I'm surprised to see no recognition of yosys, arachne-pnr and the icestorm tools which together are a free and open source HDL tool chain which already exists and is pretty widely used.
Unfortunately, they make very slow progress because they have to painstakingly reverse-engineer everything (with the possible exception of Lattice stuff).
For Xilinx chips, where exactly nothing is publicly documented at the lower levels of the stack, they have to spend mountains of time re-discovering everything.
Even if I deeply admire the effort and how far they've gotten, I can't help but think: what a terrible waste of human talent and time.
Edit: I once asked a Xilinx employee why they didn't OpenSource their entire software stack, because it struck me that they were in the chip manufacturing business, and not in the toolchain business (a blisteringly obvious fact when you look at the quality of such monstrosities as, e.g., Vivado), and that OpenSourcing the tools would potentially enlarge their potential target market by a large margin.
The culture is so broken in that space that I don't think he even actually understood the question.