several major fixes surrounding packed arrays

- entirely new PackedArray conversion (always flattens)
- typedef and struct correctly order packed ranges when combining types
- Stmt LHS traversal no longer traverses nested statements to avoid double conversion
- Logic conversion applies to `initial` blocks`
- new and modified tests to cover these cases

src/Convert/Logic.hs

@@ -57,7 +57,7 @@ convertDescription orig =
 
 regIdents :: ModuleItem -> Writer RegIdents ()
 regIdents (AlwaysC _ stmt) =
-    collectStmtLHSsM (collectNestedLHSsM idents) $
+    collectNestedStmtsM (collectStmtLHSsM (collectNestedLHSsM idents)) $
     traverseNestedStmts removeTimings stmt
     where
         idents :: LHS -> Writer RegIdents ()
@@ -66,4 +66,6 @@ regIdents (AlwaysC _ stmt) =
         removeTimings :: Stmt -> Stmt
         removeTimings (Timing _ s) = s
         removeTimings other = other
+regIdents (Initial stmt) =
+    regIdents $ AlwaysC Always stmt
 regIdents _ = return ()

src/Convert/Struct.hs

@@ -101,7 +101,7 @@ convertType :: Structs -> Type -> Type
 convertType structs t1 =
     case Map.lookup tf1 structs of
         Nothing -> t1
-        Just (t2, _) -> tf2 (rs2 ++ rs1)
+        Just (t2, _) -> tf2 (rs1 ++ rs2)
             where (tf2, rs2) = typeRanges t2
     where (tf1, rs1) = typeRanges t1
 
@@ -141,30 +141,46 @@ convertAsgn structs types (lhs, expr) =
                 Nothing -> (Implicit Unspecified [], LHSIdent x)
                 Just t -> (t, LHSIdent x)
         convertLHS (LHSBit l e) =
-            if null rs
-                then (Implicit Unspecified [], LHSBit l' e')
-                else (tf $ tail rs, LHSBit l' e')
+            case l' of
+                LHSRange lInner NonIndexed (_, loI) ->
+                    (t', LHSBit lInner (simplify $ BinOp Add loI e'))
+                LHSRange lInner IndexedPlus (baseI, _) ->
+                    (t', LHSBit lInner (simplify $ BinOp Add baseI e'))
+                _ -> (t', LHSBit l' e')
             where
                 (t, l') = convertLHS l
-                (tf, rs) = typeRanges t
+                t' = case typeRanges t of
+                    (_, []) -> Implicit Unspecified []
+                    (tf, rs) -> tf $ tail rs
                 e' = snd $ convertSubExpr e
-        convertLHS (LHSRange l m rOuterOrig) =
-            case l' of
+        convertLHS (LHSRange lOuter NonIndexed rOuterOrig) =
+            case lOuter' of
                 LHSRange lInner NonIndexed (_, loI) ->
-                    (t, LHSRange lInner m (simplify hi, simplify lo))
+                    (t, LHSRange lInner NonIndexed (simplify hi, simplify lo))
                     where
                         lo = BinOp Add loI loO
                         hi = BinOp Add loI hiO
-                _ -> if null rs
-                        then (Implicit Unspecified [], LHSRange l' m rOuter)
-                        else (tf rs', LHSRange l' m rOuter)
+                LHSRange lInner IndexedPlus (baseI, _) ->
+                    (t, LHSRange lInner IndexedPlus (simplify base, simplify len))
+                    where
+                        base = BinOp Add baseI loO
+                        len = rangeSize rOuter
+                _ -> (t, LHSRange lOuter' NonIndexed rOuter)
             where
-                (t, l') = convertLHS l
-                (tf, rs) = typeRanges t
                 hiO = snd $ convertSubExpr $ fst rOuterOrig
                 loO = snd $ convertSubExpr $ snd rOuterOrig
                 rOuter = (hiO, loO)
-                rs' = rOuter : tail rs
+                (t, lOuter') = convertLHS lOuter
+        convertLHS (LHSRange l m r) =
+            (t', LHSRange l' m r')
+            where
+                hi = snd $ convertSubExpr $ fst r
+                lo = snd $ convertSubExpr $ snd r
+                r' = (hi, lo)
+                (t, l') = convertLHS l
+                t' = case typeRanges t of
+                    (_, []) -> Implicit Unspecified []
+                    (tf, rs) -> tf $ tail rs
         convertLHS (LHSDot    l x ) =
             case t of
                 InterfaceT _ _ _ -> (Implicit Unspecified [], LHSDot l' x)
@@ -236,18 +252,30 @@ convertAsgn structs types (lhs, expr) =
                 structTf = Struct p fields
                 fieldType = lookupFieldType fields x
                 r = lookupUnstructRange structTf x
-        convertSubExpr (Range eOuter m (rOuter @ (hiO, loO))) =
+        convertSubExpr (Range eOuter NonIndexed (rOuter @ (hiO, loO))) =
             -- VCS doesn't allow ranges to be cascaded, so we need to combine
             -- nested Ranges into a single range. My understanding of the
             -- semantics are that a range returns a new, zero-indexed sub-range.
             case eOuter' of
                 Range eInner NonIndexed (_, loI) ->
-                    (t, Range eInner m (simplify hi, simplify lo))
+                    (t, Range eInner NonIndexed (simplify hi, simplify lo))
                     where
                         lo = BinOp Add loI loO
                         hi = BinOp Add loI hiO
-                _ -> (t, Range eOuter' m rOuter)
+                Range eInner IndexedPlus (baseI, _) ->
+                    (t, Range eInner IndexedPlus (simplify base, simplify len))
+                    where
+                        base = BinOp Add baseI loO
+                        len = rangeSize rOuter
+                _ -> (t, Range eOuter' NonIndexed rOuter)
             where (t, eOuter') = convertSubExpr eOuter
+        convertSubExpr (Range e m r) =
+            (t', Range e' m r)
+            where
+                (t, e') = convertSubExpr e
+                t' = case typeRanges t of
+                    (_, []) -> Implicit Unspecified []
+                    (tf, rs) -> tf $ tail rs
         convertSubExpr (Concat exprs) =
             (Implicit Unspecified [], Concat $ map (snd . convertSubExpr) exprs)
         convertSubExpr (BinOp op e1 e2) =
@@ -259,6 +287,8 @@ convertAsgn structs types (lhs, expr) =
             case e' of
                 Range eInner NonIndexed (_, loI) ->
                     (t', Bit eInner (simplify $ BinOp Add loI i'))
+                Range eInner IndexedPlus (baseI, _) ->
+                    (t', Bit eInner (simplify $ BinOp Add baseI i'))
                 _ -> (t', Bit e' i')
             where
                 (t, e') = convertSubExpr e

