1 /* Tree lowering pass. This pass gimplifies the tree representation built
2 by the C-based front ends. The structure of gimplified, or
3 language-independent, trees is dictated by the grammar described in this
5 Copyright (C) 2002, 2003 Free Software Foundation, Inc.
6 Lowering of expressions contributed by Sebastian Pop <s.pop@laposte.net>
7 Re-written to support lowering of whole function trees, documentation
8 and miscellaneous cleanups by Diego Novillo <dnovillo@redhat.com>
10 This file is part of GCC.
12 GCC is free software; you can redistribute it and/or modify it under
13 the terms of the GNU General Public License as published by the Free
14 Software Foundation; either version 2, or (at your option) any later
17 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
18 WARRANTY; without even the implied warranty of MERCHANTABILITY or
19 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
22 You should have received a copy of the GNU General Public License
23 along with GCC; see the file COPYING. If not, write to the Free
24 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
29 #include "coretypes.h"
36 #include "tree-gimple.h"
37 #include "hard-reg-set.h"
38 #include "basic-block.h"
39 #include "tree-flow.h"
40 #include "tree-inline.h"
41 #include "diagnostic.h"
42 #include "langhooks.h"
43 #include "langhooks-def.h"
47 #include "tree-dump.h"
48 #include "c-pretty-print.h"
52 /* The gimplification pass converts the language-dependent trees
53 (ld-trees) emitted by the parser into language-independent trees
54 (li-trees) that are the target of SSA analysis and transformations.
56 Language-independent trees are based on the SIMPLE intermediate
57 representation used in the McCAT compiler framework:
59 "Designing the McCAT Compiler Based on a Family of Structured
60 Intermediate Representations,"
61 L. Hendren, C. Donawa, M. Emami, G. Gao, Justiani, and B. Sridharan,
62 Proceedings of the 5th International Workshop on Languages and
63 Compilers for Parallel Computing, no. 757 in Lecture Notes in
64 Computer Science, New Haven, Connecticut, pp. 406-420,
65 Springer-Verlag, August 3-5, 1992.
67 http://www-acaps.cs.mcgill.ca/info/McCAT/McCAT.html
69 Basically, we walk down gimplifying the nodes that we encounter. As we
70 walk back up, we check that they fit our constraints, and copy them
71 into temporaries if not. */
73 /* Local declarations. */
75 static enum gimplify_status gimplify_expr_stmt (tree *);
76 static enum gimplify_status gimplify_decl_stmt (tree *);
77 static enum gimplify_status gimplify_for_stmt (tree *, tree *);
78 static enum gimplify_status gimplify_while_stmt (tree *);
79 static enum gimplify_status gimplify_do_stmt (tree *);
80 static enum gimplify_status gimplify_if_stmt (tree *);
81 static enum gimplify_status gimplify_switch_stmt (tree *);
82 static enum gimplify_status gimplify_return_stmt (tree *);
83 static enum gimplify_status gimplify_compound_literal_expr (tree *);
84 static void gimplify_cleanup_stmts (tree);
85 static tree gimplify_c_loop (tree, tree, tree, bool);
86 static void push_context (void);
87 static void pop_context (void);
88 static void add_block_to_enclosing (tree);
89 static void gimplify_condition (tree *);
91 enum bc_t { bc_break = 0, bc_continue = 1 };
92 static tree begin_bc_block (enum bc_t);
93 static tree finish_bc_block (tree, tree);
94 static tree build_bc_goto (enum bc_t);
96 static struct c_gimplify_ctx
98 /* For handling break and continue. */
99 tree current_bc_label;
108 ctxp = (struct c_gimplify_ctx *) xcalloc (1, sizeof (struct c_gimplify_ctx));
109 ctxp->bc_id[bc_continue] = get_identifier ("continue");
110 ctxp->bc_id[bc_break] = get_identifier ("break");
116 if (!ctxp || ctxp->current_bc_label)
122 /* Gimplification of statement trees. */
124 /* Convert the tree representation of FNDECL from C frontend trees to
128 c_genericize (tree fndecl)
131 int local_dump_flags;
132 struct cgraph_node *cgn;
134 /* Dump the C-specific tree IR. */
135 dump_file = dump_begin (TDI_original, &local_dump_flags);
138 fprintf (dump_file, "\n;; Function %s",
139 lang_hooks.decl_printable_name (fndecl, 2));
