gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000, 2001, 2002, 2003 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 2, 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 COPYING.  If not, write to the Free
  18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
  19 02111-1307, USA.  */
  20
  21 /* String text, identifier text and identifier node allocator.  Strings
  22    allocated by ggc_alloc_string are stored in an obstack which is
  23    never shrunk.  Identifiers are uniquely stored in a hash table.
  24
  25    We have our own private hash table implementation.  libiberty's
  26    hashtab.c is not used because it requires 100% average space
  27    overhead per string, which is unacceptable.  Also, this algorithm
  28    is faster.  */
  29
  30 #include "config.h"
  31 #include "system.h"
  32 #include "coretypes.h"
  33 #include "tm.h"
  34 #include "ggc.h"
  35 #include "tree.h"
  36 #include "hashtable.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 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 struct ht *ident_hash;
  50 static struct obstack string_stack;
  51
  52 static hashnode alloc_node (hash_table *);
  53 static int mark_ident (struct cpp_reader *, hashnode, const void *);
  54 static int ht_copy_and_clear (struct cpp_reader *, hashnode, const void *);
  55
  56 /* Initialize the string pool.  */
  57 void
  58 init_stringpool (void)
  59 {
  60   /* Create with 16K (2^14) entries.  */
  61   ident_hash = ht_create (14);
  62   ident_hash->alloc_node = alloc_node;
  63   gcc_obstack_init (&string_stack);
  64 }
  65
  66 /* Allocate a hash node.  */
  67 static hashnode
  68 alloc_node (hash_table *table ATTRIBUTE_UNUSED)
  69 {
  70   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  71 }
  72
  73 /* Allocate and return a string constant of length LENGTH, containing
  74    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  75    nul-terminated string, and the length is calculated using strlen.
  76    If the same string constant has been allocated before, that copy is
  77    returned this time too.  */
  78
  79 const char *
  80 ggc_alloc_string (const char *contents, int length)
  81 {
  82   if (length == -1)
  83     length = strlen (contents);
  84
  85   if (length == 0)
  86     return empty_string;
  87   if (length == 1 && ISDIGIT (contents[0]))
  88     return digit_string (contents[0] - '0');
  89
  90   obstack_grow0 (&string_stack, contents, length);
  91   return obstack_finish (&string_stack);
  92 }
  93
  94 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
  95    If an identifier with that name has previously been referred to,
  96    the same node is returned this time.  */
  97
  98 tree
  99 get_identifier (const char *text)
 100 {
 101   hashnode ht_node = ht_lookup (ident_hash,
 102                                 (const unsigned char *) text,
 103                                 strlen (text), HT_ALLOC);
 104
 105   /* ht_node can't be NULL here.  */
 106   return HT_IDENT_TO_GCC_IDENT (ht_node);
 107 }
 108
 109 /* Identical to get_identifier, except that the length is assumed
 110    known.  */
 111
 112 tree
 113 get_identifier_with_length (const char *text, unsigned int length)
 114 {
 115   hashnode ht_node = ht_lookup (ident_hash,
 116                                 (const unsigned char *) text,
 117                                 length, HT_ALLOC);
 118
 119   /* ht_node can't be NULL here.  */
 120   return HT_IDENT_TO_GCC_IDENT (ht_node);
 121 }
 122
 123 /* If an identifier with the name TEXT (a null-terminated string) has
 124    previously been referred to, return that node; otherwise return
 125    NULL_TREE.  */
 126
 127 tree
 128 maybe_get_identifier (const char *text)
 129 {
 130   hashnode ht_node;
 131
 132   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 133                        strlen (text), HT_NO_INSERT);
 134   if (ht_node)
 135     return HT_IDENT_TO_GCC_IDENT (ht_node);
 136
 137   return NULL_TREE;
 138 }
 139
