private void downSafety(final ExprInfo exprInfo) {
		final Iterator blocks = cfg.nodes().iterator();

		while (blocks.hasNext()) {
			final Block block = (Block) blocks.next();

			final Phi phi = exprInfo.exprPhiAtBlock(block);

			if ((phi == null) || phi.downSafe()) {
				continue;
			}

			final Iterator e = cfg.preds(block).iterator();

			while (e.hasNext()) {
				final Block pred = (Block) e.next();
				resetDownSafe(phi, pred);
			}
		}
	}