Adding Unsafe API Add nuint that is used by SpanHelpers (#15527)

* Adding Unsafe API Add nuint that is used by SpanHelpers

* Change elementOffset to IntPtr in method signature.

4 files changed, 41 insertions, 0 deletions

diff --git a/src/mscorlib/shared/Internal/Runtime/CompilerServices/Unsafe.cs b/src/mscorlib/shared/Internal/Runtime/CompilerServices/Unsafe.cs
index 8e6c5da47b..1aae1627e5 100644
--- a/src/mscorlib/shared/Internal/Runtime/CompilerServices/Unsafe.cs
+++ b/src/mscorlib/shared/Internal/Runtime/CompilerServices/Unsafe.cs
@@ -110,6 +110,22 @@ namespace Internal.Runtime.CompilerServices
         }
 
         /// <summary>
+        /// Adds an element offset to the given reference.
+        /// </summary>
+        [Intrinsic]
+        [NonVersionable]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ref T Add<T>(ref T source, IntPtr elementOffset)
+        {
+#if CORECLR
+            typeof(T).ToString(); // Type token used by the actual method body
+            throw new PlatformNotSupportedException();
+#else
+            return ref AddByteOffset(ref source, (IntPtr)(elementOffset * (nint)SizeOf<T>()));
+#endif
+        }
+
+        /// <summary>
         /// Adds an element offset to the given pointer.
         /// </summary>
         [Intrinsic]
diff --git a/src/vm/jitinterface.cpp b/src/vm/jitinterface.cpp
index 9bd710fb0b..d584f213af 100644
--- a/src/vm/jitinterface.cpp
+++ b/src/vm/jitinterface.cpp
@@ -7166,6 +7166,29 @@ bool getILIntrinsicImplementationForUnsafe(MethodDesc * ftn,
         methInfo->options = (CorInfoOptions)0;
         return true;
     }
+    else if (tk == MscorlibBinder::GetMethod(METHOD__UNSAFE__BYREF_INTPTR_ADD)->GetMemberDef())
+    {
+        mdToken tokGenericArg = FindGenericMethodArgTypeSpec(MscorlibBinder::GetModule()->GetMDImport());
+
+        static BYTE ilcode[] = { CEE_LDARG_1,
+            CEE_PREFIX1, (CEE_SIZEOF & 0xFF), 0,0,0,0,
+            CEE_MUL,
+            CEE_LDARG_0,
+            CEE_ADD,
+            CEE_RET };
+
+        ilcode[3] = (BYTE)(tokGenericArg);
+        ilcode[4] = (BYTE)(tokGenericArg >> 8);
+        ilcode[5] = (BYTE)(tokGenericArg >> 16);
+        ilcode[6] = (BYTE)(tokGenericArg >> 24);
+
+        methInfo->ILCode = const_cast<BYTE*>(ilcode);
+        methInfo->ILCodeSize = sizeof(ilcode);
+        methInfo->maxStack = 2;
+        methInfo->EHcount = 0;
+        methInfo->options = (CorInfoOptions)0;
+        return true;
+    }
     else if (tk == MscorlibBinder::GetMethod(METHOD__UNSAFE__BYREF_ADD_BYTE_OFFSET)->GetMemberDef())
     {
         static BYTE ilcode[] = { CEE_LDARG_0, CEE_LDARG_1, CEE_ADD, CEE_RET };
diff --git a/src/vm/metasig.h b/src/vm/metasig.h
index bbd326ebe3..9976ed12f2 100644
--- a/src/vm/metasig.h
+++ b/src/vm/metasig.h
@@ -293,6 +293,7 @@ DEFINE_METASIG(GM(PtrVoid_T_RetVoid, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, P(v) M(0)
 DEFINE_METASIG(GM(RefTFrom_RetRefTTo, IMAGE_CEE_CS_CALLCONV_DEFAULT, 2, r(M(0)), r(M(1))))
 DEFINE_METASIG(GM(Obj_RetT, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, j, M(0)))
 DEFINE_METASIG(GM(RefT_Int_RetRefT, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, r(M(0)) i, r(M(0))))
+DEFINE_METASIG(GM(RefT_IntPtr_RetRefT, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, r(M(0)) I, r(M(0))))
 DEFINE_METASIG(GM(PtrVoid_Int_RetPtrVoid, IMAGE_CEE_CS_CALLCONV_DEFAULT, 1, P(v) i, P(v)))
 
 DEFINE_METASIG_T(SM(SafeHandle_RefBool_RetIntPtr, C(SAFE_HANDLE) r(F), I ))
diff --git a/src/vm/mscorlib.h b/src/vm/mscorlib.h
index 39038415aa..511271d074 100644
--- a/src/vm/mscorlib.h
+++ b/src/vm/mscorlib.h
@@ -775,6 +775,7 @@ DEFINE_METHOD(UNSAFE,               SIZEOF,                 SizeOf, NoSig)
 DEFINE_METHOD(UNSAFE,               BYREF_AS,               As, GM_RefTFrom_RetRefTTo)
 DEFINE_METHOD(UNSAFE,               OBJECT_AS,              As, GM_Obj_RetT)
 DEFINE_METHOD(UNSAFE,               BYREF_ADD,              Add, GM_RefT_Int_RetRefT)
+DEFINE_METHOD(UNSAFE,               BYREF_INTPTR_ADD,       Add, GM_RefT_IntPtr_RetRefT)
 DEFINE_METHOD(UNSAFE,               PTR_ADD,                Add, GM_PtrVoid_Int_RetPtrVoid)
 DEFINE_METHOD(UNSAFE,               BYREF_BYTE_OFFSET,      ByteOffset, NoSig)
 DEFINE_METHOD(UNSAFE,               BYREF_ADD_BYTE_OFFSET,  AddByteOffset, NoSig)