The Battle for Wesnoth  1.15.12+dev
lgc.h
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1 /*
2 ** $Id: lgc.h $
3 ** Garbage Collector
4 ** See Copyright Notice in lua.h
5 */
6 
7 #ifndef lgc_h
8 #define lgc_h
9 
10 
11 #include "lobject.h"
12 #include "lstate.h"
13 
14 /*
15 ** Collectable objects may have one of three colors: white, which means
16 ** the object is not marked; gray, which means the object is marked, but
17 ** its references may be not marked; and black, which means that the
18 ** object and all its references are marked. The main invariant of the
19 ** garbage collector, while marking objects, is that a black object can
20 ** never point to a white one. Moreover, any gray object must be in a
21 ** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it
22 ** can be visited again before finishing the collection cycle. (Open
23 ** upvalues are an exception to this rule.) These lists have no meaning
24 ** when the invariant is not being enforced (e.g., sweep phase).
25 */
26 
27 
28 /*
29 ** Possible states of the Garbage Collector
30 */
31 #define GCSpropagate 0
32 #define GCSenteratomic 1
33 #define GCSatomic 2
34 #define GCSswpallgc 3
35 #define GCSswpfinobj 4
36 #define GCSswptobefnz 5
37 #define GCSswpend 6
38 #define GCScallfin 7
39 #define GCSpause 8
40 
41 
42 #define issweepphase(g) \
43  (GCSswpallgc <= (g)->gcstate && (g)->gcstate <= GCSswpend)
44 
45 
46 /*
47 ** macro to tell when main invariant (white objects cannot point to black
48 ** ones) must be kept. During a collection, the sweep
49 ** phase may break the invariant, as objects turned white may point to
50 ** still-black objects. The invariant is restored when sweep ends and
51 ** all objects are white again.
52 */
53 
54 #define keepinvariant(g) ((g)->gcstate <= GCSatomic)
55 
56 
57 /*
58 ** some useful bit tricks
59 */
60 #define resetbits(x,m) ((x) &= cast_byte(~(m)))
61 #define setbits(x,m) ((x) |= (m))
62 #define testbits(x,m) ((x) & (m))
63 #define bitmask(b) (1<<(b))
64 #define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2))
65 #define l_setbit(x,b) setbits(x, bitmask(b))
66 #define resetbit(x,b) resetbits(x, bitmask(b))
67 #define testbit(x,b) testbits(x, bitmask(b))
68 
69 
70 /*
71 ** Layout for bit use in 'marked' field. First three bits are
72 ** used for object "age" in generational mode. Last bit is used
73 ** by tests.
74 */
75 #define WHITE0BIT 3 /* object is white (type 0) */
76 #define WHITE1BIT 4 /* object is white (type 1) */
77 #define BLACKBIT 5 /* object is black */
78 #define FINALIZEDBIT 6 /* object has been marked for finalization */
79 
80 #define TESTBIT 7
81 
82 
83 
84 #define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT)
85 
86 
87 #define iswhite(x) testbits((x)->marked, WHITEBITS)
88 #define isblack(x) testbit((x)->marked, BLACKBIT)
89 #define isgray(x) /* neither white nor black */ \
90  (!testbits((x)->marked, WHITEBITS | bitmask(BLACKBIT)))
91 
92 #define tofinalize(x) testbit((x)->marked, FINALIZEDBIT)
93 
94 #define otherwhite(g) ((g)->currentwhite ^ WHITEBITS)
95 #define isdeadm(ow,m) ((m) & (ow))
96 #define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)
97 
98 #define changewhite(x) ((x)->marked ^= WHITEBITS)
99 #define nw2black(x) \
100  check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))
101 
102 #define luaC_white(g) cast_byte((g)->currentwhite & WHITEBITS)
103 
104 
105 /* object age in generational mode */
106 #define G_NEW 0 /* created in current cycle */
107 #define G_SURVIVAL 1 /* created in previous cycle */
108 #define G_OLD0 2 /* marked old by frw. barrier in this cycle */
109 #define G_OLD1 3 /* first full cycle as old */
110 #define G_OLD 4 /* really old object (not to be visited) */
111 #define G_TOUCHED1 5 /* old object touched this cycle */
112 #define G_TOUCHED2 6 /* old object touched in previous cycle */
113 
114 #define AGEBITS 7 /* all age bits (111) */
115 
116 #define getage(o) ((o)->marked & AGEBITS)
117 #define setage(o,a) ((o)->marked = cast_byte(((o)->marked & (~AGEBITS)) | a))
118 #define isold(o) (getage(o) > G_SURVIVAL)
119 
120 #define changeage(o,f,t) \
121  check_exp(getage(o) == (f), (o)->marked ^= ((f)^(t)))
122 
123 
124 /* Default Values for GC parameters */
125 #define LUAI_GENMAJORMUL 100
126 #define LUAI_GENMINORMUL 20
127 
128 /* wait memory to double before starting new cycle */
129 #define LUAI_GCPAUSE 200
130 
131 /*
132 ** some gc parameters are stored divided by 4 to allow a maximum value
133 ** up to 1023 in a 'lu_byte'.
