[armel] Crossgen2 skips methods like GetIndexOfFirstNonAsciiByte_Default that use Vector<T>

[t-mustafin]

The first group of uncompiled methods from #44948 uses Vector<T>. During crossgen2 of GetIndexOfFirstNonAsciiByte_Default() method couple of exceptions is thrown and compilation is rejected.

First exception is thrown from CorInfoImpl.cs#L838 and could be fixed by:

@ -853,7 +853,7 @@ private uint getMethodAttribsInternal(MethodDesc method)
                 DefType owningDefType = method.OwningType as DefType;
                 if (owningDefType != null && VectorOfTFieldLayoutAlgorithm.IsVectorOfTType(owningDefType))
                 {
-                    throw new RequiresRuntimeJitException("This function is using SIMD intrinsics, their size is machine specific");
+                    VerifyMethodSignatureIsStable(method.Signature);
                 }
             }
 #endif

Second exception is thrown from CorInfoImpl.cs#L1556 due to indeterminate Vector<T> size on compiling time. The size depends on similarSpecifiedVector variable. To make similarSpecifiedVector became nonull I made experiment with changing matchingVectorType default value:

@@ -99,7 +99,7 @@ public ReadyToRunCompilerContext(TargetDetails details, SharedGenericsMode gener
             // Only the Arm64 JIT respects the OS rules for vector type abi currently
             _vectorFieldLayoutAlgorithm = new VectorFieldLayoutAlgorithm(_r2rFieldLayoutAlgorithm, (details.Architecture == TargetArchitecture.ARM64) ? true : bubbleIncludesCorelib);
 
-            string matchingVectorType = "Unknown";
+            string matchingVectorType = "Vector128`1";
             if (details.MaximumSimdVectorLength == SimdVectorLength.Vector128Bit)
                 matchingVectorType = "Vector128`1";
             else if (details.MaximumSimdVectorLength == SimdVectorLength.Vector256Bit)

That experiment was successful on armel, Calculator app starts after crossgen2 and GetIndexOfFirstNonAsciiByte_Default method was precompiled by crossgen2.
How machingVectorType or similarSpecifiedVector should be calculated by crossgen2 with _vectorAbiIsStable = true?

cc @davidwrighton @jkotas @alpencolt

[mangod9]

Is this still something which will be fixed for .net 6?

[davidwrighton]

Not unless #46069 reaches a state of passing all the tests. I'm moving this to .NET 7.

[trylek]

I don't think we're going to be able to do anything about this for .NET 8 especially as David is OOF until the end of August, moving to .NET 9.

[steveisok]

I'd still like us to look at this. I'm going to ignore this has been milestone bumped all the way back to 6.0 and move it to 10 :-).