src/Convert/Traverse.hs

@@ -60,6 +60,7 @@ module Convert.Traverse
 , traverseNestedModuleItems
 , collectNestedModuleItemsM
 , traverseNestedStmts
+, collectNestedStmtsM
 , traverseNestedExprs
 , collectNestedExprsM
 , traverseNestedLHSsM
@@ -303,7 +304,7 @@ traverseAssertionExprsM mapper = assertionMapper
             return $ Cover e' stmt
 
 traverseStmtLHSsM :: Monad m => MapperM m LHS -> MapperM m Stmt
-traverseStmtLHSsM mapper = traverseNestedStmtsM stmtMapper
+traverseStmtLHSsM mapper = stmtMapper
     where
         fullMapper = mapper
         stmtMapper (Timing (Event sense) stmt) = do
@@ -591,7 +592,7 @@ traverseLHSsM' strat mapper item =
             lhs' <- mapper lhs
             return $ NInputGate kw x lhs' exprs
         traverseModuleItemLHSsM (AssertionItem (mx, a)) = do
-            Assertion a' <- traverseStmtLHSsM mapper (Assertion a)
+            Assertion a' <- traverseNestedStmtsM (traverseStmtLHSsM mapper) (Assertion a)
             return $ AssertionItem (mx, a')
         traverseModuleItemLHSsM other = return other
 
