RFR: 8359064: Expose reason for marking nmethod non-entrant to JVMCI client [v3]

[Doug Simon]

On Thu, 12 Jun 2025 00:27:55 GMT, Cesar Soares Lucas <cslucas at openjdk.org> wrote:

>> We recently introduced a way to set the reason why a nmethod was being marked as `not entrant`, see [here](https://github.com/openjdk/jdk/pull/23980) and [here](https://github.com/openjdk/jdk/pull/25338).
>> 
>> This PR is to expose in the JVMCI interface the reason why the nmethod was flagged as `not entrant`. This will allow JVMCI-based compilers to implement heuristics to handle re-compilations differently based on what happened to earlier versions of a method, for instance, this will likely be used to address this [RFE in Truffle](https://github.com/oracle/graal/issues/11045
>> ). 
>> 
>> Tested on Linux x86_64, ARM with JTREG tier 1-3.
>
> Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Refactoring: move changes to HotSpotNmethod class; remove enum on Java side; rename field to invalidationReason

src/hotspot/share/code/nmethod.hpp line 476:

> 474:   // If you change anything in this enum please patch
> 475:   // vmStructs_jvmci.cpp accordingly.
> 476:   enum class ChangeReason : u1 {

I would also suggest this enum be changed to `InvalidationReason` but that can be considered as a potential follow up.

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotNmethod.java line 213:

> 211:      * @return a String describing the reason why this nmethod was invalidated.
> 212:      */
> 213:     public String getInvalidationReasonString() {

I would have stuck with getInvalidationReasonDescription but can live with getInvalidationReasonString.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25706#discussion_r2142359399
PR Review Comment: https://git.openjdk.org/jdk/pull/25706#discussion_r2142360949