1 /* A type-safe hash table template. 2 Copyright (C) 2012-2015 Free Software Foundation, Inc. 3 Contributed by Lawrence Crowl <crowl@google.com> 4 5 This file is part of GCC. 6 7 GCC is free software; you can redistribute it and/or modify it under 8 the terms of the GNU General Public License as published by the Free 9 Software Foundation; either version 3, or (at your option) any later 10 version. 11 12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13 WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 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 /* This file implements a typed hash table. 23 The implementation borrows from libiberty's hashtab. */ 24 25 #ifdef GENERATOR_FILE 26 #include "bconfig.h" 27 #else 28 #include "config.h" 29 #endif 30 #include "system.h" 31 #include "coretypes.h" 32 #include "hash-table.h" 33 34 35 /* Table of primes and multiplicative inverses. 36 37 Note that these are not minimally reduced inverses. Unlike when generating 38 code to divide by a constant, we want to be able to use the same algorithm 39 all the time. All of these inverses (are implied to) have bit 32 set. 40 41 For the record, here's the function that computed the table; it's a 42 vastly simplified version of the function of the same name from gcc. */ 43 44 struct prime_ent const prime_tab[] = { 45 { 7, 0x24924925, 0x9999999b, 2 }, 46 { 13, 0x3b13b13c, 0x745d1747, 3 }, 47 { 31, 0x08421085, 0x1a7b9612, 4 }, 48 { 61, 0x0c9714fc, 0x15b1e5f8, 5 }, 49 { 127, 0x02040811, 0x0624dd30, 6 }, 50 { 251, 0x05197f7e, 0x073260a5, 7 }, 51 { 509, 0x01824366, 0x02864fc8, 8 }, 52 { 1021, 0x00c0906d, 0x014191f7, 9 }, 53 { 2039, 0x0121456f, 0x0161e69e, 10 }, 54 { 4093, 0x00300902, 0x00501908, 11 }, 55 { 8191, 0x00080041, 0x00180241, 12 }, 56 { 16381, 0x000c0091, 0x00140191, 13 }, 57 { 32749, 0x002605a5, 0x002a06e6, 14 }, 58 { 65521, 0x000f00e2, 0x00110122, 15 }, 59 { 131071, 0x00008001, 0x00018003, 16 }, 60 { 262139, 0x00014002, 0x0001c004, 17 }, 61 { 524287, 0x00002001, 0x00006001, 18 }, 62 { 1048573, 0x00003001, 0x00005001, 19 }, 63 { 2097143, 0x00004801, 0x00005801, 20 }, 64 { 4194301, 0x00000c01, 0x00001401, 21 }, 65 { 8388593, 0x00001e01, 0x00002201, 22 }, 66 { 16777213, 0x00000301, 0x00000501, 23 }, 67 { 33554393, 0x00001381, 0x00001481, 24 }, 68 { 67108859, 0x00000141, 0x000001c1, 25 }, 69 { 134217689, 0x000004e1, 0x00000521, 26 }, 70 { 268435399, 0x00000391, 0x000003b1, 27 }, 71 { 536870909, 0x00000019, 0x00000029, 28 }, 72 { 1073741789, 0x0000008d, 0x00000095, 29 }, 73 { 2147483647, 0x00000003, 0x00000007, 30 }, 74 /* Avoid "decimal constant so large it is unsigned" for 4294967291. */ 75 { 0xfffffffb, 0x00000006, 0x00000008, 31 } 76 }; 77 78 /* The following function returns an index into the above table of the 79 nearest prime number which is greater than N, and near a power of two. */ 80 81 unsigned int 82 hash_table_higher_prime_index (unsigned long n) 83 { 84 unsigned int low = 0; 85 unsigned int high = sizeof (prime_tab) / sizeof (prime_tab[0]); 86 87 while (low != high) 88 { 89 unsigned int mid = low + (high - low) / 2; 90 if (n > prime_tab[mid].prime) 91 low = mid + 1; 92 else 93 high = mid; 94 } 95 96 /* If we've run out of primes, abort. */ 97 gcc_assert (n <= prime_tab[low].prime); 98 99 return low; 100 } 101 102