[llvm] Add support for single reductions in ComplexDeinterleavingPass (PR #112875)

[antoine moynault via llvm-commits]

antmox wrote:

And
https://lab.llvm.org/buildbot/#/builders/41/builds/4172
https://lab.llvm.org/buildbot/#/builders/4/builds/4281
https://lab.llvm.org/buildbot/#/builders/199/builds/263

https://github.com/llvm/llvm-project/pull/112875