libgomp/hashtab.h

   1 /* An expandable hash tables datatype.
   2    Copyright (C) 1999-2020 Free Software Foundation, Inc.
   3    Contributed by Vladimir Makarov <vmakarov@cygnus.com>.
   4
   5    This file is part of the GNU Offloading and Multi Processing Library
   6    (libgomp).
   7
   8    Libgomp is free software; you can redistribute it and/or modify it
   9    under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3, or (at your option)
  11    any later version.
  12
  13    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
  14    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  15    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  16    more details.
  17
  18    Under Section 7 of GPL version 3, you are granted additional
  19    permissions described in the GCC Runtime Library Exception, version
  20    3.1, as published by the Free Software Foundation.
  21
  22    You should have received a copy of the GNU General Public License and
  23    a copy of the GCC Runtime Library Exception along with this program;
  24    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25    <http://www.gnu.org/licenses/>.  */
  26
  27 /* The hash table code copied from include/hashtab.[hc] and adjusted,
  28    so that the hash table entries are in the flexible array at the end
  29    of the control structure, no callbacks are used and the elements in the
  30    table are of the hash_entry_type type.
  31    Before including this file, define hash_entry_type type and
  32    htab_alloc and htab_free functions.  After including it, define
  33    htab_hash and htab_eq inline functions.   */
  34
  35 /* This package implements basic hash table functionality.  It is possible
  36    to search for an entry, create an entry and destroy an entry.
  37
  38    Elements in the table are generic pointers.
  39
  40    The size of the table is not fixed; if the occupancy of the table
  41    grows too high the hash table will be expanded.
  42
  43    The abstract data implementation is based on generalized Algorithm D
  44    from Knuth's book "The art of computer programming".  Hash table is
  45    expanded by creation of new hash table and transferring elements from
  46    the old table to the new table.  */
  47
  48 /* The type for a hash code.  */
  49 typedef unsigned int hashval_t;
  50
  51 static inline hashval_t htab_hash (hash_entry_type);
  52 static inline bool htab_eq (hash_entry_type, hash_entry_type);
  53
  54 /* This macro defines reserved value for empty table entry.  */
  55
  56 #define HTAB_EMPTY_ENTRY    ((hash_entry_type) 0)
  57
  58 /* This macro defines reserved value for table entry which contained
  59    a deleted element. */
  60
  61 #define HTAB_DELETED_ENTRY  ((hash_entry_type) 1)
  62
  63 /* Hash tables are of the following type.  The structure
  64    (implementation) of this type is not needed for using the hash
  65    tables.  All work with hash table should be executed only through
  66    functions mentioned below.  The size of this structure is subject to
  67    change.  */
  68
  69 struct htab {
  70   /* Current size (in entries) of the hash table.  */
  71   size_t size;
  72
  73   /* Current number of elements including also deleted elements.  */
  74   size_t n_elements;
  75
  76   /* Current number of deleted elements in the table.  */
  77   size_t n_deleted;
  78
  79   /* Current size (in entries) of the hash table, as an index into the
  80      table of primes.  */
  81   unsigned int size_prime_index;
  82
  83   /* Table itself.  */
  84   hash_entry_type entries[];
  85 };
  86
  87 typedef struct htab *htab_t;
  88
  89 /* An enum saying whether we insert into the hash table or not.  */
  90 enum insert_option {NO_INSERT, INSERT};
  91
  92 /* Table of primes and multiplicative inverses.
  93
  94    Note that these are not minimally reduced inverses.  Unlike when generating
  95    code to divide by a constant, we want to be able to use the same algorithm
  96    all the time.  All of these inverses (are implied to) have bit 32 set.
