--- /dev/null
+/*
+ * 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); \
+ 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_invalid_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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