1 /* Functions to analyze and validate GIMPLE trees.
2 Copyright (C) 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
4 Rewritten by Jason Merrill <jason@redhat.com>
5
6 This file is part of GCC.
7
8 GCC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
11 any later version.
12
13 GCC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
17
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to
20 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
21 Boston, MA 02110-1301, USA. */
22
23 #include "config.h"
24 #include "system.h"
25 #include "coretypes.h"
26 #include "ggc.h"
27 #include "tm.h"
28 #include "tree.h"
29 #include "tree-gimple.h"
30 #include "tree-flow.h"
31 #include "output.h"
32 #include "rtl.h"
33 #include "expr.h"
34 #include "bitmap.h"
35
36 /* For the definitive definition of GIMPLE, see doc/tree-ssa.texi. */
37
38 /* Validation of GIMPLE expressions. */
39
40 /* Return true if T is a GIMPLE RHS for an assignment to a temporary. */
41
42 bool
is_gimple_formal_tmp_rhs(tree t)43 is_gimple_formal_tmp_rhs (tree t)
44 {
45 enum tree_code code = TREE_CODE (t);
46
47 switch (TREE_CODE_CLASS (code))
48 {
49 case tcc_unary:
50 case tcc_binary:
51 case tcc_comparison:
52 return true;
53
54 default:
55 break;
56 }
57
58 switch (code)
59 {
60 case TRUTH_NOT_EXPR:
61 case TRUTH_AND_EXPR:
62 case TRUTH_OR_EXPR:
63 case TRUTH_XOR_EXPR:
64 case ADDR_EXPR:
65 case CALL_EXPR:
66 case CONSTRUCTOR:
67 case COMPLEX_EXPR:
68 case INTEGER_CST:
69 case REAL_CST:
70 case STRING_CST:
71 case COMPLEX_CST:
72 case VECTOR_CST:
73 case OBJ_TYPE_REF:
74 case ASSERT_EXPR:
75 return true;
76
77 default:
78 break;
79 }
80
81 return is_gimple_lvalue (t) || is_gimple_val (t);
82 }
83
84 /* Returns true iff T is a valid RHS for an assignment to a renamed
85 user -- or front-end generated artificial -- variable. */
86
87 bool
is_gimple_reg_rhs(tree t)88 is_gimple_reg_rhs (tree t)
89 {
90 /* If the RHS of the MODIFY_EXPR may throw or make a nonlocal goto
91 and the LHS is a user variable, then we need to introduce a formal
92 temporary. This way the optimizers can determine that the user
93 variable is only modified if evaluation of the RHS does not throw.
94
95 Don't force a temp of a non-renamable type; the copy could be
96 arbitrarily expensive. Instead we will generate a V_MAY_DEF for
97 the assignment. */
98
99 if (is_gimple_reg_type (TREE_TYPE (t))
100 && ((TREE_CODE (t) == CALL_EXPR && TREE_SIDE_EFFECTS (t))
101 || tree_could_throw_p (t)))
102 return false;
103
104 return is_gimple_formal_tmp_rhs (t);
105 }
106
107 /* Returns true iff T is a valid RHS for an assignment to an un-renamed
108 LHS, or for a call argument. */
109
110 bool
is_gimple_mem_rhs(tree t)111 is_gimple_mem_rhs (tree t)
112 {
113 /* If we're dealing with a renamable type, either source or dest must be
114 a renamed variable. Also force a temporary if the type doesn't need
115 to be stored in memory, since it's cheap and prevents erroneous
116 tailcalls (PR 17526). */
117 if (is_gimple_reg_type (TREE_TYPE (t))
118 || TYPE_MODE (TREE_TYPE (t)) != BLKmode)
119 return is_gimple_val (t);
120 else
121 return is_gimple_formal_tmp_rhs (t);
122 }
123
124 /* Returns the appropriate RHS predicate for this LHS. */
125
126 gimple_predicate
rhs_predicate_for(tree lhs)127 rhs_predicate_for (tree lhs)
128 {
129 if (is_gimple_formal_tmp_var (lhs))
130 return is_gimple_formal_tmp_rhs;
131 else if (is_gimple_reg (lhs))
132 return is_gimple_reg_rhs;
