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 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 (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             return RECUR (cap);
 121         }
 122       if (outer_automatic_var_p (expr)
 123           && decl_constant_var_p (expr))
 124         {
 125           if (rvalue_p)
 126             {
 127               tree t = maybe_constant_value (expr);
 128               if (TREE_CONSTANT (t))
 129                 {
 130                   expr = t;
 131                   break;
 132                 }
 133             }
 134           expr = process_outer_var_ref (expr, tf_warning_or_error, true);
 135           if (!(TREE_TYPE (oexpr)
 136                 && TREE_CODE (TREE_TYPE (oexpr)) == REFERENCE_TYPE))
 137             expr = convert_from_reference (expr);
 138         }
 139       break;
 140     case COMPONENT_REF:
 141     case NON_DEPENDENT_EXPR:
 142       recurse_op[0] = true;
 143       break;
 144     case COMPOUND_EXPR:
 145       recurse_op[1] = true;
 146       break;
 147     case COND_EXPR:
 148       recurse_op[2] = true;
 149       if (TREE_OPERAND (expr, 1))
 150         recurse_op[1] = true;
 151       break;
 152     case INDIRECT_REF:
 153       if (REFERENCE_REF_P (expr))
 154         {
 155           /* Try to look through the reference.  */
 156           tree ref = TREE_OPERAND (expr, 0);
 157           if (rvalue_p && is_normal_capture_proxy (ref))
 158             {
 159               /* Look through capture by reference.  */
 160               tree cap = DECL_CAPTURED_VARIABLE (ref);
 161               if (TREE_CODE (TREE_TYPE (cap)) != REFERENCE_TYPE
 162                   && decl_constant_var_p (cap))
 163                 return RECUR (cap);
 164             }
 165           tree r = mark_rvalue_use (ref, loc, reject_builtin);
 166           if (r != ref)
 167             expr = convert_from_reference (r);
 168         }
 169       break;
 170     default:
 171       break;
 172     }
 173
 174   for (int i = 0; i < 3; ++i)
 175     if (recurse_op[i])
 176       {
 177         tree op = TREE_OPERAND (expr, i);
 178         op = RECUR (op);
 179         if (op == error_mark_node)
 180           return error_mark_node;
 181         TREE_OPERAND (expr, i) = op;
 182       }
 183
 184   return expr;
 185 #undef RECUR
 186 }
 187
 188 /* Called whenever the expression EXPR is used in an rvalue context.
 189    When REJECT_BUILTIN is true the expression is checked to make sure
 190    it doesn't make it possible to obtain the address of a GCC built-in
 191    function with no library fallback (or any of its bits, such as in
 192    a conversion to bool).  */
 193
 194 tree
 195 mark_rvalue_use (tree e,
 196                  location_t loc /* = UNKNOWN_LOCATION */,
 197                  bool reject_builtin /* = true */)
 198 {
 199   return mark_use (e, true, true, loc, reject_builtin);
 200 }
 201
 202 /* Called whenever an expression is used in an lvalue context.  */
 203
 204 tree
 205 mark_lvalue_use (tree expr)
 206 {
 207   return mark_use (expr, false, true, input_location, false);
 208 }
 209
 210 /* As above, but don't consider this use a read.  */
 211
 212 tree
 213 mark_lvalue_use_nonread (tree expr)
 214 {
 215   return mark_use (expr, false, false, input_location, false);
 216 }
 217
 218 /* Called when expr appears as a discarded-value expression.  */
 219
 220 tree
 221 mark_discarded_use (tree expr)
 222 {
 223   /* The lvalue-to-rvalue conversion (7.1) is applied if and only if the
 224      expression is a glvalue of volatile-qualified type and it is one of the
 225      following:
 226      * ( expression ), where expression is one of these expressions,
 227      * id-expression (8.1.4),
 228      * subscripting (8.2.1),
 229      * class member access (8.2.5),
 230      * indirection (8.3.1),
 231      * pointer-to-member operation (8.5),
 232      * conditional expression (8.16) where both the second and the third
 233        operands are one of these expressions, or
 234      * comma expression (8.19) where the right operand is one of these
 235        expressions.  */
 236   if (expr == NULL_TREE)
 237     return expr;
 238
 239   switch (TREE_CODE (expr))
 240     {
 241     case COND_EXPR:
 242       TREE_OPERAND (expr, 2) = mark_discarded_use (TREE_OPERAND (expr, 2));
 243       gcc_fallthrough ();
 244     case COMPOUND_EXPR:
 245       TREE_OPERAND (expr, 1) = mark_discarded_use (TREE_OPERAND (expr, 1));
 246       return expr;
 247
 248     case COMPONENT_REF:
 249     case ARRAY_REF:
 250     case INDIRECT_REF:
 251     case MEMBER_REF:
 252       break;
 253     default:
 254       if (DECL_P (expr))
 255         break;
 256       else
 257         return expr;
 258     }
 259
 260   /* Like mark_rvalue_use, but don't reject built-ins.  */
 261   return mark_use (expr, true, true, input_location, false);
 262 }
 263
 264 /* Called whenever an expression is used in a type use context.  */
 265
 266 tree
 267 mark_type_use (tree expr)
 268 {
 269   mark_exp_read (expr);
 270   return expr;
 271 }
 272
 273 /* Mark EXP as read, not just set, for set but not used -Wunused
 274    warning purposes.  */
 275
 276 void
 277 mark_exp_read (tree exp)
 278 {
 279   if (exp == NULL)
 280     return;
 281
 282   switch (TREE_CODE (exp))
 283     {
 284     case VAR_DECL:
 285       if (DECL_DECOMPOSITION_P (exp))
 286         mark_exp_read (DECL_DECOMP_BASE (exp));
 287       gcc_fallthrough ();
 288     case PARM_DECL:
 289       DECL_READ_P (exp) = 1;
 290       break;
 291     case ARRAY_REF:
 292     case COMPONENT_REF:
 293     case MODIFY_EXPR:
 294     case REALPART_EXPR:
 295     case IMAGPART_EXPR:
 296     CASE_CONVERT:
 297     case ADDR_EXPR:
 298     case INDIRECT_REF:
 299     case FLOAT_EXPR:
 300     case NON_DEPENDENT_EXPR:
 301     case VIEW_CONVERT_EXPR:
 302       mark_exp_read (TREE_OPERAND (exp, 0));
 303       break;
 304     case COMPOUND_EXPR:
 305       mark_exp_read (TREE_OPERAND (exp, 1));
 306       break;
 307     case COND_EXPR:
 308       if (TREE_OPERAND (exp, 1))
 309         mark_exp_read (TREE_OPERAND (exp, 1));
 310       if (TREE_OPERAND (exp, 2))
 311         mark_exp_read (TREE_OPERAND (exp, 2));
 312       break;
 313     default:
 314       break;
 315     }
 316 }
 317