[8u] RFR(XXS): 8165231: java.nio.Bits.unaligned() doesn't return true on ppc

[Volker Simonis]

Hi Alan, Sean,

can we please get a review for this rather trivial change?

> jira: https://bugs.openjdk.java.net/browse/JDK-8165231
> webrev: http://cr.openjdk.java.net/~gromero/8165231/

As outlined in Hiroshi's initial mail, we can not simply downport the
solution used in jdk9 for querying the unaligned access support in nio
because of differences in Unsafe. So this is a jsk8u-only change. But
I think it is simple enough and doesn't affect any other platform
except ppc to justify it.

As nobody from the ppc porting team is jdk8u reviewer, I kindly ask
you for a review and the permission to integrate into jdk8u.

Thanks a lot and best regards,
Volker


On Thu, Sep 1, 2016 at 5:06 PM, Doerr, Martin <martin.doerr at sap.com> wrote:
> Hi Hiroshi,
>
>
>
> thanks for providing a fix.
>
>
>
> The fix
>
> 8158260: PPC64: unaligned Unsafe.getInt can lead to the generation of
> illegal instructions
>
> was downported to 8, so I think your change is good.
>
>
>
> Best regards,
>
> Martin
>
>
>
>
>
> From: Hiroshi H Horii [mailto:HORII at jp.ibm.com]
> Sent: Donnerstag, 1. September 2016 16:27
> To: jdk8u-dev at openjdk.java.net; ppc-aix-port-dev at openjdk.java.net
> Cc: Gustavo Bueno Romero <gromero at br.ibm.com>; Volker Simonis
> (volker.simonis at gmail.com) <volker.simonis at gmail.com>; Doerr, Martin
> <martin.doerr at sap.com>
> Subject: RFR(m): java.nio.Bits.unaligned() doesn't return true on ppc
>
>
>
> Dear all:
>
> Can I please request reviews for the following change?
> This change was created for JDK 8.
>
> Some open sources (such as Spark 2.0) check java.nio.Bits.unaligned()
> to recognize support of unaligned memory access in platform.
> Though ppc64 and ppc64le support it, unaligned() returns false.
>
> In JDK 9, this method returns unalignedAccess() of jdk.internal.misc.Unsafe
> that doesn't exist in JDK8.
>
> jira: https://bugs.openjdk.java.net/browse/JDK-8165231
> webrev: http://cr.openjdk.java.net/~gromero/8165231/
> (Due to my login issue to the cs.openjdk.java.net, Gustavo thankfully
> created this webrev.)
>
> Regards,
> Hiroshi
> -----------------------
> Hiroshi Horii, Ph.D.
> IBM Research - Tokyo