Implement missing arch-specific `RegId` implementations about gdbstub

[DrChat]

Here is the relevant target description file from the GDB sources for PPC32:
https://github.com/bminor/binutils-gdb/blob/master/gdb/features/rs6000/powerpc-32.c

[DrChat]

Appreciate the other references :)

I have a PPC target, but I'll have to figure out the dynamic dispatch first before I can test a RegId implementation for it.

[daniel5151]

I would also leave the following links as well:

• https://github.com/bminor/binutils-gdb/blob/master/gdb/features/rs6000/powerpc-32.xml
• https://github.com/bminor/binutils-gdb/blob/master/gdb/features/rs6000/power-core.xml
• https://github.com/bminor/binutils-gdb/blob/master/gdb/features/rs6000/power-fpu.xml

Just as a reminder though, this issue is not a bug or a blocker - it is simply tracking something that should get resolved eventually. Moreover, implementing a new RegId isn't just adding a new impl RegId enum to the codebase -- you'd also have to put in some legwork to actually test the implementation as part of a larger project.

@jamcleod, you wouldn't happen to have some spare time on your hands to circle back and upstream a RegId implementation for PowerPcAltivec32? I know it's been a while, but I thought I'd ask since you were the one who originally upstreamed the rest of the PowerPC code.

If not, all good! I totally don't mind leaving this issue open until someone happens to use gdbstub with a Power PC target, and is willing to upstream a tested RegId implementation :)

[daniel5151]

Ah, well that's great then!

In that case, I'm looking forwards to seeing a PR 😄