gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007
   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.  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 use cpplib's 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 "symtab.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
  55 static void *
  56 stringpool_ggc_alloc (size_t x)
  57 {
  58   return ggc_alloc (x);
  59 }
  60
  61 /* Initialize the string pool.  */
  62 void
  63 init_stringpool (void)
  64 {
  65   /* Create with 16K (2^14) entries.  */
  66   ident_hash = ht_create (14);
  67   ident_hash->alloc_node = alloc_node;
  68   ident_hash->alloc_subobject = stringpool_ggc_alloc;
  69   gcc_obstack_init (&string_stack);
  70 }
  71
  72 /* Allocate a hash node.  */
  73 static hashnode
  74 alloc_node (hash_table *table ATTRIBUTE_UNUSED)
  75 {
  76   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  77 }
  78
  79 /* Allocate and return a string constant of length LENGTH, containing
  80    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  81    nul-terminated string, and the length is calculated using strlen.
  82    If the same string constant has been allocated before, that copy is
  83    returned this time too.  */
  84
  85 const char *
  86 ggc_alloc_string (const char *contents, int length)
  87 {
  88   if (length == -1)
  89     length = strlen (contents);
  90
  91   if (length == 0)
  92     return empty_string;
  93   if (length == 1 && ISDIGIT (contents[0]))
  94     return digit_string (contents[0] - '0');
  95
  96   obstack_grow0 (&string_stack, contents, length);
  97   return XOBFINISH (&string_stack, const char *);
  98 }
  99
 100 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
 101    If an identifier with that name has previously been referred to,
 102    the same node is returned this time.  */
 103
 104 #undef get_identifier
 105
 106 tree
 107 get_identifier (const char *text)
 108 {
 109   hashnode ht_node = ht_lookup (ident_hash,
 110                                 (const unsigned char *) text,
 111                                 strlen (text), HT_ALLOC);
 112
 113   /* ht_node can't be NULL here.  */
 114   return HT_IDENT_TO_GCC_IDENT (ht_node);
 115 }
 116
 117 /* Identical to get_identifier, except that the length is assumed
 118    known.  */
 119
 120 tree
 121 get_identifier_with_length (const char *text, size_t length)
 122 {
 123   hashnode ht_node = ht_lookup (ident_hash,
 124                                 (const unsigned char *) text,
 125                                 length, HT_ALLOC);
 126
 127   /* ht_node can't be NULL here.  */
 128   return HT_IDENT_TO_GCC_IDENT (ht_node);
 129 }
 130
 131 /* If an identifier with the name TEXT (a null-terminated string) has
 132    previously been referred to, return that node; otherwise return
 133    NULL_TREE.  */
 134
 135 tree
 136 maybe_get_identifier (const char *text)
 137 {
 138   hashnode ht_node;
 139
 140   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 141                        strlen (text), HT_NO_INSERT);
 142   if (ht_node)
 143     return HT_IDENT_TO_GCC_IDENT (ht_node);
 144
 145   return NULL_TREE;
 146 }
 147
 148 /* Report some basic statistics about the string pool.  */
 149
 150 void
 151 stringpool_statistics (void)
 152 {
 153   ht_dump_statistics (ident_hash);
 154 }
 155 \f
 156 /* Mark an identifier for GC.  */
 157
 158 static int
 159 mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
 160             const void *v ATTRIBUTE_UNUSED)
 161 {
 162   gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
 163   return 1;
 164 }
 165
 166 /* Mark the trees hanging off the identifier node for GGC.  These are
 167    handled specially (not using gengtype) because of the special
 168    treatment for strings.  */
 169
 170 void
 171 ggc_mark_stringpool (void)
 172 {
 173   ht_forall (ident_hash, mark_ident, NULL);
 174 }
 175
 176 /* Strings are _not_ GCed, but this routine exists so that a separate
 177    roots table isn't needed for the few global variables that refer
 178    to strings.  */
 179
 180 void
 181 gt_ggc_m_S (void *x ATTRIBUTE_UNUSED)
 182 {
 183 }
 184
 185 /* Pointer-walking routine for strings (not very interesting, since
 186    strings don't contain pointers).  */
 187
 188 void
 189 gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
 190             gt_pointer_operator op ATTRIBUTE_UNUSED,
 191             void *cookie ATTRIBUTE_UNUSED)
 192 {
 193 }
 194
 195 /* PCH pointer-walking routine for strings.  */
 196
 197 void
 198 gt_pch_n_S (const void *x)
 199 {
 200   gt_pch_note_object ((void *)x, (void *)x, &gt_pch_p_S,
 201                       gt_types_enum_last);
 202 }
 203 \f
 204 /* Handle saving and restoring the string pool for PCH.  */
 205
 206 /* SPD is saved in the PCH file and holds the information needed
 207    to restore the string pool.  */
 208
 209 struct string_pool_data GTY(())
 210 {
 211   struct ht_identifier * *
 212     GTY((length ("%h.nslots"),
 213          nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
 214                      "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
 215     entries;
 216   unsigned int nslots;
 217   unsigned int nelements;
 218 };
 219
 220 static GTY(()) struct string_pool_data * spd;
 221
 222 /* Save the stringpool data in SPD.  */
 223
 224 void
 225 gt_pch_save_stringpool (void)
 226 {
 227   spd = ggc_alloc (sizeof (*spd));
 228   spd->nslots = ident_hash->nslots;
 229   spd->nelements = ident_hash->nelements;
 230   spd->entries = ggc_alloc (sizeof (spd->entries[0]) * spd->nslots);
 231   memcpy (spd->entries, ident_hash->entries,
 232           spd->nslots * sizeof (spd->entries[0]));
 233 }
 234
 235 /* Return the stringpool to its state before gt_pch_save_stringpool
 236    was called.  */
 237
 238 void
 239 gt_pch_fixup_stringpool (void)
 240 {
 241 }
 242
 243 /* A PCH file has been restored, which loaded SPD; fill the real hash table
 244    from SPD.  */
 245
 246 void
 247 gt_pch_restore_stringpool (void)
 248 {
 249   ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
 250   spd = NULL;
 251 }
 252
 253 #include "gt-stringpool.h"