synth: add mdff.

4 files changed, 88 insertions, 12 deletions

diff --git a/src/synth/netlists-builders.adb b/src/synth/netlists-builders.adb
index c591c38a8..99080d9ae 100644
--- a/src/synth/netlists-builders.adb
+++ b/src/synth/netlists-builders.adb
@@ -487,7 +487,15 @@ package body Netlists.Builders is
                                     2 => Create_Input ("rst"),
                                     3 => Create_Input ("rst_val"),
                                     4 => Create_Input ("init")),
-                     Outputs);
+                      Outputs);
+
+      Ctxt.M_Mdff := New_User_Module
+        (Ctxt.Design, New_Sname_Artificial (Get_Identifier ("mdff"), No_Sname),
+         Id_Mdff, 3, 1, 0);
+      Set_Ports_Desc (Ctxt.M_Mdff, (0 => Create_Input ("clk", 1),
+                                    1 => Create_Input ("d"),
+                                    2 => Create_Input ("els")),
+                      Outputs);
    end Create_Dff_Modules;
 
    procedure Create_Assert_Assume_Cover (Ctxt : Context_Acc)
@@ -1338,6 +1346,26 @@ package body Netlists.Builders is
       return O;
    end Build_Iadff;
 
+   function Build_Mdff (Ctxt : Context_Acc;
+                        Clk : Net;
+                        D : Net;
+                        Els : Net) return Net
+   is
+      Wd : constant Width := Get_Width (D);
+      pragma Assert (Get_Width (Clk) = 1);
+      pragma Assert (Get_Width (Els) = Wd);
+      Inst : Instance;
+      O : Net;
+   begin
+      Inst := New_Internal_Instance (Ctxt, Ctxt.M_Mdff);
+      O := Get_Output (Inst, 0);
+      Set_Width (O, Wd);
+      Connect (Get_Input (Inst, 0), Clk);
+      Connect (Get_Input (Inst, 1), D);
+      Connect (Get_Input (Inst, 2), Els);
+      return O;
+   end Build_Mdff;
+
    function Build_Extract
      (Ctxt : Context_Acc; I : Net; Off, W : Width) return Net
    is
diff --git a/src/synth/netlists-builders.ads b/src/synth/netlists-builders.ads
index 36554acad..de2a9da3c 100644
--- a/src/synth/netlists-builders.ads
+++ b/src/synth/netlists-builders.ads
@@ -185,7 +185,12 @@ package Netlists.Builders is
    function Build_Iadff (Ctxt : Context_Acc;
                         Clk : Net;
                         D : Net; Rst : Net; Rst_Val : Net;
-                        Init : Net) return Net;
+                                            Init : Net) return Net;
+
+   function Build_Mdff (Ctxt : Context_Acc;
+                        Clk : Net;
+                        D : Net;
+                        Els : Net) return Net;
 private
    type Module_Arr is array (Module_Id range <>) of Module;
 
@@ -217,6 +222,7 @@ private
       M_Idff : Module;
       M_Adff : Module;
       M_Iadff : Module;
+      M_Mdff : Module;
       M_Truncate : Module_Arr (Truncate_Module_Id);
       M_Extend : Module_Arr (Extend_Module_Id);
       M_Reduce : Module_Arr (Reduce_Module_Id);
diff --git a/src/synth/netlists-gates.ads b/src/synth/netlists-gates.ads
index bb5e64204..848c7a10f 100644
--- a/src/synth/netlists-gates.ads
+++ b/src/synth/netlists-gates.ads
@@ -141,6 +141,7 @@ package Netlists.Gates is
    --           2: INIT (initial value)
    --  Output:  0: Q
    Id_Idff  : constant Module_Id := 52;
+
    --  A DFF with an asynchronous reset and an initial value.
    --  Inputs:  0: CLK
    --           1: D
@@ -150,6 +151,13 @@ package Netlists.Gates is
    --  Output:  0: Q
    Id_Iadff : constant Module_Id := 53;
 
