RFR (16): JFR: Separate metadata per JVM-feature

[Roman Kennke]

Thanks, Erik. I can do those changes. But can we first agree with Erik
Gahlin if we want this change at all?

Thanks,
Roman

On Thu, 2020-07-23 at 17:23 -0700, Erik Joelsson wrote:
> Build changes look ok to me. I would prefer if the long "COMMAND"
> line 
> was broken up though as the side by side diff is already forcing a
> side 
> scroll on my smaller monitor.
> 
> /Erik
> 
> On 2020-07-23 10:48, Roman Kennke wrote:
> > This is a fall-out from my Shenandoah upstreaming work in JDK11,
> > where
> > I made a similar change in order to separate-out Shenandoah parts
> > from
> > JFR build when Shenandoah is disabled.
> > 
> > Currently, all JFR metadata is collected in a single metadata.xml
> > file.
> >  From those, the build machinery generates headers and some other
> > things
> > from it. For JVM-feature-specific metadata, this leads to stuff
> > generated that doesn't exist when the feature is excluded from the
> > build. For example, when disabling Shenandoah, we still need to
> > compile
> > empty methods in jfrPeriodic.cpp to satisfy the generated code.
> > 
> > The fix is to extend the code-generator to accept multiple
> > metadata-
> > *.xml files and concatenate the parsing. The version in JDK16
> > accepts a
> > --xml $FILENAME argument, and I'm extending this to --xml
> > $FILENAME1:$FILENAME2:.. etc, i.e. multiple filenames separated by
> > colon. It allows empty filenames, e.g. metadata.xml::: would be
> > parsed
> > as a single file metadata.xml files. That makes the build machinery
> > much simpler.
> > 
> > I also did the relevant metadata-separation for Shenandoah because
> > that
> > is what I care about myself. If you'd like other parts treated the
> > same, just let me know.
> > 
> > Bug:
> > https://bugs.openjdk.java.net/browse/JDK-8250218
> > Webrev:
> > http://cr.openjdk.java.net/~rkennke/JDK-8250218/webrev.00/
> > 
> > Testing: build with and without Shenandoah, run some tests, I'd
> > await
> > submit-repo results before pushing.
> > 
> > Can I please get a review?
> > 
> > Thanks!
> > Roman
> >