1/* Convert language-specific tree expression to rtl instructions,
2 for GNU compiler.
3 Copyright (C) 1988-2024 Free Software Foundation, Inc.
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify
8it under the terms of the GNU General Public License as published by
9the Free Software Foundation; either version 3, or (at your option)
10any later version.
11
12GCC is distributed in the hope that it will be useful,
13but WITHOUT ANY WARRANTY; without even the implied warranty of
14MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15GNU General Public License for more details.
16
17You should have received a copy of the GNU General Public License
18along 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
29tree
30cplus_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 (cst: 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
92tree
93mark_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 (t: 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, force_use: 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 recurse_op[0] = true;
151 break;
152 case COMPOUND_EXPR:
153 recurse_op[1] = true;
154 break;
155 case COND_EXPR:
156 recurse_op[2] = true;
157 if (TREE_OPERAND (expr, 1))
158 recurse_op[1] = true;
159 break;
160 case INDIRECT_REF:
161 if (REFERENCE_REF_P (expr))
162 {
163 /* Try to look through the reference. */
164 tree ref = TREE_OPERAND (expr, 0);
165 if (rvalue_p && is_normal_capture_proxy (ref))
166 {
167 /* Look through capture by reference. */
168 tree cap = DECL_CAPTURED_VARIABLE (ref);
169 if (!TYPE_REF_P (TREE_TYPE (cap))
170 && decl_constant_var_p (cap))
171 {
172 tree val = RECUR (cap);
173 if (!is_capture_proxy (val))
174 {
175 tree l = current_lambda_expr ();
176 LAMBDA_EXPR_CAPTURE_OPTIMIZED (l) = true;
177 }
178 return val;
179 }
180 }
181 tree r = mark_rvalue_use (ref, loc, reject_builtin);
182 if (r != ref)
183 expr = convert_from_reference (r);
184 }
185 break;
186
187 case VIEW_CONVERT_EXPR:
188 if (location_wrapper_p (exp: expr))
189 {
190 loc = EXPR_LOCATION (expr);
191 tree op = TREE_OPERAND (expr, 0);
192 tree nop = RECUR (op);
193 if (nop == error_mark_node)
194 return error_mark_node;
195 else if (op == nop)
196 /* No change. */;
197 else if (DECL_P (nop) || CONSTANT_CLASS_P (nop))
198 {
199 /* Reuse the location wrapper. */
200 TREE_OPERAND (expr, 0) = nop;
201 /* If we're replacing a DECL with a constant, we also need to
202 change the TREE_CODE of the location wrapper. */
203 if (rvalue_p)
204 TREE_SET_CODE (expr, NON_LVALUE_EXPR);
205 }
206 else
207 {
208 /* Drop the location wrapper. */
209 expr = nop;
210 protected_set_expr_location (expr, loc);
211 }
212 return expr;
213 }
214 gcc_fallthrough();
215 CASE_CONVERT:
216 recurse_op[0] = true;
217 break;
218
219 case MODIFY_EXPR:
220 {
221 tree lhs = TREE_OPERAND (expr, 0);
222 /* [expr.ass] "An assignment whose left operand is of
223 a volatile-qualified type is deprecated unless the assignment
224 is either a discarded-value expression or appears in an
225 unevaluated context." */
226 if (!cp_unevaluated_operand
227 && (TREE_THIS_VOLATILE (lhs)
228 || CP_TYPE_VOLATILE_P (TREE_TYPE (lhs)))
229 && !TREE_THIS_VOLATILE (expr))
230 {
231 if (warning_at (location_of (expr), OPT_Wvolatile,
232 "using value of assignment with "
233 "%<volatile%>-qualified left operand is "
234 "deprecated"))
235 /* Make sure not to warn about this assignment again. */
236 TREE_THIS_VOLATILE (expr) = true;
237 }
238 break;
239 }
240
241 default:
242 break;
243 }
244
245 for (int i = 0; i < 3; ++i)
246 if (recurse_op[i])
247 {
248 tree op = TREE_OPERAND (expr, i);
249 op = RECUR (op);
250 if (op == error_mark_node)
251 return error_mark_node;
252 TREE_OPERAND (expr, i) = op;
253 }
254
255 return expr;
256#undef RECUR
257}
258
259/* Called whenever the expression EXPR is used in an rvalue context.