133 else
134 return is_gimple_mem_rhs;
135 }
136
137 /* Return true if T is a valid LHS for a GIMPLE assignment expression. */
138
139 bool
is_gimple_lvalue(tree t)140 is_gimple_lvalue (tree t)
141 {
142 return (is_gimple_addressable (t)
143 || TREE_CODE (t) == WITH_SIZE_EXPR
144 /* These are complex lvalues, but don't have addresses, so they
145 go here. */
146 || TREE_CODE (t) == BIT_FIELD_REF);
147 }
148
149 /* Return true if T is a GIMPLE condition. */
150
151 bool
is_gimple_condexpr(tree t)152 is_gimple_condexpr (tree t)
153 {
154 return (is_gimple_val (t) || COMPARISON_CLASS_P (t));
155 }
156
157 /* Return true if T is something whose address can be taken. */
158
159 bool
is_gimple_addressable(tree t)160 is_gimple_addressable (tree t)
161 {
162 return (is_gimple_id (t) || handled_component_p (t)
163 || INDIRECT_REF_P (t));
164 }
165
166 /* Return true if T is function invariant. Or rather a restricted
167 form of function invariant. */
168
169 bool
is_gimple_min_invariant(tree t)170 is_gimple_min_invariant (tree t)
171 {
172 switch (TREE_CODE (t))
173 {
174 case ADDR_EXPR:
175 return TREE_INVARIANT (t);
176
177 case INTEGER_CST:
178 case REAL_CST:
179 case STRING_CST:
180 case COMPLEX_CST:
181 case VECTOR_CST:
182 return true;
183
184 default:
185 return false;
186 }
187 }
188
189 /* Return true if T looks like a valid GIMPLE statement. */
190
191 bool
is_gimple_stmt(tree t)192 is_gimple_stmt (tree t)
193 {
194 enum tree_code code = TREE_CODE (t);
195
196 if (IS_EMPTY_STMT (t))
197 return 1;
198
199 switch (code)
200 {
201 case BIND_EXPR:
202 case COND_EXPR:
203 /* These are only valid if they're void. */
204 return TREE_TYPE (t) == NULL || VOID_TYPE_P (TREE_TYPE (t));
205
206 case SWITCH_EXPR:
207 case GOTO_EXPR:
208 case RETURN_EXPR:
209 case LABEL_EXPR:
210 case CASE_LABEL_EXPR:
211 case TRY_CATCH_EXPR:
212 case TRY_FINALLY_EXPR:
213 case EH_FILTER_EXPR:
214 case CATCH_EXPR:
215 case ASM_EXPR:
216 case RESX_EXPR:
217 case PHI_NODE:
218 case STATEMENT_LIST:
219 /* These are always void. */
220 return true;
221
222 case CALL_EXPR:
223 case MODIFY_EXPR:
224 /* These are valid regardless of their type. */
225 return true;
226
227 default:
228 return false;
229 }
230 }
231
232 /* Return true if T is a variable. */
233
234 bool
is_gimple_variable(tree t)235 is_gimple_variable (tree t)
236 {
237 return (TREE_CODE (t) == VAR_DECL
238 || TREE_CODE (t) == PARM_DECL
239 || TREE_CODE (t) == RESULT_DECL
240 || TREE_CODE (t) == SSA_NAME);
241 }
242
243 /* Return true if T is a GIMPLE identifier (something with an address). */
244
245 bool
is_gimple_id(tree t)246 is_gimple_id (tree t)
247 {
248 return (is_gimple_variable (t)
249 || TREE_CODE (t) == FUNCTION_DECL
250 || TREE_CODE (t) == LABEL_DECL
251 || TREE_CODE (t) == CONST_DECL
252 /* Allow string constants, since they are addressable. */
253 || TREE_CODE (t) == STRING_CST);
254 }
255
256 /* Return true if TYPE is a suitable type for a scalar register variable. */
257
258 bool
is_gimple_reg_type(tree type)259 is_gimple_reg_type (tree type)
260 {
261 return !AGGREGATE_TYPE_P (type);
262 }
263
264 /* Return true if T is a non-aggregate register variable. */
265
266 bool
is_gimple_reg(tree t)267 is_gimple_reg (tree t)
268 {
269 var_ann_t ann;
270
271 if (TREE_CODE (t) == SSA_NAME)
272 t = SSA_NAME_VAR (t);
273
274 if (!is_gimple_variable (t))
275 return false;
276
277 if (!is_gimple_reg_type (TREE_TYPE (t)))
278 return false;
279
