You aren't seriously implying than any bystander is capable of extending LLVM to map CUDA to SPIR-V? What percentage of present day gainfully employed software engineers do you suppose even has the background knowledge? How many hours do you suppose the work would require?
If LLVM has a SPIRV backend, probably very little. For a proof of concept, a bachelor CS thesis would probably do.
Clang already has a CUDA parser, and all the code to lower CUDA specific constructs to LLVM-IR, some of which are specific for the PTX backend. If you try to compile CUDA code for a different target, like SPIRV, you'll probably get some errors saying that some of the LLVM-IR instructions generated by clang are not available in that backend, and you'll need to generate the proper SPIRV calls in clang instead.
Its probably a great beginner task to get started with clang and LLVM. You don't need to worry about the C++ frontend side of things because that's already done, and can focus on understanding the LLVM-IR and how to emit it from clang when you already have a proper AST.
Late response I know, but I would say anyone who needs that feature could learn to do it, at least if they are on Hacker News. Maybe bystander isn't the most accurate term, but certainly anyone with criticism could take the gauntlet.
LLVM is very well documented and so are these standards. The open source community is also huge and full of talented contributors and more are always welcome to join. I think there's a reason why Linux and GitHub exist.
So in short, if it's a question of motivation and it's something you need, then become motivated to make it happen. That's more likely to happen then convincing a company to invest in supporting a competitor.
You aren't seriously implying than any bystander is capable of extending LLVM to map CUDA to SPIR-V? What percentage of present day gainfully employed software engineers do you suppose even has the background knowledge? How many hours do you suppose the work would require?