140 fprintf (dump_file, " (%s)\n",
141 IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl)));
142 fprintf (dump_file, ";; enabled by -%s\n", dump_flag_name (TDI_original));
143 fprintf (dump_file, "\n");
145 if (local_dump_flags & TDF_RAW)
146 dump_node (DECL_SAVED_TREE (fndecl),
147 TDF_SLIM | local_dump_flags, dump_file);
149 print_c_tree (dump_file, DECL_SAVED_TREE (fndecl));
150 fprintf (dump_file, "\n");
152 dump_end (TDI_original, dump_file);
155 /* Go ahead and gimplify for now. */
157 gimplify_cleanup_stmts (fndecl);
158 gimplify_function_tree (fndecl);
161 /* Dump the genericized tree IR. */
162 dump_function (TDI_generic, fndecl);
164 /* Genericize all nested functions now. We do things in this order so
165 that items like VLA sizes are expanded properly in the context of
166 the correct function. */
167 cgn = cgraph_node (fndecl);
168 for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
169 c_genericize (cgn->decl);
172 /* Genericize a CLEANUP_STMT. This just turns into a TRY_FINALLY or
173 TRY_CATCH depending on whether it's EH-only. */
176 gimplify_cleanup_stmt (tree *stmt_p, int *walk_subtrees,
177 void *data ATTRIBUTE_UNUSED)
181 if (DECL_P (stmt) || TYPE_P (stmt))
183 else if (TREE_CODE (stmt) == CLEANUP_STMT)
184 *stmt_p = build (CLEANUP_EH_ONLY (stmt) ? TRY_CATCH_EXPR : TRY_FINALLY_EXPR,
185 void_type_node, CLEANUP_BODY (stmt), CLEANUP_EXPR (stmt));
191 gimplify_cleanup_stmts (tree fndecl)
193 walk_tree (&DECL_SAVED_TREE (fndecl), gimplify_cleanup_stmt, NULL, NULL);
196 /* Entry point for the tree lowering pass. Recursively scan
197 *STMT_P and convert it to a GIMPLE tree. */
200 c_gimplify_stmt (tree *stmt_p)
204 int saved_stmts_are_full_exprs_p;
205 location_t stmt_locus;
206 enum gimplify_status ret;
208 /* PRE and POST are tree chains that contain the side-effects of the
209 gimplified tree. For instance, given the expression tree:
213 After gimplification, the tree will be re-written as:
218 b = b + 1; <-- POST */
220 /* Set up context appropriately for handling this statement. */
221 saved_stmts_are_full_exprs_p = stmts_are_full_exprs_p ();
223 stmt_locus = input_location;
228 switch (TREE_CODE (stmt))
231 ret = gimplify_for_stmt (&stmt, &pre);
235 ret = gimplify_while_stmt (&stmt);
239 ret = gimplify_do_stmt (&stmt);
243 ret = gimplify_if_stmt (&stmt);
247 ret = gimplify_switch_stmt (&stmt);
251 ret = gimplify_expr_stmt (&stmt);
255 ret = gimplify_return_stmt (&stmt);
259 ret = gimplify_decl_stmt (&stmt);
263 stmt = build_bc_goto (bc_continue);
268 stmt = build_bc_goto (bc_break);
273 if (lang_gimplify_stmt && (*lang_gimplify_stmt) (&stmt))
279 fprintf (stderr, "unhandled statement node in c_gimplify_stmt:\n");
290 gimplify_stmt (&stmt);
298 /* PRE and POST now contain a list of statements for all the
299 side-effects in STMT. */
301 append_to_statement_list (stmt, &pre);
302 append_to_statement_list (post, &pre);
303 annotate_all_with_locus (&pre, stmt_locus);
305 /* Restore saved state. */
306 current_stmt_tree ()->stmts_are_full_exprs_p = saved_stmts_are_full_exprs_p;
313 add_block_to_enclosing (tree block)
317 for (enclosing = gimple_current_bind_expr ();
318 enclosing; enclosing = TREE_CHAIN (enclosing))
319 if (BIND_EXPR_BLOCK (enclosing))
322 enclosing = BIND_EXPR_BLOCK (enclosing);
323 BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
326 /* Genericize a scope by creating a new BIND_EXPR.
327 BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
328 In the latter case, we need to create a new BLOCK and add it to the
329 BLOCK_SUBBLOCKS of the enclosing block.
330 BODY is a chain of C _STMT nodes for the contents of the scope, to be
334 c_build_bind_expr (tree block, tree body)
338 if (block == NULL_TREE)
340 else if (TREE_CODE (block) == BLOCK)
341 decls = BLOCK_VARS (block);
345 if (DECL_ARTIFICIAL (decls))
349 block = make_node (BLOCK);
350 BLOCK_VARS (block) = decls;
351 add_block_to_enclosing (block);
356 body = build_empty_stmt ();
359 bind = build (BIND_EXPR, void_type_node, decls, body, block);
360 TREE_SIDE_EFFECTS (bind) = 1;
368 /* Gimplify an EXPR_STMT node.
