gcc/hash-traits.h

   1 /* Traits for hashable types.
   2    Copyright (C) 2014-2016 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef hash_traits_h
  21 #define hash_traits_h
  22
  23 /* Helpful type for removing with free.  */
  24
  25 template <typename Type>
  26 struct typed_free_remove
  27 {
  28   static inline void remove (Type *p);
  29 };
  30
  31
  32 /* Remove with free.  */
  33
  34 template <typename Type>
  35 inline void
  36 typed_free_remove <Type>::remove (Type *p)
  37 {
  38   free (p);
  39 }
  40
  41 /* Helpful type for removing with delete.  */
  42
  43 template <typename Type>
  44 struct typed_delete_remove
  45 {
  46   static inline void remove (Type *p);
  47 };
  48
  49
  50 /* Remove with delete.  */
  51
  52 template <typename Type>
  53 inline void
  54 typed_delete_remove <Type>::remove (Type *p)
  55 {
  56   delete p;
  57 }
  58
  59 /* Helpful type for a no-op remove.  */
  60
  61 template <typename Type>
  62 struct typed_noop_remove
  63 {
  64   static inline void remove (Type &);
  65 };
  66
  67
  68 /* Remove doing nothing.  */
  69
  70 template <typename Type>
  71 inline void
  72 typed_noop_remove <Type>::remove (Type &)
  73 {
  74 }
  75
  76
  77 /* Hasher for integer type Type in which Empty is a spare value that can be
  78    used to mark empty slots.  If Deleted != Empty then Deleted is another
  79    spare value that can be used for deleted slots; if Deleted == Empty then
  80    hash table entries cannot be deleted.  */
  81
  82 template <typename Type, Type Empty, Type Deleted = Empty>
  83 struct int_hash : typed_noop_remove <Type>
  84 {
  85   typedef Type value_type;
  86   typedef Type compare_type;
  87
  88   static inline hashval_t hash (value_type);
  89   static inline bool equal (value_type existing, value_type candidate);
  90   static inline void mark_deleted (Type &);
  91   static inline void mark_empty (Type &);
  92   static inline bool is_deleted (Type);
  93   static inline bool is_empty (Type);
  94 };
  95
  96 template <typename Type, Type Empty, Type Deleted>
  97 inline hashval_t
  98 int_hash <Type, Empty, Deleted>::hash (value_type x)
  99 {
 100   return x;
 101 }
 102
 103 template <typename Type, Type Empty, Type Deleted>
 104 inline bool
 105 int_hash <Type, Empty, Deleted>::equal (value_type x, value_type y)
 106 {
 107   return x == y;
 108 }
 109
 110 template <typename Type, Type Empty, Type Deleted>
 111 inline void
 112 int_hash <Type, Empty, Deleted>::mark_deleted (Type &x)
 113 {
 114   gcc_assert (Empty != Deleted);
 115   x = Deleted;
 116 }
 117
 118 template <typename Type, Type Empty, Type Deleted>
 119 inline void
 120 int_hash <Type, Empty, Deleted>::mark_empty (Type &x)
 121 {
 122   x = Empty;
 123 }
 124
 125 template <typename Type, Type Empty, Type Deleted>
 126 inline bool
 127 int_hash <Type, Empty, Deleted>::is_deleted (Type x)
 128 {
 129   return Empty != Deleted && x == Deleted;
 130 }
 131
 132 template <typename Type, Type Empty, Type Deleted>
 133 inline bool
 134 int_hash <Type, Empty, Deleted>::is_empty (Type x)
 135 {
 136   return x == Empty;
 137 }
 138
 139 /* Pointer hasher based on pointer equality.  Other types of pointer hash
 140    can inherit this and override the hash and equal functions with some
 141    other form of equality (such as string equality).  */
 142
 143 template <typename Type>
 144 struct pointer_hash
 145 {
 146   typedef Type *value_type;
 147   typedef Type *compare_type;
 148
 149   static inline hashval_t hash (const value_type &);
 150   static inline bool equal (const value_type &existing,
 151                             const compare_type &candidate);
 152   static inline void mark_deleted (Type *&);
 153   static inline void mark_empty (Type *&);
 154   static inline bool is_deleted (Type *);
 155   static inline bool is_empty (Type *);
 156 };
 157
 158 template <typename Type>
 159 inline hashval_t
 160 pointer_hash <Type>::hash (const value_type &candidate)
 161 {
 162   /* This is a really poor hash function, but it is what the current code uses,