134 */
135 #define getgcparam(p) ((p) * 4)
136 #define setgcparam(p,v) ((p) = (v) / 4)
137 
138 #define LUAI_GCMUL 100
139 
140 /* how much to allocate before next GC step (log2) */
141 #define LUAI_GCSTEPSIZE 13 /* 8 KB */
142 
143 
144 /*
145 ** Check whether the declared GC mode is generational. While in
146 ** generational mode, the collector can go temporarily to incremental
147 ** mode to improve performance. This is signaled by 'g->lastatomic != 0'.
148 */
149 #define isdecGCmodegen(g) (g->gckind == KGC_GEN || g->lastatomic != 0)
150 
151 /*
152 ** Does one step of collection when debt becomes positive. 'pre'/'pos'
153 ** allows some adjustments to be done only when needed. macro
154 ** 'condchangemem' is used only for heavy tests (forcing a full
155 ** GC cycle on every opportunity)
156 */
157 #define luaC_condGC(L,pre,pos) \
158  { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
159  condchangemem(L,pre,pos); }
160 
161 /* more often than not, 'pre'/'pos' are empty */
162 #define luaC_checkGC(L) luaC_condGC(L,(void)0,(void)0)
163 
164 
165 #define luaC_barrier(L,p,v) ( \
166  (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
167  luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
168 
169 #define luaC_barrierback(L,p,v) ( \
170  (iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
171  luaC_barrierback_(L,p) : cast_void(0))
172 
173 #define luaC_objbarrier(L,p,o) ( \
174  (isblack(p) && iswhite(o)) ? \
175  luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
176 
177 LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
179 LUAI_FUNC void luaC_step (lua_State *L);
180 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
181 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
182 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
186 LUAI_FUNC void luaC_changemode (lua_State *L, int newmode);
187 
188 
189 #endif
Definition: lobject.h:714
#define LUAI_FUNC
Definition: luaconf.h:307
LUAI_FUNC void luaC_runtilstate(lua_State *L, int statesmask)
Definition: lgc.cpp:1631
LUAI_FUNC void luaC_fix(lua_State *L, GCObject *o)
Definition: lgc.cpp:243
LUAI_FUNC GCObject * luaC_newobj(lua_State *L, int tt, size_t sz)
Definition: lgc.cpp:258
LUAI_FUNC void luaC_step(lua_State *L)
Definition: lgc.cpp:1666
LUAI_FUNC void luaC_changemode(lua_State *L, int newmode)
Definition: lgc.cpp:1323
LUAI_FUNC void luaC_checkfinalizer(lua_State *L, GCObject *o, Table *mt)
Definition: lgc.cpp:1011
LUAI_FUNC void luaC_freeallobjects(lua_State *L)
Definition: lgc.cpp:1503
LUAI_FUNC void luaC_fullgc(lua_State *L, int isemergency)
Definition: lgc.cpp:1703
LUAI_FUNC void luaC_barrierback_(lua_State *L, GCObject *o)
Definition: lgc.cpp:230
LUAI_FUNC void luaC_barrier_(lua_State *L, GCObject *o, GCObject *v)
Definition: lgc.cpp:208