gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000-2013 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.h"
  32 #include "ggc-internal.h"
  33 #include "tree.h"
  34 #include "symtab.h"
  35 #include "cpplib.h"
  36
  37 /* The "" allocated string.  */
  38 const char empty_string[] = "";
  39
  40 /* Character strings, each containing a single decimal digit.
  41    Written this way to save space.  */
  42 static const char digit_vector[] = {
  43   '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
  44   '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
  45 };
  46
  47 #define digit_string(d) (digit_vector + ((d) * 2))
  48
  49 struct ht *ident_hash;
  50
  51 static hashnode alloc_node (cpp_hash_table *);
  52 static int mark_ident (struct cpp_reader *, hashnode, const void *);
  53
  54 static void *
  55 stringpool_ggc_alloc (size_t x)
  56 {
  57   return ggc_alloc_atomic (x);
  58 }
  59
  60 /* Initialize the string pool.  */
  61 void
  62 init_stringpool (void)
  63 {
  64   /* Create with 16K (2^14) entries.  */
  65   ident_hash = ht_create (14);
  66   ident_hash->alloc_node = alloc_node;
  67   ident_hash->alloc_subobject = stringpool_ggc_alloc;
  68 }
  69
  70 /* Allocate a hash node.  */
  71 static hashnode
  72 alloc_node (cpp_hash_table *table ATTRIBUTE_UNUSED)
  73 {
  74   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  75 }
  76
  77 /* Allocate and return a string constant of length LENGTH, containing
  78    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  79    nul-terminated string, and the length is calculated using strlen.  */
  80
  81 const char *
  82 ggc_alloc_string_stat (const char *contents, int length MEM_STAT_DECL)
  83 {
  84   char *result;
  85
  86   if (length == -1)
  87     length = strlen (contents);
  88
  89   if (length == 0)
  90     return empty_string;
  91   if (length == 1 && ISDIGIT (contents[0]))
  92     return digit_string (contents[0] - '0');
  93
  94   result = (char *) ggc_alloc_atomic_stat (length + 1 PASS_MEM_STAT);
  95   memcpy (result, contents, length);
  96   result[length] = '\0';
  97   return (const char *) result;
  98 }
  99
 100 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
 101    If an identifier with that name has previously been referred to,
 102    the same node is returned this time.  */
 103
 104 #undef get_identifier
 105
 106 tree
 107 get_identifier (const char *text)
 108 {
 109   hashnode ht_node = ht_lookup (ident_hash,
 110                                 (const unsigned char *) text,
 111                                 strlen (text), HT_ALLOC);
 112
 113   /* ht_node can't be NULL here.  */
 114   return HT_IDENT_TO_GCC_IDENT (ht_node);
 115 }
 116
 117 /* Identical to get_identifier, except that the length is assumed
 118    known.  */
 119
 120 tree
 121 get_identifier_with_length (const char *text, size_t length)
 122 {
 123   hashnode ht_node = ht_lookup (ident_hash,
 124                                 (const unsigned char *) text,
 125                                 length, HT_ALLOC);
 126
 127   /* ht_node can't be NULL here.  */
 128   return HT_IDENT_TO_GCC_IDENT (ht_node);
 129 }
 130
 131 /* If an identifier with the name TEXT (a null-terminated string) has
 132    previously been referred to, return that node; otherwise return
 133    NULL_TREE.  */
 134
 135 tree
 136 maybe_get_identifier (const char *text)
 137 {
 138   hashnode ht_node;
 139
 140   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 141                        strlen (text), HT_NO_INSERT);
 142   if (ht_node)
 143     return HT_IDENT_TO_GCC_IDENT (ht_node);
 144
 145   return NULL_TREE;
 146 }
 147
