1 /* Convert language-specific tree expression to rtl instructions,
2 for GNU compiler.
3 Copyright (C) 1988-2021 Free Software Foundation, Inc.
4
5 This file is part of GCC.
6
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
10 any later version.
11
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
20
21
22 #include "config.h"
23 #include "system.h"
24 #include "coretypes.h"
25 #include "cp-tree.h"
26
27 /* Expand C++-specific constants. Currently, this means PTRMEM_CST. */
28
29 tree
cplus_expand_constant(tree cst)30 cplus_expand_constant (tree cst)
31 {
32 switch (TREE_CODE (cst))
33 {
34 case PTRMEM_CST:
35 {
36 tree type = TREE_TYPE (cst);
37 tree member;
38
39 /* Find the member. */
40 member = PTRMEM_CST_MEMBER (cst);
41
42 /* We can't lower this until the class is complete. */
43 if (!COMPLETE_TYPE_P (DECL_CONTEXT (member)))
44 return cst;
45
46 if (TREE_CODE (member) == FIELD_DECL)
47 {
48 /* Find the offset for the field. */
49 cst = byte_position (member);
50 while (!same_type_p (DECL_CONTEXT (member),
51 TYPE_PTRMEM_CLASS_TYPE (type)))
52 {
53 /* The MEMBER must have been nestled within an
54 anonymous aggregate contained in TYPE. Find the
55 anonymous aggregate. */
56 member = lookup_anon_field (TYPE_PTRMEM_CLASS_TYPE (type),
57 DECL_CONTEXT (member));
58 cst = size_binop (PLUS_EXPR, cst, byte_position (member));
59 }
60 cst = fold (build_nop (type, cst));
61 }
62 else
63 {
64 tree delta;
65 tree pfn;
66
67 expand_ptrmemfunc_cst (cst, &delta, &pfn);
68 cst = build_ptrmemfunc1 (type, delta, pfn);
69 }
70 }
71 break;
72
73 case CONSTRUCTOR:
74 {
75 constructor_elt *elt;
76 unsigned HOST_WIDE_INT idx;
77 FOR_EACH_VEC_SAFE_ELT (CONSTRUCTOR_ELTS (cst), idx, elt)
78 elt->value = cplus_expand_constant (elt->value);
79 }
80
81 default:
82 /* There's nothing to do. */
83 break;
84 }
85
86 return cst;
87 }
88
89 /* We've seen an actual use of EXPR. Possibly replace an outer variable
90 reference inside with its constant value or a lambda capture. */
91
92 tree
mark_use(tree expr,bool rvalue_p,bool read_p,location_t loc,bool reject_builtin)93 mark_use (tree expr, bool rvalue_p, bool read_p,
94 location_t loc /* = UNKNOWN_LOCATION */,
95 bool reject_builtin /* = true */)
96 {
97 #define RECUR(t) mark_use ((t), rvalue_p, read_p, loc, reject_builtin)
98
99 if (expr == NULL_TREE || error_operand_p (expr))
100 return expr;
101
102 if (reject_builtin && reject_gcc_builtin (expr, loc))
103 return error_mark_node;
104
105 if (read_p)
106 mark_exp_read (expr);
107
108 tree oexpr = expr;
109 bool recurse_op[3] = { false, false, false };
110 switch (TREE_CODE (expr))
111 {
112 case VAR_DECL:
113 case PARM_DECL:
114 if (rvalue_p && is_normal_capture_proxy (expr))
115 {
116 /* Look through capture by copy. */
117 tree cap = DECL_CAPTURED_VARIABLE (expr);
118 if (TREE_CODE (TREE_TYPE (cap)) == TREE_CODE (TREE_TYPE (expr))
119 && decl_constant_var_p (cap))
120 {
121 tree val = RECUR (cap);
122 if (!is_capture_proxy (val))
123 {
124 tree l = current_lambda_expr ();
125 LAMBDA_EXPR_CAPTURE_OPTIMIZED (l) = true;
126 }
127 return val;
128 }
129 }
130 if (outer_automatic_var_p (expr)
131 && decl_constant_var_p (expr))
132 {
133 if (rvalue_p)
134 {