+   --  Multi clock dff.  ELSE is the output of the next DFF.
+   --  Inputs:  0: CLK
+   --           1: D
+   --           2: ELSE
+   --  Output:  0: Q
+   Id_Mdff : constant Module_Id := 54;
+
    --  Width change: truncate or extend.  Sign is know in order to possibly
    --  detect loss of value.
    Id_Utrunc : constant Module_Id := 64;
diff --git a/src/synth/netlists-inference.adb b/src/synth/netlists-inference.adb
index 9f82e7207..8786d42eb 100644
--- a/src/synth/netlists-inference.adb
+++ b/src/synth/netlists-inference.adb
@@ -328,6 +328,7 @@ package body Netlists.Inference is
                        Stmt : Synth.Source.Syn_Src) return Net
    is
       O : constant Net := Get_Output (Last_Mux, 0);
+      Mux_Loc : constant Location_Type := Get_Location (Last_Mux);
       Data : Net;
       Res : Net;
       Sig : Instance;
@@ -335,6 +336,7 @@ package body Netlists.Inference is
       Rst : Net;
       Rst_Val : Net;
       Enable : Net;
+      Els : Net;
    begin
       --  Create and return the DFF.
 
@@ -344,12 +346,31 @@ package body Netlists.Inference is
          Sel : constant Input := Get_Mux2_Sel (Last_Mux);
          I0 : constant Input := Get_Mux2_I0 (Last_Mux);
          I1 : constant Input := Get_Mux2_I1 (Last_Mux);
+         Els_Inst : Instance;
+         Els_Clk : Net;
+         Els_En : Net;
       begin
          --  There must be no 'else' part for clock expression.
-         if not Is_Prev_FF_Value (Get_Driver (I0), Prev_Val, Off) then
-            Error_Msg_Synth
-              (+Stmt, "synchronous code does not expect else part");
-            return Prev_Val;
+         Els := Get_Driver (I0);
+         if Is_Prev_FF_Value (Els, Prev_Val, Off) then
+            --  The loop.
+            Els := No_Net;
+         else
+            Els_Inst := Get_Net_Parent (Els);
+            if Get_Id (Els_Inst) = Id_Mux2 then
+               Extract_Clock (Ctxt, Get_Driver (Get_Mux2_Sel (Els_Inst)),
+                              Els_Clk, Els_En);
+            else
+               Els_Clk := No_Net;
+            end if;
+            if Els_Clk = No_Net then
+               Error_Msg_Synth
+                 (+Stmt, "clocked logic requires clocked logic on else part");
+               Els := No_Net;
+            else
+               Els := Infere_FF (Ctxt, Prev_Val, Off, Els_Inst,
+                                 Els_Clk, Els_En, Stmt);
+            end if;
          end if;
 
          Disconnect (Sel);
@@ -471,6 +492,8 @@ package body Netlists.Inference is
          end loop;
       end;
 
+      Free_Instance (Last_Mux);
+
       if Off = 0
         and then Can_Infere_RAM (Data, Prev_Val)
       then
@@ -493,12 +516,25 @@ package body Netlists.Inference is
       --  Create the FF.
       if Rst = No_Net then
          pragma Assert (Rst_Val = No_Net);
-         if Init /= No_Net then
-            Res := Build_Idff (Ctxt, Clk, D => Data, Init => Init);
+         if Els = No_Net then
+            if Init /= No_Net then
+               Res := Build_Idff (Ctxt, Clk, D => Data, Init => Init);
+            else
+               Res := Build_Dff (Ctxt, Clk, D => Data);
+            end if;
          else
-            Res := Build_Dff (Ctxt, Clk, D => Data);
+            if Init /= No_Net then
+               raise Internal_Error;
+            else
+               Res := Build_Mdff (Ctxt, Clk, D => Data, Els => Els);
+            end if;
          end if;
       else
+         if Els /= No_Net then
+            Error_Msg_Synth
+              (+Stmt, "synchronous code does not expect else part");
+         end if;
+
          if Init /= No_Net then
             Res := Build_Iadff (Ctxt, Clk, D => Data,
                                 Rst => Rst, Rst_Val => Rst_Val,
@@ -508,9 +544,7 @@ package body Netlists.Inference is
                                Rst => Rst, Rst_Val => Rst_Val);
          end if;
       end if;
-      Copy_Location (Res, Last_Mux);
-
-      Free_Instance (Last_Mux);
+      Set_Location (Res, Mux_Loc);
 
       return Res;
    end Infere_FF;