grt-processes.adb

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   begin
      if Lock.Process /= Get_Current_Process_Id then
         Internal_Error ("protected_leave(1)");
      end if;

      if Lock.Count <= 0 then
         Internal_Error ("protected_leave(2)");
      end if;
      Lock.Count := Lock.Count - 1;
      if Lock.Count = 0 then
         Lock.Process := Nul_Process_Id;
      end if;
   end Ghdl_Protected_Leave;

   procedure Ghdl_Protected_Init (Obj : System.Address)
   is
      Lock : Object_Lock_Acc_Acc := To_Lock_Acc_Acc (Obj);
   begin
      Lock.all := new Object_Lock'(Process => Nul_Process_Id,
                                   Count => 0);
   end Ghdl_Protected_Init;

   procedure Ghdl_Protected_Fini (Obj : System.Address)
   is
      procedure Deallocate is new Ada.Unchecked_Deallocation
        (Object => Object_Lock, Name => Object_Lock_Acc);

      Lock : Object_Lock_Acc_Acc := To_Lock_Acc_Acc (Obj);
   begin
      if Lock.all.Count /= 0 or Lock.all.Process /= Nul_Process_Id then
         Internal_Error ("protected_fini");
      end if;
      Deallocate (Lock.all);
   end Ghdl_Protected_Fini;

   function Compute_Next_Time return Std_Time
   is
      Res : Std_Time;
   begin
      --  f) The time of the next simulation cycle, Tn, is determined by
      --     setting it to the earliest of
      --     1) TIME'HIGH
      Res := Std_Time'Last;

      --     2) The next time at which a driver becomes active, or
      Res := Std_Time'Min (Res, Grt.Signals.Find_Next_Time);

      if Res = Current_Time then
         return Res;
      end if;

      --     3) The next time at which a process resumes.
      for I in Process_Table.First .. Process_Table.Last loop
         declare
            Proc : Process_Type renames Process_Table.Table (I);
         begin
            if Proc.State = State_Wait
              and then Proc.Timeout < Res
              and then Proc.Timeout >= 0
            then
               --  No signals to be updated.
               Grt.Signals.Flush_Active_List;

               if Proc.Timeout = Current_Time then
                  --  Can't be better.
                  return Current_Time;
               else
                  Res := Proc.Timeout;
               end if;
            end if;
         end;
      end loop;

      return Res;
   end Compute_Next_Time;

   procedure Disp_Process_Name (Stream : Grt.Stdio.FILEs; Proc : Process_Id)
   is
   begin
      Grt.Rtis_Utils.Put (Stream, Process_Table.Table (Proc).Rti);
   end Disp_Process_Name;

   type Run_Handler is access function return Integer;
   --  pragma Convention (C, Run_Handler);

   function Run_Through_Longjump (Hand : Run_Handler) return Integer;
   pragma Import (C, Run_Through_Longjump, "__ghdl_run_through_longjump");

   --  Run resumed processes.
   --  If POSTPONED is true, resume postponed processes, else resume
   --  non-posponed processes.
   --  Returns one of these values:
   --  No process has been run.
   Run_None : constant Integer := 1;
   --  At least one process was run.
   Run_Resumed : constant Integer := 2;
   --  Simulation is finished.
   Run_Finished : constant Integer := 3;
   --  Failure, simulation should stop.
   Run_Failure : constant Integer := -1;

   function Run_Processes (Postponed : Boolean) return Integer
   is
      Status : Integer;
   begin
      Status := Run_None;

      if Options.Flag_Stats then
         Stats.Start_Processes;
      end if;

      for I in Process_Table.First .. Process_Table.Last loop
         if Process_Table.Table (I).Postponed = Postponed
           and Process_Table.Table (I).Resumed
         then
            if Grt.Options.Trace_Processes then
               Grt.Astdio.Put ("run process ");
               Disp_Process_Name (Stdio.stdout, I);
               Grt.Astdio.Put (" [");
               Grt.Astdio.Put (Stdio.stdout, Process_Table.Table (I).This);
               Grt.Astdio.Put ("]");
               Grt.Astdio.New_Line;
            end if;
            Process_Table.Table (I).Resumed := False;
            Status := Run_Resumed;
            Cur_Proc_Id := I;
            Cur_Proc := To_Acc (Process_Table.Table (I)'Address);
            if Cur_Proc.State = State_Sensitized then
               Cur_Proc.Subprg.all (Cur_Proc.This);
            else
               Stack_Switch (Cur_Proc.Stack, Main_Stack);
            end if;
            if Grt.Options.Checks then
               Ghdl_Signal_Internal_Checks;
               Grt.Stack2.Check_Empty (Stack2);
            end if;
         end if;
      end loop;

