RFR: 8275908: Record null_check traps for calls and array_check traps in the interpreter

[Volker Simonis]

On Thu, 25 Nov 2021 09:29:12 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> `null_checks` occurring at invoke bytecodes are currently not recorded by the profiler. This leads to unnecessary uncommon traps, deoptimizations and recompilations for exceptions which already occurred before the compilation (i.e. are "hot"). This change fixes the problem in the interpreter.
>> 
>> `array_checks` are currently recorded as `class_checks` in the interpreter and therefore not recognized by the compiler. This again leads to uncommon traps, deoptimizations and recompilations. This change unifies the handling of `array_checks` in the interpreter and compiler and prevents unnecessary recompilation.
>> 
>> The test is a stripped down version of a test which was developed for [JDK-8273563: Improve performance of implicit exceptions with -XX:-OmitStackTraceInFastThrow](https://bugs.openjdk.java.net/browse/JDK-8273563) (still [under review](https://github.com/openjdk/jdk/pull/5488)). It introduces an extension to the Whitebox API to expose the decompile, deopt and trap counters which is also required for testing [JDK-8273563](https://bugs.openjdk.java.net/browse/JDK-8273563). I think (and hope) it will also be helpful for others in the future.
>
> test/hotspot/jtreg/compiler/exceptions/OptimizeImplicitExceptions.java line 141:
> 
>> 139:     private static void printCounters(TestMode testMode, ImplicitException impExcp, Method throwImplicitException_m, int invocations) {
>> 140:         System.out.println("testMode=" + testMode + " exception=" + impExcp + " invocations=" + invocations + "\n" +
>> 141:                            "decompilecount=" + WB.getMethodDecompileCount(throwImplicitException_m) + " " +
> 
> `getMethodDecompileCount()` seems only to be used to print the counters here but is not verified otherwise. If it is is not too complicated, could a specific test for it be added as well?

Hm, it was used in JDK-8275908 before this fix. Now, with this fix we don't get any recompiles any more :)

The tests is already quite big so I've added a separate test `test/hotspot/jtreg/compiler/uncommontrap/Decompile.java` to verify the new WhiteBox methods introduced by  this change.

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PR: https://git.openjdk.java.net/jdk/pull/6541