[llvm] [LoopFusion] Validate loop structure before creating LoopCandidates (PR #192280)

[Madhur Amilkanthwar via llvm-commits]

madhur13490 wrote:

@amehsan @CongzheUalberta In the current revision, I am taking suggestion from @amehsan as to depend on header than preheader as it should exist. The current revision has a new optimization remark, removes assert altogether and depends on header while emitting  the existing remark when STATS is enabled. It seem that the assert is there only to ensure that its access is valid in ORE. But, we can't be sure of preheader always. 

I have tested in release and debug binaries and this is fine. Please let me know if there can a better remark message.


https://github.com/llvm/llvm-project/pull/192280