boehm-gc/gc_hdrs.h

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   4  *
   5  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   6  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   7  *
   8  * Permission is hereby granted to use or copy this program
   9  * for any purpose,  provided the above notices are retained on all copies.
  10  * Permission to modify the code and to distribute modified code is granted,
  11  * provided the above notices are retained, and a notice that the code was
  12  * modified is included with the above copyright notice.
  13  */
  14 /* Boehm, July 11, 1995 11:54 am PDT */
  15 # ifndef GC_HEADERS_H
  16 # define GC_HEADERS_H
  17 typedef struct hblkhdr hdr;
  18
  19 # if CPP_WORDSZ != 32 && CPP_WORDSZ < 36
  20         --> Get a real machine.
  21 # endif
  22
  23 /*
  24  * The 2 level tree data structure that is used to find block headers.
  25  * If there are more than 32 bits in a pointer, the top level is a hash
  26  * table.
  27  */
  28
  29 # if CPP_WORDSZ > 32
  30 #   define HASH_TL
  31 # endif
  32
  33 /* Define appropriate out-degrees for each of the two tree levels       */
  34 # ifdef SMALL_CONFIG
  35 #   define LOG_BOTTOM_SZ 11
  36         /* Keep top index size reasonable with smaller blocks. */
  37 # else
  38 #   define LOG_BOTTOM_SZ 10
  39 # endif
  40 # ifndef HASH_TL
  41 #   define LOG_TOP_SZ (WORDSZ - LOG_BOTTOM_SZ - LOG_HBLKSIZE)
  42 # else
  43 #   define LOG_TOP_SZ 11
  44 # endif
  45 # define TOP_SZ (1 << LOG_TOP_SZ)
  46 # define BOTTOM_SZ (1 << LOG_BOTTOM_SZ)
  47
  48 typedef struct bi {
  49     hdr * index[BOTTOM_SZ];
  50         /*
  51          * The bottom level index contains one of three kinds of values:
  52          * 0 means we're not responsible for this block.
  53          * 1 < (long)X <= MAX_JUMP means the block starts at least
  54          *        X * HBLKSIZE bytes before the current address.
  55          * A valid pointer points to a hdr structure. (The above can't be
  56          * valid pointers due to the GET_MEM return convention.)
  57          */
  58     struct bi * asc_link;       /* All indices are linked in    */
  59                                 /* ascending order.             */
  60     word key;                   /* high order address bits.     */
  61 # ifdef HASH_TL
  62     struct bi * hash_link;      /* Hash chain link.             */
  63 # endif
  64 } bottom_index;
  65
  66 /* extern bottom_index GC_all_nils; - really part of GC_arrays */
  67
  68 /* extern bottom_index * GC_top_index []; - really part of GC_arrays */
  69                                 /* Each entry points to a bottom_index. */
  70                                 /* On a 32 bit machine, it points to    */
  71                                 /* the index for a set of high order    */
  72                                 /* bits equal to the index.  For longer */
  73                                 /* addresses, we hash the high order    */
  74                                 /* bits to compute the index in         */
  75                                 /* GC_top_index, and each entry points  */
  76                                 /* to a hash chain.                     */
  77                                 /* The last entry in each chain is      */
  78                                 /* GC_all_nils.                         */
  79
  80
  81 # define MAX_JUMP (HBLKSIZE - 1)
  82
  83 # define HDR_FROM_BI(bi, p) \
  84                 ((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)])
  85 # ifndef HASH_TL
  86 #   define BI(p) (GC_top_index \
  87                 [(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)])
  88 #   define HDR_INNER(p) HDR_FROM_BI(BI(p),p)
  89 #   ifdef SMALL_CONFIG
  90 #       define HDR(p) GC_find_header((ptr_t)(p))
  91 #   else
  92 #       define HDR(p) HDR_INNER(p)
  93 #   endif
  94 #   define GET_BI(p, bottom_indx) (bottom_indx) = BI(p)
  95 #   define GET_HDR(p, hhdr) (hhdr) = HDR(p)
  96 #   define SET_HDR(p, hhdr) HDR_INNER(p) = (hhdr)
  97 #   define GET_HDR_ADDR(p, ha) (ha) = &(HDR_INNER(p))
  98 # else /* hash */
  99 /*  Hash function for tree top level */
 100 #   define TL_HASH(hi) ((hi) & (TOP_SZ - 1))
 101 /*  Set bottom_indx to point to the bottom index for address p */
 102 #   define GET_BI(p, bottom_indx) \
 103         { \
 104             register word hi = \
 105                 (word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \
 106             register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \
 107             \
 108             while (_bi -> key != hi && _bi != GC_all_nils) \
 109                 _bi = _bi -> hash_link; \
 110             (bottom_indx) = _bi; \
 111         }
 112 #   define GET_HDR_ADDR(p, ha) \
 113         { \
 114             register bottom_index * bi; \
 115             \
 116             GET_BI(p, bi);      \
 117             (ha) = &(HDR_FROM_BI(bi, p)); \
 118         }
 119 #   define GET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
 120                               (hhdr) = *_ha; }
 121 #   define SET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
 122                               *_ha = (hhdr); }
 123 #   define HDR(p) GC_find_header((ptr_t)(p))
 124 # endif
 125
 126 /* Is the result a forwarding address to someplace closer to the        */
 127 /* beginning of the block or NIL?                                       */
 128 # define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((unsigned long) (hhdr) <= MAX_JUMP)
 129
 130 /* Get an HBLKSIZE aligned address closer to the beginning of the block */
 131 /* h.  Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr).             */
 132 # define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (unsigned long)(hhdr))
 133 # endif /*  GC_HEADERS_H */