RFR: 8271140: Fix native frame handling in vframeStream::asJavaVFrame()

[Andreas Woess]

On Thu, 22 Jul 2021 22:17:21 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> Follow-up to https://github.com/openjdk/jdk/pull/4625 ([JDK-8269592](https://bugs.openjdk.java.net/browse/JDK-8269592)) which added support for native frames to `vframeStreamCommon::asJavaVFrame()`. This change was not correct when `asJavaVFrame()` is called for a native frame that is the last frame on the stack (i.e. the first frame in the stream), in which case there's no `_prev_frame` yet. We don't actually need the extended frame information for native frames, so the fix is to just use the vframeStream's `_frame` and `_reg_map` for native frames.
>> Extended the test from JDK-8269592 to cover this case.
>
> test/hotspot/jtreg/compiler/jvmci/compilerToVM/IterateFramesNative.java line 47:
> 
>> 45:  *                   -XX:+DoEscapeAnalysis -XX:-UseCounterDecay
>> 46:  *                   compiler.jvmci.compilerToVM.IterateFramesNative
>> 47:  * @run main/othervm -Xbatch -Xcomp -Xbootclasspath/a:.
> 
> I think `-Xcomp` implies `-Xbatch`.
> I think you should add `-XX:CompileOnly=jdk.vm.ci.hotspot.CompilerToVM::iterateFrames` since you only really care about that method being compiled for sake of the test.

Hm, actually, I don't really need to use `-Xcomp` since the test should already trigger compilation anyway. It was just a way to ensure it's really compiled. I'll replace it with an assert in the test that the method is compiled.

> test/hotspot/jtreg/compiler/jvmci/compilerToVM/IterateFramesNative.java line 50:
> 
>> 48:  *                   -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
>> 49:  *                   -XX:+UnlockExperimentalVMOptions -XX:+EnableJVMCI
>> 50:  *                   -XX:+DoEscapeAnalysis -XX:-UseCounterDecay
> 
> Are the `-XX:+DoEscapeAnalysis -XX:-UseCounterDecay` options really needed?

Probably copied them from somewhere, I think they're irrelevant and will remove them.

-------------

PR: https://git.openjdk.java.net/jdk/pull/4872