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 stmt = COMPOUND_BODY (stmt);
236 ret = gimplify_for_stmt (&stmt, &pre);
240 ret = gimplify_while_stmt (&stmt);
244 ret = gimplify_do_stmt (&stmt);
248 ret = gimplify_if_stmt (&stmt);
252 ret = gimplify_switch_stmt (&stmt);
256 ret = gimplify_expr_stmt (&stmt);
260 ret = gimplify_return_stmt (&stmt);
264 ret = gimplify_decl_stmt (&stmt);
268 stmt = build1 (LABEL_EXPR, void_type_node, LABEL_STMT_LABEL (stmt));
273 stmt = build1 (GOTO_EXPR, void_type_node, GOTO_DESTINATION (stmt));
279 tree label = create_artificial_label ();
280 stmt = build (CASE_LABEL_EXPR, void_type_node,
281 CASE_LOW (stmt), CASE_HIGH (stmt), label);
287 stmt = build_bc_goto (bc_continue);
292 stmt = build_bc_goto (bc_break);
298 tree new_stmt = build (ASM_EXPR, void_type_node, ASM_STRING (stmt),
299 ASM_OUTPUTS (stmt), ASM_INPUTS (stmt),
300 ASM_CLOBBERS (stmt));
301 ASM_INPUT_P (new_stmt) = ASM_INPUT_P (stmt);
302 ASM_VOLATILE_P (new_stmt) = ASM_VOLATILE_P (stmt);
309 if (lang_gimplify_stmt && (*lang_gimplify_stmt) (&stmt))
315 fprintf (stderr, "unhandled statement node in c_gimplify_stmt:\n");
326 gimplify_stmt (&stmt);
334 /* PRE and POST now contain a list of statements for all the
335 side-effects in STMT. */
337 append_to_statement_list (stmt, &pre);
338 append_to_statement_list (post, &pre);
339 annotate_all_with_locus (&pre, stmt_locus);
341 /* Restore saved state. */
342 current_stmt_tree ()->stmts_are_full_exprs_p = saved_stmts_are_full_exprs_p;
349 add_block_to_enclosing (tree block)
353 for (enclosing = gimple_current_bind_expr ();
354 enclosing; enclosing = TREE_CHAIN (enclosing))
355 if (BIND_EXPR_BLOCK (enclosing))
358 enclosing = BIND_EXPR_BLOCK (enclosing);
359 BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
362 /* Genericize a scope by creating a new BIND_EXPR.
363 BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
364 In the latter case, we need to create a new BLOCK and add it to the
365 BLOCK_SUBBLOCKS of the enclosing block.
366 BODY is a chain of C _STMT nodes for the contents of the scope, to be
370 c_build_bind_expr (tree block, tree body)
374 if (block == NULL_TREE)
376 else if (TREE_CODE (block) == BLOCK)
377 decls = BLOCK_VARS (block);
381 if (DECL_ARTIFICIAL (decls))
385 block = make_node (BLOCK);
386 BLOCK_VARS (block) = decls;
387 add_block_to_enclosing (block);
392 body = build_empty_stmt ();
395 bind = build (BIND_EXPR, void_type_node, decls, body, block);
396 TREE_SIDE_EFFECTS (bind) = 1;
404 /* Gimplify an EXPR_STMT node.
406 STMT is the statement node.
408 PRE_P points to the list where side effects that must happen before
409 STMT should be stored.
411 POST_P points to the list where side effects that must happen after
412 STMT should be stored. */
414 static enum gimplify_status
415 gimplify_expr_stmt (tree *stmt_p)
417 tree stmt = EXPR_STMT_EXPR (*stmt_p);
419 if (stmt == error_mark_node)
422 /* Gimplification of a statement expression will nullify the
423 statement if all its side effects are moved to *PRE_P and *POST_P.
