1 /* Convert language-specific tree expression to rtl instructions,
2 for GNU compiler.
3 Copyright (C) 1988-2020 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 temp_override<location_t> l (input_location);
143 if (loc != UNKNOWN_LOCATION)
144 input_location = loc;
145 expr = process_outer_var_ref (expr, tf_warning_or_error, true);
146 if (!(TREE_TYPE (oexpr)
147 && TYPE_REF_P (TREE_TYPE (oexpr))))
148 expr = convert_from_reference (expr);
149 }
150 break;
151 case COMPONENT_REF:
152 case NON_DEPENDENT_EXPR:
153 recurse_op[0] = true;
154 break;
155 case COMPOUND_EXPR:
156 recurse_op[1] = true;
157 break;
158 case COND_EXPR:
159 recurse_op[2] = true;
160 if (TREE_OPERAND (expr, 1))
161 recurse_op[1] = true;
162 break;
163 case INDIRECT_REF:
164 if (REFERENCE_REF_P (expr))
165 {
166 /* Try to look through the reference. */
167 tree ref = TREE_OPERAND (expr, 0);
168 if (rvalue_p && is_normal_capture_proxy (ref))
169 {
170 /* Look through capture by reference. */
171 tree cap = DECL_CAPTURED_VARIABLE (ref);
172 if (!TYPE_REF_P (TREE_TYPE (cap))
173 && decl_constant_var_p (cap))
174 {
175 tree val = RECUR (cap);
176 if (!is_capture_proxy (val))
177 {
178 tree l = current_lambda_expr ();
179 LAMBDA_EXPR_CAPTURE_OPTIMIZED (l) = true;
180 }
181 return val;
182 }
183 }
184 tree r = mark_rvalue_use (ref, loc, reject_builtin);
185 if (r != ref)
186 expr = convert_from_reference (r);
187 }
188 break;
189
190 case VIEW_CONVERT_EXPR:
191 if (location_wrapper_p (expr))
192 {
193 loc = EXPR_LOCATION (expr);
194 tree op = TREE_OPERAND (expr, 0);
195 tree nop = RECUR (op);
196 if (nop == error_mark_node)
197 return error_mark_node;
198 else if (op == nop)
199 /* No change. */;
200 else if (DECL_P (nop) || CONSTANT_CLASS_P (nop))
201 {
202 /* Reuse the location wrapper. */
203 TREE_OPERAND (expr, 0) = nop;
204 /* If we're replacing a DECL with a constant, we also need to
205 change the TREE_CODE of the location wrapper. */
206 if (rvalue_p)
207 TREE_SET_CODE (expr, NON_LVALUE_EXPR);
208 }
209 else
210 {
211 /* Drop the location wrapper. */
212 expr = nop;
213 protected_set_expr_location (expr, loc);
214 }
215 return expr;
216 }
217 gcc_fallthrough();
218 CASE_CONVERT:
219 recurse_op[0] = true;
220 break;
221
222 case MODIFY_EXPR:
223 {
224 tree lhs = TREE_OPERAND (expr, 0);
225 /* [expr.ass] "An assignment whose left operand is of
226 a volatile-qualified type is deprecated unless the assignment
227 is either a discarded-value expression or appears in an
228 unevaluated context." */
229 if (!cp_unevaluated_operand
230 && (TREE_THIS_VOLATILE (lhs)
231 || CP_TYPE_VOLATILE_P (TREE_TYPE (lhs)))
232 && !TREE_THIS_VOLATILE (expr))
233 {
234 if (warning_at (location_of (expr), OPT_Wvolatile,
235 "using value of assignment with "
236 "%<volatile%>-qualified left operand is "
237 "deprecated"))
238 /* Make sure not to warn about this assignment again. */
239 TREE_THIS_VOLATILE (expr) = true;
240 }
241 break;
242 }
243
244 default:
245 break;
246 }
247
248 for (int i = 0; i < 3; ++i)
249 if (recurse_op[i])
250 {
251 tree op = TREE_OPERAND (expr, i);
252 op = RECUR (op);
253 if (op == error_mark_node)
254 return error_mark_node;
255 TREE_OPERAND (expr, i) = op;
256 }
257
258 return expr;
259 #undef RECUR
260 }
261
262 /* Called whenever the expression EXPR is used in an rvalue context.
