--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/luajit/src/lj_snap.c	Thu Jan 22 20:10:30 2026 -0800
@@ -0,0 +1,996 @@
+/*
+** Snapshot handling.
+** Copyright (C) 2005-2023 Mike Pall. See Copyright Notice in luajit.h
+*/
+
+#define lj_snap_c
+#define LUA_CORE
+
+#include "lj_obj.h"
+
+#if LJ_HASJIT
+
+#include "lj_gc.h"
+#include "lj_tab.h"
+#include "lj_state.h"
+#include "lj_frame.h"
+#include "lj_bc.h"
+#include "lj_ir.h"
+#include "lj_jit.h"
+#include "lj_iropt.h"
+#include "lj_trace.h"
+#include "lj_snap.h"
+#include "lj_target.h"
+#if LJ_HASFFI
+#include "lj_ctype.h"
+#include "lj_cdata.h"
+#endif
+
+/* Pass IR on to next optimization in chain (FOLD). */
+#define emitir(ot, a, b)	(lj_ir_set(J, (ot), (a), (b)), lj_opt_fold(J))
+
+/* Emit raw IR without passing through optimizations. */
+#define emitir_raw(ot, a, b)	(lj_ir_set(J, (ot), (a), (b)), lj_ir_emit(J))
+
+/* -- Snapshot buffer allocation ------------------------------------------ */
+
+/* Grow snapshot buffer. */
+void lj_snap_grow_buf_(jit_State *J, MSize need)
+{
+  MSize maxsnap = (MSize)J->param[JIT_P_maxsnap];
+  if (need > maxsnap)
+    lj_trace_err(J, LJ_TRERR_SNAPOV);
+  lj_mem_growvec(J->L, J->snapbuf, J->sizesnap, maxsnap, SnapShot);
+  J->cur.snap = J->snapbuf;
+}
+
+/* Grow snapshot map buffer. */
+void lj_snap_grow_map_(jit_State *J, MSize need)
+{
+  if (need < 2*J->sizesnapmap)
+    need = 2*J->sizesnapmap;
+  else if (need < 64)
+    need = 64;
+  J->snapmapbuf = (SnapEntry *)lj_mem_realloc(J->L, J->snapmapbuf,
+		    J->sizesnapmap*sizeof(SnapEntry), need*sizeof(SnapEntry));
+  J->cur.snapmap = J->snapmapbuf;
+  J->sizesnapmap = need;
+}
+
+/* -- Snapshot generation ------------------------------------------------- */
+
+/* Add all modified slots to the snapshot. */
+static MSize snapshot_slots(jit_State *J, SnapEntry *map, BCReg nslots)
+{
+  IRRef retf = J->chain[IR_RETF];  /* Limits SLOAD restore elimination. */
+  BCReg s;
+  MSize n = 0;
+  for (s = 0; s < nslots; s++) {
+    TRef tr = J->slot[s];
+    IRRef ref = tref_ref(tr);
+#if LJ_FR2
+    if (s == 1) {  /* Ignore slot 1 in LJ_FR2 mode, except if tailcalled. */
+      if ((tr & TREF_FRAME))
+	map[n++] = SNAP(1, SNAP_FRAME | SNAP_NORESTORE, REF_NIL);
+      continue;
+    }
+    if ((tr & (TREF_FRAME | TREF_CONT)) && !ref) {
+      cTValue *base = J->L->base - J->baseslot;
+      tr = J->slot[s] = (tr & 0xff0000) | lj_ir_k64(J, IR_KNUM, base[s].u64);
+      ref = tref_ref(tr);
+    }
+#endif
+    if (ref) {
+      SnapEntry sn = SNAP_TR(s, tr);
+      IRIns *ir = &J->cur.ir[ref];
+      if ((LJ_FR2 || !(sn & (SNAP_CONT|SNAP_FRAME))) &&
+	  ir->o == IR_SLOAD && ir->op1 == s && ref > retf) {
+	/*
+	** No need to snapshot unmodified non-inherited slots.
+	** But always snapshot the function below a frame in LJ_FR2 mode.
+	*/
+	if (!(ir->op2 & IRSLOAD_INHERIT) &&
+	    (!LJ_FR2 || s == 0 || s+1 == nslots ||
+	     !(J->slot[s+1] & (TREF_CONT|TREF_FRAME))))
+	  continue;
+	/* No need to restore readonly slots and unmodified non-parent slots. */
+	if (!(LJ_DUALNUM && (ir->op2 & IRSLOAD_CONVERT)) &&
+	    (ir->op2 & (IRSLOAD_READONLY|IRSLOAD_PARENT)) != IRSLOAD_PARENT)
+	  sn |= SNAP_NORESTORE;
+      }
+      if (LJ_SOFTFP32 && irt_isnum(ir->t))
+	sn |= SNAP_SOFTFPNUM;
+      map[n++] = sn;
+    }
+  }
+  return n;
+}
+
+/* Add frame links at the end of the snapshot. */
+static MSize snapshot_framelinks(jit_State *J, SnapEntry *map, uint8_t *topslot)
+{
+  cTValue *frame = J->L->base - 1;
+  cTValue *lim = J->L->base - J->baseslot + LJ_FR2;
+  GCfunc *fn = frame_func(frame);
+  cTValue *ftop = isluafunc(fn) ? (frame+funcproto(fn)->framesize) : J->L->top;
+#if LJ_FR2
+  uint64_t pcbase = (u64ptr(J->pc) << 8) | (J->baseslot - 2);
+  lj_assertJ(2 <= J->baseslot && J->baseslot <= 257, "bad baseslot");
+  memcpy(map, &pcbase, sizeof(uint64_t));
+#else
+  MSize f = 0;
+  map[f++] = SNAP_MKPC(J->pc);  /* The current PC is always the first entry. */
+#endif
+  lj_assertJ(!J->pt ||
+	     (J->pc >= proto_bc(J->pt) &&
+	      J->pc < proto_bc(J->pt) + J->pt->sizebc), "bad snapshot PC");
+  while (frame > lim) {  /* Backwards traversal of all frames above base. */
+    if (frame_islua(frame)) {
+#if !LJ_FR2
+      map[f++] = SNAP_MKPC(frame_pc(frame));
+#endif
+      frame = frame_prevl(frame);
+    } else if (frame_iscont(frame)) {
+#if !LJ_FR2
+      map[f++] = SNAP_MKFTSZ(frame_ftsz(frame));
+      map[f++] = SNAP_MKPC(frame_contpc(frame));
+#endif
+      frame = frame_prevd(frame);
+    } else {
+      lj_assertJ(!frame_isc(frame), "broken frame chain");
+#if !LJ_FR2
