[llvm] [SLP] Match poison as instruction with the same opcode (PR #115946)

[Maksim Levental via llvm-commits]

makslevental wrote:

> What is the target triple, nvptx64-unknown-unknown?

We/Triton leaves it "empty" for internal reasons that I currently don't have context on https://github.com/triton-lang/triton/blob/main/python/src/llvm.cc#L333-L339.

https://github.com/llvm/llvm-project/pull/115946