263 When REJECT_BUILTIN is true the expression is checked to make sure
264 it doesn't make it possible to obtain the address of a GCC built-in
265 function with no library fallback (or any of its bits, such as in
266 a conversion to bool). */
267
268 tree
mark_rvalue_use(tree e,location_t loc,bool reject_builtin)269 mark_rvalue_use (tree e,
270 location_t loc /* = UNKNOWN_LOCATION */,
271 bool reject_builtin /* = true */)
272 {
273 return mark_use (e, true, true, loc, reject_builtin);
274 }
275
276 /* Called whenever an expression is used in an lvalue context. */
277
278 tree
mark_lvalue_use(tree expr)279 mark_lvalue_use (tree expr)
280 {
281 return mark_use (expr, false, true, input_location, false);
282 }
283
284 /* As above, but don't consider this use a read. */
285
286 tree
mark_lvalue_use_nonread(tree expr)287 mark_lvalue_use_nonread (tree expr)
288 {
289 return mark_use (expr, false, false, input_location, false);
290 }
291
292 /* Called when expr appears as a discarded-value expression. */
293
294 tree
mark_discarded_use(tree expr)295 mark_discarded_use (tree expr)
296 {
297 /* The lvalue-to-rvalue conversion (7.1) is applied if and only if the
298 expression is a glvalue of volatile-qualified type and it is one of the
299 following:
300 * ( expression ), where expression is one of these expressions,
301 * id-expression (8.1.4),
302 * subscripting (8.2.1),
303 * class member access (8.2.5),
304 * indirection (8.3.1),
305 * pointer-to-member operation (8.5),
306 * conditional expression (8.16) where both the second and the third
307 operands are one of these expressions, or
308 * comma expression (8.19) where the right operand is one of these
309 expressions. */
310 if (expr == NULL_TREE)
311 return expr;
312
313 STRIP_ANY_LOCATION_WRAPPER (expr);
314
315 switch (TREE_CODE (expr))
316 {
317 case COND_EXPR:
318 TREE_OPERAND (expr, 2) = mark_discarded_use (TREE_OPERAND (expr, 2));
319 gcc_fallthrough ();
320 case COMPOUND_EXPR:
321 TREE_OPERAND (expr, 1) = mark_discarded_use (TREE_OPERAND (expr, 1));
322 return expr;
323
324 case COMPONENT_REF:
325 case ARRAY_REF:
326 case INDIRECT_REF:
327 case MEMBER_REF:
328 break;
329 default:
330 if (DECL_P (expr))
331 break;
332 else
333 return expr;
334 }
335
336 /* Like mark_rvalue_use, but don't reject built-ins. */
337 return mark_use (expr, true, true, input_location, false);
338 }
339
340 /* Called whenever an expression is used in a type use context. */
341
342 tree
mark_type_use(tree expr)343 mark_type_use (tree expr)
344 {
345 mark_exp_read (expr);
346 return expr;
347 }
348
349 /* Mark EXP as read, not just set, for set but not used -Wunused
350 warning purposes. */
351
352 void
mark_exp_read(tree exp)353 mark_exp_read (tree exp)
354 {
355 if (exp == NULL)
356 return;
357
358 switch (TREE_CODE (exp))
359 {
360 case VAR_DECL:
361 if (DECL_DECOMPOSITION_P (exp))
362 mark_exp_read (DECL_DECOMP_BASE (exp));
363 gcc_fallthrough ();
364 case PARM_DECL:
365 DECL_READ_P (exp) = 1;
366 break;
367 case ARRAY_REF:
368 case COMPONENT_REF:
369 case MODIFY_EXPR:
370 case REALPART_EXPR:
371 case IMAGPART_EXPR:
372 CASE_CONVERT:
373 case ADDR_EXPR:
374 case INDIRECT_REF:
375 case FLOAT_EXPR:
376 case NON_DEPENDENT_EXPR:
377 case VIEW_CONVERT_EXPR:
378 mark_exp_read (TREE_OPERAND (exp, 0));
379 break;
380 case COMPOUND_EXPR:
381 mark_exp_read (TREE_OPERAND (exp, 1));
382 break;
383 case COND_EXPR:
384 if (TREE_OPERAND (exp, 1))
385 mark_exp_read (TREE_OPERAND (exp, 1));
386 if (TREE_OPERAND (exp, 2))
387 mark_exp_read (TREE_OPERAND (exp, 2));
388 break;
389 default:
390 break;
391 }
392 }
393
394 /* Fold X for consideration by one of the warning functions when checking
395 whether an expression has a constant value. */
396
397 tree
fold_for_warn(tree x)398 fold_for_warn (tree x)
399 {
400 /* C++ implementation. */
401
402 /* It's not generally safe to fully fold inside of a template, so
403 call fold_non_dependent_expr instead. */
404 if (processing_template_decl)
405 {
406 tree f = fold_non_dependent_expr (x, tf_none);
407 if (f == error_mark_node)
408 return x;
409 else
410 return f;
411 }
412 else if (cxx_dialect >= cxx11)
413 x = maybe_constant_value (x, NULL_TREE, false, true);
414
415 return c_fully_fold (x, /*for_init*/false, /*maybe_constp*/NULL);
416 }
417