Imported Upstream version 5.16.0.100

Former-commit-id: 38faa55fb9669e35e7d8448b15c25dc447f25767

mcs/class/corlib/ReferenceSources/Buffer.cs

@@ -1,3 +1,12 @@
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
+using System.Runtime.CompilerServices;
+using System.Runtime;
+
 namespace System
 {
 	partial class Buffer
@@ -213,7 +222,28 @@ namespace System
 
 		internal static unsafe void Memmove (byte *dest, byte *src, uint len)
 		{
+            if (((nuint)dest - (nuint)src < len) || ((nuint)src - (nuint)dest < len))
+				goto PInvoke;
 			Memcpy (dest, src, (int) len);
+			return;
+
+            PInvoke:
+            RuntimeImports.Memmove(dest, src, len);
+		}
+
+		internal static void Memmove<T>(ref T destination, ref T source, nuint elementCount)
+		{
+            if (!RuntimeHelpers.IsReferenceOrContainsReferences<T>()) {
+                unsafe {
+                    fixed (byte* pDestination = &Unsafe.As<T, byte>(ref destination), pSource = &Unsafe.As<T, byte>(ref source))
+                        Memmove(pDestination, pSource, (uint)elementCount * (uint)Unsafe.SizeOf<T>());
+                }
+			} else {
+                unsafe {
+                    fixed (byte* pDestination = &Unsafe.As<T, byte>(ref destination), pSource = &Unsafe.As<T, byte>(ref source))
+                        RuntimeImports.Memmove_wbarrier(pDestination, pSource, (uint)elementCount, typeof(T).TypeHandle.Value);
+				}
+			}
 		}
 	}
 }

mcs/class/corlib/ReferenceSources/String.cs

@@ -34,11 +34,19 @@
 //
 //
 
+#if BIT64
+using nuint = System.UInt64;
+#else
+using nuint = System.UInt32;
+#endif
+
 using System.Runtime.CompilerServices;
 using System.Text;
 using System.Globalization;
 using System.Collections;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Diagnostics.Private;
 
 namespace System
 {
@@ -51,15 +59,6 @@ namespace System
 
 		public static readonly String Empty;
 
-		public unsafe static implicit operator ReadOnlySpan<char> (String value)
-		{
-			if (value == null)
-				return default;
-
-			fixed (void* start = &value._firstChar)
-				return new ReadOnlySpan<char> (start, value.Length);
-		}
-
 		internal unsafe int IndexOfUnchecked (string value, int startIndex, int count)
 		{
 			int valueLen = value.Length;
@@ -202,7 +201,12 @@ namespace System
 			if (this.Length < value.Length || _firstChar != value._firstChar)
 				return false;
 
-			return value.Length == 1 ? true : StartsWithOrdinalHelper (this, value);
+			return value.Length == 1 ?
+				true :
+				SpanHelpers.SequenceEqual (
+					ref Unsafe.As<char, byte> (ref this.GetRawStringData ()),
+					ref Unsafe.As<char, byte> (ref value.GetRawStringData ()),
+					((nuint)value.Length) * 2);
 		}
 
 		[MethodImplAttribute (MethodImplOptions.InternalCall)]

mcs/class/corlib/ReferenceSources/TextInfo.cs

@@ -1,4 +1,5 @@
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 namespace System.Globalization
 {
@@ -198,7 +199,7 @@ namespace System.Globalization
 			return c;
 		}
 
-		static unsafe int InternalCompareStringOrdinalIgnoreCase (String strA, int indexA, String strB, int indexB, int lenA, int lenB)
+		internal static unsafe int InternalCompareStringOrdinalIgnoreCase (String strA, int indexA, String strB, int indexB, int lenA, int lenB)
 		{
 			if (strA == null) {
 				return strB == null ? 0 : -1;
@@ -229,6 +230,47 @@ namespace System.Globalization
 				return lengthA - lengthB;
 			}
 		}
+
+		internal void ToLowerAsciiInvariant (ReadOnlySpan<char> source, Span<char> destination)
+		{
+			for (int i = 0; i < source.Length; i++)
+			{
+				destination [i] = ToLowerAsciiInvariant (source [i]);
+			}
+		}
+
+		internal void ToUpperAsciiInvariant (ReadOnlySpan<char> source, Span<char> destination)
+		{
+			for (int i = 0; i < source.Length; i++)
+			{
+				destination [i] = ToUpperAsciiInvariant (source[i]);
+			}
+		}
+
+		internal unsafe void ChangeCase (ReadOnlySpan<char> source, Span<char> destination, bool toUpper)
+		{
+			if (source.IsEmpty)
+				return;
+
+			var ti = CultureInfo.CurrentCulture.TextInfo;
+
+			fixed (char* pSource = &MemoryMarshal.GetReference (source))
+			fixed (char* pResult = &MemoryMarshal.GetReference (destination)) {
+				int length = 0;
+				char* a = pSource, b = pResult;
+				if (toUpper) {
+					while (length < source.Length) {
+						*b++ = ti.ToUpper (*a++);
+						length++;
+					}
+				} else {
+					while (length < source.Length) {
+						*b++ = ti.ToLower (*a++);
+						length++;
+					}
+				}
+			}
+		}
 	}
 
 	static class TextInfoToUpperData