[NF] Fix equation order for branch selection.

Belonging to [master]:
  - #2921
  - OpenModelica/OpenModelica-testsuite#1120

Author: perost

Compiler/NFFrontEnd/NFFlatten.mo

@@ -997,7 +997,7 @@ algorithm
         algorithm
           // Flatten the condition and body of the branch.
           cond := flattenExp(cond, prefix);
-          eql := listReverseInPlace(flattenEquations(eql, prefix));
+          eql := flattenEquations(eql, prefix);
 
           // Evaluate structural conditions.
           if var <= Variability.STRUCTURAL_PARAMETER then
@@ -1022,12 +1022,12 @@ algorithm
               equations := listAppend(eql, equations);
             else
               // Otherwise, append this branch.
-              bl := Equation.makeBranch(cond, eql, var) :: bl;
+              bl := Equation.makeBranch(cond, listReverseInPlace(eql), var) :: bl;
             end if;
           elseif not Expression.isFalse(cond) then
             // Only add the branch to the list of branches if the condition is not
             // literal false, otherwise just drop it since it will never trigger.
-            bl := Equation.makeBranch(cond, eql, var) :: bl;
+            bl := Equation.makeBranch(cond, listReverseInPlace(eql), var) :: bl;
           end if;
         then
           bl;

Compiler/NFFrontEnd/NFSimplifyModel.mo

@@ -376,7 +376,9 @@ algorithm
           if Expression.isTrue(cond) then
             if listEmpty(accum) then
               // If it's the first branch, remove the if and keep only the branch body.
-              elements := listAppend(simplifyEquations(body), elements);
+              for eq in body loop
+                elements := simplifyEquation(eq, elements);
+              end for;
               return;
             else
               // Otherwise just discard the rest of the branches.