如果memory的timing比较差，常规设置如下：

remove_path_groups -all
group_path -name I2R -from [all_inputs]   -to [all_register] -weight 1 -critical_range 0.5
group_path -name R2O -from [all_register] -to [all_outputs]  -weight 1 -critical_range 0.5
group_path -name R2R -from [all_register] -to [all_register] -weight 1 -critical_range 0.5
group_path -name M2R -from [all_memories] -to [all_register] -weight 2 -critical_range 1
group_path -name R2M -from [all_register] -to [all_memories] -weight 2 -critical_range 1