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

[via llvm-commits]

zmodem wrote:

> 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).

That's the point: a counter above 2^56 strongly indicates corrupt data, which can be flagged as an error.

> 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.

I don't think is something the user should have to think about, so I don't think we should have an option.

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