RFR: 8221542: ~15% performance degradation due to less optimized inline decision

[Vladimir Ivanov]

>> After some explorations I decided to keep original behavior for 
>> immature profiles (profile.count == -1).
> 
> I agree.
> 
> I have two questions here.
> 
> 1. What's the difference of the following two if statements?
> -------------------------------------------------
> +  if (!callee_method->was_executed_more_than(0))  return true; // 
> callee was never executed
> +
> +  if (caller_method->is_not_reached(caller_bci))  return true; // call 
> site not resolved
> -------------------------------------------------
> I think only one of them is needed.

The checks are complimentary: one inspects callee and the other looks at 
call site.

"!callee_method->was_executed_more_than(0)" ensures that callee was 
executed at least once.

"caller_method->is_not_reached(caller_bci)" inspects the state of the 
call site. If corresponding CP entry is not resolved, then the call site 
isn't reached. If is_not_reached() returns false, it's not a definitive 
answer: there's still a chance the site is not reached - consider the 
case of virtual calls where callee_method may differ for the same 
resolved method.

> 2. Does the assert in InlineTree::is_not_reached(...) make sense?
> Since we have
> -------------------------------------------------
> if (profile.count() > 0)   return false; // reachable according to profile
> -------------------------------------------------
> and
> -------------------------------------------------
> if (profile.count() == -1) {...}
> -------------------------------------------------
> before
> -------------------------------------------------
> assert(profile.count() == 0, "sanity");
> -------------------------------------------------
> is the assert redundant?

Asserts are intended to be redundant :-) But still catch bugs from time 
to time.

This one, in particular, checks invariant on profile.count() >= -1 
(which is not very useful by itself), but also stresses that 
"profile.count() == 0" case is being processed.

Best regards,
Vladimir Ivanov