Some work-arounds for Ceval of zero-size arrays

The Values.mo structure does not store the type of the array which means
that `Values.ARRAY({})` becomes `{} /* T_UNKNOWN[0] */` instead of
containing the actual type. We now have some work-arounds for this case:
- cevalIfConstant will not try to evaluate literal values
- If an empty array is returned in cevalIfConstant, we backpatch the
  array type to the expected type (but this only works for the top-level
  expression; hopefully this is enough to not propagate unknown
  dimensions too far though).

Belonging to [master]:
  - OpenModelica/OMCompiler#2074

Compiler/FrontEnd/Ceval.mo

@@ -885,79 +885,63 @@ public function cevalIfConstant
    or if the expression is a call of parameter constness whose return type
    contains unknown dimensions (in which case we need to determine the size of
    those dimensions)."
-  input FCore.Cache inCache;
+  input output FCore.Cache cache;
   input FCore.Graph inEnv;
-  input DAE.Exp inExp;
-  input DAE.Properties inProp;
+  input output DAE.Exp exp;
+  input output DAE.Properties prop;
   input Boolean impl;
   input SourceInfo inInfo;
-  output FCore.Cache outCache;
-  output DAE.Exp outExp;
-  output DAE.Properties outProp;
 algorithm
-  (outCache, outExp, outProp) :=
-  matchcontinue(inCache, inEnv, inExp, inProp, impl, inInfo)
+  if Expression.isEvaluatedConst(exp) then
+    // Don't mess up the dimensions, etc by using the Values module
+    return;
+  end if;
+  (cache, exp, prop) := matchcontinue prop
     local
-        DAE.Exp e;
-        Values.Value v;
-        FCore.Cache cache;
-        DAE.Properties prop;
+      Values.Value v;
       DAE.Type tp;
 
-    /* adrpo: this is not needed! we do dimension propagation on function call!
-    case (_, _, e as DAE.CALL(attr = DAE.CALL_ATTR(ty = DAE.T_ARRAY(dims = _))),
-        DAE.PROP(constFlag = DAE.C_PARAM()), _, _)
-      equation
-        (e, prop) = cevalWholedimRetCall(e, inCache, inEnv, inInfo, 0);
-      then
-        (inCache, e, prop);*/
-
-    case (_, _, e, DAE.PROP(constFlag = DAE.C_PARAM(), type_ = tp), _, _) // BoschRexroth specifics
-      equation
-        false = Flags.getConfigBool(Flags.CEVAL_EQUATION);
-      then
-        (inCache, e, DAE.PROP(tp, DAE.C_VAR()));
-
-    case (_, _, e, DAE.PROP(constFlag = DAE.C_CONST()), _, _)
-      equation
-        (cache, v, _) = ceval(inCache, inEnv, e, impl, NONE(), Absyn.NO_MSG(), 0);
-        e = ValuesUtil.valueExp(v);
-      then
-        (cache, e, inProp);
+    case DAE.PROP(constFlag = DAE.C_PARAM(), type_ = tp)
+      // BoschRexroth specifics
+      guard not Flags.getConfigBool(Flags.CEVAL_EQUATION)
+      then (cache, exp, DAE.PROP(tp, DAE.C_VAR()));
 
-    case (_, _, e, DAE.PROP_TUPLE(), _, _)
-      equation
-        DAE.C_CONST() = Types.propAllConst(inProp);
-        (cache, v, _) = ceval(inCache, inEnv, e, false, NONE(), Absyn.NO_MSG(), 0);
-        e = ValuesUtil.valueExp(v);
-      then
-        (cache, e, inProp);
+    case DAE.PROP(constFlag = DAE.C_CONST(), type_ = tp)
+      algorithm
+        (cache, v, _) := ceval(cache, inEnv, exp, impl, NONE(), Absyn.NO_MSG(), 0);
+        exp := ValuesUtil.valueExp(v);
+        exp := ValuesUtil.fixZeroSizeArray(exp, tp);
+      then (cache, exp, prop);
 
-    case (_, _, _, DAE.PROP_TUPLE(), _, _) // BoschRexroth specifics
-      equation
-        false = Flags.getConfigBool(Flags.CEVAL_EQUATION);
-        DAE.C_PARAM() = Types.propAllConst(inProp);
+    case DAE.PROP_TUPLE()
+      algorithm
+        DAE.C_CONST() := Types.propAllConst(prop);
+        (cache, v, _) := ceval(cache, inEnv, exp, false, NONE(), Absyn.NO_MSG(), 0);
+        exp := ValuesUtil.valueExp(v);
+      then (cache, exp, prop);
+
+    case DAE.PROP_TUPLE()
+      // BoschRexroth specifics
+      guard not Flags.getConfigBool(Flags.CEVAL_EQUATION)
+      algorithm
+        DAE.C_PARAM() := Types.propAllConst(prop);
         print(" tuple non constant evaluation not implemented yet\n");
-      then
-        fail();
+      then fail();
 
