ComputeCrc32, ComputeCrc32C

[echesakov]

https://github.com/dotnet/corefx/issues/26220

cc @dotnet/jit-contrib @TamarChristinaArm

[echesakov]

There is an issue with the name of ISA class being the same as one of the methods.
This should be address on the next API review meeting

[TamarChristinaArm]

Looks good to me, the name clash is an interesting one. One way could be to name the class Crc instead. It would differ from what the kernel and the architecture feature bit is called but would match with the extension flag clang and gcc name it (+crc.)

[TamarChristinaArm]

Just so I know I'm understanding this correctly, after splitting the Crc32 from ArmBase, don't you need to change lookupInstructionSet to have the new Crc32 class return InstructionSet_Crc32? That seems what compSetProcessor seems to be setting when crc is available.

And also change Arm64VersionOfIsa to return a new InstructionSet_Crc32_Base64 for the A64 only parts?

[tannergooding]

don't you need to change lookupInstructionSet

Due to the repo split between CoreFX and CoreCLR, the API exposure and the JIT handling needs to be in separate PRs (as we typically don't want to add code to the JIT that can't be tested at the same time).

[tannergooding]

One way could be to name the class Crc instead.

We'll be able to discuss this more fully in API review; but I'm not convinced renaming the class differently from the ISA is the correct thing to do. We don't want to risk having clashing names in the future.

I would likely prefer keeping the class name "correct" and then modifying the method name instead. We could likely call it ComputeCrc32 or maybe something like Crc32Step (given that this just performs a single Crc32 iteration).

[echesakov]

Just so I know I'm understanding this correctly, after splitting the Crc32 from ArmBase, don't you need to change lookupInstructionSet to have the new Crc32 class return InstructionSet_Crc32? That seems what compSetProcessor seems to be setting when crc is available.
And also change Arm64VersionOfIsa to return a new InstructionSet_Crc32_Base64 for the A64 only parts?

@TamarChristinaArm As Tanner pointed this will be part of my another PR in coreclr after the change propagates to corefx and back.