gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000, 2001, 2002 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 PARAMS ((hash_table *));
  53 static int mark_ident PARAMS ((struct cpp_reader *, hashnode, const PTR));
  54 static int ht_copy_and_clear PARAMS ((struct cpp_reader *, hashnode, const void *));
  55
  56 /* Initialize the string pool.  */
  57 void
  58 init_stringpool ()
  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 (table)
  69      hash_table *table ATTRIBUTE_UNUSED;
  70 {
  71   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  72 }
  73
  74 /* Allocate and return a string constant of length LENGTH, containing
  75    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  76    nul-terminated string, and the length is calculated using strlen.
  77    If the same string constant has been allocated before, that copy is
  78    returned this time too.  */
  79
  80 const char *
  81 ggc_alloc_string (contents, length)
  82      const char *contents;
  83      int length;
  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   obstack_grow0 (&string_stack, contents, length);
  94   return obstack_finish (&string_stack);
  95 }
  96
  97 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
  98    If an identifier with that name has previously been referred to,
  99    the same node is returned this time.  */
 100
 101 tree
 102 get_identifier (text)
 103      const char *text;
 104 {
 105   hashnode ht_node = ht_lookup (ident_hash,
 106                                 (const unsigned char *) text,
 107                                 strlen (text), HT_ALLOC);
 108
 109   /* ht_node can't be NULL here.  */
 110   return HT_IDENT_TO_GCC_IDENT (ht_node);
 111 }
 112
 113 /* Identical to get_identifier, except that the length is assumed
 114    known.  */
 115
 116 tree
 117 get_identifier_with_length (text, length)
 118      const char *text;
 119      unsigned int length;
 120 {
 121   hashnode ht_node = ht_lookup (ident_hash,
 122                                 (const unsigned char *) text,
 123                                 length, HT_ALLOC);
 124
 125   /* ht_node can't be NULL here.  */
 126   return HT_IDENT_TO_GCC_IDENT (ht_node);
 127 }
 128
 129 /* If an identifier with the name TEXT (a null-terminated string) has
 130    previously been referred to, return that node; otherwise return
 131    NULL_TREE.  */
 132
 133 tree
 134 maybe_get_identifier (text)
 135      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 ()
 151 {
 152   ht_dump_statistics (ident_hash);
 153 }
 154
 155 /* Mark an identifier for GC.  */
 156
 157 static int
 158 mark_ident (pfile, h, v)
 159      struct cpp_reader *pfile ATTRIBUTE_UNUSED;
 160      hashnode h;
 161      const PTR 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 ()
 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 (x)
 183      void *x ATTRIBUTE_UNUSED;
 184 {
 185 }
 186
 187 /* Pointer-walking routine for strings (not very interesting, since
 188    strings don't contain pointers).  */
 189
 190 void
 191 gt_pch_p_S (obj, x, op, cookie)
 192      void *obj ATTRIBUTE_UNUSED;
 193      void *x ATTRIBUTE_UNUSED;
 194      gt_pointer_operator op ATTRIBUTE_UNUSED;
 195      void *cookie ATTRIBUTE_UNUSED;
 196 {
 197 }
 198
 199 /* PCH pointer-walking routine for strings.  */
 200
 201 void
 202 gt_pch_n_S (x)
 203      const void *x;
 204 {
 205   gt_pch_note_object ((void *)x, (void *)x, &gt_pch_p_S);
 206 }
 207
 208 /* Handle saving and restoring the string pool for PCH.  */
 209
 210 struct string_pool_data GTY(())
 211 {
 212   tree * GTY((length ("%h.nslots"))) entries;
 213   unsigned int nslots;
 214   unsigned int nelements;
 215 };
 216
 217 static GTY(()) struct string_pool_data * spd;
 218
 219 static int
 220 ht_copy_and_clear (r, hp, ht2_p)
 221      cpp_reader *r ATTRIBUTE_UNUSED;
 222      hashnode hp;
 223      const void *ht2_p;
 224 {
 225   cpp_hashnode *h = CPP_HASHNODE (hp);
 226   struct ht *ht2 = (struct ht *) ht2_p;
 227
 228   if (h->type != NT_VOID
 229       && (h->flags & NODE_BUILTIN) == 0)
 230     {
 231       cpp_hashnode *h2 = CPP_HASHNODE (ht_lookup (ht2,
 232                                                   NODE_NAME (h),
 233                                                   NODE_LEN (h),
 234                                                   HT_ALLOC));
 235       h2->type = h->type;
 236       memcpy (&h2->value, &h->value, sizeof (h->value));
 237
 238       h->type = NT_VOID;
 239       memset (&h->value, 0, sizeof (h->value));
 240     }
 241   return 1;
 242 }
 243
 244 static struct ht *saved_ident_hash;
 245
 246 void
 247 gt_pch_save_stringpool ()
 248 {
 249   unsigned int i;
 250
 251   spd = ggc_alloc (sizeof (*spd));
 252   spd->nslots = ident_hash->nslots;
 253   spd->nelements = ident_hash->nelements;
 254   spd->entries = ggc_alloc (sizeof (tree *) * spd->nslots);
 255   for (i = 0; i < spd->nslots; i++)
 256     if (ident_hash->entries[i] != NULL)
 257       spd->entries[i] = HT_IDENT_TO_GCC_IDENT (ident_hash->entries[i]);
 258     else
 259       spd->entries[i] = NULL;
 260
 261   saved_ident_hash = ht_create (14);
 262   saved_ident_hash->alloc_node = alloc_node;
 263   ht_forall (ident_hash, ht_copy_and_clear, saved_ident_hash);
 264 }
 265
 266 void
 267 gt_pch_fixup_stringpool ()
 268 {
 269   ht_forall (saved_ident_hash, ht_copy_and_clear, ident_hash);
 270   ht_destroy (saved_ident_hash);
 271   saved_ident_hash = 0;
 272 }
 273
 274 void
 275 gt_pch_restore_stringpool ()
 276 {
 277   unsigned int i;
 278
 279   ident_hash->nslots = spd->nslots;
 280   ident_hash->nelements = spd->nelements;
 281   ident_hash->entries = xrealloc (ident_hash->entries,
 282                                   sizeof (hashnode) * spd->nslots);
 283   for (i = 0; i < spd->nslots; i++)
 284     if (spd->entries[i] != NULL)
 285       ident_hash->entries[i] = GCC_IDENT_TO_HT_IDENT (spd->entries[i]);
 286     else
 287       ident_hash->entries[i] = NULL;
 288
 289   spd = NULL;
 290 }
 291
 292 #include "gt-stringpool.h"