RELEASE LuaJIT-2.0.0-beta1v2.0.0-beta1

1 files changed, 800 insertions, 0 deletions

diff --git a/src/lj_gc.c b/src/lj_gc.c
new file mode 100644
index 00000000..e479b567
--- /dev/null
+++ b/src/lj_gc.c
@@ -0,0 +1,800 @@
+/*
+** Garbage collector.
+** Copyright (C) 2005-2009 Mike Pall. See Copyright Notice in luajit.h
+**
+** Major portions taken verbatim or adapted from the Lua interpreter.
+** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
+*/
+
+#define lj_gc_c
+#define LUA_CORE
+
+#include "lj_obj.h"
+#include "lj_gc.h"
+#include "lj_err.h"
+#include "lj_str.h"
+#include "lj_tab.h"
+#include "lj_func.h"
+#include "lj_udata.h"
+#include "lj_meta.h"
+#include "lj_state.h"
+#include "lj_frame.h"
+#include "lj_trace.h"
+#include "lj_vm.h"
+
+#define GCSTEPSIZE      1024u
+#define GCSWEEPMAX      40
+#define GCSWEEPCOST     10
+#define GCFINALIZECOST  100
+
+/* Macros to set GCobj colors and flags. */
+#define white2gray(x)           ((x)->gch.marked &= cast_byte(~LJ_GC_WHITES))
+#define black2gray(x)           ((x)->gch.marked &= cast_byte(~LJ_GC_BLACK))
+#define gray2black(x)           ((x)->gch.marked |= LJ_GC_BLACK)
+#define makewhite(g, x) \
+  ((x)->gch.marked = ((x)->gch.marked & cast_byte(~LJ_GC_COLORS)) | curwhite(g))
+#define isfinalized(u)          ((u)->marked & LJ_GC_FINALIZED)
+#define markfinalized(u)        ((u)->marked |= LJ_GC_FINALIZED)
+
+/* -- Mark phase ---------------------------------------------------------- */
+
+/* Mark a TValue (if needed). */
+#define gc_marktv(g, tv) \
+  { lua_assert(!tvisgcv(tv) || (~itype(tv) == gcval(tv)->gch.gct)); \
+    if (tviswhite(tv)) gc_mark(g, gcV(tv)); }
+
+/* Mark a GCobj (if needed). */
+#define gc_markobj(g, o) \
+  { if (iswhite(obj2gco(o))) gc_mark(g, obj2gco(o)); }
+
+/* Mark a string object. */
+#define gc_mark_str(s)          ((s)->marked &= cast_byte(~LJ_GC_WHITES))
+
+/* Mark a white GCobj. */
+static void gc_mark(global_State *g, GCobj *o)
+{
+  lua_assert(iswhite(o) && !isdead(g, o));
+  white2gray(o);
+  if (LJ_UNLIKELY(o->gch.gct == ~LJ_TUDATA)) {
+    GCtab *mt = tabref(gco2ud(o)->metatable);
+    gray2black(o);  /* Userdata are never gray. */
+    if (mt) gc_markobj(g, mt);
+    gc_markobj(g, tabref(gco2ud(o)->env));
+  } else if (LJ_UNLIKELY(o->gch.gct == ~LJ_TUPVAL)) {
+    GCupval *uv = gco2uv(o);
+    gc_marktv(g, uv->v);
+    if (uv->closed)
+      gray2black(o);  /* Closed upvalues are never gray. */
+  } else if (o->gch.gct != ~LJ_TSTR) {
+    lua_assert(o->gch.gct == ~LJ_TFUNC || o->gch.gct == ~LJ_TTAB ||
+               o->gch.gct == ~LJ_TTHREAD || o->gch.gct == ~LJ_TPROTO);
+    setgcrefr(o->gch.gclist, g->gc.gray);
+    setgcref(g->gc.gray, o);
+  }
+}
+
+/* Mark the base metatables. */
+static void gc_mark_basemt(global_State *g)
+{
+  int i;
+  for (i = 0; i < BASEMT_MAX; i++)
+    if (tabref(g->basemt[i]) != NULL)
+      gc_markobj(g, tabref(g->basemt[i]));
+}
+
+/* Start a GC cycle and mark the root set. */
+static void gc_mark_start(global_State *g)
+{
+  setgcrefnull(g->gc.gray);
+  setgcrefnull(g->gc.grayagain);
+  setgcrefnull(g->gc.weak);
+  gc_markobj(g, mainthread(g));
+  gc_markobj(g, tabref(mainthread(g)->env));
+  gc_marktv(g, &g->registrytv);
+  gc_mark_basemt(g);
+  g->gc.state = GCSpropagate;
+}
+
+/* Mark open upvalues. */