  97
  98    For the record, the function that computed the table is in
  99    libiberty/hashtab.c.  */
 100
 101 struct prime_ent
 102 {
 103   hashval_t prime;
 104   hashval_t inv;
 105   hashval_t inv_m2;     /* inverse of prime-2 */
 106   hashval_t shift;
 107 };
 108
 109 static struct prime_ent const prime_tab[] = {
 110   {          7, 0x24924925, 0x9999999b, 2 },
 111   {         13, 0x3b13b13c, 0x745d1747, 3 },
 112   {         31, 0x08421085, 0x1a7b9612, 4 },
 113   {         61, 0x0c9714fc, 0x15b1e5f8, 5 },
 114   {        127, 0x02040811, 0x0624dd30, 6 },
 115   {        251, 0x05197f7e, 0x073260a5, 7 },
 116   {        509, 0x01824366, 0x02864fc8, 8 },
 117   {       1021, 0x00c0906d, 0x014191f7, 9 },
 118   {       2039, 0x0121456f, 0x0161e69e, 10 },
 119   {       4093, 0x00300902, 0x00501908, 11 },
 120   {       8191, 0x00080041, 0x00180241, 12 },
 121   {      16381, 0x000c0091, 0x00140191, 13 },
 122   {      32749, 0x002605a5, 0x002a06e6, 14 },
 123   {      65521, 0x000f00e2, 0x00110122, 15 },
 124   {     131071, 0x00008001, 0x00018003, 16 },
 125   {     262139, 0x00014002, 0x0001c004, 17 },
 126   {     524287, 0x00002001, 0x00006001, 18 },
 127   {    1048573, 0x00003001, 0x00005001, 19 },
 128   {    2097143, 0x00004801, 0x00005801, 20 },
 129   {    4194301, 0x00000c01, 0x00001401, 21 },
 130   {    8388593, 0x00001e01, 0x00002201, 22 },
 131   {   16777213, 0x00000301, 0x00000501, 23 },
 132   {   33554393, 0x00001381, 0x00001481, 24 },
 133   {   67108859, 0x00000141, 0x000001c1, 25 },
 134   {  134217689, 0x000004e1, 0x00000521, 26 },
 135   {  268435399, 0x00000391, 0x000003b1, 27 },
 136   {  536870909, 0x00000019, 0x00000029, 28 },
 137   { 1073741789, 0x0000008d, 0x00000095, 29 },
 138   { 2147483647, 0x00000003, 0x00000007, 30 },
 139   /* Avoid "decimal constant so large it is unsigned" for 4294967291.  */
 140   { 0xfffffffb, 0x00000006, 0x00000008, 31 }
 141 };
 142
 143 /* The following function returns an index into the above table of the
 144    nearest prime number which is greater than N, and near a power of two. */
 145
 146 static unsigned int
 147 higher_prime_index (unsigned long n)
 148 {
 149   unsigned int low = 0;
 150   unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]);
 151
 152   while (low != high)
 153     {
 154       unsigned int mid = low + (high - low) / 2;
 155       if (n > prime_tab[mid].prime)
 156         low = mid + 1;
 157       else
 158         high = mid;
 159     }
 160
 161   /* If we've run out of primes, abort.  */
 162   if (n > prime_tab[low].prime)
 163     abort ();
 164
 165   return low;
 166 }
 167
 168 /* Return the current size of given hash table.  */
 169
 170 static inline size_t
 171 htab_size (htab_t htab)
 172 {
 173   return htab->size;
 174 }
 175
 176 /* Return the current number of elements in given hash table. */
 177
 178 static inline size_t
 179 htab_elements (htab_t htab)
 180 {
 181   return htab->n_elements - htab->n_deleted;
 182 }
 183
 184 /* Return X % Y.  */
 185
 186 static inline hashval_t
 187 htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift)
 188 {
 189   /* The multiplicative inverses computed above are for 32-bit types, and
 190      requires that we be able to compute a highpart multiply.  */
 191   if (sizeof (hashval_t) * __CHAR_BIT__ <= 32)
 192     {
 193       hashval_t t1, t2, t3, t4, q, r;
 194
 195       t1 = ((unsigned long long)x * inv) >> 32;
 196       t2 = x - t1;
 197       t3 = t2 >> 1;
 198       t4 = t1 + t3;
 199       q  = t4 >> shift;
 200       r  = x - (q * y);
 201
 202       return r;
 203     }
 204
 205   /* Otherwise just use the native division routines.  */
 206   return x % y;
 207 }
 208
 209 /* Compute the primary hash for HASH given HTAB's current size.  */
 210