+      map[f++] = SNAP_MKFTSZ(frame_ftsz(frame));
+#endif
+      frame = frame_prevd(frame);
+      continue;
+    }
+    if (frame + funcproto(frame_func(frame))->framesize > ftop)
+      ftop = frame + funcproto(frame_func(frame))->framesize;
+  }
+  *topslot = (uint8_t)(ftop - lim);
+#if LJ_FR2
+  lj_assertJ(sizeof(SnapEntry) * 2 == sizeof(uint64_t), "bad SnapEntry def");
+  return 2;
+#else
+  lj_assertJ(f == (MSize)(1 + J->framedepth), "miscalculated snapshot size");
+  return f;
+#endif
+}
+
+/* Take a snapshot of the current stack. */
+static void snapshot_stack(jit_State *J, SnapShot *snap, MSize nsnapmap)
+{
+  BCReg nslots = J->baseslot + J->maxslot;
+  MSize nent;
+  SnapEntry *p;
+  /* Conservative estimate. */
+  lj_snap_grow_map(J, nsnapmap + nslots + (MSize)(LJ_FR2?2:J->framedepth+1));
+  p = &J->cur.snapmap[nsnapmap];
+  nent = snapshot_slots(J, p, nslots);
+  snap->nent = (uint8_t)nent;
+  nent += snapshot_framelinks(J, p + nent, &snap->topslot);
+  snap->mapofs = (uint32_t)nsnapmap;
+  snap->ref = (IRRef1)J->cur.nins;
+  snap->mcofs = 0;
+  snap->nslots = (uint8_t)nslots;
+  snap->count = 0;
+  J->cur.nsnapmap = (uint32_t)(nsnapmap + nent);
+}
+
+/* Add or merge a snapshot. */
+void lj_snap_add(jit_State *J)
+{
+  MSize nsnap = J->cur.nsnap;
+  MSize nsnapmap = J->cur.nsnapmap;
+  /* Merge if no ins. inbetween or if requested and no guard inbetween. */
+  if ((nsnap > 0 && J->cur.snap[nsnap-1].ref == J->cur.nins) ||
+      (J->mergesnap && !irt_isguard(J->guardemit))) {
+    if (nsnap == 1) {  /* But preserve snap #0 PC. */
+      emitir_raw(IRT(IR_NOP, IRT_NIL), 0, 0);
+      goto nomerge;
+    }
+    nsnapmap = J->cur.snap[--nsnap].mapofs;
+  } else {
+  nomerge:
+    lj_snap_grow_buf(J, nsnap+1);
+    J->cur.nsnap = (uint16_t)(nsnap+1);
+  }
+  J->mergesnap = 0;
+  J->guardemit.irt = 0;
+  snapshot_stack(J, &J->cur.snap[nsnap], nsnapmap);
+}
+
+/* -- Snapshot modification ----------------------------------------------- */
+
+#define SNAP_USEDEF_SLOTS	(LJ_MAX_JSLOTS+LJ_STACK_EXTRA)
+
+/* Find unused slots with reaching-definitions bytecode data-flow analysis. */
+static BCReg snap_usedef(jit_State *J, uint8_t *udf,
+			 const BCIns *pc, BCReg maxslot)
+{
+  BCReg s;
+  GCobj *o;
+
+  if (maxslot == 0) return 0;
+#ifdef LUAJIT_USE_VALGRIND
+  /* Avoid errors for harmless reads beyond maxslot. */
+  memset(udf, 1, SNAP_USEDEF_SLOTS);
+#else
+  memset(udf, 1, maxslot);
+#endif
+
+  /* Treat open upvalues as used. */
+  o = gcref(J->L->openupval);
+  while (o) {
+    if (uvval(gco2uv(o)) < J->L->base) break;
+    udf[uvval(gco2uv(o)) - J->L->base] = 0;
+    o = gcref(o->gch.nextgc);
+  }
+
+#define USE_SLOT(s)		udf[(s)] &= ~1
+#define DEF_SLOT(s)		udf[(s)] *= 3
+
+  /* Scan through following bytecode and check for uses/defs. */
+  lj_assertJ(pc >= proto_bc(J->pt) && pc < proto_bc(J->pt) + J->pt->sizebc,
+	     "snapshot PC out of range");
+  for (;;) {
+    BCIns ins = *pc++;
+    BCOp op = bc_op(ins);
+    switch (bcmode_b(op)) {
+    case BCMvar: USE_SLOT(bc_b(ins)); break;
+    default: break;
+    }
+    switch (bcmode_c(op)) {
+    case BCMvar: USE_SLOT(bc_c(ins)); break;
+    case BCMrbase:
+      lj_assertJ(op == BC_CAT, "unhandled op %d with RC rbase", op);
+      for (s = bc_b(ins); s <= bc_c(ins); s++) USE_SLOT(s);
+      for (; s < maxslot; s++) DEF_SLOT(s);
+      break;
+    case BCMjump:
+    handle_jump: {
+      BCReg minslot = bc_a(ins);
+      if (op >= BC_FORI && op <= BC_JFORL) minslot += FORL_EXT;
+      else if (op >= BC_ITERL && op <= BC_JITERL) minslot += bc_b(pc[-2])-1;
+      else if (op == BC_UCLO) {
+	ptrdiff_t delta = bc_j(ins);
+	if (delta < 0) return maxslot;  /* Prevent loop. */
+	pc += delta;
+	break;
+      }
+      for (s = minslot; s < maxslot; s++) DEF_SLOT(s);
+      return minslot < maxslot ? minslot : maxslot;
+      }
+    case BCMlit:
+      if (op == BC_JFORL || op == BC_JITERL || op == BC_JLOOP) {
+	goto handle_jump;
+      } else if (bc_isret(op)) {
+	BCReg top = op == BC_RETM ? maxslot : (bc_a(ins) + bc_d(ins)-1);
+	for (s = 0; s < bc_a(ins); s++) DEF_SLOT(s);
+	for (; s < top; s++) USE_SLOT(s);
+	for (; s < maxslot; s++) DEF_SLOT(s);
+	return 0;
+      }
+      break;
+    case BCMfunc: return maxslot;  /* NYI: will abort, anyway. */
+    default: break;
+    }
+    switch (bcmode_a(op)) {
+    case BCMvar: USE_SLOT(bc_a(ins)); break;
+    case BCMdst:
+       if (!(op == BC_ISTC || op == BC_ISFC)) DEF_SLOT(bc_a(ins));
+       break;
+    case BCMbase:
+      if (op >= BC_CALLM && op <= BC_ITERN) {
+	BCReg top = (op == BC_CALLM || op == BC_CALLMT || bc_c(ins) == 0) ?
