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 enum bc_t { bc_break = 0, bc_continue = 1 };
77 static struct c_gimplify_ctx
79 /* For handling break and continue. */
80 tree current_bc_label;
89 ctxp = (struct c_gimplify_ctx *) xcalloc (1, sizeof (struct c_gimplify_ctx));
90 ctxp->bc_id[bc_continue] = get_identifier ("continue");
91 ctxp->bc_id[bc_break] = get_identifier ("break");
97 if (!ctxp || ctxp->current_bc_label)
103 /* Gimplification of statement trees. */
105 /* Convert the tree representation of FNDECL from C frontend trees to
109 c_genericize (tree fndecl)
112 int local_dump_flags;
113 struct cgraph_node *cgn;
115 /* Dump the C-specific tree IR. */
116 dump_file = dump_begin (TDI_original, &local_dump_flags);
119 fprintf (dump_file, "\n;; Function %s",
120 lang_hooks.decl_printable_name (fndecl, 2));
121 fprintf (dump_file, " (%s)\n",
122 IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl)));
123 fprintf (dump_file, ";; enabled by -%s\n", dump_flag_name (TDI_original));
124 fprintf (dump_file, "\n");
126 if (local_dump_flags & TDF_RAW)
127 dump_node (DECL_SAVED_TREE (fndecl),
128 TDF_SLIM | local_dump_flags, dump_file);
130 print_c_tree (dump_file, DECL_SAVED_TREE (fndecl));
131 fprintf (dump_file, "\n");
133 dump_end (TDI_original, dump_file);
136 /* Go ahead and gimplify for now. */
138 gimplify_function_tree (fndecl);
141 /* Dump the genericized tree IR. */
142 dump_function (TDI_generic, fndecl);
144 /* Genericize all nested functions now. We do things in this order so
145 that items like VLA sizes are expanded properly in the context of
146 the correct function. */
147 cgn = cgraph_node (fndecl);
148 for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
149 c_genericize (cgn->decl);
153 add_block_to_enclosing (tree block)
157 for (enclosing = gimple_current_bind_expr ();
158 enclosing; enclosing = TREE_CHAIN (enclosing))
159 if (BIND_EXPR_BLOCK (enclosing))
162 enclosing = BIND_EXPR_BLOCK (enclosing);
163 BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
166 /* Genericize a scope by creating a new BIND_EXPR.
167 BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
168 In the latter case, we need to create a new BLOCK and add it to the
169 BLOCK_SUBBLOCKS of the enclosing block.
170 BODY is a chain of C _STMT nodes for the contents of the scope, to be
174 c_build_bind_expr (tree block, tree body)
178 if (block == NULL_TREE)
180 else if (TREE_CODE (block) == BLOCK)
181 decls = BLOCK_VARS (block);
185 if (DECL_ARTIFICIAL (decls))
189 block = make_node (BLOCK);
190 BLOCK_VARS (block) = decls;
191 add_block_to_enclosing (block);
196 body = build_empty_stmt ();
199 bind = build (BIND_EXPR, void_type_node, decls, body, block);
200 TREE_SIDE_EFFECTS (bind) = 1;
208 /* Gimplify an EXPR_STMT node.
210 STMT is the statement node.
212 PRE_P points to the list where side effects that must happen before
213 STMT should be stored.
215 POST_P points to the list where side effects that must happen after
216 STMT should be stored. */
218 static enum gimplify_status
219 gimplify_expr_stmt (tree *stmt_p)
221 tree stmt = EXPR_STMT_EXPR (*stmt_p);
223 if (stmt == error_mark_node)
226 /* Gimplification of a statement expression will nullify the
227 statement if all its side effects are moved to *PRE_P and *POST_P.
229 In this case we will not want to emit the gimplified statement.
230 However, we may still want to emit a warning, so we do that before
232 if (stmt && (extra_warnings || warn_unused_value))
234 if (!TREE_SIDE_EFFECTS (stmt))
236 if (!IS_EMPTY_STMT (stmt)
237 && !VOID_TYPE_P (TREE_TYPE (stmt))
238 && !TREE_NO_WARNING (stmt))
239 warning ("statement with no effect");
241 else if (warn_unused_value)
242 warn_if_unused_value (stmt, input_location);
245 if (stmt == NULL_TREE)
246 stmt = build_empty_stmt ();
253 /* Begin a scope which can be exited by a break or continue statement. BC
256 Just creates a label and pushes it into the current context. */
259 begin_bc_block (enum bc_t bc)
261 tree label = create_artificial_label ();
262 DECL_NAME (label) = ctxp->bc_id[bc];
263 TREE_CHAIN (label) = ctxp->current_bc_label;
264 ctxp->current_bc_label = label;
268 /* Finish a scope which can be exited by a break or continue statement.
269 LABEL was returned from the most recent call to begin_bc_block. BODY is
270 an expression for the contents of the scope.
