netlists-memories: allow intermediate signals to detect sync read.

Fix #1079

3 files changed, 18 insertions, 2 deletions

diff --git a/src/synth/netlists-memories.adb b/src/synth/netlists-memories.adb
index c1b8603ec..908087f9e 100644
--- a/src/synth/netlists-memories.adb
+++ b/src/synth/netlists-memories.adb
@@ -410,9 +410,9 @@ package body Netlists.Memories is
       Dff_Out := Get_Output (Dff_Inst, 0);
 
       if Mux_Inp = Get_Input (Mux_Inst, 1) then
-         return Get_Input_Net (Mux_Inst, 2) = Dff_Out;
+         return Skip_Signal (Get_Input_Net (Mux_Inst, 2)) = Dff_Out;
       else
-         return Get_Input_Net (Mux_Inst, 1) = Dff_Out;
+         return Skip_Signal (Get_Input_Net (Mux_Inst, 1)) = Dff_Out;
       end if;
    end Is_Enable_Dff;
 
diff --git a/src/synth/netlists-utils.adb b/src/synth/netlists-utils.adb
index 59eb086d5..3f9a9fd46 100644
--- a/src/synth/netlists-utils.adb
+++ b/src/synth/netlists-utils.adb
@@ -175,6 +175,18 @@ package body Netlists.Utils is
       end case;
    end Get_Net_Element;
 
+   function Skip_Signal (N : Net) return Net
+   is
+      Inst : constant Instance := Get_Net_Parent (N);
+   begin
+      case Get_Id (Inst) is
+         when Id_Signal =>
+            return Get_Input_Net (Inst, 0);
+         when others =>
+            return N;
+      end case;
+   end Skip_Signal;
+
    function Is_Connected (O : Net) return Boolean is
    begin
       return Get_First_Sink (O) /= No_Input;
diff --git a/src/synth/netlists-utils.ads b/src/synth/netlists-utils.ads
index 79838b614..be6f58e9e 100644
--- a/src/synth/netlists-utils.ads
+++ b/src/synth/netlists-utils.ads
@@ -79,6 +79,10 @@ package Netlists.Utils is
    --  selection of the same net.
    function Same_Net (L, R : Net) return Boolean;
 
+   --  If N is the output of a signal or isignal, return the driver of the
+   --  input.
+   function Skip_Signal (N : Net) return Net;
+
    function Clog2 (W : Width) return Width;
 
    --  Used at many places.