RFR(S): 8193927: Optimize scanning code for oops.

[Lindenmaier, Goetz]

Hi Volker, 

you are right, encapsulating it in a function is a better solution:
http://cr.openjdk.java.net/~goetz/wr17/8193927-oopsInCode/webrev.02

Making it switchable would require changes to x86, which is 
not my scope.

Best regards,
  Goetz.

> -----Original Message-----
> From: Volker Simonis [mailto:volker.simonis at gmail.com]
> Sent: Donnerstag, 21. Dezember 2017 14:51
> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>
> Cc: hotspot-compiler-dev at openjdk.java.net
> Subject: Re: RFR(S): 8193927: Optimize scanning code for oops.
> 
> Hi Goetz,
> 
> this seems to be a little strange flag for me because it can not be
> used for really controlling the emission of immediate oops. It only
> records if a platform can emit immediate oops or not.
> 
> So wouldn't it be better to either have a flag like
> "EmitImmediateOops" which really controls the emission of immediate
> oops. I.e. it could be used to switch the emission of immediate oops
> off even on platforms which usually do that. Or if that's not
> reasonable, don't introduce a new flag at all but just declare a
> platform specific method instead which returns if immediate oops can
> be emitted on that platform or not.
> 
> Thanks,
> Volker
> 
> On Thu, Dec 21, 2017 at 9:30 AM, Lindenmaier, Goetz
> <goetz.lindenmaier at sap.com> wrote:
> > Hi,
> >
> > Some platforms don't emit immediate oops to the code. If so, scans
> > of the code for oops can be skipped.
> >
> > Add flag ImmediateOopsEmitted to each platform specifying the behavior.
> > Only search code for immediate oops if this flag is set. Make sure no
> > oops are emitted to code if the flag is not set.
> >
> > @aarch people: should the flag set to 'false' on aarch/arm?  So far it
> > is true, which defaults to the old behavior.
> >
> > Please review this change. I please need a sponsor.
> > http://cr.openjdk.java.net/~goetz/wr17/8193927-oopsInCode/webrev.01/
> >
> > Best regards,
> >   Goetz