[llvm] MC: Remove bundle alignment mode (PR #148781)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> @MaskRay bundle alignment would have made #150239 unnecessary.

You'd still need a lot of heavy customization on AMDGPU side. You should implement padding in your backend's finishLayout.

Again, the NaCl aligned bundle mode, added in 2012, increased the complexity of MC internals, causing notable performance slowdowns for non-NaCl users. It isn't a good reference for similar features.

https://github.com/llvm/llvm-project/pull/148781