Move EEClassLayoutInfo::CollectLayoutFieldMetadataThrowing to class.cpp (#22932)

Move `EEClassLayoutInfo::CollectLayoutFieldMetadataThrowing` to class.cpp and out of fieldmarshaler.cpp.

This change co-locates `EEClassLayoutInfo::CollectLayoutFieldMetadataThrowing` with the rest of the implementation of `EEClassLayoutInfo`. Additionally, this PR separates out the field blittability check into a separate function instead of burying it in `CollectLayoutFieldMetadataThrowing`.

Finally, it adds a small optimization in the field marshaler implementations where if a field's native size is statically known, the code returns that value instead of calling into one of the FieldMarshaler "virtual" calls.

Originally part of #21415, but extracted out to make that PR smaller.

1 files changed, 30 insertions, 2 deletions

diff --git a/src/vm/fieldmarshaler.h b/src/vm/fieldmarshaler.h
index 2e1b011c5c..e83835844a 100644
--- a/src/vm/fieldmarshaler.h
+++ b/src/vm/fieldmarshaler.h
@@ -31,7 +31,6 @@
 #endif // FEATURE_PREJIT
 
 // Forward refernces
-class EEClassLayoutInfo;
 class FieldDesc;
 class MethodTable;
 
@@ -89,6 +88,36 @@ enum NStructFieldType
 #define DEFAULT_PACKING_SIZE 32
 
 
+enum class ParseNativeTypeFlags
+{
+    None    = 0x00,
+    IsAnsi  = 0x01,
+#ifdef FEATURE_COMINTEROP
+    IsWinRT = 0x02,
+#endif // FEATURE_COMINTEROP
+};
+
+VOID ParseNativeType(Module*    pModule,
+    PCCOR_SIGNATURE             pCOMSignature,
+    DWORD                       cbCOMSignature,
+    ParseNativeTypeFlags        flags,
+    LayoutRawFieldInfo*         pfwalk,
+    PCCOR_SIGNATURE             pNativeType,
+    ULONG                       cbNativeType,
+    IMDInternalImport*          pInternalImport,
+    mdTypeDef                   cl,
+    const SigTypeContext *      pTypeContext,
+    BOOL                       *pfDisqualifyFromManagedSequential
+#ifdef _DEBUG
+    ,
+    LPCUTF8                     szNamespace,
+    LPCUTF8                     szClassName,
+    LPCUTF8                     szFieldName
+#endif
+);
+
+BOOL IsFieldBlittable(FieldMarshaler* pFM);
+
 //=======================================================================
 // This is invoked from the class loader while building the data structures for a type.
 // This function checks if explicit layout metadata exists.
@@ -456,7 +485,6 @@ protected:
     }
 #endif // _DEBUG
 
-
     RelativeFixupPointer<PTR_FieldDesc> m_pFD;      // FieldDesc
     UINT32           m_dwExternalOffset;    // offset of field in the fixed portion
     NStructFieldType m_nft;