+static void gc_mark_uv(global_State *g)
+{
+  GCupval *uv;
+  for (uv = uvnext(&g->uvhead); uv != &g->uvhead; uv = uvnext(uv)) {
+    lua_assert(uvprev(uvnext(uv)) == uv && uvnext(uvprev(uv)) == uv);
+    if (isgray(obj2gco(uv)))
+      gc_marktv(g, uv->v);
+  }
+}
+
+/* Mark userdata in mmudata list. */
+static void gc_mark_mmudata(global_State *g)
+{
+  GCobj *root = gcref(g->gc.mmudata);
+  GCobj *u = root;
+  if (u) {
+    do {
+      u = gcnext(u);
+      makewhite(g, u);  /* Could be from previous GC. */
+      gc_mark(g, u);
+    } while (u != root);
+  }
+}
+
+/* Separate userdata which which needs finalization to mmudata list. */
+size_t lj_gc_separateudata(global_State *g, int all)
+{
+  size_t m = 0;
+  GCRef *p = &mainthread(g)->nextgc;
+  GCobj *o;
+  while ((o = gcref(*p)) != NULL) {
+    if (!(iswhite(o) || all) || isfinalized(gco2ud(o))) {
+      p = &o->gch.nextgc;  /* Nothing to do. */
+    } else if (!lj_meta_fastg(g, tabref(gco2ud(o)->metatable), MM_gc)) {
+      markfinalized(gco2ud(o));  /* Done, as there's no __gc metamethod. */
+      p = &o->gch.nextgc;
+    } else {  /* Otherwise move userdata to be finalized to mmudata list. */
+      m += sizeudata(gco2ud(o));
+      markfinalized(gco2ud(o));
+      *p = o->gch.nextgc;
+      if (gcref(g->gc.mmudata)) {  /* Link to end of mmudata list. */
+        GCobj *root = gcref(g->gc.mmudata);
+        setgcrefr(o->gch.nextgc, root->gch.nextgc);
+        setgcref(root->gch.nextgc, o);
+        setgcref(g->gc.mmudata, o);
+      } else {  /* Create circular list. */
+        setgcref(o->gch.nextgc, o);
+        setgcref(g->gc.mmudata, o);
+      }
+    }
+  }
+  return m;
+}
+
+/* -- Propagation phase --------------------------------------------------- */
+
+/* Traverse a table. */
+static int gc_traverse_tab(global_State *g, GCtab *t)
+{
+  int weak = 0;
+  cTValue *mode;
+  GCtab *mt = tabref(t->metatable);
+  if (mt)
+    gc_markobj(g, mt);
+  mode = lj_meta_fastg(g, mt, MM_mode);
+  if (mode && tvisstr(mode)) {  /* Valid __mode field? */
+    const char *modestr = strVdata(mode);
+    int c;
+    while ((c = *modestr++)) {
+      if (c == 'k') weak |= LJ_GC_WEAKKEY;
+      else if (c == 'v') weak |= LJ_GC_WEAKVAL;
+    }
+    if (weak) {  /* Weak tables are cleared in the atomic phase. */
+      t->marked = cast_byte((t->marked & ~LJ_GC_WEAK) | weak);
+      setgcrefr(t->gclist, g->gc.weak);
+      setgcref(g->gc.weak, obj2gco(t));
+    }
+  }
+  if (weak == LJ_GC_WEAK)  /* Nothing to mark if both keys/values are weak. */
+    return 1;
+  if (!(weak & LJ_GC_WEAKVAL)) {  /* Mark array part. */
+    MSize i, asize = t->asize;
+    for (i = 0; i < asize; i++)
+      gc_marktv(g, arrayslot(t, i));
+  }
+  if (t->hmask > 0) {  /* Mark hash part. */
+    Node *node = noderef(t->node);
+    MSize i, hmask = t->hmask;
+    for (i = 0; i <= hmask; i++) {
+      Node *n = &node[i];
+      lua_assert(itype(&n->key) != LJ_TDEADKEY || tvisnil(&n->val));
+      if (!tvisnil(&n->val)) {  /* Mark non-empty slot. */
+        lua_assert(!tvisnil(&n->key));
+        if (!(weak & LJ_GC_WEAKKEY)) gc_marktv(g, &n->key);
+        if (!(weak & LJ_GC_WEAKVAL)) gc_marktv(g, &n->val);
+      } else if (tvisgcv(&n->key)) {  /* Leave GC key in, but mark as dead. */
+        setitype(&n->key, LJ_TDEADKEY);
+      }
+    }
+  }
