gcc/cp/expr.c

   1 /* Convert language-specific tree expression to rtl instructions,
   2    for GNU compiler.
   3    Copyright (C) 1988-2018 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 || expr == error_mark_node)
 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           expr = process_outer_var_ref (expr, tf_warning_or_error, true);
 143           if (!(TREE_TYPE (oexpr)
 144                 && TREE_CODE (TREE_TYPE (oexpr)) == REFERENCE_TYPE))
 145             expr = convert_from_reference (expr);
 146         }
 147       break;
 148     case COMPONENT_REF:
 149     case NON_DEPENDENT_EXPR:
 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 (TREE_CODE (TREE_TYPE (cap)) != REFERENCE_TYPE
 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     default:
 187       break;
 188     }
 189
 190   for (int i = 0; i < 3; ++i)
 191     if (recurse_op[i])
 192       {
 193         tree op = TREE_OPERAND (expr, i);
 194         op = RECUR (op);
 195         if (op == error_mark_node)
 196           return error_mark_node;
 197         TREE_OPERAND (expr, i) = op;
 198       }
 199
 200   return expr;
 201 #undef RECUR
 202 }
 203
 204 /* Called whenever the expression EXPR is used in an rvalue context.
 205    When REJECT_BUILTIN is true the expression is checked to make sure
 206    it doesn't make it possible to obtain the address of a GCC built-in
 207    function with no library fallback (or any of its bits, such as in
 208    a conversion to bool).  */
 209
 210 tree
 211 mark_rvalue_use (tree e,
 212                  location_t loc /* = UNKNOWN_LOCATION */,
 213                  bool reject_builtin /* = true */)
 214 {
 215   return mark_use (e, true, true, loc, reject_builtin);
 216 }
 217
 218 /* Called whenever an expression is used in an lvalue context.  */
 219
 220 tree
 221 mark_lvalue_use (tree expr)
 222 {
 223   return mark_use (expr, false, true, input_location, false);
 224 }
 225
 226 /* As above, but don't consider this use a read.  */
 227
 228 tree
 229 mark_lvalue_use_nonread (tree expr)
 230 {
 231   return mark_use (expr, false, false, input_location, false);
 232 }
 233
 234 /* Called when expr appears as a discarded-value expression.  */
 235
 236 tree
 237 mark_discarded_use (tree expr)
 238 {
 239   /* The lvalue-to-rvalue conversion (7.1) is applied if and only if the
 240      expression is a glvalue of volatile-qualified type and it is one of the
 241      following:
 242      * ( expression ), where expression is one of these expressions,
 243      * id-expression (8.1.4),
 244      * subscripting (8.2.1),
 245      * class member access (8.2.5),
 246      * indirection (8.3.1),
 247      * pointer-to-member operation (8.5),
 248      * conditional expression (8.16) where both the second and the third
 249        operands are one of these expressions, or
 250      * comma expression (8.19) where the right operand is one of these
 251        expressions.  */
 252   if (expr == NULL_TREE)
 253     return expr;
 254
 255   switch (TREE_CODE (expr))
 256     {
 257     case COND_EXPR:
 258       TREE_OPERAND (expr, 2) = mark_discarded_use (TREE_OPERAND (expr, 2));
 259       gcc_fallthrough ();
 260     case COMPOUND_EXPR:
 261       TREE_OPERAND (expr, 1) = mark_discarded_use (TREE_OPERAND (expr, 1));
 262       return expr;
 263
 264     case COMPONENT_REF:
 265     case ARRAY_REF:
 266     case INDIRECT_REF:
 267     case MEMBER_REF:
 268       break;
 269     default:
 270       if (DECL_P (expr))
 271         break;
 272       else
 273         return expr;
 274     }
 275
 276   /* Like mark_rvalue_use, but don't reject built-ins.  */
 277   return mark_use (expr, true, true, input_location, false);
 278 }
 279
 280 /* Called whenever an expression is used in a type use context.  */
 281
 282 tree
 283 mark_type_use (tree expr)
 284 {
 285   mark_exp_read (expr);
 286   return expr;
 287 }
 288
 289 /* Mark EXP as read, not just set, for set but not used -Wunused
 290    warning purposes.  */
 291
 292 void
 293 mark_exp_read (tree exp)
 294 {
 295   if (exp == NULL)
 296     return;
 297
 298   switch (TREE_CODE (exp))
 299     {
 300     case VAR_DECL:
 301       if (DECL_DECOMPOSITION_P (exp))
 302         mark_exp_read (DECL_DECOMP_BASE (exp));
 303       gcc_fallthrough ();
 304     case PARM_DECL:
 305       DECL_READ_P (exp) = 1;
 306       break;
 307     case ARRAY_REF:
 308     case COMPONENT_REF:
 309     case MODIFY_EXPR:
 310     case REALPART_EXPR:
 311     case IMAGPART_EXPR:
 312     CASE_CONVERT:
 313     case ADDR_EXPR:
 314     case INDIRECT_REF:
 315     case FLOAT_EXPR:
 316     case NON_DEPENDENT_EXPR:
 317     case VIEW_CONVERT_EXPR:
 318       mark_exp_read (TREE_OPERAND (exp, 0));
 319       break;
 320     case COMPOUND_EXPR:
 321       mark_exp_read (TREE_OPERAND (exp, 1));
 322       break;
 323     case COND_EXPR:
 324       if (TREE_OPERAND (exp, 1))
 325         mark_exp_read (TREE_OPERAND (exp, 1));
 326       if (TREE_OPERAND (exp, 2))
 327         mark_exp_read (TREE_OPERAND (exp, 2));
 328       break;
 329     default:
 330       break;
 331     }
 332 }
 333
 334 /* Fold X for consideration by one of the warning functions when checking
 335    whether an expression has a constant value.  */
 336
 337 tree
 338 fold_for_warn (tree x)
 339 {
 340   /* C++ implementation.  */
 341
 342   /* It's not generally safe to fully fold inside of a template, so
 343      call fold_non_dependent_expr instead.  */
 344   if (processing_template_decl)
 345     return fold_non_dependent_expr (x);
 346
 347   return c_fully_fold (x, /*for_init*/false, /*maybe_constp*/NULL);
 348 }