RFR[S]:8241874 [PPC64] Improve performance of Long.reverseBytes() and Integer.reverseBytes() on Power9

[Doerr, Martin]

Hi Corey,

please use 2020 for both, the Oracle and the SAP copyright.
Usually, both should be the same, but some people forget to update one of them.

Best regards,
Martin


> -----Original Message-----
> From: Corey Ashford <cjashfor at linux.ibm.com>
> Sent: Donnerstag, 16. April 2020 03:35
> To: Doerr, Martin <martin.doerr at sap.com>
> Cc: Michihiro Horie <HORIE at jp.ibm.com>; hotspot-compiler-
> dev at openjdk.java.net; ppc-aix-port-dev at openjdk.java.net
> Subject: Re: RFR[S]:8241874 [PPC64] Improve performance of
> Long.reverseBytes() and Integer.reverseBytes() on Power9
> 
> Hello Martin,
> 
> I'm having some trouble with my email server, so I'm having to reply to
> your earlier post, but I saw your most recent post on the mailing list
> archive.
> 
> Thanks for reviewing and testing this patch.  I went to look at the
> copyright dates, and see two date ranges: one for Oracle and its
> affiliates, and another for SAP.  In the files I looked at, the end date
> wasn't the same between the two.  Which one (or both) should I modify?
> 
> Thanks,
> 
> - Corey
> 
> On 4/14/20 6:26 AM, Doerr, Martin wrote:
> > Hi Corey,
> >
> > thanks for contributing it. Looks good to me. I’ll run it through our
> > testing and let you know about the results.
> >
> > Best regards,
> >
> > Martin
> >
> > *From:*ppc-aix-port-dev <ppc-aix-port-dev-bounces at openjdk.java.net>
> *On
> > Behalf Of *Michihiro Horie
> > *Sent:* Freitag, 10. April 2020 10:48
> > *To:* cjashfor at linux.ibm.com
> > *Cc:* hotspot-compiler-dev at openjdk.java.net;
> > ppc-aix-port-dev at openjdk.java.net
> > *Subject:* Re: RFR[S]:8241874 [PPC64] Improve performance of
> > Long.reverseBytes() and Integer.reverseBytes() on Power9
> >
> > Hi Corey,
> >
> > Thank you for sharing your benchmarks. I confirmed your change reduced
> > the elapsed time of the benchmarks by more than 30% on my P9 node.
> Also,
> > I checked JTREG results, which look no problem.
> >
> > BTW, I cannot find further points of improvement in your change.
> >
> > Best regards,
> > Michihiro
> >
> >
> > ----- Original message -----
> > From: "Corey Ashford" <cjashfor at linux.ibm.com
> > <mailto:cjashfor at linux.ibm.com>>
> > To: Michihiro Horie/Japan/IBM at IBMJP
> > Cc: hotspot-compiler-dev at openjdk.java.net
> > <mailto:hotspot-compiler-dev at openjdk.java.net>,
> > ppc-aix-port-dev at openjdk.java.net
> > <mailto:ppc-aix-port-dev at openjdk.java.net>, "Gustavo Romero"
> > <gromero at linux.vnet.ibm.com <mailto:gromero at linux.vnet.ibm.com>>
> > Subject: Re: RFR[S]:8241874 [PPC64] Improve performance of
> > Long.reverseBytes() and Integer.reverseBytes() on Power9
> > Date: Fri, Apr 3, 2020 8:07 AM
> >
> > On 4/2/20 7:27 AM, Michihiro Horie wrote:
> >> Hi Corey,
> >>
> >> I’m not a reviewer, but I can run your benchmark in my local P9 node if
> >> you share it.
> >>
> >> Best regards,
> >> Michihiro
> >
> > The tests are somewhat hokey; I added the shifts to keep the compiler
> > from hoisting the code that it could predetermine the result.
> >
> > Here's the one for Long.reverseBytes():
> >
> > import java.lang.*;
> >
> > class ReverseLong
> > {
> >       public static void main(String args[])
> >       {
> >           long reversed, re_reversed;
> > long accum = 0;
> > long orig = 0x1122334455667788L;
> > long start = System.currentTimeMillis();
> > for (int i = 0; i < 1_000_000_000; i++) {
> > // Try to keep java from figuring out stuff in advance
> > reversed = Long.reverseBytes(orig);
> > re_reversed = Long.reverseBytes(reversed);
> > if (re_reversed != orig) {
> >           System.out.println("Orig: " + String.format("%16x", orig) +
> > "  Re-reversed: " + String.format("%16x", re_reversed));
> > }
> > accum += orig;
> > orig = Long.rotateRight(orig, 3);
> > }
> > System.out.println("Elapsed time: " +
> > Long.toString(System.currentTimeMillis() - start));
> > System.out.println("accum: " + Long.toString(accum));
> >       }
> > }
> >
> >
> > And the one for Integer.reverseBytes():
> >
> > import java.lang.*;
> >
> > class ReverseInt
> > {
> >       public static void main(String args[])
> >       {
> >           int reversed, re_reversed;
> > int orig = 0x11223344;
> > int accum = 0;
> > long start = System.currentTimeMillis();
> > for (int i = 0; i < 1_000_000_000; i++) {
> > // Try to keep java from figuring out stuff in advance
> > reversed = Integer.reverseBytes(orig);
> > re_reversed = Integer.reverseBytes(reversed);
> > if (re_reversed != orig) {
> >           System.out.println("Orig: " + String.format("%08x", orig) +
> > "  Re-reversed: " + String.format("%08x", re_reversed));
> > }
> > accum += orig;
> > orig = Integer.rotateRight(orig, 3);
> > }
> > System.out.println("Elapsed time: " +
> > Long.toString(System.currentTimeMillis() - start));
> > System.out.println("accum: " + Integer.toString(accum));
> >       }
> > }
> >