[llvm] [InstCombine] Do not request non-splat vector support in code reviews (NFC) (PR #90709)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> Non-trivial non-splat vector handling has done significant damage to the InstCombine code base in the past (mostly due to the work of a single contributor) and I am quite wary of repeating this mistake nowadays.

I take it this is aimed at me, and I'm sorry if this has caused you problems.

Please can you give examples of the damaging combines?

https://github.com/llvm/llvm-project/pull/90709