libyuv needs dotprod on aarch64

[catap]

See: https://chromium.googlesource.com/libyuv/libyuv/+/refs/heads/main/CMakeLists.txt#115

[ilya-fedin]

Did you test it with all of: GCC, AppleClang and MSVC? This is being used by 3 compilers.

[catap]

It was discovered by bulk-build in OpenBSD, and this patch is already used in OpenBSD ports: openbsd/ports@b9f167d

Thus, it is reused the same march which is used by upstream of libyuv.

[ilya-fedin]

This doesn't really answer my question. Are you sure your change won't break other compilers/platforms I mentioned?

[catap]

I have no idea, nor I had tested it.

Anyway, upstream seems to use it for all arm64/aarch64 builds and this is required minimal march to compile compare_neon64.cc which uses udot instruction.

[ilya-fedin]

No? I see it's under NOT MSVC upstream. And Google generally seem to not to use AppleClang for their builds? So the build system could not account for it. This needs testing.

[catap]

Just to let you know. Without this march it fails as:

.../src/third_party/libyuv/source/compare_neon64.cc:175:8: error: instruction requires: dotprod
      "udot        v4.4s, v0.16b, v6.16b         \n"
       ^
<inline asm>:14:1: note: instantiated into assembly here
udot        v4.4s, v0.16b, v6.16b         
^

[ilya-fedin]

With this march it will likely fail with unknown argument error on various compilers. On MSVC for sure.