425 In this case we will not want to emit the gimplified statement.
426 However, we may still want to emit a warning, so we do that before
428 if (stmt && (extra_warnings || warn_unused_value))
430 if (!TREE_SIDE_EFFECTS (stmt))
432 if (!IS_EMPTY_STMT (stmt)
433 && !VOID_TYPE_P (TREE_TYPE (stmt))
434 && !TREE_NO_WARNING (stmt))
435 warning ("statement with no effect");
437 else if (warn_unused_value)
439 /* Kludge for 20020220-2.c. warn_if_unused_value shouldn't use
440 the stmt file location info. */
441 set_file_and_line_for_stmt (input_location);
442 warn_if_unused_value (stmt);
446 if (stmt == NULL_TREE)
447 stmt = build_empty_stmt ();
448 else if (stmts_are_full_exprs_p ())
449 stmt = build1 (CLEANUP_POINT_EXPR, void_type_node, stmt);
456 /* If the condition for a loop (or the like) is a decl, it will be a
457 TREE_LIST where the TREE_PURPOSE is a DECL_STMT and the TREE_VALUE is
458 a use of the decl. Turn such a thing into a COMPOUND_EXPR. */
461 gimplify_condition (tree *cond_p)
464 if (cond && TREE_CODE (cond) == TREE_LIST)
466 tree decl = TREE_PURPOSE (cond);
467 tree value = TREE_VALUE (cond);
468 gimplify_stmt (&decl);
469 *cond_p = build (COMPOUND_EXPR, TREE_TYPE (value), decl, value);
473 /* Begin a scope which can be exited by a break or continue statement. BC
476 Just creates a label and pushes it into the current context. */
479 begin_bc_block (enum bc_t bc)
481 tree label = create_artificial_label ();
482 DECL_NAME (label) = ctxp->bc_id[bc];
483 TREE_CHAIN (label) = ctxp->current_bc_label;
484 ctxp->current_bc_label = label;
488 /* Finish a scope which can be exited by a break or continue statement.
489 LABEL was returned from the most recent call to begin_bc_block. BODY is
490 an expression for the contents of the scope.
492 If we saw a break (or continue) in the scope, append a LABEL_EXPR to
493 body. Otherwise, just forget the label. */
496 finish_bc_block (tree label, tree body)
498 if (label != ctxp->current_bc_label)
501 if (TREE_USED (label))
505 /* Clear the name so flow can delete the label. */
506 DECL_NAME (label) = NULL_TREE;
507 t = build1 (LABEL_EXPR, void_type_node, label);
509 append_to_statement_list (body, &sl);
510 append_to_statement_list (t, &sl);
514 ctxp->current_bc_label = TREE_CHAIN (label);
515 TREE_CHAIN (label) = NULL_TREE;
519 /* Build a GOTO_EXPR to represent a break or continue statement. BC
523 build_bc_goto (enum bc_t bc)
526 tree target_name = ctxp->bc_id[bc];
528 /* Look for the appropriate type of label. */
529 for (label = ctxp->current_bc_label;
531 label = TREE_CHAIN (label))
532 if (DECL_NAME (label) == target_name)
535 if (label == NULL_TREE)
538 error ("break statement not within loop or switch");
540 error ("continue statement not within loop or switch");
545 /* Mark the label used for finish_bc_block. */
546 TREE_USED (label) = 1;
547 return build1 (GOTO_EXPR, void_type_node, label);
550 /* Build a generic representation of one of the C loop forms. COND is the
551 loop condition or NULL_TREE. BODY is the (possibly compound) statement
552 controlled by the loop. INCR is the increment expression of a for-loop,
553 or NULL_TREE. COND_IS_FIRST indicates whether the condition is
554 evaluated before the loop body as in while and for loops, or after the
555 loop body as in do-while loops. */
558 gimplify_c_loop (tree cond, tree body, tree incr, bool cond_is_first)
560 tree top, entry, exit, cont_block, break_block, stmt_list, t;
561 location_t stmt_locus;
563 stmt_locus = input_location;
565 /* Detect do { ... } while (0) and don't generate loop construct. */
