Fold more "OBJ(ADDR(LCL))" patterns in multi-reg morphing (#70207)

It is unfortunate that we have to expand this code, but it
will avoid diffs for a TYP_STRUCT LCL_FLD change.

src/coreclr/jit/morph.cpp

@@ -3792,30 +3792,33 @@ GenTree* Compiler::fgMorphMultiregStructArg(CallArg* arg)
     GenTree*                   argValue   = argNode; // normally argValue will be arg, but see right below
     unsigned                   structSize = 0;
 
-    if (argNode->TypeGet() != TYP_STRUCT)
+    if (argNode->OperGet() == GT_OBJ)
     {
-        structSize = genTypeSize(argNode->TypeGet());
-    }
-    else if (argNode->OperGet() == GT_OBJ)
-    {
-        GenTreeObj*        argObj    = argNode->AsObj();
-        const ClassLayout* objLayout = argObj->GetLayout();
-        structSize                   = objLayout->GetSize();
+        GenTreeObj*  argObj    = argNode->AsObj();
+        ClassLayout* objLayout = argObj->GetLayout();
+        structSize             = objLayout->GetSize();
 
         // If we have a GT_OBJ of a GT_ADDR then we set argValue to the child node of the GT_ADDR.
-        GenTree* op1 = argObj->gtOp1;
-        if (op1->OperGet() == GT_ADDR)
+        // TODO-ADDR: always perform this transformation in local morph and delete this code.
+        GenTree* addr = argObj->Addr();
+        if (addr->OperGet() == GT_ADDR)
         {
-            GenTree* underlyingTree = op1->AsOp()->gtOp1;
+            GenTree* location = addr->AsOp()->gtOp1;
 
-            // Only update to the same type.
-            if (underlyingTree->OperIs(GT_LCL_VAR))
+            if (location->OperIsLocalRead())
             {
-                const LclVarDsc* varDsc = lvaGetDesc(underlyingTree->AsLclVar());
-                if (ClassLayout::AreCompatible(varDsc->GetLayout(), objLayout))
+                if (!location->OperIs(GT_LCL_VAR) ||
+                    !ClassLayout::AreCompatible(lvaGetDesc(location->AsLclVarCommon())->GetLayout(), objLayout))
                 {
-                    argValue = underlyingTree;
+                    unsigned lclOffset = location->AsLclVarCommon()->GetLclOffs();
+
+                    location->ChangeType(argObj->TypeGet());
+                    location->SetOper(GT_LCL_FLD);
+                    location->AsLclFld()->SetLclOffs(lclOffset);
+                    location->AsLclFld()->SetLayout(objLayout);
                 }
+
+                argValue = location;
             }
         }
     }
@@ -3824,6 +3827,10 @@ GenTree* Compiler::fgMorphMultiregStructArg(CallArg* arg)
         LclVarDsc* varDsc = lvaGetDesc(argNode->AsLclVarCommon());
         structSize        = varDsc->lvExactSize;
     }
+    else if (!argNode->TypeIs(TYP_STRUCT))
+    {
+        structSize = genTypeSize(argNode);
+    }
     else
     {
         structSize = info.compCompHnd->getClassSize(objClass);