370 STMT is the statement node.
372 PRE_P points to the list where side effects that must happen before
373 STMT should be stored.
375 POST_P points to the list where side effects that must happen after
376 STMT should be stored. */
378 static enum gimplify_status
379 gimplify_expr_stmt (tree *stmt_p)
381 tree stmt = EXPR_STMT_EXPR (*stmt_p);
383 if (stmt == error_mark_node)
386 /* Gimplification of a statement expression will nullify the
387 statement if all its side effects are moved to *PRE_P and *POST_P.
389 In this case we will not want to emit the gimplified statement.
390 However, we may still want to emit a warning, so we do that before
392 if (stmt && (extra_warnings || warn_unused_value))
394 if (!TREE_SIDE_EFFECTS (stmt))
396 if (!IS_EMPTY_STMT (stmt)
397 && !VOID_TYPE_P (TREE_TYPE (stmt))
398 && !TREE_NO_WARNING (stmt))
399 warning ("statement with no effect");
401 else if (warn_unused_value)
403 /* Kludge for 20020220-2.c. warn_if_unused_value shouldn't use
404 the stmt file location info. */
405 set_file_and_line_for_stmt (input_location);
406 warn_if_unused_value (stmt);
410 if (stmt == NULL_TREE)
411 stmt = build_empty_stmt ();
412 else if (stmts_are_full_exprs_p ())
413 stmt = build1 (CLEANUP_POINT_EXPR, void_type_node, stmt);
420 /* If the condition for a loop (or the like) is a decl, it will be a
421 TREE_LIST where the TREE_PURPOSE is a DECL_STMT and the TREE_VALUE is
422 a use of the decl. Turn such a thing into a COMPOUND_EXPR. */
425 gimplify_condition (tree *cond_p)
428 if (cond && TREE_CODE (cond) == TREE_LIST)
430 tree decl = TREE_PURPOSE (cond);
431 tree value = TREE_VALUE (cond);
432 gimplify_stmt (&decl);
433 *cond_p = build (COMPOUND_EXPR, TREE_TYPE (value), decl, value);
437 /* Begin a scope which can be exited by a break or continue statement. BC
440 Just creates a label and pushes it into the current context. */
443 begin_bc_block (enum bc_t bc)
445 tree label = create_artificial_label ();
446 DECL_NAME (label) = ctxp->bc_id[bc];
447 TREE_CHAIN (label) = ctxp->current_bc_label;
448 ctxp->current_bc_label = label;
452 /* Finish a scope which can be exited by a break or continue statement.
453 LABEL was returned from the most recent call to begin_bc_block. BODY is
454 an expression for the contents of the scope.
456 If we saw a break (or continue) in the scope, append a LABEL_EXPR to
457 body. Otherwise, just forget the label. */
460 finish_bc_block (tree label, tree body)
462 if (label != ctxp->current_bc_label)
465 if (TREE_USED (label))
469 /* Clear the name so flow can delete the label. */
470 DECL_NAME (label) = NULL_TREE;
471 t = build1 (LABEL_EXPR, void_type_node, label);
473 append_to_statement_list (body, &sl);
474 append_to_statement_list (t, &sl);
478 ctxp->current_bc_label = TREE_CHAIN (label);
479 TREE_CHAIN (label) = NULL_TREE;
483 /* Build a GOTO_EXPR to represent a break or continue statement. BC
487 build_bc_goto (enum bc_t bc)
490 tree target_name = ctxp->bc_id[bc];
492 /* Look for the appropriate type of label. */
493 for (label = ctxp->current_bc_label;
495 label = TREE_CHAIN (label))
496 if (DECL_NAME (label) == target_name)
499 if (label == NULL_TREE)
502 error ("break statement not within loop or switch");
504 error ("continue statement not within loop or switch");
509 /* Mark the label used for finish_bc_block. */
510 TREE_USED (label) = 1;
511 return build1 (GOTO_EXPR, void_type_node, label);
514 /* Build a generic representation of one of the C loop forms. COND is the
515 loop condition or NULL_TREE. BODY is the (possibly compound) statement
516 controlled by the loop. INCR is the increment expression of a for-loop,
517 or NULL_TREE. COND_IS_FIRST indicates whether the condition is
518 evaluated before the loop body as in while and for loops, or after the
