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