 211 static inline hashval_t
 212 htab_mod (hashval_t hash, htab_t htab)
 213 {
 214   const struct prime_ent *p = &prime_tab[htab->size_prime_index];
 215   return htab_mod_1 (hash, p->prime, p->inv, p->shift);
 216 }
 217
 218 /* Compute the secondary hash for HASH given HTAB's current size.  */
 219
 220 static inline hashval_t
 221 htab_mod_m2 (hashval_t hash, htab_t htab)
 222 {
 223   const struct prime_ent *p = &prime_tab[htab->size_prime_index];
 224   return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift);
 225 }
 226
 227 /* Create hash table of size SIZE.  */
 228
 229 static htab_t
 230 htab_create (size_t size)
 231 {
 232   htab_t result;
 233   unsigned int size_prime_index;
 234
 235   size_prime_index = higher_prime_index (size);
 236   size = prime_tab[size_prime_index].prime;
 237
 238   result = (htab_t) htab_alloc (sizeof (struct htab)
 239                                 + size * sizeof (hash_entry_type));
 240   result->size = size;
 241   result->n_elements = 0;
 242   result->n_deleted = 0;
 243   result->size_prime_index = size_prime_index;
 244   memset (result->entries, 0, size * sizeof (hash_entry_type));
 245   return result;
 246 }
 247
 248 /* Similar to htab_find_slot, but without several unwanted side effects:
 249     - Does not call htab_eq when it finds an existing entry.
 250     - Does not change the count of elements in the hash table.
 251    This function also assumes there are no deleted entries in the table.
 252    HASH is the hash value for the element to be inserted.  */
 253
 254 static hash_entry_type *
 255 find_empty_slot_for_expand (htab_t htab, hashval_t hash)
 256 {
 257   hashval_t index = htab_mod (hash, htab);
 258   size_t size = htab_size (htab);
 259   hash_entry_type *slot = htab->entries + index;
 260   hashval_t hash2;
 261
 262   if (*slot == HTAB_EMPTY_ENTRY)
 263     return slot;
 264   else if (*slot == HTAB_DELETED_ENTRY)
 265     abort ();
 266
 267   hash2 = htab_mod_m2 (hash, htab);
 268   for (;;)
 269     {
 270       index += hash2;
 271       if (index >= size)
 272         index -= size;
 273
 274       slot = htab->entries + index;
 275       if (*slot == HTAB_EMPTY_ENTRY)
 276         return slot;
 277       else if (*slot == HTAB_DELETED_ENTRY)
 278         abort ();
 279     }
 280 }
 281
 282 /* The following function changes size of memory allocated for the
 283    entries and repeatedly inserts the table elements.  The occupancy
 284    of the table after the call will be about 50%.  Naturally the hash
 285    table must already exist.  Remember also that the place of the
 286    table entries is changed.  */
 287
 288 static htab_t
 289 htab_expand (htab_t htab)
 290 {
 291   htab_t nhtab;
 292   hash_entry_type *olimit;
 293   hash_entry_type *p;
 294   size_t osize, elts;
 295
 296   osize = htab->size;
 297   olimit = htab->entries + osize;
 298   elts = htab_elements (htab);
 299
 300   /* Resize only when table after removal of unused elements is either
 301      too full or too empty.  */
 302   if (elts * 2 > osize || (elts * 8 < osize && osize > 32))
 303     nhtab = htab_create (elts * 2);
 304   else
 305     nhtab = htab_create (osize - 1);
 306   nhtab->n_elements = htab->n_elements - htab->n_deleted;
 307
 308   p = htab->entries;
 309   do
 310     {
 311       hash_entry_type x = *p;
 312
 313       if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
 314         *find_empty_slot_for_expand (nhtab, htab_hash (x)) = x;
 315
 316       p++;
 317     }
 318   while (p < olimit);
 319
 320   htab_free (htab);
 321   return nhtab;
 322 }
 323
 324 /* This function searches for a hash table entry equal to the given
 325    element.  It cannot be used to insert or delete an element.  */
 326
 327 static hash_entry_type
