BitOperations arm64 intrinsic for LeadingZeroCount, TrailingZeroCount and Log2

[kunalspathak]

Use arm64 intrinsics for BitOperations's LeadingZeroCount, TrailingZeroCount and Log2 methods.

Below are the performance improvement details of each API.

API	before (in us)	after (in us)	% diff
LeadingZeroCount_uint	6.538	1.544	76%
LeadingZeroCount_ulong	6.614	1.544	77%
Log2_uint	5.774	1.920	67%
Log2_ulong	6.925	1.921	72%
TrailingZeroCount_uint	2.722	1.665	39%
TrailingZeroCount_ulong	2.891	1.666	42%

I didn't include PopCount() as part of this PR because it needs special handling of CreateScalar in JIT. Once #34485 is fixed, I will send a separate PR for it PopCount().

Contributes to #33308 and #33495 .

[Dotnet-GitSync-Bot]

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[kunalspathak]

Please take a look @dotnet/jit-contrib , @tannergooding

[BruceForstall]

The Log2_uint improvement % number looks incorrect.

For these arm64-specific libraries changes, I think you need to trigger the runtime AzDO pipeline manually, as the default PR testing does not include libraries arm64 testing.

[kunalspathak]

@BruceForstall - Triggered one just now at https://dev.azure.com/dnceng/public/_build/results?buildId=587055&view=results
I do see jobs "Libraries Test Run release coreclr Linux arm64 Release" in it. So hopefully that is the one we wanted.

[kunalspathak]

I was seeing ARM not present in System.Runtime.Intrinsics namespace errors. Not sure if this was because I didn't had #34107.

I have rebased my changes and triggered another pipeline run.
https://dev.azure.com/dnceng/public/_build/results?buildId=587081&view=results

[kunalspathak]

Jobs are failing with following errors. Do i need to add a package reference or something inside System.Utf8String.Experimental.csproj. How is it suppose to work?

F:\workspace\_work\1\s\src\libraries\System.Private.CoreLib\src\System\Numerics\BitOperations.cs(8,33): error CS0234: The type or namespace name 'Arm' does not exist in the namespace 'System.Runtime.Intrinsics' (are you missing an assembly reference?) [F:\workspace\_work\1\s\src\libraries\System.Utf8String.Experimental\src\System.Utf8String.Experimental.csproj]
##[error]src\libraries\System.Private.CoreLib\src\System\Numerics\BitOperations.cs(8,33): error CS0234: The type or namespace name 'Arm' does not exist in the namespace 'System.Runtime.Intrinsics' (are you missing an assembly reference?)

@tannergooding , @echesakovMSFT

[EgorBo]

What about BitOperations.RotateLeft does jit lower GT_ROR to arm's ror ?

[kunalspathak]

What about BitOperations.RotateLeft does jit lower GT_ROR to arm's ror ?

Yes. It converts RotateRight to ror and RotateLeft to neg/ror because there is no rol instruction in arm.

[echesakov]

Looks good with comments regarding redundant casts to int

[echesakov]

Jobs are failing with following errors. Do i need to add a package reference or something inside System.Utf8String.Experimental.csproj. How is it suppose to work?
F:\workspace_work\1\s\src\libraries\System.Private.CoreLib\src\System\Numerics\BitOperations.cs(8,33): error CS0234: The type or namespace name 'Arm' does not exist in the namespace 'System.Runtime.Intrinsics' (are you missing an assembly reference?) [F:\workspace_work\1\s\src\libraries\System.Utf8String.Experimental\src\System.Utf8String.Experimental.csproj]
##[error]src\libraries\System.Private.CoreLib\src\System\Numerics\BitOperations.cs(8,33): error CS0234: The type or namespace name 'Arm' does not exist in the namespace 'System.Runtime.Intrinsics' (are you missing an assembly reference?)

@kunalspathak My understanding that you need to update Intrinsics.Shims.cs simiralrly as it's been done for System.Runtime.Intrinsics.X86 in order for this to work - @tannergooding is it right?

[tannergooding]

Jobs are failing with following errors. Do i need to add a package reference or something inside System.Utf8String.Experimental.csproj. How is it suppose to work?
My understanding that you need to update Intrinsics.Shims.cs simiralrly as it's been done for System.Runtime.Intrinsics.X86 in order for this to work - @tannergooding is it right?

I believe that is the case, but CC. @GrabYourPitchforks since I think he "owns" System.Utf8String.Experimental.
Just as a note, we don't want to do this more broadly as we don't want to have a reference to the experiemental package from non-experimental packages.
If there is anything non-experimental that isn't in S.P.Corelib that would require a similar change, we may need to wait for the bits to be moved in box (which should be happening once API review on everything finishes).

[kunalspathak]

Jobs are failing with following errors. Do i need to add a package reference or something inside System.Utf8String.Experimental.csproj. How is it suppose to work?
F:\workspace_work\1\s\src\libraries\System.Private.CoreLib\src\System\Numerics\BitOperations.cs(8,33): error CS0234: The type or namespace name 'Arm' does not exist in the namespace 'System.Runtime.Intrinsics' (are you missing an assembly reference?) [F:\workspace_work\1\s\src\libraries\System.Utf8String.Experimental\src\System.Utf8String.Experimental.csproj]
##[error]src\libraries\System.Private.CoreLib\src\System\Numerics\BitOperations.cs(8,33): error CS0234: The type or namespace name 'Arm' does not exist in the namespace 'System.Runtime.Intrinsics' (are you missing an assembly reference?)

@kunalspathak My understanding that you need to update Intrinsics.Shims.cs simiralrly as it's been done for System.Runtime.Intrinsics.X86 in order for this to work - @tannergooding is it right?

That seemed to have solved the problem (atleast on my local machine). Thanks!

[kunalspathak]

The Log2_uint improvement % number looks incorrect.

@BruceForstall - This measurements were taken on ARM64 machine manually for MicroBenchmarks. Changes are here: dotnet/performance#1264

[kunalspathak]

Failures related to #34465
//cc @jaredpar

[BruceForstall]

@BruceForstall - This measurements were taken on ARM64 machine manually for MicroBenchmarks.

given this:

API	before (in us)	after (in us)	% diff
Log2_uint	5.774	1.920	15%
Log2_ulong	6.925	1.921	72%

It seems like Log2_unit should be 67% improvement, not 15%.

[kunalspathak]

It seems like Log2_unit should be 67% improvement, not 15%.

Ah yes.