-    case (_, _, e, _, _, _)
-      equation
-        true = Expression.isConst(e); // Structural parameters and the like... we can ceval them if we want to
-        false = Config.acceptMetaModelicaGrammar();
-        // false = Expression.isConstValue(e);
-        // print("Try ceval: " + ExpressionDump.printExpStr(e) + "; expect " + Types.unparseType(Types.getPropType(inProp)) + "\n");
-        (_, v, _) = ceval(inCache, inEnv, e, impl, NONE(), Absyn.NO_MSG(), 0);
-        // print("Ceval'ed constant: " + ExpressionDump.printExpStr(inExp) + " => " + ValuesUtil.valString(v) + "\n");
-        e = ValuesUtil.valueExp(v);
-        // print("Ceval'ed constant: " + ExpressionDump.printExpStr(inExp) + "\n");
-      then (inCache, e, inProp);
+    case _
+      // Structural parameters and the like... we can ceval them if we want to
+      guard Expression.isConst(exp) and not Config.acceptMetaModelicaGrammar()
+      algorithm
+        (_, v, _) := ceval(cache, inEnv, exp, impl, NONE(), Absyn.NO_MSG(), 0);
+        exp := ValuesUtil.valueExp(v);
+        exp := ValuesUtil.fixZeroSizeArray(exp, Types.getPropType(prop));
+      then (cache, exp, prop);
 
     else
-      equation
+      algorithm
         // If we fail to evaluate, at least we should simplify the expression
-        (e,_) = ExpressionSimplify.simplify1(inExp);
-      then (inCache, e, inProp);
+        (exp,_) := ExpressionSimplify.simplify1(exp);
+      then (cache, exp, prop);
 
   end matchcontinue;
 end cevalIfConstant;

Compiler/FrontEnd/ExpressionSimplify.mo

@@ -1300,6 +1300,10 @@ algorithm
         e = Expression.makeImpureBuiltinCall("delay",{e,e3,e4},tp);
       then DAE.UNARY(op,e);
 
+    // The sum of an empty array is simply the sum of its elements
+    case DAE.CALL(path=Absyn.IDENT("sum"),expLst={DAE.ARRAY(array={})}, attr=DAE.CALL_ATTR(ty=tp1))
+      then Expression.makeConstZero(tp1);
+
     // To calculate sums, first try matrix concatenation
     case DAE.CALL(path=Absyn.IDENT("sum"),expLst={DAE.MATRIX(ty=tp1,matrix=mexpl)},attr=DAE.CALL_ATTR(ty=tp2))
       equation

Compiler/FrontEnd/Static.mo

@@ -8462,10 +8462,8 @@ algorithm
     // checkModel this should succeed anyway, since we might be checking a function
     // that takes a vector of unknown size. So pretend that the dimension is 1.
     case (e, (DAE.DIM_UNKNOWN() :: ad), prop)
-      algorithm
-        true := Flags.getConfigBool(Flags.CHECK_MODEL);
-      then
-        vectorizeCall(e, DAE.DIM_INTEGER(1) :: ad, inSlots, prop, info);
+      guard Flags.getConfigBool(Flags.CHECK_MODEL)
+      then vectorizeCall(e, DAE.DIM_INTEGER(1) :: ad, inSlots, prop, info);
 
     /* Scalar expression, i.e function call */
     case (e as DAE.CALL(),(dim :: ad),DAE.PROP(tp,c))
@@ -8474,8 +8472,7 @@ algorithm
         exp_type := Types.simplifyType(Types.liftArray(tp, dim)) "pass type of vectorized result expr";
         vect_exp := vectorizeCallScalar(e, exp_type, int_dim, inSlots);
         tp := Types.liftArray(tp, dim);
-      then
-        vectorizeCall(vect_exp, ad, inSlots, DAE.PROP(tp,c),info);
+      then vectorizeCall(vect_exp, ad, inSlots, DAE.PROP(tp,c),info);
 
     /* array expression of function calls */
     case (DAE.ARRAY(),(dim :: ad),DAE.PROP(tp,c))
@@ -8484,8 +8481,7 @@ algorithm
         // _ = Types.simplifyType(Types.liftArray(tp, dim));
         vect_exp := vectorizeCallArray(inExp, int_dim, inSlots);
         tp := Types.liftArrayRight(tp, dim);
-      then
-        vectorizeCall(vect_exp, ad, inSlots, DAE.PROP(tp,c),info);
+      then vectorizeCall(vect_exp, ad, inSlots, DAE.PROP(tp,c),info);
 
     /* Multiple dimensions are possible to change to a reduction, like:
      * f(arr1,arr2) => array(f(x,y) thread for x in arr1, y in arr2)

Compiler/FrontEnd/ValuesUtil.mo

@@ -2346,5 +2346,16 @@ algorithm
   end match;
 end typeConvertRecord;
 
+public function fixZeroSizeArray "Work-around for Values.ARRAY({}) becoming T_UNKNOWN in ValuesUtil.valueExp"
+  input output DAE.Exp e;
+  input DAE.Type ty;
+algorithm
+  e := match e
+    case DAE.ARRAY(ty=DAE.T_ARRAY(ty=DAE.T_UNKNOWN()), scalar=false, array={})
+      then DAE.ARRAY(ty, not Types.isArray(Types.unliftArray(ty)), {});
+    else e;
+  end match;
+end fixZeroSizeArray;
+
 annotation(__OpenModelica_Interface="frontend");
 end ValuesUtil;