gcc/stringpool.c

   1 /* String pool for GCC.
   2    Copyright (C) 2000, 2001 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
  38 /* The "" allocated string.  */
  39 const char empty_string[] = "";
  40
  41 /* Character strings, each containing a single decimal digit.
  42    Written this way to save space.  */
  43 const char digit_vector[] = {
  44   '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
  45   '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
  46 };
  47
  48 struct ht *ident_hash;
  49 static struct obstack string_stack;
  50
  51 static hashnode alloc_node PARAMS ((hash_table *));
  52 static int mark_ident PARAMS ((struct cpp_reader *, hashnode, const PTR));
  53 static void mark_ident_hash PARAMS ((void *));
  54
  55 /* Initialize the string pool.  */
  56 void
  57 init_stringpool ()
  58 {
  59   /* Create with 16K (2^14) entries.  */
  60   ident_hash = ht_create (14);
  61   ident_hash->alloc_node = alloc_node;
  62   gcc_obstack_init (&string_stack);
  63   ggc_add_root (&ident_hash, 1, sizeof ident_hash, mark_ident_hash);
  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   ggc_mark_tree (HT_IDENT_TO_GCC_IDENT (h));
 164   return 1;
 165 }
 166
 167 /* Mark all identifiers for GC.  */
 168
 169 static void
 170 mark_ident_hash (arg)
 171      PTR arg ATTRIBUTE_UNUSED;
 172 {
 173   ht_forall (ident_hash, mark_ident, NULL);
 174 }