Remove tm.h and xm.h handling, as it wasn't used. Use nm.h only when needed.
[dragonfly.git] / contrib / gcc-4.1 / gcc / gimple-low.c
blob5c7c27f7e13f62e34ccdf66a814151952b8143f5
1 /* Tree lowering pass. Lowers GIMPLE into unstructured form.
3 Copyright (C) 2003, 2005 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
10 version.
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
20 02110-1301, USA. */
22 #include "config.h"
23 #include "system.h"
24 #include "coretypes.h"
25 #include "tm.h"
26 #include "tree.h"
27 #include "rtl.h"
28 #include "varray.h"
29 #include "tree-gimple.h"
30 #include "tree-inline.h"
31 #include "diagnostic.h"
32 #include "langhooks.h"
33 #include "langhooks-def.h"
34 #include "tree-flow.h"
35 #include "timevar.h"
36 #include "except.h"
37 #include "hashtab.h"
38 #include "flags.h"
39 #include "function.h"
40 #include "expr.h"
41 #include "toplev.h"
42 #include "tree-pass.h"
44 struct lower_data
46 /* Block the current statement belongs to. */
47 tree block;
49 /* A TREE_LIST of label and return statements to be moved to the end
50 of the function. */
51 tree return_statements;
54 static void lower_stmt (tree_stmt_iterator *, struct lower_data *);
55 static void lower_bind_expr (tree_stmt_iterator *, struct lower_data *);
56 static void lower_cond_expr (tree_stmt_iterator *, struct lower_data *);
57 static void lower_return_expr (tree_stmt_iterator *, struct lower_data *);
58 static bool expand_var_p (tree);
60 /* Lowers the body of current_function_decl. */
62 static void
63 lower_function_body (void)
65 struct lower_data data;
66 tree *body_p = &DECL_SAVED_TREE (current_function_decl);
67 tree bind = *body_p;
68 tree_stmt_iterator i;
69 tree t, x;
71 gcc_assert (TREE_CODE (bind) == BIND_EXPR);
73 data.block = DECL_INITIAL (current_function_decl);
74 BLOCK_SUBBLOCKS (data.block) = NULL_TREE;
75 BLOCK_CHAIN (data.block) = NULL_TREE;
76 TREE_ASM_WRITTEN (data.block) = 1;
78 data.return_statements = NULL_TREE;
80 *body_p = alloc_stmt_list ();
81 i = tsi_start (*body_p);
82 tsi_link_after (&i, bind, TSI_NEW_STMT);
83 lower_bind_expr (&i, &data);
85 i = tsi_last (*body_p);
87 /* If the function falls off the end, we need a null return statement.
88 If we've already got one in the return_statements list, we don't
89 need to do anything special. Otherwise build one by hand. */
90 if (block_may_fallthru (*body_p)
91 && (data.return_statements == NULL
92 || TREE_OPERAND (TREE_VALUE (data.return_statements), 0) != NULL))
94 x = build (RETURN_EXPR, void_type_node, NULL);
95 SET_EXPR_LOCATION (x, cfun->function_end_locus);
96 tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
99 /* If we lowered any return statements, emit the representative
100 at the end of the function. */
101 for (t = data.return_statements ; t ; t = TREE_CHAIN (t))
103 x = build (LABEL_EXPR, void_type_node, TREE_PURPOSE (t));
104 tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
106 /* Remove the line number from the representative return statement.
