright (C) 1987, 88, 89, 92, 93, 96, 1997, 1998 Free Software Foundation, Inc. This file is part of GNU CC. GNU CC 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. GNU CC 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 GNU CC; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /* This file is part of the C front end. It is responsible for implementing iterators, both their declarations and the expansion of statements using them. */ #include "config.h" #include "system.h" #include "tree.h" #include "c-tree.h" #include "flags.h" #include "obstack.h" #include "rtl.h" #include "toplev.h" #include "expr.h" /* KEEPING TRACK OF EXPANSIONS In order to clean out expansions corresponding to statements inside "{(...)}" constructs we have to keep track of all expansions. The cleanup is needed when an automatic, or implicit, expansion on iterator, say X, happens to a statement which contains a {(...)} form with a statement already expanded on X. In this case we have to go back and cleanup the inner expansion. This can be further complicated by the fact that {(...)} can be nested. To make this cleanup possible, we keep lists of all expansions, and to make it work for nested constructs, we keep a stack. The list at the top of the stack (ITER_STACK.CURRENT_LEVEL) corresponds to the currently parsed level. All expansions of the levels below the current one are kept in one list whose head is pointed to by ITER_STACK.SUBLEVEL_FIRST (SUBLEVEL_LAST is there for making merges easy). The process works as follows: -- On "({" a new node is added to the stack by PUSH_ITERATOR_STACK. The sublevel list is not changed at this point. -- On "})" the list for the current level is appended to the sublevel list. -- On ";" sublevel lists are appended to the current level lists. The reason is this: if they have not been superseded by the expansion at the current level, they still might be superseded later by the expansion on the higher level. The levels do not have to distinguish levels below, so we can merge the lists together. */ struct ixpansion { tree ixdecl; /* Iterator decl */ rtx ixprologue_start; /* First insn of epilogue. NULL means */ /* explicit (FOR) expansion*/ rtx ixprologue_end; rtx ixepilogue_start; rtx ixepilogue_end; struct ixpansion *next; /* Next in the list */ }; struct iter_stack_node { struct ixpansion *first; /* Head of list of ixpansions */ struct ixpansion *last; /* Last node in list of ixpansions */ struct iter_stack_node *next; /* Next level iterator stack node */ }; struct iter_stack_node *iter_stack; struct iter_stack_node sublevel_ixpansions; /* A special obstack, and a pointer to the start of all the data in it (so we can free everything easily). */ static struct obstack ixp_obstack; static char *ixp_firstobj; /* During collect_iterators, a list of SAVE_EXPRs already scanned. */ static tree save_exprs; static void expand_stmt_with_iterators_1 PROTO((tree, tree)); static tree collect_iterators PROTO((tree, tree)); static void iterator_loop_prologue PROTO((tree, rtx *, rtx *)); static void iterator_loop_epilogue PROTO((tree, rtx *, rtx *)); static int top_level_ixpansion_p PROTO((void)); static void isn_append PROTO((struct iter_stack_node *, struct iter_stack_node *)); static void istack_sublevel_to_current PROTO((void)); static void add_ixpansion PROTO((tree, rtx, rtx, rtx, rtx)); static void delete_ixpansion PROTO((tree)); /* Initialize our obstack once per compilation. */ void init_iterators () { gcc_obstack_init (&ixp_obstack); ixp_firstobj = (char *) obstack_alloc (&ixp_obstack, 0); } /* Handle the start of an explicit `for' loop for iterator IDECL. */ void iterator_for_loop_start (idecl) tree idecl; { ITERATOR_BOUND_P (idecl) = 1; add_ixpansion (idecl, 0, 0, 0, 0); iterator_loop_prologue (idecl, 0, 0); } /* Handle the end of an explicit `for' loop for iterator IDECL. */ void iterator_for_loop_end (idecl) tree idecl; { iterator_loop_epilogue (idecl, 0, 0); ITERATOR_BOUND_P (idecl) = 0; } /* ITERATOR RTL EXPANSIONS Expanding simple statements with iterators is straightforward: collect the list of all free iterators in the statement, and generate a loop for each of them. An iterator is "free" if it has not been "bound" by a FOR operator. The DECL_RTL of the iterator is the loop counter. */ /* Expand a statement STMT, possibly containing iterator usage, into RTL. */ void iterator_expand (stmt) tree stmt; { tree iter_list; save_exprs = NULL_TREE; iter_list = collect_iterators (stmt, NULL_TREE); expand_stmt_with_iterators_1 (stmt, iter_list); istack_sublevel_to_current (); } static void expand_stmt_with_iterators_1 (stmt, iter_list) tree stmt, iter_list; { if (iter_list == 0) expand_expr_stmt (stmt); else { tree current_iterator = TREE_VALUE (iter_list); tree iter_list_tail = TREE_CHAIN (iter_list); rtx p_start, p_end, e_start, e_end; iterator_loop_prologue (current_iterator, &p_start, &p_end); expand_stmt_with_iterators_1 (stmt, iter_list_tail); iterator_loop_epilogue (current_iterator, &e_start, &e_end); /** Delete all inner expansions based on current_iterator **/ /** before adding the outer one. **/ delete_ixpansion (current_iterator); add_ixpansion (current_iterator, p_start, p_end, e_start, e_end); } } /* Return a list containing all the free (i.e. not bound by a containing `for' statement) iterators mentioned in EXP, plus those in LIST. Do not add duplicate entries to the list. */ static tree collect_iterators (exp, list) tree exp, list; { if (exp == 0) return list; switch (TREE_CODE (exp)) { case VAR_DECL: if (! ITERATOR_P (exp) || ITERATOR_BOUND_P (exp)) return list; if (value_member (exp, list)) return list; return tree_cons (NULL_TREE, exp, list); case TREE_LIST: { tree tail; for (tail = exp; tail; tail = TREE_CHAIN (tail)) list = collect_iterators (TREE_VALUE (tail), list); return list; } case SAVE_EXPR: /* In each scan, scan a given save_expr only once. */ if (value_member (exp, save_exprs)) return list; save_exprs = tree_cons (NULL_TREE, exp, save_exprs); return collect_iterators (TREE_OPERAND (exp, 0), list); /* we do not automatically iterate blocks -- one must */ /* use the FOR construct to do that */ case BLOCK: return list; default: switch (TREE_CODE_CLASS (TREE_CODE (exp))) { case '1': return collect_iterators (TREE_OPERAND (exp, 0), list); case '2': case '<': return collect_iterators (TREE_OPERAND (exp, 0), collect_iterators (TREE_OPERAND (exp, 1), list)); case 'e': case 'r': { int num_args = tree_code_length[(int) TREE_CODE (exp)]; int i; /* Some tree codes have RTL, not trees, as operands. */ switch (TREE_CODE (exp)) { case CALL_EXPR: num_args = 2; break; case METHOD_CALL_EXPR: num_args = 3; break; case WITH_CLEANUP_EXPR: num_args = 1; break; case RTL_EXPR: return list; default: break; } for (i = 0; i < num_args; i++) list = collect_iterators (TREE_OPERAND (exp, i), list); return list; } default: return list; } } } /* Emit rtl for the start of a loop for iterator IDECL. If necessary, create loop counter rtx and store it as DECL_RTL of IDECL. The prologue normally starts and ends with notes, which are returned by this function in *START_NOTE and *END_NODE. If START_NOTE and END_NODE are 0, we don't make those notes. */ static void iterator_loop_prologue (idecl, start_note, end_note) tree idecl; rtx *start_note, *end_note; { tree expr; /* Force