+		    maxslot : (bc_a(ins) + bc_c(ins)+LJ_FR2);
+	if (LJ_FR2) DEF_SLOT(bc_a(ins)+1);
+	s = bc_a(ins) - ((op == BC_ITERC || op == BC_ITERN) ? 3 : 0);
+	for (; s < top; s++) USE_SLOT(s);
+	for (; s < maxslot; s++) DEF_SLOT(s);
+	if (op == BC_CALLT || op == BC_CALLMT) {
+	  for (s = 0; s < bc_a(ins); s++) DEF_SLOT(s);
+	  return 0;
+	}
+      } else if (op == BC_VARG) {
+	return maxslot;  /* NYI: punt. */
+      } else if (op == BC_KNIL) {
+	for (s = bc_a(ins); s <= bc_d(ins); s++) DEF_SLOT(s);
+      } else if (op == BC_TSETM) {
+	for (s = bc_a(ins)-1; s < maxslot; s++) USE_SLOT(s);
+      }
+      break;
+    default: break;
+    }
+    lj_assertJ(pc >= proto_bc(J->pt) && pc < proto_bc(J->pt) + J->pt->sizebc,
+	       "use/def analysis PC out of range");
+  }
+
+#undef USE_SLOT
+#undef DEF_SLOT
+
+  return 0;  /* unreachable */
+}
+
+/* Mark slots used by upvalues of child prototypes as used. */
+static void snap_useuv(GCproto *pt, uint8_t *udf)
+{
+  /* This is a coarse check, because it's difficult to correlate the lifetime
+  ** of slots and closures. But the number of false positives is quite low.
+  ** A false positive may cause a slot not to be purged, which is just
+  ** a missed optimization.
+  */
+  if ((pt->flags & PROTO_CHILD)) {
+    ptrdiff_t i, j, n = pt->sizekgc;
+    GCRef *kr = mref(pt->k, GCRef) - 1;
+    for (i = 0; i < n; i++, kr--) {
+      GCobj *o = gcref(*kr);
+      if (o->gch.gct == ~LJ_TPROTO) {
+	for (j = 0; j < gco2pt(o)->sizeuv; j++) {
+	  uint32_t v = proto_uv(gco2pt(o))[j];
+	  if ((v & PROTO_UV_LOCAL)) {
+	    udf[(v & 0xff)] = 0;
+	  }
+	}
+      }
+    }
+  }
+}
+
+/* Purge dead slots before the next snapshot. */
+void lj_snap_purge(jit_State *J)
+{
+  uint8_t udf[SNAP_USEDEF_SLOTS];
+  BCReg s, maxslot = J->maxslot;
+  if (bc_op(*J->pc) == BC_FUNCV && maxslot > J->pt->numparams)
+    maxslot = J->pt->numparams;
+  s = snap_usedef(J, udf, J->pc, maxslot);
+  if (s < maxslot) {
+    snap_useuv(J->pt, udf);
+    for (; s < maxslot; s++)
+      if (udf[s] != 0)
+	J->base[s] = 0;  /* Purge dead slots. */
+  }
+}
+
+/* Shrink last snapshot. */
+void lj_snap_shrink(jit_State *J)
+{
+  SnapShot *snap = &J->cur.snap[J->cur.nsnap-1];
+  SnapEntry *map = &J->cur.snapmap[snap->mapofs];
+  MSize n, m, nlim, nent = snap->nent;
+  uint8_t udf[SNAP_USEDEF_SLOTS];
+  BCReg maxslot = J->maxslot;
+  BCReg baseslot = J->baseslot;
+  BCReg minslot = snap_usedef(J, udf, snap_pc(&map[nent]), maxslot);
+  if (minslot < maxslot) snap_useuv(J->pt, udf);
+  maxslot += baseslot;
+  minslot += baseslot;
+  snap->nslots = (uint8_t)maxslot;
+  for (n = m = 0; n < nent; n++) {  /* Remove unused slots from snapshot. */
+    BCReg s = snap_slot(map[n]);
+    if (s < minslot || (s < maxslot && udf[s-baseslot] == 0))
+      map[m++] = map[n];  /* Only copy used slots. */
+  }
+  snap->nent = (uint8_t)m;
+  nlim = J->cur.nsnapmap - snap->mapofs - 1;
+  while (n <= nlim) map[m++] = map[n++];  /* Move PC + frame links down. */
+  J->cur.nsnapmap = (uint32_t)(snap->mapofs + m);  /* Free up space in map. */
+}
+
+/* -- Snapshot access ----------------------------------------------------- */
+
+/* Initialize a Bloom Filter with all renamed refs.
+** There are very few renames (often none), so the filter has
+** very few bits set. This makes it suitable for negative filtering.
