[llvm] [SLP]Reduce number of alternate instruction, where possible (PR #128907)

[via llvm-commits]

dyung wrote:

@alexey-bataev, one of our internal tests started hitting a build error which I bisected back to this change. I have put the details in issue #130743, can you take a look?

https://github.com/llvm/llvm-project/pull/128907