error的描述是这个样子的:
**ERROR: (TA-152): A latency path from the 'Fall' edge of the master clock at source pin clk' to the 'Rise' edge of generated clock 'gen_clk' at pin 'gen_clk' cannot be found. You must modify your create_generated_clock constraint to be consistent with the network topology. The analysis will continue using 0ns source latency for generated clock 'gen_clk'. For backward compatibility with earlier releases or to remove the edge-to-edge sufficiency checking, you should set the global 'timing_enable_genclk_edge_based_source_latency' to false