1 /* String pool for GCC. 2 Copyright (C) 2000-2016 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 /* String text, identifier text and identifier node allocator. 21 Identifiers are uniquely stored in a hash table. 22 23 We use cpplib's hash table implementation. libiberty's 24 hashtab.c is not used because it requires 100% average space 25 overhead per string, which is unacceptable. Also, this algorithm 26 is faster. */ 27 28 #include "config.h" 29 #include "system.h" 30 #include "coretypes.h" 31 #include "tree.h" 32 33 /* The "" allocated string. */ 34 const char empty_string[] = ""; 35 36 /* Character strings, each containing a single decimal digit. 37 Written this way to save space. */ 38 static const char digit_vector[] = { 39 '0', 0, '1', 0, '2', 0, '3', 0, '4', 0, 40 '5', 0, '6', 0, '7', 0, '8', 0, '9', 0 41 }; 42 43 #define digit_string(d) (digit_vector + ((d) * 2)) 44 45 struct ht *ident_hash; 46 47 static hashnode alloc_node (cpp_hash_table *); 48 static int mark_ident (struct cpp_reader *, hashnode, const void *); 49 50 static void * 51 stringpool_ggc_alloc (size_t x) 52 { 53 return ggc_alloc_atomic (x); 54 } 55 56 /* Initialize the string pool. */ 57 void 58 init_stringpool (void) 59 { 60 /* Clean up if we're called more than once. 61 (We can't make this idempotent since identifiers contain state) */ 62 if (ident_hash) 63 ht_destroy (ident_hash); 64 65 /* Create with 16K (2^14) entries. */ 66 ident_hash = ht_create (14); 67 ident_hash->alloc_node = alloc_node; 68 ident_hash->alloc_subobject = stringpool_ggc_alloc; 69 } 70 71 /* Allocate a hash node. */ 72 static hashnode 73 alloc_node (cpp_hash_table *table ATTRIBUTE_UNUSED) 74 { 75 return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE)); 76 } 77 78 /* Allocate and return a string constant of length LENGTH, containing 79 CONTENTS. If LENGTH is -1, CONTENTS is assumed to be a 80 nul-terminated string, and the length is calculated using strlen. */ 81 82 const char * 83 ggc_alloc_string (const char *contents, int length MEM_STAT_DECL) 84 { 85 char *result; 86 87 if (length == -1) 88 length = strlen (contents); 89 90 if (length == 0) 91 return empty_string; 92 if (length == 1 && ISDIGIT (contents[0])) 93 return digit_string (contents[0] - '0'); 94 95 result = (char *) ggc_internal_cleared_alloc (length + 1 PASS_MEM_STAT); 96 memcpy (result, contents, length); 97 result[length] = '\0'; 98 return (const char *) result; 99 } 100 101 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string). 102 If an identifier with that name has previously been referred to, 103 the same node is returned this time. */ 104 105 #undef get_identifier 106 107 tree 108 get_identifier (const char *text) 109 { 110 hashnode ht_node = ht_lookup (ident_hash, 111 (const unsigned char *) text, 112 strlen (text), HT_ALLOC); 113 114 /* ht_node can't be NULL here. */ 115 return HT_IDENT_TO_GCC_IDENT (ht_node); 116 } 117 118 /* Identical to get_identifier, except that the length is assumed 119 known. */ 120 121 tree 122 get_identifier_with_length (const char *text, size_t length) 123 { 124 hashnode ht_node = ht_lookup (ident_hash, 125 (const unsigned char *) text, 126 length, HT_ALLOC); 127 128 /* ht_node can't be NULL here. */ 129 return HT_IDENT_TO_GCC_IDENT (ht_node); 130 } 131 132 /* If an identifier with the name TEXT (a null-terminated string) has 133 previously been referred to, return that node; otherwise return 134 NULL_TREE. */ 135 136 tree 137 maybe_get_identifier (const char *text) 138 { 139 hashnode ht_node; 140 141 ht_node = ht_lookup (ident_hash, (const