vhdl: add anonymous_signal_declaration.

18 files changed, 384 insertions, 186 deletions

diff --git a/src/vhdl/translate/trans-chap4.adb b/src/vhdl/translate/trans-chap4.adb
index 419229e66..13688263c 100644
--- a/src/vhdl/translate/trans-chap4.adb
+++ b/src/vhdl/translate/trans-chap4.adb
@@ -229,7 +229,8 @@ package body Trans.Chap4 is
          when Iir_Kind_Signal_Declaration
             | Iir_Kind_Interface_Signal_Declaration =>
             Rtis.Generate_Signal_Rti (Decl);
-         when Iir_Kind_Guard_Signal_Declaration =>
+         when Iir_Kind_Guard_Signal_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             --  No name created for guard signal.
             null;
          when others =>
@@ -1820,7 +1821,8 @@ package body Trans.Chap4 is
             | Iir_Kind_Constant_Declaration =>
             Create_Object (Decl);
 
-         when Iir_Kind_Signal_Declaration =>
+         when Iir_Kind_Signal_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             Create_Signal (Decl);
 
          when Iir_Kind_Object_Alias_Declaration =>
@@ -2584,7 +2586,8 @@ package body Trans.Chap4 is
                   Need_Final := True;
                end if;
 
-            when Iir_Kind_Signal_Declaration =>
+            when Iir_Kind_Signal_Declaration
+              | Iir_Kind_Anonymous_Signal_Declaration =>
                Elab_Signal_Declaration (Decl, Parent, False);
 
