[llvm] MachineBlockPlacement: Add tolerance to comparisons (PR #67197)

[via llvm-commits]

spupyrev wrote:

I am curios if there is a way to teach BFI to return appropriately rounded values, so that we don't modify downstream algorithms? Similarly, do you think lower bits in the frequencies provide any signal, or are they just noise that always needs to be discarded?

https://github.com/llvm/llvm-project/pull/67197