gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
   3    Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 /* String text, identifier text and identifier node allocator.
  22    Identifiers are uniquely stored in a hash table.
  23
  24    We use cpplib's hash table implementation.  libiberty's
  25    hashtab.c is not used because it requires 100% average space
  26    overhead per string, which is unacceptable.  Also, this algorithm
  27    is faster.  */
  28
  29 #include "config.h"
  30 #include "system.h"
  31 #include "coretypes.h"
  32 #include "tm.h"
  33 #include "ggc.h"
  34 #include "ggc-internal.h"
  35 #include "tree.h"
  36 #include "symtab.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 (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   /* Create with 16K (2^14) entries.  */
  67   ident_hash = ht_create (14);
  68   ident_hash->alloc_node = alloc_node;
  69   ident_hash->alloc_subobject = stringpool_ggc_alloc;
  70 }
  71
  72 /* Allocate a hash node.  */
  73 static hashnode
  74 alloc_node (hash_table *table ATTRIBUTE_UNUSED)
  75 {
  76   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  77 }
  78
  79 /* Allocate and return a string constant of length LENGTH, containing
  80    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  81    nul-terminated string, and the length is calculated using strlen.  */
  82
  83 const char *
  84 ggc_alloc_string_stat (const char *contents, int length MEM_STAT_DECL)
  85 {
  86   char *result;
  87
  88   if (length == -1)
  89     length = strlen (contents);
  90
  91   if (length == 0)
  92     return empty_string;
  93   if (length == 1 && ISDIGIT (contents[0]))
  94     return digit_string (contents[0] - '0');
  95
  96   result = (char *) ggc_alloc_atomic_stat (length + 1 PASS_MEM_STAT);
  97   memcpy (result, contents, length);
  98   result[length] = '\0';
  99   return (const char *) result;
 100 }
 101
 102 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
 103    If an identifier with that name has previously been referred to,
 104    the same node is returned this time.  */
 105
 106 #undef get_identifier
 107
 108 tree
 109 get_identifier (const char *text)
 110 {
 111   hashnode ht_node = ht_lookup (ident_hash,
 112                                 (const unsigned char *) text,
 113                                 strlen (text), HT_ALLOC);
 114
 115   /* ht_node can't be NULL here.  */
 116   return HT_IDENT_TO_GCC_IDENT (ht_node);
 117 }
 118
 119 /* Identical to get_identifier, except that the length is assumed
 120    known.  */
 121
 122 tree
 123 get_identifier_with_length (const char *text, size_t length)
 124 {
 125   hashnode ht_node = ht_lookup (ident_hash,
 126                                 (const unsigned char *) text,
 127                                 length, HT_ALLOC);
 128
 129   /* ht_node can't be NULL here.  */
 130   return HT_IDENT_TO_GCC_IDENT (ht_node);
 131 }
 132
 133 /* If an identifier with the name TEXT (a null-terminated string) has
 134    previously been referred to, return that node; otherwise return
 135    NULL_TREE.  */
 136
 137 tree
 138 maybe_get_identifier (const char *text)
 139 {
 140   hashnode ht_node;
 141
 142   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 143                        strlen (text), HT_NO_INSERT);
 144   if (ht_node)
 145     return HT_IDENT_TO_GCC_IDENT (ht_node);
 146
 147   return NULL_TREE;
 148 }
 149
 150 /* Report some basic statistics about the string pool.  */
 151
 152 void
 153 stringpool_statistics (void)
 154 {
 155   ht_dump_statistics (ident_hash);
 156 }
 157 \f
 158 /* Mark an identifier for GC.  */
 159
 160 static int
 161 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 162             const void *v ATTRIBUTE_UNUSED)
 163 {
 164   gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
 165   return 1;
 166 }
 167
 168 /* Return true if an identifier should be removed from the table.  */
 169
 170 static int
 171 maybe_delete_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 172                     const void *v ATTRIBUTE_UNUSED)
 173 {
 174   return !ggc_marked_p (HT_IDENT_TO_GCC_IDENT (h));
 175 }
 176
 177 /* Mark the trees hanging off the identifier node for GGC.  These are
 178    handled specially (not using gengtype) because identifiers are only
 179    roots during one part of compilation.  */
 180
 181 void
 182 ggc_mark_stringpool (void)
 183 {
 184   ht_forall (ident_hash, mark_ident, NULL);
 185 }
 186
 187 /* Purge the identifier hash of identifiers which are no longer
 188    referenced.  */
 189
 190 void
 191 ggc_purge_stringpool (void)
 192 {
 193   ht_purge (ident_hash, maybe_delete_ident, NULL);
 194 }
 195
 196 /* Pointer-walking routine for strings (not very interesting, since
 197    strings don't contain pointers).  */
 198
 199 void
 200 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 201             gt_pointer_operator op ATTRIBUTE_UNUSED,
 202             void *cookie ATTRIBUTE_UNUSED)
 203 {
 204 }
 205
 206 /* PCH pointer-walking routine for strings.  */
 207
 208 void
 209 gt_pch_n_S (const void *x)
 210 {
 211   gt_pch_note_object (CONST_CAST (void *, x), CONST_CAST (void *, x),
 212                       &gt_pch_p_S, gt_types_enum_last);
 213 }
 214 \f
 215 /* Handle saving and restoring the string pool for PCH.  */
 216
 217 /* SPD is saved in the PCH file and holds the information needed
 218    to restore the string pool.  */
 219
 220 struct GTY(()) string_pool_data {
 221   ht_identifier_ptr *
 222     GTY((length ("%h.nslots"),
 223          nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
 224                      "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
 225     entries;
 226   unsigned int nslots;
 227   unsigned int nelements;
 228 };
 229
 230 static GTY(()) struct string_pool_data * spd;
 231
 232 /* Save the stringpool data in SPD.  */
 233
 234 void
 235 gt_pch_save_stringpool (void)
 236 {
 237   spd = ggc_alloc_string_pool_data ();
 238   spd->nslots = ident_hash->nslots;
 239   spd->nelements = ident_hash->nelements;
 240   spd->entries = ggc_alloc_vec_ht_identifier_ptr (spd->nslots);
 241   memcpy (spd->entries, ident_hash->entries,
 242           spd->nslots * sizeof (spd->entries[0]));
 243 }
 244
 245 /* Return the stringpool to its state before gt_pch_save_stringpool
 246    was called.  */
 247
 248 void
 249 gt_pch_fixup_stringpool (void)
 250 {
 251 }
 252
 253 /* A PCH file has been restored, which loaded SPD; fill the real hash table
 254    from SPD.  */
 255
 256 void
 257 gt_pch_restore_stringpool (void)
 258 {
 259   ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
 260   spd = NULL;
 261 }
 262
 263 #include "gt-stringpool.h"