[llvm] [AMDGPU] Replace dynamic VGPR feature with attribute (PR #133444)

[Diana Picus via llvm-commits]

rovka wrote:

> > > I have a question, how do programmers use this feature？
> > 
> > 
> > This is currently only used by the compiler, it is not intended to be used by programmers in its current form.
> 
> May I ask, in what way will it ultimately be provided to programmers for use？

I can't really comment on that.

You can get some general idea about how it's currently used in [this 3rd party article](https://chipsandcheese.com/p/dynamic-register-allocation-on-amds). 

https://github.com/llvm/llvm-project/pull/133444