[8u] RFR: 8221355: Performance regression after JDK-8155635 backport into 8u

[Severin Gehwolf]

Hi Aleksey,

Thanks for the review!

On Wed, 2019-04-10 at 13:25 +0200, Aleksey Shipilev wrote:
> On 4/10/19 1:18 PM, Severin Gehwolf wrote:
> > Could I please get a review of this 8u212 performance regression fix?
> > webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8221355/01/webrev/
> 
> This is not the same patch that Oracle apparently pushed, or that I tested myself. Compare with:
>   http://cr.openjdk.java.net/~shade/8221355/8221355-01.patch
> 
> The difference is not critical, but better match?

Is there a reason to keep unused local variable 'can_access_non_heap'
around in JDK 8? It makes sense for the JDK 9 change as its being used
further down in the same function:
http://hg.openjdk.java.net/jdk-updates/jdk9u/hotspot/file/22d7a88dbe78/src/share/vm/opto/library_call.cpp#l2493

That's not the case for JDK 8u, though. Thoughts?

The left over comment is misleading, though, which I've now removed:
http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8221355/02/webrev/

> It should definitely be in 8u-dev (next CPU). I'll leave the decision for 8u (current CPU) to 8u
> maintainers.

Yes, I'd be aiming this for 8u-dev for now.

Thanks,
Severin