[llvm] [AMDGPU] Enable copy from VCC to SHARED_BASE. (PR #164138)

[via llvm-commits]

carlobertolli wrote:

The comment after that early exit seems relevant:

  // FIXME: At this point the COPY verify is done only for non-ssa forms.
  // Find a better property to recognize the point where instruction selection
  // is just done.
  // We can only enforce this check after SIFixSGPRCopies pass so that the
  // illegal copies are legalized and thereafter we don't expect a pass
  // inserting similar copies.
  
  
  
I'll leave this alone for the time being, but please @arsenm let me know if there is any extra verification you think we should be doing.

https://github.com/llvm/llvm-project/pull/164138