gcc/cp/expr.cc

   1 /* Convert language-specific tree expression to rtl instructions,
   2    for GNU compiler.
   3    Copyright (C) 1988-2023 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
  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
  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] "An 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 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
 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
 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
 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
 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
 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
 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
 396 fold_for_warn (tree x)
 397 {
 398   /* C++ implementation.  */
 399
 400   if (cp_unevaluated_operand)
 401     /* In an unevaluated context we don't care about the reduced value
 402        of an expression, so neither should any warnings.  */
 403     return x;
 404
 405   /* Prevent warning-dependent constexpr evaluation from changing
 406      DECL_UID (which breaks -fcompare-debug) and from instantiating
 407      templates.  */
 408   uid_sensitive_constexpr_evaluation_sentinel s;
 409
 410   /* It's not generally safe to fully fold inside of a template, so
 411      call fold_non_dependent_expr instead.  */
 412   if (processing_template_decl)
 413     {
 414       tree f = fold_non_dependent_expr (x, tf_none);
 415       if (f == error_mark_node)
 416         return x;
 417       else
 418         return f;
 419     }
 420   else if (cxx_dialect >= cxx11)
 421     x = maybe_constant_value (x);
 422
 423   return c_fully_fold (x, /*for_init*/false, /*maybe_constp*/NULL);
 424 }