[llvm] LV: Expand llvm.histogram intrinsic to support umax, umin, and uadd.sat operations (PR #127399)

[Graham Hunter via llvm-commits]

huntergr-arm wrote:

> > > It would be good to add the intrinsics together with initial lowering as separate patch, including codegen tests.
> > 
> > 
> > It would still be good to separate the changes for adding the new intrinsics from using them in LV. Also the description/titl needs updating.
> 
> I updated the title and description. I'm not sure I understand what you're proposing. Adding the intrinsics without using them in LV seems redundant. What's the point of adding unused intrinsics? If you meant something else, please elaborate on what's needs to be done.
> 
> Thanks in advance for taking your time and reviewing.

Splitting it into separate patches is often done to make it easier to review or limit the amount of code that must be examined if a bug is found later in a given commit. I did create a separate patch for the initial histogram intrinsic in fbb37e960616efcf7cd5c1ebbe95f75c65d565dc, along with AArch64 codegen. The use in LoopVectorize came later in 6f1a8c2da278a04565877e277bc4d5b70055ac74.

https://github.com/llvm/llvm-project/pull/127399