272 If we saw a break (or continue) in the scope, append a LABEL_EXPR to
273 body. Otherwise, just forget the label. */
276 finish_bc_block (tree label, tree body)
278 if (label != ctxp->current_bc_label)
281 if (TREE_USED (label))
285 /* Clear the name so flow can delete the label. */
286 DECL_NAME (label) = NULL_TREE;
287 t = build1 (LABEL_EXPR, void_type_node, label);
289 append_to_statement_list (body, &sl);
290 append_to_statement_list (t, &sl);
294 ctxp->current_bc_label = TREE_CHAIN (label);
295 TREE_CHAIN (label) = NULL_TREE;
299 /* Build a GOTO_EXPR to represent a break or continue statement. BC
303 build_bc_goto (enum bc_t bc)
306 tree target_name = ctxp->bc_id[bc];
308 /* Look for the appropriate type of label. */
309 for (label = ctxp->current_bc_label;
311 label = TREE_CHAIN (label))
312 if (DECL_NAME (label) == target_name)
315 if (label == NULL_TREE)
318 error ("break statement not within loop or switch");
320 error ("continue statement not within loop or switch");
325 /* Mark the label used for finish_bc_block. */
326 TREE_USED (label) = 1;
327 return build1 (GOTO_EXPR, void_type_node, label);
330 /* Build a generic representation of one of the C loop forms. COND is the
331 loop condition or NULL_TREE. BODY is the (possibly compound) statement
332 controlled by the loop. INCR is the increment expression of a for-loop,
333 or NULL_TREE. COND_IS_FIRST indicates whether the condition is
334 evaluated before the loop body as in while and for loops, or after the
335 loop body as in do-while loops. */
338 gimplify_c_loop (tree cond, tree body, tree incr, bool cond_is_first)
340 tree top, entry, exit, cont_block, break_block, stmt_list, t;
341 location_t stmt_locus;
343 stmt_locus = input_location;
345 /* Detect do { ... } while (0) and don't generate loop construct. */
346 if (!cond_is_first && cond && integer_zerop (cond))
350 /* If we use a LOOP_EXPR here, we have to feed the whole thing
351 back through the main gimplifier to lower it. Given that we
352 have to gimplify the loop body NOW so that we can resolve
353 break/continue stmts, seems easier to just expand to gotos. */
354 top = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
357 break_block = begin_bc_block (bc_break);
361 /* If we have an exit condition, then we build an IF with gotos either
362 out of the loop, or to the top of it. If there's no exit condition,
363 then we just build a jump back to the top. */
364 exit = build_and_jump (&LABEL_EXPR_LABEL (top));
367 t = build_bc_goto (bc_break);
368 exit = build (COND_EXPR, void_type_node, cond, exit, t);
370 gimplify_stmt (&exit);
376 cont_block = begin_bc_block (bc_continue);
378 gimplify_stmt (&body);
379 gimplify_stmt (&incr);
381 body = finish_bc_block (cont_block, body);
385 if (cond_is_first && cond)
387 entry = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
388 t = build_and_jump (&LABEL_EXPR_LABEL (entry));
389 append_to_statement_list (t, &stmt_list);
394 append_to_statement_list (top, &stmt_list);
395 append_to_statement_list (body, &stmt_list);
396 append_to_statement_list (incr, &stmt_list);
397 append_to_statement_list (entry, &stmt_list);
398 append_to_statement_list (exit, &stmt_list);
400 annotate_all_with_locus (&stmt_list, stmt_locus);
402 return finish_bc_block (break_block, stmt_list);
405 /* Gimplify a FOR_STMT node. Move the stuff in the for-init-stmt into the
406 prequeue and hand off to gimplify_c_loop. */
408 static enum gimplify_status
409 gimplify_for_stmt (tree *stmt_p, tree *pre_p)
413 if (FOR_INIT_STMT (stmt))
415 gimplify_stmt (&FOR_INIT_STMT (stmt));
416 append_to_statement_list (FOR_INIT_STMT (stmt), pre_p);
418 *stmt_p = gimplify_c_loop (FOR_COND (stmt), FOR_BODY (stmt),
424 /* Gimplify a WHILE_STMT node. */
426 static enum gimplify_status
427 gimplify_while_stmt (tree *stmt_p)
430 *stmt_p = gimplify_c_loop (WHILE_COND (stmt), WHILE_BODY (stmt),
435 /* Gimplify a DO_STMT node. */
437 static enum gimplify_status
438 gimplify_do_stmt (tree *stmt_p)
441 *stmt_p = gimplify_c_loop (DO_COND (stmt), DO_BODY (stmt),
446 /* Genericize a SWITCH_STMT by turning it into a SWITCH_EXPR. */
448 static enum gimplify_status
449 gimplify_switch_stmt (tree *stmt_p)
452 tree break_block, body;
453 location_t stmt_locus = input_location;