280 /* A volatile decl is not acceptable because we can't reuse it as
281 needed. We need to copy it into a temp first. */
282 if (TREE_THIS_VOLATILE (t))
283 return false;
284
285 /* We define "registers" as things that can be renamed as needed,
286 which with our infrastructure does not apply to memory. */
287 if (needs_to_live_in_memory (t))
288 return false;
289
290 /* Hard register variables are an interesting case. For those that
291 are call-clobbered, we don't know where all the calls are, since
292 we don't (want to) take into account which operations will turn
293 into libcalls at the rtl level. For those that are call-saved,
294 we don't currently model the fact that calls may in fact change
295 global hard registers, nor do we examine ASM_CLOBBERS at the tree
296 level, and so miss variable changes that might imply. All around,
297 it seems safest to not do too much optimization with these at the
298 tree level at all. We'll have to rely on the rtl optimizers to
299 clean this up, as there we've got all the appropriate bits exposed. */
300 if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
301 return false;
302
303 /* Complex values must have been put into ssa form. That is, no
304 assignments to the individual components. */
305 if (TREE_CODE (TREE_TYPE (t)) == COMPLEX_TYPE)
306 return DECL_COMPLEX_GIMPLE_REG_P (t);
307
308 /* Some compiler temporaries are created to be used exclusively in
309 virtual operands (currently memory tags and sub-variables).
310 These variables should never be considered GIMPLE registers. */
311 if (DECL_ARTIFICIAL (t) && (ann = var_ann (t)) != NULL)
312 return ann->mem_tag_kind == NOT_A_TAG;
313
314 return true;
315 }
316
317
318 /* Returns true if T is a GIMPLE formal temporary variable. */
319
320 bool
is_gimple_formal_tmp_var(tree t)321 is_gimple_formal_tmp_var (tree t)
322 {
323 if (TREE_CODE (t) == SSA_NAME)
324 return true;
325
326 return TREE_CODE (t) == VAR_DECL && DECL_GIMPLE_FORMAL_TEMP_P (t);
327 }
328
329 /* Returns true if T is a GIMPLE formal temporary register variable. */
330
331 bool
is_gimple_formal_tmp_reg(tree t)332 is_gimple_formal_tmp_reg (tree t)
333 {
334 /* The intent of this is to get hold of a value that won't change.
335 An SSA_NAME qualifies no matter if its of a user variable or not. */
336 if (TREE_CODE (t) == SSA_NAME)
337 return true;
338
339 /* We don't know the lifetime characteristics of user variables. */
340 if (!is_gimple_formal_tmp_var (t))
341 return false;
342
343 /* Finally, it must be capable of being placed in a register. */
344 return is_gimple_reg (t);
345 }
346
347 /* Return true if T is a GIMPLE variable whose address is not needed. */
348
349 bool
is_gimple_non_addressable(tree t)350 is_gimple_non_addressable (tree t)
351 {
352 if (TREE_CODE (t) == SSA_NAME)
353 t = SSA_NAME_VAR (t);
354
355 return (is_gimple_variable (t) && ! needs_to_live_in_memory (t));
356 }
357
358 /* Return true if T is a GIMPLE rvalue, i.e. an identifier or a constant. */
359
360 bool
is_gimple_val(tree t)361 is_gimple_val (tree t)
362 {
363 /* Make loads from volatiles and memory vars explicit. */
364 if (is_gimple_variable (t)
365 && is_gimple_reg_type (TREE_TYPE (t))
366 && !is_gimple_reg (t))
367 return false;
368
369 /* FIXME make these decls. That can happen only when we expose the
370 entire landing-pad construct at the tree level. */
371 if (TREE_CODE (t) == EXC_PTR_EXPR || TREE_CODE (t) == FILTER_EXPR)
372 return 1;
373