 328 htab_find (htab_t htab, const hash_entry_type element)
 329 {
 330   hashval_t index, hash2, hash = htab_hash (element);
 331   size_t size;
 332   hash_entry_type entry;
 333
 334   size = htab_size (htab);
 335   index = htab_mod (hash, htab);
 336
 337   entry = htab->entries[index];
 338   if (entry == HTAB_EMPTY_ENTRY
 339       || (entry != HTAB_DELETED_ENTRY && htab_eq (entry, element)))
 340     return entry;
 341
 342   hash2 = htab_mod_m2 (hash, htab);
 343   for (;;)
 344     {
 345       index += hash2;
 346       if (index >= size)
 347         index -= size;
 348
 349       entry = htab->entries[index];
 350       if (entry == HTAB_EMPTY_ENTRY
 351           || (entry != HTAB_DELETED_ENTRY && htab_eq (entry, element)))
 352         return entry;
 353     }
 354 }
 355
 356 /* This function searches for a hash table slot containing an entry
 357    equal to the given element.  To delete an entry, call this with
 358    insert=NO_INSERT, then call htab_clear_slot on the slot returned
 359    (possibly after doing some checks).  To insert an entry, call this
 360    with insert=INSERT, then write the value you want into the returned
 361    slot.  */
 362
 363 static hash_entry_type *
 364 htab_find_slot (htab_t *htabp, const hash_entry_type element,
 365                 enum insert_option insert)
 366 {
 367   hash_entry_type *first_deleted_slot;
 368   hashval_t index, hash2, hash = htab_hash (element);
 369   size_t size;
 370   hash_entry_type entry;
 371   htab_t htab = *htabp;
 372
 373   size = htab_size (htab);
 374   if (insert == INSERT && size * 3 <= htab->n_elements * 4)
 375     {
 376       htab = *htabp = htab_expand (htab);
 377       size = htab_size (htab);
 378     }
 379
 380   index = htab_mod (hash, htab);
 381
 382   first_deleted_slot = NULL;
 383
 384   entry = htab->entries[index];
 385   if (entry == HTAB_EMPTY_ENTRY)
 386     goto empty_entry;
 387   else if (entry == HTAB_DELETED_ENTRY)
 388     first_deleted_slot = &htab->entries[index];
 389   else if (htab_eq (entry, element))
 390     return &htab->entries[index];
 391
 392   hash2 = htab_mod_m2 (hash, htab);
 393   for (;;)
 394     {
 395       index += hash2;
 396       if (index >= size)
 397         index -= size;
 398
 399       entry = htab->entries[index];
 400       if (entry == HTAB_EMPTY_ENTRY)
 401         goto empty_entry;
 402       else if (entry == HTAB_DELETED_ENTRY)
 403         {
 404           if (!first_deleted_slot)
 405             first_deleted_slot = &htab->entries[index];
 406         }
 407       else if (htab_eq (entry, element))
 408         return &htab->entries[index];
 409     }
 410
 411  empty_entry:
 412   if (insert == NO_INSERT)
 413     return NULL;
 414
 415   if (first_deleted_slot)
 416     {
 417       htab->n_deleted--;
 418       *first_deleted_slot = HTAB_EMPTY_ENTRY;
 419       return first_deleted_slot;
 420     }
 421
 422   htab->n_elements++;
 423   return &htab->entries[index];
 424 }
 425
 426 /* This function clears a specified slot in a hash table.  It is
 427    useful when you've already done the lookup and don't want to do it
 428    again.  */
 429
 430 static inline void
 431 htab_clear_slot (htab_t htab, hash_entry_type *slot)
 432 {
 433   if (slot < htab->entries || slot >= htab->entries + htab_size (htab)
 434       || *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY)
 435     abort ();
 436
 437   *slot = HTAB_DELETED_ENTRY;
 438   htab->n_deleted++;
 439 }
 440
 441 /* Returns a hash code for pointer P. Simplified version of evahash */
 442
 443 static inline hashval_t
 444 hash_pointer (const void *p)
 445 {
 446   uintptr_t v = (uintptr_t) p;
 447   if (sizeof (v) > sizeof (hashval_t))
 448     v ^= v >> (sizeof (uintptr_t) / 2 * __CHAR_BIT__);
 449   return v;
 450 }