+  return weak;
+}
+
+/* Traverse a function. */
+static void gc_traverse_func(global_State *g, GCfunc *fn)
+{
+  gc_markobj(g, tabref(fn->c.env));
+  if (isluafunc(fn)) {
+    uint32_t i;
+    lua_assert(fn->l.nupvalues == funcproto(fn)->sizeuv);
+    gc_markobj(g, funcproto(fn));
+    for (i = 0; i < fn->l.nupvalues; i++)  /* Mark Lua function upvalues. */
+      gc_markobj(g, &gcref(fn->l.uvptr[i])->uv);
+  } else {
+    uint32_t i;
+    for (i = 0; i < fn->c.nupvalues; i++)  /* Mark C function upvalues. */
+      gc_marktv(g, &fn->c.upvalue[i]);
+  }
+}
+
+#if LJ_HASJIT
+/* Traverse a trace. */
+static void gc_traverse_trace(global_State *g, Trace *T)
+{
+  IRRef ref;
+  for (ref = T->nk; ref < REF_TRUE; ref++) {
+    IRIns *ir = &T->ir[ref];
+    if (ir->o == IR_KGC)
+      gc_markobj(g, ir_kgc(ir));
+  }
+}
+
+/* The current trace is a GC root while not anchored in the prototype (yet). */
+#define gc_mark_curtrace(g) \
+  { if (G2J(g)->state != LJ_TRACE_IDLE && G2J(g)->curtrace != 0) \
+    gc_traverse_trace(g, &G2J(g)->cur); }
+#else
+#define gc_mark_curtrace(g)     UNUSED(g)
+#endif
+
+/* Traverse a prototype. */
+static void gc_traverse_proto(global_State *g, GCproto *pt)
+{
+  ptrdiff_t i;
+#if LJ_HASJIT
+  jit_State *J = G2J(g);
+  TraceNo root, side;
+  /* Mark all root traces and attached side traces. */
+  for (root = pt->trace; root != 0; root = J->trace[root]->nextroot) {
+    for (side = J->trace[root]->nextside; side != 0;
+         side = J->trace[side]->nextside)
+      gc_traverse_trace(g, J->trace[side]);
+    gc_traverse_trace(g, J->trace[root]);
+  }
+#endif
+  /* GC during prototype creation could cause NULL fields. */
+  if (pt->chunkname)
+    gc_mark_str(pt->chunkname);
+  for (i = -(ptrdiff_t)pt->sizekgc; i < 0; i++)  /* Mark collectable consts. */
+    gc_markobj(g, gcref(pt->k.gc[i]));
+  for (i = 0; i < (ptrdiff_t)pt->sizeuvname; i++)  /* Mark upvalue names. */
+    if (pt->uvname[i])
+      gc_mark_str(pt->uvname[i]);
+  for (i = 0; i < (ptrdiff_t)pt->sizevarinfo; i++)  /* Mark names of locals. */
+    if (pt->varinfo[i].name)
+      gc_mark_str(pt->varinfo[i].name);
+}
+
+/* Traverse the frame structure of a stack. */
+static TValue *gc_traverse_frames(global_State *g, lua_State *th)
+{
+  TValue *frame, *top = th->top-1;
+  /* Note: extra vararg frame not skipped, marks function twice (harmless). */
+  for (frame = th->base-1; frame > th->stack; frame = frame_prev(frame)) {
+    GCfunc *fn = frame_func(frame);
+    TValue *ftop = frame;
+    if (isluafunc(fn)) ftop += funcproto(fn)->framesize;
+    if (ftop > top) top = ftop;
+    gc_markobj(g, frame_gc(frame));  /* Need to mark hidden function (or L). */
+  }
+  top++;  /* Correct bias of -1 (frame == base-1). */
+  if (top > th->maxstack) top = th->maxstack;
+  return top;
+}
+
+/* Traverse a thread object. */
+static void gc_traverse_thread(global_State *g, lua_State *th)
+{
+  TValue *o, *lim;
+  gc_markobj(g, tabref(th->env));
+  for (o = th->stack+1; o < th->top; o++)
+    gc_marktv(g, o);
+  lim = gc_traverse_frames(g, th);
+  /* Extra cleanup required to avoid this marking problem:
+  **
+  ** [aa[bb.X|   X created.
+  ** [aa[cc|     GC called from (small) inner frame, X destroyed.
+  ** [aa....X.|  GC called again in (larger) outer frame, X resurrected (ouch).
