[jdk11u-dev] RFR: 8248238: Implementation: JEP 388: Windows AArch64 Support [v3]

[Vladimir Kempik]

On Tue, 31 Aug 2021 13:18:50 GMT, Reka Kovacs <github.com+25946952+rnkovacs at openjdk.org> wrote:

>> Main commit of the Windows/AArch64 port.
>> 
>> Also fixes [JDK-8272181](https://bugs.openjdk.java.net/browse/JDK-8272181) by adding [`src/hotspot/os_cpu/windows_aarch64/pauth_windows_aarch64.inline.hpp`](https://github.com/openjdk/jdk11u-dev/pull/301/files#diff-235302dc4618158c4f75771ebbb6f0e4beeee5daf0a537b03ee4253a711268c6), which is needed for a successful Windows-AArch64 build.
>> 
>> Depends on #274 and #299.
>
> Reka Kovacs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains one additional commit since the last revision:
> 
>   Backport 9604ee82690f89320614b37bfef4178abc869777

One question, about R18 exclusion part.
In the light of recent issues with r18 being finally used by OS for its own needs ( since macos12b6), I have made some tests.  ( more about issues here https://youtrack.jetbrains.com/issue/JBR-3715)
I took part of this PR which belongs to R18 usage elimination and applied it to zulu11 ( reverting older version of patch first which wasn't working with C2 compiled code)
This fixed zulu11 under macos12b6 and I was happy about that.
However I have noticed one strange thing
I did this:
bin/java -XX:+UnlockDiagnosticVMOptions -XX:+PrintAssembly -jar demo/jfc/J2Ddemo/J2Ddemo.jar > output.log
then this:
cat output.log | grep x18 | grep -v 0x18
and found some usage of x18:
0x000000010bcafc80: stp	x18, x19, [sp, #144]
 0x000000010bcb0b60: stp	x18, x19, [sp, #144]
 0x000000010bcb1590: stp	x18, x19, [sp, #144]
 0x000000010bcb2470: stp	x18, x19, [sp, #144]
 0x000000010bcb3dd0: stp	x18, x19, [sp, #144]
 0x000000010bcb4cd0: stp	x18, x19, [sp, #144]
 0x000000010bcb5ae0: stp	x18, x19, [sp, #144]

it's just reading of x18, not writing, however it might indicate something is still missing there.
this doesn't happen on jdk17ea (on 17ea there is a different strange thing with x18)

Could you try to replicate this result with win-arm64  build  of jdk11 ( make sure to put hsdis in there)

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PR: https://git.openjdk.java.net/jdk11u-dev/pull/301