RFR(XS): 8030976: untaken paths should be more vigorously pruned at highest optimization level

[Rickard Bäckman]

Christian,

sorry, had to rerun a bunch of things.

jbb2005-tuned: no significant change
jvm2008-compress: no significant change
jvm2008-crypto: no significant change
jvm2008-derby: + 5-6%
jvm2008-startup: no significant change
jvm2008-xml: + 2-3%
volano29: no significant change

Thanks
/R

On 05/22, Christian Thalinger wrote:
> 
> On May 22, 2014, at 4:53 AM, Rickard Bäckman <rickard.backman at oracle.com> wrote:
> 
> > Hi all,
> > 
> > can I please have reviews for this change.
> > The patch makes C2 place uncommon traps on previously untaken branches
> > much more aggressively (we are simply trusting the profiling more). 
> > This improves performance for a couple of different patterns.
> > 
> > Example:
> > 
> > class Test {
> >  public int[] array = new int[] = { 1, 1, 2, 3, 5, 8, 13 };
> > 
> >  public void some_method() {
> >    for (int i = 0; i < array.length; i++) {
> >      if (array[i] < 255) {
> >        some_call();
> >      } else {
> >        some_other_call();
> >      }
> >    }
> >  }
> > }
> > 
> > Where we previously if the else branch had never been taken rarely would
> > inline the some_other_call and when array escapes we can't make
> > assumptions on non-changing lengths, call killing registers, etc.
> > 
> > On some of the Nashorn benchmark this patch increases score by 35%,
> > others don't see any change at all. No difference on SpecJBB 2005.
> > More performance numbers / microbenchmark in the comments of the bug.
> 
> One comment says:
> 
> "Trying to get numbers from some bigger benchmarks as well.”
> 
> Did you only run SPECjbb2005 or others as well?
> 
> > 
> > Webrev: http://cr.openjdk.java.net/~rbackman/8030976/
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8030976
> > 
> > Thanks
> > /R
> 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 836 bytes
Desc: Digital signature
URL: <http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/attachments/20140603/3c863a5a/signature-0001.asc>