[llvm] [llvm-profdata] Emit warning when counter value is greater than 2^56. (PR #69513)

[via llvm-commits]

https://github.com/xur-llvm commented:

It seems to me 2^56 is rather big for an instrumentation counter value. Even we use uint64 as the counter, the real counter value should not be near to this value (even considering scaling and merging).
In this sense, I don't like a fix value. Maybe a value can be changed by an options.
I also would suggest a smaller default value. 

https://github.com/llvm/llvm-project/pull/69513