135 tree t = maybe_constant_value (expr);
136 if (TREE_CONSTANT (t))
137 {
138 expr = t;
139 break;
140 }
141 }
142 iloc_sentinel l (loc);
143 expr = process_outer_var_ref (expr, tf_warning_or_error, true);
144 if (!(TREE_TYPE (oexpr)
145 && TYPE_REF_P (TREE_TYPE (oexpr))))
146 expr = convert_from_reference (expr);
147 }
148 break;
149 case COMPONENT_REF:
150 case NON_DEPENDENT_EXPR:
151 recurse_op[0] = true;
152 break;
153 case COMPOUND_EXPR:
154 recurse_op[1] = true;
155 break;
156 case COND_EXPR:
157 recurse_op[2] = true;
158 if (TREE_OPERAND (expr, 1))
159 recurse_op[1] = true;
160 break;
161 case INDIRECT_REF:
162 if (REFERENCE_REF_P (expr))
163 {
164 /* Try to look through the reference. */
165 tree ref = TREE_OPERAND (expr, 0);
166 if (rvalue_p && is_normal_capture_proxy (ref))
167 {
168 /* Look through capture by reference. */
169 tree cap = DECL_CAPTURED_VARIABLE (ref);
170 if (!TYPE_REF_P (TREE_TYPE (cap))
171 && decl_constant_var_p (cap))
172 {
173 tree val = RECUR (cap);
174 if (!is_capture_proxy (val))
175 {
176 tree l = current_lambda_expr ();
177 LAMBDA_EXPR_CAPTURE_OPTIMIZED (l) = true;
178 }
179 return val;
180 }
181 }
182 tree r = mark_rvalue_use (ref, loc, reject_builtin);
183 if (r != ref)
184 expr = convert_from_reference (r);
185 }
186 break;
187
188 case VIEW_CONVERT_EXPR:
189 if (location_wrapper_p (expr))
190 {
191 loc = EXPR_LOCATION (expr);
192 tree op = TREE_OPERAND (expr, 0);
193 tree nop = RECUR (op);
194 if (nop == error_mark_node)
195 return error_mark_node;
196 else if (op == nop)
197 /* No change. */;
198 else if (DECL_P (nop) || CONSTANT_CLASS_P (nop))
199 {
200 /* Reuse the location wrapper. */
201 TREE_OPERAND (expr, 0) = nop;
202 /* If we're replacing a DECL with a constant, we also need to
203 change the TREE_CODE of the location wrapper. */
204 if (rvalue_p)
205 TREE_SET_CODE (expr, NON_LVALUE_EXPR);
206 }
207 else
208 {
209 /* Drop the location wrapper. */
210 expr = nop;
211 protected_set_expr_location (expr, loc);
212 }
213 return expr;
214 }
215 gcc_fallthrough();
216 CASE_CONVERT:
217 recurse_op[0] = true;
218 break;
219
220 case MODIFY_EXPR:
221 {
222 tree lhs = TREE_OPERAND (expr, 0);
223 /* [expr.ass] "A simple assignment whose left operand is of
224 a volatile-qualified type is deprecated unless the assignment
225 is either a discarded-value expression or appears in an
226 unevaluated context." */
227 if (!cp_unevaluated_operand
228 && (TREE_THIS_VOLATILE (lhs)
229 || CP_TYPE_VOLATILE_P (TREE_TYPE (lhs)))
230 && !TREE_THIS_VOLATILE (expr))
231 {
232 if (warning_at (location_of (expr), OPT_Wvolatile,
233 "using value of simple assignment with "
234 "%<volatile%>-qualified left operand is "
235 "deprecated"))
236 /* Make sure not to warn about this assignment again. */
237 TREE_THIS_VOLATILE (expr) = true;
238 }
239 break;
240 }
241
242 default:
243 break;
244 }
245
246 for (int i = 0; i < 3; ++i)
247 if (recurse_op[i])
248 {
249 tree op = TREE_OPERAND (expr, i);
250 op = RECUR (op);
251 if (op == error_mark_node)
252 return error_mark_node;
253 TREE_OPERAND (expr, i) = op;
254 }
255
256 return expr;
257 #undef RECUR
258 }
259
260 /* Called whenever the expression EXPR is used in an rvalue context.
