Cleanup MightBeBlittable implementation

- Cleaned up comments around MightBeBlittable and simplified the implementation
- Moved a few more Marshal methods to PInvokeMarshal from InteropExtensions and removed redundant wrappers
- Fixed potential integer truncation in UnsafeAddrOfPinnedArrayElement on 64-bit platforms

[tfs-changeset: 1663953]

3 files changed, 20 insertions, 37 deletions

diff --git a/src/System.Private.Interop/src/Shared/McgHelpers.cs b/src/System.Private.Interop/src/Shared/McgHelpers.cs
index ddabcc53d..370f4d409 100644
--- a/src/System.Private.Interop/src/Shared/McgHelpers.cs
+++ b/src/System.Private.Interop/src/Shared/McgHelpers.cs
@@ -1700,7 +1700,7 @@ namespace System.Runtime.InteropServices
 
                 *((uint*)pCount) = (uint)count;
 
-                InteropExtensions.CopyToNative(data, 0, pDest, count);
+                PInvokeMarshal.CopyToNative(data, 0, pDest, count);
             }
             catch (System.Exception hrExcep)
             {
diff --git a/src/System.Private.Interop/src/System/Runtime/InteropServices/ArrayWithOffset.cs b/src/System.Private.Interop/src/System/Runtime/InteropServices/ArrayWithOffset.cs
index 96997db75..5ee563ca6 100644
--- a/src/System.Private.Interop/src/System/Runtime/InteropServices/ArrayWithOffset.cs
+++ b/src/System.Private.Interop/src/System/Runtime/InteropServices/ArrayWithOffset.cs
@@ -83,7 +83,7 @@ namespace System.Runtime.InteropServices
                     throw new ArgumentException(SR.Arg_NotIsomorphic);
                 }
 
-                if (!arrayObj.IsElementTypeBlittable())
+                if (!arrayObj.IsBlittable())
                 {
                     throw new ArgumentException(SR.Arg_NotIsomorphic);
                 }
diff --git a/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs b/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs
index 6f0cdfa09..28a956b6d 100644
--- a/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs
+++ b/src/System.Private.Interop/src/System/Runtime/InteropServices/Marshal.cs
@@ -227,47 +227,42 @@ namespace System.Runtime.InteropServices
         //====================================================================
         public static void Copy(int[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         public static void Copy(char[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         public static void Copy(short[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         public static void Copy(long[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         public static void Copy(float[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         public static void Copy(double[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         public static void Copy(byte[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         public static void Copy(IntPtr[] source, int startIndex, IntPtr destination, int length)
         {
-            CopyToNative(source, startIndex, destination, length);
-        }
-
-        private static void CopyToNative(Array source, int startIndex, IntPtr destination, int length)
-        {
-            InteropExtensions.CopyToNative(source, startIndex, destination, length);
+            PInvokeMarshal.CopyToNative(source, startIndex, destination, length);
         }
 
         //====================================================================
@@ -275,50 +270,44 @@ namespace System.Runtime.InteropServices
         //====================================================================
         public static void Copy(IntPtr source, int[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
         public static void Copy(IntPtr source, char[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
         public static void Copy(IntPtr source, short[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
         public static void Copy(IntPtr source, long[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
         public static void Copy(IntPtr source, float[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
         public static void Copy(IntPtr source, double[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
         public static void Copy(IntPtr source, byte[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
         public static void Copy(IntPtr source, IntPtr[] destination, int startIndex, int length)
         {
-            CopyToManaged(source, destination, startIndex, length);
+            PInvokeMarshal.CopyToManaged(source, destination, startIndex, length);
         }
 
-        private static void CopyToManaged(IntPtr source, Array destination, int startIndex, int length)
-        {
-            InteropExtensions.CopyToManaged(source, destination, startIndex, length);
-        }
-
-
         //====================================================================
         // Read from memory
         //====================================================================
@@ -1420,18 +1409,12 @@ namespace System.Runtime.InteropServices
         //====================================================================
         public static IntPtr UnsafeAddrOfPinnedArrayElement(Array arr, int index)
         {
-            if (arr == null)
-                throw new ArgumentNullException(nameof(arr));
-            
-            Contract.EndContractBlock();
-            int offset = checked(index * arr.GetElementSize());
-
-            return arr.GetAddrOfPinnedArrayFromEETypeField() + offset;
+            return PInvokeMarshal.UnsafeAddrOfPinnedArrayElement(arr, index);
         }
 
         public static IntPtr UnsafeAddrOfPinnedArrayElement<T>(T[] arr, int index)
         {
-            return UnsafeAddrOfPinnedArrayElement((Array)arr, index);
+            return PInvokeMarshal.UnsafeAddrOfPinnedArrayElement(arr, index);
         }
 
         //====================================================================