Drop cast helper call for (TTo)obj.MemberwiseClone()

EgorBo · Nov 29, 2020 · 43282cd · 43282cd
1 parent 15f7a79
commit 43282cd
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Showing 4 changed files with 33 additions and 0 deletions.
diff --git a/src/coreclr/src/System.Private.CoreLib/src/System/Object.CoreCLR.cs b/src/coreclr/src/System.Private.CoreLib/src/System/Object.CoreCLR.cs
@@ -16,6 +16,7 @@ public partial class Object
         // object.  This is always a shallow copy of the instance. The method is protected
         // so that other object may only call this method on themselves.  It is intended to
         // support the ICloneable interface.
+        [Intrinsic]
         protected unsafe object MemberwiseClone()
         {
             object clone = RuntimeHelpers.AllocateUninitializedClone(this);

diff --git a/src/coreclr/src/jit/importer.cpp b/src/coreclr/src/jit/importer.cpp
@@ -4789,6 +4789,13 @@ NamedIntrinsic Compiler::lookupNamedIntrinsic(CORINFO_METHOD_HANDLE method)
                 result = NI_System_Type_IsAssignableTo;
             }
         }
+        else if (strcmp(className, "Object") == 0)
+        {
+            if (strcmp(methodName, "MemberwiseClone") == 0)
+            {
+                result = NI_System_Object_MemberwiseClone;
+            }
+        }
     }
     else if (strcmp(namespaceName, "System.Threading") == 0)
     {

diff --git a/src/coreclr/src/jit/morph.cpp b/src/coreclr/src/jit/morph.cpp
@@ -9062,6 +9062,30 @@ GenTree* Compiler::fgMorphCall(GenTreeCall* call)
         call->gtCallArgs->SetNode(dest);
     }
 
+    if (call->gtCallMethHnd == eeFindHelper(CORINFO_HELP_CHKCASTARRAY)) // not only array?
+    {
+        GenTree* arg0 = call->gtCallArgs->GetNode();
+        GenTree* arg1 = call->gtCallArgs->GetNext()->GetNode();
+
+        if (arg0->OperIs(GT_CNS_INT) && arg1->IsCall() &&
+            (lookupNamedIntrinsic(arg1->AsCall()->gtCallMethHnd) == NI_System_Object_MemberwiseClone))
+        {
+            CORINFO_CLASS_HANDLE castToHandle = (CORINFO_CLASS_HANDLE)arg0->AsIntCon()->IconValue();
+
+            bool isExact = false;
+            bool isNonNull = false;
+            CORINFO_CLASS_HANDLE castFromHandle =
+                gtGetClassHandle(arg1->AsCall()->gtCallThisArg->GetNode(), &isExact, &isNonNull);
+
+            if (castToHandle != NO_CLASS_HANDLE &&
+                castFromHandle != NO_CLASS_HANDLE &&
+                info.compCompHnd->compareTypesForCast(castFromHandle, castToHandle) == TypeCompareState::Must) // or canCast() ?
+            {
+                return fgMorphTree(arg1);
+            }
+        }
+    }
+
     /* Process the "normal" argument list */
     call = fgMorphArgs(call);
     noway_assert(call->gtOper == GT_CALL);

diff --git a/src/coreclr/src/jit/namedintrinsiclist.h b/src/coreclr/src/jit/namedintrinsiclist.h
@@ -43,6 +43,7 @@ enum NamedIntrinsic : unsigned short
     NI_System_Type_get_IsValueType,
     NI_System_Type_IsAssignableFrom,
     NI_System_Type_IsAssignableTo,
+    NI_System_Object_MemberwiseClone,
 
     // These are used by HWIntrinsics but are defined more generally
     // to allow dead code optimization and handle the recursion case