[llvm] r190598 - Add an instruction deprecation feature to TableGen.

[Joey Gouly]

> Thanks for the speedy fix :) -- Some basic PPC use cases committed in r190605.
> 

Thanks! Nice to see you using it so quickly too!

> I think that we might want to add a deprecation message in addition to the subtarget feature. It would be most useful, I think, to have something like this:
>
> , Deprecated<DeprecatedMFTB, "use mfspr instead">;
> 
> (so it would print, "warning: deprecated, use mfspr instead").
>
> What do you think?

Sounds like a good idea. I can try have a look tonight, shouldn't be too difficult to implement.

Joey