261 When REJECT_BUILTIN is true the expression is checked to make sure
262 it doesn't make it possible to obtain the address of a GCC built-in
263 function with no library fallback (or any of its bits, such as in
264 a conversion to bool). */
265
266 tree
mark_rvalue_use(tree e,location_t loc,bool reject_builtin)267 mark_rvalue_use (tree e,
268 location_t loc /* = UNKNOWN_LOCATION */,
269 bool reject_builtin /* = true */)
270 {
271 return mark_use (e, true, true, loc, reject_builtin);
272 }
273
274 /* Called whenever an expression is used in an lvalue context. */
275
276 tree
mark_lvalue_use(tree expr)277 mark_lvalue_use (tree expr)
278 {
279 return mark_use (expr, false, true, input_location, false);
280 }
281
282 /* As above, but don't consider this use a read. */
283
284 tree
mark_lvalue_use_nonread(tree expr)285 mark_lvalue_use_nonread (tree expr)
286 {
287 return mark_use (expr, false, false, input_location, false);
288 }
289
290 /* Called when expr appears as a discarded-value expression. */
291
292 tree
mark_discarded_use(tree expr)293 mark_discarded_use (tree expr)
294 {
295 /* The lvalue-to-rvalue conversion (7.1) is applied if and only if the
296 expression is a glvalue of volatile-qualified type and it is one of the
297 following:
298 * ( expression ), where expression is one of these expressions,
299 * id-expression (8.1.4),
300 * subscripting (8.2.1),
301 * class member access (8.2.5),
302 * indirection (8.3.1),
303 * pointer-to-member operation (8.5),
304 * conditional expression (8.16) where both the second and the third
305 operands are one of these expressions, or
306 * comma expression (8.19) where the right operand is one of these
307 expressions. */
308 if (expr == NULL_TREE)
309 return expr;
310
311 STRIP_ANY_LOCATION_WRAPPER (expr);
312
313 switch (TREE_CODE (expr))
314 {
315 case COND_EXPR:
316 TREE_OPERAND (expr, 2) = mark_discarded_use (TREE_OPERAND (expr, 2));
317 gcc_fallthrough ();
318 case COMPOUND_EXPR:
319 TREE_OPERAND (expr, 1) = mark_discarded_use (TREE_OPERAND (expr, 1));
320 return expr;
321
322 case COMPONENT_REF:
323 case ARRAY_REF:
324 case INDIRECT_REF:
325 case MEMBER_REF:
326 break;
327 default:
328 if (DECL_P (expr))
329 break;
330 else
331 return expr;
332 }
333
334 /* Like mark_rvalue_use, but don't reject built-ins. */
335 return mark_use (expr, true, true, input_location, false);
336 }
337
338 /* Called whenever an expression is used in a type use context. */
339
340 tree
mark_type_use(tree expr)341 mark_type_use (tree expr)
342 {
343 mark_exp_read (expr);
344 return expr;
345 }
346
347 /* Mark EXP as read, not just set, for set but not used -Wunused
348 warning purposes. */
349
350 void
mark_exp_read(tree exp)351 mark_exp_read (tree exp)
352 {
353 if (exp == NULL)
354 return;
355
356 switch (TREE_CODE (exp))
357 {
358 case VAR_DECL:
359 if (DECL_DECOMPOSITION_P (exp))
360 mark_exp_read (DECL_DECOMP_BASE (exp));
361 gcc_fallthrough ();
362 case PARM_DECL:
363 DECL_READ_P (exp) = 1;
364 break;
365 case ARRAY_REF:
366 case COMPONENT_REF:
367 case MODIFY_EXPR:
368 case REALPART_EXPR:
369 case IMAGPART_EXPR:
370 CASE_CONVERT:
371 case ADDR_EXPR:
372 case INDIRECT_REF:
373 case FLOAT_EXPR:
374 case NON_DEPENDENT_EXPR:
375 case VIEW_CONVERT_EXPR:
376 mark_exp_read (TREE_OPERAND (exp, 0));
377 break;
378 case COMPOUND_EXPR:
379 mark_exp_read (TREE_OPERAND (exp, 1));
380 break;
381 case COND_EXPR:
382 if (TREE_OPERAND (exp, 1))
383 mark_exp_read (TREE_OPERAND (exp, 1));
384 if (TREE_OPERAND (exp, 2))
385 mark_exp_read (TREE_OPERAND (exp, 2));
386 break;
387 default:
388 break;
389 }
390 }
391
392 /* Fold X for consideration by one of the warning functions when checking
393 whether an expression has a constant value. */
394
395 tree
fold_for_warn(tree x)396 fold_for_warn (tree x)
397 {
398 /* C++ implementation. */
399
400 /* Prevent warning-dependent constexpr evaluation from changing
401 DECL_UID (which breaks -fcompare-debug) and from instantiating
402 templates. */
403 uid_sensitive_constexpr_evaluation_sentinel s;
404
405 /* It's not generally safe to fully fold inside of a template, so
406 call fold_non_dependent_expr instead. */
407 if (processing_template_decl)
408 {
409 tree f = fold_non_dependent_expr (x, tf_none);
410 if (f == error_mark_node)
411 return x;
412 else
413 return f;
414 }
415 else if (cxx_dialect >= cxx11)
416 x = maybe_constant_value (x);
417
418 return c_fully_fold (x, /*for_init*/false, /*maybe_constp*/NULL);
419 }
420