This is an implementation a 4-bit Kogge Stone Adder (a type of carry-tree adder) in VHDL using Xilinx Vivado. A Kogge Stone Adder is a carry tree adder (an upgrade of carry-look-ahead adder) which creates a propagator and a generator to calculate the sum and carry. It is one of the most popular adders used commercially.
The references mentioned below have been of great help especially that of LarbiBekka34[2] and Bharat's Tutorial[3].
References : [1] https://en.wikipedia.org/wiki/Kogge%E2%80%93Stone_adder [2] https://github.com/LarbiBekka34/miniproject-vhdl [3] https://elnndccpro.wordpress.com/2017/01/25/a-design-of-kogge-stone-adder-8-bit/