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-- Environment definition for synthesis.
-- Copyright (C) 2017 Tristan Gingold
--
-- This file is part of GHDL.
--
-- This program is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 2 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program; if not, write to the Free Software
-- Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
-- MA 02110-1301, USA.
with Types; use Types;
with Tables;
with Netlists; use Netlists;
with Netlists.Builders;
with Synth.Source;
package Synth.Environment is
-- A simple signal/variable is either a bit or a std_ulogic
-- signal/variable, or a bus (bit_vector, std_ulogic_vector, signed,
-- unsigned...).
--
-- Complex signals/variables (records, arrays) are decomposed to simple
-- signals/variables.
--
-- Each simple signal/variable is represented by a Wire_Id. Synthesis
-- deals only with these wires or group of them.
type Wire_Id is new Uns32;
No_Wire_Id : constant Wire_Id := 0;
-- A Wire is either a signal, a variable or a port. We need to know the
-- nature of a wire as the assignment semantic is not the same (a variable
-- assignment overwrite the old value, while a signal assignment is
-- effective at the next cycle).
type Wire_Kind is
(
Wire_None,
Wire_Signal, Wire_Variable,
Wire_Input, Wire_Output, Wire_Inout
);
type Assign is new Uns32;
No_Assign : constant Assign := 0;
-- A Wire_Id represents a bit or a vector.
type Wire_Id_Record is record
-- Kind of wire: signal, variable...
-- Set at initialization and cannot be changed.
Kind : Wire_Kind;
-- Used in various algorithms: a flag on a wire. This flag must be
-- cleared after usage.
Mark_Flag : Boolean;
-- Source node that created the wire.
Decl : Source.Syn_Src;
-- The initial net for the wire.
Gate : Net;
Cur_Assign : Assign;
end record;
-- The current value of WID. For variables, this is the last assigned
-- value. For signals, this is the initial value.
function Get_Current_Value (Wid : Wire_Id) return Net;
-- The last assigned value to WID.
function Get_Last_Assigned_Value (Wid : Wire_Id) return Net;
--
type Phi_Id is new Uns32;
No_Phi_Id : constant Phi_Id := 0;
type Assign_Record is record
-- Target of the assignment.
Id : Wire_Id;
-- Assignment is the previous phi context.
Prev : Assign;
-- Corresponding phi context for this wire.
Phi : Phi_Id;
-- Next wire in the phi context.
Chain : Assign;
-- Value assigned.
Value : Net;
end record;
function Get_Wire_Id (W : Assign) return Wire_Id;
function Get_Assign_Chain (Asgn : Assign) return Assign;
function Get_Assign_Value (Asgn : Assign) return Net;
type Phi_Type is private;
-- Create a new phi context.
procedure Push_Phi;
procedure Pop_Phi (Phi : out Phi_Type);
-- Destroy the current phi context and merge it. Can apply only for the
-- first non-top level phi context.
procedure Pop_And_Merge_Phi (Ctxt : Builders.Context_Acc);
-- Handle if statement. According to SEL, the value of the wires are
-- those from T or from F.
procedure Merge_Phis (Ctxt : Builders.Context_Acc;
Sel : Net;
T, F : Phi_Type);
function Sort_Phi (P : Phi_Type) return Assign;
-- In the current phi context, assign VAL to DEST.
procedure Phi_Assign (Dest : Wire_Id; Val : Net);
-- Get current phi context.
function Current_Phi return Phi_Id;
pragma Inline (Current_Phi);
package Wire_Id_Table is new Tables
(Table_Component_Type => Wire_Id_Record,
Table_Index_Type => Wire_Id,
Table_Low_Bound => No_Wire_Id,
Table_Initial => 1024);
package Assign_Table is new Tables
(Table_Component_Type => Assign_Record,
Table_Index_Type => Assign,
Table_Low_Bound => No_Assign,
Table_Initial => 1024);
private
type Phi_Type is record
First : Assign;
Nbr : Uns32;
end record;
package Phis_Table is new Tables
(Table_Component_Type => Phi_Type,
Table_Index_Type => Phi_Id,
Table_Low_Bound => No_Phi_Id,
Table_Initial => 16);
end Synth.Environment;
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