synth: handle null array comparison. Fix #1311

3 files changed, 45 insertions, 11 deletions

diff --git a/src/synth/netlists-folds.adb b/src/synth/netlists-folds.adb
index 9aa070238..c4138d0cd 100644
--- a/src/synth/netlists-folds.adb
+++ b/src/synth/netlists-folds.adb
@@ -20,7 +20,6 @@
 
 with Types_Utils; use Types_Utils;
 
-with Netlists.Gates; use Netlists.Gates;
 with Netlists.Utils; use Netlists.Utils;
 with Netlists.Locations; use Netlists.Locations;
 
@@ -296,4 +295,32 @@ package body Netlists.Folds is
       Set_Location (N, Loc);
       return N;
    end Build2_And;
+
+   function Build2_Compare (Ctxt : Context_Acc;
+                            Id   : Compare_Module_Id;
+                            L, R : Net) return Net
+   is
+      W : constant Width := Get_Width (L);
+   begin
+      if W > 0 then
+         --  A real gate.
+         return Build_Compare (Ctxt, Id, L, R);
+      end if;
+
+      pragma Assert (Get_Width (R) = 0);
+      case Id is
+         when Id_Eq
+            | Id_Sle
+            | Id_Ule
+            | Id_Sge
+            | Id_Uge =>
+            return Build_Const_UB32 (Ctxt, 1, 1);
+         when Id_Ne
+            | Id_Slt
+            | Id_Ult
+            | Id_Sgt
+            | Id_Ugt =>
+            return Build_Const_UB32 (Ctxt, 0, 1);
+      end case;
+   end Build2_Compare;
 end Netlists.Folds;
diff --git a/src/synth/netlists-folds.ads b/src/synth/netlists-folds.ads
index 1aa020df9..6c63f49bc 100644
--- a/src/synth/netlists-folds.ads
+++ b/src/synth/netlists-folds.ads
@@ -18,6 +18,7 @@
 --  Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
 --  MA 02110-1301, USA.
 
+with Netlists.Gates; use Netlists.Gates;
 with Netlists.Builders; use Netlists.Builders;
 
 package Netlists.Folds is
@@ -78,5 +79,11 @@ package Netlists.Folds is
    --  If A is No_Net, simply return B so that it is possible to easily build
    --  chain of conditions.
    function Build2_And (Ctxt : Context_Acc; A, B : Net; Loc : Location_Type)
-                       return Net;
+                        return Net;
+
+   --  Like Build_Compare but handle net of width 0.
+   function Build2_Compare (Ctxt : Context_Acc;
+                            Id   : Compare_Module_Id;
+                            L, R : Net) return Net;
+
 end Netlists.Folds;
diff --git a/src/synth/synth-oper.adb b/src/synth/synth-oper.adb
index 4e1c16cb8..c34ec4875 100644
--- a/src/synth/synth-oper.adb
+++ b/src/synth/synth-oper.adb
@@ -417,7 +417,7 @@ package body Synth.Oper is
       begin
          pragma Assert (Left_Type = Right_Type);
          pragma Assert (Res_Type = Expr_Typ);
-         N := Build_Compare
+         N := Build2_Compare
            (Ctxt, Id, Get_Net (Ctxt, Left), Get_Net (Ctxt, Right));
          Set_Location (N, Expr);
          return Create_Value_Net (N, Res_Type);
@@ -430,7 +430,7 @@ package body Synth.Oper is
          Sel, N : Net;
       begin
          pragma Assert (Left_Type = Right_Type);
-         Sel := Build_Compare (Ctxt, Id, L, R);
+         Sel := Build2_Compare (Ctxt, Id, L, R);
          Set_Location (Sel, Expr);
          N := Build_Mux2 (Ctxt, Sel, R, L);
          Set_Location (N, Expr);
@@ -446,7 +446,7 @@ package body Synth.Oper is
             Warning_Msg_Synth
               (+Expr, "comparing non-numeric vector is unexpected");
             if Left.Typ.W = Right.Typ.W then
-               N := Build_Compare
+               N := Build2_Compare
                  (Ctxt, Id, Get_Net (Ctxt, Left), Get_Net (Ctxt, Right));
                Set_Location (N, Expr);
                return Create_Value_Net (N, Res_Type);
@@ -468,7 +468,7 @@ package body Synth.Oper is
          N : Net;
       begin
          N := Synth_Uresize (Ctxt, Right, Left.Typ.W, Expr);
-         N := Build_Compare (Ctxt, Id, Get_Net (Ctxt, Left), N);
+         N := Build2_Compare (Ctxt, Id, Get_Net (Ctxt, Left), N);
          Set_Location (N, Expr);
          return Create_Value_Net (N, Res_Type);
       end Synth_Compare_Uns_Nat;
@@ -479,7 +479,7 @@ package body Synth.Oper is
          N : Net;
       begin
          N := Synth_Uresize (Ctxt, Left, Right.Typ.W, Expr);
-         N := Build_Compare (Ctxt, Id, Get_Net (Ctxt, Right), N);
+         N := Build2_Compare (Ctxt, Id, Get_Net (Ctxt, Right), N);
          Set_Location (N, Expr);
          return Create_Value_Net (N, Res_Type);
       end Synth_Compare_Nat_Uns;
@@ -490,7 +490,7 @@ package body Synth.Oper is
          N : Net;
       begin
          N := Synth_Sresize (Ctxt, Right, Left.Typ.W, Expr);
-         N := Build_Compare (Ctxt, Id, Get_Net (Ctxt, Left), N);
+         N := Build2_Compare (Ctxt, Id, Get_Net (Ctxt, Left), N);
          Set_Location (N, Expr);
          return Create_Value_Net (N, Res_Typ);
       end Synth_Compare_Sgn_Int;
@@ -501,7 +501,7 @@ package body Synth.Oper is
          N : Net;
       begin
          N := Synth_Sresize (Ctxt, Left, Right.Typ.W, Expr);
-         N := Build_Compare (Ctxt, Id, N, Get_Net (Ctxt, Right));
+         N := Build2_Compare (Ctxt, Id, N, Get_Net (Ctxt, Right));
          Set_Location (N, Expr);
          return Create_Value_Net (N, Res_Typ);
       end Synth_Compare_Int_Sgn;
@@ -540,7 +540,7 @@ package body Synth.Oper is
       begin
          L1 := Synth_Uresize (Ctxt, Left, W, Expr);
          R1 := Synth_Uresize (Ctxt, Right, W, Expr);
-         N := Build_Compare (Ctxt, Id, L1, R1);
+         N := Build2_Compare (Ctxt, Id, L1, R1);
          Set_Location (N, Expr);
          return Create_Value_Net (N, Res_Type);
       end Synth_Compare_Uns_Uns;
@@ -554,7 +554,7 @@ package body Synth.Oper is
       begin
          L1 := Synth_Sresize (Ctxt, Left, W, Expr);
          R1 := Synth_Sresize (Ctxt, Right, W, Expr);
-         N := Build_Compare (Ctxt, Id, L1, R1);
+         N := Build2_Compare (Ctxt, Id, L1, R1);
          Set_Location (N, Expr);
          return Create_Value_Net (N, Res_Typ);
       end Synth_Compare_Sgn_Sgn;