// on them, their lattices must be initially worse Bottom.
		return
	}

	oldLt := t.getLatticeCell(val)
	defer func() {
		// re-visit all uses of value if its lattice is changed
		newLt := t.getLatticeCell(val)
		if !equals(newLt, oldLt) {
			if int8(oldLt.tag) > int8(newLt.tag) {
				t.f.Fatalf("Must lower lattice\n")
			}
			t.addUses(val)
		}