Comments on: Load unsigned and better Compressed Oops http://blog.juma.me.uk/2009/04/03/load-unsigned-and-better-compressed-oops/ Thu, 14 Jul 2011 17:33:59 +0000 hourly 1 http://wordpress.com/ By: Ismael Juma http://blog.juma.me.uk/2009/04/03/load-unsigned-and-better-compressed-oops/#comment-243 Fri, 15 May 2009 04:59:24 +0000 http://blog.juma.me.uk/?p=107#comment-243 Hi Scott,

As far as I understand, the change made it into HS15 but not HS14. 6u14 is based on the latter, so I don’t expect it to be in that release (note that the matching numbers are simply a coincidence).

I don’t think Sun has announced what update release after 6u14 will include a new HotSpot, so I can’t say if 6u16 is the one.

Best,
Ismael

]]> By: Scott C. http://blog.juma.me.uk/2009/04/03/load-unsigned-and-better-compressed-oops/#comment-242 Thu, 14 May 2009 22:28:00 +0000 http://blog.juma.me.uk/?p=107#comment-242 Is the better CompressedOops by Vladimir going to be in 6u14? Or will we have to wait until u16?

The change seems to be 6791178 — I’m trying to figure out if that made it out of openjdk to the 6u14 stuff or not…

]]> By: Ismael Juma http://blog.juma.me.uk/2009/04/03/load-unsigned-and-better-compressed-oops/#comment-191 Fri, 03 Apr 2009 15:26:53 +0000 http://blog.juma.me.uk/?p=107#comment-191 Very interesting Cliff.

The Azul VM certainly sounds very nifty. It would certainly be nice if some stuff could be put back to the open source HotSpot, but I understand that it’s not a simple decision given business interests and such.

Regarding tiered compilation, great that you guys got that to work to the point where it could be enabled by default (and for over a year at that). I was following a similar project for HotSpot with interest, but it seems like that is stalled at the moment.

Ismael

]]> By: Cliff Click http://blog.juma.me.uk/2009/04/03/load-unsigned-and-better-compressed-oops/#comment-190 Fri, 03 Apr 2009 15:20:55 +0000 http://blog.juma.me.uk/?p=107#comment-190 Thanks… we’re having the internal debate about whether or not to start putting stuff back to the open source HotSpot.

We’ve made a huge ton of changes; our VM is much smaller & lighter… and might be more performant on an X86. E.g. we’ve got tiered compilation turned on by default, and have had it on for over a year.

Cliff

]]> By: Ismael Juma http://blog.juma.me.uk/2009/04/03/load-unsigned-and-better-compressed-oops/#comment-188 Fri, 03 Apr 2009 14:59:49 +0000 http://blog.juma.me.uk/?p=107#comment-188 Hi Cliff,

Thanks for the comment. I suggest sending an email to the hotspot-compiler-dev mailing list so that the people who worked on and reviewed the change can benefit from your insight (and possibly explain their reasoning). :)

Best,
Ismael

]]> By: Cliff Click http://blog.juma.me.uk/2009/04/03/load-unsigned-and-better-compressed-oops/#comment-187 Fri, 03 Apr 2009 14:51:24 +0000 http://blog.juma.me.uk/?p=107#comment-187 But… the unsigned variants *belong* in the Matcher! If you put them in the core optimizer, then *everyplace* there’s a reference to ‘LoadI’ or ‘LoadB’ you have to add the unsigned variants, or you’ll screw up existing optimizations.

If you’re seeing missed unsigned opportunities, the Right Thing To Do is to canonicalize the IR such that the masks end up next to the loads.

Final note: Azul engineering has been busy in the HotSpot compiler business as well, including doing a number of optimizations related to removing bogus masks.

Cliff
Architect of the Server compiler

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