RFR: 8261447: MethodInvocationCounters frequently run into overflow [v2]

[Lutz Schmidt]

On Tue, 2 Mar 2021 21:15:46 GMT, Igor Veresov <iveresov at openjdk.org> wrote:

>> When you increment (2^31-1), you get 2^31 which is 0x80000000. When interpreted as signed int, it is MIN_INT. I don't want that. I want to treat the value as positive number - what it actually is. There is no negative count!
>
> I was trying to make a point that these counters are always < MAX_INT. ```InvocationCounter::count()``` shifts the counter right by 1, ensuring that the sign bit is 0. ```Method::{invocation, backedge, interpreter_invocation}_count()``` can also return ```InvocationCounter::count_limit```, but this one is 2^30, which is also positive.

Slowly, but surely, we are coming to a common understanding. Thanks for educating me. I hadn't seen the range limitation for the counters. Now that I know, I recognise there is some knowledge in my almost faded memory.
OK, these three counters will never get dangerously close to 2^31-1. I will rework the section, remove some checks and casts. This will only happen tomorrow (Wednesday) which starts in 90 minutes in my time zone (GMT+1).

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PR: https://git.openjdk.java.net/jdk/pull/2511