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[official-gcc.git] / libgomp / hashtab.h
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1 /* An expandable hash tables datatype.
2 Copyright (C) 1999-2017 Free Software Foundation, Inc.
3 Contributed by Vladimir Makarov <vmakarov@cygnus.com>.
5 This file is part of the GNU Offloading and Multi Processing Library
6 (libgomp).
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.
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.
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.
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/>. */
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. */
35 /* This package implements basic hash table functionality. It is possible
36 to search for an entry, create an entry and destroy an entry.
38 Elements in the table are generic pointers.
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.
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. */
48 /* The type for a hash code. */
49 typedef unsigned int hashval_t;
51 static inline hashval_t htab_hash (hash_entry_type);
52 static inline bool htab_eq (hash_entry_type, hash_entry_type);
54 /* This macro defines reserved value for empty table entry. */
56 #define HTAB_EMPTY_ENTRY ((hash_entry_type) 0)
58 /* This macro defines reserved value for table entry which contained
59 a deleted element. */
61 #define HTAB_DELETED_ENTRY ((hash_entry_type) 1)
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. */
69 struct htab {
70 /* Current size (in entries) of the hash table. */
71 size_t size;
73 /* Current number of elements including also deleted elements. */
74 size_t n_elements;
76 /* Current number of deleted elements in the table. */
77 size_t n_deleted;
79 /* Current size (in entries) of the hash table, as an index into the
80 table of primes. */
81 unsigned int size_prime_index;
83 /* Table itself. */
84 hash_entry_type entries[];
87 typedef struct htab *htab_t;
89 /* An enum saying whether we insert into the hash table or not. */
90 enum insert_option {NO_INSERT, INSERT};
92 /* Table of primes and multiplicative inverses.
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.
98 For the record, the function that computed the table is in
99 libiberty/hashtab.c. */
101 struct prime_ent
103 hashval_t prime;
104 hashval_t inv;
105 hashval_t inv_m2; /* inverse of prime-2 */
106 hashval_t shift;
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 }
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. */
146 static unsigned int
147 higher_prime_index (unsigned long n)
149 unsigned int low = 0;
150 unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]);
152 while (low != high)
154 unsigned int mid = low + (high - low) / 2;
155 if (n > prime_tab[mid].prime)
156 low = mid + 1;
157 else
158 high = mid;
161 /* If we've run out of primes, abort. */
162 if (n > prime_tab[low].prime)
163 abort ();
165 return low;
168 /* Return the current size of given hash table. */
170 static inline size_t
171 htab_size (htab_t htab)
173 return htab->size;
176 /* Return the current number of elements in given hash table. */
178 static inline size_t
179 htab_elements (htab_t htab)
181 return htab->n_elements - htab->n_deleted;
184 /* Return X % Y. */
186 static inline hashval_t
187 htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift)
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)
193 hashval_t t1, t2, t3, t4, q, r;
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);
202 return r;
205 /* Otherwise just use the native division routines. */
206 return x % y;
209 /* Compute the primary hash for HASH given HTAB's current size. */
211 static inline hashval_t
212 htab_mod (hashval_t hash, htab_t htab)
214 const struct prime_ent *p = &prime_tab[htab->size_prime_index];
215 return htab_mod_1 (hash, p->prime, p->inv, p->shift);
218 /* Compute the secondary hash for HASH given HTAB's current size. */
220 static inline hashval_t
221 htab_mod_m2 (hashval_t hash, htab_t htab)
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);
227 /* Create hash table of size SIZE. */
229 static htab_t
230 htab_create (size_t size)
232 htab_t result;
233 unsigned int size_prime_index;
235 size_prime_index = higher_prime_index (size);
236 size = prime_tab[size_prime_index].prime;
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;
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. */
254 static hash_entry_type *
255 find_empty_slot_for_expand (htab_t htab, hashval_t hash)
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;
262 if (*slot == HTAB_EMPTY_ENTRY)
263 return slot;
264 else if (*slot == HTAB_DELETED_ENTRY)
265 abort ();
267 hash2 = htab_mod_m2 (hash, htab);
268 for (;;)
270 index += hash2;
271 if (index >= size)
272 index -= size;
274 slot = htab->entries + index;
275 if (*slot == HTAB_EMPTY_ENTRY)
276 return slot;
277 else if (*slot == HTAB_DELETED_ENTRY)
278 abort ();
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. */
288 static htab_t
289 htab_expand (htab_t htab)
291 htab_t nhtab;
292 hash_entry_type *olimit;
293 hash_entry_type *p;
294 size_t osize, elts;
296 osize = htab->size;
297 olimit = htab->entries + osize;
298 elts = htab_elements (htab);
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;
308 p = htab->entries;
311 hash_entry_type x = *p;
313 if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
314 *find_empty_slot_for_expand (nhtab, htab_hash (x)) = x;
316 p++;
318 while (p < olimit);
320 htab_free (htab);
321 return nhtab;
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. */
327 static hash_entry_type
328 htab_find (htab_t htab, const hash_entry_type element)
330 hashval_t index, hash2, hash = htab_hash (element);
331 size_t size;
332 hash_entry_type entry;
334 size = htab_size (htab);
335 index = htab_mod (hash, htab);
337 entry = htab->entries[index];
338 if (entry == HTAB_EMPTY_ENTRY
339 || (entry != HTAB_DELETED_ENTRY && htab_eq (entry, element)))
340 return entry;
342 hash2 = htab_mod_m2 (hash, htab);
343 for (;;)
345 index += hash2;
346 if (index >= size)
347 index -= size;
349 entry = htab->entries[index];
350 if (entry == HTAB_EMPTY_ENTRY
351 || (entry != HTAB_DELETED_ENTRY && htab_eq (entry, element)))
352 return entry;
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. */
363 static hash_entry_type *
364 htab_find_slot (htab_t *htabp, const hash_entry_type element,
365 enum insert_option insert)
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;
373 size = htab_size (htab);
374 if (insert == INSERT && size * 3 <= htab->n_elements * 4)
376 htab = *htabp = htab_expand (htab);
377 size = htab_size (htab);
380 index = htab_mod (hash, htab);
382 first_deleted_slot = NULL;
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];
392 hash2 = htab_mod_m2 (hash, htab);
393 for (;;)
395 index += hash2;
396 if (index >= size)
397 index -= size;
399 entry = htab->entries[index];
400 if (entry == HTAB_EMPTY_ENTRY)
401 goto empty_entry;
402 else if (entry == HTAB_DELETED_ENTRY)
404 if (!first_deleted_slot)
405 first_deleted_slot = &htab->entries[index];
407 else if (htab_eq (entry, element))
408 return &htab->entries[index];
411 empty_entry:
412 if (insert == NO_INSERT)
413 return NULL;
415 if (first_deleted_slot)
417 htab->n_deleted--;
418 *first_deleted_slot = HTAB_EMPTY_ENTRY;
419 return first_deleted_slot;
422 htab->n_elements++;
423 return &htab->entries[index];
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. */
430 static inline void
431 htab_clear_slot (htab_t htab, hash_entry_type *slot)
433 if (slot < htab->entries || slot >= htab->entries + htab_size (htab)
434 || *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY)
435 abort ();
437 *slot = HTAB_DELETED_ENTRY;
438 htab->n_deleted++;
441 /* Returns a hash code for pointer P. Simplified version of evahash */
443 static inline hashval_t
444 hash_pointer (const void *p)
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;