Add zilsd & zcmlsd new instruction

[dongyasun]

Hi,
We referred to your implementation of Zilsd extension in binutils, and added some new contents to Zilsd extension according to the new spec(https://github.com/riscv/riscv-zilsd/blob/main/zilsd.adoc), including new operands, Gt and Gd, to match rs2 of sd instruction and rd of ld instruction to restrict registers. We think such implementation may be more complete. We also added some implementation of Zcmlsd extension based on our understanding of the new spec and classified c.ld, c.sd, c.ldsp, c.sdsp into Zcmlsd extension. We hope our work can be helpful to the implementation of zilsd & zcmlsd extension.

[dongyasun]

Thank you for embracing our suggestion. We have noticed that the specifications for this extension have been largely solidified.We(https://www.nucleisys.com/) are interested in partnering with you to submit a patch to the binutils upstream, with the goal of making zilsd and zcmlsd available within binutils. Would this collaboration be a possibility for us to explore? @christian-herber-nxp

[christian-herber-nxp]

Thank you for embracing our suggestion. We have noticed that the specifications for this extension have been largely solidified.We(https://www.nucleisys.com/) are interested in partnering with you to submit a patch to the binutils upstream, with the goal of making zilsd and zcmlsd available within binutils. Would this collaboration be a possibility for us to explore? @christian-herber-nxp

any help is welcome. i think there is also some room for improvement on the gcc side itself. On binutils, I am not sure if patches will be accepted before ratification. The specification is currently in architecture review. In the process, small changes are happening here and there.
In case you want to submit a patch upstream, you are very welcome to do so.