[llvm] [SelectionDAG][PPC][SystemZ] Fix GET_DYNAMIC_AREA_OFFSET chain result (PR #116507)

[Ulrich Weigand via llvm-commits]

uweigand wrote:

I don't quite see what this chain is intended to accomplish.  At least on SystemZ, `GET_DYNAMIC_AREA_OFFSET` returns a value that is constant everywhere within the given function (it can differ between functions).  So there is no reason to tie its evaluation to any particular place (as enforced by a chain), and the back-end currently optimizes resolution of `ADJDYNALLOC` based on that property.

I believe the same should be true for PowerPC as well, although they may not optimize `GET_DYNAMIC_AREA_OFFSET` as much as we do.


https://github.com/llvm/llvm-project/pull/116507