[llvm] [X86] Support EGPR (R16-R31) for APX (PR #67702)

[Shengchen Kan via llvm-commits]

KanRobert wrote:

> > The return value of `TRI::getNumRegs()` is a constant generated by tablgen, which is same for all cpus for one target.
> 
> I assume getNumRegs is the total number of registers defined in the enum in X86GenRegisterInfo.inc and the new registers are not at the end of that enum?

Yes, you are right.

https://github.com/llvm/llvm-project/pull/67702