[DAEMode] create aux variable for cse variables

 - this attempts to fix initialization issue in DAEmode

Belonging to [master]:
  - #2460

Compiler/BackEnd/BackendVariable.mo

@@ -48,6 +48,7 @@ import BackendDump;
 import BaseHashSet;
 import BaseHashTable;
 import ComponentReference;
+import CommonSubExpression;
 import DAEUtil;
 import Debug;
 import ElementSource;
@@ -1247,6 +1248,17 @@ algorithm
   end match;
 end isAlgebraicOldState;
 
+public function isCSEVar
+"Return true if variable is introduced by wrapFunctionCall and prefixed with '$cse'"
+  input BackendDAE.Var inVar;
+  output Boolean outBoolean;
+algorithm
+  outBoolean := match (inVar)
+    case (BackendDAE.VAR()) guard CommonSubExpression.isCSECref(inVar.varName) then true;
+    else false;
+  end match;
+end isCSEVar;
+
 public function hasMayerTermAnno
 "author: Vitalij Ruge
  Return true if variable has isMayer=true annotation"

Compiler/BackEnd/DAEMode.mo

@@ -298,7 +298,7 @@ algorithm
       constant Boolean debug = false;
 
     case ({eq}, false, false)
-      guard(Util.boolAndList(list(CommonSubExpression.isCSECref(v.varName) for v in vars)))
+      guard(Util.boolAndList(list(BackendVariable.isCSEVar(v) for v in vars)))
       equation
         newResVars = list(BackendVariable.setVarKind(v, BackendDAE.DAE_AUX_VAR()) for v in vars);
         new_eq = BackendEquation.setEquationAttributes(eq, BackendDAE.EQ_ATTR_DEFAULT_AUX);
@@ -492,6 +492,8 @@ algorithm
       algorithm
 
         (discVars, contVars) := List.splitOnTrue(inVars, BackendVariable.isVarDiscrete);
+        (newAuxVars, contVars) := List.splitOnTrue(contVars, BackendVariable.BackendVariable.isCSEVar);
+        discVars := listAppend(newAuxVars,discVars);
         (discEqns, contEqns) := getDiscAndContEqns(inVars, inEqns, discVars, contVars, traverserArgs.shared.functionTree);
 
         // create discrete