| 1 | /*
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| 2 | * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
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| 3 | * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
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| 4 | *
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| 5 | * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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| 6 | * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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| 7 | *
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| 8 | * Permission is hereby granted to use or copy this program
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| 9 | * for any purpose, provided the above notices are retained on all copies.
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| 10 | * Permission to modify the code and to distribute modified code is granted,
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| 11 | * provided the above notices are retained, and a notice that the code was
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| 12 | * modified is included with the above copyright notice.
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| 13 | */
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| 14 | /* Boehm, July 11, 1995 11:54 am PDT */
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| 15 | # ifndef GC_HEADERS_H
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| 16 | # define GC_HEADERS_H
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| 17 | typedef struct hblkhdr hdr;
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| 18 |
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| 19 | # if CPP_WORDSZ != 32 && CPP_WORDSZ < 36
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| 20 | --> Get a real machine.
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| 21 | # endif
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| 22 |
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| 23 | /*
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| 24 | * The 2 level tree data structure that is used to find block headers.
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| 25 | * If there are more than 32 bits in a pointer, the top level is a hash
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| 26 | * table.
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| 27 | *
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| 28 | * This defines HDR, GET_HDR, and SET_HDR, the main macros used to
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| 29 | * retrieve and set object headers.
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| 30 | *
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| 31 | * Since 5.0 alpha 5, we can also take advantage of a header lookup
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| 32 | * cache. This is a locally declared direct mapped cache, used inside
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| 33 | * the marker. The HC_GET_HDR macro uses and maintains this
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| 34 | * cache. Assuming we get reasonable hit rates, this shaves a few
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| 35 | * memory references from each pointer validation.
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| 36 | */
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| 37 |
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| 38 | # if CPP_WORDSZ > 32
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| 39 | # define HASH_TL
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| 40 | # endif
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| 41 |
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| 42 | /* Define appropriate out-degrees for each of the two tree levels */
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| 43 | # ifdef SMALL_CONFIG
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| 44 | # define LOG_BOTTOM_SZ 11
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| 45 | /* Keep top index size reasonable with smaller blocks. */
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| 46 | # else
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| 47 | # define LOG_BOTTOM_SZ 10
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| 48 | # endif
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| 49 | # ifndef HASH_TL
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| 50 | # define LOG_TOP_SZ (WORDSZ - LOG_BOTTOM_SZ - LOG_HBLKSIZE)
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| 51 | # else
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| 52 | # define LOG_TOP_SZ 11
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| 53 | # endif
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| 54 | # define TOP_SZ (1 << LOG_TOP_SZ)
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| 55 | # define BOTTOM_SZ (1 << LOG_BOTTOM_SZ)
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| 56 |
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| 57 | #ifndef SMALL_CONFIG
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| 58 | # define USE_HDR_CACHE
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| 59 | #endif
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| 60 |
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| 61 | /* #define COUNT_HDR_CACHE_HITS */
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| 62 |
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| 63 | extern hdr * GC_invalid_header; /* header for an imaginary block */
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| 64 | /* containing no objects. */
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| 65 |
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| 66 |
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| 67 | /* Check whether p and corresponding hhdr point to long or invalid */
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| 68 | /* object. If so, advance hhdr to */
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| 69 | /* beginning of block, or set hhdr to GC_invalid_header. */
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| 70 | #define ADVANCE(p, hhdr, source) \
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| 71 | { \
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| 72 | hdr * new_hdr = GC_invalid_header; \
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| 73 | p = GC_FIND_START(p, hhdr, &new_hdr, (word)source); \
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| 74 | hhdr = new_hdr; \
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| 75 | }
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| 76 |
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| 77 | #ifdef USE_HDR_CACHE
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| 78 |
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| 79 | # ifdef COUNT_HDR_CACHE_HITS
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| 80 | extern word GC_hdr_cache_hits;
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| 81 | extern word GC_hdr_cache_misses;
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| 82 | # define HC_HIT() ++GC_hdr_cache_hits
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| 83 | # define HC_MISS() ++GC_hdr_cache_misses
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| 84 | # else
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| 85 | # define HC_HIT()
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| 86 | # define HC_MISS()
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| 87 | # endif
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| 88 |
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| 89 | typedef struct hce {
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| 90 | word block_addr; /* right shifted by LOG_HBLKSIZE */
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| 91 | hdr * hce_hdr;
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| 92 | } hdr_cache_entry;
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| 93 |
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| 94 | # define HDR_CACHE_SIZE 8 /* power of 2 */
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| 95 |
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| 96 | # define DECLARE_HDR_CACHE \
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| 97 | hdr_cache_entry hdr_cache[HDR_CACHE_SIZE]
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| 98 |
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| 99 | # define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache));
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| 100 |
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| 101 | # define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1))
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| 102 |
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| 103 | # define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \
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| 104 | ((word)(h) >> LOG_HBLKSIZE))
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| 105 |
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| 106 | # define HCE_HDR(h) ((hce) -> hce_hdr)
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| 107 |
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| 108 |
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| 109 | /* Analogous to GET_HDR, except that in the case of large objects, it */
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| 110 | /* Returns the header for the object beginning, and updates p. */
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| 111 | /* Returns &GC_bad_header instead of 0. All of this saves a branch */
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| 112 | /* in the fast path. */
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| 113 | # define HC_GET_HDR(p, hhdr, source) \
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| 114 | { \
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| 115 | hdr_cache_entry * hce = HCE(p); \
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| 116 | if (HCE_VALID_FOR(hce, p)) { \
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| 117 | HC_HIT(); \
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| 118 | hhdr = hce -> hce_hdr; \
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| 119 | } else { \
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| 120 | HC_MISS(); \
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| 121 | GET_HDR(p, hhdr); \
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| 122 | if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \
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| 123 | ADVANCE(p, hhdr, source); \
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| 124 | } else { \
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| 125 | hce -> block_addr = (word)(p) >> LOG_HBLKSIZE; \
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| 126 | hce -> hce_hdr = hhdr; \
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| 127 | } \
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| 128 | } \
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| 129 | }
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| 130 |
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| 131 | #else /* !USE_HDR_CACHE */
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| 132 |
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| 133 | # define DECLARE_HDR_CACHE
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| 134 |
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| 135 | # define INIT_HDR_CACHE
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| 136 |
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| 137 | # define HC_GET_HDR(p, hhdr, source) \
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| 138 | { \
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| 139 | GET_HDR(p, hhdr); \
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| 140 | if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \
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| 141 | ADVANCE(p, hhdr, source); \
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| 142 | } \
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| 143 | }
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| 144 | #endif
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| 145 |
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| 146 | typedef struct bi {
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| 147 | hdr * index[BOTTOM_SZ];
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| 148 | /*
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| 149 | * The bottom level index contains one of three kinds of values:
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| 150 | * 0 means we're not responsible for this block,
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| 151 | * or this is a block other than the first one in a free block.
