RFR: 8358329: AArch64: emit direct branches in static stubs for small code caches [v2]

[Mikhail Ablakatov]

On Tue, 10 Jun 2025 10:37:00 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Mikhail Ablakatov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   address review comments: use pd_patch_instruction directly
>>   
>>   MacroAssembler::pd_patch_instruction can distinguish between the `b`
>>   and `movk movz movz br` sequences. Strictly speaking, the method
>>   patches not a single instruction but a semantically joint sequence of
>>   instructions. Use it directly instead of `NativeJump` and
>>   `NativeGeneralJump` wrapper classes to simplify the implementation and
>>   get rid of an extra icache invalidation.
>>   
>>   Other changes in the patch simply clean up code that became redundant.
>
> src/hotspot/cpu/aarch64/compiledIC_aarch64.cpp line 106:
> 
>> 104:   } else {
>> 105:     NativeJump::insert(method_holder->next_instruction_address(), entry);
>> 106:   }
> 
> We're also calling `ICache::invalidate_range` twice, which is kinda lame. That perhaps doesn't matter because calls to `CompiledDirectCall::set_to_interpreted()` are fairly rare.

Agreed, thank you for spotting that. Should not be the case any longer.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25702#discussion_r2140504282