107 It now fills in for many such returns. Failure to remove this
108 will result in incorrect results for coverage analysis. */
109 x = TREE_VALUE (t);
110 #ifdef USE_MAPPED_LOCATION
111 SET_EXPR_LOCATION (x, UNKNOWN_LOCATION);
112 #else
113 SET_EXPR_LOCUS (x, NULL);
114 #endif
115 tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
118 gcc_assert (data.block == DECL_INITIAL (current_function_decl));
119 BLOCK_SUBBLOCKS (data.block)
120 = blocks_nreverse (BLOCK_SUBBLOCKS (data.block));
122 clear_block_marks (data.block);
125 struct tree_opt_pass pass_lower_cf =
127 "lower", /* name */
128 NULL, /* gate */
129 lower_function_body, /* execute */
130 NULL, /* sub */
131 NULL, /* next */
132 0, /* static_pass_number */
133 0, /* tv_id */
134 PROP_gimple_any, /* properties_required */
135 PROP_gimple_lcf, /* properties_provided */
136 PROP_gimple_any, /* properties_destroyed */
137 0, /* todo_flags_start */
138 TODO_dump_func, /* todo_flags_finish */
139 0 /* letter */
143 /* Lowers the EXPR. Unlike gimplification the statements are not relowered
144 when they are changed -- if this has to be done, the lowering routine must
145 do it explicitly. DATA is passed through the recursion. */
147 static void
148 lower_stmt_body (tree expr, struct lower_data *data)
150 tree_stmt_iterator tsi;
152 for (tsi = tsi_start (expr); !tsi_end_p (tsi); )
153 lower_stmt (&tsi, data);
156 /* Lowers statement TSI. DATA is passed through the recursion. */
158 static void
159 lower_stmt (tree_stmt_iterator *tsi, struct lower_data *data)
161 tree stmt = tsi_stmt (*tsi);
163 if (EXPR_HAS_LOCATION (stmt) && data)
164 TREE_BLOCK (stmt) = data->block;
166 switch (TREE_CODE (stmt))
168 case BIND_EXPR:
169 lower_bind_expr (tsi, data);
170 return;
171 case COND_EXPR:
172 lower_cond_expr (tsi, data);
173 return;
174 case RETURN_EXPR:
175 lower_return_expr (tsi, data);
176 return;
178 case TRY_FINALLY_EXPR:
179 case TRY_CATCH_EXPR:
180 lower_stmt_body (TREE_OPERAND (stmt, 0), data);
181 lower_stmt_body (TREE_OPERAND (stmt, 1), data);
182 break;
183 case CATCH_EXPR:
184 lower_stmt_body (CATCH_BODY (stmt), data);
185 break;
186 case EH_FILTER_EXPR:
187 lower_stmt_body (EH_FILTER_FAILURE (stmt), data);
188 break;
190 case NOP_EXPR:
191 case ASM_EXPR:
192 case MODIFY_EXPR:
193 case CALL_EXPR:
194 case GOTO_EXPR:
195 case LABEL_EXPR:
196 case SWITCH_EXPR:
197 break;
199 default:
200 #ifdef ENABLE_CHECKING
201 print_node_brief (stderr, "", stmt, 0);
202 internal_error ("unexpected node");
203 #endif
204 case COMPOUND_EXPR:
205 gcc_unreachable ();
208 tsi_next (tsi);
211 /* Lowers a bind_expr TSI. DATA is passed through the recursion. */
213 static void
214 lower_bind_expr (tree_stmt_iterator *tsi, struct lower_data *data)
216 tree old_block = data->block;
217 tree stmt = tsi_stmt (*tsi);
218 tree new_block = BIND_EXPR_BLOCK (stmt);
220 if (new_block)
222 if (new_block == old_block)
224 /* The outermost block of the original function may not be the
225 outermost statement chain of the gimplified function. So we
226 may see the outermost block just inside the function. */
227 gcc_assert (new_block == DECL_INITIAL (current_function_decl));
228 new_block = NULL;
230 else
232 /* We do not expect to handle duplicate blocks. */
233 gcc_assert (!TREE_ASM_WRITTEN (new_block));
234 TREE_ASM_WRITTEN (new_block) = 1;
236 /* Block tree may get clobbered by inlining. Normally this would
237 be fixed in rest_of_decl_compilation using block notes, but
238 since we are not going to emit them, it is up to us. */
239 BLOCK_CHAIN (new_block) = BLOCK_SUBBLOCKS (old_block);
240 BLOCK_SUBBLOCKS (old_block) = new_block;
241 BLOCK_SUBBLOCKS (new_block) = NULL_TREE;
242 BLOCK_SUPERCONTEXT (new_block) = old_block;
244 data->block = new_block;
248 record_vars (BIND_EXPR_VARS (stmt));
249 lower_stmt_body (BIND_EXPR_BODY (stmt), data);
251 if (new_block)
253 gcc_assert (data->block == new_block);
255 BLOCK_SUBBLOCKS (new_block)
256 = blocks_nreverse (BLOCK_SUBBLOCKS (new_block));
257 data->block = old_block;
260 /* The BIND_EXPR no longer carries any useful information -- kill it. */
261 tsi_link_before (tsi, BIND_EXPR_BODY (stmt), TSI_SAME_STMT);
262 tsi_delink (tsi);
265 /* Try to determine whether a TRY_CATCH expression can fall through.
