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-- Build utilities
-- Copyright (C) 2019 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, see <gnu.org/licenses>.
with Netlists.Locations; use Netlists.Locations;
package body Netlists.Butils is
procedure Synth_Case (Ctxt : Context_Acc;
Sel : Net;
Els : in out Case_Element_Array;
Default : Net;
Res : out Net;
Sel_Loc : Location_Type)
is
Wd : constant Width := Get_Width (Sel);
Mask : Uns64;
Sub_Sel : Net;
Lels : Natural;
Iels : Natural;
Oels : Natural;
begin
Lels := Els'Last;
Iels := Els'First;
if Lels < Iels then
-- No choices
Res := Default;
return;
end if;
-- Handle SEL bits by 2, so group case_element by 4.
for I in 1 .. Natural (Wd / 2) loop
Mask := Shift_Left (not 0, Natural (2 * I));
Iels := Els'First;
Oels := Els'First;
while Iels <= Lels loop
declare
type Net4 is array (0 .. 3) of Net;
G : Net4;
S_Group : constant Uns64 := Els (Iels).Sel and Mask;
S_El : Uns64;
El_Idx : Natural;
Rsel : Net;
begin
-- Extract 2 bits from the selector.
G := (others => Default);
for K in 0 .. 3 loop
exit when Iels > Lels;
S_El := Els (Iels).Sel;
exit when (S_El and Mask) /= S_Group;
El_Idx := Natural
(Shift_Right (S_El, Natural (2 * (I - 1))) and 3);
G (El_Idx) := Els (Iels).Val;
Iels := Iels + 1;
end loop;
if G (0) /= No_Net
and G (1) /= No_Net
and G (2) /= No_Net
and G (3) /= No_Net
then
-- The 4 choices are available.
if G (0) = G (1) and G (0) = G (2) and G (0) = G (3) then
-- But they are the same: no need to choose!
Rsel := G (0);
else
Sub_Sel := Build_Extract (Ctxt,
Sel, Width (2 * (I - 1)), 2);
Set_Location (Sub_Sel, Sel_Loc);
Rsel := Build_Mux4 (Ctxt,
Sub_Sel, G (0), G (1), G (2), G (3));
Set_Location (Rsel, Sel_Loc);
end if;
else
for K in 0 .. 1 loop
if G (2 * K) /= No_Net and G (2 * K + 1) /= No_Net then
G (K) := Build_Mux2
(Ctxt,
Build_Extract_Bit
(Ctxt, Sel, Width (2 * (I - 1))),
G (2 * K), G (2 * K + 1));
Set_Location (G (K), Sel_Loc);
else
if G (2 * K) /= No_Net then
G (K) := G (2 * K);
else
G (K) := G (2 * K + 1);
end if;
end if;
end loop;
if G (0) /= No_Net and G (1) /= No_Net then
Rsel := Build_Mux2
(Ctxt,
Build_Extract_Bit (Ctxt, Sel,
Width (2 * (I - 1) + 1)),
G (0), G (1));
Set_Location (Rsel, Sel_Loc);
else
if G (0) /= No_Net then
Rsel := G (0);
else
Rsel := G (1);
end if;
end if;
end if;
Els (Oels) := (Sel => S_Group, Val => Rsel);
Oels := Oels + 1;
end;
end loop;
Lels := Oels - 1;
end loop;
-- If the width is not a multiple of 2, handle the last level.
if Wd mod 2 = 1 then
if Wd = 1 then
Sub_Sel := Sel;
else
Sub_Sel := Build_Extract_Bit (Ctxt, Sel, Wd - 1);
Set_Location (Sub_Sel, Sel_Loc);
end if;
Iels := Els'First;
Oels := Els'First;
while Iels <= Lels loop
declare
type Net2 is array (0 .. 1) of Net;
G : Net2;
S_Group : constant Uns64 := Els (Iels).Sel and Mask;
S_El : Uns64;
El_Idx : Natural;
Rsel : Net;
begin
G := (others => Default);
for K in 0 .. 1 loop
exit when Iels > Lels;
S_El := Els (Iels).Sel;
El_Idx := Natural
(Shift_Right (S_El, Natural (Wd - 1)) and 1);
G (El_Idx) := Els (Iels).Val;
Iels := Iels + 1;
end loop;
Rsel := Build_Mux2 (Ctxt, Sub_Sel, G (0), G (1));
Set_Location (Rsel, Sel_Loc);
Els (Oels) := (Sel => S_Group, Val => Rsel);
Oels := Oels + 1;
end;
end loop;
Lels := Oels - 1;
end if;
pragma Assert (Lels = Els'First);
Res := Els (Els'First).Val;
end Synth_Case;
end Netlists.Butils;
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