Late cast expansion: more improvements

src/coreclr/jit/compiler.h

@@ -4904,7 +4904,6 @@ class Compiler
     bool impIsImplicitTailCallCandidate(
         OPCODE curOpcode, const BYTE* codeAddrOfNextOpcode, const BYTE* codeEnd, int prefixFlags, bool isRecursive);
 
-    bool impIsClassExact(CORINFO_CLASS_HANDLE classHnd);
     bool impCanSkipCovariantStoreCheck(GenTree* value, GenTree* array);
 
     methodPointerInfo* impAllocateMethodPointerInfo(const CORINFO_RESOLVED_TOKEN& token, mdToken tokenConstrained);
@@ -8011,6 +8010,7 @@ class Compiler
                                size_t               bufferSize = 0);
 
     const char* eeGetClassName(CORINFO_CLASS_HANDLE clsHnd, char* buffer = nullptr, size_t bufferSize = 0);
+    bool eeIsClassExact(CORINFO_CLASS_HANDLE clsHnd);
 
     void eePrintObjectDescription(const char* prefix, CORINFO_OBJECT_HANDLE handle);
     const char* eeGetShortClassName(CORINFO_CLASS_HANDLE clsHnd);

src/coreclr/jit/eeinterface.cpp

@@ -569,6 +569,42 @@ const char* Compiler::eeGetClassName(CORINFO_CLASS_HANDLE clsHnd, char* buffer,
     return printer.GetBuffer();
 }
 
+//------------------------------------------------------------------------
+// eeIsClassExact: check if a class handle can only describe values
+//    of exactly one class.
+//
+// Arguments:
+//    classHnd - handle for class in question
+//
+// Return value:
+//    true if class is final and not subject to special casting from
+//    variance or similar.
+//
+// Note:
+//    We are conservative on arrays of primitive types here.
+//
+bool Compiler::eeIsClassExact(CORINFO_CLASS_HANDLE clsHnd)
+{
+    DWORD flags     = info.compCompHnd->getClassAttribs(clsHnd);
+    DWORD flagsMask = CORINFO_FLG_FINAL | CORINFO_FLG_VARIANCE | CORINFO_FLG_ARRAY;
+
+    if ((flags & flagsMask) == CORINFO_FLG_FINAL)
+    {
+        return true;
+    }
+    if ((flags & flagsMask) == (CORINFO_FLG_FINAL | CORINFO_FLG_ARRAY))
+    {
+        CORINFO_CLASS_HANDLE arrayElementHandle = nullptr;
+        CorInfoType          type               = info.compCompHnd->getChildType(clsHnd, &arrayElementHandle);
+
+        if ((type == CORINFO_TYPE_CLASS) || (type == CORINFO_TYPE_VALUECLASS))
+        {
+            return eeIsClassExact(arrayElementHandle);
+        }
+    }
+    return false;
+}
+
 //------------------------------------------------------------------------
 // eeGetShortClassName: Returns class name with no instantiation.
 //

src/coreclr/jit/gentree.cpp

@@ -14034,7 +14034,7 @@ GenTree* Compiler::gtFoldTypeCompare(GenTree* tree)
 
     // if both classes are "final" (e.g. System.String[]) we can replace the comparison
     // with `true/false` + null check.
-    if ((objCls != NO_CLASS_HANDLE) && (pIsExact || impIsClassExact(objCls)))
+    if ((objCls != NO_CLASS_HANDLE) && (pIsExact || eeIsClassExact(objCls)))
     {
         TypeCompareState tcs = info.compCompHnd->compareTypesForEquality(objCls, clsHnd);
         if (tcs != TypeCompareState::May)
@@ -18585,7 +18585,7 @@ CORINFO_CLASS_HANDLE Compiler::gtGetClassHandle(GenTree* tree, bool* pIsExact, b
         }
         else
         {
-            *pIsExact = impIsClassExact(objClass);
+            *pIsExact = eeIsClassExact(objClass);
         }
     }