Issue 539 in webp: ARM64 NEON support for MSVC

[nth1… via monorail]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 539 by nth1...@gmail.com: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539

The existing preprocessor definitions in src/dsp/dsp.h support NEON intrinsics when compiling for ARM32 with MSVC, but not ARM64.

MSVC appears to build with ARM64 NEON support if I change the preprocessor definition at https://chromium.googlesource.com/webm/libwebp/+/refs/tags/v1.2.1/src/dsp/dsp.h#122 to the following:

#if defined(_MSC_VER) &&\
(_MSC_VER >= 1700 && defined(_M_ARM) || _MSC_VER >= 1911 && defined(_M_ARM64))

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[jz… via monorail]

Updates:
Status: Accepted

Comment #1 on issue 539 by jz...@google.com: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539#c1

Thanks for the report. At one point Visual Studio had a separate arm64_neon.h that would be needed. I haven't looked at this for some time though.

[hamdi… via monorail]

Comment #3 on issue 539 by hamdi...@gmail.com: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539#c3

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[jz… via monorail]

Updates:
Owner: jz...@google.com

Comment #4 on issue 539 by jz...@google.com: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539#c4

It seems Visual Studio 2019 started including a check in arm_neon.h [1] rather than requiring arm64_neon.h to be directly included (and failing otherwise [2]). We can start with that version.

[1] arm_neon.h VS2019
#if defined(_M_ARM64) || defined(_M_HYBRID_X86_ARM64)
#include <arm64_neon.h>
#else /* defined(_M_ARM64) || defined(_M_HYBRID_X86_ARM64)*/
...

[2] arm_neon.h VS2017
...
#if !defined (_M_ARM)
#error This header is specific to ARM targets
#endif /* !defined (_M_ARM) */

[Git Watcher via monorail]

Comment #5 on issue 539 by Git Watcher: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539#c5

The following revision refers to this bug:
https://chromium.googlesource.com/webm/libwebp/+/e23cd5481c4d90229e967bc01034fdc355e8978d

commit e23cd5481c4d90229e967bc01034fdc355e8978d
Author: James Zern <jz...@google.com>
Date: Tue Sep 14 00:44:38 2021

dsp.h: enable NEON w/VS2019+ ARM64 targets

Visual Studio added ARM64 support, but requires arm64_neon.h to be
included rather than arm_neon.h. Visual Studio 2019 addressed this so
we'll start with that version and leave a local adapter include for a
follow up.

Bug: webp:539
Change-Id: If975c029dafffba99210b3bb2d670035a83e8105

[modify] https://crrev.com/e23cd5481c4d90229e967bc01034fdc355e8978d/src/dsp/dsp.h

[jz… via monorail]

Updates:
Labels: Needs-Feedback

Comment #6 on issue 539 by jz...@google.com: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539#c6

I'm tempted to leave Visual Studio 2017 as is to reduce the code churn with an adapter include. Is Visual Studio 2019 support enough for your setup?

[nth1… via monorail]

Comment #7 on issue 539 by nth1...@gmail.com: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539#c7

> Is Visual Studio 2019 support enough for your setup?

Yes.

[jz… via monorail]

Updates:
Labels: -Needs-Feedback
Status: Fixed

Comment #8 on issue 539 by jz...@google.com: ARM64 NEON support for MSVC
https://bugs.chromium.org/p/webp/issues/detail?id=539#c8

Thanks for the update. I'll close this for now. The path for Visual Studio 2017 is documented in the code and we can revisit this if it's pressing for others.