RFR (M): 8036767 PPC64: Support for little endian execution model

[Andrew Hughes]

snip...

> >
> > We're now seeing problems with Java tools on ppc64le as a result of this
> > decision not to give it a distinct arch name.
> >
> > The os.arch property on both ppc64be and ppc64le builds of OpenJDK is being
> > reported as the same; "ppc64". This leaves Java applications no way of
> > determining which of the two platforms the JDK is running on and, for
> > example,
> > means that Maven can't determine which native JNI binaries to download.
> >
> > There is a sun.cpu.endian property but this is non-standard and it seems
> > wrong to me that every Java tool should have to add a special case for
> > ppc64le using such a property. This value is traditionally not so much
> > just the architecture as a composite of the architecture, the bit size
> > and the endianness. The only difference with other platforms is that they
> > only support one default endianness so the value is implied e.g.
> > little-endian for amd64, big-endian for sparc. We do distinguish between
> > ppc and ppc64 rather than expecting tools to check sun.arch.data.model,
> > so we should do the same with endianness.
> >
> > To add to the confusion, other JDKs are reporting it as ppc64le
> > (thanks to Tiago Sturmer Daitx for these results):
> >
> > IBM Java 2.7 SR1
> > os.arch: ppc64le
> > sun.cpu.endian: little
> >
> > GCJ 4.8.2 (gij (GNU libgcj) version 4.8.2):
> > os.arch: ppc64le
> > sun.cpu.endian: null
> >
> > whereas OpenJDK gives:
> >
> > os.arch: ppc64
> > sun.cpu.endian: little
> >
> > It also means that ppc64le is alone in not having a unique architecture
> > directory in jre/lib. I understand that a ppc64le machine is not going
> > to support ppc64be, but likewise amd64 is not going to support arm,
> > yet they have unique arch directories.
> >
> > I've prepared a webrev which fixes the external facing architecture names,
> > LIBARCH and os.name, while leaving the HotSpot build architecture,
> > BUILDARCH,
> > as it is, to avoid the duplication mentioned as a problem in the original
> > review.
> >
> > http://cr.openjdk.java.net/~andrew/rh1191652/webrev.01/
> >
> > This is against our IcedTea OpenJDK7-based HotSpot where we've been testing
> > but it should still be applicable to the 9 HotSpot repositories. The JDK
> > side
> > is another issue and I suspect we'll need a completely different patch
> > there
> > to the one we have for 7.
> >
> > Our builds of OpenJDK 7 with this fixed now give:
> >
> > java.library.path =
> > /usr/java/packages/lib/ppc64le:/usr/lib64:/lib64:/lib:/usr/lib
> > sun.boot.library.path =
> > /builddir/build/BUILD/java-1.7.0-openjdk-1.7.0.75-2.5.4.5.ael7b.ppc64le/openjdk/build/linux-ppc64le/j2sdk-image/jre/lib/ppc64le
> > os.arch = ppc64le
> >
> > I've filed a bug for this here:
> >
> > https://bugs.openjdk.java.net/browse/JDK-8073139
> >
> > Thanks,
> > --
> > Andrew :)
> >
> > Free Java Software Engineer
> > Red Hat, Inc. (http://www.redhat.com)
> >
> > PGP Key: ed25519/35964222 (hkp://keys.gnupg.net)
> > Fingerprint = 5132 579D D154 0ED2 3E04  C5A0 CFDA 0F9B 3596 4222
> >
> > PGP Key: rsa4096/248BDC07 (hkp://keys.gnupg.net)
> > Fingerprint = EC5A 1F5E C0AD 1D15 8F1F  8F91 3B96 A578 248B DC07
> >
> 
> Hi Andrew,
> 
> I don't have a problem with your change and it doesn't affect the
> ppc64 big endian build.
> 
> I've prepared a patch which applies cleanly to jdk9-hs-rt here:
> 
> http://cr.openjdk.java.net/~simonis/webrevs/2015/8073139/
> 

Thanks. I see OpenJDK 9 still doesn't have aarch64; that seems to be
the only difference.

> Let's here some other opinions as well (you'll need a sponsor from
> Oracle anyway and it would also be interesting to here from Alexander
> if they already rely on os.arch being ppc64) but from my side thumbs
> up.

Thanks. I thought arch-specific changes were now able to go through
without Oracle sponsorship? Anyway, if David is willing to shepherd
it through, it's not a problem.

> 
> Regards,
> Volker
> 

-- 
Andrew :)

Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

PGP Key: ed25519/35964222 (hkp://keys.gnupg.net)
Fingerprint = 5132 579D D154 0ED2 3E04  C5A0 CFDA 0F9B 3596 4222

PGP Key: rsa4096/248BDC07 (hkp://keys.gnupg.net)
Fingerprint = EC5A 1F5E C0AD 1D15 8F1F  8F91 3B96 A578 248B DC07