260 When REJECT_BUILTIN is true the expression is checked to make sure
261 it doesn't make it possible to obtain the address of a GCC built-in
262 function with no library fallback (or any of its bits, such as in
263 a conversion to bool). */
264
265tree
266mark_rvalue_use (tree e,
267 location_t loc /* = UNKNOWN_LOCATION */,
268 bool reject_builtin /* = true */)
269{
270 return mark_use (expr: e, rvalue_p: true, read_p: true, loc, reject_builtin);
271}
272
273/* Called whenever an expression is used in an lvalue context. */
274
275tree
276mark_lvalue_use (tree expr)
277{
278 return mark_use (expr, rvalue_p: false, read_p: true, loc: input_location, reject_builtin: false);
279}
280
281/* As above, but don't consider this use a read. */
282
283tree
284mark_lvalue_use_nonread (tree expr)
285{
286 return mark_use (expr, rvalue_p: false, read_p: false, loc: input_location, reject_builtin: false);
287}
288
289/* Called when expr appears as a discarded-value expression. */
290
291tree
292mark_discarded_use (tree expr)
293{
294 /* The lvalue-to-rvalue conversion (7.1) is applied if and only if the
295 expression is a glvalue of volatile-qualified type and it is one of the
296 following:
297 * ( expression ), where expression is one of these expressions,
298 * id-expression (8.1.4),
299 * subscripting (8.2.1),
300 * class member access (8.2.5),
301 * indirection (8.3.1),
302 * pointer-to-member operation (8.5),
303 * conditional expression (8.16) where both the second and the third
304 operands are one of these expressions, or
305 * comma expression (8.19) where the right operand is one of these
306 expressions. */
307 if (expr == NULL_TREE)
308 return expr;
309
310 STRIP_ANY_LOCATION_WRAPPER (expr);
311
312 switch (TREE_CODE (expr))
313 {
314 case COND_EXPR:
315 TREE_OPERAND (expr, 2) = mark_discarded_use (TREE_OPERAND (expr, 2));
316 gcc_fallthrough ();
317 case COMPOUND_EXPR:
318 TREE_OPERAND (expr, 1) = mark_discarded_use (TREE_OPERAND (expr, 1));
319 return expr;
320
321 case COMPONENT_REF:
322 case ARRAY_REF:
323 case INDIRECT_REF:
324 case MEMBER_REF:
325 break;
326 default:
327 if (DECL_P (expr))
328 break;
329 else
330 return expr;
331 }
332
333 /* Like mark_rvalue_use, but don't reject built-ins. */
334 return mark_use (expr, rvalue_p: true, read_p: true, loc: input_location, reject_builtin: false);
335}
336
337/* Called whenever an expression is used in a type use context. */
338
339tree
340mark_type_use (tree expr)
341{
342 mark_exp_read (expr);
343 return expr;
344}
345
346/* Mark EXP as read, not just set, for set but not used -Wunused
347 warning purposes. */
348
349void
350mark_exp_read (tree exp)
351{
352 if (exp == NULL)
353 return;
354
355 switch (TREE_CODE (exp))
356 {
357 case VAR_DECL:
358 if (DECL_DECOMPOSITION_P (exp))
359 mark_exp_read (DECL_DECOMP_BASE (exp));
360 gcc_fallthrough ();
361 case PARM_DECL:
362 DECL_READ_P (exp) = 1;
363 break;
364 case ARRAY_REF:
365 case COMPONENT_REF:
366 case MODIFY_EXPR:
367 case REALPART_EXPR:
368 case IMAGPART_EXPR:
369 CASE_CONVERT:
370 case ADDR_EXPR:
371 case INDIRECT_REF:
372 case FLOAT_EXPR:
373 case VIEW_CONVERT_EXPR:
374 mark_exp_read (TREE_OPERAND (exp, 0));
375 break;
376 case COMPOUND_EXPR:
377 mark_exp_read (TREE_OPERAND (exp, 1));
378 break;
379 case COND_EXPR:
380 if (TREE_OPERAND (exp, 1))
381 mark_exp_read (TREE_OPERAND (exp, 1));
382 if (TREE_OPERAND (exp, 2))
383 mark_exp_read (TREE_OPERAND (exp, 2));
384 break;
385 default:
386 break;
387 }
388}
389
390/* Fold X for consideration by one of the warning functions when checking
391 whether an expression has a constant value. */
392
393tree
394fold_for_warn (tree x)
395{
396 /* C++ implementation. */
397
398 if (cp_unevaluated_operand)
399 /* In an unevaluated context we don't care about the reduced value
400 of an expression, so neither should any warnings. */
401 return x;
402
403 /* Prevent warning-dependent constexpr evaluation from changing
404 DECL_UID (which breaks -fcompare-debug) and from instantiating
405 templates. */
406 uid_sensitive_constexpr_evaluation_sentinel s;
407
408 /* It's not generally safe to fully fold inside of a template, so
409 call fold_non_dependent_expr instead. */
410 if (processing_template_decl)
411 {
412 tree f = fold_non_dependent_expr (x, tf_none);
413 if (f == error_mark_node)
414 return x;
415 else
416 return f;
417 }
418 else if (cxx_dialect >= cxx11)
419 x = maybe_constant_value (x);
420
421 return c_fully_fold (x, /*for_init*/false, /*maybe_constp*/NULL);
422}
423

source code of gcc/cp/expr.cc