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

[Rahman Lavaee via llvm-commits]

rlavaee wrote:

IIUC, these functions do not satisfy weak ordering. Suppose a series of similar BFI edge frequencies are considered where
w_1 ~< w_2 ~< w_3 <~ ... <~ w_n
and
w_1 !lessWithTolerance w_2  !lessWithTolerance ... !lessWithTolerance w_n

We can still have w_1 lessWithTolerance w_n.

In that case, is it a good idea to expose these as pseudo-comparators?

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