[llvm] [AMDGPU] SelectionDAG divergence tracking should take into account Target divergency. (PR #147560)

[David Stuttard via llvm-commits]

dstutt wrote:

This change is causing us issues downstream - we've had to revert it there.
Issue arises when using wwm intrinsic. A quick fix was to add detection of WWM/(WQM?) intrinsics in isSingleLaneExecution, but that's probably too expensive.
Either way, this change breaks in this situation and causes failures for Vulkan CTS subgroup operations.

Does this need reverting here as well - it can break in the presence of wwm intrinsics.

https://github.com/llvm/llvm-project/pull/147560