[llvm] [AMDGPU] Avoid put implicit_def into bundle that break reg's liveness (PR #142563)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> We cannot include implicit_def into the bundle because inside the bundle implicit def will not count for defined register and any use of this register in the latter program will cause the verification error.

You can and should include implicit_def in the bundle. It does not matter that it's an implicit_def, the liveness of that def should work the same as any other real instruction inside the bundle. 

> if the register it is defining doesn't overlap with other instruction, move the implicit_def into the front of the bundle

You don't really need to move anything. I guess you could handle it this way, but I think it would be more difficult than just treating the implicit_def like any other load def in the bundle 



https://github.com/llvm/llvm-project/pull/142563