public void removePhiAtBlock(final Block block) {
		final PhiStmt phi = phis[cfg.preOrderIndex(block)];

		if (phi != null) {
			if (SSA.DEBUG) {
				System.out.println("  removing " + phi + " at " + block);
			}

			phi.cleanup();
			phis[cfg.preOrderIndex(block)] = null;
		}
	}