GH-49921: [C++] Bump xsimd to 14.2.0

[AntoinePrv]

Rationale for this change

• Fix for the current SVE ODR violation in the latest version
  Fix SVE dynamic dispatch ODR violation xtensor-stack/xsimd#1311
• Pre-requisit to [C++] Use existing library for CPU detection #45331

What changes are included in this PR?

Bump version and cleanup backports.

Are these changes tested?

Yes, in CI.

Are there any user-facing changes?

No

• GitHub Issue: [C++] Bump xsimd to 14.2.0 #49921

[github-actions]

⚠️ GitHub issue #49921 has been automatically assigned in GitHub to PR creator.

[pitrou]

@AntoinePrv Can you take a look at the CI failures? They seem related.

[AntoinePrv]

Yes, I am still waiting for the Msys2 build of xsimd to happen...

[pitrou]

There are failures on non-MSys2 builds, though:

• https://github.com/apache/arrow/actions/runs/25421952127/job/74565986944?pr=49922
• https://github.com/apache/arrow/actions/runs/25421952024/job/74565986771?pr=49922

[AntoinePrv]

Perhaps it's this check that does not work on MSVC?

https://github.com/xtensor-stack/xsimd/blob/80c23624ce008d937da7e845e528e82ce0cbf4e0/include/xsimd/types/xsimd_batch_constant.hpp#L500

Either we could add /Zc:__cplusplus or re-introduce the backport.

[pitrou]

I think we should both 1) fix xsimd upstream anyway and 2) pass /Zc:__cplusplus when building Arrow C++.

It seems xsimd should do something like this:

#ifdef _MSVC_LANG
#define XSIMD_CPP_LEVEL _MSVC_LANG
#else
#define XSIMD_CPP_LEVEL __cplusplus
#endif

and then use the XSIMD_CPP_LEVEL macro everywhere instead of __cplusplus.

(but xsimd could also use find-grained feature testing).

[AntoinePrv]

Already sending a patch, but not sure I want to go through another round of xsimd releases

xtensor-stack/xsimd#1342

[pitrou]

Agreed, hence "pass /Zc:__cplusplus when building Arrow C++" as well 😉