+*/
+static BloomFilter snap_renamefilter(GCtrace *T, SnapNo lim)
+{
+  BloomFilter rfilt = 0;
+  IRIns *ir;
+  for (ir = &T->ir[T->nins-1]; ir->o == IR_RENAME; ir--)
+    if (ir->op2 <= lim)
+      bloomset(rfilt, ir->op1);
+  return rfilt;
+}
+
+/* Process matching renames to find the original RegSP. */
+static RegSP snap_renameref(GCtrace *T, SnapNo lim, IRRef ref, RegSP rs)
+{
+  IRIns *ir;
+  for (ir = &T->ir[T->nins-1]; ir->o == IR_RENAME; ir--)
+    if (ir->op1 == ref && ir->op2 <= lim)
+      rs = ir->prev;
+  return rs;
+}
+
+/* Copy RegSP from parent snapshot to the parent links of the IR. */
+IRIns *lj_snap_regspmap(jit_State *J, GCtrace *T, SnapNo snapno, IRIns *ir)
+{
+  SnapShot *snap = &T->snap[snapno];
+  SnapEntry *map = &T->snapmap[snap->mapofs];
+  BloomFilter rfilt = snap_renamefilter(T, snapno);
+  MSize n = 0;
+  IRRef ref = 0;
+  UNUSED(J);
+  for ( ; ; ir++) {
+    uint32_t rs;
+    if (ir->o == IR_SLOAD) {
+      if (!(ir->op2 & IRSLOAD_PARENT)) break;
+      for ( ; ; n++) {
+	lj_assertJ(n < snap->nent, "slot %d not found in snapshot", ir->op1);
+	if (snap_slot(map[n]) == ir->op1) {
+	  ref = snap_ref(map[n++]);
+	  break;
+	}
+      }
+    } else if (LJ_SOFTFP32 && ir->o == IR_HIOP) {
+      ref++;
+    } else if (ir->o == IR_PVAL) {
+      ref = ir->op1 + REF_BIAS;
+    } else {
+      break;
+    }
+    rs = T->ir[ref].prev;
+    if (bloomtest(rfilt, ref))
+      rs = snap_renameref(T, snapno, ref, rs);
+    ir->prev = (uint16_t)rs;
+    lj_assertJ(regsp_used(rs), "unused IR %04d in snapshot", ref - REF_BIAS);
+  }
+  return ir;
+}
+
+/* -- Snapshot replay ----------------------------------------------------- */
+
+/* Replay constant from parent trace. */
+static TRef snap_replay_const(jit_State *J, IRIns *ir)
+{
+  /* Only have to deal with constants that can occur in stack slots. */
+  switch ((IROp)ir->o) {
+  case IR_KPRI: return TREF_PRI(irt_type(ir->t));
+  case IR_KINT: return lj_ir_kint(J, ir->i);
+  case IR_KGC: return lj_ir_kgc(J, ir_kgc(ir), irt_t(ir->t));
+  case IR_KNUM: case IR_KINT64:
+    return lj_ir_k64(J, (IROp)ir->o, ir_k64(ir)->u64);
+  case IR_KPTR: return lj_ir_kptr(J, ir_kptr(ir));  /* Continuation. */
+  default: lj_assertJ(0, "bad IR constant op %d", ir->o); return TREF_NIL;
+  }
+}
+
+/* De-duplicate parent reference. */
+static TRef snap_dedup(jit_State *J, SnapEntry *map, MSize nmax, IRRef ref)
+{
+  MSize j;
+  for (j = 0; j < nmax; j++)
+    if (snap_ref(map[j]) == ref)
+      return J->slot[snap_slot(map[j])] & ~(SNAP_KEYINDEX|SNAP_CONT|SNAP_FRAME);
+  return 0;
+}
+
+/* Emit parent reference with de-duplication. */
+static TRef snap_pref(jit_State *J, GCtrace *T, SnapEntry *map, MSize nmax,
+		      BloomFilter seen, IRRef ref)
+{
+  IRIns *ir = &T->ir[ref];
+  TRef tr;
+  if (irref_isk(ref))
+    tr = snap_replay_const(J, ir);
+  else if (!regsp_used(ir->prev))
+    tr = 0;
+  else if (!bloomtest(seen, ref) || (tr = snap_dedup(J, map, nmax, ref)) == 0)
+    tr = emitir(IRT(IR_PVAL, irt_type(ir->t)), ref - REF_BIAS, 0);
+  return tr;
+}
+
+/* Check whether a sunk store corresponds to an allocation. Slow path. */
+static int snap_sunk_store2(GCtrace *T, IRIns *ira, IRIns *irs)
+{
+  if (irs->o == IR_ASTORE || irs->o == IR_HSTORE ||
+      irs->o == IR_FSTORE || irs->o == IR_XSTORE) {
+    IRIns *irk = &T->ir[irs->op1];
+    if (irk->o == IR_AREF || irk->o == IR_HREFK)
+      irk = &T->ir[irk->op1];
+    return (&T->ir[irk->op1] == ira);
+  }
+  return 0;
+}
+
+/* Check whether a sunk store corresponds to an allocation. Fast path. */
+static LJ_AINLINE int snap_sunk_store(GCtrace *T, IRIns *ira, IRIns *irs)
+{
+  if (irs->s != 255)
+    return (ira + irs->s == irs);  /* Fast check. */
+  return snap_sunk_store2(T, ira, irs);
+}
+
+/* Replay snapshot state to setup side trace. */
+void lj_snap_replay(jit_State *J, GCtrace *T)
+{
+  SnapShot *snap = &T->snap[J->exitno];
+  SnapEntry *map = &T->snapmap[snap->mapofs];
+  MSize n, nent = snap->nent;
+  BloomFilter seen = 0;
+  int pass23 = 0;
+  J->framedepth = 0;
+  /* Emit IR for slots inherited from parent snapshot. */
+  for (n = 0; n < nent; n++) {
+    SnapEntry sn = map[n];
+    BCReg s = snap_slot(sn);
