gcc/cp/expr.c

   1 /* Convert language-specific tree expression to rtl instructions,
   2    for GNU compiler.
   3    Copyright (C) 1988-2017 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 static 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 (outer_automatic_var_p (expr)
 115           && decl_constant_var_p (expr))
 116         {
 117           if (rvalue_p)
 118             {
 119               tree t = maybe_constant_value (expr);
 120               if (TREE_CONSTANT (t))
 121                 {
 122                   expr = t;
 123                   break;
 124                 }
 125             }
 126           expr = process_outer_var_ref (expr, tf_warning_or_error, true);
 127           if (!(TREE_TYPE (oexpr)
 128                 && TREE_CODE (TREE_TYPE (oexpr)) == REFERENCE_TYPE))
 129             expr = convert_from_reference (expr);
 130         }
 131       break;
 132     case COMPONENT_REF:
 133     case NON_DEPENDENT_EXPR:
 134       recurse_op[0] = true;
 135       break;
 136     case COMPOUND_EXPR:
 137       recurse_op[1] = true;
 138       break;
 139     case COND_EXPR:
 140       recurse_op[2] = true;
 141       if (TREE_OPERAND (expr, 1))
 142         recurse_op[1] = true;
 143       break;
 144     case INDIRECT_REF:
 145       if (REFERENCE_REF_P (expr))
 146         {
 147           /* Try to look through the reference.  */
 148           tree ref = TREE_OPERAND (expr, 0);
 149           tree r = mark_rvalue_use (ref, loc, reject_builtin);
 150           if (r != ref)
 151             expr = convert_from_reference (r);
 152         }
 153       break;
 154     default:
 155       break;
 156     }
 157
 158   for (int i = 0; i < 3; ++i)
 159     if (recurse_op[i])
 160       {
 161         tree op = TREE_OPERAND (expr, i);
 162         op = RECUR (op);
 163         if (op == error_mark_node)
 164           return error_mark_node;
 165         TREE_OPERAND (expr, i) = op;
 166       }
 167
 168   return expr;
 169 #undef RECUR
 170 }
 171
 172 /* Called whenever the expression EXPR is used in an rvalue context.
 173    When REJECT_BUILTIN is true the expression is checked to make sure
 174    it doesn't make it possible to obtain the address of a GCC built-in
 175    function with no library fallback (or any of its bits, such as in
 176    a conversion to bool).  */
 177
 178 tree
 179 mark_rvalue_use (tree e,
 180                  location_t loc /* = UNKNOWN_LOCATION */,
 181                  bool reject_builtin /* = true */)
 182 {
 183   return mark_use (e, true, true, loc, reject_builtin);
 184 }
 185
 186 /* Called when expr appears as a discarded-value expression.  */
 187
 188 tree
 189 mark_discarded_use (tree expr)
 190 {
 191   /* The lvalue-to-rvalue conversion (7.1) is applied if and only if the
 192      expression is a glvalue of volatile-qualified type and it is one of the
 193      following:
 194      * ( expression ), where expression is one of these expressions,
 195      * id-expression (8.1.4),
 196      * subscripting (8.2.1),
 197      * class member access (8.2.5),
 198      * indirection (8.3.1),
 199      * pointer-to-member operation (8.5),
 200      * conditional expression (8.16) where both the second and the third
 201        operands are one of these expressions, or
 202      * comma expression (8.19) where the right operand is one of these
 203        expressions.  */
 204   if (expr == NULL_TREE)
 205     return expr;
 206
 207   switch (TREE_CODE (expr))
 208     {
 209     case COND_EXPR:
 210       TREE_OPERAND (expr, 2) = mark_discarded_use (TREE_OPERAND (expr, 2));
 211       gcc_fallthrough ();
 212     case COMPOUND_EXPR:
 213       TREE_OPERAND (expr, 1) = mark_discarded_use (TREE_OPERAND (expr, 1));
 214       return expr;
 215
 216     case COMPONENT_REF:
 217     case ARRAY_REF:
 218     case INDIRECT_REF:
 219     case MEMBER_REF:
 220       break;
 221     default:
 222       if (DECL_P (expr))
 223         break;
 224       else
 225         return expr;
 226     }
 227
 228   /* Like mark_rvalue_use, but don't reject built-ins.  */
 229   return mark_use (expr, true, true, input_location, false);
 230 }
 231
 232 /* Called whenever an expression is used in an lvalue context.  */
 233
 234 tree
 235 mark_lvalue_use (tree expr)
 236 {
 237   return mark_use (expr, false, true, input_location, false);
 238 }
 239
 240 /* As above, but don't consider this use a read.  */
 241
 242 tree
 243 mark_lvalue_use_nonread (tree expr)
 244 {
 245   return mark_use (expr, false, false, input_location, false);
 246 }
 247
 248 /* Called whenever an expression is used in a type use context.  */
 249
 250 tree
 251 mark_type_use (tree expr)
 252 {
 253   mark_exp_read (expr);
 254   return expr;
 255 }
 256
 257 /* Mark EXP as read, not just set, for set but not used -Wunused
 258    warning purposes.  */
 259
 260 void
 261 mark_exp_read (tree exp)
 262 {
 263   if (exp == NULL)
 264     return;
 265
 266   switch (TREE_CODE (exp))
 267     {
 268     case VAR_DECL:
 269       if (DECL_DECOMPOSITION_P (exp))
 270         mark_exp_read (DECL_DECOMP_BASE (exp));
 271       gcc_fallthrough ();
 272     case PARM_DECL:
 273       DECL_READ_P (exp) = 1;
 274       break;
 275     case ARRAY_REF:
 276     case COMPONENT_REF:
 277     case MODIFY_EXPR:
 278     case REALPART_EXPR:
 279     case IMAGPART_EXPR:
 280     CASE_CONVERT:
 281     case ADDR_EXPR:
 282     case INDIRECT_REF:
 283     case FLOAT_EXPR:
 284     case NON_DEPENDENT_EXPR:
 285     case VIEW_CONVERT_EXPR:
 286       mark_exp_read (TREE_OPERAND (exp, 0));
 287       break;
 288     case COMPOUND_EXPR:
 289       mark_exp_read (TREE_OPERAND (exp, 1));
 290       break;
 291     case COND_EXPR:
 292       if (TREE_OPERAND (exp, 1))
 293         mark_exp_read (TREE_OPERAND (exp, 1));
 294       if (TREE_OPERAND (exp, 2))
 295         mark_exp_read (TREE_OPERAND (exp, 2));
 296       break;
 297     default:
 298       break;
 299     }
 300 }
 301