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/*
* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
/* Boehm, July 11, 1995 11:54 am PDT */
# ifndef GC_HEADERS_H
# define GC_HEADERS_H
typedef struct hblkhdr hdr;
# if CPP_WORDSZ != 32 && CPP_WORDSZ < 36
--> Get a real machine.
# endif
/*
* The 2 level tree data structure that is used to find block headers.
* If there are more than 32 bits in a pointer, the top level is a hash
* table.
*
* This defines HDR, GET_HDR, and SET_HDR, the main macros used to
* retrieve and set object headers.
*
* Since 5.0 alpha 5, we can also take advantage of a header lookup
* cache. This is a locally declared direct mapped cache, used inside
* the marker. The HC_GET_HDR macro uses and maintains this
* cache. Assuming we get reasonable hit rates, this shaves a few
* memory references from each pointer validation.
*/
# if CPP_WORDSZ > 32
# define HASH_TL
# endif
/* Define appropriate out-degrees for each of the two tree levels */
# ifdef SMALL_CONFIG
# define LOG_BOTTOM_SZ 11
/* Keep top index size reasonable with smaller blocks. */
# else
# define LOG_BOTTOM_SZ 10
# endif
# ifndef HASH_TL
# define LOG_TOP_SZ (WORDSZ - LOG_BOTTOM_SZ - LOG_HBLKSIZE)
# else
# define LOG_TOP_SZ 11
# endif
# define TOP_SZ (1 << LOG_TOP_SZ)
# define BOTTOM_SZ (1 << LOG_BOTTOM_SZ)
#ifndef SMALL_CONFIG
# define USE_HDR_CACHE
#endif
/* #define COUNT_HDR_CACHE_HITS */
extern hdr * GC_invalid_header; /* header for an imaginary block */
/* containing no objects. */
/* Check whether p and corresponding hhdr point to long or invalid */
/* object. If so, advance hhdr to */
/* beginning of block, or set hhdr to GC_invalid_header. */
#define ADVANCE(p, hhdr, source) \
{ \
hdr * new_hdr = GC_invalid_header; \
p = GC_FIND_START(p, hhdr, &new_hdr, (word)source); \
hhdr = new_hdr; \
}
#ifdef USE_HDR_CACHE
# ifdef COUNT_HDR_CACHE_HITS
extern word GC_hdr_cache_hits;
extern word GC_hdr_cache_misses;
# define HC_HIT() ++GC_hdr_cache_hits
# define HC_MISS() ++GC_hdr_cache_misses
# else
# define HC_HIT()
# define HC_MISS()
# endif
typedef struct hce {
word block_addr; /* right shifted by LOG_HBLKSIZE */
hdr * hce_hdr;
} hdr_cache_entry;
# define HDR_CACHE_SIZE 8 /* power of 2 */
# define DECLARE_HDR_CACHE \
hdr_cache_entry hdr_cache[HDR_CACHE_SIZE]
# define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache));
# define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1))
# define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \
((word)(h) >> LOG_HBLKSIZE))
# define HCE_HDR(h) ((hce) -> hce_hdr)
/* Analogous to GET_HDR, except that in the case of large objects, it */
/* Returns the header for the object beginning, and updates p. */
/* Returns &GC_bad_header instead of 0. All of this saves a branch */
/* in the fast path. */
# define HC_GET_HDR(p, hhdr, source) \
{ \
hdr_cache_entry * hce = HCE(p); \
if (HCE_VALID_FOR(hce, p)) { \
HC_HIT(); \
hhdr = hce -> hce_hdr; \
} else { \
HC_MISS(); \
GET_HDR(p, hhdr); \
if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \
ADVANCE(p, hhdr, source); \
} else { \
hce -> block_addr = (word)(p) >> LOG_HBLKSIZE; \
hce -> hce_hdr = hhdr; \
} \
} \
}
#else /* !USE_HDR_CACHE */
# define DECLARE_HDR_CACHE
# define INIT_HDR_CACHE
# define HC_GET_HDR(p, hhdr, source) \
{ \
GET_HDR(p, hhdr); \
if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \
ADVANCE(p, hhdr, source); \
} \
}
#endif
typedef struct bi {
hdr * index[BOTTOM_SZ];
/*
* The bottom level index contains one of three kinds of values:
* 0 means we're not responsible for this block,
* or this is a block other than the first one in a free block.
* 1 < (long)X <= MAX_JUMP means the block starts at least
* X * HBLKSIZE bytes before the current address.
* A valid pointer points to a hdr structure. (The above can't be
* valid pointers due to the GET_MEM return convention.)
*/
struct bi * asc_link; /* All indices are linked in */
/* ascending order... */
struct bi * desc_link; /* ... and in descending order. */
word key; /* high order address bits. */
# ifdef HASH_TL
struct bi * hash_link; /* Hash chain link. */
# endif
} bottom_index;
/* extern bottom_index GC_all_nils; - really part of GC_arrays */
/* extern bottom_index * GC_top_index []; - really part of GC_arrays */
/* Each entry points to a bottom_index. */
/* On a 32 bit machine, it points to */
/* the index for a set of high order */
/* bits equal to the index. For longer */
/* addresses, we hash the high order */
/* bits to compute the index in */
/* GC_top_index, and each entry points */
/* to a hash chain. */
/* The last entry in each chain is */
/* GC_all_nils. */
# define MAX_JUMP (HBLKSIZE - 1)
# define HDR_FROM_BI(bi, p) \
((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)])
# ifndef HASH_TL
# define BI(p) (GC_top_index \
[(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)])
# define HDR_INNER(p) HDR_FROM_BI(BI(p),p)
# ifdef SMALL_CONFIG
# define HDR(p) GC_find_header((ptr_t)(p))
# else
# define HDR(p) HDR_INNER(p)
# endif
# define GET_BI(p, bottom_indx) (bottom_indx) = BI(p)
# define GET_HDR(p, hhdr) (hhdr) = HDR(p)
# define SET_HDR(p, hhdr) HDR_INNER(p) = (hhdr)
# define GET_HDR_ADDR(p, ha) (ha) = &(HDR_INNER(p))
# else /* hash */
/* Hash function for tree top level */
# define TL_HASH(hi) ((hi) & (TOP_SZ - 1))
/* Set bottom_indx to point to the bottom index for address p */
# define GET_BI(p, bottom_indx) \
{ \
register word hi = \
(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \
register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \
\
while (_bi -> key != hi && _bi != GC_all_nils) \
_bi = _bi -> hash_link; \
(bottom_indx) = _bi; \
}
# define GET_HDR_ADDR(p, ha) \
{ \
register bottom_index * bi; \
\
GET_BI(p, bi); \
(ha) = &(HDR_FROM_BI(bi, p)); \
}
# define GET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
(hhdr) = *_ha; }
# define SET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
*_ha = (hhdr); }
# define HDR(p) GC_find_header((ptr_t)(p))
# endif
/* Is the result a forwarding address to someplace closer to the */
/* beginning of the block or NIL? */
# define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((unsigned long) (hhdr) <= MAX_JUMP)
/* Get an HBLKSIZE aligned address closer to the beginning of the block */
/* h. Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr). */
# define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (unsigned long)(hhdr))
# endif /* GC_HEADERS_H */
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