[llvm] [AArch64] Fall back to SelectionDAG ISel if GISel is not feasible. (PR #196343)

[Benjamin Maxwell via llvm-commits]

https://github.com/MacDue approved this pull request.


Thanks, this LGTM, and a little clearer too. 

Though I do wonder if `fallBackToDAGISel` should also be controlling when GISel is enabled (it looks like we now enable GISel when it's disabled, then fallback for cases where it shouldn't be enabled https://github.com/llvm/llvm-project/pull/174746/changes#r2812855555, IIUC).

https://github.com/llvm/llvm-project/pull/196343