unsigned char *) text, 142 strlen (text), HT_NO_INSERT); 143 if (ht_node) 144 return HT_IDENT_TO_GCC_IDENT (ht_node); 145 146 return NULL_TREE; 147 } 148 149 /* Report some basic statistics about the string pool. */ 150 151 void 152 stringpool_statistics (void) 153 { 154 ht_dump_statistics (ident_hash); 155 } 156 157 /* Mark an identifier for GC. */ 158 159 static int 160 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h, 161 const void *v ATTRIBUTE_UNUSED) 162 { 163 gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h)); 164 return 1; 165 } 166 167 /* Return true if an identifier should be removed from the table. */ 168 169 static int 170 maybe_delete_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h, 171 const void *v ATTRIBUTE_UNUSED) 172 { 173 return !ggc_marked_p (HT_IDENT_TO_GCC_IDENT (h)); 174 } 175 176 /* Mark the trees hanging off the identifier node for GGC. These are 177 handled specially (not using gengtype) because identifiers are only 178 roots during one part of compilation. */ 179 180 void 181 ggc_mark_stringpool (void) 182 { 183 ht_forall (ident_hash, mark_ident, NULL); 184 } 185 186 /* Purge the identifier hash of identifiers which are no longer 187 referenced. */ 188 189 void 190 ggc_purge_stringpool (void) 191 { 192 ht_purge (ident_hash, maybe_delete_ident, NULL); 193 } 194 195 /* Pointer-walking routine for strings (not very interesting, since 196 strings don't contain pointers). */ 197 198 void 199 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED, 200 gt_pointer_operator op ATTRIBUTE_UNUSED, 201 void *cookie ATTRIBUTE_UNUSED) 202 { 203 } 204 205 /* PCH pointer-walking routine for strings. */ 206 207 void 208 gt_pch_n_S (const void *x) 209 { 210 gt_pch_note_object (CONST_CAST (void *, x), CONST_CAST (void *, x), 211 >_pch_p_S); 212 } 213 214 215 /* User-callable entry point for marking string X. */ 216 217 void 218 gt_pch_nx (const char *& x) 219 { 220 gt_pch_n_S (x); 221 } 222 223 void 224 gt_pch_nx (unsigned char *& x) 225 { 226 gt_pch_n_S (x); 227 } 228 229 void 230 gt_pch_nx (unsigned char& x ATTRIBUTE_UNUSED) 231 { 232 } 233 234 void 235 gt_pch_nx (unsigned char *x, gt_pointer_operator op, void *cookie) 236 { 237 op (x, cookie); 238 } 239 240 /* Handle saving and restoring the string pool for PCH. */ 241 242 /* SPD is saved in the PCH file and holds the information needed 243 to restore the string pool. */ 244 245 struct GTY(()) string_pool_data { 246 ht_identifier_ptr * 247 GTY((length ("%h.nslots"), 248 nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL", 249 "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL"))) 250 entries; 251 unsigned int nslots; 252 unsigned int nelements; 253 }; 254 255 static GTY(()) struct string_pool_data * spd; 256 257 /* Save the stringpool data in SPD. */ 258 259 void 260 gt_pch_save_stringpool (void) 261 { 262 spd = ggc_alloc<string_pool_data> (); 263 spd->nslots = ident_hash->nslots; 264 spd->nelements = ident_hash->nelements; 265 spd->entries = ggc_vec_alloc<ht_identifier_ptr> (spd->nslots); 266 memcpy (spd->entries, ident_hash->entries, 267 spd->nslots * sizeof (spd->entries[0])); 268 } 269 270 /* Return the stringpool to its state before gt_pch_save_stringpool 271 was called. */ 272 273 void 274 gt_pch_fixup_stringpool (void) 275 { 276 } 277 278 /* A PCH file has been restored, which loaded SPD; fill the real hash table 279 from SPD. */ 280 281 void 282 gt_pch_restore_stringpool (void) 283 { 284 ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false); 285 spd = NULL; 286 } 287 288 #include "gt-stringpool.h" 289