+    IRRef ref = snap_ref(sn);
+    IRIns *ir = &T->ir[ref];
+    TRef tr;
+    /* The bloom filter avoids O(nent^2) overhead for de-duping slots. */
+    if (bloomtest(seen, ref) && (tr = snap_dedup(J, map, n, ref)) != 0)
+      goto setslot;
+    bloomset(seen, ref);
+    if (irref_isk(ref)) {
+      /* See special treatment of LJ_FR2 slot 1 in snapshot_slots() above. */
+      if (LJ_FR2 && (sn == SNAP(1, SNAP_FRAME | SNAP_NORESTORE, REF_NIL)))
+	tr = 0;
+      else
+	tr = snap_replay_const(J, ir);
+    } else if (!regsp_used(ir->prev)) {
+      pass23 = 1;
+      lj_assertJ(s != 0, "unused slot 0 in snapshot");
+      tr = s;
+    } else {
+      IRType t = irt_type(ir->t);
+      uint32_t mode = IRSLOAD_INHERIT|IRSLOAD_PARENT;
+      if (LJ_SOFTFP32 && (sn & SNAP_SOFTFPNUM)) t = IRT_NUM;
+      if (ir->o == IR_SLOAD) mode |= (ir->op2 & IRSLOAD_READONLY);
+      if ((sn & SNAP_KEYINDEX)) mode |= IRSLOAD_KEYINDEX;
+      tr = emitir_raw(IRT(IR_SLOAD, t), s, mode);
+    }
+  setslot:
+    /* Same as TREF_* flags. */
+    J->slot[s] = tr | (sn&(SNAP_KEYINDEX|SNAP_CONT|SNAP_FRAME));
+    J->framedepth += ((sn & (SNAP_CONT|SNAP_FRAME)) && (s != LJ_FR2));
+    if ((sn & SNAP_FRAME))
+      J->baseslot = s+1;
+  }
+  if (pass23) {
+    IRIns *irlast = &T->ir[snap->ref];
+    pass23 = 0;
+    /* Emit dependent PVALs. */
+    for (n = 0; n < nent; n++) {
+      SnapEntry sn = map[n];
+      IRRef refp = snap_ref(sn);
+      IRIns *ir = &T->ir[refp];
+      if (regsp_reg(ir->r) == RID_SUNK) {
+	if (J->slot[snap_slot(sn)] != snap_slot(sn)) continue;
+	pass23 = 1;
+	lj_assertJ(ir->o == IR_TNEW || ir->o == IR_TDUP ||
+		   ir->o == IR_CNEW || ir->o == IR_CNEWI,
+		   "sunk parent IR %04d has bad op %d", refp - REF_BIAS, ir->o);
+	if (ir->op1 >= T->nk) snap_pref(J, T, map, nent, seen, ir->op1);
+	if (ir->op2 >= T->nk) snap_pref(J, T, map, nent, seen, ir->op2);
+	if (LJ_HASFFI && ir->o == IR_CNEWI) {
+	  if (LJ_32 && refp+1 < T->nins && (ir+1)->o == IR_HIOP)
+	    snap_pref(J, T, map, nent, seen, (ir+1)->op2);
+	} else {
+	  IRIns *irs;
+	  for (irs = ir+1; irs < irlast; irs++)
+	    if (irs->r == RID_SINK && snap_sunk_store(T, ir, irs)) {
+	      if (snap_pref(J, T, map, nent, seen, irs->op2) == 0)
+		snap_pref(J, T, map, nent, seen, T->ir[irs->op2].op1);
+	      else if ((LJ_SOFTFP32 || (LJ_32 && LJ_HASFFI)) &&
+		       irs+1 < irlast && (irs+1)->o == IR_HIOP)
+		snap_pref(J, T, map, nent, seen, (irs+1)->op2);
+	    }
+	}
+      } else if (!irref_isk(refp) && !regsp_used(ir->prev)) {
+	lj_assertJ(ir->o == IR_CONV && ir->op2 == IRCONV_NUM_INT,
+		   "sunk parent IR %04d has bad op %d", refp - REF_BIAS, ir->o);
+	J->slot[snap_slot(sn)] = snap_pref(J, T, map, nent, seen, ir->op1);
+      }
+    }
+    /* Replay sunk instructions. */
+    for (n = 0; pass23 && n < nent; n++) {
+      SnapEntry sn = map[n];
+      IRRef refp = snap_ref(sn);
+      IRIns *ir = &T->ir[refp];
+      if (regsp_reg(ir->r) == RID_SUNK) {
+	TRef op1, op2;
+	if (J->slot[snap_slot(sn)] != snap_slot(sn)) {  /* De-dup allocs. */
+	  J->slot[snap_slot(sn)] = J->slot[J->slot[snap_slot(sn)]];
+	  continue;
+	}
+	op1 = ir->op1;
+	if (op1 >= T->nk) op1 = snap_pref(J, T, map, nent, seen, op1);
+	op2 = ir->op2;
+	if (op2 >= T->nk) op2 = snap_pref(J, T, map, nent, seen, op2);
+	if (LJ_HASFFI && ir->o == IR_CNEWI) {
+	  if (LJ_32 && refp+1 < T->nins && (ir+1)->o == IR_HIOP) {
+	    lj_needsplit(J);  /* Emit joining HIOP. */
+	    op2 = emitir_raw(IRT(IR_HIOP, IRT_I64), op2,
+			     snap_pref(J, T, map, nent, seen, (ir+1)->op2));
+	  }
+	  J->slot[snap_slot(sn)] = emitir(ir->ot & ~(IRT_MARK|IRT_ISPHI), op1, op2);
+	} else {
+	  IRIns *irs;
+	  TRef tr = emitir(ir->ot, op1, op2);
+	  J->slot[snap_slot(sn)] = tr;
+	  for (irs = ir+1; irs < irlast; irs++)
+	    if (irs->r == RID_SINK && snap_sunk_store(T, ir, irs)) {
+	      IRIns *irr = &T->ir[irs->op1];
+	      TRef val, key = irr->op2, tmp = tr;
+	      if (irr->o != IR_FREF) {
+		IRIns *irk = &T->ir[key];
+		if (irr->o == IR_HREFK)
+		  key = lj_ir_kslot(J, snap_replay_const(J, &T->ir[irk->op1]),
+				    irk->op2);
+		else
+		  key = snap_replay_const(J, irk);
+		if (irr->o == IR_HREFK || irr->o == IR_AREF) {
