ea2f5395b1
Updates SimplifyCFG to avoid jump threading through loop headers if -keep-loops is requested. Canonical loop form requires a loop header that dominates all blocks in the loop. If we thread through a header, we risk breaking its domination of the loop. This change avoids this issue by conservatively avoiding threading through headers entirely. Fixes: https://github.com/llvm/llvm-project/issues/151144