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

[Jay Foad via llvm-commits]

jayfoad wrote:

> > It's a workaround, not a proper fix.
> 
> Hi jayfoad , if I'm not wrong the implicit_def inside a bundle will not add definition of registers. So if we want to fix this, we cannot leave it inside the bundle

Your patch will generate worse code in some cases (because it won't be able to form hard clauses in some cases) and it only avoids one specific case of this problem.

What if some other meta instruction with an implicit-def appears in a bundle? We will have the same problem again.

What if some non-meta instruction with an implicit-def appears in a bundle? We will have the same problem again.

A better fix would be to understand how `finalizeBundle` works, and fix it to do the right thing with implicits-defs.

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