the save_expr in DECL_INITIAL to be calculated if it hasn't been calculated yet. */ expand_expr (DECL_INITIAL (idecl), const0_rtx, VOIDmode, EXPAND_NORMAL); if (DECL_RTL (idecl) == 0) expand_decl (idecl); if (start_note) *start_note = emit_note (0, NOTE_INSN_DELETED); /* Initialize counter. */ expr = build (MODIFY_EXPR, TREE_TYPE (idecl), idecl, integer_zero_node); TREE_SIDE_EFFECTS (expr) = 1; expand_expr (expr, const0_rtx, VOIDmode, EXPAND_NORMAL); expand_start_loop_continue_elsewhere (1); ITERATOR_BOUND_P (idecl) = 1; if (end_note) *end_note = emit_note (0, NOTE_INSN_DELETED); } /* Similar to the previous function, but for the end of the loop. DECL_RTL is zeroed unless we are inside "({...})". The reason for that is described below. When we create two (or more) loops based on the same IDECL, and both inside the same "({...})" construct, we must be prepared to delete both of the loops and create a single one on the level above, i.e. enclosing the "({...})". The new loop has to use the same counter rtl because the references to the iterator decl (IDECL) have already been expanded as references to the counter rtl. It is incorrect to use the same counter reg in different functions, and it is desirable to use different counters in disjoint loops when we know there's no need to combine them (because then they can get allocated separately). */ static void iterator_loop_epilogue (idecl, start_note, end_note) tree idecl; rtx *start_note, *end_note; { tree test, incr; if (start_note) *start_note = emit_note (0, NOTE_INSN_DELETED); expand_loop_continue_here (); incr = build_binary_op (PLUS_EXPR, idecl, integer_one_node, 0); incr = build (MODIFY_EXPR, TREE_TYPE (idecl), idecl, incr); TREE_SIDE_EFFECTS (incr) = 1; expand_expr (incr, const0_rtx, VOIDmode, EXPAND_NORMAL); test = build_binary_op (LT_EXPR, idecl, DECL_INITIAL (idecl), 0); expand_exit_loop_if_false (0, test); expand_end_loop (); ITERATOR_BOUND_P (idecl) = 0; /* we can reset rtl since there is not chance that this expansion */ /* would be superseded by a higher level one */ /* but don't do this if the decl is static, since we need to share */ /* the same decl in that case. */ if (top_level_ixpansion_p () && ! TREE_STATIC (idecl)) DECL_RTL (idecl) = 0; if (end_note) *end_note = emit_note (0, NOTE_INSN_DELETED); } /* Return true if we are not currently inside a "({...})" construct. */ static int top_level_ixpansion_p () { return iter_stack == 0; } /* Given two chains of iter_stack_nodes, append the nodes in X into Y. */ static void isn_append (x, y) struct iter_stack_node *x, *y; { if (x->first == 0) return; if (y->first == 0) { y->first = x->first; y->last = x->last; } else { y->last->next = x->first; y->last = x->last; } } /** Make X empty **/ #define ISN_ZERO(X) (X).first=(X).last=0 /* Move the ixpansions in sublevel_ixpansions into the current node on the iter_stack, or discard them if the iter_stack is empty. We do this at the end of a statement. */ static void istack_sublevel_to_current () { /* At the top level we can throw away sublevel's expansions **/ /* because there is nobody above us to ask for a cleanup **/ if (iter_stack != 0) /** Merging with empty sublevel list is a no-op **/ if (sublevel_ixpansions.last) isn_append (&sublevel_ixpansions, iter_stack); if (iter_stack == 0) obstack_free (&ixp_obstack, ixp_firstobj); ISN_ZERO (sublevel_ixpansions); } /* Push a new node on the iter_stack, when we enter a ({...