519 loop body as in do-while loops. */
522 gimplify_c_loop (tree cond, tree body, tree incr, bool cond_is_first)
524 tree top, entry, exit, cont_block, break_block, stmt_list, t;
525 location_t stmt_locus;
527 stmt_locus = input_location;
529 /* Detect do { ... } while (0) and don't generate loop construct. */
530 if (!cond_is_first && cond && integer_zerop (cond))
534 /* If we use a LOOP_EXPR here, we have to feed the whole thing
535 back through the main gimplifier to lower it. Given that we
536 have to gimplify the loop body NOW so that we can resolve
537 break/continue stmts, seems easier to just expand to gotos. */
538 top = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
541 break_block = begin_bc_block (bc_break);
545 /* If we have an exit condition, then we build an IF with gotos either
546 out of the loop, or to the top of it. If there's no exit condition,
547 then we just build a jump back to the top. */
548 exit = build_and_jump (&LABEL_EXPR_LABEL (top));
551 gimplify_condition (&cond);
552 t = build_bc_goto (bc_break);
553 exit = build (COND_EXPR, void_type_node, cond, exit, t);
555 gimplify_stmt (&exit);
561 cont_block = begin_bc_block (bc_continue);
563 gimplify_stmt (&body);
564 if (incr && stmts_are_full_exprs_p ())
565 incr = fold (build1 (CLEANUP_POINT_EXPR, void_type_node, incr));
566 gimplify_stmt (&incr);
568 body = finish_bc_block (cont_block, body);
572 if (cond_is_first && cond)
574 entry = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
575 t = build_and_jump (&LABEL_EXPR_LABEL (entry));
576 append_to_statement_list (t, &stmt_list);
581 append_to_statement_list (top, &stmt_list);
582 append_to_statement_list (body, &stmt_list);
583 append_to_statement_list (incr, &stmt_list);
584 append_to_statement_list (entry, &stmt_list);
585 append_to_statement_list (exit, &stmt_list);
587 annotate_all_with_locus (&stmt_list, stmt_locus);
589 return finish_bc_block (break_block, stmt_list);
592 /* Gimplify a FOR_STMT node. Move the stuff in the for-init-stmt into the
593 prequeue and hand off to gimplify_c_loop. */
595 static enum gimplify_status
596 gimplify_for_stmt (tree *stmt_p, tree *pre_p)
600 if (FOR_INIT_STMT (stmt))
602 gimplify_stmt (&FOR_INIT_STMT (stmt));
603 append_to_statement_list (FOR_INIT_STMT (stmt), pre_p);
605 *stmt_p = gimplify_c_loop (FOR_COND (stmt), FOR_BODY (stmt),
611 /* Gimplify a WHILE_STMT node. */
613 static enum gimplify_status
614 gimplify_while_stmt (tree *stmt_p)
617 *stmt_p = gimplify_c_loop (WHILE_COND (stmt), WHILE_BODY (stmt),
622 /* Gimplify a DO_STMT node. */
624 static enum gimplify_status
625 gimplify_do_stmt (tree *stmt_p)
628 *stmt_p = gimplify_c_loop (DO_COND (stmt), DO_BODY (stmt),
633 /* Genericize an IF_STMT by turning it into a COND_EXPR. */
635 static enum gimplify_status
636 gimplify_if_stmt (tree *stmt_p)
638 tree stmt, then_, else_;
641 then_ = THEN_CLAUSE (stmt);
642 else_ = ELSE_CLAUSE (stmt);
645 then_ = build_empty_stmt ();
647 else_ = build_empty_stmt ();
649 stmt = build (COND_EXPR, void_type_node, IF_COND (stmt), then_, else_);
650 gimplify_condition (& TREE_OPERAND (stmt, 0));
656 /* Genericize a SWITCH_STMT by turning it into a SWITCH_EXPR. */
658 static enum gimplify_status
659 gimplify_switch_stmt (tree *stmt_p)
662 tree break_block, body;
663 location_t stmt_locus = input_location;
665 break_block = begin_bc_block (bc_break);
667 gimplify_condition (&SWITCH_COND (stmt));
669 body = SWITCH_BODY (stmt);
671 body = build_empty_stmt ();
673 *stmt_p = build (SWITCH_EXPR, SWITCH_TYPE (stmt), SWITCH_COND (stmt),
675 annotate_with_locus (*stmt_p, stmt_locus);
676 gimplify_stmt (stmt_p);
678 *stmt_p = finish_bc_block (break_block, *stmt_p);
682 /* Genericize a RETURN_STMT by turning it into a RETURN_EXPR. */
