[llvm] [LV] Always emit branch weights for vector epilogue (PR #155437)

[David Sherwood via llvm-commits]

david-arm wrote:

> Hmm that's interesting. Looking at https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Analysis/BlockFrequencyInfoImpl.h#L1351C25-L1351C39, it seems like `BlockFrequencyInfoI` may not use the profile info, if there is not profile counts for the function entry block?

Take a look at https://github.com/llvm/llvm-project/pull/154759. I think the original form of the test llvm/test/Transforms/LoopVectorize/X86/avx512.ll was broken by this PR due to changes in block ordering, despite there being no pre-existing profile info. Perhaps CodeGen doesn't use BlockFrequencyInfoImpl.h?

https://github.com/llvm/llvm-project/pull/155437