      if Options.Flag_Stats then
         Stats.End_Processes;
      end if;
      return Status;
   end Run_Processes;

   function Initialization_Phase return Integer
   is
      Status : Integer;
   begin
      --  LRM93 12.6.4
      --  At the beginning of initialization, the current time, Tc, is assumed
      --  to be 0 ns.
      Current_Time := 0;

      --  The initialization phase consists of the following steps:
      --  - The driving value and the effective value of each explicitly
      --    declared signal are computed, and the current value of the signal
      --    is set to the effective value.  This value is assumed to have been
      --    the value of the signal for an infinite length of time prior to
      --    the start of the simulation.
      Init_Signals;

      --  - The value of each implicit signal of the form S'Stable(T) or
      --    S'Quiet(T) is set to true.  The value of each implicit signal of
      --    the form S'Delayed is set to the initial value of its prefix, S.
      --  GHDL: already done when the signals are created.
      null;

      --  - The value of each implicit GUARD signal is set to the result of
      --    evaluating the corresponding guard expression.
      null;

      --  - Each nonpostponed process in the model is executed until it
      --    suspends.
      Status := Run_Processes (Postponed => False);
      if Status = Run_Failure then
         return Run_Failure;
      end if;

      --  - Each postponed process in the model is executed until it suspends.
      Status := Run_Processes (Postponed => True);
      if Status = Run_Failure then
         return Run_Failure;
      end if;

      --  - The time of the next simulation cycle (which in this case is the
      --    first simulation cycle), Tn, is calculated according to the rules
      --    of step f of the simulation cycle, below.
      Current_Time := Compute_Next_Time;

      return Run_Resumed;
   end Initialization_Phase;

   --  Launch a simulation cycle.
   --  Set FINISHED to true if this is the last cycle.
   function Simulation_Cycle return Integer
   is
      Tn : Std_Time;
      Status : Integer;
   begin
      --  LRM93 12.6.4
      --  A simulation cycle consists of the following steps:
      --
      --  a) The current time, Tc is set equal to Tn.  Simulation is complete
      --     when Tn = TIME'HIGH and there are no active drivers or process
      --     resumptions at Tn.
      --  GHDL: this is done at the last step of the cycle.
      null;

      --  b) Each active explicit signal in the model is updated.  (Events
      --     may occur on signals as a result).
      --  c) Each implicit signal in the model is updated.  (Events may occur
      --     on signals as a result.)
      if Options.Flag_Stats then
         Stats.Start_Update;
      end if;
      Update_Signals;
      if Options.Flag_Stats then
         Stats.End_Update;
      end if;

      --  d) For each process P, if P is currently sensitive to a signal S and
      --     if an event has occured on S in this simulation cycle, then P
      --     resumes.
      for I in Process_Table.First .. Process_Table.Last loop
         declare
            Proc : Process_Type renames Process_Table.Table (I);
            El : Sensitivity_Acc;
         begin
            case Proc.State is
               when State_Sensitized =>
                  null;
               when State_Delayed =>
                  if Proc.Timeout = Current_Time then
                     Proc.Timeout := Bad_Time;
                     Proc.Resumed := True;
                     Proc.State := State_Sensitized;
                  end if;
               when State_Wait =>
                  if Proc.Timeout = Current_Time then
                     Proc.Timeout := Bad_Time;
                     Proc.Resumed := True;
                     Proc.State := State_Timeout;
                  else
                     El := Proc.Sensitivity;
                     while El /= null loop
                        if El.Sig.Event then
                           Proc.Resumed := True;
                           exit;
                        else
                           El := El.Next;
                        end if;
                     end loop;
                  end if;
               when State_Timeout =>
                  Internal_Error ("process in timeout");
               when State_Dead =>
                  null;
            end case;
         end;
      end loop;

