1/* String pool for GCC.
2   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008
3   Free Software Foundation, Inc.
4
5This file is part of GCC.
6
7GCC is free software; you can redistribute it and/or modify it under
8the terms of the GNU General Public License as published by the Free
9Software Foundation; either version 3, or (at your option) any later
10version.
11
12GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13WARRANTY; without even the implied warranty of MERCHANTABILITY or
14FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15for more details.
16
17You should have received a copy of the GNU General Public License
18along 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.
22   Identifiers are uniquely stored in a hash table.
23
24   We use cpplib's hash table implementation.  libiberty's
25   hashtab.c is not used because it requires 100% average space
26   overhead per string, which is unacceptable.  Also, this algorithm
27   is faster.  */
28
29#include "config.h"
30#include "system.h"
31#include "coretypes.h"
32#include "tm.h"
33#include "ggc.h"
34#include "tree.h"
35#include "symtab.h"
36#include "cpplib.h"
37
38/* The "" allocated string.  */
39const char empty_string[] = "";
40
41/* Character strings, each containing a single decimal digit.
42   Written this way to save space.  */
43const 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
48struct ht *ident_hash;
49
50static hashnode alloc_node (hash_table *);
51static int mark_ident (struct cpp_reader *, hashnode, const void *);
52
53static void *
54stringpool_ggc_alloc (size_t x)
55{
56  return ggc_alloc (x);
57}
58
59/* Initialize the string pool.  */
60void
61init_stringpool (void)
62{
63  /* Create with 16K (2^14) entries.  */
64  ident_hash = ht_create (14);
65  ident_hash->alloc_node = alloc_node;
66  ident_hash->alloc_subobject = stringpool_ggc_alloc;
67}
68
69/* Allocate a hash node.  */
70static hashnode
71alloc_node (hash_table *table ATTRIBUTE_UNUSED)
72{
73  return GCC_IDENT_TO_HT_IDENT (make_node (IDENTIFIER_NODE));
74}
75
76/* Allocate and return a string constant of length LENGTH, containing
77   CONTENTS.  If LENGTH is -1, CONTENTS is assumed to be a
78   nul-terminated string, and the length is calculated using strlen.  */
79
80const char *
81ggc_alloc_string (const char *contents, int length)
82{
83  char *result;
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  result = GGC_NEWVAR (char, length + 1);
94  memcpy (result, contents, length);
95  result[length] = '\0';
96  return (const char *) result;
97}
98
99/* Return an IDENTIFIER_NODE whose name is TEXT (a null-terminated string).
100   If an identifier with that name has previously been referred to,
101   the same node is returned this time.  */
102
103#undef get_identifier
104
105tree
106get_identifier (const char *text)
107{
108  hashnode ht_node = ht_lookup (ident_hash,
109				(const unsigned char *) text,
110				strlen (text), HT_ALLOC);
111
112  /* ht_node can't be NULL here.  */
113  return HT_IDENT_TO_GCC_IDENT (ht_node);
114}
115
116/* Identical to get_identifier, except that the length is assumed
117   known.  */
118
119tree
120get_identifier_with_length (const char *text, size_t length)
121{
122  hashnode ht_node = ht_lookup (ident_hash,
123				(const unsigned char *) text,
124				length, HT_ALLOC);
125
126  /* ht_node can't be NULL here.  */
127  return HT_IDENT_TO_GCC_IDENT (ht_node);
128}
129
130/* If an identifier with the name TEXT (a null-terminated string) has
131   previously been referred to, return that node; otherwise return
132   NULL_TREE.  */
133
134tree
135maybe_get_identifier (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
149void
150stringpool_statistics (void)
151{
152  ht_dump_statistics (ident_hash);
153}
154
155/* Mark an identifier for GC.  */
156
157static int
158mark_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
159	    const void *v ATTRIBUTE_UNUSED)
160{
161  gt_ggc_m_9tree_node (HT_IDENT_TO_GCC_IDENT (h));
162  return 1;
163}
164
165/* Return true if an identifier should be removed from the table.  */
166
167static int
168maybe_delete_ident (struct cpp_reader *pfile ATTRIBUTE_UNUSED, hashnode h,
169		    const void *v ATTRIBUTE_UNUSED)
170{
171  return !ggc_marked_p (HT_IDENT_TO_GCC_IDENT (h));
172}
173
174/* Mark the trees hanging off the identifier node for GGC.  These are
175   handled specially (not using gengtype) because identifiers are only
176   roots during one part of compilation.  */
177
178void
179ggc_mark_stringpool (void)
180{
181  ht_forall (ident_hash, mark_ident, NULL);
182}
183
184/* Purge the identifier hash of identifiers which are no longer
185   referenced.  */
186
187void
188ggc_purge_stringpool (void)
189{
190  ht_purge (ident_hash, maybe_delete_ident, NULL);
191}
192
193/* Pointer-walking routine for strings (not very interesting, since
194   strings don't contain pointers).  */
195
196void
197gt_pch_p_S (void *obj ATTRIBUTE_UNUSED, void *x ATTRIBUTE_UNUSED,
198	    gt_pointer_operator op ATTRIBUTE_UNUSED,
199	    void *cookie ATTRIBUTE_UNUSED)
200{
201}
202
203/* PCH pointer-walking routine for strings.  */
204
205void
206gt_pch_n_S (const void *x)
207{
208  gt_pch_note_object (CONST_CAST (void *, x), CONST_CAST (void *, x),
209		      &gt_pch_p_S, gt_types_enum_last);
210}
211
212/* Handle saving and restoring the string pool for PCH.  */
213
214/* SPD is saved in the PCH file and holds the information needed
215   to restore the string pool.  */
216
217struct GTY(()) string_pool_data {
218  struct ht_identifier * *
219    GTY((length ("%h.nslots"),
220	 nested_ptr (union tree_node, "%h ? GCC_IDENT_TO_HT_IDENT (%h) : NULL",
221		     "%h ? HT_IDENT_TO_GCC_IDENT (%h) : NULL")))
222    entries;
223  unsigned int nslots;
224  unsigned int nelements;
225};
226
227static GTY(()) struct string_pool_data * spd;
228
229/* Save the stringpool data in SPD.  */
230
231void
232gt_pch_save_stringpool (void)
233{
234  spd = GGC_NEW (struct string_pool_data);
235  spd->nslots = ident_hash->nslots;
236  spd->nelements = ident_hash->nelements;
237  spd->entries = GGC_NEWVEC (struct ht_identifier *, spd->nslots);
238  memcpy (spd->entries, ident_hash->entries,
239	  spd->nslots * sizeof (spd->entries[0]));
240}
241
242/* Return the stringpool to its state before gt_pch_save_stringpool
243   was called.  */
244
245void
246gt_pch_fixup_stringpool (void)
247{
248}
249
250/* A PCH file has been restored, which loaded SPD; fill the real hash table
251   from SPD.  */
252
253void
254gt_pch_restore_stringpool (void)
255{
256  ht_load (ident_hash, spd->entries, spd->nslots, spd->nelements, false);
257  spd = NULL;
258}
259
260#include "gt-stringpool.h"
261