[clang] [llvm] [RFC][CodeGen] Add generic target feature checks for intrinsics (PR #201470)

[Sameer Sahasrabuddhe via cfe-commits]

ssahasra wrote:

> The `$custom` handling is removed now.
> 
> > But you could do it in some required IR pass that is part of the codegen pipeline, like ExpandIRInsts? Just to avoid duplicating the checks between the two different isel frameworks.
> 
> Well, I don't think other IR passes are the right place for diagnostics and error reporting. If we want that, we'd probably need another pass similar to the Verifier, but with access to backend-specific information.
> 
> That could be a reasonable follow-up if we decide we really want to go in that direction.

Yes, I would be interested in that direction.

https://github.com/llvm/llvm-project/pull/201470