266 This is a subroutine of block_may_fallthru. */
268 static bool
269 try_catch_may_fallthru (tree stmt)
271 tree_stmt_iterator i;
273 /* If the TRY block can fall through, the whole TRY_CATCH can
274 fall through. */
275 if (block_may_fallthru (TREE_OPERAND (stmt, 0)))
276 return true;
278 i = tsi_start (TREE_OPERAND (stmt, 1));
279 switch (TREE_CODE (tsi_stmt (i)))
281 case CATCH_EXPR:
282 /* We expect to see a sequence of CATCH_EXPR trees, each with a
283 catch expression and a body. The whole TRY_CATCH may fall
284 through iff any of the catch bodies falls through. */
285 for (; !tsi_end_p (i); tsi_next (&i))
287 if (block_may_fallthru (CATCH_BODY (tsi_stmt (i))))
288 return true;
290 return false;
292 case EH_FILTER_EXPR:
293 /* The exception filter expression only matters if there is an
294 exception. If the exception does not match EH_FILTER_TYPES,
295 we will execute EH_FILTER_FAILURE, and we will fall through
296 if that falls through. If the exception does match
297 EH_FILTER_TYPES, the stack unwinder will continue up the
298 stack, so we will not fall through. We don't know whether we
299 will throw an exception which matches EH_FILTER_TYPES or not,
300 so we just ignore EH_FILTER_TYPES and assume that we might
301 throw an exception which doesn't match. */
302 return block_may_fallthru (EH_FILTER_FAILURE (tsi_stmt (i)));
304 default:
305 /* This case represents statements to be executed when an
306 exception occurs. Those statements are implicitly followed
307 by a RESX_EXPR to resume execution after the exception. So
308 in this case the TRY_CATCH never falls through. */
309 return false;
313 /* Try to determine if we can fall out of the bottom of BLOCK. This guess
314 need not be 100% accurate; simply be conservative and return true if we
315 don't know. This is used only to avoid stupidly generating extra code.
316 If we're wrong, we'll just delete the extra code later. */
318 bool
319 block_may_fallthru (tree block)
321 tree stmt = expr_last (block);
323 switch (stmt ? TREE_CODE (stmt) : ERROR_MARK)
325 case GOTO_EXPR:
326 case RETURN_EXPR:
327 case RESX_EXPR:
328 /* Easy cases. If the last statement of the block implies
329 control transfer, then we can't fall through. */
330 return false;
332 case SWITCH_EXPR:
333 /* If SWITCH_LABELS is set, this is lowered, and represents a
334 branch to a selected label and hence can not fall through.