 140 /* Report some basic statistics about the string pool.  */
 141
 142 void
 143 stringpool_statistics (void)
 144 {
 145   ht_dump_statistics (ident_hash);
 146 }
 147
 148 /* Mark an identifier for GC.  */
 149
 150 static int
 151 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 152             const void *v ATTRIBUTE_UNUSED)
 153 {
 154   gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
 155   return 1;
 156 }
 157
 158 /* Mark the trees hanging off the identifier node for GGC.  These are
 159    handled specially (not using gengtype) because of the special
 160    treatment for strings.  */
 161
 162 void
 163 ggc_mark_stringpool (void)
 164 {
 165   ht_forall (ident_hash, mark_ident, NULL);
 166 }
 167
 168 /* Strings are _not_ GCed, but this routine exists so that a separate
 169    roots table isn't needed for the few global variables that refer
 170    to strings.  */
 171
 172 void
 173 gt_ggc_m_S (void *x ATTRIBUTE_UNUSED)
 174 {
 175 }
 176
 177 /* Pointer-walking routine for strings (not very interesting, since
 178    strings don't contain pointers).  */
 179
 180 void
 181 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 182             gt_pointer_operator op ATTRIBUTE_UNUSED,
 183             void *cookie ATTRIBUTE_UNUSED)
 184 {
 185 }
 186
 187 /* PCH pointer-walking routine for strings.  */
 188
 189 void
 190 gt_pch_n_S (const void *x)
 191 {
 192   gt_pch_note_object ((void *)x, (void *)x, &gt_pch_p_S);
 193 }
 194
 195 /* Handle saving and restoring the string pool for PCH.  */
 196
 197 struct string_pool_data GTY(())
 198 {
 199   tree * GTY((length ("%h.nslots"))) entries;
 200   unsigned int nslots;
 201   unsigned int nelements;
 202 };
 203
 204 static GTY(()) struct string_pool_data * spd;
 205
 206 static int
 207 ht_copy_and_clear (cpp_reader *r ATTRIBUTE_UNUSED, hashnode hp, const void *ht2_p)
 208 {
 209   cpp_hashnode *h = CPP_HASHNODE (hp);
 210   struct ht *ht2 = (struct ht *) ht2_p;
 211
 212   if (h->type != NT_VOID
 213       && (h->flags & NODE_BUILTIN) == 0)
 214     {
 215       cpp_hashnode *h2 = CPP_HASHNODE (ht_lookup (ht2,
 216                                                   NODE_NAME (h),
 217                                                   NODE_LEN (h),
 218                                                   HT_ALLOC));
 219       h2->type = h->type;
 220       memcpy (&h2->value, &h->value, sizeof (h->value));
 221
 222       h->type = NT_VOID;
 223       memset (&h->value, 0, sizeof (h->value));
 224     }
 225   return 1;
 226 }
 227
 228 static struct ht *saved_ident_hash;
 229
 230 void
 231 gt_pch_save_stringpool (void)
 232 {
 233   unsigned int i;
 234
 235   spd = ggc_alloc (sizeof (*spd));
 236   spd->nslots = ident_hash->nslots;
 237   spd->nelements = ident_hash->nelements;
 238   spd->entries = ggc_alloc (sizeof (tree *) * spd->nslots);
 239   for (i = 0; i < spd->nslots; i++)
 240     if (ident_hash->entries[i] != NULL)
 241       spd->entries[i] = HT_IDENT_TO_GCC_IDENT (ident_hash->entries[i]);
 242     else
 243       spd->entries[i] = NULL;
 244
 245   saved_ident_hash = ht_create (14);
 246   saved_ident_hash->alloc_node = alloc_node;
 247   ht_forall (ident_hash, ht_copy_and_clear, saved_ident_hash);
 248 }
 249
 250 void
 251 gt_pch_fixup_stringpool (void)
 252 {
 253   ht_forall (saved_ident_hash, ht_copy_and_clear, ident_hash);
 254   ht_destroy (saved_ident_hash);
 255   saved_ident_hash = 0;
 256 }
 257
 258 void
 259 gt_pch_restore_stringpool (void)
 260 {
 261   unsigned int i;
 262
 263   ident_hash->nslots = spd->nslots;
 264   ident_hash->nelements = spd->nelements;
 265   ident_hash->entries = xrealloc (ident_hash->entries,
 266                                   sizeof (hashnode) * spd->nslots);
 267   for (i = 0; i < spd->nslots; i++)
 268     if (spd->entries[i] != NULL)
 269       ident_hash->entries[i] = GCC_IDENT_TO_HT_IDENT (spd->entries[i]);
 270     else
 271       ident_hash->entries[i] = NULL;
 272
 273   spd = NULL;
 274 }
 275
 276 #include "gt-stringpool.h"