566 if (!cond_is_first && cond && integer_zerop (cond))
570 /* If we use a LOOP_EXPR here, we have to feed the whole thing
571 back through the main gimplifier to lower it. Given that we
572 have to gimplify the loop body NOW so that we can resolve
573 break/continue stmts, seems easier to just expand to gotos. */
574 top = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
577 break_block = begin_bc_block (bc_break);
581 /* If we have an exit condition, then we build an IF with gotos either
582 out of the loop, or to the top of it. If there's no exit condition,
583 then we just build a jump back to the top. */
584 exit = build_and_jump (&LABEL_EXPR_LABEL (top));
587 gimplify_condition (&cond);
588 t = build_bc_goto (bc_break);
589 exit = build (COND_EXPR, void_type_node, cond, exit, t);
591 gimplify_stmt (&exit);
597 cont_block = begin_bc_block (bc_continue);
599 gimplify_stmt (&body);
600 if (incr && stmts_are_full_exprs_p ())
601 incr = fold (build1 (CLEANUP_POINT_EXPR, void_type_node, incr));
602 gimplify_stmt (&incr);
604 body = finish_bc_block (cont_block, body);
608 if (cond_is_first && cond)
610 entry = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
611 t = build_and_jump (&LABEL_EXPR_LABEL (entry));
612 append_to_statement_list (t, &stmt_list);
617 append_to_statement_list (top, &stmt_list);
618 append_to_statement_list (body, &stmt_list);
619 append_to_statement_list (incr, &stmt_list);
620 append_to_statement_list (entry, &stmt_list);
621 append_to_statement_list (exit, &stmt_list);
623 annotate_all_with_locus (&stmt_list, stmt_locus);
625 return finish_bc_block (break_block, stmt_list);
628 /* Gimplify a FOR_STMT node. Move the stuff in the for-init-stmt into the
629 prequeue and hand off to gimplify_c_loop. */
631 static enum gimplify_status
632 gimplify_for_stmt (tree *stmt_p, tree *pre_p)
636 if (FOR_INIT_STMT (stmt))
638 gimplify_stmt (&FOR_INIT_STMT (stmt));
639 append_to_statement_list (FOR_INIT_STMT (stmt), pre_p);
641 *stmt_p = gimplify_c_loop (FOR_COND (stmt), FOR_BODY (stmt),
647 /* Gimplify a WHILE_STMT node. */
649 static enum gimplify_status
650 gimplify_while_stmt (tree *stmt_p)
653 *stmt_p = gimplify_c_loop (WHILE_COND (stmt), WHILE_BODY (stmt),
658 /* Gimplify a DO_STMT node. */
660 static enum gimplify_status
661 gimplify_do_stmt (tree *stmt_p)
664 *stmt_p = gimplify_c_loop (DO_COND (stmt), DO_BODY (stmt),
669 /* Genericize an IF_STMT by turning it into a COND_EXPR. */
671 static enum gimplify_status
672 gimplify_if_stmt (tree *stmt_p)
674 tree stmt, then_, else_;
677 then_ = THEN_CLAUSE (stmt);
678 else_ = ELSE_CLAUSE (stmt);
681 then_ = build_empty_stmt ();
683 else_ = build_empty_stmt ();
685 stmt = build (COND_EXPR, void_type_node, IF_COND (stmt), then_, else_);
686 gimplify_condition (& TREE_OPERAND (stmt, 0));
692 /* Genericize a SWITCH_STMT by turning it into a SWITCH_EXPR. */
694 static enum gimplify_status
695 gimplify_switch_stmt (tree *stmt_p)
698 tree break_block, body;
699 location_t stmt_locus = input_location;
701 break_block = begin_bc_block (bc_break);
703 gimplify_condition (&SWITCH_COND (stmt));
705 body = SWITCH_BODY (stmt);
707 body = build_empty_stmt ();
709 *stmt_p = build (SWITCH_EXPR, SWITCH_TYPE (stmt), SWITCH_COND (stmt),
711 annotate_with_locus (*stmt_p, stmt_locus);
712 gimplify_stmt (stmt_p);
714 *stmt_p = finish_bc_block (break_block, *stmt_p);
718 /* Genericize a RETURN_STMT by turning it into a RETURN_EXPR. */
720 static enum gimplify_status
721 gimplify_return_stmt (tree *stmt_p)
723 tree expr = RETURN_STMT_EXPR (*stmt_p);
724 expr = build1 (RETURN_EXPR, void_type_node, expr);
