gcc/stringpool.c

   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 \f
 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                       &gt_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 \f
 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"