+  **
+  ** During GC in step 2 the stack must be cleaned up to the max. frame extent:
+  **
+  **       ***|  Slots cleaned
+  **    [cc|      from top of last frame
+  ** [aa......|   to max. frame extent.
+  */
+  for (; o <= lim; o++)
+    setnilV(o);
+  lj_state_shrinkstack(th, (MSize)(lim - th->stack));
+}
+
+/* Propagate one gray object. Traverse it and turn it black. */
+static size_t propagatemark(global_State *g)
+{
+  GCobj *o = gcref(g->gc.gray);
+  lua_assert(isgray(o));
+  gray2black(o);
+  setgcrefr(g->gc.gray, o->gch.gclist);  /* Remove from gray list. */
+  if (LJ_LIKELY(o->gch.gct == ~LJ_TTAB)) {
+    GCtab *t = gco2tab(o);
+    if (gc_traverse_tab(g, t))
+      black2gray(o);  /* Keep weak tables gray. */
+    return sizeof(GCtab) + sizeof(TValue) * t->asize +
+                           sizeof(Node) * (t->hmask + 1);
+  } else if (LJ_LIKELY(o->gch.gct == ~LJ_TFUNC)) {
+    GCfunc *fn = gco2func(o);
+    gc_traverse_func(g, fn);
+    return isluafunc(fn) ? sizeLfunc((MSize)fn->l.nupvalues) :
+                           sizeCfunc((MSize)fn->c.nupvalues);
+  } else if (LJ_LIKELY(o->gch.gct == ~LJ_TPROTO)) {
+    GCproto *pt = gco2pt(o);
+    gc_traverse_proto(g, pt);
+    return sizeof(GCproto) + sizeof(BCIns) * pt->sizebc +
+                             sizeof(GCobj *) * pt->sizekgc +
+                             sizeof(lua_Number) * pt->sizekn +
+                             sizeof(int16_t) * pt->sizeuv +
+                             sizeof(int32_t) * pt->sizelineinfo +
+                             sizeof(VarInfo) * pt->sizevarinfo +
+                             sizeof(GCstr *) * pt->sizeuvname;
+  } else {
+    lua_State *th = gco2th(o);
+    setgcrefr(th->gclist, g->gc.grayagain);
+    setgcref(g->gc.grayagain, o);
+    black2gray(o);  /* Threads are never black. */
+    gc_traverse_thread(g, th);
+    return sizeof(lua_State) + sizeof(TValue) * th->stacksize;
+  }
+}
+
+/* Propagate all gray objects. */
+static size_t gc_propagate_gray(global_State *g)
+{
+  size_t m = 0;
+  while (gcref(g->gc.gray) != NULL)
+    m += propagatemark(g);
+  return m;
+}
+
+/* -- Sweep phase --------------------------------------------------------- */
+
+/* Try to shrink some common data structures. */
+static void gc_shrink(global_State *g, lua_State *L)
+{
+  if (g->strnum <= (g->strmask >> 2) && g->strmask > LJ_MIN_STRTAB*2-1)
+    lj_str_resize(L, g->strmask >> 1);  /* Shrink string table. */
+  if (g->tmpbuf.sz > LJ_MIN_SBUF*2)
+    lj_str_resizebuf(L, &g->tmpbuf, g->tmpbuf.sz >> 1);  /* Shrink temp buf. */
+}
+
+/* Type of GC free functions. */
+typedef void (LJ_FASTCALL *GCFreeFunc)(global_State *g, GCobj *o);
+
+/* GC free functions for LJ_TSTR .. LJ_TUDATA. ORDER LJ_T */
+static const GCFreeFunc gc_freefunc[] = {
+  (GCFreeFunc)lj_str_free,
+  (GCFreeFunc)lj_func_freeuv,
+  (GCFreeFunc)lj_state_free,
+  (GCFreeFunc)lj_func_freeproto,
+  (GCFreeFunc)lj_func_free,
+  (GCFreeFunc)0,
+  (GCFreeFunc)lj_tab_free,
+  (GCFreeFunc)lj_udata_free
+};
+
+/* Full sweep of a GC list. */
+#define gc_fullsweep(g, p)      gc_sweep(g, (p), LJ_MAX_MEM)
+
+/* Partial sweep of a GC list. */
+static GCRef *gc_sweep(global_State *g, GCRef *p, uint32_t lim)
+{
+  /* Mask with other white and LJ_GC_FIXED. Or LJ_GC_SFIXED on shutdown. */
+  int ow = otherwhite(g);
+  GCobj *o;
+  while ((o = gcref(*p)) != NULL && lim-- > 0) {
+    if (o->gch.gct == ~LJ_TTHREAD)  /* Need to sweep open upvalues, too. */
