RFR: 8316694: Implement relocation of nmethod within CodeCache [v4]

[Evgeny Astigeevich]

On Fri, 14 Mar 2025 21:57:21 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:
> 
>   Fix build issues

src/hotspot/share/prims/whitebox.cpp line 1640:

> 1638: WB_END
> 1639: 
> 1640: WB_ENTRY(void, WB_RelocateAllNMethods(JNIEnv* env))

We don't need it.

test/hotspot/jtreg/compiler/whitebox/DeoptimizeRelocatedNMethod.java line 2:

> 1: /*
> 2:  * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.

Fix the copyright.

test/hotspot/jtreg/compiler/whitebox/RelocateAndDeoptmizeAllNMethods.java line 98:

> 96: import jdk.test.whitebox.WhiteBox;
> 97: 
> 98: public class RelocateAndDeoptmizeAllNMethods {

Please rewrite the test to the following which more practical:
1. Compile a set of Java methods with C1. There should be a call graph of the methods with one entry point which produces a result.
2. Call the entry point to produce a result.
3. Relocate nmethods.
4. Call the entry point to produce a new result.
5. Compare the results.
6. Deoptimize the nmethods.
7. Check Java methods don't have nmethods.

Do the same for C2.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23573#discussion_r1998694877
PR Review Comment: https://git.openjdk.org/jdk/pull/23573#discussion_r1998692849
PR Review Comment: https://git.openjdk.org/jdk/pull/23573#discussion_r1998689847