1 /* Tree lowering pass. Lowers GIMPLE into unstructured form.
3 Copyright (C) 2003 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
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
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, 59 Temple Place - Suite 330, Boston, MA
24 #include "coretypes.h"
30 #include "tree-gimple.h"
31 #include "tree-inline.h"
32 #include "diagnostic.h"
33 #include "langhooks.h"
34 #include "langhooks-def.h"
35 #include "tree-flow.h"
43 #include "tree-pass.h"
47 /* Block the current statement belongs to. */
50 /* Label that unifies the return statements. */
51 tree the_return_label;
55 static void lower_stmt (tree_stmt_iterator *, struct lower_data *);
56 static void lower_bind_expr (tree_stmt_iterator *, struct lower_data *);
57 static void lower_cond_expr (tree_stmt_iterator *, struct lower_data *);
58 static void lower_return_expr (tree_stmt_iterator *, struct lower_data *);
59 static bool expand_var_p (tree);
61 /* Lowers the body of current_function_decl. */
64 lower_function_body (void)
66 struct lower_data data;
67 tree *body_p = &DECL_SAVED_TREE (current_function_decl);
71 if (TREE_CODE (bind) != BIND_EXPR)
74 data.block = DECL_INITIAL (current_function_decl);
75 BLOCK_SUBBLOCKS (data.block) = NULL_TREE;
76 BLOCK_CHAIN (data.block) = NULL_TREE;
77 TREE_ASM_WRITTEN (data.block) = 1;
79 data.the_return_label = NULL_TREE;
80 data.one_return_stmt = NULL_TREE;
82 *body_p = alloc_stmt_list ();
83 i = tsi_start (*body_p);
84 tsi_link_after (&i, bind, TSI_NEW_STMT);
85 lower_bind_expr (&i, &data);
87 /* If we lowered any return statements, emit the representative at the
88 end of the function. */
89 if (data.one_return_stmt)
92 t = build (LABEL_EXPR, void_type_node, data.the_return_label);
93 i = tsi_last (*body_p);
94 tsi_link_after (&i, t, TSI_CONTINUE_LINKING);
95 tsi_link_after (&i, data.one_return_stmt, TSI_CONTINUE_LINKING);
98 if (data.block != DECL_INITIAL (current_function_decl))
100 BLOCK_SUBBLOCKS (data.block)
101 = blocks_nreverse (BLOCK_SUBBLOCKS (data.block));
103 clear_block_marks (data.block);
105 /* Avoid producing notes for blocks. */
106 cfun->dont_emit_block_notes = 1;
107 reset_block_changes ();
110 struct tree_opt_pass pass_lower_cf =
114 lower_function_body, /* execute */
117 0, /* static_pass_number */
119 PROP_gimple_any, /* properties_required */
120 PROP_gimple_lcf, /* properties_provided */
121 PROP_gimple_any, /* properties_destroyed */
122 0, /* todo_flags_start */
123 TODO_dump_func /* todo_flags_finish */
127 /* Lowers the EXPR. Unlike gimplification the statements are not relowered
128 when they are changed -- if this has to be done, the lowering routine must
129 do it explicitly. DATA is passed through the recursion. */
132 lower_stmt_body (tree expr, struct lower_data *data)
134 tree_stmt_iterator tsi;
136 for (tsi = tsi_start (expr); !tsi_end_p (tsi); )
137 lower_stmt (&tsi, data);
140 /* Lowers statement TSI. DATA is passed through the recursion. */
143 lower_stmt (tree_stmt_iterator *tsi, struct lower_data *data)
145 tree stmt = tsi_stmt (*tsi);
147 if (EXPR_HAS_LOCATION (stmt) && data)
148 TREE_BLOCK (stmt) = data->block;
150 switch (TREE_CODE (stmt))
153 lower_bind_expr (tsi, data);
156 lower_cond_expr (tsi, data);
159 lower_return_expr (tsi, data);
162 case TRY_FINALLY_EXPR:
164 lower_stmt_body (TREE_OPERAND (stmt, 0), data);
