Why does the Intel® Quartus® Prime Pro Edition Software hang during synthesis?

Due to a problem in the Intel® Quartus® Prime Pro Edition Software v21.3 and earlier, synthesis may hang during compilation. This problem occurs when a wire LUT feeds back into itself and synthesis gets into an infinite loop to resolve it.

To work around this problem, set the following command in the .qsf: 

set_global_assignment -name -SKIP_ATOM_SWEEPER ON

With this command, synthesis will not remove redundant wire cells, which means Fmax performance may be affected.

In the  Intel® Quartus® Prime Pro Edition Software v21.4, a wire LUT feeding back into itself will generate an error message.