gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008
   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 "tree.h"
  35 #include "symtab.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 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 struct ht *ident_hash;
  49
  50 static hashnode alloc_node (hash_table *);
  51 static int mark_ident (struct cpp_reader *, hashnode, const void *);
  52
  53 static void *
  54 stringpool_ggc_alloc (size_t x)
  55 {
  56   return ggc_alloc (x);
  57 }
  58
  59 /* Initialize the string pool.  */
  60 void
  61 init_stringpool (void)
  62 {
  63   /* Create with 16K (2^14) entries.  */
  64   ident_hash = ht_create (14);
  65   ident_hash->alloc_node = alloc_node;
  66   ident_hash->alloc_subobject = stringpool_ggc_alloc;
  67 }
  68
  69 /* Allocate a hash node.  */
  70 static hashnode
  71 alloc_node (hash_table *table ATTRIBUTE_UNUSED)
  72 {
  73   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  74 }
  75
  76 /* Allocate and return a string constant of length LENGTH, containing
  77    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  78    nul-terminated string, and the length is calculated using strlen.  */
  79
  80 const char *
  81 ggc_alloc_string (const char *contents, int length)
  82 {
  83   char *result;
  84
  85   if (length == -1)
  86     length = strlen (contents);
  87
  88   if (length == 0)
  89     return empty_string;
  90   if (length == 1 && ISDIGIT (contents[0]))
  91     return digit_string (contents[0] - '0');
  92
  93   result = GGC_NEWVAR (char, length + 1);
  94   memcpy (result, contents, length);
  95   result[length] = '\0';
  96   return (const char *) result;
  97 }
  98
  99 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
 100    If an identifier with that name has previously been referred to,
 101    the same node is returned this time.  */
 102
 103 #undef get_identifier
 104
 105 tree
 106 get_identifier (const char *text)
 107 {
 108   hashnode ht_node = ht_lookup (ident_hash,
 109                                 (const unsigned char *) text,
 110                                 strlen (text), HT_ALLOC);
 111
 112   /* ht_node can't be NULL here.  */
 113   return HT_IDENT_TO_GCC_IDENT (ht_node);
 114 }
 115
 116 /* Identical to get_identifier, except that the length is assumed
 117    known.  */
 118
 119 tree
 120 get_identifier_with_length (const char *text, size_t length)
 121 {
 122   hashnode ht_node = ht_lookup (ident_hash,
 123                                 (const unsigned char *) text,
 124                                 length, HT_ALLOC);
 125
 126   /* ht_node can't be NULL here.  */
 127   return HT_IDENT_TO_GCC_IDENT (ht_node);
 128 }
 129
 130 /* If an identifier with the name TEXT (a null-terminated string) has
 131    previously been referred to, return that node; otherwise return
 132    NULL_TREE.  */
 133
 134 tree
 135 maybe_get_identifier (const char *text)
 136 {
 137   hashnode ht_node;
 138
 139   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 140                        strlen (text), HT_NO_INSERT);
 141   if (ht_node)
 142     return HT_IDENT_TO_GCC_IDENT (ht_node);
 143
 144   return NULL_TREE;
 145 }
 146
 147 /* Report some basic statistics about the string pool.  */
 148
 149 void
 150 stringpool_statistics (void)
 151 {
 152   ht_dump_statistics (ident_hash);
 153 }
 154 \f
 155 /* Mark an identifier for GC.  */
 156
 157 static int
 158 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 159             const void *v ATTRIBUTE_UNUSED)
 160 {
 161   gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
 162   return 1;
 163 }
 164
 165 /* Return true if an identifier should be removed from the table.  */
 166
 167 static int
 168 maybe_delete_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 169                     const void *v ATTRIBUTE_UNUSED)
 170 {
 171   return !ggc_marked_p (HT_IDENT_TO_GCC_IDENT (h));
 172 }
 173
 174 /* Mark the trees hanging off the identifier node for GGC.  These are
 175    handled specially (not using gengtype) because identifiers are only
 176    roots during one part of compilation.  */
 177
 178 void
 179 ggc_mark_stringpool (void)
 180 {
 181   ht_forall (ident_hash, mark_ident, NULL);
 182 }
 183
 184 /* Purge the identifier hash of identifiers which are no longer
 185    referenced.  */
 186
 187 void
 188 ggc_purge_stringpool (void)
 189 {
 190   ht_purge (ident_hash, maybe_delete_ident, NULL);
 191 }
 192
 193 /* Pointer-walking routine for strings (not very interesting, since
 194    strings don't contain pointers).  */
 195
 196 void
 197 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 198             gt_pointer_operator op ATTRIBUTE_UNUSED,
 199             void *cookie ATTRIBUTE_UNUSED)
 200 {
 201 }
 202
 203 /* PCH pointer-walking routine for strings.  */
 204
 205 void
 206 gt_pch_n_S (const void *x)
 207 {
 208   gt_pch_note_object (CONST_CAST (void *, x), CONST_CAST (void *, x),
 209                       &gt_pch_p_S, gt_types_enum_last);
 210 }
 211 \f
 212 /* Handle saving and restoring the string pool for PCH.  */
 213
 214 /* SPD is saved in the PCH file and holds the information needed
 215    to restore the string pool.  */
 216
 217 struct GTY(()) string_pool_data {
 218   struct ht_identifier * *
 219     GTY((length ("%h.nslots"),
 220          nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
 221                      "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
 222     entries;
 223   unsigned int nslots;
 224   unsigned int nelements;
 225 };
 226
 227 static GTY(()) struct string_pool_data * spd;
 228
 229 /* Save the stringpool data in SPD.  */
 230
 231 void
 232 gt_pch_save_stringpool (void)
 233 {
 234   spd = GGC_NEW (struct string_pool_data);
 235   spd->nslots = ident_hash->nslots;
 236   spd->nelements = ident_hash->nelements;
 237   spd->entries = GGC_NEWVEC (struct ht_identifier *, spd->nslots);
 238   memcpy (spd->entries, ident_hash->entries,
 239           spd->nslots * sizeof (spd->entries[0]));
 240 }
 241
 242 /* Return the stringpool to its state before gt_pch_save_stringpool
 243    was called.  */
 244
 245 void
 246 gt_pch_fixup_stringpool (void)
 247 {
 248 }
 249
 250 /* A PCH file has been restored, which loaded SPD; fill the real hash table
 251    from SPD.  */
 252
 253 void
 254 gt_pch_restore_stringpool (void)
 255 {
 256   ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
 257   spd = NULL;
 258 }
 259
 260 #include "gt-stringpool.h"