+		  IRIns *irf = &T->ir[irr->op1];
+		  tmp = emitir(irf->ot, tmp, irf->op2);
+		}
+	      }
+	      tmp = emitir(irr->ot, tmp, key);
+	      val = snap_pref(J, T, map, nent, seen, irs->op2);
+	      if (val == 0) {
+		IRIns *irc = &T->ir[irs->op2];
+		lj_assertJ(irc->o == IR_CONV && irc->op2 == IRCONV_NUM_INT,
+			   "sunk store for parent IR %04d with bad op %d",
+			   refp - REF_BIAS, irc->o);
+		val = snap_pref(J, T, map, nent, seen, irc->op1);
+		val = emitir(IRTN(IR_CONV), val, IRCONV_NUM_INT);
+	      } else if ((LJ_SOFTFP32 || (LJ_32 && LJ_HASFFI)) &&
+			 irs+1 < irlast && (irs+1)->o == IR_HIOP) {
+		IRType t = IRT_I64;
+		if (LJ_SOFTFP32 && irt_type((irs+1)->t) == IRT_SOFTFP)
+		  t = IRT_NUM;
+		lj_needsplit(J);
+		if (irref_isk(irs->op2) && irref_isk((irs+1)->op2)) {
+		  uint64_t k = (uint32_t)T->ir[irs->op2].i +
+			       ((uint64_t)T->ir[(irs+1)->op2].i << 32);
+		  val = lj_ir_k64(J, t == IRT_I64 ? IR_KINT64 : IR_KNUM, k);
+		} else {
+		  val = emitir_raw(IRT(IR_HIOP, t), val,
+			  snap_pref(J, T, map, nent, seen, (irs+1)->op2));
+		}
+		tmp = emitir(IRT(irs->o, t), tmp, val);
+		continue;
+	      }
+	      tmp = emitir(irs->ot, tmp, val);
+	    } else if (LJ_HASFFI && irs->o == IR_XBAR && ir->o == IR_CNEW) {
+	      emitir(IRT(IR_XBAR, IRT_NIL), 0, 0);
+	    }
+	}
+      }
+    }
+  }
+  J->base = J->slot + J->baseslot;
+  J->maxslot = snap->nslots - J->baseslot;
+  lj_snap_add(J);
+  if (pass23)  /* Need explicit GC step _after_ initial snapshot. */
+    emitir_raw(IRTG(IR_GCSTEP, IRT_NIL), 0, 0);
+}
+
+/* -- Snapshot restore ---------------------------------------------------- */
+
+static void snap_unsink(jit_State *J, GCtrace *T, ExitState *ex,
+			SnapNo snapno, BloomFilter rfilt,
+			IRIns *ir, TValue *o);
+
+/* Restore a value from the trace exit state. */
+static void snap_restoreval(jit_State *J, GCtrace *T, ExitState *ex,
+			    SnapNo snapno, BloomFilter rfilt,
+			    IRRef ref, TValue *o)
+{
+  IRIns *ir = &T->ir[ref];
+  IRType1 t = ir->t;
+  RegSP rs = ir->prev;
+  if (irref_isk(ref)) {  /* Restore constant slot. */
+    if (ir->o == IR_KPTR) {
+      o->u64 = (uint64_t)(uintptr_t)ir_kptr(ir);
+    } else {
+      lj_assertJ(!(ir->o == IR_KKPTR || ir->o == IR_KNULL),
+		 "restore of const from IR %04d with bad op %d",
+		 ref - REF_BIAS, ir->o);
+      lj_ir_kvalue(J->L, o, ir);
+    }
+    return;
+  }
+  if (LJ_UNLIKELY(bloomtest(rfilt, ref)))
+    rs = snap_renameref(T, snapno, ref, rs);
+  if (ra_hasspill(regsp_spill(rs))) {  /* Restore from spill slot. */
+    int32_t *sps = &ex->spill[regsp_spill(rs)];
+    if (irt_isinteger(t)) {
+      setintV(o, *sps);
+#if !LJ_SOFTFP32
+    } else if (irt_isnum(t)) {
+      o->u64 = *(uint64_t *)sps;
+#endif
+#if LJ_64 && !LJ_GC64
+    } else if (irt_islightud(t)) {
+      /* 64 bit lightuserdata which may escape already has the tag bits. */
+      o->u64 = *(uint64_t *)sps;
+#endif
+    } else {
+      lj_assertJ(!irt_ispri(t), "PRI ref with spill slot");
+      setgcV(J->L, o, (GCobj *)(uintptr_t)*(GCSize *)sps, irt_toitype(t));
+    }
+  } else {  /* Restore from register. */
+    Reg r = regsp_reg(rs);
+    if (ra_noreg(r)) {
+      lj_assertJ(ir->o == IR_CONV && ir->op2 == IRCONV_NUM_INT,
+		 "restore from IR %04d has no reg", ref - REF_BIAS);
+      snap_restoreval(J, T, ex, snapno, rfilt, ir->op1, o);
+      if (LJ_DUALNUM) setnumV(o, (lua_Number)intV(o));
+      return;
+    } else if (irt_isinteger(t)) {
+      setintV(o, (int32_t)ex->gpr[r-RID_MIN_GPR]);
+#if !LJ_SOFTFP
+    } else if (irt_isnum(t)) {
+      setnumV(o, ex->fpr[r-RID_MIN_FPR]);
+#elif LJ_64  /* && LJ_SOFTFP */
+    } else if (irt_isnum(t)) {
+      o->u64 = ex->gpr[r-RID_MIN_GPR];
+#endif
+#if LJ_64 && !LJ_GC64
+    } else if (irt_is64(t)) {
+      /* 64 bit values that already have the tag bits. */
+      o->u64 = ex->gpr[r-RID_MIN_GPR];
+#endif
+    } else if (irt_ispri(t)) {
+      setpriV(o, irt_toitype(t));
+    } else {
+      setgcV(J->L, o, (GCobj *)ex->gpr[r-RID_MIN_GPR], irt_toitype(t));
+    }
+  }
+}
+
+#if LJ_HASFFI
+/* Restore raw data from the trace exit state. */
+static void snap_restoredata(jit_State *J, GCtrace *T, ExitState *ex,
+			     SnapNo snapno, BloomFilter rfilt,