+      gc_fullsweep(g, &gco2th(o)->openupval);
+    if (((o->gch.marked ^ LJ_GC_WHITES) & ow)) {  /* Black or current white? */
+      lua_assert(!isdead(g, o) || (o->gch.marked & LJ_GC_FIXED));
+      makewhite(g, o);  /* Value is alive, change to the current white. */
+      p = &o->gch.nextgc;
+    } else {  /* Otherwise value is dead, free it. */
+      lua_assert(isdead(g, o) || ow == LJ_GC_SFIXED);
+      setgcrefr(*p, o->gch.nextgc);
+      if (o == gcref(g->gc.root))
+        setgcrefr(g->gc.root, o->gch.nextgc);  /* Adjust list anchor. */
+      gc_freefunc[o->gch.gct - ~LJ_TSTR](g, o);
+    }
+  }
+  return p;
+}
+
+/* Check whether we can clear a key or a value slot from a table. */
+static int gc_mayclear(cTValue *o, int val)
+{
+  if (tvisgcv(o)) {  /* Only collectable objects can be weak references. */
+    if (tvisstr(o)) {  /* But strings cannot be used as weak references. */
+      gc_mark_str(strV(o));  /* And need to be marked. */
+      return 0;
+    }
+    if (iswhite(gcV(o)))
+      return 1;  /* Object is about to be collected. */
+    if (tvisudata(o) && val && isfinalized(udataV(o)))
+      return 1;  /* Finalized userdata is dropped only from values. */
+  }
+  return 0;  /* Cannot clear. */
+}
+
+/* Clear collected entries from weak tables. */
+static void gc_clearweak(GCobj *o)
+{
+  while (o) {
+    GCtab *t = gco2tab(o);
+    lua_assert((t->marked & LJ_GC_WEAK));
+    if ((t->marked & LJ_GC_WEAKVAL)) {
+      MSize i, asize = t->asize;
+      for (i = 0; i < asize; i++) {
+        /* Clear array slot when value is about to be collected. */
+        TValue *tv = arrayslot(t, i);
+        if (gc_mayclear(tv, 1))
+          setnilV(tv);
+      }
+    }
+    if (t->hmask > 0) {
+      Node *node = noderef(t->node);
+      MSize i, hmask = t->hmask;
+      for (i = 0; i <= hmask; i++) {
+        Node *n = &node[i];
+        /* Clear hash slot when key or value is about to be collected. */
+        if (!tvisnil(&n->val) && (gc_mayclear(&n->key, 0) ||
+                                  gc_mayclear(&n->val, 1))) {
+          setnilV(&n->val);
+          if (tvisgcv(&n->key))  /* Leave GC key in, but mark as dead. */
+            setitype(&n->key, LJ_TDEADKEY);
+        }
+      }
+    }
+    o = gcref(t->gclist);
+  }
+}
+
+/* Finalize one userdata object from mmudata list. */
+static void gc_finalize(lua_State *L)
+{
+  global_State *g = G(L);
+  GCobj *o = gcnext(gcref(g->gc.mmudata));
+  GCudata *ud = gco2ud(o);
+  cTValue *mo;
+  /* Unchain from list of userdata to be finalized. */
+  if (o == gcref(g->gc.mmudata))
+    setgcrefnull(g->gc.mmudata);
+  else
+    setgcrefr(gcref(g->gc.mmudata)->gch.nextgc, ud->nextgc);
+  /* Add it back to the main userdata list and make it white. */
+  setgcrefr(ud->nextgc, mainthread(g)->nextgc);
+  setgcref(mainthread(g)->nextgc, o);
+  makewhite(g, o);
+  /* Resolve the __gc metamethod. */
+  mo = lj_meta_fastg(g, tabref(ud->metatable), MM_gc);
+  if (mo) {
+    /* Save and restore lots of state around the __gc callback. */
+    uint8_t oldh = hook_save(g);
+    MSize oldt = g->gc.threshold;
+    GCobj *oldjl = gcref(g->jit_L);
+    MSize oldjs = 0;
+    ptrdiff_t oldjb = 0;
+    int errcode;
+    TValue *top;
+    if (oldjl) {
+      oldjs = gco2th(oldjl)->stacksize;
+      oldjb = savestack(gco2th(oldjl), mref(g->jit_base, TValue ));
+      setgcrefnull(g->jit_L);
+    }
