/vendor/gc/include/private/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
 17typedef 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 * 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.
 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# ifdef COUNT_HDR_CACHE_HITS
 64    extern word GC_hdr_cache_hits;
 65    extern word GC_hdr_cache_misses;
 66#   define HC_HIT() ++GC_hdr_cache_hits
 67#   define HC_MISS() ++GC_hdr_cache_misses
 68# else
 69#   define HC_HIT()
 70#   define HC_MISS()
 71# endif
 72
 73  typedef struct hce {
 74    word block_addr;  	/* right shifted by LOG_HBLKSIZE */
 75    hdr * hce_hdr;
 76  } hdr_cache_entry;
 77
 78# define HDR_CACHE_SIZE 8  /* power of 2 */
 79
 80# define DECLARE_HDR_CACHE \
 81	hdr_cache_entry hdr_cache[HDR_CACHE_SIZE]
 82
 83# define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache))
 84
 85# define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1))
 86
 87# define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \
 88				((word)(h) >> LOG_HBLKSIZE))
 89
 90# define HCE_HDR(h) ((hce) -> hce_hdr)
 91
 92#ifdef PRINT_BLACK_LIST
 93  hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce, ptr_t source);
 94# define HEADER_CACHE_MISS(p, hce, source) \
 95	  GC_header_cache_miss(p, hce, source)
 96#else
 97  hdr * GC_header_cache_miss(ptr_t p, hdr_cache_entry *hce);
 98# define HEADER_CACHE_MISS(p, hce, source) GC_header_cache_miss(p, hce)
 99#endif
100
101/* Set hhdr to the header for p.  Analogous to GET_HDR below,		*/
102/* except that in the case of large objects, it				*/
103/* gets the header for the object beginning, if GC_all_interior_ptrs	*/
104/* is set.								*/
105/* Returns zero if p points to somewhere other than the first page	*/
106/* of an object, and it is not a valid pointer to the object.		*/
107# define HC_GET_HDR(p, hhdr, source, exit_label) \
108	{ \
109	  hdr_cache_entry * hce = HCE(p); \
110	  if (EXPECT(HCE_VALID_FOR(hce, p), 1)) { \
111	    HC_HIT(); \
112	    hhdr = hce -> hce_hdr; \
113	  } else { \
114	    hhdr = HEADER_CACHE_MISS(p, hce, source); \
115	    if (0 == hhdr) goto exit_label; \
116	  } \
117	}
118
119typedef struct bi {
120    hdr * index[BOTTOM_SZ];
121	/*
122 	 * The bottom level index contains one of three kinds of values:
123	 * 0 means we're not responsible for this block,
124	 *   or this is a block other than the first one in a free block.
125	 * 1 < (long)X <= MAX_JUMP means the block starts at least
126	 *        X * HBLKSIZE bytes before the current address.
127	 * A valid pointer points to a hdr structure. (The above can't be
128	 * valid pointers due to the GET_MEM return convention.)
129	 */
130    struct bi * asc_link;	/* All indices are linked in	*/
131    				/* ascending order...		*/
132    struct bi * desc_link;	/* ... and in descending order.	*/
133    word key;			/* high order address bits.	*/
134# ifdef HASH_TL
135    struct bi * hash_link;	/* Hash chain link.		*/
136# endif
137} bottom_index;
138
139/* extern bottom_index GC_all_nils; - really part of GC_arrays */
140
141/* extern bottom_index * GC_top_index []; - really part of GC_arrays */
142				/* Each entry points to a bottom_index.	*/
143				/* On a 32 bit machine, it points to 	*/
144				/* the index for a set of high order	*/
145				/* bits equal to the index.  For longer	*/
146				/* addresses, we hash the high order	*/
147				/* bits to compute the index in 	*/
148				/* GC_top_index, and each entry points	*/
149				/* to a hash chain.			*/
150				/* The last entry in each chain is	*/
151				/* GC_all_nils.				*/
152
153
154# define MAX_JUMP (HBLKSIZE - 1)
155
156# define HDR_FROM_BI(bi, p) \
157		((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)])
158# ifndef HASH_TL
159#   define BI(p) (GC_top_index \
160		[(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)])
161#   define HDR_INNER(p) HDR_FROM_BI(BI(p),p)
162#   ifdef SMALL_CONFIG
163#	define HDR(p) GC_find_header((ptr_t)(p))
164#   else
165#	define HDR(p) HDR_INNER(p)
166#   endif
167#   define GET_BI(p, bottom_indx) (bottom_indx) = BI(p)
168#   define GET_HDR(p, hhdr) (hhdr) = HDR(p)
169#   define SET_HDR(p, hhdr) HDR_INNER(p) = (hhdr)
170#   define GET_HDR_ADDR(p, ha) (ha) = &(HDR_INNER(p))
171# else /* hash */
172/*  Hash function for tree top level */
173#   define TL_HASH(hi) ((hi) & (TOP_SZ - 1))
174/*  Set bottom_indx to point to the bottom index for address p */
175#   define GET_BI(p, bottom_indx) \
176	{ \
177	    register word hi = \
178	        (word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \
179	    register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \
180	    \
181	    while (_bi -> key != hi && _bi != GC_all_nils) \
182	    	_bi = _bi -> hash_link; \
183	    (bottom_indx) = _bi; \
184	}
185#   define GET_HDR_ADDR(p, ha) \
186	{ \
187	    register bottom_index * bi; \
188	    \
189	    GET_BI(p, bi);	\
190	    (ha) = &(HDR_FROM_BI(bi, p)); \
191	}
192#   define GET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
193			      (hhdr) = *_ha; }
194#   define SET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
195			      *_ha = (hhdr); }
196#   define HDR(p) GC_find_header((ptr_t)(p))
197# endif
198			    
199/* Is the result a forwarding address to someplace closer to the	*/
200/* beginning of the block or NIL?					*/
201# define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((size_t) (hhdr) <= MAX_JUMP)
202
203/* Get an HBLKSIZE aligned address closer to the beginning of the block */
204/* h.  Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr).		*/
205# define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (size_t)(hhdr))
206# endif /*  GC_HEADERS_H */