1 /* Shared pool of memory blocks for pool allocators.
2    Copyright (C) 2015-2018 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
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10 
11 GCC is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 GNU General Public License for more details.
15 
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3.  If not see
18 <http://www.gnu.org/licenses/>.  */
19 
20 
21 #ifndef MEMORY_BLOCK_H
22 #define MEMORY_BLOCK_H
23 
24 /* Shared pool which allows other memory pools to reuse each others' allocated
25    memory blocks instead of calling free/malloc again.  */
26 class memory_block_pool
27 {
28 public:
29   /* Blocks have fixed size.  This is necessary for sharing.  */
30   static const size_t block_size = 64 * 1024;
31 
32   memory_block_pool ();
33 
34   static inline void *allocate () ATTRIBUTE_MALLOC;
35   static inline void release (void *);
36   void clear_free_list ();
37 
38 private:
39   /* memory_block_pool singleton instance, defined in memory-block.cc.  */
40   static memory_block_pool instance;
41 
42   struct block_list
43   {
44     block_list *m_next;
45   };
46 
47   /* Free list.  */
48   block_list *m_blocks;
49 };
50 
51 /* Allocate a single block.  Reuse a previously returned block, if possible.  */
52 inline void *
53 memory_block_pool::allocate ()
54 {
55   if (instance.m_blocks == NULL)
56     return XNEWVEC (char, block_size);
57 
58   void *result = instance.m_blocks;
59   instance.m_blocks = instance.m_blocks->m_next;
60   VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (result, block_size));
61   return result;
62 }
63 
64 /* Return UNCAST_BLOCK to the pool.  */
65 inline void
66 memory_block_pool::release (void *uncast_block)
67 {
68   block_list *block = new (uncast_block) block_list;
69   block->m_next = instance.m_blocks;
70   instance.m_blocks = block;
71 }
72 
73 extern void *mempool_obstack_chunk_alloc (size_t) ATTRIBUTE_MALLOC;
74 extern void mempool_obstack_chunk_free (void *);
75 
76 #endif /* MEMORY_BLOCK_H */
77