             when Iir_Kind_Object_Alias_Declaration =>
diff --git a/src/vhdl/translate/trans-chap5.adb b/src/vhdl/translate/trans-chap5.adb
index 2aa7cfdea..3df3a7324 100644
--- a/src/vhdl/translate/trans-chap5.adb
+++ b/src/vhdl/translate/trans-chap5.adb
@@ -448,7 +448,13 @@ package body Trans.Chap5 is
             --  actual, but the type of the formal may be used by the actual.
             Set_Map_Env (Formal_Env);
             Chap6.Translate_Signal_Name (Formal, Formal_Sig, Formal_Val);
-            Actual_En := Chap7.Translate_Expression (Actual, Formal_Type);
+            if Get_Kind (Actual) = Iir_Kind_Reference_Name then
+               --  For vhdl08 association by expression.
+               Actual_En := Chap7.Translate_Expression
+                 (Get_Referenced_Name (Actual), Formal_Type);
+            else
+               Actual_En := Chap7.Translate_Expression (Actual, Formal_Type);
+            end if;
             Actual_Sig := E2M (Actual_En, Get_Info (Formal_Type), Mode_Value);
             Mode := Connect_Value;
 --            raise Internal_Error;
diff --git a/src/vhdl/translate/trans-chap6.adb b/src/vhdl/translate/trans-chap6.adb
index a277d452b..eb757d9c7 100644
--- a/src/vhdl/translate/trans-chap6.adb
+++ b/src/vhdl/translate/trans-chap6.adb
@@ -1071,7 +1071,8 @@ package body Trans.Chap6 is
            | Iir_Kind_Quiet_Attribute
            | Iir_Kind_Delayed_Attribute
            | Iir_Kind_Transaction_Attribute
-           | Iir_Kind_Guard_Signal_Declaration =>
+           | Iir_Kind_Guard_Signal_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             if Mode = Mode_Signal then
                return Get_Var (Name_Info.Signal_Sig, Type_Info, Mode_Signal);
             else
@@ -1180,7 +1181,8 @@ package body Trans.Chap6 is
            | Iir_Kind_Delayed_Attribute
            | Iir_Kind_Transaction_Attribute
            | Iir_Kind_Guard_Signal_Declaration
-           | Iir_Kind_Object_Alias_Declaration =>
+           | Iir_Kind_Object_Alias_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             Translate_Signal_Base (Name, Sig, Drv);
          when Iir_Kind_Slice_Name =>
             declare
@@ -1231,7 +1233,8 @@ package body Trans.Chap6 is
    begin
       case Get_Kind (Name) is
          when Iir_Kind_Signal_Declaration
-           | Iir_Kind_Interface_Signal_Declaration =>
+           | Iir_Kind_Interface_Signal_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             declare
                Name_Type : constant Iir := Get_Type (Name);
                Name_Info : constant Ortho_Info_Acc := Get_Info (Name);
@@ -1290,7 +1293,8 @@ package body Trans.Chap6 is
            | Iir_Kind_Quiet_Attribute
            | Iir_Kind_Delayed_Attribute
            | Iir_Kind_Transaction_Attribute
-           | Iir_Kind_Guard_Signal_Declaration =>
+           | Iir_Kind_Guard_Signal_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             Sig := Get_Var (Name_Info.Signal_Sig, Type_Info, Mode_Signal);
             Val := Get_Var (Name_Info.Signal_Val, Type_Info, Mode_Value);
          when Iir_Kind_Interface_Signal_Declaration =>
diff --git a/src/vhdl/translate/trans-chap7.adb b/src/vhdl/translate/trans-chap7.adb
index 3d670cf56..4d6f68fdc 100644
--- a/src/vhdl/translate/trans-chap7.adb
+++ b/src/vhdl/translate/trans-chap7.adb
@@ -4330,6 +4330,7 @@ package body Trans.Chap7 is
             | Iir_Kind_Delayed_Attribute
             | Iir_Kind_Transaction_Attribute
             | Iir_Kind_Guard_Signal_Declaration
+            | Iir_Kind_Anonymous_Signal_Declaration
             | Iir_Kind_Attribute_Value
             | Iir_Kind_Attribute_Name =>
             Res := M2E (Chap6.Translate_Name (Expr, Mode_Value));
diff --git a/src/vhdl/translate/trans-rtis.adb b/src/vhdl/translate/trans-rtis.adb
index 759a066cb..e59a12b92 100644
--- a/src/vhdl/translate/trans-rtis.adb
+++ b/src/vhdl/translate/trans-rtis.adb
@@ -1933,7 +1933,8 @@ package body Trans.Rtis is
          Start_Record_Aggr (List, Ghdl_Rtin_Object);
          Mode := 0;
          case Get_Kind (Decl) is
-            when Iir_Kind_Signal_Declaration =>
+            when Iir_Kind_Signal_Declaration
+              | Iir_Kind_Anonymous_Signal_Declaration =>
                Comm := Ghdl_Rtik_Signal;
                Var := Info.Signal_Sig;
             when Iir_Kind_Interface_Signal_Declaration =>
@@ -2140,7 +2141,8 @@ package body Trans.Rtis is
               | Iir_Kind_Interface_Constant_Declaration
               | Iir_Kind_Variable_Declaration
               | Iir_Kind_File_Declaration
-              | Iir_Kind_Signal_Attribute_Declaration =>
+              | Iir_Kind_Signal_Attribute_Declaration
+              | Iir_Kind_Anonymous_Signal_Declaration =>
                null;
             when Iir_Kind_Object_Alias_Declaration
                | Iir_Kind_Attribute_Declaration =>
@@ -2270,7 +2272,8 @@ package body Trans.Rtis is
                   Add_Rti_Node (Info.Object_Rti);
                end;
             when Iir_Kind_Signal_Declaration
-               | Iir_Kind_Interface_Signal_Declaration =>
+              | Iir_Kind_Interface_Signal_Declaration
+              | Iir_Kind_Anonymous_Signal_Declaration =>
                declare
                   Info : constant Signal_Info_Acc := Get_Info (Decl);
                begin
diff --git a/src/vhdl/vhdl-canon.adb b/src/vhdl/vhdl-canon.adb
index 604272813..5e1011a36 100644
--- a/src/vhdl/vhdl-canon.adb
+++ b/src/vhdl/vhdl-canon.adb
@@ -40,13 +40,11 @@ package body Vhdl.Canon is
    --  Canonicalize the chain of declarations in Declaration_Chain of
    --  DECL_PARENT. PARENT must be the parent of the current statements chain,
    --  or NULL_IIR if DECL_PARENT has no corresponding current statments.
+   --  TOP is used to add dependencies (from binding indications).
    procedure Canon_Declarations (Top : Iir_Design_Unit;
                                  Decl_Parent : Iir;
                                  Parent : Iir);
-   function Canon_Declaration (Top : Iir_Design_Unit;
-                               Decl : Iir;
-                               Parent : Iir;
-                               Decl_Parent : Iir)
+   function Canon_Declaration (Top : Iir_Design_Unit; Decl : Iir; Parent : Iir)
                               return Iir;
 
