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 * This defines HDR, GET_HDR, and SET_HDR, the main macros used to 29 * retrieve and set object headers. 30 * 31 * Since 5.0 alpha 5, we can also take advantage of a header lookup 32 * cache. This is a locally declared direct mapped cache, used inside 33 * the marker. The HC_GET_HDR macro uses and maintains this 34 * cache. Assuming we get reasonable hit rates, this shaves a few 35 * memory references from each pointer validation. 36 */ 37 38 # if CPP_WORDSZ > 32 39 # define HASH_TL 40 # endif 41 42 /* Define appropriate out-degrees for each of the two tree levels */ 43 # ifdef SMALL_CONFIG 44 # define LOG_BOTTOM_SZ 11 45 /* Keep top index size reasonable with smaller blocks. */ 46 # else 47 # define LOG_BOTTOM_SZ 10 48 # endif 49 # ifndef HASH_TL 50 # define LOG_TOP_SZ (WORDSZ - LOG_BOTTOM_SZ - LOG_HBLKSIZE) 51 # else 52 # define LOG_TOP_SZ 11 53 # endif 54 # define TOP_SZ (1 << LOG_TOP_SZ) 55 # define BOTTOM_SZ (1 << LOG_BOTTOM_SZ) 56 57 #ifndef SMALL_CONFIG 58 # define USE_HDR_CACHE 59 #endif 60 61 /* #define COUNT_HDR_CACHE_HITS */ 62 63 extern hdr * GC_invalid_header; /* header for an imaginary block */ 64 /* containing no objects. */ 65 66 67 /* Check whether p and corresponding hhdr point to long or invalid */ 68 /* object. If so, advance hhdr to */ 69 /* beginning of block, or set hhdr to GC_invalid_header. */ 70 #define ADVANCE(p, hhdr, source) \ 71 { \ 72 hdr * new_hdr = GC_invalid_header; \ 73 p = GC_find_start(p, hhdr, &new_hdr); \ 74 hhdr = new_hdr; \ 75 } 76 77 #ifdef USE_HDR_CACHE 78 79 # ifdef COUNT_HDR_CACHE_HITS 80 extern word GC_hdr_cache_hits; 81 extern word GC_hdr_cache_misses; 82 # define HC_HIT() ++GC_hdr_cache_hits 83 # define HC_MISS() ++GC_hdr_cache_misses 84 # else 85 # define HC_HIT() 86 # define HC_MISS() 87 # endif 88 89 typedef struct hce { 90 word block_addr; /* right shifted by LOG_HBLKSIZE */ 91 hdr * hce_hdr; 92 } hdr_cache_entry; 93 94 # define HDR_CACHE_SIZE 8 /* power of 2 */ 95 96 # define DECLARE_HDR_CACHE \ 97 hdr_cache_entry hdr_cache[HDR_CACHE_SIZE] 98 99 # define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache)); 100 101 # define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1)) 102 103 # define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \ 104 ((word)(h) >> LOG_HBLKSIZE)) 105 106 # define HCE_HDR(h) ((hce) -> hce_hdr) 107 108 109 /* Analogous to GET_HDR, except that in the case of large objects, it */ 110 /* Returns the header for the object beginning, and updates p. */ 111 /* Returns &GC_bad_header instead of 0. All of this saves a branch */ 112 /* in the fast path. */ 113 # define HC_GET_HDR(p, hhdr, source) \ 114 { \ 115 hdr_cache_entry * hce = HCE(p); \ 116 if (HCE_VALID_FOR(hce, p)) { \ 117 HC_HIT(); \ 118 hhdr = hce -> hce_hdr; \ 119 } else { \ 120 HC_MISS(); \ 121 GET_HDR(p, hhdr); \ 122 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \ 123 ADVANCE(p, hhdr, source); \ 124 } else { \ 125 hce -> block_addr = (word)(p) >> LOG_HBLKSIZE; \ 126 hce -> hce_hdr = hhdr; \ 127 } \ 128 } \ 129 } 130 131 #else /* !USE_HDR_CACHE */ 132 133 # define DECLARE_HDR_CACHE 134 135 # define INIT_HDR_CACHE 136 137 # define HC_GET_HDR(p, hhdr, source) \ 138 { \ 139 GET_HDR(p, hhdr); \ 140 if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \ 141 ADVANCE(p, hhdr, source); \ 142 } \ 143 } 144 #endif 145 146 typedef struct bi { 147 hdr * index[BOTTOM_SZ]; 148 /* 149 * The bottom level index contains one of three kinds of values: 150 * 0 means we're not responsible for this block, 151 * or this is a block other than the first one in a free block. 