JIT: Use ValueTuple argument for SIMD type lookup for AdvSimd.Store*

[amanasifkhalid]

Follow-up to #106765. Store and StoreVectorAndZip, like StoreSelectedScalar, have variants that operate on ValueTuples of Vectors, and in the case of the former intrinsic, the SIMD size has to be determined at runtime since it can operate on 64- and 128-bit Vectors. Thus, the JIT needs to determine the Vector size used by the intrinsic overloads' ValueTuple argument.

There are a few other intrinsics (like LoadAndInsertScalar) that also operate on ValueTuples, and the JIT currently differentiates between these variants with dedicated NamedIntrinsics (LoadAndInsertScalarVector64x2, LoadAndInsertScalarVector64x3, etc). I think these can be unified into one NamedIntrinsic and use the ValueTuple lookup logic, in case we want to clean these up.

[amanasifkhalid]

@tannergooding I did a quick parse of the intrinsics that take ValueTuples, and none of them need to look up their SIMD sizes at runtime, so are there any correctness issues we need to fix here? I only see potential for cleanup with this new functionality.

[tannergooding]

The SIMD size here isn't correct as the size is not always 8. Consider, for example:

runtime/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/AdvSimd.PlatformNotSupported.cs

Lines 15019 to 15024 in 7ff684a

	/// <summary>
	/// <para>void vst1q_u8 (uint8_t * ptr, uint8x16_t val)</para>
	/// <para> A32: VST1.8 { Dd, Dd+1 }, [Rn]</para>
	/// <para> A64: ST1 { Vt.16B }, [Xn]</para>
	/// </summary>
	public static unsafe void Store(byte* address, Vector128<byte> source) { throw new PlatformNotSupportedException(); }

or in the case of AdvSimd_Arm64:

runtime/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Arm/AdvSimd.PlatformNotSupported.cs

Lines 3600 to 3601 in 7ff684a

	/// <summary> A64: ST1 { Vn.16B, Vn+1.16B }, [Xn]</summary>
	public static unsafe void Store(byte* address, (Vector128<byte> Value1, Vector128<byte> Value2) value) { throw new PlatformNotSupportedException(); }

[amanasifkhalid]

I see, so this one needs to look up the size at runtime, too. Let me fix that.

[tannergooding]

I believe this one only has overloads dealing with Vector128

[amanasifkhalid]

You're right; fixed.

[tannergooding]

LGTM. I believe this is all the places that are using tuple and that had been changed from .NET 8, but I notably did not compare line by line to find any other places that may have gotten incorrectly changed

[amanasifkhalid]

LGTM. I believe this is all the places that are using tuple and that had been changed from .NET 8, but I notably did not compare line by line to find any other places that may have gotten incorrectly changed

There is also LoadAndInsertScalar, but that one is special-cased such that during importation, we convert the NamedIntrinsic to one specifying the ValueTuple shape. VectorTableLookup also has a ValueTuple arg, but it doesn't have an immediate argument, and it has a special path in the importer anyway, so I don't think anything else needs to be fixed?

[amanasifkhalid]

@tannergooding should this be backported to .NET 9, since we fixed the SIMD size lookup for AdvSimd.Store? I see some logic during codegen that relies on the SIMD size being correct to pass the right parameters to the emitter.