[NF] Simplify reductions more.

- Simplify reductions where the iteration range only contains zero or
  one values.

OMCompiler/Compiler/NFFrontEnd/NFSimplifyExp.mo

@@ -193,14 +193,7 @@ algorithm
         callExp;
 
     case Call.TYPED_ARRAY_CONSTRUCTOR() then simplifyArrayConstructor(call);
-
-    case Call.TYPED_REDUCTION()
-      algorithm
-        call.exp := simplify(call.exp);
-        call.iters := list((Util.tuple21(i), simplify(Util.tuple22(i))) for i in call.iters);
-      then
-        Expression.CALL(call);
-
+    case Call.TYPED_REDUCTION() then simplifyReduction(call);
     else callExp;
   end match;
 end simplifyCall;
@@ -345,6 +338,52 @@ algorithm
   end matchcontinue;
 end simplifyArrayConstructor;
 
+function simplifyReduction
+  input Call call;
+  output Expression outExp;
+algorithm
+  outExp := match call
+    local
+      Expression exp, e;
+      list<tuple<InstNode, Expression>> iters;
+      InstNode iter;
+      Dimension dim;
+      Integer dim_size;
+
+    case Call.TYPED_REDUCTION()
+      algorithm
+        iters := list((Util.tuple21(i), simplify(Util.tuple22(i))) for i in call.iters);
+      then matchcontinue iters
+        case {(iter, e)}
+          algorithm
+            Type.ARRAY(dimensions = {dim}) := Expression.typeOf(e);
+            dim_size := Dimension.size(dim);
+
+            if dim_size == 0 then
+              // Iteration range is empty, return default value for reduction.
+              SOME(outExp) := call.defaultExp;
+            elseif dim_size == 1 then
+              // Iteration range is one, return reduction expression with iterator value applied.
+              (Expression.ARRAY(elements = {e}), _) := ExpandExp.expand(e);
+              outExp := Expression.replaceIterator(call.exp, iter, e);
+              outExp := simplify(outExp);
+            else
+              fail();
+            end if;
+          then
+            outExp;
+
+        else
+          algorithm
+            call.exp := simplify(call.exp);
+            call.iters := iters;
+          then
+            Expression.CALL(call);
+
+      end matchcontinue;
+  end match;
+end simplifyReduction;
+
 function simplifySize
   input output Expression sizeExp;
 algorithm

testsuite/flattening/modelica/scodeinst/FuncBuiltinReduction.mo

@@ -46,25 +46,25 @@ end FuncBuiltinReduction;
 //   Real r3 = sum(/*Real*/(r) * 2.0 for r in 1:10);
 //   Real r4 = product(/*Real*/(r) ^ 2.0 for r in 1:5);
 //   Real r5 = sum(/*Real*/(x * y) for x in 1:4, y in 3:9);
-//   Real r6 = min(/*Real*/(r) * 2.0 for r in 1:0);
-//   Real r7 = max(/*Real*/(r) * 2.0 for r in 1:0);
-//   Real r8 = sum(/*Real*/(r) * 2.0 for r in 1:0);
-//   Real r9 = product(/*Real*/(r) * 2.0 for r in 1:0);
+//   Real r6 = 8.777798510069901e+304;
+//   Real r7 = -8.777798510069901e+304;
+//   Real r8 = 0.0;
+//   Real r9 = 1.0;
 //   Integer i1 = min(i - 1 for i in {2, 4, 1});
 //   Integer i2 = max(i for i in {4, 2, 9});
 //   Integer i3 = sum(i * i for i in {1, 2, 3});
 //   Integer i4 = product(i for i in 4:9);
-//   Integer i5 = min(i for i in 1:0);
-//   Integer i6 = max(i for i in 1:0);
-//   Integer i7 = sum(i for i in 1:0);
-//   Integer i8 = product(i for i in 1:0);
+//   Integer i5 = 4611686018427387903;
+//   Integer i6 = -4611686018427387903;
+//   Integer i7 = 0;
+//   Integer i8 = 1;
 //   Boolean b1 = min(not b for b in {false, true});
 //   Boolean b2 = max(i == 2 for i in 1:4);
-//   Boolean b3 = min(b for b in true:false);
-//   Boolean b4 = max(b for b in true:false);
+//   Boolean b3 = true;
+//   Boolean b4 = false;
 //   enumeration(one, two, three) e1 = min(e for e in E.one:E.three);
 //   enumeration(one, two, three) e2 = max(e for e in {E.one, E.two, E.three});
-//   enumeration(one, two, three) e3 = min(e for e in E.three:E.one);
-//   enumeration(one, two, three) e4 = max(e for e in E.three:E.one);
+//   enumeration(one, two, three) e3 = E.three;
+//   enumeration(one, two, three) e4 = E.one;
 // end FuncBuiltinReduction;
 // endResult