 148 /* Report some basic statistics about the string pool.  */
 149
 150 void
 151 stringpool_statistics (void)
 152 {
 153   ht_dump_statistics (ident_hash);
 154 }
 155 \f
 156 /* Mark an identifier for GC.  */
 157
 158 static int
 159 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 160             const void *v ATTRIBUTE_UNUSED)
 161 {
 162   gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
 163   return 1;
 164 }
 165
 166 /* Return true if an identifier should be removed from the table.  */
 167
 168 static int
 169 maybe_delete_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 170                     const void *v ATTRIBUTE_UNUSED)
 171 {
 172   return !ggc_marked_p (HT_IDENT_TO_GCC_IDENT (h));
 173 }
 174
 175 /* Mark the trees hanging off the identifier node for GGC.  These are
 176    handled specially (not using gengtype) because identifiers are only
 177    roots during one part of compilation.  */
 178
 179 void
 180 ggc_mark_stringpool (void)
 181 {
 182   ht_forall (ident_hash, mark_ident, NULL);
 183 }
 184
 185 /* Purge the identifier hash of identifiers which are no longer
 186    referenced.  */
 187
 188 void
 189 ggc_purge_stringpool (void)
 190 {
 191   ht_purge (ident_hash, maybe_delete_ident, NULL);
 192 }
 193
 194 /* Pointer-walking routine for strings (not very interesting, since
 195    strings don't contain pointers).  */
 196
 197 void
 198 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 199             gt_pointer_operator op ATTRIBUTE_UNUSED,
 200             void *cookie ATTRIBUTE_UNUSED)
 201 {
 202 }
 203
 204 /* PCH pointer-walking routine for strings.  */
 205
 206 void
 207 gt_pch_n_S (const void *x)
 208 {
 209   gt_pch_note_object (CONST_CAST (void *, x), CONST_CAST (void *, x),
 210                       &gt_pch_p_S);
 211 }
 212
 213
 214 /* User-callable entry point for marking string X.  */
 215
 216 void
 217 gt_pch_nx (const char *& x)
 218 {
 219   gt_pch_n_S (x);
 220 }
 221
 222 void
 223 gt_pch_nx (unsigned char *& x)
 224 {
 225   gt_pch_n_S (x);
 226 }
 227
 228 void
 229 gt_pch_nx (unsigned char& x ATTRIBUTE_UNUSED)
 230 {
 231 }
 232
 233 void
 234 gt_pch_nx (unsigned char *x, gt_pointer_operator op, void *cookie)
 235 {
 236   op (x, cookie);
 237 }
 238 \f
 239 /* Handle saving and restoring the string pool for PCH.  */
 240
 241 /* SPD is saved in the PCH file and holds the information needed
 242    to restore the string pool.  */
 243
 244 struct GTY(()) string_pool_data {
 245   ht_identifier_ptr *
 246     GTY((length ("%h.nslots"),
 247          nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
 248                      "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
 249     entries;
 250   unsigned int nslots;
 251   unsigned int nelements;
 252 };
 253
 254 static GTY(()) struct string_pool_data * spd;
 255
 256 /* Save the stringpool data in SPD.  */
 257
 258 void
 259 gt_pch_save_stringpool (void)
 260 {
 261   spd = ggc_alloc_string_pool_data ();
 262   spd->nslots = ident_hash->nslots;
 263   spd->nelements = ident_hash->nelements;
 264   spd->entries = ggc_alloc_vec_ht_identifier_ptr (spd->nslots);
 265   memcpy (spd->entries, ident_hash->entries,
 266           spd->nslots * sizeof (spd->entries[0]));
 267 }
 268
 269 /* Return the stringpool to its state before gt_pch_save_stringpool
 270    was called.  */
 271
 272 void
 273 gt_pch_fixup_stringpool (void)
 274 {
 275 }
 276
 277 /* A PCH file has been restored, which loaded SPD; fill the real hash table
 278    from SPD.  */
 279
 280 void
 281 gt_pch_restore_stringpool (void)
 282 {
 283   ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
 284   spd = NULL;
 285 }
 286
 287 #include "gt-stringpool.h"