ID:13374 Verilog HDL error at <location>: must use only constant operands for this operator

CAUSE: In a Verilog Design File (.v) at the specified location, you have used a non-constant operand, such as a reg, with an operator that requires only constant operands in the Quartus Prime software.

ACTION: Modify the design to use a different operator, or change the operand to a constant value.