state.varSlots = state.varSlots[:len(state.vars)]
		for i := range state.varSlots {
			state.varSlots[i] = state.varSlots[i][:0]
		}
	}
	if cap(state.slotVars) < len(state.slots) {
		state.slotVars = make([]VarID, len(state.slots))
	} else {
		state.slotVars = state.slotVars[:len(state.slots)]
	}

	if state.partsByVarOffset == nil {
		state.partsByVarOffset = &partsByVarOffset{}
	}
	for varID, n := range state.vars {

// writes to the slot's mark bit and then as part of scanning reads
// the slot.
//
// Initially both [slot] and [slotmark] are 0 (nil)
// Mutator thread          GC thread
// st [slot], ptr          st [slotmark], 1
//
// ld r1, [slotmark]       ld r2, [slot]
//
// Without an expensive memory barrier between the st and the ld, the final