gcc/memory-block.h

   1 /* Shared pool of memory blocks for pool allocators.
   2    Copyright (C) 2015-2019 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   VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS ((char *)uncast_block
  73                                                 + sizeof (block_list),
  74                                                 block_size
  75                                                 - sizeof (block_list)));
  76 }
  77
  78 extern void *mempool_obstack_chunk_alloc (size_t) ATTRIBUTE_MALLOC;
  79 extern void mempool_obstack_chunk_free (void *);
  80
  81 #endif /* MEMORY_BLOCK_H */