Fix maxslots when recording BC_VARG, part 3.

Thanks to Peter Cawley. #1046

src/lj_record.c

@@ -1518,8 +1518,12 @@ static void rec_varg(jit_State *J, BCReg dst, ptrdiff_t nresults)
   if (J->framedepth > 0) {  /* Simple case: varargs defined on-trace. */
     ptrdiff_t i;
     if (nvararg < 0) nvararg = 0;
-    if (nresults == -1) nresults = nvararg;
-    J->maxslot = dst + (BCReg)nresults;
+    if (nresults != 1) {
+      if (nresults == -1) nresults = nvararg;
+      J->maxslot = dst + (BCReg)nresults;
+    } else if (dst >= J->maxslot) {
+      J->maxslot = dst + 1;
+    }
     if (J->baseslot + J->maxslot >= LJ_MAX_JSLOTS)
       lj_trace_err(J, LJ_TRERR_STACKOV);
     for (i = 0; i < nresults; i++)
@@ -1552,7 +1556,9 @@ static void rec_varg(jit_State *J, BCReg dst, ptrdiff_t nresults)
       }
       for (i = nvararg; i < nresults; i++)
 	J->base[dst+i] = TREF_NIL;
-      J->maxslot = dst + (BCReg)nresults;
+      if (nresults != 1 || dst >= J->maxslot) {
+	J->maxslot = dst + (BCReg)nresults;
+      }
     } else if (select_detect(J)) {  /* y = select(x, ...) */
       TRef tridx = J->base[dst-1];
       TRef tr = TREF_NIL;