 163      so I am reusing it to avoid an additional axis in testing.  */
 164   return (hashval_t) ((intptr_t)candidate >> 3);
 165 }
 166
 167 template <typename Type>
 168 inline bool
 169 pointer_hash <Type>::equal (const value_type &existing,
 170                            const compare_type &candidate)
 171 {
 172   return existing == candidate;
 173 }
 174
 175 template <typename Type>
 176 inline void
 177 pointer_hash <Type>::mark_deleted (Type *&e)
 178 {
 179   e = reinterpret_cast<Type *> (1);
 180 }
 181
 182 template <typename Type>
 183 inline void
 184 pointer_hash <Type>::mark_empty (Type *&e)
 185 {
 186   e = NULL;
 187 }
 188
 189 template <typename Type>
 190 inline bool
 191 pointer_hash <Type>::is_deleted (Type *e)
 192 {
 193   return e == reinterpret_cast<Type *> (1);
 194 }
 195
 196 template <typename Type>
 197 inline bool
 198 pointer_hash <Type>::is_empty (Type *e)
 199 {
 200   return e == NULL;
 201 }
 202
 203 /* Hasher for "const char *" strings, using string rather than pointer
 204    equality.  */
 205
 206 struct string_hash : pointer_hash <const char>
 207 {
 208   static inline hashval_t hash (const char *);
 209   static inline bool equal (const char *, const char *);
 210 };
 211
 212 inline hashval_t
 213 string_hash::hash (const char *id)
 214 {
 215   return htab_hash_string (id);
 216 }
 217
 218 inline bool
 219 string_hash::equal (const char *id1, const char *id2)
 220 {
 221   return strcmp (id1, id2) == 0;
 222 }
 223
 224 /* Remover and marker for entries in gc memory.  */
 225
 226 template<typename T>
 227 struct ggc_remove
 228 {
 229   static void remove (T &) {}
 230
 231   static void
 232   ggc_mx (T &p)
 233   {
 234     extern void gt_ggc_mx (T &);
 235     gt_ggc_mx (p);
 236   }
 237
 238   static void
 239   pch_nx (T &p)
 240   {
 241     extern void gt_pch_nx (T &);
 242     gt_pch_nx (p);
 243   }
 244
 245   static void
 246   pch_nx (T &p, gt_pointer_operator op, void *cookie)
 247   {
 248     op (&p, cookie);
 249   }
 250 };
 251
 252 /* Remover and marker for "cache" entries in gc memory.  These entries can
 253    be deleted if there are no non-cache references to the data.  */
 254
 255 template<typename T>
 256 struct ggc_cache_remove : ggc_remove<T>
 257 {
 258   /* Entries are weakly held because this is for caches.  */
 259   static void ggc_mx (T &) {}
 260
 261   static int
 262   keep_cache_entry (T &e)
 263   {
 264     return ggc_marked_p (e) ? -1 : 0;
 265   }
 266 };
 267
 268 /* Traits for pointer elements that should not be freed when an element
 269    is deleted.  */
 270
 271 template <typename T>
 272 struct nofree_ptr_hash : pointer_hash <T>, typed_noop_remove <T *> {};
 273
 274 /* Traits for pointer elements that should be freed via free() when an
 275    element is deleted.  */
 276
 277 template <typename T>
 278 struct free_ptr_hash : pointer_hash <T>, typed_free_remove <T> {};
 279
 280 /* Traits for pointer elements that should be freed via delete operand when an
 281    element is deleted.  */
 282
 283 template <typename T>
 284 struct delete_ptr_hash : pointer_hash <T>, typed_delete_remove <T> {};
 285
 286 /* Traits for elements that point to gc memory.  The pointed-to data
 287    must be kept across collections.  */
 288
 289 template <typename T>
 290 struct ggc_ptr_hash : pointer_hash <T>, ggc_remove <T *> {};
 291
 292 /* Traits for elements that point to gc memory.  The elements don't
 293    in themselves keep the pointed-to data alive and they can be deleted
 294    if the pointed-to data is going to be collected.  */
 295
 296 template <typename T>
 297 struct ggc_cache_ptr_hash : pointer_hash <T>, ggc_cache_remove <T *> {};
 298
 299 /* Traits for string elements that should not be freed when an element
 300    is deleted.  */
 301
 302 struct nofree_string_hash : string_hash, typed_noop_remove <const char *> {};
 303
 304 template <typename T> struct default_hash_traits : T {};
 305
 306 template <typename T>
 307 struct default_hash_traits <T *> : ggc_ptr_hash <T> {};
 308
 309 #endif