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Diffstat (limited to 'include/gc_mark.h')
| -rw-r--r-- | include/gc_mark.h | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/include/gc_mark.h b/include/gc_mark.h new file mode 100644 index 00000000..0856d16f --- /dev/null +++ b/include/gc_mark.h @@ -0,0 +1,145 @@ +/* + * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved. + * Copyright (c) 2001 by Hewlett-Packard Company. 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. + * + */ + +/* + * This contains interfaces to the GC marker that are likely to be useful to + * clients that provide detailed heap layout information to the collector. + * This interface should not be used by normal C or C++ clients. + * It will be useful to runtimes for other languages. + * + * Note that this file is not "namespace-clean", i.e. it introduces names + * not prefixed with GC_, which may collide with the client's names. It + * should be included only in those few places that directly provide + * information to the collector. + */ +#ifndef GC_MARK_H +# define GC_MARK_H + +# ifndef GC_H +# include "gc.h" +# endif + +/* A client supplied mark procedure. Returns new mark stack pointer. */ +/* Primary effect should be to push new entries on the mark stack. */ +/* Mark stack pointer values are passed and returned explicitly. */ +/* Global variables decribing mark stack are not necessarily valid. */ +/* (This usually saves a few cycles by keeping things in registers.) */ +/* Assumed to scan about GC_PROC_BYTES on average. If it needs to do */ +/* much more work than that, it should do it in smaller pieces by */ +/* pushing itself back on the mark stack. */ +/* Note that it should always do some work (defined as marking some */ +/* objects) before pushing more than one entry on the mark stack. */ +/* This is required to ensure termination in the event of mark stack */ +/* overflows. */ +/* This procedure is always called with at least one empty entry on the */ +/* mark stack. */ +/* Currently we require that mark procedures look for pointers in a */ +/* subset of the places the conservative marker would. It must be safe */ +/* to invoke the normal mark procedure instead. */ +/* WARNING: Such a mark procedure may be invoked on an unused object */ +/* residing on a free list. Such objects are cleared, except for a */ +/* free list link field in the first word. Thus mark procedures may */ +/* not count on the presence of a type descriptor, and must handle this */ +/* case correctly somehow. */ +# define GC_PROC_BYTES 100 +struct GC_ms_entry; +typedef struct GC_ms_entry * (*GC_mark_proc) GC_PROTO(( + GC_word * addr, struct GC_ms_entry * mark_stack_ptr, + struct GC_ms_entry * mark_stack_limit, GC_word env)); + +# define GC_LOG_MAX_MARK_PROCS 6 +# define GC_MAX_MARK_PROCS (1 << GC_LOG_MAX_MARK_PROCS) + +/* In a few cases it's necessary to assign statically known indices to */ +/* certain mark procs. Thus we reserve a few for well known clients. */ +/* (This is necessary if mark descriptors are compiler generated.) */ +#define GC_RESERVED_MARK_PROCS 8 +# define GC_GCJ_RESERVED_MARK_PROC_INDEX 0 + +/* Object descriptors on mark stack or in objects. Low order two */ +/* bits are tags distinguishing among the following 4 possibilities */ +/* for the high order 30 bits. */ +#define GC_DS_TAG_BITS 2 +#define GC_DS_TAGS ((1 << GC_DS_TAG_BITS) - 1) +#define GC_DS_LENGTH 0 /* The entire word is a length in bytes that */ + /* must be a multiple of 4. */ +#define GC_DS_BITMAP 1 /* 30 (62) bits are a bitmap describing pointer */ + /* fields. The msb is 1 iff the first word */ + /* is a pointer. */ + /* (This unconventional ordering sometimes */ + /* makes the marker slightly faster.) */ + /* Zeroes indicate definite nonpointers. Ones */ + /* indicate possible pointers. */ + /* Only usable if pointers are word aligned. */ +#define GC_DS_PROC 2 + /* The objects referenced by this object can be */ + /* pushed on the mark stack by invoking */ + /* PROC(descr). ENV(descr) is passed as the */ + /* last argument. */ +# define GC_MAKE_PROC(proc_index, env) \ + (((((env) << GC_LOG_MAX_MARK_PROCS) \ + | (proc_index)) << GC_DS_TAG_BITS) | GC_DS_PROC) +#define GC_DS_PER_OBJECT 3 /* The real descriptor is at the */ + /* byte displacement from the beginning of the */ + /* object given by descr & ~DS_TAGS */ + /* If the descriptor is negative, the real */ + /* descriptor is at (*<object_start>) - */ + /* (descr & ~DS_TAGS) - GC_INDIR_PER_OBJ_BIAS */ + /* The latter alternative can be used if each */ + /* object contains a type descriptor in the */ + /* first word. */ + /* Note that in multithreaded environments */ + /* per object descriptors maust be located in */ + /* either the first two or last two words of */ + /* the object, since only those are guaranteed */ + /* to be cleared while the allocation lock is */ + /* held. */ +#define GC_INDIR_PER_OBJ_BIAS 0x10 + +extern GC_PTR GC_least_plausible_heap_addr; +extern GC_PTR GC_greatest_plausible_heap_addr; + /* Bounds on the heap. Guaranteed valid */ + /* Likely to include future heap expansion. */ + +/* Handle nested references in a custom mark procedure. */ +/* Check if obj is a valid object. If so, ensure that it is marked. */ +/* If it was not previously marked, push its contents onto the mark */ +/* stack for future scanning. The object will then be scanned using */ +/* its mark descriptor. */ +/* Returns the new mark stack pointer. */ +/* Handles mark stack overflows correctly. */ +/* Since this marks first, it makes progress even if there are mark */ +/* stack overflows. */ +/* Src is the address of the pointer to obj, which is used only */ +/* for back pointer-based heap debugging. */ +/* It is strongly recommended that most objects be handled without mark */ +/* procedures, e.g. with bitmap descriptors, and that mark procedures */ +/* be reserved for exceptional cases. That will ensure that */ +/* performance of this call is not extremely performance critical. */ +/* (Otherwise we would need to inline GC_mark_and_push completely, */ +/* which would tie the client code to a fixed colllector version.) */ +struct GC_ms_entry *GC_mark_and_push + GC_PROTO((GC_PTR obj, + struct GC_ms_entry * mark_stack_ptr, + struct GC_ms_entry * mark_stack_limit, GC_PTR *src)); + +#define GC_MARK_AND_PUSH(obj, msp, lim, src) \ + (((GC_word)obj >= (GC_word)GC_least_plausible_heap_addr && \ + (GC_word)obj <= (GC_word)GC_greatest_plausible_heap_addr)? \ + GC_mark_and_push(obj, msp, lim, src) : \ + msp) + +#endif /* GC_MARK_H */ + |