725 if (stmts_are_full_exprs_p ())
726 expr = build1 (CLEANUP_POINT_EXPR, void_type_node, expr);
731 /* Gimplifies a DECL_STMT node *STMT_P by making any necessary allocation
732 and initialization explicit. */
734 static enum gimplify_status
735 gimplify_decl_stmt (tree *stmt_p)
738 tree decl = DECL_STMT_DECL (stmt);
739 tree pre = NULL_TREE;
740 tree post = NULL_TREE;
742 if (TREE_TYPE (decl) == error_mark_node)
748 if (TREE_CODE (decl) == TYPE_DECL)
750 tree type = TREE_TYPE (decl);
751 if (TYPE_SIZE_UNIT (type)
752 && !TREE_CONSTANT (TYPE_SIZE_UNIT (type)))
754 /* This is a variable-sized array type. Simplify its size. */
755 tree temp = TYPE_SIZE_UNIT (type);
756 gimplify_expr (&temp, &pre, &post, is_gimple_val, fb_rvalue);
760 if (TREE_CODE (decl) == VAR_DECL && !DECL_EXTERNAL (decl))
762 tree init = DECL_INITIAL (decl);
764 if (!TREE_CONSTANT (DECL_SIZE (decl)))
766 tree pt_type = build_pointer_type (TREE_TYPE (decl));
769 /* This is a variable-sized decl. Simplify its size and mark it
770 for deferred expansion. Note that mudflap depends on the format
771 of the emitted code: see mx_register_decls(). */
773 size = get_initialized_tmp_var (DECL_SIZE_UNIT (decl), &pre, &post);
774 DECL_DEFER_OUTPUT (decl) = 1;
775 alloc = build_function_call_expr
776 (implicit_built_in_decls[BUILT_IN_STACK_ALLOC],
777 tree_cons (NULL_TREE,
778 build1 (ADDR_EXPR, pt_type, decl),
779 tree_cons (NULL_TREE, size, NULL_TREE)));
780 append_to_compound_expr (alloc, &pre);
783 if (init && init != error_mark_node)
785 if (!TREE_STATIC (decl))
787 /* Do not warn about int x = x; as it is a GCC extension
788 to turn off this warning but only if warn_init_self
790 if (init == decl && !warn_init_self)
791 TREE_NO_WARNING (decl) = 1;
793 DECL_INITIAL (decl) = NULL_TREE;
794 init = build (MODIFY_EXPR, void_type_node, decl, init);
795 if (stmts_are_full_exprs_p ())
796 init = build1 (CLEANUP_POINT_EXPR, void_type_node, init);
797 append_to_compound_expr (init, &pre);
801 /* We must still examine initializers for static variables
802 as they may contain a label address. */
803 walk_tree (&init, force_labels_r, NULL, NULL);
807 /* This decl isn't mentioned in the enclosing block, so add it to the
808 list of temps. FIXME it seems a bit of a kludge to say that
809 anonymous artificial vars aren't pushed, but everything else is. */
810 if (DECL_ARTIFICIAL (decl) && DECL_NAME (decl) == NULL_TREE)
811 gimple_add_tmp_var (decl);
814 append_to_compound_expr (post, &pre);
819 /* Gimplification of expression trees. */
821 /* Gimplify a C99 compound literal expression. This just means adding the
822 DECL_STMT before the current EXPR_STMT and using its anonymous decl
825 static enum gimplify_status
826 gimplify_compound_literal_expr (tree *expr_p)
828 tree decl_s = COMPOUND_LITERAL_EXPR_DECL_STMT (*expr_p);
829 tree decl = DECL_STMT_DECL (decl_s);
831 /* This decl isn't mentioned in the enclosing block, so add it to the
832 list of temps. FIXME it seems a bit of a kludge to say that
833 anonymous artificial vars aren't pushed, but everything else is. */
834 if (DECL_NAME (decl) == NULL_TREE)
835 gimple_add_tmp_var (decl);
837 gimplify_decl_stmt (&decl_s);
838 *expr_p = decl_s ? decl_s : decl;
842 /* Do C-specific gimplification. Args are as for gimplify_expr. */
845 c_gimplify_expr (tree *expr_p, tree *pre_p ATTRIBUTE_UNUSED,
846 tree *post_p ATTRIBUTE_UNUSED)
848 enum tree_code code = TREE_CODE (*expr_p);
850 if (STATEMENT_CODE_P (code))
851 return c_gimplify_stmt (expr_p);
855 case COMPOUND_LITERAL_EXPR:
856 return gimplify_compound_literal_expr (expr_p);