+    lj_trace_abort(g);
+    top = L->top;
+    L->top = top+2;
+    hook_entergc(g);  /* Disable hooks and new traces during __gc. */
+    g->gc.threshold = LJ_MAX_MEM;  /* Prevent GC steps. */
+    copyTV(L, top, mo);
+    setudataV(L, top+1, ud);
+    errcode = lj_vm_pcall(L, top+1, 1+0, -1);  /* Stack: |mo|ud| -> | */
+    hook_restore(g, oldh);
+    g->gc.threshold = oldt;  /* Restore GC threshold. */
+    if (oldjl) {
+      if (gco2th(oldjl)->stacksize < oldjs)
+        lj_state_growstack(gco2th(oldjl), oldjs - gco2th(oldjl)->stacksize);
+      setgcref(g->jit_L, oldjl);
+      setmref(g->jit_base, restorestack(gco2th(oldjl), oldjb));
+    }
+    if (errcode)
+      lj_err_throw(L, errcode);  /* Propagate errors. */
+  }
+}
+
+/* Finalize all userdata objects from mmudata list. */
+void lj_gc_finalizeudata(lua_State *L)
+{
+  while (gcref(G(L)->gc.mmudata) != NULL)
+    gc_finalize(L);
+}
+
+/* Free all remaining GC objects. */
+void lj_gc_freeall(global_State *g)
+{
+  MSize i, strmask;
+  /* Free everything, except super-fixed objects (the main thread). */
+  g->gc.currentwhite = LJ_GC_WHITES | LJ_GC_SFIXED;
+  gc_fullsweep(g, &g->gc.root);
+  strmask = g->strmask;
+  for (i = 0; i <= strmask; i++)  /* Free all string hash chains. */
+    gc_fullsweep(g, &g->strhash[i]);
+}
+
+/* -- Collector ----------------------------------------------------------- */
+
+/* Atomic part of the GC cycle, transitioning from mark to sweep phase. */
+static void atomic(global_State *g, lua_State *L)
+{
+  size_t udsize;
+
+  gc_mark_uv(g);  /* Need to remark open upvalues (the thread may be dead). */
+  gc_propagate_gray(g);  /* Propagate any left-overs. */
+
+  setgcrefr(g->gc.gray, g->gc.weak);  /* Empty the list of weak tables. */
+  setgcrefnull(g->gc.weak);
+  lua_assert(!iswhite(obj2gco(mainthread(g))));
+  gc_markobj(g, L);  /* Mark running thread. */
+  gc_mark_curtrace(g);  /* Mark current trace. */
+  gc_mark_basemt(g);  /* Mark base metatables (again). */
+  gc_propagate_gray(g);  /* Propagate all of the above. */
+
+  setgcrefr(g->gc.gray, g->gc.grayagain);  /* Empty the 2nd chance list. */
+  setgcrefnull(g->gc.grayagain);
+  gc_propagate_gray(g);  /* Propagate it. */
+
+  udsize = lj_gc_separateudata(g, 0);  /* Separate userdata to be finalized. */
+  gc_mark_mmudata(g);  /* Mark them. */
+  udsize += gc_propagate_gray(g);  /* And propagate the marks. */
+
+  /* All marking done, clear weak tables. */
+  gc_clearweak(gcref(g->gc.weak));
+
+  /* Prepare for sweep phase. */
+  g->gc.currentwhite = cast_byte(otherwhite(g));  /* Flip current white. */
+  g->gc.sweepstr = 0;
+  g->gc.sweep = &g->gc.root;
+  g->gc.state = GCSsweepstring;
+  g->gc.estimate = g->gc.total - (MSize)udsize;  /* Initial estimate. */
+}
+
+/* GC state machine. Returns a cost estimate for each step performed. */
+static size_t gc_onestep(lua_State *L)
+{
+  global_State *g = G(L);
+  switch (g->gc.state) {
+  case GCSpause:
+    gc_mark_start(g);  /* Start a new GC cycle by marking all GC roots. */
+    return 0;
+  case GCSpropagate:
+    if (gcref(g->gc.gray) != NULL)
+      return propagatemark(g);  /* Propagate one gray object. */
+    atomic(g, L);  /* End of mark phase. */
+    return 0;
+  case GCSsweepstring: {
+    MSize old = g->gc.total;
+    gc_fullsweep(g, &g->strhash[g->gc.sweepstr++]);  /* Sweep one chain. */
+    if (g->gc.sweepstr > g->strmask)
