gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000-2015 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 "ggc-internal.h"
  32 #include "input.h"
  33 #include "alias.h"
  34 #include "symtab.h"
  35 #include "options.h"
  36 #include "tree.h"
  37 #include "cpplib.h"
  38
  39 /* The "" allocated string.  */
  40 const char empty_string[] = "";
  41
  42 /* Character strings, each containing a single decimal digit.
  43    Written this way to save space.  */
  44 static const char digit_vector[] = {
  45   '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
  46   '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
  47 };
  48
  49 #define digit_string(d) (digit_vector + ((d) * 2))
  50
  51 struct ht *ident_hash;
  52
  53 static hashnode alloc_node (cpp_hash_table *);
  54 static int mark_ident (struct cpp_reader *, hashnode, const void *);
  55
  56 static void *
  57 stringpool_ggc_alloc (size_t x)
  58 {
  59   return ggc_alloc_atomic (x);
  60 }
  61
  62 /* Initialize the string pool.  */
  63 void
  64 init_stringpool (void)
  65 {
  66   /* Clean up if we're called more than once.
  67      (We can't make this idempotent since identifiers contain state) */
  68   if (ident_hash)
  69     ht_destroy (ident_hash);
  70
  71   /* Create with 16K (2^14) entries.  */
  72   ident_hash = ht_create (14);
  73   ident_hash->alloc_node = alloc_node;
  74   ident_hash->alloc_subobject = stringpool_ggc_alloc;
  75 }
  76
  77 /* Allocate a hash node.  */
  78 static hashnode
  79 alloc_node (cpp_hash_table *table ATTRIBUTE_UNUSED)
  80 {
  81   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  82 }
  83
  84 /* Allocate and return a string constant of length LENGTH, containing
  85    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  86    nul-terminated string, and the length is calculated using strlen.  */
  87
  88 const char *
  89 ggc_alloc_string (const char *contents, int length MEM_STAT_DECL)
  90 {
  91   char *result;
  92
  93   if (length == -1)
  94     length = strlen (contents);
  95
  96   if (length == 0)
  97     return empty_string;
  98   if (length == 1 && ISDIGIT (contents[0]))
  99     return digit_string (contents[0] - '0');
 100
 101   result = (char *) ggc_internal_cleared_alloc (length + 1 PASS_MEM_STAT);
 102   memcpy (result, contents, length);
 103   result[length] = '\0';
 104   return (const char *) result;
 105 }
 106
 107 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
 108    If an identifier with that name has previously been referred to,
 109    the same node is returned this time.  */
 110
 111 #undef get_identifier
 112
 113 tree
 114 get_identifier (const char *text)
 115 {
 116   hashnode ht_node = ht_lookup (ident_hash,
 117                                 (const unsigned char *) text,
 118                                 strlen (text), HT_ALLOC);
 119
 120   /* ht_node can't be NULL here.  */
 121   return HT_IDENT_TO_GCC_IDENT (ht_node);
 122 }
 123
 124 /* Identical to get_identifier, except that the length is assumed
 125    known.  */
 126
 127 tree
 128 get_identifier_with_length (const char *text, size_t length)
 129 {
 130   hashnode ht_node = ht_lookup (ident_hash,
 131                                 (const unsigned char *) text,
 132                                 length, HT_ALLOC);
 133
 134   /* ht_node can't be NULL here.  */
 135   return HT_IDENT_TO_GCC_IDENT (ht_node);
 136 }
 137
 138 /* If an identifier with the name TEXT (a null-terminated string) has
 139    previously been referred to, return that node; otherwise return
 140    NULL_TREE.  */
 141
 142 tree
 143 maybe_get_identifier (const char *text)
 144 {
 145   hashnode ht_node;
 146
 147   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 148                        strlen (text), HT_NO_INSERT);
 149   if (ht_node)
