[llvm] Complex deinterleaving/single reductions build fixReapply "Add support for single reductions in ComplexDeinterleavingPass (#112875)" (PR #120441)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Please add in the commit message what changed relative to the first PR. If it continues to cause issues, it will be useful to know that, especially if it's months from now.

https://github.com/llvm/llvm-project/pull/120441