RFR: 8261447: MethodInvocationCounters frequently run into overflow [v8]

[Lutz Schmidt]

On Tue, 2 Mar 2021 16:34:26 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Lutz Schmidt has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   comment changes requested by TheRealMDoerr
>
> src/hotspot/cpu/x86/vtableStubs_x86_32.cpp line 159:
> 
>> 157:     return NULL;
>> 158:   }
>> 159: 
> 
> Why you did not update asm instruction to update `nof_megamorphic_calls` in this file?

The reason is plain simple: there is no incrementq() for x86_32. I could emulate that with a few lines like
    address ctrAddr = (address)SharedRuntime::nof_megamorphic_calls_addr();
    __ lea(rscratch1, ExternalAddress(ctrAddr));
    __ addl(Address(rscratch1, 0), 1);
    __ adcl(Address(rscratch1, 4), 0);
Not sure if that would be desirable here. Just let me know. As is, the code just updates the less significant half of the 8-byte counter.

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