Move more casts to the late phase

src/coreclr/jit/helperexpansion.cpp

@@ -1894,9 +1894,9 @@ static int PickCandidatesForTypeCheck(Compiler*              comp,
     CORINFO_CLASS_HANDLE castToCls = comp->gtGetHelperArgClassHandle(clsArg);
     if (castToCls == NO_CLASS_HANDLE)
     {
-        // clsArg doesn't represent a class handle - bail out
-        // TODO-InlineCast: if CSE becomes a problem - move the whole phase after assertion prop,
-        // so we can still rely on VN to get the class handle.
+        // We don't expect the constant handle to be CSE'd here because importer
+        // sets GTF_DONT_CSE for it. The only case when this arg is not a constant is RUNTIMELOOKUP
+        // TODO-InlineCast: we should be able to handle RUNTIMELOOKUP as well.
         JITDUMP("clsArg is not a constant handle - bail out.\n");
         return 0;
     }

src/coreclr/jit/importer.cpp

@@ -5514,7 +5514,16 @@ GenTree* Compiler::impCastClassOrIsInstToTree(
         }
     }
 
-    const bool expandInline = canExpandInline && shouldExpandInline;
+    bool expandInline = canExpandInline && shouldExpandInline;
+
+    // Move expansion to the Late Cast Expansion phase.
+    if (op2->IsIconHandle(GTF_ICON_CLASS_HDL) && (helper != CORINFO_HELP_ISINSTANCEOFCLASS || !isClassExact))
+    {
+        // The only two cases left here are:
+        // 1) isinst <exact class> -- it seems it's profitable to expand such casts early (they don't need helpers)
+        // 2) late cast expansion doesn't yet support GT_RUNTIMELOOKUP as cast-to yet. (TODO-InlineCast)
+        expandInline = false;
+    }
 
     if (!expandInline)
     {
@@ -5529,7 +5538,8 @@ GenTree* Compiler::impCastClassOrIsInstToTree(
         GenTreeCall* call = gtNewHelperCallNode(helper, TYP_REF, op2, op1);
 
         // Instrument this castclass/isinst
-        if ((JitConfig.JitClassProfiling() > 0) && impIsCastHelperEligibleForClassProbe(call) && !isClassExact)
+        if ((JitConfig.JitClassProfiling() > 0) && impIsCastHelperEligibleForClassProbe(call) && !isClassExact &&
+            !compCurBB->isRunRarely())
         {
             // It doesn't make sense to instrument "x is T" or "(T)x" for shared T
             if ((info.compCompHnd->getClassAttribs(pResolvedToken->hClass) & CORINFO_FLG_SHAREDINST) == 0)

src/coreclr/jit/valuenum.h

@@ -1102,7 +1102,8 @@ class ValueNumStore
 
 #ifdef _MSC_VER
 
-                assert(&typeid(T) == &typeid(size_t)); // We represent ref/byref constants as size_t's.
+                assert((&typeid(T) == &typeid(size_t)) ||
+                       (&typeid(T) == &typeid(ssize_t))); // We represent ref/byref constants as size_t/ssize_t
 
 #endif // _MSC_VER