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1 /* Shared pool of memory blocks for pool allocators.
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145
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2 Copyright (C) 2015-2020 Free Software Foundation, Inc.
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3
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4 This file is part of GCC.
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5
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6 GCC is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3, or (at your option)
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9 any later version.
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10
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11 GCC is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with GCC; see the file COPYING3. If not see
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18 <http://www.gnu.org/licenses/>. */
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19
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20
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21 #ifndef MEMORY_BLOCK_H
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22 #define MEMORY_BLOCK_H
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23
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24 /* Shared pool which allows other memory pools to reuse each others' allocated
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25 memory blocks instead of calling free/malloc again. */
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26 class memory_block_pool
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27 {
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28 public:
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29 /* Blocks have fixed size. This is necessary for sharing. */
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30 static const size_t block_size = 64 * 1024;
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31 /* Number of blocks we keep in the freelists. */
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32 static const size_t freelist_size = 1024 * 1024 / block_size;
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33
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34 memory_block_pool ();
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35
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36 static inline void *allocate () ATTRIBUTE_MALLOC;
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37 static inline void release (void *);
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38 static void trim (int nblocks = freelist_size);
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39 void reduce_free_list (int);
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40
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41 private:
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42 /* memory_block_pool singleton instance, defined in memory-block.cc. */
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43 static memory_block_pool instance;
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44
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45 struct block_list
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46 {
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47 block_list *m_next;
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48 };
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49
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50 /* Free list. */
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51 block_list *m_blocks;
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52 };
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53
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54 /* Allocate a single block. Reuse a previously returned block, if possible. */
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55 inline void *
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56 memory_block_pool::allocate ()
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57 {
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58 if (instance.m_blocks == NULL)
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59 return XNEWVEC (char, block_size);
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60
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61 void *result = instance.m_blocks;
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62 instance.m_blocks = instance.m_blocks->m_next;
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63 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (result, block_size));
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64 return result;
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65 }
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66
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67 /* Return UNCAST_BLOCK to the pool. */
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68 inline void
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69 memory_block_pool::release (void *uncast_block)
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70 {
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71 block_list *block = new (uncast_block) block_list;
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72 block->m_next = instance.m_blocks;
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73 instance.m_blocks = block;
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131
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74
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75 VALGRIND_DISCARD (VALGRIND_MAKE_MEM_NOACCESS ((char *)uncast_block
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76 + sizeof (block_list),
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77 block_size
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78 - sizeof (block_list)));
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79 }
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80
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81 extern void *mempool_obstack_chunk_alloc (size_t) ATTRIBUTE_MALLOC;
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82 extern void mempool_obstack_chunk_free (void *);
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83
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84 #endif /* MEMORY_BLOCK_H */
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