+      g->gc.state = GCSsweep;  /* All string hash chains sweeped. */
+    lua_assert(old >= g->gc.total);
+    g->gc.estimate -= old - g->gc.total;
+    return GCSWEEPCOST;
+    }
+  case GCSsweep: {
+    MSize old = g->gc.total;
+    g->gc.sweep = gc_sweep(g, g->gc.sweep, GCSWEEPMAX);  /* Partial sweep. */
+    if (gcref(*g->gc.sweep) == NULL) {
+      gc_shrink(g, L);
+      g->gc.state = GCSfinalize;  /* End of sweep phase. */
+    }
+    lua_assert(old >= g->gc.total);
+    g->gc.estimate -= old - g->gc.total;
+    return GCSWEEPMAX*GCSWEEPCOST;
+    }
+  case GCSfinalize:
+    if (gcref(g->gc.mmudata) != NULL) {
+      gc_finalize(L);  /* Finalize one userdata object. */
+      if (g->gc.estimate > GCFINALIZECOST)
+        g->gc.estimate -= GCFINALIZECOST;
+      return GCFINALIZECOST;
+    }
+    g->gc.state = GCSpause;  /* End of GC cycle. */
+    g->gc.debt = 0;
+    return 0;
+  default:
+    lua_assert(0);
+    return 0;
+  }
+}
+
+/* Perform a limited amount of incremental GC steps. */
+int lj_gc_step(lua_State *L)
+{
+  global_State *g = G(L);
+  MSize lim;
+  int32_t ostate = g->vmstate;
+  setvmstate(g, GC);
+  lim = (GCSTEPSIZE/100) * g->gc.stepmul;
+  if (lim == 0)
+    lim = LJ_MAX_MEM;
+  g->gc.debt += g->gc.total - g->gc.threshold;
+  do {
+    lim -= (MSize)gc_onestep(L);
+    if (g->gc.state == GCSpause) {
+      lua_assert(g->gc.total >= g->gc.estimate);
+      g->gc.threshold = (g->gc.estimate/100) * g->gc.pause;
+      g->vmstate = ostate;
+      return 1;  /* Finished a GC cycle. */
+    }
+  } while ((int32_t)lim > 0);
+  if (g->gc.debt < GCSTEPSIZE) {
+    g->gc.threshold = g->gc.total + GCSTEPSIZE;
+  } else {
+    g->gc.debt -= GCSTEPSIZE;
+    g->gc.threshold = g->gc.total;
+  }
+  g->vmstate = ostate;
+  return 0;
+}
+
+/* Ditto, but fix the stack top first. */
+void lj_gc_step_fixtop(lua_State *L)
+{
+  if (curr_funcisL(L)) L->top = curr_topL(L);
+  lj_gc_step(L);
+}
+
+/* Perform multiple GC steps. Called from JIT-compiled code. */
+void lj_gc_step_jit(lua_State *L, const BCIns *pc, MSize steps)
+{
+  cframe_pc(cframe_raw(L->cframe)) = pc;
+  L->top = curr_topL(L);
+  while (steps-- > 0 && lj_gc_step(L) == 0)
+    ;
+}
+
+/* Perform a full GC cycle. */
+void lj_gc_fullgc(lua_State *L)
+{
+  global_State *g = G(L);
+  int32_t ostate = g->vmstate;
+  setvmstate(g, GC);
+  if (g->gc.state <= GCSpropagate) {  /* Caught somewhere in the middle. */
+    g->gc.sweepstr = 0;
+    g->gc.sweep = &g->gc.root;  /* Sweep everything (preserving it). */
+    setgcrefnull(g->gc.gray);  /* Reset lists from partial propagation. */
+    setgcrefnull(g->gc.grayagain);
+    setgcrefnull(g->gc.weak);
+    g->gc.state = GCSsweepstring;  /* Fast forward to the sweep phase. */
+  }
+  lua_assert(g->gc.state != GCSpause && g->gc.state != GCSpropagate);
+  while (g->gc.state != GCSfinalize) {  /* Finish sweep. */
+    lua_assert(g->gc.state == GCSsweepstring || g->gc.state == GCSsweep);
+    gc_onestep(L);
+  }
+  /* Now perform a full GC. */
+  gc_mark_start(g);
+  while (g->gc.state != GCSpause)
+    gc_onestep(L);
+  g->gc.threshold = (g->gc.estimate/100) * g->gc.pause;
+  g->vmstate = ostate;
+}
+
+/* -- Write barriers ------------------------------------------------------ */
+
+/* Move the GC propagation frontier back for tables (make it gray again). */
+void lj_gc_barrierback(global_State *g, GCtab *t)
+{
+  GCobj *o = obj2gco(t);
+  lua_assert(isblack(o) && !isdead(g, o));
