On Fri, 8 Oct 2021 23:31:32 GMT, Mandy Chung <mch...@openjdk.org> wrote:
>> This reimplements core reflection with method handles. >> >> For `Constructor::newInstance` and `Method::invoke`, the new implementation >> uses `MethodHandle`. For `Field` accessor, the new implementation uses >> `VarHandle`. For the first few invocations of one of these reflective >> methods on a specific reflective object we invoke the corresponding method >> handle directly. After that we spin a dynamic bytecode stub defined in a >> hidden class which loads the target `MethodHandle` or `VarHandle` from its >> class data as a dynamically computed constant. Loading the method handle >> from a constant allows JIT to inline the method-handle invocation in order >> to achieve good performance. >> >> The VM's native reflection methods are needed during early startup, before >> the method-handle mechanism is initialized. That happens soon after >> System::initPhase1 and before System::initPhase2, after which we switch to >> using method handles exclusively. >> >> The core reflection and method handle implementation are updated to handle >> chained caller-sensitive method calls [1] properly. A caller-sensitive >> method can define with a caller-sensitive adapter method that will take an >> additional caller class parameter and the adapter method will be annotated >> with `@CallerSensitiveAdapter` for better auditing. See the detailed >> description from [2]. >> >> Ran tier1-tier8 tests. >> >> [1] https://bugs.openjdk.java.net/browse/JDK-8013527 >> [2] >> https://bugs.openjdk.java.net/browse/JDK-8271820?focusedCommentId=14439430&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14439430 > > Mandy Chung has updated the pull request incrementally with one additional > commit since the last revision: > > Fix left-over assignment Marked as reviewed by plevart (Reviewer). Hi Mandy, I think this is good as first slab. I don't have anything to add at this point. Some optimization ideas to try as followups. I ran benchmarks myself and the results are similar to yours. Some seem like a regression, but don't have big impact on real-world use case such as Jackson (de)serialization. "Const" class is pretty much the same as with recently improved variant with @Stable fields. I say Go! src/java.base/share/classes/jdk/internal/reflect/MethodHandleCharacterFieldAccessorImpl.java line 137: > 135: { > 136: if (isReadOnly()) { > 137: ensureObj(obj); // throw NPE if obj is null on instance > field I think ensureObj(obj) must go before if statement in setChar ------------- PR: https://git.openjdk.java.net/jdk/pull/5027
