Handle IND_STATIC in isRetainer
[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 "PosixSource.h"
11 #include "Rts.h"
12
13 #include "GC.h"
14 #include "Storage.h"
15 #include "Compact.h"
16 #include "Task.h"
17 #include "Capability.h"
18 #include "Trace.h"
19 #include "Schedule.h"
20 // DO NOT include "GCThread.h", we don't want the register variable
21
22 /* -----------------------------------------------------------------------------
23 isAlive determines whether the given closure is still alive (after
24 a garbage collection) or not. It returns the new address of the
25 closure if it is alive, or NULL otherwise.
26
27 NOTE: Use it before compaction only!
28 It untags and (if needed) retags pointers to closures.
29 -------------------------------------------------------------------------- */
30
31 StgClosure *
32 isAlive(StgClosure *p)
33 {
34 const StgInfoTable *info;
35 bdescr *bd;
36 StgWord tag;
37 StgClosure *q;
38
39 while (1) {
40 /* The tag and the pointer are split, to be merged later when needed. */
41 tag = GET_CLOSURE_TAG(p);
42 q = UNTAG_CLOSURE(p);
43
44 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
45
46 // ignore static closures
47 //
48 // ToDo: This means we never look through IND_STATIC, which means
49 // isRetainer needs to handle the IND_STATIC case rather than
50 // raising an error.
51 //
52 // ToDo: for static closures, check the static link field.
53 // Problem here is that we sometimes don't set the link field, eg.
54 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
55 //
56 if (!HEAP_ALLOCED_GC(q)) {
57 return p;
58 }
59
60 // ignore closures in generations that we're not collecting.
61 bd = Bdescr((P_)q);
62
63 // if it's a pointer into to-space, then we're done
64 if (bd->flags & BF_EVACUATED) {
65 return p;
66 }
67
68 // large objects use the evacuated flag
69 if (bd->flags & BF_LARGE) {
70 if (get_itbl(q)->type == TSO &&
71 ((StgTSO *)p)->what_next == ThreadRelocated) {
72 p = (StgClosure *)((StgTSO *)p)->_link;
73 continue;
74 }
75 return NULL;
76 }
77
78 // check the mark bit for compacted steps
79 if ((bd->flags & BF_MARKED) && is_marked((P_)q,bd)) {
80 return p;
81 }
82
83 info = q->header.info;
84
85 if (IS_FORWARDING_PTR(info)) {
86 // alive!
87 return (StgClosure*)UN_FORWARDING_PTR(info);
88 }
89
90 info = INFO_PTR_TO_STRUCT(info);
91
92 switch (info->type) {
93
94 case IND:
95 case IND_STATIC:
96 case IND_PERM:
97 // follow indirections
98 p = ((StgInd *)q)->indirectee;
99 continue;
100
101 case TSO:
102 if (((StgTSO *)q)->what_next == ThreadRelocated) {
103 p = (StgClosure *)((StgTSO *)q)->_link;
104 continue;
105 }
106 return NULL;
107
108 default:
109 // dead.
110 return NULL;
111 }
112 }
113 }
114
115 /* -----------------------------------------------------------------------------
116 Reverting CAFs
117 -------------------------------------------------------------------------- */
118
119 void
120 revertCAFs( void )
121 {
122 StgIndStatic *c;
123
124 for (c = (StgIndStatic *)revertible_caf_list;
125 c != (StgIndStatic *)END_OF_STATIC_LIST;
126 c = (StgIndStatic *)c->static_link)
127 {
128 SET_INFO(c, c->saved_info);
129 c->saved_info = NULL;
130 // could, but not necessary: c->static_link = NULL;
131 }
132 revertible_caf_list = END_OF_STATIC_LIST;
133 }
134
135 void
136 markCAFs (evac_fn evac, void *user)
137 {
138 StgIndStatic *c;
139
140 for (c = (StgIndStatic *)caf_list;
141 c != (StgIndStatic*)END_OF_STATIC_LIST;
142 c = (StgIndStatic *)c->static_link)
143 {
144 evac(user, &c->indirectee);
145 }
146 for (c = (StgIndStatic *)revertible_caf_list;
147 c != (StgIndStatic*)END_OF_STATIC_LIST;
148 c = (StgIndStatic *)c->static_link)
149 {
150 evac(user, &c->indirectee);
151 }
152 }