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

[Jay Foad via cfe-commits]

jayfoad wrote:

> Both SelectionDAG and GlobalISel now perform this check before lowering target intrinsics. This allows targets to opt in by annotating intrinsic definitions directly, rather than adding custom checks during lowering, legalization, or instruction selection.

Why do the checks during instruction selection, instead of in the IR verifier?

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