      --  e) Each nonpostponed that has resumed in the current simulation cycle
      --     is executed until it suspends.
      Status := Run_Processes (Postponed => False);
      if Status = Run_Failure then
         return Run_Failure;
      end if;

      --  f) The time of the next simulation cycle, Tn, is determined by
      --     setting it to the earliest of
      --     1) TIME'HIGH
      --     2) The next time at which a driver becomes active, or
      --     3) The next time at which a process resumes.
      --     If Tn = Tc, then the next simulation cycle (if any) will be a
      --     delta cycle.
      if Options.Flag_Stats then
         Stats.Start_Next_Time;
      end if;
      Tn := Compute_Next_Time;
      if Options.Flag_Stats then
         Stats.End_Next_Time;
      end if;

      --  g) If the next simulation cycle will be a delta cycle, the remainder
      --     of the step is skipped.
      --     Otherwise, each postponed process that has resumed but has not
      --     been executed since its last resumption is executed until it
      --     suspends.  Then Tn is recalculated according to the rules of
      --     step f.  It is an error if the execution of any postponed
      --     process causes a delta cycle to occur immediatly after the
      --     current simulation cycle.
      if Tn = Current_Time then
         if Current_Time = Last_Time and then Status = Run_None then
            return Run_Finished;
         else
            Current_Delta := Current_Delta + 1;
            return Run_Resumed;
         end if;
      else
         Current_Delta := 0;
         Status := Run_Processes (Postponed => True);
         if Status = Run_Resumed then
            Flush_Active_List;
            if Options.Flag_Stats then
               Stats.Start_Next_Time;
            end if;
            Tn := Compute_Next_Time;
            if Options.Flag_Stats then
               Stats.End_Next_Time;
            end if;
            if Tn = Current_Time then
               Error ("postponed process causes a delta cycle");
            end if;
         elsif Status = Run_Failure then
            return Run_Failure;
         end if;
         Current_Time := Tn;
         return Run_Resumed;
      end if;
   end Simulation_Cycle;

   function Simulation return Integer
   is
      use Options;
      Status : Integer;
   begin
      --Put_Line ("grt.processes:" & Process_Id'Image (Process_Table.Last)
      --          & " process(es)");

--       if Disp_Sig_Types then
--          Grt.Disp.Disp_Signals_Type;
--       end if;

      Grt.Hooks.Call_Start_Hooks;

      Status := Run_Through_Longjump (Initialization_Phase'Access);
      if Status /= Run_Resumed then
         return -1;
      end if;

      Current_Delta := 0;
      Nbr_Delta_Cycles := 0;
      Nbr_Cycles := 0;
      if Trace_Signals then
         Grt.Disp_Signals.Disp_All_Signals;
      end if;

      if Current_Time /= 0 then
         --  This is the end of a cycle.
         Cycle_Time := 0;
         Grt.Hooks.Call_Cycle_Hooks;
      end if;

      loop
         Cycle_Time := Current_Time;
         if Disp_Time then
            Grt.Disp.Disp_Now;
         end if;
         Status := Run_Through_Longjump (Simulation_Cycle'Access);
         exit when Status = Run_Failure;
         if Trace_Signals then
            Grt.Disp_Signals.Disp_All_Signals;
         end if;

         --  Statistics.
         if Current_Delta = 0 then
            Nbr_Cycles := Nbr_Cycles + 1;
         else
            Nbr_Delta_Cycles := Nbr_Delta_Cycles + 1;
         end if;

         exit when Status = Run_Finished;
         if Current_Delta = 0 then
            Grt.Hooks.Call_Cycle_Hooks;
         end if;

         if Current_Delta >= Stop_Delta then
            Error ("simulation stopped by --stop-delta");
            exit;
         end if;
         if Current_Time > Stop_Time then
            Info ("simulation stopped by --stop-time");
            exit;
         end if;
      end loop;

      Grt.Hooks.Call_Finish_Hooks;

      if Status = Run_Failure then
         return -1;
      else
         return 0;
      end if;
   end Simulation;

end Grt.Processes;