[llvm] [AMDGPU] Delete dead meta instructions (PR #193030)

[Jay Foad via llvm-commits]

jayfoad wrote:

> This is surely fixable: either don't delete the SI_RETURN_TO_EPILOG instruction (I don't know why does si-late-branch-lowering that)

Looks like this behaviour was introduced by @perlfu's https://reviews.llvm.org/D98915.

https://github.com/llvm/llvm-project/pull/193030