Fix one more Crossgen2 field layout mismatch with runtime

[trylek]

The field offset mismatch in the test

JIT/Regression/JitBlue/Runtime_60035/Runtime_60035.csproj

specific to Crossgen2 composite mode is due to the recent
proliferation of 16-byte alignment specific to Vector across
the runtime repo. Previously, the largest supported alignment
was 8 and X86 was the only architecture not respecting it.

In general the problem is caused by the fact that the native
CoreCLR runtime method table builder calculates field offsets
without taking the method table pointer into account; in the
particular case of the Runtime_60035 test, the class
System.Text.Encodings.Web.OptimizedInboxTextEncoder
has a field named _allowedAsciiCodePoints that is 16-aligned
that exposes this inconsistency.

Thanks

Tomas

/cc @dotnet/crossgen-contrib

Fixes #73728

[trylek]

/azp run runtime-coreclr crossgen2-composite

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[davidwrighton]

This function needs a comment describing what's happening here, and we need a test where we have Sequential field layout used for classes as well as just the standard auto layout.

[trylek]

Thanks David for your feedback. I have improved the code comment and I added a pair of tests exercising the 16-layout with classes using both Auto and Sequential layout. Could you please take another look when you have a chance?

[mangod9]

There is one test failing in the IL.ClassLayout tests. Given this error looks like the test is expecting a nondeterministic layout:

Assert.Equal() Failure\nExpected: Indeterminate\nActual: 8

[davidwrighton]

@mangod9, @trylek, the failing test is testing universal generic layout behavior, which I don't believe has been actually correct since we implemented auto layout. We can comment that test out.

[mangod9]

@mangod9, @trylek, the failing test is testing universal generic layout behavior, which I don't believe has been actually correct since we implemented auto layout. We can comment that test out.

or perhaps just update it to expect 8. Or is that non-deterministic still?

[trylek]

/backport to release/7.0-rc1

[github-actions]

Started backporting to release/7.0-rc1: https://github.com/dotnet/runtime/actions/runs/2894813266