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