BitOperations arm64 intrinsic for LeadingZeroCount, TrailingZeroCount and Log2 by kunalspathak · Pull Request #34486 · dotnet/runtime

kunalspathak · 2020-04-03T02:17:27Z

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 · 2020-04-03T02:17:37Z

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kunalspathak · 2020-04-03T02:18:00Z

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

BruceForstall · 2020-04-03T04:54:53Z

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 · 2020-04-03T05:31:37Z

@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 · 2020-04-03T06:06:36Z

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 · 2020-04-03T07:01:36Z

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 · 2020-04-03T07:28:03Z

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

kunalspathak · 2020-04-03T08:05:39Z

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 · 2020-04-03T18:37:55Z

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 · 2020-04-03T18:48:00Z

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 · 2020-04-03T18:59:29Z

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 · 2020-04-03T19:01:14Z

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 · 2020-04-04T00:26:22Z

Failures related to #34465
//cc @jaredpar

BruceForstall · 2020-04-04T01:47:36Z

@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 · 2020-04-06T08:21:23Z

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

Ah yes.

kunalspathak added the arch-arm64 label Apr 3, 2020

tannergooding approved these changes Apr 3, 2020

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BruceForstall added the area-System.Numerics label Apr 3, 2020

BruceForstall approved these changes Apr 3, 2020

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kunalspathak added 3 commits April 2, 2020 22:57

ARM64 intrinsic for LeadingZeroCount

cc04050

ARM64 intrinsic for Log2

90be48c

ARM64 intrinsic for TrailingZeroCount

a2effc7

kunalspathak force-pushed the bitoperations-intrinsic branch from b628d47 to a2effc7 Compare April 3, 2020 05:58

echesakov approved these changes Apr 3, 2020

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kunalspathak added 2 commits April 3, 2020 11:57

Remove redundant cast

cdf34f9

Add entry of System.Runtime.Intrinsic.Arm in shim

80ff885

kunalspathak merged commit 510efdf into dotnet:master Apr 4, 2020

kunalspathak deleted the bitoperations-intrinsic branch April 4, 2020 00:27

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