+  lua_assert(g->gc.state != GCSfinalize && g->gc.state != GCSpause);
+  black2gray(o);
+  setgcrefr(t->gclist, g->gc.grayagain);
+  setgcref(g->gc.grayagain, o);
+}
+
+/* Move the GC propagation frontier forward. */
+void lj_gc_barrierf(global_State *g, GCobj *o, GCobj *v)
+{
+  lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
+  lua_assert(g->gc.state != GCSfinalize && g->gc.state != GCSpause);
+  lua_assert(o->gch.gct != ~LJ_TTAB);
+  /* Preserve invariant during propagation. Otherwise it doesn't matter. */
+  if (g->gc.state == GCSpropagate)
+    gc_mark(g, v);  /* Move frontier forward. */
+  else
+    makewhite(g, o);  /* Make it white to avoid the following barrier. */
+}
+
+/* The reason for duplicating this is that it needs to be visible from ASM. */
+void lj_gc_barrieruv(global_State *g, GCobj *o, GCobj *v)
+{
+  lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
+  lua_assert(g->gc.state != GCSfinalize && g->gc.state != GCSpause);
+  lua_assert(o->gch.gct == ~LJ_TUPVAL);
+  /* Preserve invariant during propagation. Otherwise it doesn't matter. */
+  if (g->gc.state == GCSpropagate)
+    gc_mark(g, v);  /* Move frontier forward. */
+  else
+    makewhite(g, o);  /* Make it white to avoid the following barrier. */
+}
+
+/* Close upvalue. Also needs a write barrier. */
+void lj_gc_closeuv(global_State *g, GCupval *uv)
+{
+  GCobj *o = obj2gco(uv);
+  /* Copy stack slot to upvalue itself and point to the copy. */
+  copyTV(mainthread(g), &uv->tv, uv->v);
+  uv->v = &uv->tv;
+  uv->closed = 1;
+  setgcrefr(o->gch.nextgc, g->gc.root);
+  setgcref(g->gc.root, o);
+  if (isgray(o)) {  /* A closed upvalue is never gray, so fix this. */
+    if (g->gc.state == GCSpropagate) {
+      gray2black(o);  /* Make it black and preserve invariant. */
+      if (tviswhite(uv->v))
+        lj_gc_barrierf(g, o, gcV(uv->v));
+    } else {
+      makewhite(g, o);  /* Make it white, i.e. sweep the upvalue. */
+      lua_assert(g->gc.state != GCSfinalize && g->gc.state != GCSpause);
+    }
+  }
+}
+
+#if LJ_HASJIT
+/* Mark a trace if it's saved during the propagation phase. */
+void lj_gc_barriertrace(global_State *g, void *T)
+{
+  if (g->gc.state == GCSpropagate)
+    gc_traverse_trace(g, (Trace *)T);
+}
+#endif
+
+/* -- Allocator ----------------------------------------------------------- */
+
+/* Call pluggable memory allocator to allocate or resize a fragment. */
+void *lj_mem_realloc(lua_State *L, void *p, MSize osz, MSize nsz)
+{
+  global_State *g = G(L);
+  lua_assert((osz == 0) == (p == NULL));
+  p = g->allocf(g->allocd, p, osz, nsz);
+  if (p == NULL && nsz > 0)
+    lj_err_throw(L, LUA_ERRMEM);
+  lua_assert((nsz == 0) == (p == NULL));
+  g->gc.total = (g->gc.total - osz) + nsz;
+  return p;
+}
+
+/* Allocate new GC object and link it to the root set. */
+void *lj_mem_newgco(lua_State *L, MSize size)
+{
+  global_State *g = G(L);
+  GCobj *o = (GCobj *)g->allocf(g->allocd, NULL, 0, size);
+  if (o == NULL)
+    lj_err_throw(L, LUA_ERRMEM);
+  g->gc.total += size;
+  setgcrefr(o->gch.nextgc, g->gc.root);
+  setgcref(g->gc.root, o);
+  newwhite(g, o);
+  return o;
+}
+
+/* Resize growable vector. */
+void *lj_mem_grow(lua_State *L, void *p, MSize *szp, MSize lim, MSize esz)
+{
+  MSize sz = (*szp) << 1;
+  if (sz < LJ_MIN_VECSZ)
+    sz = LJ_MIN_VECSZ;
+  if (sz > lim)
+    sz = lim;
+  p = lj_mem_realloc(L, p, (*szp)*esz, sz*esz);
+  *szp = sz;
+  return p;
+}
+