[llvm] [SelectionDAG] Add initial support for nneg flag on ISD::ZERO_EXTEND. (PR #70872)

[Nikita Popov via llvm-commits]

nikic wrote:

> > Do we need to add the flag to the zext_in_reg nodes? This question is complicated by the fact that comments in DAGCombine mention such a node, but it doesn't appear to be in the ISDOpcodes.h list.
> 
> zext_in_reg is ISD::AND with a trailing ones mask.

There is ZERO_EXTEND_VECTOR_INREG though, so I guess the question applies to that one.

https://github.com/llvm/llvm-project/pull/70872