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 #undef get_identifier
  99
 100 tree
 101 get_identifier (const char *text)
 102 {
 103   hashnode ht_node = ht_lookup (ident_hash,
 104                                 (const unsigned char *) text,
 105                                 strlen (text), HT_ALLOC);
 106
 107   /* ht_node can't be NULL here.  */
 108   return HT_IDENT_TO_GCC_IDENT (ht_node);
 109 }
 110
 111 /* Identical to get_identifier, except that the length is assumed
 112    known.  */
 113
 114 tree
 115 get_identifier_with_length (const char *text, size_t length)
 116 {
 117   hashnode ht_node = ht_lookup (ident_hash,
 118                                 (const unsigned char *) text,
 119                                 length, HT_ALLOC);
 120
 121   /* ht_node can't be NULL here.  */
 122   return HT_IDENT_TO_GCC_IDENT (ht_node);
 123 }
 124
 125 /* If an identifier with the name TEXT (a null-terminated string) has
 126    previously been referred to, return that node; otherwise return
 127    NULL_TREE.  */
 128
 129 tree
 130 maybe_get_identifier (const char *text)
 131 {
 132   hashnode ht_node;
 133
 134   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 135                        strlen (text), HT_NO_INSERT);
 136   if (ht_node)
 137     return HT_IDENT_TO_GCC_IDENT (ht_node);
 138
 139   return NULL_TREE;
 140 }
 141
 142 /* Report some basic statistics about the string pool.  */
 143
 144 void
 145 stringpool_statistics (void)
 146 {
 147   ht_dump_statistics (ident_hash);
 148 }
 149
 150 /* Mark an identifier for GC.  */
 151
 152 static int
 153 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 154             const void *v ATTRIBUTE_UNUSED)
 155 {
 156   gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
 157   return 1;
 158 }
 159
 160 /* Mark the trees hanging off the identifier node for GGC.  These are
 161    handled specially (not using gengtype) because of the special
 162    treatment for strings.  */
 163
 164 void
 165 ggc_mark_stringpool (void)
 166 {
 167   ht_forall (ident_hash, mark_ident, NULL);
 168 }
 169
 170 /* Strings are _not_ GCed, but this routine exists so that a separate
 171    roots table isn't needed for the few global variables that refer
 172    to strings.  */
 173
 174 void
 175 gt_ggc_m_S (void *x ATTRIBUTE_UNUSED)
 176 {
 177 }
 178
 179 /* Pointer-walking routine for strings (not very interesting, since
 180    strings don't contain pointers).  */
 181
 182 void
 183 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 184             gt_pointer_operator op ATTRIBUTE_UNUSED,
 185             void *cookie ATTRIBUTE_UNUSED)
 186 {
 187 }
 188
 189 /* PCH pointer-walking routine for strings.  */
 190
 191 void
 192 gt_pch_n_S (const void *x)
 193 {
 194   gt_pch_note_object ((void *)x, (void *)x, &gt_pch_p_S);
 195 }
 196
 197 /* Handle saving and restoring the string pool for PCH.  */
 198
 199 struct string_pool_data GTY(())
 200 {
 201   tree * GTY((length ("%h.nslots"))) entries;
 202   unsigned int nslots;
 203   unsigned int nelements;
 204 };
 205
 206 static GTY(()) struct string_pool_data * spd;
 207
 208 static int
 209 ht_copy_and_clear (cpp_reader *r ATTRIBUTE_UNUSED, hashnode hp, const void *ht2_p)
 210 {
 211   cpp_hashnode *h = CPP_HASHNODE (hp);
 212   struct ht *ht2 = (struct ht *) ht2_p;
 213
 214   if (h->type != NT_VOID
 215       && (h->flags & NODE_BUILTIN) == 0)
 216     {
 217       cpp_hashnode *h2 = CPP_HASHNODE (ht_lookup (ht2,
 218                                                   NODE_NAME (h),
 219                                                   NODE_LEN (h),
 220                                                   HT_ALLOC));
 221       h2->type = h->type;
 222       memcpy (&h2->value, &h->value, sizeof (h->value));
 223
 224       h->type = NT_VOID;
 225       memset (&h->value, 0, sizeof (h->value));
 226     }
 227   return 1;
 228 }
 229
 230 static struct ht *saved_ident_hash;
 231
 232 void
 233 gt_pch_save_stringpool (void)
 234 {
 235   unsigned int i;
 236
 237   spd = ggc_alloc (sizeof (*spd));
 238   spd->nslots = ident_hash->nslots;
 239   spd->nelements = ident_hash->nelements;
 240   spd->entries = ggc_alloc (sizeof (tree *) * spd->nslots);
 241   for (i = 0; i < spd->nslots; i++)
 242     if (ident_hash->entries[i] != NULL)
 243       spd->entries[i] = HT_IDENT_TO_GCC_IDENT (ident_hash->entries[i]);
 244     else
 245       spd->entries[i] = NULL;
 246
 247   saved_ident_hash = ht_create (14);
 248   saved_ident_hash->alloc_node = alloc_node;
 249   ht_forall (ident_hash, ht_copy_and_clear, saved_ident_hash);
 250 }
 251
 252 void
 253 gt_pch_fixup_stringpool (void)
 254 {
 255   ht_forall (saved_ident_hash, ht_copy_and_clear, ident_hash);
 256   ht_destroy (saved_ident_hash);
 257   saved_ident_hash = 0;
 258 }
 259
 260 void
 261 gt_pch_restore_stringpool (void)
 262 {
 263   unsigned int i;
 264
 265   ident_hash->nslots = spd->nslots;
 266   ident_hash->nelements = spd->nelements;
 267   ident_hash->entries = xrealloc (ident_hash->entries,
 268                                   sizeof (hashnode) * spd->nslots);
 269   for (i = 0; i < spd->nslots; i++)
 270     if (spd->entries[i] != NULL)
 271       ident_hash->entries[i] = GCC_IDENT_TO_HT_IDENT (spd->entries[i]);
 272     else
 273       ident_hash->entries[i] = NULL;
 274
 275   spd = NULL;
 276 }
 277
 278 #include "gt-stringpool.h"