OpenJDK extension to AArch64 and Windows

Ludovic Henry luhenry at
Wed Jun 24 21:33:53 UTC 2020

Hi Magnus,

Happy to answer any question you have on the build system changes.

A lot of the changes were due to the build system not supporting cross-compilation well when targetting the microsoft toolchain (it just never really had to support it). We had to go through a few hoops to remove as many of our own quick hacks, initially there just to get things building - like hardcoding the target being windows-aarch64 for example.

Thank you for your review,


From: Magnus Ihse Bursie <magnus.ihse.bursie at>
Sent: Wednesday, June 24, 2020 13:44
To: Monica Beckwith; hotspot-runtime-dev at; aarch64-port-dev at; build-dev
Cc: openjdk-aarch64
Subject: Re: OpenJDK extension to AArch64 and Windows

Hi Monica,

All build system changes must be sent to build-dev for review by the
build team, and you are doing quite a lot of build changes. (I'm cc:ing
build-dev now.)

I did a quick scan and found some changes that looked odd enough to draw
my attention.

I will need some time to fully understand what you are trying to
accomplish here, before I can give a full review.


On 2020-06-24 18:40, Monica Beckwith wrote:
> Hello OpenJDK community,
> As the project lead here @Microsoft, I am pleased to share that we have been working towards a Windows addition to the OpenJDK AArch64 port. We are very thankful to all that have contributed to the Linux+aarch64 and Windows+x86-64. Both these codebases came to our rescue on numerous occasions.
> Support status: We have successfully ported C2 and can build the server release (cross-compiled environment)
> Test coverage: C2 + ParallelGC (No AOT, JVMCI, ZGC, ShenandoahGC, G1GC)
> Tests and benchmarks covered [1]: JTReg [2], JCStress, jmh-jdk-microbenchmarks, SPEC SERT, SPECJBB2015 [3], SPEC JVM2008, Scimark2, SPEC JBB2005.
> Umbrella Bug ID:
> Webrevs:
> `Webrev P1`:  &
> `Webrev P2`:
> The first patch `Webrev P1` (patch 1 aka P1 in our tests) helps integrate support for Windows (LLP64) on Linux + AArch64
> The second patch `Webrev P2` (patch 2 aka P2 in our tests) adds the 'windows-aarch64' support in `os_cpu`. We also had to modify shared code, and I am highlighting a few details here:
>       * In windows_x86 such as the `get_frame_at_stack_banging_point` in `os_windows_x86.cpp`,
>       * In `os/windows os_windows.cpp` to make it aware of Windows + Arm64
>       * `os/windows` in `threadCritical_windows.cpp`,
>       * Windbg support
>       * `globalDefinitions_visCPP.hpp` in `share/utilities`
>       * We also added Vectored Exception Handling (VEH) to P2, as it is a requirement on Windows + Arm64 (due to ABI specifications).
> Also, in `Webrev P2`, you will find that we have made some significant changes to `cpu/aarch64` around register usage since on Windows + Arm64, register R18 points to TEB [4]. We have discussed this with Andrew Haley and Andrew Dinn, and they are helping us with a cleaner implementation of the same. Their constant support and guidance have humbled me.
> I'd also like to recognize the great work done by Ludovic Henry (our resident runtime expert) in driving the C2 support and by Bernhard Urban-Forster, (who recently joined our team) in helping expand the coverage to G1 GC.
> As a part of this project, we have also worked on two additional patches:
>       * Expanding VEH on Windows to x86-64 (patch 3 aka P3 in our tests). Details here:
>       * Improvements in the shared cross-platform code on Windows (patch 4 aka P4 in our tests) - We will send out a separate patch soon.
> We welcome any feedback and comments from the community and are looking forward to working together.
> Regards,
> Monica
> [1]
> [2]
> [3]
> [4]

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