[llvm] [AArch64][SelectionDAG] Implement vector splitting for histogram intrinsic (PR #103037)

[Sander de Smalen via llvm-commits]

sdesmalen-arm wrote:

On the commit message, the patch is also doing type promotion, so maybe you want to rephrase it to something slightly more generic, e.g. `Vector splitting and promotion for histogram` ?

https://github.com/llvm/llvm-project/pull/103037