335 Otherwise SWITCH_BODY is set, and the switch can fall
336 through. */
337 return SWITCH_LABELS (stmt) == NULL_TREE;
339 case COND_EXPR:
340 if (block_may_fallthru (COND_EXPR_THEN (stmt)))
341 return true;
342 return block_may_fallthru (COND_EXPR_ELSE (stmt));
344 case BIND_EXPR:
345 return block_may_fallthru (BIND_EXPR_BODY (stmt));
347 case TRY_CATCH_EXPR:
348 return try_catch_may_fallthru (stmt);
350 case TRY_FINALLY_EXPR:
351 /* The finally clause is always executed after the try clause,
352 so if it does not fall through, then the try-finally will not
353 fall through. Otherwise, if the try clause does not fall
354 through, then when the finally clause falls through it will
355 resume execution wherever the try clause was going. So the
356 whole try-finally will only fall through if both the try
357 clause and the finally clause fall through. */
358 return (block_may_fallthru (TREE_OPERAND (stmt, 0))
359 && block_may_fallthru (TREE_OPERAND (stmt, 1)));
361 case MODIFY_EXPR:
362 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR)
363 stmt = TREE_OPERAND (stmt, 1);
364 else
365 return true;
366 /* FALLTHRU */
368 case CALL_EXPR:
369 /* Functions that do not return do not fall through. */
370 return (call_expr_flags (stmt) & ECF_NORETURN) == 0;
372 case CLEANUP_POINT_EXPR:
373 return block_may_fallthru (TREE_OPERAND (stmt, 0));
375 default:
376 return true;
380 /* Lowers a cond_expr TSI. DATA is passed through the recursion. */
382 static void
383 lower_cond_expr (tree_stmt_iterator *tsi, struct lower_data *data)
385 tree stmt = tsi_stmt (*tsi);
386 bool then_is_goto, else_is_goto;
387 tree then_branch, else_branch;
388 tree then_goto, else_goto;
390 then_branch = COND_EXPR_THEN (stmt);
391 else_branch = COND_EXPR_ELSE (stmt);
393 lower_stmt_body (then_branch, data);
394 lower_stmt_body (else_branch, data);
396 then_goto = expr_only (then_branch);
397 then_is_goto = then_goto && simple_goto_p (then_goto);
399 else_goto = expr_only (else_branch);
400 else_is_goto = else_goto && simple_goto_p (else_goto);
402 if (!then_is_goto || !else_is_goto)
404 tree then_label, else_label, end_label, t;
406 then_label = NULL_TREE;
407 else_label = NULL_TREE;
408 end_label = NULL_TREE;
410 /* Replace the cond_expr with explicit gotos. */
411 if (!then_is_goto)
413 t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
414 if (TREE_SIDE_EFFECTS (then_branch))
415 then_label = t;
416 else
417 end_label = t;
418 then_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
421 if (!else_is_goto)
423 t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
424 if (TREE_SIDE_EFFECTS (else_branch))
425 else_label = t;
426 else
428 /* Both THEN and ELSE can be no-ops if one or both contained an
429 empty BIND_EXPR that was associated with the toplevel block
430 of an inlined function. In that case remove_useless_stmts
431 can't have cleaned things up for us; kill the whole
432 conditional now. */
433 if (end_label)
435 tsi_delink (tsi);
436 return;
438 else
439 end_label = t;
441 else_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
444 if (then_label)
446 bool may_fallthru = block_may_fallthru (then_branch);
448 tsi_link_after (tsi, then_label, TSI_CONTINUE_LINKING);
449 tsi_link_after (tsi, then_branch, TSI_CONTINUE_LINKING);
451 if (else_label && may_fallthru)
453 end_label = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
454 t = build_and_jump (&LABEL_EXPR_LABEL (end_label));
455 tsi_link_after (tsi, t, TSI_CONTINUE_LINKING);
459 if (else_label)
461 tsi_link_after (tsi, else_label, TSI_CONTINUE_LINKING);
462 tsi_link_after (tsi, else_branch, TSI_CONTINUE_LINKING);
465 if (end_label)
466 tsi_link_after (tsi, end_label, TSI_CONTINUE_LINKING);
469 COND_EXPR_THEN (stmt) = then_goto;
470 COND_EXPR_ELSE (stmt) = else_goto;
472 tsi_next (tsi);
475 static void
476 lower_return_expr (tree_stmt_iterator *tsi, struct lower_data *data)
478 tree stmt = tsi_stmt (*tsi);
479 tree value, t, label;