    procedure Canon_Concurrent_Stmts (Top : Iir_Design_Unit; Parent : Iir);
@@ -2101,8 +2099,7 @@ package body Vhdl.Canon is
                   Decl : constant Iir := Get_Parameter_Specification (El);
                   New_Decl : Iir;
                begin
-                  New_Decl := Canon_Declaration
-                    (Top, Decl, Null_Iir, Null_Iir);
+                  New_Decl := Canon_Declaration (Top, Decl, Null_Iir);
                   pragma Assert (New_Decl = Decl);
 
                   Canon_Generate_Statement_Body
@@ -2245,6 +2242,7 @@ package body Vhdl.Canon is
    end Add_Binding_Indication_Dependence;
 
    --  Canon the component_configuration or configuration_specification CFG.
+   --  TOP is used to add dependences.
    procedure Canon_Component_Configuration (Top : Iir_Design_Unit; Cfg : Iir)
    is
       --  True iff CFG is a component_configuration.
@@ -2622,7 +2620,7 @@ package body Vhdl.Canon is
 
    --  Replace ALL/OTHERS with the explicit list of signals.
    procedure Canon_Disconnection_Specification
-     (Dis : Iir_Disconnection_Specification; Decl_Parent : Iir)
+     (Dis : Iir_Disconnection_Specification)
    is
       Signal_List : Iir_Flist;
       Force : Boolean;
@@ -2648,7 +2646,7 @@ package body Vhdl.Canon is
          Dis_Type := Get_Type (Get_Type_Mark (Dis));
          N_List := Create_Iir_List;
          Set_Is_Ref (Dis, True);
-         El := Get_Declaration_Chain (Decl_Parent);
+         El := Get_Declaration_Chain (Get_Parent (Dis));
          while El /= Null_Iir loop
             if Get_Kind (El) = Iir_Kind_Signal_Declaration
               and then Get_Type (El) = Dis_Type
@@ -2739,9 +2737,8 @@ package body Vhdl.Canon is
       return Decl;
    end Canon_Package_Instantiation_Declaration;
 
-   function Canon_Declaration
-     (Top : Iir_Design_Unit; Decl : Iir; Parent : Iir; Decl_Parent : Iir)
-     return Iir
+   function Canon_Declaration (Top : Iir_Design_Unit; Decl : Iir; Parent : Iir)
+                              return Iir
    is
       Stmts : Iir;
    begin
@@ -2784,6 +2781,38 @@ package body Vhdl.Canon is
                Canon_Expression (Get_Default_Value (Decl));
             end if;
 
+         when Iir_Kind_Anonymous_Signal_Declaration =>
+            if Canon_Flag_Expressions then
+               Canon_Expression (Get_Expression (Decl));
+            end if;
+            --  Create a signal assignment.
+            declare
+               Parent : constant Node := Get_Parent (Decl);
+               Asgn : Iir;
+               We : Iir;
+               Name : Iir;
+            begin
+               Asgn := Create_Iir
+                 (Iir_Kind_Concurrent_Simple_Signal_Assignment);
+               Location_Copy (Asgn, Decl);
+               Set_Parent (Asgn, Parent);
+               Name := Build_Simple_Name (Decl, Decl);
+               Set_Type (Name, Get_Type (Decl));
+               Set_Target (Asgn, Name);
+               Set_Delay_Mechanism (Asgn, Iir_Inertial_Delay);
+
+               We := Create_Iir (Iir_Kind_Waveform_Element);
+               Location_Copy (We, Decl);
+               Set_We_Value (We, Get_Expression (Decl));
+               Set_Expression (Decl, Null_Iir);
+
+               Set_Waveform_Chain (Asgn, We);
+
+               --  Prepend.
+               Set_Chain (Asgn, Get_Concurrent_Statement_Chain (Parent));
+               Set_Concurrent_Statement_Chain (Parent, Asgn);
+            end;
+
          when Iir_Kind_Iterator_Declaration =>
             null;
 
