[llvm] [SLP]Reduce number of alternate instruction, where possible (PR #123360)

[Vladimir Vereschaka via llvm-commits]

vvereschaka wrote:

Hi @zmodem ,
looks like reverting of this MR caused the test failures on the [llvm-clang-x86_64-expensive-checks-ubuntu](https://lab.llvm.org/buildbot/#/builders/187) builder for some reason:
* LLVM::materialize-frame-index-sgpr.ll
* LLVM::materialize-frame-index-sgpr.gfx10.ll
* LLVM::schedule-amdgpu-tracker-physreg-crash.ll

https://lab.llvm.org/buildbot/#/builders/187/builds/4783

https://github.com/llvm/llvm-project/pull/123360