[llvm] [RISCV] Correct copyPhysReg for GPRPF64. (PR #70419)

[Shao-Ce SUN via llvm-commits]

sunshaoce wrote:

> > LGTM. This is indeed a negligence, GPRF64 should be copied in pairs to the register.
> 
> @sunshaoce This bug is pretty concerning. Can you say how much testing of Zdinx you've done for RV32?

Because we lacked testing personnel at the time, we manually tested many assembly files and some programs generated by csmith, and indeed did not discover this issue before.

https://github.com/llvm/llvm-project/pull/70419