374 return (is_gimple_variable (t) || is_gimple_min_invariant (t));
375 }
376
377 /* Similarly, but accept hard registers as inputs to asm statements. */
378
379 bool
is_gimple_asm_val(tree t)380 is_gimple_asm_val (tree t)
381 {
382 if (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t))
383 return true;
384
385 return is_gimple_val (t);
386 }
387
388 /* Return true if T is a GIMPLE minimal lvalue. */
389
390 bool
is_gimple_min_lval(tree t)391 is_gimple_min_lval (tree t)
392 {
393 return (is_gimple_id (t)
394 || TREE_CODE (t) == INDIRECT_REF);
395 }
396
397 /* Return true if T is a typecast operation. */
398
399 bool
is_gimple_cast(tree t)400 is_gimple_cast (tree t)
401 {
402 return (TREE_CODE (t) == NOP_EXPR
403 || TREE_CODE (t) == CONVERT_EXPR
404 || TREE_CODE (t) == FIX_TRUNC_EXPR
405 || TREE_CODE (t) == FIX_CEIL_EXPR
406 || TREE_CODE (t) == FIX_FLOOR_EXPR
407 || TREE_CODE (t) == FIX_ROUND_EXPR);
408 }
409
410 /* Return true if T is a valid op0 of a CALL_EXPR. */
411
412 bool
is_gimple_call_addr(tree t)413 is_gimple_call_addr (tree t)
414 {
415 return (TREE_CODE (t) == OBJ_TYPE_REF
416 || is_gimple_val (t));
417 }
418
419 /* If T makes a function call, return the corresponding CALL_EXPR operand.
420 Otherwise, return NULL_TREE. */
421
422 tree
get_call_expr_in(tree t)423 get_call_expr_in (tree t)
424 {
425 if (TREE_CODE (t) == MODIFY_EXPR)
426 t = TREE_OPERAND (t, 1);
427 if (TREE_CODE (t) == WITH_SIZE_EXPR)
428 t = TREE_OPERAND (t, 0);
429 if (TREE_CODE (t) == CALL_EXPR)
430 return t;
431 return NULL_TREE;
432 }
433
434 /* Given a memory reference expression T, return its base address.
435 The base address of a memory reference expression is the main
436 object being referenced. For instance, the base address for
437 'array[i].fld[j]' is 'array'. You can think of this as stripping
438 away the offset part from a memory address.
439
440 This function calls handled_component_p to strip away all the inner
441 parts of the memory reference until it reaches the base object. */
442
443 tree
get_base_address(tree t)444 get_base_address (tree t)
445 {
446 while (handled_component_p (t))
447 t = TREE_OPERAND (t, 0);
448
449 if (SSA_VAR_P (t)
450 || TREE_CODE (t) == STRING_CST
451 || TREE_CODE (t) == CONSTRUCTOR
452 || INDIRECT_REF_P (t))
453 return t;
454 else
455 return NULL_TREE;
456 }
457
458 void
recalculate_side_effects(tree t)459 recalculate_side_effects (tree t)
460 {
461 enum tree_code code = TREE_CODE (t);
462 int len = TREE_CODE_LENGTH (code);
463 int i;
464
465 switch (TREE_CODE_CLASS (code))
466 {
467 case tcc_expression:
468 switch (code)
469 {
470 case INIT_EXPR:
471 case MODIFY_EXPR:
472 case VA_ARG_EXPR:
473 case PREDECREMENT_EXPR:
474 case PREINCREMENT_EXPR:
475 case POSTDECREMENT_EXPR:
476 case POSTINCREMENT_EXPR:
477 /* All of these have side-effects, no matter what their
478 operands are. */
479 return;
480
481 default:
482 break;
483 }
484 /* Fall through. */
485
486 case tcc_comparison: /* a comparison expression */
487 case tcc_unary: /* a unary arithmetic expression */
488 case tcc_binary: /* a binary arithmetic expression */
489 case tcc_reference: /* a reference */
490 TREE_SIDE_EFFECTS (t) = TREE_THIS_VOLATILE (t);
491 for (i = 0; i < len; ++i)
492 {
493 tree op = TREE_OPERAND (t, i);
494 if (op && TREE_SIDE_EFFECTS (op))
495 TREE_SIDE_EFFECTS (t) = 1;
496 }
497 break;
498
499 default:
500 /* Can never be used with non-expressions. */
501 gcc_unreachable ();
502 }
503 }
504