}). */ void push_iterator_stack () { struct iter_stack_node *new_top = (struct iter_stack_node *) obstack_alloc (&ixp_obstack, sizeof (struct iter_stack_node)); new_top->first = 0; new_top->last = 0; new_top->next = iter_stack; iter_stack = new_top; } /* Pop iter_stack, moving the ixpansions in the node being popped into sublevel_ixpansions. */ void pop_iterator_stack () { if (iter_stack == 0) abort (); isn_append (iter_stack, &sublevel_ixpansions); /** Pop current level node: */ iter_stack = iter_stack->next; } /* Record an iterator expansion ("ixpansion") for IDECL. The remaining parameters are the notes in the loop entry and exit rtl. */ static void add_ixpansion (idecl, pro_start, pro_end, epi_start, epi_end) tree idecl; rtx pro_start, pro_end, epi_start, epi_end; { struct ixpansion *newix; /* Do nothing if we are not inside "({...})", as in that case this expansion can't need subsequent RTL modification. */ if (iter_stack == 0) return; newix = (struct ixpansion *) obstack_alloc (&ixp_obstack, sizeof (struct ixpansion)); newix->ixdecl = idecl; newix->ixprologue_start = pro_start; newix->ixprologue_end = pro_end; newix->ixepilogue_start = epi_start; newix->ixepilogue_end = epi_end; newix->next = iter_stack->first; iter_stack->first = newix; if (iter_stack->last == 0) iter_stack->last = newix; } /* Delete the RTL for all ixpansions for iterator IDECL in our sublevels. We do this when we make a larger containing expansion for IDECL. */ static void delete_ixpansion (idecl) tree idecl; { struct ixpansion *previx = 0, *ix; for (ix = sublevel_ixpansions.first; ix; ix = ix->next) if (ix->ixdecl == idecl) { /** zero means that this is a mark for FOR -- **/ /** we do not delete anything, just issue an error. **/ if (ix->ixprologue_start == 0) error_with_decl (idecl, "`for (%s)' appears within implicit iteration"); else { rtx insn; /* We delete all insns, including notes because leaving loop */ /* notes and barriers produced by iterator expansion would */ /* be misleading to other phases */ for (insn = NEXT_INSN (ix->ixprologue_start); insn != ix->ixprologue_end; insn = NEXT_INSN (insn)) delete_insn (insn); for (insn = NEXT_INSN (ix->ixepilogue_start); insn != ix->ixepilogue_end; insn = NEXT_INSN (insn)) delete_insn (insn); } /* Delete this ixpansion from sublevel_ixpansions. */ if (previx) previx->next = ix->next; else sublevel_ixpansions.first = ix->next; if (sublevel_ixpansions.last == ix) sublevel_ixpansions.last = previx; } else previx = ix; } #ifdef DEBUG_ITERATORS /* The functions below are for use from source level debugger. They print short forms of iterator lists and the iterator stack. */ /* Print the name of the iterator D. */ void prdecl (d) tree d; { if (d) { if (TREE_CODE (d) == VAR_DECL) { tree tname = DECL_NAME (d); char *dname = IDENTIFIER_POINTER (tname); fprintf (stderr, dname); } else fprintf (stderr, "<>"); } else fprintf (stderr, "<<0>>"); } /* Print Iterator List -- names only */ tree pil (head) tree head; { tree current, next; for (current = head; current; current = next) { tree node = TREE_VALUE (current); prdecl (node); next = TREE_CHAIN (current); if (next) fprintf (stderr, ","); } fprintf (stderr, "\n"); } /* Print IXpansion List */ struct ixpansion * pixl (head) struct ixpansion *head; { struct ixpansion *current, *next; fprintf (stderr, "> "); if (head == 0) fprintf (stderr, "(empty)"); for (current=head; current; current = next) { tree node = current->ixdecl; prdecl (node); next = current->next; if (next) fprintf (stderr, ","); } fprintf (stderr, "\n"); return head; } /* Print Iterator Stack. */ void pis () { struct iter_stack_node *stack_node; fprintf (stderr, "--SubLevel: "); pixl (sublevel_ixpansions.first); fprintf (stderr, "--Stack:--\n"); for (stack_node = iter_stack; stack_node; stack_node = stack_node->next) pixl (stack_node->first); } #endif /* DEBUG_ITERATORS */