Port GrayscalConverter to Arm

[stefannikolei]

Port Grayscaleconverter to ARM

Benchmarks:

| Method | Mean | Error | StdDev | Ratio | RatioSD ||-------------- |----------:|---------:|---------:|------:|--------:|| Scalar | 118.76 ns | 0.499 ns | 0.443 ns | 1.00 | 0.00 || SimdVectorAvx | NA | NA | NA | ? | ? || SimdVectorArm | 53.57 ns | 0.410 ns | 0.364 ns | 0.45 | 0.00 |

[JimBobSquarePants]

Great speed up! All these additions are going to be a gamechanger for ARM

[JimBobSquarePants]

Looks like something in #2401 has changed the result of some of the WebP output on ARM.

[brianpopow]

Looks like something in #2401 has changed the result of some of the WebP output on ARM.

Just stating the obvious: It seems impossible to me, that the changes from this PR could be responsible for WebP test failures.
@stefannikolei If you run the webp tests on you machine, do you see any test failing?
You can run only Webp tests with: dotnet test -c Release -f net6.0 --filter "Format=Webp"

[stefannikolei]

 WebpDecoderTests
WebpDecoder_CanDecode_Lossless_WithThreeTransforms
WebpDecoder_CanDecode_Lossless_WithThreeTransforms<Rgba32>(provider: Webp/bike_lossless.webp[Rgba32])
WebpDecoder_CanDecode_Lossless_WithThreeTransforms<Rgba32>(provider: Webp/color_cache_bits_11.webp[Rgba32])
WebpDecoder_Decode_Resize
WebpDecoder_Decode_Resize<Rgba32>(provider: Webp/bike_lossless.webp[Rgba32])

Yeah this tests fail

[JimBobSquarePants]

Looks like something in #2401 has changed the result of some of the WebP output on ARM.

Just stating the obvious: It seems impossible to me, that the changes from this PR could be responsible for WebP test failures. @stefannikolei If you run the webp tests on you machine, do you see any test failing? You can run only Webp tests with: dotnet test -c Release -f net6.0 --filter "Format=Webp"

@brianpopow#2401 is the low hanging fruit PR. WebP is touched there. I'm doing another code review as we didn't label the PR to catch ARM issues.

[gfoidl]

I also have a look at this right now.

[gfoidl]

Just a FYI for easier location of error on x86-dev-machine: run the tests with DOTNET_EnableSSE=0 dotnet test -c Release -f net6.0 --filter "Format=Webp"

-- or --

Update the .runsettings to

<?xml version="1.0" encoding="utf-8" ?>
<RunSettings>
<RunConfiguration>
<!--Used in conjunction with ActiveIssueAttribute to skip tests with known issues-->
<TestCaseFilter>category!=failing</TestCaseFilter>
<EnvironmentVariables>
<DOTNET_EnableSSE>0</DOTNET_EnableSSE>
</EnvironmentVariables>
</RunConfiguration>
</RunSettings>

[gfoidl]

Hm, so far I can't spot the bug.

State so far:

• AVX --> ✔️
• ARM --> 🐛
• SSE disabled --> scalar --> 🐛

So I assume the bug isn't specific to ARM, rather it's anywhere in the scalar-path (that is hit by ARM too, but not with SSE/AVX).
Will search and debug further to smash the bug down....

[gfoidl]

I found something, will send a PR in a moment (just checking if a similar bug doesn't exist elsewhere).

Edit: PR --> #2413

[JimBobSquarePants]

OK. Let's get this merged as the changes are covered. Thanks