2 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
3 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
5 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
6 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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.
14 /* Boehm, July 11, 1995 11:54 am PDT */
17 typedef struct hblkhdr hdr;
19 # if CPP_WORDSZ != 32 && CPP_WORDSZ < 36
20 --> Get a real machine.
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
28 * This defines HDR, GET_HDR, and SET_HDR, the main macros used to
29 * retrieve and set object headers.
31 * We 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.
42 /* Define appropriate out-degrees for each of the two tree levels */
44 # define LOG_BOTTOM_SZ 11
45 /* Keep top index size reasonable with smaller blocks. */
47 # define LOG_BOTTOM_SZ 10
50 # define LOG_TOP_SZ (WORDSZ - LOG_BOTTOM_SZ - LOG_HBLKSIZE)
52 # define LOG_TOP_SZ 11
54 # define TOP_SZ (1 << LOG_TOP_SZ)
55 # define BOTTOM_SZ (1 << LOG_BOTTOM_SZ)
57 /* #define COUNT_HDR_CACHE_HITS */
59 # ifdef COUNT_HDR_CACHE_HITS
60 extern word GC_hdr_cache_hits; /* used for debugging/profiling */
61 extern word GC_hdr_cache_misses;
62 # define HC_HIT() ++GC_hdr_cache_hits
63 # define HC_MISS() ++GC_hdr_cache_misses
70 word block_addr; /* right shifted by LOG_HBLKSIZE */
74 # define HDR_CACHE_SIZE 8 /* power of 2 */
76 # define DECLARE_HDR_CACHE \
77 hdr_cache_entry hdr_cache[HDR_CACHE_SIZE]
79 # define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache))
81 # define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1))
83 # define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \
84 ((word)(h) >> LOG_HBLKSIZE))
86 # define HCE_HDR(h) ((hce) -> hce_hdr)
88 #ifdef PRINT_BLACK_LIST
89 GC_INNER hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce,
91 # define HEADER_CACHE_MISS(p, hce, source) \
92 GC_header_cache_miss(p, hce, source)
94 GC_INNER hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce);
95 # define HEADER_CACHE_MISS(p, hce, source) GC_header_cache_miss(p, hce)
98 /* Set hhdr to the header for p. Analogous to GET_HDR below, */
99 /* except that in the case of large objects, it */
100 /* gets the header for the object beginning, if GC_all_interior_ptrs */
102 /* Returns zero if p points to somewhere other than the first page */
103 /* of an object, and it is not a valid pointer to the object. */
104 # define HC_GET_HDR(p, hhdr, source, exit_label) \
106 hdr_cache_entry * hce = HCE(p); \
107 if (EXPECT(HCE_VALID_FOR(hce, p), 1)) { \
109 hhdr = hce -> hce_hdr; \
111 hhdr = HEADER_CACHE_MISS(p, hce, source); \
112 if (0 == hhdr) goto exit_label; \
117 hdr * index[BOTTOM_SZ];
119 * The bottom level index contains one of three kinds of values:
120 * 0 means we're not responsible for this block,
121 * or this is a block other than the first one in a free block.
122 * 1 < (long)X <= MAX_JUMP means the block starts at least
123 * X * HBLKSIZE bytes before the current address.
124 * A valid pointer points to a hdr structure. (The above can't be
125 * valid pointers due to the GET_MEM return convention.)
127 struct bi * asc_link; /* All indices are linked in */
128 /* ascending order... */
129 struct bi * desc_link; /* ... and in descending order. */
130 word key; /* high order address bits. */
132 struct bi * hash_link; /* Hash chain link. */
136 /* bottom_index GC_all_nils; - really part of GC_arrays */
138 /* extern bottom_index * GC_top_index []; - really part of GC_arrays */
139 /* Each entry points to a bottom_index. */
140 /* On a 32 bit machine, it points to */
141 /* the index for a set of high order */
142 /* bits equal to the index. For longer */
143 /* addresses, we hash the high order */
144 /* bits to compute the index in */
145 /* GC_top_index, and each entry points */
146 /* to a hash chain. */
147 /* The last entry in each chain is */
151 # define MAX_JUMP (HBLKSIZE - 1)
153 # define HDR_FROM_BI(bi, p) \
154 ((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)])
156 # define BI(p) (GC_top_index \
157 [(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)])
158 # define HDR_INNER(p) HDR_FROM_BI(BI(p),p)
160 # define HDR(p) GC_find_header((ptr_t)(p))
162 # define HDR(p) HDR_INNER(p)
164 # define GET_BI(p, bottom_indx) (bottom_indx) = BI(p)
165 # define GET_HDR(p, hhdr) (hhdr) = HDR(p)
166 # define SET_HDR(p, hhdr) HDR_INNER(p) = (hhdr)
167 # define GET_HDR_ADDR(p, ha) (ha) = &(HDR_INNER(p))
169 /* Hash function for tree top level */
170 # define TL_HASH(hi) ((hi) & (TOP_SZ - 1))
171 /* Set bottom_indx to point to the bottom index for address p */
172 # define GET_BI(p, bottom_indx) \
175 (word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \
176 register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \
178 while (_bi -> key != hi && _bi != GC_all_nils) \
179 _bi = _bi -> hash_link; \
180 (bottom_indx) = _bi; \
182 # define GET_HDR_ADDR(p, ha) \
184 register bottom_index * bi; \
187 (ha) = &(HDR_FROM_BI(bi, p)); \
189 # define GET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
191 # define SET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
193 # define HDR(p) GC_find_header((ptr_t)(p))
196 /* Is the result a forwarding address to someplace closer to the */
197 /* beginning of the block or NIL? */
198 # define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((size_t) (hhdr) <= MAX_JUMP)
200 /* Get an HBLKSIZE aligned address closer to the beginning of the block */
201 /* h. Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr). */
202 # define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (size_t)(hhdr))
203 # endif /* GC_HEADERS_H */