455 break_block = begin_bc_block (bc_break);
457 body = SWITCH_BODY (stmt);
459 body = build_empty_stmt ();
461 *stmt_p = build (SWITCH_EXPR, SWITCH_TYPE (stmt), SWITCH_COND (stmt),
463 annotate_with_locus (*stmt_p, stmt_locus);
464 gimplify_stmt (stmt_p);
466 *stmt_p = finish_bc_block (break_block, *stmt_p);
470 /* Genericize a RETURN_STMT by turning it into a RETURN_EXPR. */
472 static enum gimplify_status
473 gimplify_return_stmt (tree *stmt_p)
475 tree expr = RETURN_STMT_EXPR (*stmt_p);
476 expr = build1 (RETURN_EXPR, void_type_node, expr);
481 /* Gimplifies a DECL_STMT node *STMT_P by making any necessary allocation
482 and initialization explicit. */
484 static enum gimplify_status
485 gimplify_decl_stmt (tree *stmt_p)
488 tree decl = DECL_STMT_DECL (stmt);
489 tree pre = NULL_TREE;
490 tree post = NULL_TREE;
492 if (TREE_TYPE (decl) == error_mark_node)
498 if (TREE_CODE (decl) == TYPE_DECL)
500 tree type = TREE_TYPE (decl);
501 if (TYPE_SIZE_UNIT (type)
502 && !TREE_CONSTANT (TYPE_SIZE_UNIT (type)))
504 /* This is a variable-sized array type. Simplify its size. */
505 tree temp = TYPE_SIZE_UNIT (type);
506 gimplify_expr (&temp, &pre, &post, is_gimple_val, fb_rvalue);
510 if (TREE_CODE (decl) == VAR_DECL && !DECL_EXTERNAL (decl))
512 tree init = DECL_INITIAL (decl);
514 if (!TREE_CONSTANT (DECL_SIZE (decl)))
516 tree pt_type = build_pointer_type (TREE_TYPE (decl));
519 /* This is a variable-sized decl. Simplify its size and mark it
520 for deferred expansion. Note that mudflap depends on the format
521 of the emitted code: see mx_register_decls(). */
523 size = get_initialized_tmp_var (DECL_SIZE_UNIT (decl), &pre, &post);
524 DECL_DEFER_OUTPUT (decl) = 1;
525 alloc = build_function_call_expr
526 (implicit_built_in_decls[BUILT_IN_STACK_ALLOC],
527 tree_cons (NULL_TREE,
528 build1 (ADDR_EXPR, pt_type, decl),
529 tree_cons (NULL_TREE, size, NULL_TREE)));
530 append_to_compound_expr (alloc, &pre);
533 if (init && init != error_mark_node)
535 if (!TREE_STATIC (decl))
537 /* Do not warn about int x = x; as it is a GCC extension
538 to turn off this warning but only if warn_init_self
540 if (init == decl && !warn_init_self)
541 TREE_NO_WARNING (decl) = 1;
543 DECL_INITIAL (decl) = NULL_TREE;
544 init = build (MODIFY_EXPR, void_type_node, decl, init);
545 append_to_compound_expr (init, &pre);
549 /* We must still examine initializers for static variables
550 as they may contain a label address. */
551 walk_tree (&init, force_labels_r, NULL, NULL);
555 /* This decl isn't mentioned in the enclosing block, so add it to the
556 list of temps. FIXME it seems a bit of a kludge to say that
557 anonymous artificial vars aren't pushed, but everything else is. */
558 if (DECL_ARTIFICIAL (decl) && DECL_NAME (decl) == NULL_TREE)
559 gimple_add_tmp_var (decl);
562 append_to_compound_expr (post, &pre);
567 /* Gimplification of expression trees. */
569 /* Gimplify a C99 compound literal expression. This just means adding the
570 DECL_STMT before the current EXPR_STMT and using its anonymous decl
573 static enum gimplify_status
574 gimplify_compound_literal_expr (tree *expr_p)
576 tree decl_s = COMPOUND_LITERAL_EXPR_DECL_STMT (*expr_p);
577 tree decl = DECL_STMT_DECL (decl_s);
579 /* This decl isn't mentioned in the enclosing block, so add it to the
580 list of temps. FIXME it seems a bit of a kludge to say that
581 anonymous artificial vars aren't pushed, but everything else is. */
582 if (DECL_NAME (decl) == NULL_TREE)
583 gimple_add_tmp_var (decl);
585 gimplify_decl_stmt (&decl_s);
586 *expr_p = decl_s ? decl_s : decl;
590 /* Do C-specific gimplification. Args are as for gimplify_expr. */
593 c_gimplify_expr (tree *expr_p, tree *pre_p, tree *post_p ATTRIBUTE_UNUSED)
595 enum tree_code code = TREE_CODE (*expr_p);
599 case COMPOUND_LITERAL_EXPR:
600 return gimplify_compound_literal_expr (expr_p);
603 return gimplify_for_stmt (expr_p, pre_p);
606 return gimplify_while_stmt (expr_p);
609 return gimplify_do_stmt (expr_p);
612 return gimplify_switch_stmt (expr_p);
615 return gimplify_expr_stmt (expr_p);
618 return gimplify_return_stmt (expr_p);
621 return gimplify_decl_stmt (expr_p);
624 *expr_p = build_bc_goto (bc_continue);
628 *expr_p = build_bc_goto (bc_break);