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| 152 | * 1 < (long)X <= MAX_JUMP means the block starts at least
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| 153 | * X * HBLKSIZE bytes before the current address.
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| 154 | * A valid pointer points to a hdr structure. (The above can't be
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| 155 | * valid pointers due to the GET_MEM return convention.)
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| 156 | */
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| 157 | struct bi * asc_link; /* All indices are linked in */
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| 158 | /* ascending order... */
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| 159 | struct bi * desc_link; /* ... and in descending order. */
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| 160 | word key; /* high order address bits. */
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| 161 | # ifdef HASH_TL
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| 162 | struct bi * hash_link; /* Hash chain link. */
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| 163 | # endif
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| 164 | } bottom_index;
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| 165 |
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| 166 | /* extern bottom_index GC_all_nils; - really part of GC_arrays */
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| 167 |
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| 168 | /* extern bottom_index * GC_top_index []; - really part of GC_arrays */
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| 169 | /* Each entry points to a bottom_index. */
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| 170 | /* On a 32 bit machine, it points to */
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| 171 | /* the index for a set of high order */
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| 172 | /* bits equal to the index. For longer */
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| 173 | /* addresses, we hash the high order */
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| 174 | /* bits to compute the index in */
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| 175 | /* GC_top_index, and each entry points */
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| 176 | /* to a hash chain. */
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| 177 | /* The last entry in each chain is */
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| 178 | /* GC_all_nils. */
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| 179 |
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| 180 |
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| 181 | # define MAX_JUMP (HBLKSIZE - 1)
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| 182 |
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| 183 | # define HDR_FROM_BI(bi, p) \
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| 184 | ((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)])
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| 185 | # ifndef HASH_TL
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| 186 | # define BI(p) (GC_top_index \
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| 187 | [(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)])
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| 188 | # define HDR_INNER(p) HDR_FROM_BI(BI(p),p)
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| 189 | # ifdef SMALL_CONFIG
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| 190 | # define HDR(p) GC_find_header((ptr_t)(p))
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| 191 | # else
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| 192 | # define HDR(p) HDR_INNER(p)
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| 193 | # endif
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| 194 | # define GET_BI(p, bottom_indx) (bottom_indx) = BI(p)
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| 195 | # define GET_HDR(p, hhdr) (hhdr) = HDR(p)
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| 196 | # define SET_HDR(p, hhdr) HDR_INNER(p) = (hhdr)
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| 197 | # define GET_HDR_ADDR(p, ha) (ha) = &(HDR_INNER(p))
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| 198 | # else /* hash */
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| 199 | /* Hash function for tree top level */
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| 200 | # define TL_HASH(hi) ((hi) & (TOP_SZ - 1))
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| 201 | /* Set bottom_indx to point to the bottom index for address p */
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| 202 | # define GET_BI(p, bottom_indx) \
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| 203 | { \
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| 204 | register word hi = \
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| 205 | (word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \
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| 206 | register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \
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| 207 | \
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| 208 | while (_bi -> key != hi && _bi != GC_all_nils) \
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| 209 | _bi = _bi -> hash_link; \
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| 210 | (bottom_indx) = _bi; \
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| 211 | }
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| 212 | # define GET_HDR_ADDR(p, ha) \
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| 213 | { \
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| 214 | register bottom_index * bi; \
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| 215 | \
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| 216 | GET_BI(p, bi); \
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| 217 | (ha) = &(HDR_FROM_BI(bi, p)); \
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| 218 | }
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| 219 | # define GET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
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| 220 | (hhdr) = *_ha; }
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| 221 | # define SET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
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| 222 | *_ha = (hhdr); }
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| 223 | # define HDR(p) GC_find_header((ptr_t)(p))
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| 224 | # endif
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| 225 |
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| 226 | /* Is the result a forwarding address to someplace closer to the */
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| 227 | /* beginning of the block or NIL? */
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| 228 | # define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((unsigned long) (hhdr) <= MAX_JUMP)
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| 229 |
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| 230 | /* Get an HBLKSIZE aligned address closer to the beginning of the block */
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| 231 | /* h. Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr). */
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| 232 | # define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (unsigned long)(hhdr))
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| 233 | # endif /* GC_HEADERS_H */
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