gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005
   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 2, 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 COPYING.  If not, write to the Free
  19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  20 02111-1307, USA.  */
  21
  22 /* String text, identifier text and identifier node allocator.  Strings
  23    allocated by ggc_alloc_string are stored in an obstack which is
  24    never shrunk.  Identifiers are uniquely stored in a hash table.
  25
  26    We use cpplib's hash table implementation.  libiberty's
  27    hashtab.c is not used because it requires 100% average space
  28    overhead per string, which is unacceptable.  Also, this algorithm
  29    is faster.  */
  30
  31 #include "config.h"
  32 #include "system.h"
  33 #include "coretypes.h"
  34 #include "tm.h"
  35 #include "ggc.h"
  36 #include "tree.h"
  37 #include "symtab.h"
  38 #include "cpplib.h"
  39
  40 /* The "" allocated string.  */
  41 const char empty_string[] = "";
  42
  43 /* Character strings, each containing a single decimal digit.
  44    Written this way to save space.  */
  45 const char digit_vector[] = {
  46   '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
  47   '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
  48 };
  49
  50 struct ht *ident_hash;
  51 static struct obstack string_stack;
  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 (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   gcc_obstack_init (&string_stack);
  71 }
  72
  73 /* Allocate a hash node.  */
  74 static hashnode
  75 alloc_node (hash_table *table ATTRIBUTE_UNUSED)
  76 {
  77   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  78 }
  79
  80 /* Allocate and return a string constant of length LENGTH, containing
  81    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  82    nul-terminated string, and the length is calculated using strlen.
  83    If the same string constant has been allocated before, that copy is
  84    returned this time too.  */
  85
  86 const char *
  87 ggc_alloc_string (const char *contents, int length)
  88 {
  89   if (length == -1)
  90     length = strlen (contents);
  91
  92   if (length == 0)
  93     return empty_string;
  94   if (length == 1 && ISDIGIT (contents[0]))
  95     return digit_string (contents[0] - '0');
  96
  97   obstack_grow0 (&string_stack, contents, length);
  98   return obstack_finish (&string_stack);
  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 /* Mark the trees hanging off the identifier node for GGC.  These are
 168    handled specially (not using gengtype) because of the special
 169    treatment for strings.  */
 170
 171 void
 172 ggc_mark_stringpool (void)
 173 {
 174   ht_forall (ident_hash, mark_ident, NULL);
 175 }
 176
 177 /* Strings are _not_ GCed, but this routine exists so that a separate
 178    roots table isn't needed for the few global variables that refer
 179    to strings.  */
 180
 181 void
 182 gt_ggc_m_S (void *x ATTRIBUTE_UNUSED)
 183 {
 184 }
 185
 186 /* Pointer-walking routine for strings (not very interesting, since
 187    strings don't contain pointers).  */
 188
 189 void
 190 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 191             gt_pointer_operator op ATTRIBUTE_UNUSED,
 192             void *cookie ATTRIBUTE_UNUSED)
 193 {
 194 }
 195
 196 /* PCH pointer-walking routine for strings.  */
 197
 198 void
 199 gt_pch_n_S (const void *x)
 200 {
 201   gt_pch_note_object ((void *)x, (void *)x, &gt_pch_p_S,
 202                       gt_types_enum_last);
 203 }
 204 \f
 205 /* Handle saving and restoring the string pool for PCH.  */
 206
 207 /* SPD is saved in the PCH file and holds the information needed
 208    to restore the string pool.  */
 209
 210 struct string_pool_data GTY(())
 211 {
 212   struct ht_identifier * *
 213     GTY((length ("%h.nslots"),
 214          nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
 215                      "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
 216     entries;
 217   unsigned int nslots;
 218   unsigned int nelements;
 219 };
 220
 221 static GTY(()) struct string_pool_data * spd;
 222
 223 /* Save the stringpool data in SPD.  */
 224
 225 void
 226 gt_pch_save_stringpool (void)
 227 {
 228   spd = ggc_alloc (sizeof (*spd));
 229   spd->nslots = ident_hash->nslots;
 230   spd->nelements = ident_hash->nelements;
 231   spd->entries = ggc_alloc (sizeof (spd->entries[0]) * spd->nslots);
 232   memcpy (spd->entries, ident_hash->entries,
 233           spd->nslots * sizeof (spd->entries[0]));
 234 }
 235
 236 /* Return the stringpool to its state before gt_pch_save_stringpool
 237    was called.  */
 238
 239 void
 240 gt_pch_fixup_stringpool (void)
 241 {
 242 }
 243
 244 /* A PCH file has been restored, which loaded SPD; fill the real hash table
 245    from SPD.  */
 246
 247 void
 248 gt_pch_restore_stringpool (void)
 249 {
 250   ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
 251   spd = NULL;
 252 }
 253
 254 #include "gt-stringpool.h"