Annotation of OpenXM_contrib2/asir2000/gc/include/gc_mark.h, Revision 1.4
1.1 noro 1: /*
2: * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
3: * Copyright (c) 2001 by Hewlett-Packard Company. 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: */
15:
16: /*
17: * This contains interfaces to the GC marker that are likely to be useful to
18: * clients that provide detailed heap layout information to the collector.
19: * This interface should not be used by normal C or C++ clients.
20: * It will be useful to runtimes for other languages.
21: *
22: * Note that this file is not "namespace-clean", i.e. it introduces names
23: * not prefixed with GC_, which may collide with the client's names. It
24: * should be included only in those few places that directly provide
25: * information to the collector.
26: */
27: #ifndef GC_MARK_H
28: # define GC_MARK_H
29:
30: # ifndef GC_H
31: # include "gc.h"
32: # endif
33:
34: /* A client supplied mark procedure. Returns new mark stack pointer. */
35: /* Primary effect should be to push new entries on the mark stack. */
36: /* Mark stack pointer values are passed and returned explicitly. */
37: /* Global variables decribing mark stack are not necessarily valid. */
38: /* (This usually saves a few cycles by keeping things in registers.) */
39: /* Assumed to scan about GC_PROC_BYTES on average. If it needs to do */
40: /* much more work than that, it should do it in smaller pieces by */
41: /* pushing itself back on the mark stack. */
42: /* Note that it should always do some work (defined as marking some */
43: /* objects) before pushing more than one entry on the mark stack. */
44: /* This is required to ensure termination in the event of mark stack */
45: /* overflows. */
46: /* This procedure is always called with at least one empty entry on the */
47: /* mark stack. */
48: /* Currently we require that mark procedures look for pointers in a */
49: /* subset of the places the conservative marker would. It must be safe */
50: /* to invoke the normal mark procedure instead. */
51: /* WARNING: Such a mark procedure may be invoked on an unused object */
52: /* residing on a free list. Such objects are cleared, except for a */
53: /* free list link field in the first word. Thus mark procedures may */
54: /* not count on the presence of a type descriptor, and must handle this */
55: /* case correctly somehow. */
56: # define GC_PROC_BYTES 100
57: struct GC_ms_entry;
58: typedef struct GC_ms_entry * (*GC_mark_proc) GC_PROTO((
59: GC_word * addr, struct GC_ms_entry * mark_stack_ptr,
60: struct GC_ms_entry * mark_stack_limit, GC_word env));
61:
62: # define GC_LOG_MAX_MARK_PROCS 6
63: # define GC_MAX_MARK_PROCS (1 << GC_LOG_MAX_MARK_PROCS)
64:
65: /* In a few cases it's necessary to assign statically known indices to */
66: /* certain mark procs. Thus we reserve a few for well known clients. */
67: /* (This is necessary if mark descriptors are compiler generated.) */
68: #define GC_RESERVED_MARK_PROCS 8
69: # define GC_GCJ_RESERVED_MARK_PROC_INDEX 0
70:
71: /* Object descriptors on mark stack or in objects. Low order two */
72: /* bits are tags distinguishing among the following 4 possibilities */
73: /* for the high order 30 bits. */
74: #define GC_DS_TAG_BITS 2
75: #define GC_DS_TAGS ((1 << GC_DS_TAG_BITS) - 1)
76: #define GC_DS_LENGTH 0 /* The entire word is a length in bytes that */
77: /* must be a multiple of 4. */
78: #define GC_DS_BITMAP 1 /* 30 (62) bits are a bitmap describing pointer */
79: /* fields. The msb is 1 iff the first word */
80: /* is a pointer. */
81: /* (This unconventional ordering sometimes */
82: /* makes the marker slightly faster.) */
83: /* Zeroes indicate definite nonpointers. Ones */
84: /* indicate possible pointers. */
85: /* Only usable if pointers are word aligned. */
86: #define GC_DS_PROC 2
87: /* The objects referenced by this object can be */
88: /* pushed on the mark stack by invoking */
89: /* PROC(descr). ENV(descr) is passed as the */
90: /* last argument. */
91: # define GC_MAKE_PROC(proc_index, env) \
92: (((((env) << GC_LOG_MAX_MARK_PROCS) \
93: | (proc_index)) << GC_DS_TAG_BITS) | GC_DS_PROC)
94: #define GC_DS_PER_OBJECT 3 /* The real descriptor is at the */
95: /* byte displacement from the beginning of the */
96: /* object given by descr & ~DS_TAGS */
97: /* If the descriptor is negative, the real */
98: /* descriptor is at (*<object_start>) - */
99: /* (descr & ~DS_TAGS) - GC_INDIR_PER_OBJ_BIAS */
100: /* The latter alternative can be used if each */
101: /* object contains a type descriptor in the */
102: /* first word. */
103: /* Note that in multithreaded environments */
104: /* per object descriptors maust be located in */
105: /* either the first two or last two words of */
106: /* the object, since only those are guaranteed */
107: /* to be cleared while the allocation lock is */
108: /* held. */
109: #define GC_INDIR_PER_OBJ_BIAS 0x10
110:
111: extern GC_PTR GC_least_plausible_heap_addr;
112: extern GC_PTR GC_greatest_plausible_heap_addr;
113: /* Bounds on the heap. Guaranteed valid */
114: /* Likely to include future heap expansion. */
115:
116: /* Handle nested references in a custom mark procedure. */
117: /* Check if obj is a valid object. If so, ensure that it is marked. */
118: /* If it was not previously marked, push its contents onto the mark */
119: /* stack for future scanning. The object will then be scanned using */
120: /* its mark descriptor. */
121: /* Returns the new mark stack pointer. */
122: /* Handles mark stack overflows correctly. */
123: /* Since this marks first, it makes progress even if there are mark */
124: /* stack overflows. */
125: /* Src is the address of the pointer to obj, which is used only */
126: /* for back pointer-based heap debugging. */
127: /* It is strongly recommended that most objects be handled without mark */
128: /* procedures, e.g. with bitmap descriptors, and that mark procedures */
129: /* be reserved for exceptional cases. That will ensure that */
130: /* performance of this call is not extremely performance critical. */
131: /* (Otherwise we would need to inline GC_mark_and_push completely, */
1.4 ! noro 132: /* which would tie the client code to a fixed collector version.) */
! 133: /* Note that mark procedures should explicitly call FIXUP_POINTER() */
! 134: /* if required. */
1.1 noro 135: struct GC_ms_entry *GC_mark_and_push
136: GC_PROTO((GC_PTR obj,
137: struct GC_ms_entry * mark_stack_ptr,
138: struct GC_ms_entry * mark_stack_limit, GC_PTR *src));
139:
140: #define GC_MARK_AND_PUSH(obj, msp, lim, src) \
141: (((GC_word)obj >= (GC_word)GC_least_plausible_heap_addr && \
142: (GC_word)obj <= (GC_word)GC_greatest_plausible_heap_addr)? \
143: GC_mark_and_push(obj, msp, lim, src) : \
144: msp)
145:
146: #endif /* GC_MARK_H */
147:
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