Experimental "mark-region" strategy for the old generation
[ghc.git] / rts / sm / GCAux.c
1 /* -----------------------------------------------------------------------------
2 *
3 * (c) The GHC Team 1998-2008
4 *
5 * Functions called from outside the GC need to be separate from GC.c,
6 * because GC.c is compiled with register variable(s).
7 *
8 * ---------------------------------------------------------------------------*/
9
10 #include "Rts.h"
11 #include "Storage.h"
12 #include "MBlock.h"
13 #include "GC.h"
14 #include "Compact.h"
15 #include "Task.h"
16 #include "Capability.h"
17 #include "Trace.h"
18 #include "Schedule.h"
19 // DO NOT include "GCThread.h", we don't want the register variable
20
21 /* -----------------------------------------------------------------------------
22 isAlive determines whether the given closure is still alive (after
23 a garbage collection) or not. It returns the new address of the
24 closure if it is alive, or NULL otherwise.
25
26 NOTE: Use it before compaction only!
27 It untags and (if needed) retags pointers to closures.
28 -------------------------------------------------------------------------- */
29
30 StgClosure *
31 isAlive(StgClosure *p)
32 {
33 const StgInfoTable *info;
34 bdescr *bd;
35 StgWord tag;
36 StgClosure *q;
37
38 while (1) {
39 /* The tag and the pointer are split, to be merged later when needed. */
40 tag = GET_CLOSURE_TAG(p);
41 q = UNTAG_CLOSURE(p);
42
43 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
44
45 // ignore static closures
46 //
47 // ToDo: for static closures, check the static link field.
48 // Problem here is that we sometimes don't set the link field, eg.
49 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
50 //
51 if (!HEAP_ALLOCED(q)) {
52 return p;
53 }
54
55 // ignore closures in generations that we're not collecting.
56 bd = Bdescr((P_)q);
57
58 // if it's a pointer into to-space, then we're done
59 if (bd->flags & BF_EVACUATED) {
60 return p;
61 }
62
63 // large objects use the evacuated flag
64 if (bd->flags & BF_LARGE) {
65 if (get_itbl(q)->type == TSO &&
66 ((StgTSO *)p)->what_next == ThreadRelocated) {
67 p = (StgClosure *)((StgTSO *)p)->_link;
68 continue;
69 }
70 return NULL;
71 }
72
73 // check the mark bit for compacted steps
74 if ((bd->flags & BF_MARKED) && is_marked((P_)q,bd)) {
75 return p;
76 }
77
78 info = q->header.info;
79
80 if (IS_FORWARDING_PTR(info)) {
81 // alive!
82 return (StgClosure*)UN_FORWARDING_PTR(info);
83 }
84
85 info = INFO_PTR_TO_STRUCT(info);
86
87 switch (info->type) {
88
89 case IND:
90 case IND_STATIC:
91 case IND_PERM:
92 case IND_OLDGEN: // rely on compatible layout with StgInd
93 case IND_OLDGEN_PERM:
94 // follow indirections
95 p = ((StgInd *)q)->indirectee;
96 continue;
97
98 case TSO:
99 if (((StgTSO *)q)->what_next == ThreadRelocated) {
100 p = (StgClosure *)((StgTSO *)q)->_link;
101 continue;
102 }
103 return NULL;
104
105 default:
106 // dead.
107 return NULL;
108 }
109 }
110 }
111
112 /* -----------------------------------------------------------------------------
113 Reverting CAFs
114 -------------------------------------------------------------------------- */
115
116 void
117 revertCAFs( void )
118 {
119 StgIndStatic *c;
120
121 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
122 c = (StgIndStatic *)c->static_link)
123 {
124 SET_INFO(c, c->saved_info);
125 c->saved_info = NULL;
126 // could, but not necessary: c->static_link = NULL;
127 }
128 revertible_caf_list = NULL;
129 }
130
131 void
132 markCAFs (evac_fn evac, void *user)
133 {
134 StgIndStatic *c;
135
136 for (c = (StgIndStatic *)caf_list; c != NULL;
137 c = (StgIndStatic *)c->static_link)
138 {
139 evac(user, &c->indirectee);
140 }
141 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
142 c = (StgIndStatic *)c->static_link)
143 {
144 evac(user, &c->indirectee);
145 }
146 }