@@ -610,7 +611,7 @@ collectLHSsM = collectLHSsM' IncludeTFs
 traverseNestedLHSsM :: Monad m => MapperM m LHS -> MapperM m LHS
 traverseNestedLHSsM mapper = fullMapper
     where
-        fullMapper lhs = tl lhs >>= mapper
+        fullMapper lhs = mapper lhs >>= tl
         tl (LHSIdent  x    ) = return $ LHSIdent x
         tl (LHSBit    l e  ) = fullMapper l >>= \l' -> return $ LHSBit    l' e
         tl (LHSRange  l m r) = fullMapper l >>= \l' -> return $ LHSRange  l' m r
@@ -792,6 +793,8 @@ collectNestedModuleItemsM = collectify traverseNestedModuleItemsM
 
 traverseNestedStmts :: Mapper Stmt -> Mapper Stmt
 traverseNestedStmts = unmonad traverseNestedStmtsM
+collectNestedStmtsM :: Monad m => CollectorM m Stmt -> CollectorM m Stmt
+collectNestedStmtsM = collectify traverseNestedStmtsM
 
 traverseNestedExprs :: Mapper Expr -> Mapper Expr
 traverseNestedExprs = unmonad traverseNestedExprsM

src/Convert/Typedef.hs

@@ -72,12 +72,12 @@ resolveType types (Alias st rs1) =
     if Map.notMember st types
     then InterfaceT st Nothing rs1
     else case resolveType types $ types Map.! st of
-        (Net           kw    rs2) -> Net           kw    $ rs2 ++ rs1
-        (Implicit         sg rs2) -> Implicit         sg $ rs2 ++ rs1
-        (IntegerVector kw sg rs2) -> IntegerVector kw sg $ rs2 ++ rs1
-        (Enum t v rs2) -> Enum t v $ rs2 ++ rs1
-        (Struct p l rs2) -> Struct p l $ rs2 ++ rs1
-        (InterfaceT x my rs2) -> InterfaceT x my $ rs2 ++ rs1
+        (Net           kw    rs2) -> Net           kw    $ rs1 ++ rs2
+        (Implicit         sg rs2) -> Implicit         sg $ rs1 ++ rs2
+        (IntegerVector kw sg rs2) -> IntegerVector kw sg $ rs1 ++ rs2
+        (Enum            t v rs2) -> Enum            t v $ rs1 ++ rs2
+        (Struct          p l rs2) -> Struct          p l $ rs1 ++ rs2
+        (InterfaceT     x my rs2) -> InterfaceT     x my $ rs1 ++ rs2
         (IntegerAtom   kw _ ) -> error $ "resolveType encountered packed `" ++ (show kw) ++ "` on " ++ st
         (NonInteger    kw   ) -> error $ "resolveType encountered packed `" ++ (show kw) ++ "` on " ++ st
         (Alias    _ _) -> error $ "resolveType invariant failed on " ++ st

src/Language/SystemVerilog/AST/Expr.hs

@@ -145,7 +145,10 @@ simplify other = other
 
 rangeSize :: Range -> Expr
 rangeSize (s, e) =
-    simplify $ BinOp Add (BinOp Sub s e) (Number "1")
+    endianCondExpr (s, e) a b
+    where
+        a = simplify $ BinOp Add (BinOp Sub s e) (Number "1")
+        b = simplify $ BinOp Add (BinOp Sub e s) (Number "1")
 
 -- chooses one or the other expression based on the endianness of the given
 -- range; [hi:lo] chooses the first expression

test/basic/flatten.sv

-`define CASE_A(name, dims) \
+`define CASE(name, dims, a, b) \
 module name(clock, in, out); \
     input wire clock, in; \
     output logic dims out; \
-    initial out[0] = 0; \
-    initial out[1] = 0; \
-    initial out[2] = 0; \
+    initial out[0+a] = 0; \
+    initial out[1+a] = 0; \
+    initial out[2+a] = 0; \
     always @(posedge clock) begin \
- \
-        out[2][4] = out[2][3]; \
-        out[2][3] = out[2][2]; \
-        out[2][2] = out[2][1]; \
-        out[2][1] = out[2][0]; \
-        out[2][0] = out[1][4]; \
- \
-        out[1][4] = out[1][3]; \
-        out[1][3] = out[1][2]; \
-        out[1][2] = out[1][1]; \
-        out[1][1] = out[1][0]; \
-        out[1][0] = out[0][4]; \
- \
-        out[0][4] = out[0][3]; \
-        out[0][3] = out[0][2]; \
-        out[0][2] = out[0][1]; \
-        out[0][1] = out[0][0]; \
-        out[0][0] = in; \
+        /*$display($time, `" name ", out[0+a][1+b+:1]);*/ \
+        /*$display($time, `" name ", out[0+a][1+b+:1]);*/ \
+        /*$display($time, `" name ", out[1+a][1+b+:1]);*/ \
+        /*$display($time, `" name ", out[1+a][1+b+:1]);*/ \
+        /*$display($time, `" name ", out[2+a][1+b+:1]);*/ \
+        /*$display($time, `" name ", out[2+a][1+b+:1]);*/ \
+ \
+        out[2+a][4+b] = out[2+a][3+b]; \
+        out[2+a][3+b] = out[2+a][2+b]; \
+        out[2+a][2+b] = out[2+a][1+b]; \
+        out[2+a][1+b] = out[2+a][0+b]; \
+        out[2+a][0+b] = out[1+a][4+b]; \
+ \
+        out[1+a][4+b] = out[1+a][3+b]; \
+        out[1+a][3+b] = out[1+a][2+b]; \
+        out[1+a][2+b] = out[1+a][1+b]; \
+        out[1+a][1+b] = out[1+a][0+b]; \
+        out[1+a][0+b] = out[0+a][4+b]; \
+ \
+        out[0+a][4+b] = out[0+a][3+b]; \
+        out[0+a][3+b] = out[0+a][2+b]; \
+        out[0+a][2+b] = out[0+a][1+b]; \
+        out[0+a][1+b] = out[0+a][0+b]; \
+        out[0+a][0+b] = in; \
  \
     end \
 endmodule
 
