MSVC compile error for NEON (win/arm64)

XSIMD library cannot be built using MSVC compiler on a windows/arm64 target.

Steps to reproduce

Visual Studio 2019 or higher is required for compilation.

Compilation can be done natively on a win/arm64 machine or can be cross-compiled from an x86/x64 machine.

From a command terminal

C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Auxiliary\Build\vcvarsx86_arm64.bat

cmake -G "NMake Makefiles" -D DOWNLOAD_GTEST=1 -D CMAKE_BUILD_TYPE=Debug .

nmake test_xsimd

The issue has been noticed while building the apache arrow library and would be required to build an apache arrow for win/arm64 using MSVC.

The main issue seems to be due to MSVC arm/neon intrinsic vector type using the same underlying type for the neon vectors.

e.g: int8x16_t and uint8x16_t maps to __n128 type

This causes a couple of issues

Function overloading issues as functions with same functions redefined in xsimd
Neon dispatcher doesn't pick the right function as all of the functions might be using the same underlying type.

And other issues are

reinterpret_cast doesn't work on neon vector types
intrinsic functions defined using macro which might overwrite functions with the same name even defined under a namespace (e.g: wrap::vadd_f32)
NEON identification require different flag checks
Initializer_list constructor missing for neon vector types

Few approaches I can think of

A) Replace the dispatcher to not use target vector type and use the scalar vector type to find the functions to use.
B) Define a wrapper class for msvc neon vector types so that they are distinguishable and can be used with the current dispatcher mechanism.

Pull Request for approach (A)

Any news on this issue, since nowadays ARM64 on Windows is a thing?

We should probably revive #612 , but I cannot give a deadline for now. Any help on that would be appreciated.

proved obsolete by #1248.

@serge-sans-paille

@serge-sans-paille I'm afraid this issue is not proved obsolete by the new CI job. It's about building with the MSVC compiler targeting arm64, not about building with gcc/mingw. Could you please reopen the issue?

As noted in #1248 (comment), I mistyped the label, but it's indeed msvc being run.
And this build: https://github.com/xtensor-stack/xsimd/actions/runs/21322768338/job/61375021654 makes me think everything is good?

-- The C compiler identification is MSVC 19.44.35222.0
-- The CXX compiler identification is MSVC 19.44.35222.0

...
or so I thought, but no, It's targeting amd64, my bad. Reopening

@jgiannuzzi

@jgiannuzzi https://github.com/xtensor-stack/xsimd/actions/runs/21334459960/job/61404179357?pr=1250 from #1250 looks good, right?

@serge-sans-paille

@serge-sans-paille yes that looks good to me! Thank you!

Some feedback: I cana ctually reproduce your issue in #1250, which is somehow good. I had great hope that /Zc:arm64-aliased-neon-types- would help, but that doesn't seem to be enough, unfortunately.

This issue actually got worse with #1254. Before, including "xsimd" was basicly a no-op. I was even able to use the emulated SIMD xsimd::emulated as fallback. Now it detects neon (which is correct), but so this error here breaks building the emulated fallback.

can you try something like this in the meantime? https://github.com/flatironinstitute/finufft/blob/e137ec92f1cc1e91191f50072460a80307195304/include/finufft/simd.hpp#L8
then you can check if NEON is detected and force emulated.

The project now builds successfully with MSVC on Windows on ARM, with all tests passing. Additionally, a CI script has been added to support builds using LLVM Clang and MSYS2 CLANGARM64. Refer below PR
#1285

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MSVC compile error for NEON (win/arm64) #611

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MSVC compile error for NEON (win/arm64) #611

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niyas-sait commented on Oct 19, 2021

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