[llvm] [AMDGPU] Model structured control-flow lane masks as i1 (PR #209158)

[Petar Avramovic via llvm-commits]

https://github.com/petar-avramovic commented:

Requires much larger audience,
but think this should attempt to add some test cases with control flow intrinsics using i1 instead of s32/s64 for start, make sure it works. Maybe hide i1 lane mask mode (for annotate control flow) behind command line option to test it in detail on everything first

https://github.com/llvm/llvm-project/pull/209158