165 lower_stmt_body (TREE_OPERAND (stmt, 1), data);
168 lower_stmt_body (CATCH_BODY (stmt), data);
171 lower_stmt_body (EH_FILTER_FAILURE (stmt), data);
185 print_node_brief (stderr, "", stmt, 0);
193 /* Lowers a bind_expr TSI. DATA is passed through the recursion. */
196 lower_bind_expr (tree_stmt_iterator *tsi, struct lower_data *data)
198 tree old_block = data->block;
199 tree stmt = tsi_stmt (*tsi);
200 tree new_block = BIND_EXPR_BLOCK (stmt);
204 if (new_block == old_block)
206 /* The outermost block of the original function may not be the
207 outermost statement chain of the gimplified function. So we
208 may see the outermost block just inside the function. */
209 if (new_block != DECL_INITIAL (current_function_decl))
215 /* We do not expect to handle duplicate blocks. */
216 if (TREE_ASM_WRITTEN (new_block))
218 TREE_ASM_WRITTEN (new_block) = 1;
220 /* Block tree may get clobbered by inlining. Normally this would
221 be fixed in rest_of_decl_compilation using block notes, but
222 since we are not going to emit them, it is up to us. */
223 BLOCK_CHAIN (new_block) = BLOCK_SUBBLOCKS (old_block);
224 BLOCK_SUBBLOCKS (old_block) = new_block;
225 BLOCK_SUBBLOCKS (new_block) = NULL_TREE;
226 BLOCK_SUPERCONTEXT (new_block) = old_block;
228 data->block = new_block;
232 record_vars (BIND_EXPR_VARS (stmt));
233 lower_stmt_body (BIND_EXPR_BODY (stmt), data);
237 if (data->block != new_block)
240 BLOCK_SUBBLOCKS (new_block)
241 = blocks_nreverse (BLOCK_SUBBLOCKS (new_block));
242 data->block = old_block;
245 /* The BIND_EXPR no longer carries any useful information -- kill it. */
246 tsi_link_before (tsi, BIND_EXPR_BODY (stmt), TSI_SAME_STMT);
250 /* Try to determine if we can fall out of the bottom of BLOCK. This guess
251 need not be 100% accurate; simply be conservative and return true if we
252 don't know. This is used only to avoid stupidly generating extra code.
253 If we're wrong, we'll just delete the extra code later. */
256 block_may_fallthru (tree block)
258 tree stmt = expr_last (block);
260 switch (stmt ? TREE_CODE (stmt) : ERROR_MARK)
266 /* Easy cases. If the last statement of the block implies
267 control transfer, then we can't fall through. */
271 if (block_may_fallthru (COND_EXPR_THEN (stmt)))
273 return block_may_fallthru (COND_EXPR_ELSE (stmt));
276 return block_may_fallthru (BIND_EXPR_BODY (stmt));
278 case TRY_FINALLY_EXPR:
279 return block_may_fallthru (TREE_OPERAND (stmt, 1));
282 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR)
283 stmt = TREE_OPERAND (stmt, 1);
289 /* Functions that do not return do not fall through. */
290 return (call_expr_flags (stmt) & ECF_NORETURN) == 0;
297 /* Lowers a cond_expr TSI. DATA is passed through the recursion. */
300 lower_cond_expr (tree_stmt_iterator *tsi, struct lower_data *data)
302 tree stmt = tsi_stmt (*tsi);
303 bool then_is_goto, else_is_goto;
304 tree then_branch, else_branch;
305 tree then_goto, else_goto;
307 then_branch = COND_EXPR_THEN (stmt);
308 else_branch = COND_EXPR_ELSE (stmt);
310 lower_stmt_body (then_branch, data);
311 lower_stmt_body (else_branch, data);
313 then_goto = expr_only (then_branch);
314 then_is_goto = then_goto && simple_goto_p (then_goto);
316 else_goto = expr_only (else_branch);
317 else_is_goto = else_goto && simple_goto_p (else_goto);
319 if (!then_is_goto || !else_is_goto)
321 tree then_label, else_label, end_label, t;
