netlists: do not remove net gates that have an attribute

3 files changed, 36 insertions, 25 deletions

diff --git a/src/synth/netlists-cleanup.adb b/src/synth/netlists-cleanup.adb
index 22f02b761..2f741e3f3 100644
--- a/src/synth/netlists-cleanup.adb
+++ b/src/synth/netlists-cleanup.adb
@@ -128,29 +128,32 @@ package body Netlists.Cleanup is
               |  Id_Port
               |  Id_Enable
               |  Id_Nop =>
-               declare
-                  Inp : Input;
-                  In_Drv : Net;
-                  O : Net;
-               begin
-                  Inp := Get_Input (Inst, 0);
-                  In_Drv := Get_Driver (Inp);
-                  O := Get_Output (Inst, 0);
-                  if In_Drv /= No_Net then
-                     --  Only when the output is driven.
-                     Disconnect (Inp);
-                     Redirect_Inputs (O, In_Drv);
-                  else
-                     Disconnect (Get_First_Sink (O));
-                  end if;
+               --  Keep gates with an attribute.
+               if not Has_Attribute (Inst) then
+                  declare
+                     Inp : Input;
+                     In_Drv : Net;
+                     O : Net;
+                  begin
+                     Inp := Get_Input (Inst, 0);
+                     In_Drv := Get_Driver (Inp);
+                     O := Get_Output (Inst, 0);
+                     if In_Drv /= No_Net then
+                        --  Only when the output is driven.
+                        Disconnect (Inp);
+                        Redirect_Inputs (O, In_Drv);
+                     else
+                        Disconnect (Get_First_Sink (O));
+                     end if;
 
-                  if Get_Id (Inst) = Id_Ioutput then
-                     --  Disconnect the initial value.
-                     Disconnect (Get_Input (Inst, 1));
-                  end if;
+                     if Get_Id (Inst) = Id_Ioutput then
+                        --  Disconnect the initial value.
+                        Disconnect (Get_Input (Inst, 1));
+                     end if;
 
-                  Remove_Instance (Inst);
-               end;
+                     Remove_Instance (Inst);
+                  end;
+               end if;
             when others =>
                null;
          end case;
diff --git a/src/synth/netlists.adb b/src/synth/netlists.adb
index 18ca51992..24c39df50 100644
--- a/src/synth/netlists.adb
+++ b/src/synth/netlists.adb
@@ -1232,11 +1232,16 @@ package body Netlists is
       return Modules_Table.Table (M).Attrs;
    end Get_Attributes;
 
+   function Has_Attribute (Inst : Instance) return Boolean is
+   begin
+      return Instances_Table.Table (Inst).Has_Attr;
+   end Has_Attribute;
+
    function Get_First_Attribute (Inst : Instance) return Attribute
    is
       pragma Assert (Is_Valid (Inst));
    begin
-      if not Instances_Table.Table (Inst).Has_Attr then
+      if not Has_Attribute (Inst) then
          return No_Attribute;
       end if;
       declare
diff --git a/src/synth/netlists.ads b/src/synth/netlists.ads
index 2f4c604e3..a516efee4 100644
--- a/src/synth/netlists.ads
+++ b/src/synth/netlists.ads
@@ -343,6 +343,9 @@ package Netlists is
    --  Get the next attribute for the same instance.
    function Get_Attribute_Next (Attr : Attribute) return Attribute;
 
+   --  Return True iff INST has at least one attribute.
+   function Has_Attribute (Inst : Instance) return Boolean;
+
    --  Display some usage stats on the standard error.
    procedure Disp_Stats;
 private
@@ -445,9 +448,9 @@ private
 
    type Instance_Record is record
       --  The instance is instantiated in Parent.
-      Parent     : Module;
-      Has_Attr  : Boolean;  --  Set when there is at least one attribute.
-      Flag4      : Boolean;
+      Parent   : Module;
+      Has_Attr : Boolean;  --  Set when there is at least one attribute.
+      Flag4    : Boolean;
 
       --  Instances are in a doubly-linked list.
       Prev_Instance : Instance;