[llvm] [LLVM][InstSimplify] Add folds for SVE integer reduction intrinsics. (PR #167519)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

> > NOTE: I did not spot any other simplifications for target specific intrinsics but they do exist in ConstantFold, which InstSimplify uses, so presumably this is allow?
> 
> It's allowed, but unless you specifically need this in InstSimplify, handling this via the InstCombine TTI hooks might be cleaner? No strong opinion though.

Thanks, noted. In this case InstCombine was not sufficient because I wanted to activate a code path in FoldOpIntoSelect that explicitly requires simplification (via simplifyOperationIntoSelectOperand).

https://github.com/llvm/llvm-project/pull/167519