481 /* Extract the value being returned. */
482 value = TREE_OPERAND (stmt, 0);
483 if (value && TREE_CODE (value) == MODIFY_EXPR)
484 value = TREE_OPERAND (value, 1);
486 /* Match this up with an existing return statement that's been created. */
487 for (t = data->return_statements; t ; t = TREE_CHAIN (t))
489 tree tvalue = TREE_OPERAND (TREE_VALUE (t), 0);
490 if (tvalue && TREE_CODE (tvalue) == MODIFY_EXPR)
491 tvalue = TREE_OPERAND (tvalue, 1);
493 if (value == tvalue)
495 label = TREE_PURPOSE (t);
496 goto found;
500 /* Not found. Create a new label and record the return statement. */
501 label = create_artificial_label ();
502 data->return_statements = tree_cons (label, stmt, data->return_statements);
504 /* Generate a goto statement and remove the return statement. */
505 found:
506 t = build (GOTO_EXPR, void_type_node, label);
507 SET_EXPR_LOCUS (t, EXPR_LOCUS (stmt));
508 tsi_link_before (tsi, t, TSI_SAME_STMT);
509 tsi_delink (tsi);
513 /* Record the variables in VARS. */
515 void
516 record_vars (tree vars)
518 for (; vars; vars = TREE_CHAIN (vars))
520 tree var = vars;
522 /* BIND_EXPRs contains also function/type/constant declarations
523 we don't need to care about. */
524 if (TREE_CODE (var) != VAR_DECL)
525 continue;
526 /* Nothing to do in this case. */
527 if (DECL_EXTERNAL (var))
528 continue;
530 /* Record the variable. */
531 cfun->unexpanded_var_list = tree_cons (NULL_TREE, var,
532 cfun->unexpanded_var_list);
536 /* Check whether to expand a variable VAR. */
538 static bool
539 expand_var_p (tree var)
541 struct var_ann_d *ann;
543 if (TREE_CODE (var) != VAR_DECL)
544 return true;
546 /* Leave statics and externals alone. */
547 if (TREE_STATIC (var) || DECL_EXTERNAL (var))
548 return true;
550 /* Remove all unused local variables. */
551 ann = var_ann (var);
552 if (!ann || !ann->used)
553 return false;
555 return true;
558 /* Throw away variables that are unused. */
560 static void
561 remove_useless_vars (void)
563 tree var, *cell;
564 FILE *df = NULL;
566 if (dump_file && (dump_flags & TDF_DETAILS))
568 df = dump_file;
569 fputs ("Discarding as unused:\n", df);
572 for (cell = &cfun->unexpanded_var_list; *cell; )
574 var = TREE_VALUE (*cell);
576 if (!expand_var_p (var))
578 if (df)
580 fputs (" ", df);
581 print_generic_expr (df, var, dump_flags);
582 fputc ('\n', df);
585 *cell = TREE_CHAIN (*cell);
586 continue;
589 cell = &TREE_CHAIN (*cell);
592 if (df)
593 fputc ('\n', df);
596 struct tree_opt_pass pass_remove_useless_vars =
598 "vars", /* name */
599 NULL, /* gate */
600 remove_useless_vars, /* execute */
601 NULL, /* sub */
602 NULL, /* next */
603 0, /* static_pass_number */
604 0, /* tv_id */
605 0, /* properties_required */
606 0, /* properties_provided */
607 0, /* properties_destroyed */
608 0, /* todo_flags_start */
609 TODO_dump_func, /* todo_flags_finish */
610 0 /* letter */
613 /* Mark BLOCK used if it has a used variable in it, then recurse over its
614 subblocks. */
616 static void
617 mark_blocks_with_used_vars (tree block)
619 tree var;
620 tree subblock;
622 if (!TREE_USED (block))
624 for (var = BLOCK_VARS (block);
625 var;
626 var = TREE_CHAIN (var))
628 if (TREE_USED (var))
630 TREE_USED (block) = true;
631 break;
635 for (subblock = BLOCK_SUBBLOCKS (block);
636 subblock;
637 subblock = BLOCK_CHAIN (subblock))
638 mark_blocks_with_used_vars (subblock);
641 /* Mark the used attribute on blocks correctly. */
643 static void
644 mark_used_blocks (void)
646 mark_blocks_with_used_vars (DECL_INITIAL (current_function_decl));
650 struct tree_opt_pass pass_mark_used_blocks =
652 "blocks", /* name */
653 NULL, /* gate */
654 mark_used_blocks, /* execute */
655 NULL, /* sub */
656 NULL, /* next */
657 0, /* static_pass_number */
658 0, /* tv_id */
659 0, /* properties_required */
660 0, /* properties_provided */
661 0, /* properties_destroyed */
662 0, /* todo_flags_start */
663 TODO_dump_func, /* todo_flags_finish */
664 0 /* letter */