[llvm] [ConstantFolding] Fold sqrt poison -> poison (PR #141821)

[Luke Lau via llvm-commits]

lukel97 wrote:

I've updated this to just handle this in `ConstantFoldScalarCall1`, and I've left around the test cases for scalable vectors + nnan/ninf for later (let me know if you want me to take them out though)

I'll work on a patch to constant fold scalable intrinsics where the operands are splatted next.

But I guess we'll still need to figure out how to handle the case whenever not all arguments are constant, e.g only one operand is poison. Should that be handled by ValueTracking?

https://github.com/llvm/llvm-project/pull/141821