[NF] Various improvements.

- Fix ordering of equations/statements during simplification, when
  replacing an if-equation/statement with the first branch.
- Unroll for-loops in algorithms when the range has size 1.

Belonging to [master]:
  - #2901

Author: perost

3rdParty

@@ -218,10 +218,22 @@ public
   algorithm
     isZero := match dim
       case INTEGER() then dim.size == 0;
+      case ENUM() then Type.enumSize(dim.enumType) == 0;
       else false;
     end match;
   end isZero;
 
+  function isOne
+    input Dimension dim;
+    output Boolean isOne;
+  algorithm
+    isOne := match dim
+      case INTEGER() then dim.size == 1;
+      case ENUM() then Type.enumSize(dim.enumType) == 1;
+      else false;
+    end match;
+  end isOne;
+
   function subscriptType
     "Returns the expected type of a subscript for the given dimension."
     input Dimension dim;

Compiler/NFFrontEnd/NFDimension.mo

@@ -1098,8 +1098,8 @@ algorithm
 
   while RangeIterator.hasNext(range_iter) loop
     (range_iter, val) := RangeIterator.next(range_iter);
-    unrolled_body := list(Equation.mapExp(eq,
-      function Expression.replaceIterator(iterator = iter, iteratorValue = val)) for eq in body);
+    unrolled_body := Equation.mapExpList(body,
+      function Expression.replaceIterator(iterator = iter, iteratorValue = val));
     unrolled_body := flattenEquations(unrolled_body, prefix);
     equations := listAppend(unrolled_body, equations);
   end while;

Compiler/NFFrontEnd/NFFlatten.mo

@@ -46,6 +46,7 @@ import NFBinding.Binding;
 import Variable = NFVariable;
 import Algorithm = NFAlgorithm;
 import Dimension = NFDimension;
+import Subscript = NFSubscript;
 
 protected
 import MetaModelica.Dangerous.*;
@@ -250,6 +251,8 @@ algorithm
     local
       Expression e, lhs, rhs;
       Type ty;
+      Dimension dim;
+      list<Statement> body;
 
     case Statement.ASSIGNMENT()
       algorithm
@@ -265,8 +268,17 @@ algorithm
 
     case Statement.FOR(range = SOME(e))
       algorithm
-        if not Type.isEmptyArray(Expression.typeOf(e)) then
-          stmt.range := SimplifyExp.simplifyOpt(stmt.range);
+        ty := Expression.typeOf(e);
+        dim := Type.nthDimension(ty, 1);
+
+        if Dimension.isOne(dim) then
+          e := Expression.applySubscript(Subscript.INDEX(Expression.INTEGER(1)), e);
+          body := Statement.mapExpList(stmt.body,
+            function Expression.replaceIterator(iterator = stmt.iterator, iteratorValue = e));
+          body := simplifyStatements(body);
+          statements := listAppend(body, statements);
+        elseif not Dimension.isZero(dim) then
+          stmt.range := SOME(SimplifyExp.simplify(e));
           stmt.body := simplifyStatements(stmt.body);
           statements := stmt :: statements;
         end if;
@@ -363,7 +375,7 @@ 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);
+              elements := listAppend(listReverse(simplifyEquations(body)), elements);
               return;
             else
               // Otherwise just discard the rest of the branches.
@@ -431,7 +443,7 @@ 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(simplifyFunc(body), elements);
+        elements := listAppend(listReverse(simplifyFunc(body)), elements);
         return;
       else
         // Otherwise just discard the rest of the branches.

Compiler/NFFrontEnd/NFSimplifyModel.mo

@@ -822,6 +822,16 @@ public
     ENUMERATION(typePath = name) := ty;
   end enumName;
 
+  function enumSize
+    input Type ty;
+    output Integer size;
+  protected
+    list<String> literals;
+  algorithm
+    ENUMERATION(literals = literals) := ty;
+    size := listLength(literals);
+  end enumSize;
+
   function box
     input Type ty;
     output Type boxedType;