-`CASE_A(A1, [2:0][4:0])
-`CASE_A(A2, [0:2][0:4])
-`CASE_A(A3, [0:2][4:0])
-`CASE_A(A4, [2:0][0:4])
-
-`define CASE_B(name, dims) \
-module name(clock, in, out); \
-    input wire clock, in; \
-    output logic dims out; \
-    initial out[1] = 0; \
-    initial out[2] = 0; \
-    initial out[3] = 0; \
-    always @(posedge clock) begin \
- \
-        out[3][5] = out[3][4]; \
-        out[3][4] = out[3][3]; \
-        out[3][3] = out[3][2]; \
-        out[3][2] = out[3][1]; \
-        out[3][1] = out[2][5]; \
- \
-        out[2][5] = out[2][4]; \
-        out[2][4] = out[2][3]; \
-        out[2][3] = out[2][2]; \
-        out[2][2] = out[2][1]; \
-        out[2][1] = out[1][5]; \
- \
-        out[1][5] = out[1][4]; \
-        out[1][4] = out[1][3]; \
-        out[1][3] = out[1][2]; \
-        out[1][2] = out[1][1]; \
-        out[1][1] = in; \
- \
-    end \
-endmodule
+`CASE(A1, [2:0][4:0], 0, 0)
+`CASE(A2, [0:2][0:4], 0, 0)
+`CASE(A3, [0:2][4:0], 0, 0)
+`CASE(A4, [2:0][0:4], 0, 0)
 
-`CASE_B(B1, [3:1][5:1])
-`CASE_B(B2, [1:3][1:5])
-`CASE_B(B3, [1:3][5:1])
-`CASE_B(B4, [3:1][1:5])
+`CASE(B1, [3:1][5:1], 1, 1)
+`CASE(B2, [1:3][1:5], 1, 1)
+`CASE(B3, [1:3][5:1], 1, 1)
+`CASE(B4, [3:1][1:5], 1, 1)
 
-`define CASE_C(name, dims) \
-module name(clock, in, out); \
-    input wire clock, in; \
-    output logic dims out; \
-    initial out[2] = 0; \
-    initial out[3] = 0; \
-    initial out[4] = 0; \
-    always @(posedge clock) begin \
- \
-        out[4][6] = out[4][5]; \
-        out[4][5] = out[4][4]; \
-        out[4][4] = out[4][3]; \
-        out[4][3] = out[4][2]; \
-        out[4][2] = out[3][6]; \
- \
-        out[3][6] = out[3][5]; \
-        out[3][5] = out[3][4]; \
-        out[3][4] = out[3][3]; \
-        out[3][3] = out[3][2]; \
-        out[3][2] = out[2][6]; \
- \
-        out[2][6] = out[2][5]; \
-        out[2][5] = out[2][4]; \
-        out[2][4] = out[2][3]; \
-        out[2][3] = out[2][2]; \
-        out[2][2] = in; \
- \
-    end \
-endmodule
+`CASE(C1, [4:2][6:2], 2, 2)
+`CASE(C2, [2:4][2:6], 2, 2)
+`CASE(C3, [2:4][6:2], 2, 2)
+`CASE(C4, [4:2][2:6], 2, 2)
 
