RFR: JDK-8213199: GC abstraction for Assembler::needs_explicit_null_check()

Roman Kennke rkennke at redhat.com
Thu Nov 1 16:58:24 UTC 2018

Hi Erik,

> Would you mind explaining how you need to override this and why? I'm
> afraid I did not quite get it from your description in the RFC (which is
> also why I didn't come up with a solution either).
> Am I correct that you need to return false if the passed in offset is
> the cell header offset -8, or is there anything else at all required to
> that logic?

No, it's really just that. Plus take care of it in the case of combined
narrow-oops-offset plus -8.

> You mentioned something about the high order byte being
> masked on AArch64, but didn't quite connect the dot to how that is
> related to this code. Is it?

Yes, we also need to mask the high order byte in AArch64 because of the
way addressing works on that platform, and because -8 flips on those
negative bits.

Also, the mach5 job came back with FAILED (see below). Can somebody with
access check and see what's up?


Build Details: 2018-11-01-1146402.roman.source
0 Failed Tests
Mach5 Tasks Results Summary

    KILLED: 0
    PASSED: 48
    FAILED: 0
    NA: 0

        6 Executed with failure
            solaris-sparcv9-solaris-sparcv9-build-8 error while
building, return value: 2
            solaris-sparcv9-debug-solaris-sparcv9-build-9 error while
building, return value: 2
            windows-x64-windows-x64-build-10 error while building,
return value: 2
            windows-x64-debug-windows-x64-build-11 error while building,
return value: 2
            windows-x64-open-windows-x64-build-12 error while building,
return value: 2
            windows-x64-open-debug-windows-x64-build-13 error while
building, return value: 2
        2 Not run
            solaris-sparcv9-install-solaris-sparcv9-build-16 Dependency
task failed: mach5...-8300-solaris-sparcv9-solaris-sparcv9-build-8
            windows-x64-install-windows-x64-build-17 Dependency task
failed: YJftjiBUYc


        19 Not run

Dependency task failed:

Dependency task failed:

Dependency task failed: YJftjiBUYc

Dependency task failed: YJftjiBVYc

tier1-debug-open_test_hotspot_jtreg_tier1_compiler_1-windows-x64-debug-29 Dependency
task failed: YJftjiBVYc

tier1-debug-open_test_hotspot_jtreg_tier1_compiler_2-windows-x64-debug-32 Dependency
task failed: YJftjiBVYc

tier1-debug-open_test_hotspot_jtreg_tier1_compiler_3-windows-x64-debug-35 Dependency
task failed: YJftjiBVYc

Dependency task failed: YJftjiBVYc

Dependency task failed: YJftjiBVYc

Dependency task failed: YJftjiBVYc
            See all 19...

> Thanks,
> /Erik
> On 2018-11-01 12:20, Roman Kennke wrote:
>> Hi Kim, thanks for reviewing! I'll push it through jdk/submit now.
>> Erik: ok for you too?
>> Thanks,
>> Roman
>>>> On Oct 31, 2018, at 6:14 PM, Roman Kennke <rkennke at redhat.com> wrote:
>>>> Hi Erik,
>>>> right. Fixed this, and what what Kim mentioned plus a missing include:
>>>> Incremental:
>>>> http://cr.openjdk.java.net/~rkennke/JDK-8213199/webrev.01.diff/
>>>> Full:
>>>> http://cr.openjdk.java.net/~rkennke/JDK-8213199/webrev.01/
>>>> Ok now?
>>> Looks good.

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