+			     IRRef ref, void *dst, CTSize sz)
+{
+  IRIns *ir = &T->ir[ref];
+  RegSP rs = ir->prev;
+  int32_t *src;
+  uint64_t tmp;
+  UNUSED(J);
+  if (irref_isk(ref)) {
+    if (ir_isk64(ir)) {
+      src = (int32_t *)&ir[1];
+    } else if (sz == 8) {
+      tmp = (uint64_t)(uint32_t)ir->i;
+      src = (int32_t *)&tmp;
+    } else {
+      src = &ir->i;
+    }
+  } else {
+    if (LJ_UNLIKELY(bloomtest(rfilt, ref)))
+      rs = snap_renameref(T, snapno, ref, rs);
+    if (ra_hasspill(regsp_spill(rs))) {
+      src = &ex->spill[regsp_spill(rs)];
+      if (sz == 8 && !irt_is64(ir->t)) {
+	tmp = (uint64_t)(uint32_t)*src;
+	src = (int32_t *)&tmp;
+      }
+    } else {
+      Reg r = regsp_reg(rs);
+      if (ra_noreg(r)) {
+	/* Note: this assumes CNEWI is never used for SOFTFP split numbers. */
+	lj_assertJ(sz == 8 && ir->o == IR_CONV && ir->op2 == IRCONV_NUM_INT,
+		   "restore from IR %04d has no reg", ref - REF_BIAS);
+	snap_restoredata(J, T, ex, snapno, rfilt, ir->op1, dst, 4);
+	*(lua_Number *)dst = (lua_Number)*(int32_t *)dst;
+	return;
+      }
+      src = (int32_t *)&ex->gpr[r-RID_MIN_GPR];
+#if !LJ_SOFTFP
+      if (r >= RID_MAX_GPR) {
+	src = (int32_t *)&ex->fpr[r-RID_MIN_FPR];
+#if LJ_TARGET_PPC
+	if (sz == 4) {  /* PPC FPRs are always doubles. */
+	  *(float *)dst = (float)*(double *)src;
+	  return;
+	}
+#else
+	if (LJ_BE && sz == 4) src++;
+#endif
+      } else
+#endif
+      if (LJ_64 && LJ_BE && sz == 4) src++;
+    }
+  }
+  lj_assertJ(sz == 1 || sz == 2 || sz == 4 || sz == 8,
+	     "restore from IR %04d with bad size %d", ref - REF_BIAS, sz);
+  if (sz == 4) *(int32_t *)dst = *src;
+  else if (sz == 8) *(int64_t *)dst = *(int64_t *)src;
+  else if (sz == 1) *(int8_t *)dst = (int8_t)*src;
+  else *(int16_t *)dst = (int16_t)*src;
+}
+#endif
+
+/* Unsink allocation from the trace exit state. Unsink sunk stores. */
+static void snap_unsink(jit_State *J, GCtrace *T, ExitState *ex,
+			SnapNo snapno, BloomFilter rfilt,
+			IRIns *ir, TValue *o)
+{
+  lj_assertJ(ir->o == IR_TNEW || ir->o == IR_TDUP ||
+	     ir->o == IR_CNEW || ir->o == IR_CNEWI,
+	     "sunk allocation with bad op %d", ir->o);
+#if LJ_HASFFI
+  if (ir->o == IR_CNEW || ir->o == IR_CNEWI) {
+    CTState *cts = ctype_cts(J->L);
+    CTypeID id = (CTypeID)T->ir[ir->op1].i;
+    CTSize sz;
+    CTInfo info = lj_ctype_info(cts, id, &sz);
+    GCcdata *cd = lj_cdata_newx(cts, id, sz, info);
+    setcdataV(J->L, o, cd);
+    if (ir->o == IR_CNEWI) {
+      uint8_t *p = (uint8_t *)cdataptr(cd);
+      lj_assertJ(sz == 4 || sz == 8, "sunk cdata with bad size %d", sz);
+      if (LJ_32 && sz == 8 && ir+1 < T->ir + T->nins && (ir+1)->o == IR_HIOP) {
+	snap_restoredata(J, T, ex, snapno, rfilt, (ir+1)->op2,
+			 LJ_LE ? p+4 : p, 4);
+	if (LJ_BE) p += 4;
+	sz = 4;
+      }
+      snap_restoredata(J, T, ex, snapno, rfilt, ir->op2, p, sz);
+    } else {
+      IRIns *irs, *irlast = &T->ir[T->snap[snapno].ref];
+      for (irs = ir+1; irs < irlast; irs++)
+	if (irs->r == RID_SINK && snap_sunk_store(T, ir, irs)) {
+	  IRIns *iro = &T->ir[T->ir[irs->op1].op2];
+	  uint8_t *p = (uint8_t *)cd;
+	  CTSize szs;
+	  lj_assertJ(irs->o == IR_XSTORE, "sunk store with bad op %d", irs->o);
+	  lj_assertJ(T->ir[irs->op1].o == IR_ADD,
+		     "sunk store with bad add op %d", T->ir[irs->op1].o);
+	  lj_assertJ(iro->o == IR_KINT || iro->o == IR_KINT64,
+		     "sunk store with bad const offset op %d", iro->o);
+	  if (irt_is64(irs->t)) szs = 8;
+	  else if (irt_isi8(irs->t) || irt_isu8(irs->t)) szs = 1;
+	  else if (irt_isi16(irs->t) || irt_isu16(irs->t)) szs = 2;
+	  else szs = 4;
+	  if (LJ_64 && iro->o == IR_KINT64)
+	    p += (int64_t)ir_k64(iro)->u64;
+	  else
+	    p += iro->i;
+	  lj_assertJ(p >= (uint8_t *)cdataptr(cd) &&
+		     p + szs <= (uint8_t *)cdataptr(cd) + sz,
+		     "sunk store with offset out of range");
+	  if (LJ_32 && irs+1 < T->ir + T->nins && (irs+1)->o == IR_HIOP) {
+	    lj_assertJ(szs == 4, "sunk store with bad size %d", szs);
+	    snap_restoredata(J, T, ex, snapno, rfilt, (irs+1)->op2,
+			     LJ_LE ? p+4 : p, 4);
+	    if (LJ_BE) p += 4;
+	  }
+	  snap_restoredata(J, T, ex, snapno, rfilt, irs->op2, p, szs);
+	}
+    }
+  } else
