RFR: 8316694: Implement relocation of nmethod within CodeCache [v28]

[Fei Yang]

On Tue, 17 Jun 2025 21:14:56 GMT, Chad Rakoczy <duke at openjdk.org> wrote:

>> This PR introduces a new function to replace nmethods, addressing [JDK-8316694](https://bugs.openjdk.org/browse/JDK-8316694). It enables the creation of new nmethods from existing ones, allowing method relocation in the code heap and supporting [JDK-8328186](https://bugs.openjdk.org/browse/JDK-8328186).
>> 
>> When an nmethod is replaced, a deep copy is performed. The corresponding Java method is updated to reference the new nmethod, while the old one is marked as unused. The garbage collector handles final cleanup and deallocation.
>> 
>> This change does not modify existing code paths and therefore does not benefit much from existing tests. New tests were created and confirmed to pass on x64/aarch64 for slowdebug/fastdebug/release.
>
> Chad Rakoczy has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use new _metadata_size instead of _jvmci_data_size

src/hotspot/share/code/relocInfo.cpp line 415:

> 413: // We must check that the new offset can still fit in the instruction
> 414: // for architectures that have small branch ranges
> 415: #if defined(AARCH64) || defined(RISV)

Should be `RISC-V` instead of `RISV`.

src/hotspot/share/code/relocInfo.cpp line 419:

> 417:     if (NativeCall::is_call_at(addr())) {
> 418:       NativeCall* call = nativeCall_at(addr());
> 419:       address trampoline = call->get_trampoline();

We don't have this `call->get_trampoline()` method for RISC-V now. Trampoline call for RISC-V was deprecated by https://bugs.openjdk.org/browse/JDK-8332689 and later removed by https://bugs.openjdk.org/browse/JDK-8343430.
So I guess RISC-V is not affected here in this case? CC: @robehn

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PR Review Comment: https://git.openjdk.org/jdk/pull/23573#discussion_r2153410156
PR Review Comment: https://git.openjdk.org/jdk/pull/23573#discussion_r2153416320