323 then_label = NULL_TREE;
324 else_label = NULL_TREE;
325 end_label = NULL_TREE;
327 /* Replace the cond_expr with explicit gotos. */
330 t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
331 if (TREE_SIDE_EFFECTS (then_branch))
335 then_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
340 t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
341 if (TREE_SIDE_EFFECTS (else_branch))
345 /* Both THEN and ELSE can be no-ops if one or both contained an
346 empty BIND_EXPR that was associated with the toplevel block
347 of an inlined function. In that case remove_useless_stmts
348 can't have cleaned things up for us; kill the whole
358 else_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
363 bool may_fallthru = block_may_fallthru (then_branch);
365 tsi_link_after (tsi, then_label, TSI_CONTINUE_LINKING);
366 tsi_link_after (tsi, then_branch, TSI_CONTINUE_LINKING);
368 if (else_label && may_fallthru)
370 end_label = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
371 t = build_and_jump (&LABEL_EXPR_LABEL (end_label));
372 tsi_link_after (tsi, t, TSI_CONTINUE_LINKING);
378 tsi_link_after (tsi, else_label, TSI_CONTINUE_LINKING);
379 tsi_link_after (tsi, else_branch, TSI_CONTINUE_LINKING);
383 tsi_link_after (tsi, end_label, TSI_CONTINUE_LINKING);
386 COND_EXPR_THEN (stmt) = then_goto;
387 COND_EXPR_ELSE (stmt) = else_goto;
393 lower_return_expr (tree_stmt_iterator *tsi, struct lower_data *data)
395 tree stmt, label = data->the_return_label;
399 data->the_return_label = label = create_artificial_label ();
400 data->one_return_stmt = tsi_stmt (*tsi);
403 stmt = build (GOTO_EXPR, void_type_node, label);
404 tsi_link_before (tsi, stmt, TSI_SAME_STMT);
409 /* Record the variables in VARS. */
412 record_vars (tree vars)
414 for (; vars; vars = TREE_CHAIN (vars))
418 /* Nothing to do in this case. */
419 if (DECL_EXTERNAL (var))
421 if (TREE_CODE (var) == FUNCTION_DECL)
424 /* Record the variable. */
425 cfun->unexpanded_var_list = tree_cons (NULL_TREE, var,
426 cfun->unexpanded_var_list);
430 /* Check whether to expand a variable VAR. */
433 expand_var_p (tree var)
435 struct var_ann_d *ann;
437 if (TREE_CODE (var) != VAR_DECL)
442 /* Remove all unused, unaliased temporaries. Also remove unused, unaliased
443 local variables during highly optimizing compilations. */
446 && ! ann->may_aliases
448 && ! ann->has_hidden_use
449 && ! TREE_ADDRESSABLE (var)
450 && ! TREE_THIS_VOLATILE (var)
451 && (DECL_ARTIFICIAL (var) || optimize >= 2))
457 /* Throw away variables that are unused. */
460 remove_useless_vars (void)
464 for (cell = &cfun->unexpanded_var_list; *cell; )
466 var = TREE_VALUE (*cell);
468 if (!expand_var_p (var))
470 *cell = TREE_CHAIN (*cell);
474 cell = &TREE_CHAIN (*cell);
478 /* Expand variables in the unexpanded_var_list. */
481 expand_used_vars (void)
485 cfun->unexpanded_var_list = nreverse (cfun->unexpanded_var_list);
487 for (cell = cfun->unexpanded_var_list; cell; cell = TREE_CHAIN (cell))
488 expand_var (TREE_VALUE (cell));
490 cfun->unexpanded_var_list = NULL_TREE;
493 struct tree_opt_pass pass_remove_useless_vars =
497 remove_useless_vars, /* execute */
500 0, /* static_pass_number */
502 0, /* properties_required */
503 0, /* properties_provided */
504 0, /* properties_destroyed */
505 0, /* todo_flags_start */
506 TODO_dump_func /* todo_flags_finish */