 150     return HT_IDENT_TO_GCC_IDENT (ht_node);
 151
 152   return NULL_TREE;
 153 }
 154
 155 /* Report some basic statistics about the string pool.  */
 156
 157 void
 158 stringpool_statistics (void)
 159 {
 160   ht_dump_statistics (ident_hash);
 161 }
 162 \f
 163 /* Mark an identifier for GC.  */
 164
 165 static int
 166 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 167             const void *v ATTRIBUTE_UNUSED)
 168 {
 169   gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
 170   return 1;
 171 }
 172
 173 /* Return true if an identifier should be removed from the table.  */
 174
 175 static int
 176 maybe_delete_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 177                     const void *v ATTRIBUTE_UNUSED)
 178 {
 179   return !ggc_marked_p (HT_IDENT_TO_GCC_IDENT (h));
 180 }
 181
 182 /* Mark the trees hanging off the identifier node for GGC.  These are
 183    handled specially (not using gengtype) because identifiers are only
 184    roots during one part of compilation.  */
 185
 186 void
 187 ggc_mark_stringpool (void)
 188 {
 189   ht_forall (ident_hash, mark_ident, NULL);
 190 }
 191
 192 /* Purge the identifier hash of identifiers which are no longer
 193    referenced.  */
 194
 195 void
 196 ggc_purge_stringpool (void)
 197 {
 198   ht_purge (ident_hash, maybe_delete_ident, NULL);
 199 }
 200
 201 /* Pointer-walking routine for strings (not very interesting, since
 202    strings don't contain pointers).  */
 203
 204 void
 205 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 206             gt_pointer_operator op ATTRIBUTE_UNUSED,
 207             void *cookie ATTRIBUTE_UNUSED)
 208 {
 209 }
 210
 211 /* PCH pointer-walking routine for strings.  */
 212
 213 void
 214 gt_pch_n_S (const void *x)
 215 {
 216   gt_pch_note_object (CONST_CAST (void *, x), CONST_CAST (void *, x),
 217                       &gt_pch_p_S);
 218 }
 219
 220
 221 /* User-callable entry point for marking string X.  */
 222
 223 void
 224 gt_pch_nx (const char *& x)
 225 {
 226   gt_pch_n_S (x);
 227 }
 228
 229 void
 230 gt_pch_nx (unsigned char *& x)
 231 {
 232   gt_pch_n_S (x);
 233 }
 234
 235 void
 236 gt_pch_nx (unsigned char& x ATTRIBUTE_UNUSED)
 237 {
 238 }
 239
 240 void
 241 gt_pch_nx (unsigned char *x, gt_pointer_operator op, void *cookie)
 242 {
 243   op (x, cookie);
 244 }
 245 \f
 246 /* Handle saving and restoring the string pool for PCH.  */
 247
 248 /* SPD is saved in the PCH file and holds the information needed
 249    to restore the string pool.  */
 250
 251 struct GTY(()) string_pool_data {
 252   ht_identifier_ptr *
 253     GTY((length ("%h.nslots"),
 254          nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
 255                      "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
 256     entries;
 257   unsigned int nslots;
 258   unsigned int nelements;
 259 };
 260
 261 static GTY(()) struct string_pool_data * spd;
 262
 263 /* Save the stringpool data in SPD.  */
 264
 265 void
 266 gt_pch_save_stringpool (void)
 267 {
 268   spd = ggc_alloc<string_pool_data> ();
 269   spd->nslots = ident_hash->nslots;
 270   spd->nelements = ident_hash->nelements;
 271   spd->entries = ggc_vec_alloc<ht_identifier_ptr> (spd->nslots);
 272   memcpy (spd->entries, ident_hash->entries,
 273           spd->nslots * sizeof (spd->entries[0]));
 274 }
 275
 276 /* Return the stringpool to its state before gt_pch_save_stringpool
 277    was called.  */
 278
 279 void
 280 gt_pch_fixup_stringpool (void)
 281 {
 282 }
 283
 284 /* A PCH file has been restored, which loaded SPD; fill the real hash table
 285    from SPD.  */
 286
 287 void
 288 gt_pch_restore_stringpool (void)
 289 {
 290   ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
 291   spd = NULL;
 292 }
 293
 294 #include "gt-stringpool.h"