[llvm] [CodeGen] Fix handling dead redefs in finalizeBundle (PR #157427)

[Jay Foad via llvm-commits]

jayfoad wrote:

> > I've always understood that the bundle should be equivalent to executing the contained instructions **serially**.
> 
> No, bundles have no ordering. It's as if they all executed at the same time

Citation? That's not what `finalizeBundle` implements. It has code to handle use operands that read a value written by a def operand in an *earlier* instruction in the bundle.

https://github.com/llvm/llvm-project/pull/157427