684 static enum gimplify_status
685 gimplify_return_stmt (tree *stmt_p)
687 tree expr = RETURN_STMT_EXPR (*stmt_p);
688 expr = build1 (RETURN_EXPR, void_type_node, expr);
689 if (stmts_are_full_exprs_p ())
690 expr = build1 (CLEANUP_POINT_EXPR, void_type_node, expr);
695 /* Gimplifies a DECL_STMT node *STMT_P by making any necessary allocation
696 and initialization explicit. */
698 static enum gimplify_status
699 gimplify_decl_stmt (tree *stmt_p)
702 tree decl = DECL_STMT_DECL (stmt);
703 tree pre = NULL_TREE;
704 tree post = NULL_TREE;
706 if (TREE_TYPE (decl) == error_mark_node)
712 if (TREE_CODE (decl) == TYPE_DECL)
714 tree type = TREE_TYPE (decl);
715 if (TYPE_SIZE_UNIT (type)
716 && !TREE_CONSTANT (TYPE_SIZE_UNIT (type)))
718 /* This is a variable-sized array type. Simplify its size. */
719 tree temp = TYPE_SIZE_UNIT (type);
720 gimplify_expr (&temp, &pre, &post, is_gimple_val, fb_rvalue);
724 if (TREE_CODE (decl) == VAR_DECL && !DECL_EXTERNAL (decl))
726 tree init = DECL_INITIAL (decl);
728 if (!TREE_CONSTANT (DECL_SIZE (decl)))
730 tree pt_type = build_pointer_type (TREE_TYPE (decl));
733 /* This is a variable-sized decl. Simplify its size and mark it
734 for deferred expansion. Note that mudflap depends on the format
735 of the emitted code: see mx_register_decls(). */
737 size = get_initialized_tmp_var (DECL_SIZE_UNIT (decl), &pre, &post);
738 DECL_DEFER_OUTPUT (decl) = 1;
739 alloc = build_function_call_expr
740 (implicit_built_in_decls[BUILT_IN_STACK_ALLOC],
741 tree_cons (NULL_TREE,
742 build1 (ADDR_EXPR, pt_type, decl),
743 tree_cons (NULL_TREE, size, NULL_TREE)));
744 append_to_compound_expr (alloc, &pre);
747 if (init && init != error_mark_node)
749 if (!TREE_STATIC (decl))
751 /* Do not warn about int x = x; as it is a GCC extension
752 to turn off this warning but only if warn_init_self
754 if (init == decl && !warn_init_self)
755 TREE_NO_WARNING (decl) = 1;
757 DECL_INITIAL (decl) = NULL_TREE;
758 init = build (MODIFY_EXPR, void_type_node, decl, init);
759 if (stmts_are_full_exprs_p ())
760 init = build1 (CLEANUP_POINT_EXPR, void_type_node, init);
761 append_to_compound_expr (init, &pre);
765 /* We must still examine initializers for static variables
766 as they may contain a label address. */
767 walk_tree (&init, force_labels_r, NULL, NULL);
771 /* This decl isn't mentioned in the enclosing block, so add it to the
772 list of temps. FIXME it seems a bit of a kludge to say that
773 anonymous artificial vars aren't pushed, but everything else is. */
774 if (DECL_ARTIFICIAL (decl) && DECL_NAME (decl) == NULL_TREE)
775 gimple_add_tmp_var (decl);
778 append_to_compound_expr (post, &pre);
783 /* Gimplification of expression trees. */
785 /* Gimplify a C99 compound literal expression. This just means adding the
786 DECL_STMT before the current EXPR_STMT and using its anonymous decl
789 static enum gimplify_status
790 gimplify_compound_literal_expr (tree *expr_p)
792 tree decl_s = COMPOUND_LITERAL_EXPR_DECL_STMT (*expr_p);
793 tree decl = DECL_STMT_DECL (decl_s);
795 /* This decl isn't mentioned in the enclosing block, so add it to the
796 list of temps. FIXME it seems a bit of a kludge to say that
797 anonymous artificial vars aren't pushed, but everything else is. */
798 if (DECL_NAME (decl) == NULL_TREE)
799 gimple_add_tmp_var (decl);
801 gimplify_decl_stmt (&decl_s);
802 *expr_p = decl_s ? decl_s : decl;
806 /* Do C-specific gimplification. Args are as for gimplify_expr. */
809 c_gimplify_expr (tree *expr_p, tree *pre_p ATTRIBUTE_UNUSED,
810 tree *post_p ATTRIBUTE_UNUSED)
812 enum tree_code code = TREE_CODE (*expr_p);
814 if (STATEMENT_CODE_P (code))
815 return c_gimplify_stmt (expr_p);
819 case COMPOUND_LITERAL_EXPR:
820 return gimplify_compound_literal_expr (expr_p);