RFR(S) 8166750: profiling handles statically bindable call sites differently than the interpreter

[Doug Simon]

Thanks for the explanation - maybe you could add it to code as a comment.

Sent from my iPhone

> On 25 Oct 2017, at 6:13 pm, Igor Veresov <igor.veresov at oracle.com> wrote:
> 
> 
> 
>> On Oct 25, 2017, at 3:07 AM, Doug Simon <doug.simon at oracle.com> wrote:
>> 
>>  581 
>>  582             // Fixup the case of C1's inability to optimize profiling of a statically bindable call site
>>  583             if (entries == 1) {
>>  584                 counts[0] = totalCount;
>>  585             }
>>  586 
>> But what happens if we're looking at a profile from the interpreter? In that case, won't totalCount == 0 && counts[0] have the right value? In which case, the above fixup will lose this information. Maybe it should be:
>> 
>>     counts[0] += totalCount;
> 
> 
> If it’s pure interpreter you’d have entries == 0, so this fixup won’t fire. Also totalCount at the point of the fixup is a sum of every counter in profile (for all the types + the counter for types that weren’t recorded). So what the fixup does is that it attributes all the counts to the first type (if it’s a monomorphic call site).
> 
> igor
> 
>> 
>> -Doug
>> 
>>> On 25 Oct 2017, at 05:52, Igor Veresov <igor.veresov at oracle.com> wrote:
>>> 
>>> This a fix from Tom that I ported to all architectures and the new repo structure. While that fix doesn’t not solve the problem of the interpreter-C1 profiling style discrepancy completely it speeds up profiling of the statically bindable call sites and we’d like to push that. I also added a bit of a code to JVMCI to do the profile fix up analogous to what happens in CI.
>>> 
>>> Webrev: http://cr.openjdk.java.net/~iveresov/8166750/webrev.01/
>>> JBS: https://bugs.openjdk.java.net/browse/JDK-8166750
>>> 
>>> Thanks,
>>> igor
>> 
> 
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