RFR: 8363620: AArch64: reimplement emit_static_call_stub() [v3]

[Fei Gao]

On Thu, 4 Dec 2025 11:54:31 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/compiledIC_aarch64.cpp line 180:
>> 
>>> 178:     nativeCallTrampolineStub_at(trampoline_stub_addr)->set_destination(stub);
>>> 179:   }
>>> 180: 
>> 
>> Suggestion:
>> 
>> 
>>   // This code is executed while other threads are running. We must                                                                                                                  
>>   // ensure that at all times there is a valid path of execution. A                                                                                                                  
>>   // racing thread either observes a call (possibly via a trampoline)                                                                                                                
>>   // to SharedRuntime::resolve_static_call_C or a complete call to the                                                                                                               
>>   // interpreter.                                                                                                                                                                    
>>   //                                                                                                                                                                                 
>>   // If a racing thread observes an updated direct branch at a call                                                                                                                  
>>   // site, it must also observe all of the updated instructions in the                                                                                                               
>>   // static interpreter stub.                                                                                                                                                        
>>   //                                                                                                                                                                                 
>>   // To ensure this, we first update the static interpreter stub, then                                                                                                               
>>   // the trampoline, then the direct branch at the call site.                                                                                                                        
>>   //                                                                                              ...
>
> Here's my thinking:
> 
> First say what you want to achieve and why.
> 
> Be definite about what you say in comments. Avoid words like "generally", for example. Always use the strongest words you can. For example, "because" is stronger than "since".
> 
> Be concise. The purpose of all code is to ensure correctness, so you don't have to say so.
> 
> This comment is not perfect, so feel free to amend anything that is unclear.

@theRealAph Many thanks for your feedback and your time! 

I’ve updated the commit with your suggestion. I made a small adjustment on top of what you proposed—hope it’s not unnecessary.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26638#discussion_r2593083821