-`CASE_C(C1, [4:2][6:2])
-`CASE_C(C2, [2:4][2:6])
-`CASE_C(C3, [2:4][6:2])
-`CASE_C(C4, [4:2][2:6])
+`CASE(D1, [5:3][6:2], 3, 2)
+`CASE(D2, [3:5][2:6], 3, 2)
+`CASE(D3, [3:5][6:2], 3, 2)
+`CASE(D4, [5:3][2:6], 3, 2)

test/basic/flatten_tb.v

@@ -4,9 +4,13 @@
     tag``2 tag``two(.clock(clock), .in(in), .out(tag``two_out)); \
     tag``3 tag``thr(.clock(clock), .in(in), .out(tag``thr_out)); \
     tag``4 tag``fou(.clock(clock), .in(in), .out(tag``fou_out)); \
+    integer tag``i; \
     initial begin \
-        $monitor(`"tag", $time, ": %h %15b %15b %15b %15b", in, \
+        for (tag``i = 0; tag``i < 20; tag``i++) begin \
+            #2; \
+            $display(`"tag", $time, ": %h %15b %15b %15b %15b", in, \
                 tag``one_out, tag``two_out, tag``thr_out, tag``fou_out); \
+        end \
     end
 
 module top;
@@ -30,5 +34,6 @@ module top;
     `FOO(A)
     `FOO(B)
     `FOO(C)
+    `FOO(D)
 
 endmodule

test/basic/multipack.sv

+`define PRINT(arr, a, b) \
+    $display(arr[0+a][0+b]); \
+    $display(arr[0+a][1+b]); \
+    $display(arr[0+a][2+b]); \
+    $display(arr[1+a][0+b]); \
+    $display(arr[1+a][1+b]); \
+    $display(arr[1+a][2+b]); \
+    $display(arr[2+a][0+b]); \
+    $display(arr[2+a][1+b]); \
+    $display(arr[2+a][2+b]); \
+    $display(arr[3+a][0+b]); \
+    $display(arr[3+a][1+b]); \
+    $display(arr[3+a][2+b]); \
+    $display(arr[4+a][0+b]); \
+    $display(arr[4+a][1+b]); \
+    $display(arr[4+a][2+b]);
+
+module Example;
+
+    typedef logic [2:0] Pack;
+    Pack [4:0] arr1;
+    Pack [4:0] arr2;
+    Pack [4:0] arr3;
+    initial begin
+        arr1 = 'b100101010100100;
+        arr1[0][1] = ~arr1[0][1];
+        arr1[4][2] = ~arr1[4][2];
+        `PRINT(arr1, 0, 0)
+        arr2 = 'b100101000110101;
+        `PRINT(arr2, 0, 0)
+        arr3 = 'b100100111101010;
+        arr3[1] = arr3[2];
+        `PRINT(arr3, 0, 0)
+    end
+
+    Pack [5:1] arr4;
+    Pack [5:1] arr5;
+    Pack [5:1] arr6;
+    initial begin
+        arr4 = 'b100101010100100;
+        arr4[1][1] = ~arr4[1][1];
+        arr4[5][2] = ~arr4[5][2];
+        `PRINT(arr4, 1, 0)
+        arr5 = 'b100101000110101;
+        `PRINT(arr5, 1, 0)
+        arr6 = 'b100100111101010;
+        arr6[2] = arr6[3];
+        `PRINT(arr6, 1, 0)
+    end
+
+    Pack [1:5] arr7;
+    Pack [1:5] arr8;
+    Pack [1:5] arr9;
+    initial begin
+        arr7 = 'b100101010100100;
+        arr7[1][1] = ~arr7[1][1];
+        arr7[5][2] = ~arr7[5][2];
+        `PRINT(arr7, 1, 0)
+        arr8 = 'b100101000110101;
+        `PRINT(arr8, 1, 0)
+        arr9 = 'b100100111101010;
+        arr9[2] = arr9[3];
+        `PRINT(arr9, 1, 0)
+    end
+
+endmodule