152 * 1 < (long)X <= MAX_JUMP means the block starts at least 153 * X * HBLKSIZE bytes before the current address. 154 * A valid pointer points to a hdr structure. (The above can't be 155 * valid pointers due to the GET_MEM return convention.) 156 */ 157 struct bi * asc_link; /* All indices are linked in */ 158 /* ascending order... */ 159 struct bi * desc_link; /* ... and in descending order. */ 160 word key; /* high order address bits. */ 161 # ifdef HASH_TL 162 struct bi * hash_link; /* Hash chain link. */ 163 # endif 164 } bottom_index; 165 166 /* extern bottom_index GC_all_nils; - really part of GC_arrays */ 167 168 /* extern bottom_index * GC_top_index []; - really part of GC_arrays */ 169 /* Each entry points to a bottom_index. */ 170 /* On a 32 bit machine, it points to */ 171 /* the index for a set of high order */ 172 /* bits equal to the index. For longer */ 173 /* addresses, we hash the high order */ 174 /* bits to compute the index in */ 175 /* GC_top_index, and each entry points */ 176 /* to a hash chain. */ 177 /* The last entry in each chain is */ 178 /* GC_all_nils. */ 179 180 181 # define MAX_JUMP (HBLKSIZE - 1) 182 183 # define HDR_FROM_BI(bi, p) \ 184 ((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)]) 185 # ifndef HASH_TL 186 # define BI(p) (GC_top_index \ 187 [(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)]) 188 # define HDR_INNER(p) HDR_FROM_BI(BI(p),p) 189 # ifdef SMALL_CONFIG 190 # define HDR(p) GC_find_header((ptr_t)(p)) 191 # else 192 # define HDR(p) HDR_INNER(p) 193 # endif 194 # define GET_BI(p, bottom_indx) (bottom_indx) = BI(p) 195 # define GET_HDR(p, hhdr) (hhdr) = HDR(p) 196 # define SET_HDR(p, hhdr) HDR_INNER(p) = (hhdr) 197 # define GET_HDR_ADDR(p, ha) (ha) = &(HDR_INNER(p)) 198 # else /* hash */ 199 /* Hash function for tree top level */ 200 # define TL_HASH(hi) ((hi) & (TOP_SZ - 1)) 201 /* Set bottom_indx to point to the bottom index for address p */ 202 # define GET_BI(p, bottom_indx) \ 203 { \ 204 register word hi = \ 205 (word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \ 206 register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \ 207 \ 208 while (_bi -> key != hi && _bi != GC_all_nils) \ 209 _bi = _bi -> hash_link; \ 210 (bottom_indx) = _bi; \ 211 } 212 # define GET_HDR_ADDR(p, ha) \ 213 { \ 214 register bottom_index * bi; \ 215 \ 216 GET_BI(p, bi); \ 217 (ha) = &(HDR_FROM_BI(bi, p)); \ 218 } 219 # define GET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \ 220 (hhdr) = *_ha; } 221 # define SET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \ 222 *_ha = (hhdr); } 223 # define HDR(p) GC_find_header((ptr_t)(p)) 224 # endif 225 226 /* Is the result a forwarding address to someplace closer to the */ 227 /* beginning of the block or NIL? */ 228 # define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((unsigned long) (hhdr) <= MAX_JUMP) 229 230 /* Get an HBLKSIZE aligned address closer to the beginning of the block */ 231 /* h. Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr). */ 232 # define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (unsigned long)(hhdr)) 233 # endif /* GC_HEADERS_H */ 234