Disable load/store vector APIs until Mono adds support for it

[kunalspathak]

Load/Store vector APIs were added in #84510 and the plan was to implement them in mono as part of #93081. However, since it is not in mono yet, when we started using it in #95513, they started throwing PlatformNotSupportedException. It was not caught in #95513 because the mono CI pipeline that test the AdvSimd is only part of llvm-aot which is run as part of runtime-extra-platforms. Given that Preview1 will be out in next couple of weeks, it will be incorrect for Mono to return AdvSimd.IsSupported == true, but throw PlatformNotSupportedException for these APIs. Working with Mono team offline, their plan is to implement them on mono side by Preview2, but until then, for Preview 1, we decided to disable them. This PR contains following changes:

• Revert [libs] Skip AdvSimdEncode on Mono #96829
• Revert Use multi-reg load/store for EncodeToUtf8 #95513
• Wraps all the load/store APIs added in [API Proposal]: Arm64 [Load/Store]Vector64 and [Load/Store]Vector128 for 2,3 and 4 variants #84510 with #if 0
• Disable all the related tests

Once mono implementation is complete, we should revert the changes from this PR as well as enable these tests for mono. One example is:

runtime/src/tests/JIT/HardwareIntrinsics/Arm/Shared/LoadVectorx2Test.template

Line 23 in d145879

[ActiveIssue("https://github.com/dotnet/runtime/pull/92855#issuecomment-1746078670", TestRuntimes.Mono)]

[ghost]

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This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[ghost]

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Issue Details

---

Load/Store vector APIs were added in #84510 and the plan was to implement them in mono as part of #93081. However, since it is not in mono yet, when we started using it in #95513, they started throwing PlatformNotSupportedException. It was not caught in #95513 because the mono CI pipeline that test the AdvSimd is only part of llvm-aot which is run as part of runtime-extra-platforms. Given that Preview1 will be out in next couple of weeks, it will be incorrect for Mono to return AdvSimd.IsSupported == true, but throw PlatformNotSupportedException for these APIs. Working with Mono team offline, their plan is to implement them on mono side by Preview2, but until then, for Preview 1, we decided to disable them. This PR contains following changes:

• Revert [libs] Skip AdvSimdEncode on Mono #96829
• Revert Use multi-reg load/store for EncodeToUtf8 #95513
• Wraps all the load/store APIs added in [API Proposal]: Arm64 [Load/Store]Vector64 and [Load/Store]Vector128 for 2,3 and 4 variants #84510 with #if 0
• Disable all the related tests

Once mono implementation is complete, we should revert the changes from this PR as well as enable these tests for mono. One example is:

runtime/src/tests/JIT/HardwareIntrinsics/Arm/Shared/LoadVectorx2Test.template

Line 23 in d145879

[ActiveIssue("https://github.com/dotnet/runtime/pull/92855#issuecomment-1746078670", TestRuntimes.Mono)]

Author:	kunalspathak
Assignees:	kunalspathak
Labels:	area-System.Runtime.Intrinsics, new-api-needs-documentation
Milestone:	-

[kunalspathak]

@tannergooding@fanyang-mono@SamMonoRT@lambdageek @dotnet/arm64-contrib @JulieLeeMSFT

[kunalspathak]

/azp run runtime-extra-platforms

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[kunalspathak]

@fanyang-mono - could you please double check if the failures from runtime-extra-platforms are not because of this PR and are known?

[a74nh]

• Revert Use multi-reg load/store for EncodeToUtf8 #95513

Have the automatic performance tests run since this patch went in? If not, it'd be good to wait until they are so we can see the impact before merging this.

their plan is to implement them on mono side by Preview2, but until then, for Preview 1, we decided to disable them

@SwapnilGaikwad's upcoming work on DecodeToUtf8 should be pushed out until then.

[kunalspathak]

Have the automatic performance tests run since this patch went in? If not, it'd be good to wait until they are so we can see the impact before merging this.

It did run - dotnet/perf-autofiling-issues#27114

[fanyang-mono]

Thanks for making this change!

[fanyang-mono]

None of the test failures on runtime-extra-platforms are related to this PR.