ABI for Int128 and UInt128 is incorrect with regards to native ABI for by value parameter passing

[davidwrighton]

Known ABI issues

• Handling of Int128 types wrapped in structures on X64 SysV and ARM64 platforms
• Use of Int128 types and alignment issues if the parameter needs to be spilled to the stack on Arm64 and SysV
• Register alignment on ARM64 platforms

When this is fixed re-enable $(XunitTestBinBase)/Interop/PInvoke/Int128/Int128Test/

See #73601 for a PR which failed to fix all the issues. Instead #74123 was created to disable problematic scenarios so that we can fix this in the future.

category:correctness
theme:calling-convention
skill-level:expert
cost:medium
impact:small

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Issue Details

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Known ABI issues

• Handling of Int128 types wrapped in structures on X64 SysV and ARM64 platforms
• Use of Int128 types and alignment issues if the parameter needs to be spilled to the stack on Arm64 and SysV
• Register alignment on ARM64 platforms

See #73601 for a PR which failed to fix all the issues. Instead #74123 was created to disable problematic scenarios so that we can fix this in the future.

Author:	davidwrighton
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	8.0.0

[davidwrighton]

We do not appear to have customer demand for pinvokes of this type. I recommend that we move this to the future milestone to keep a record of the issue instead of sliding this from milestone to milestone. @JulieLeeMSFT do you concur?

[tannergooding]

👍from me. The 128-bit integer, vector types, and other ABI primitives are part of the long term things we want to support for interop; but they are fairly niche and don't come up super often. Putting it into future until someone has time to get it working or a motivating customer scenario comes by seems reasonable.

[JulieLeeMSFT]

Sounds good.