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 "ggc.h"
  33 #include "tree.h"
  34 #include "hashtable.h"
  35
  36 /* The "" allocated string.  */
  37 const char empty_string[] = "";
  38
  39 /* Character strings, each containing a single decimal digit.
  40    Written this way to save space.  */
  41 const char digit_vector[] = {
  42   '0', 0, '1', 0, '2', 0, '3', 0, '4', 0,
  43   '5', 0, '6', 0, '7', 0, '8', 0, '9', 0
  44 };
  45
  46 struct ht *ident_hash;
  47 static struct obstack string_stack;
  48
  49 static hashnode alloc_node PARAMS ((hash_table *));
  50 static int mark_ident PARAMS ((struct cpp_reader *, hashnode, const PTR));
  51 static void mark_ident_hash PARAMS ((void *));
  52
  53 /* Initialize the string pool.  */
  54 void
  55 init_stringpool ()
  56 {
  57   /* Create with 16K (2^14) entries.  */
  58   ident_hash = ht_create (14);
  59   ident_hash->alloc_node = alloc_node;
  60   gcc_obstack_init (&string_stack);
  61   ggc_add_root (&ident_hash, 1, sizeof ident_hash, mark_ident_hash);
  62 }
  63
  64 /* Allocate a hash node.  */
  65 static hashnode
  66 alloc_node (table)
  67      hash_table *table ATTRIBUTE_UNUSED;
  68 {
  69   return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
  70 }
  71
  72 /* Allocate and return a string constant of length LENGTH, containing
  73    CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
  74    nul-terminated string, and the length is calculated using strlen.
  75    If the same string constant has been allocated before, that copy is
  76    returned this time too.  */
  77
  78 const char *
  79 ggc_alloc_string (contents, length)
  80      const char *contents;
  81      int length;
  82 {
  83   if (length == -1)
  84     length = strlen (contents);
  85
  86   if (length == 0)
  87     return empty_string;
  88   if (length == 1 && ISDIGIT (contents[0]))
  89     return digit_string (contents[0] - '0');
  90
  91   obstack_grow0 (&string_stack, contents, length);
  92   return obstack_finish (&string_stack);
  93 }
  94
  95 /* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
  96    If an identifier with that name has previously been referred to,
  97    the same node is returned this time.  */
  98
  99 tree
 100 get_identifier (text)
 101      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 (text, length)
 116      const char *text;
 117      unsigned int length;
 118 {
 119   hashnode ht_node = ht_lookup (ident_hash,
 120                                 (const unsigned char *) text,
 121                                 length, HT_ALLOC);
 122
 123   /* ht_node can't be NULL here.  */
 124   return HT_IDENT_TO_GCC_IDENT (ht_node);
 125 }
 126
 127 /* If an identifier with the name TEXT (a null-terminated string) has
 128    previously been referred to, return that node; otherwise return
 129    NULL_TREE.  */
 130
 131 tree
 132 maybe_get_identifier (text)
 133      const char *text;
 134 {
 135   hashnode ht_node;
 136
 137   ht_node = ht_lookup (ident_hash, (const unsigned char *) text,
 138                        strlen (text), HT_NO_INSERT);
 139   if (ht_node)
 140     return HT_IDENT_TO_GCC_IDENT (ht_node);
 141
 142   return NULL_TREE;
 143 }
 144
 145 /* Report some basic statistics about the string pool.  */
 146
 147 void
 148 stringpool_statistics ()
 149 {
 150   ht_dump_statistics (ident_hash);
 151 }
 152
 153 /* Mark an identifier for GC.  */
 154
 155 static int
 156 mark_ident (pfile, h, v)
 157      struct cpp_reader *pfile ATTRIBUTE_UNUSED;
 158      hashnode h;
 159      const PTR v ATTRIBUTE_UNUSED;
 160 {
 161   ggc_mark_nonnull_tree (HT_IDENT_TO_GCC_IDENT (h));
 162   return 1;
 163 }
 164
 165 /* Mark all identifiers for GC.  */
 166
 167 static void
 168 mark_ident_hash (arg)
 169      PTR arg ATTRIBUTE_UNUSED;
 170 {
 171   ht_forall (ident_hash, mark_ident, NULL);
 172 }