test/basic/multipack.v

+`define PRINT(arr, a, b) \
+    $display(arr[0+a][0+b]); \
+    $display(arr[0+a][1+b]); \
+    $display(arr[0+a][2+b]); \
+    $display(arr[1+a][0+b]); \
+    $display(arr[1+a][1+b]); \
+    $display(arr[1+a][2+b]); \
+    $display(arr[2+a][0+b]); \
+    $display(arr[2+a][1+b]); \
+    $display(arr[2+a][2+b]); \
+    $display(arr[3+a][0+b]); \
+    $display(arr[3+a][1+b]); \
+    $display(arr[3+a][2+b]); \
+    $display(arr[4+a][0+b]); \
+    $display(arr[4+a][1+b]); \
+    $display(arr[4+a][2+b]);
+
+module Example;
+
+    reg [4:0][2:0] arr1;
+    reg [4:0][2:0] arr2;
+    reg [4:0][2:0] arr3;
+    initial begin
+        arr1 = 'b100101010100100;
+        arr1[0][1] = ~arr1[0][1];
+        arr1[4][2] = ~arr1[4][2];
+        `PRINT(arr1, 0, 0)
+        arr2 = 'b100101000110101;
+        `PRINT(arr2, 0, 0)
+        arr3 = 'b100100111101010;
+        arr3[1] = arr3[2];
+        `PRINT(arr3, 0, 0)
+    end
+
+    reg [5:1][2:0] arr4;
+    reg [5:1][2:0] arr5;
+    reg [5:1][2:0] arr6;
+    initial begin
+        arr4 = 'b100101010100100;
+        arr4[1][1] = ~arr4[1][1];
+        arr4[5][2] = ~arr4[5][2];
+        `PRINT(arr4, 1, 0)
+        arr5 = 'b100101000110101;
+        `PRINT(arr5, 1, 0)
+        arr6 = 'b100100111101010;
+        arr6[2] = arr6[3];
+        `PRINT(arr6, 1, 0)
+    end
+
+    reg [1:5][2:0] arr7;
+    reg [1:5][2:0] arr8;
+    reg [1:5][2:0] arr9;
+    initial begin
+        arr7 = 'b100101010100100;
+        arr7[1][1] = ~arr7[1][1];
+        arr7[5][2] = ~arr7[5][2];
+        `PRINT(arr7, 1, 0)
+        arr8 = 'b100101000110101;
+        `PRINT(arr8, 1, 0)
+        arr9 = 'b100100111101010;
+        arr9[2] = arr9[3];
+        `PRINT(arr9, 1, 0)
+    end
+
+endmodule

test/basic/multipack_tb.v

+module top;
+    Example example();
+endmodule

test/basic/struct_array.sv

+typedef struct packed {
+    logic x;
+    logic [3:0] y;
+    logic [1:0] z;
+} Struct_t;
+
+module Unpacker(in, select, a, b, c);
+    parameter WIDTH = 8;
+    input Struct_t [WIDTH-1:0] in;
+    input logic [$clog2(WIDTH)-1:0] select;
+    output logic a;
+    output logic [3:0] b;
+    output logic [1:0] c;
+    assign a = in[select].x;
+    assign b = in[select].y;
+    assign c = in[select].z;
+endmodule

test/basic/struct_array.v

+module Unpacker(in, select, a, b, c);
+    parameter WIDTH = 8;
+    input wire [WIDTH-1:0][6:0] in;
+    input wire [$clog2(WIDTH)-1:0] select;
+    output wire a;
+    output wire [3:0] b;
+    output wire [1:0] c;
+    wire [6:0] p;
+    assign p = in[select];
+    assign a = p[6:6];
+    assign b = p[5:2];
+    assign c = p[1:0];
+endmodule

test/basic/struct_array_tb.v

+module top;
+    reg [56-1:0] in;
+    reg [2:0] select;
+
+    wire a;
+    wire [3:0] b;
+    wire [1:0] c;
+
+    Unpacker unpacker(in, select, a, b, c);
+
+    initial begin
+        $monitor("%d: %01b %04b %02b", select, a, b, c);
+        in = 'b01111011011011101111100111110111001010001011100110101000;
+        select = 0; #1;
+        select = 1; #1;
+        select = 2; #1;
+        select = 3; #1;
+        select = 4; #1;
+        select = 5; #1;
+        select = 6; #1;
+        select = 7; #1;
+        $finish;
+    end
+
+    // 0 1010 00
+    // 1 1100 11
+    // 0 1000 10
+    // 0 1110 01
+    // 0 0111 11
+    // 1 0111 11
+    // 1 0110 11
+    // 0 1111 01
+
+endmodule