+#endif
+  {
+    IRIns *irs, *irlast;
+    GCtab *t = ir->o == IR_TNEW ? lj_tab_new(J->L, ir->op1, ir->op2) :
+				  lj_tab_dup(J->L, ir_ktab(&T->ir[ir->op1]));
+    settabV(J->L, o, t);
+    irlast = &T->ir[T->snap[snapno].ref];
+    for (irs = ir+1; irs < irlast; irs++)
+      if (irs->r == RID_SINK && snap_sunk_store(T, ir, irs)) {
+	IRIns *irk = &T->ir[irs->op1];
+	TValue tmp, *val;
+	lj_assertJ(irs->o == IR_ASTORE || irs->o == IR_HSTORE ||
+		   irs->o == IR_FSTORE,
+		   "sunk store with bad op %d", irs->o);
+	if (irk->o == IR_FREF) {
+	  lj_assertJ(irk->op2 == IRFL_TAB_META,
+		     "sunk store with bad field %d", irk->op2);
+	  snap_restoreval(J, T, ex, snapno, rfilt, irs->op2, &tmp);
+	  /* NOBARRIER: The table is new (marked white). */
+	  setgcref(t->metatable, obj2gco(tabV(&tmp)));
+	} else {
+	  irk = &T->ir[irk->op2];
+	  if (irk->o == IR_KSLOT) irk = &T->ir[irk->op1];
+	  lj_ir_kvalue(J->L, &tmp, irk);
+	  val = lj_tab_set(J->L, t, &tmp);
+	  /* NOBARRIER: The table is new (marked white). */
+	  snap_restoreval(J, T, ex, snapno, rfilt, irs->op2, val);
+	  if (LJ_SOFTFP32 && irs+1 < T->ir + T->nins && (irs+1)->o == IR_HIOP) {
+	    snap_restoreval(J, T, ex, snapno, rfilt, (irs+1)->op2, &tmp);
+	    val->u32.hi = tmp.u32.lo;
+	  }
+	}
+      }
+  }
+}
+
+/* Restore interpreter state from exit state with the help of a snapshot. */
+const BCIns *lj_snap_restore(jit_State *J, void *exptr)
+{
+  ExitState *ex = (ExitState *)exptr;
+  SnapNo snapno = J->exitno;  /* For now, snapno == exitno. */
+  GCtrace *T = traceref(J, J->parent);
+  SnapShot *snap = &T->snap[snapno];
+  MSize n, nent = snap->nent;
+  SnapEntry *map = &T->snapmap[snap->mapofs];
+#if !LJ_FR2 || defined(LUA_USE_ASSERT)
+  SnapEntry *flinks = &T->snapmap[snap_nextofs(T, snap)-1-LJ_FR2];
+#endif
+#if !LJ_FR2
+  ptrdiff_t ftsz0;
+#endif
+  TValue *frame;
+  BloomFilter rfilt = snap_renamefilter(T, snapno);
+  const BCIns *pc = snap_pc(&map[nent]);
+  lua_State *L = J->L;
+
+  /* Set interpreter PC to the next PC to get correct error messages. */
+  setcframe_pc(cframe_raw(L->cframe), pc+1);
+
+  /* Make sure the stack is big enough for the slots from the snapshot. */
+  if (LJ_UNLIKELY(L->base + snap->topslot >= tvref(L->maxstack))) {
+    L->top = curr_topL(L);
+    lj_state_growstack(L, snap->topslot - curr_proto(L)->framesize);
+  }
+
+  /* Fill stack slots with data from the registers and spill slots. */
+  frame = L->base-1-LJ_FR2;
+#if !LJ_FR2
+  ftsz0 = frame_ftsz(frame);  /* Preserve link to previous frame in slot #0. */
+#endif
+  for (n = 0; n < nent; n++) {
+    SnapEntry sn = map[n];
+    if (!(sn & SNAP_NORESTORE)) {
+      TValue *o = &frame[snap_slot(sn)];
+      IRRef ref = snap_ref(sn);
+      IRIns *ir = &T->ir[ref];
+      if (ir->r == RID_SUNK) {
+	MSize j;
+	for (j = 0; j < n; j++)
+	  if (snap_ref(map[j]) == ref) {  /* De-duplicate sunk allocations. */
+	    copyTV(L, o, &frame[snap_slot(map[j])]);
+	    goto dupslot;
+	  }
+	snap_unsink(J, T, ex, snapno, rfilt, ir, o);
+      dupslot:
+	continue;
+      }
+      snap_restoreval(J, T, ex, snapno, rfilt, ref, o);
+      if (LJ_SOFTFP32 && (sn & SNAP_SOFTFPNUM) && tvisint(o)) {
+	TValue tmp;
+	snap_restoreval(J, T, ex, snapno, rfilt, ref+1, &tmp);
+	o->u32.hi = tmp.u32.lo;
+#if !LJ_FR2
+      } else if ((sn & (SNAP_CONT|SNAP_FRAME))) {
+	/* Overwrite tag with frame link. */
+	setframe_ftsz(o, snap_slot(sn) != 0 ? (int32_t)*flinks-- : ftsz0);
+	L->base = o+1;
+#endif
+      } else if ((sn & SNAP_KEYINDEX)) {
+	/* A IRT_INT key index slot is restored as a number. Undo this. */
+	o->u32.lo = (uint32_t)(LJ_DUALNUM ? intV(o) : lj_num2int(numV(o)));
+	o->u32.hi = LJ_KEYINDEX;
+      }
+    }
+  }
+#if LJ_FR2
+  L->base += (map[nent+LJ_BE] & 0xff);
+#endif
+  lj_assertJ(map + nent == flinks, "inconsistent frames in snapshot");
+
+  /* Compute current stack top. */
+  switch (bc_op(*pc)) {
+  default:
+    if (bc_op(*pc) < BC_FUNCF) {
+      L->top = curr_topL(L);
+      break;
+    }
+    /* fallthrough */
+  case BC_CALLM: case BC_CALLMT: case BC_RETM: case BC_TSETM:
+    L->top = frame + snap->nslots;
+    break;
+  }
+  return pc;
+}
+
+#undef emitir_raw
+#undef emitir
+
+#endif