Where does the openjdk JVM interpreter execute the bytecode instanceof operation

[Julian Waters]

Glad to help! Paging for David and Thomas again, who'll probably be able to
help you more than I can

best regards,
Julian

On Fri, May 3, 2024 at 3:54 PM zhengxianwei <baikaishiuc at gmail.com> wrote:

> I carefully analyzed it and found that what you said is actually correct.
>
> I didn't understand it correctly initially.
>
> Thanks again for your explanation
>
> On Fri, May 3, 2024 at 11:03 AM Julian Waters <tanksherman27 at gmail.com>
> wrote:
>
>> Hi Xian Wei,
>>
>> No, you are right! The code in templateTable_x86.cpp that you linked to
>> in your post is not part of the Just in Time Compilers, it is part of the
>> x86 Interpreter! The Java HotSpot VM actually has 2 different Interpreters,
>> the primary Interpreter is written in large chunks of assembly specific to
>> each platform, which is then processed by the HotSpot macro assemblers. The
>> bytecodeInterpreter.cpp file you linked to is part of the second and less
>> often used Interpreter, which is why modifying the bytecodeInterpreter.cpp
>> instanceof implementation did nothing in your case (The Interpreter used
>> actually depends on the platform, and the secondary Interpreter is not used
>> on ARM or x86). The details on the macro assemblers unfortunately elude me
>> since I am not a HotSpot expert (Although I hope to be one day), but to
>> understand how instanceof works on x86 and ARM, you need to understand both
>> x86 and ARM assembly. The Interpreter's instanceof opcode is implemented on
>> x86 in
>> https://github.com/openjdk/jdk/blob/6bef0474c8b8773d0d20c0f25c36a2ce9cdbd7e8/src/hotspot/cpu/x86/templateTable_x86.cpp#L4243
>> and on ARM, it is implemented in
>> https://github.com/openjdk/jdk/blob/6bef0474c8b8773d0d20c0f25c36a2ce9cdbd7e8/src/hotspot/cpu/arm/templateTable_arm.cpp#L4182
>>
>> Happy to help!
>>
>> best regards,
>> Julian
>>
>
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