[llvm] [RISCV] Added new register class GPRNoGPRS defined as substraction of GPRC sequences from GPR (PR #106974)

[Vladislav Belov via llvm-commits]

vbe-sc wrote:

> > @wangpc-pp, @topperc there is an example of llvm-based tool developed in Syntacore ([syntacore/snippy#83](https://github.com/syntacore/snippy/pull/83)). For new patch it requires to add a new register class:
> > https://github.com/syntacore/snippy/blob/7d4ea758d58ad89ea48d32c75e0187192edcf930/llvm/tools/llvm-snippy/lib/Target/RISCV/Target.cpp#L1512
> > At the same time we are trying to keep in sync our LLVM project with upstream one as much as it possible, so we want to see this changes in the upstream.
> 
> Maybe you can upstream `llvm-snippy`?

We are thinking about it. However, `llvm-snippy` is a huge project and it looks difficult to upstream it now, but we really appreciate this offer. We are sure that later it would be possible. 

https://github.com/llvm/llvm-project/pull/106974