llvm dev - May 2018 - Showcase of the Windows/ARM64/MinGW target

Hi,

At the Build conference recently, Microsoft had a session about Windows on 
ARM(64), [1]. As case example of a large, nontrivial app rebuilt for this 
arch, they demonstrated VLC.

The presentation claimed that this was built with MSVC, with zero changes 
to the source.

This actually isn't true; the app that was demonstrated was actually built 
with Clang and LLD with mingw-w64 as SDK (and there had been quite a few 
minor fixes throughout the codebase to make it all build both with 
clang/libc++ for windows, and for windows on non x86 targets).

Despite the pretty drastic miscommunication, I think it was nice to have 
at least the output from these tools demonstrated. (The presenter was 
reminded about how it actually was built after the presentation; 
apparently this information had been lost somewhere along the chain.)

And as a fun fact, it can be mentioned that a large amout of the 
windows/arm64 support in LLVM/LLD was developed before I even had access 
to this OS for testing, or even MSVC for reference - most of it was 
developed and tested just with wine (bootstrapped from a handful of 
reference windows/arm64 binaries).

Thanks to everybody who have helped make this happen!

// Martin

[1] https://www.youtube.com/watch?v=vdYIaUeZnqc

So are you saying that LLVM can be built as ARM64 on Windows now?
CMake doesn't show me an option for ARM64 when using MSVC on Windows.
I have the latest CMake.

On Mon, May 21, 2018 at 2:34 AM, Martin Storsjö via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> At the Build conference recently, Microsoft had a session about Windows on
> ARM(64), [1]. As case example of a large, nontrivial app rebuilt for this
> arch, they demonstrated VLC.
>
> The presentation claimed that this was built with MSVC, with zero changes
to
> the source.
>
> This actually isn't true; the app that was demonstrated was actually
built
> with Clang and LLD with mingw-w64 as SDK (and there had been quite a few
> minor fixes throughout the codebase to make it all build both with
> clang/libc++ for windows, and for windows on non x86 targets).
>
> Despite the pretty drastic miscommunication, I think it was nice to have at
> least the output from these tools demonstrated. (The presenter was reminded
> about how it actually was built after the presentation; apparently this
> information had been lost somewhere along the chain.)
>
> And as a fun fact, it can be mentioned that a large amout of the
> windows/arm64 support in LLVM/LLD was developed before I even had access to
> this OS for testing, or even MSVC for reference - most of it was developed
> and tested just with wine (bootstrapped from a handful of reference
> windows/arm64 binaries).
>
> Thanks to everybody who have helped make this happen!
>
> // Martin
>
> [1] https://www.youtube.com/watch?v=vdYIaUeZnqc
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

On Mon, 21 May 2018, Hayden Livingston wrote:
> So are you saying that LLVM can be built as ARM64 on Windows now?
> CMake doesn't show me an option for ARM64 when using MSVC on Windows.
> I have the latest CMake.
I'm saying that LLVM can produce code for the Windows/ARM64 target.

As for compiling LLVM itself to run on ARM64 on Windows, I don't know how 
to configure MSVC to do that; MSVC doesn't install the ARM64 compiler by 
default but you manually need to check a box in the installer (available 
since 15.4, and more intended for actual public use since the 15.8 
preview). No idea how you configure that in CMake.

You can build LLVM+Clang for ARM64 with Clang/mingw-w64/libcxx though, 
with the same toolchain used to build VLC in that demo.

// Martin