@@ -2803,7 +2832,7 @@ package body Vhdl.Canon is
                Canon_Expression (Get_Expression (Decl));
             end if;
          when Iir_Kind_Disconnection_Specification =>
-            Canon_Disconnection_Specification (Decl, Decl_Parent);
+            Canon_Disconnection_Specification (Decl);
 
          when Iir_Kind_Group_Template_Declaration =>
             null;
@@ -2856,15 +2885,34 @@ package body Vhdl.Canon is
       Decl : Iir;
       Prev_Decl : Iir;
       New_Decl : Iir;
+      Anon_Label : Natural;
    begin
       if Parent /= Null_Iir then
          Clear_Instantiation_Configuration (Parent, True);
       end if;
 
+      Anon_Label := 0;
+
       Decl := Get_Declaration_Chain (Decl_Parent);
       Prev_Decl := Null_Iir;
       while Decl /= Null_Iir loop
-         New_Decl := Canon_Declaration (Top, Decl, Parent, Decl_Parent);
+         --  Give a name to anonymous signals.
+         --  Ideally it should be done in Canon_Declaration, but we need
+         --  a counter for all the declarations.
+         if Get_Kind (Decl) = Iir_Kind_Anonymous_Signal_Declaration then
+            declare
+               Str : String := "ANONYMOUS" & Natural'Image (Anon_Label);
+            begin
+               --  Note: the label starts with a capitalized
+               --  letter, to avoid any clash with user's
+               --  identifiers.
+               Str (10) := '_';
+               Set_Identifier (Decl, Name_Table.Get_Identifier (Str));
+               Anon_Label := Anon_Label + 1;
+            end;
+         end if;
+
+         New_Decl := Canon_Declaration (Top, Decl, Parent);
 
          if New_Decl /= Decl then
             --  Replace declaration
diff --git a/src/vhdl/vhdl-elocations.adb b/src/vhdl/vhdl-elocations.adb
index 8bc68245c..c08519076 100644
--- a/src/vhdl/vhdl-elocations.adb
+++ b/src/vhdl/vhdl-elocations.adb
@@ -282,6 +282,7 @@ package body Vhdl.Elocations is
            | Iir_Kind_Guard_Signal_Declaration
            | Iir_Kind_Interface_Function_Declaration
            | Iir_Kind_Interface_Procedure_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Signal_Attribute_Declaration
            | Iir_Kind_Identity_Operator
            | Iir_Kind_Negation_Operator
diff --git a/src/vhdl/vhdl-elocations.ads b/src/vhdl/vhdl-elocations.ads
index fa895e111..643746527 100644
--- a/src/vhdl/vhdl-elocations.ads
+++ b/src/vhdl/vhdl-elocations.ads
@@ -259,6 +259,8 @@ package Vhdl.Elocations is
 
    -- Iir_Kind_Guard_Signal_Declaration (None)
 
+   -- Iir_Kind_Anonymous_Signal_Declaration (None)
+
    -- Iir_Kind_Signal_Attribute_Declaration (None)
 
    -- Iir_Kind_Constant_Declaration (L1)
diff --git a/src/vhdl/vhdl-errors.adb b/src/vhdl/vhdl-errors.adb
index 1bed01213..db2f87601 100644
--- a/src/vhdl/vhdl-errors.adb
+++ b/src/vhdl/vhdl-errors.adb
@@ -455,6 +455,9 @@ package body Vhdl.Errors is
          when Iir_Kind_Signal_Attribute_Declaration =>
             --  Should not appear.
             return "signal attribute";
+         when Iir_Kind_Anonymous_Signal_Declaration =>
+            --  Should not appear.
+            return "anonymous signal";
          when Iir_Kind_Group_Template_Declaration =>
             return Disp_Identifier (Node, "group template");
          when Iir_Kind_Group_Declaration =>
diff --git a/src/vhdl/vhdl-nodes.adb b/src/vhdl/vhdl-nodes.adb
index 85755105e..ae1c2bcb0 100644
--- a/src/vhdl/vhdl-nodes.adb
+++ b/src/vhdl/vhdl-nodes.adb
@@ -1059,6 +1059,7 @@ package body Vhdl.Nodes is
            | Iir_Kind_Interface_Signal_Declaration
            | Iir_Kind_Interface_File_Declaration
            | Iir_Kind_Interface_Type_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Signal_Attribute_Declaration
            | Iir_Kind_Identity_Operator
            | Iir_Kind_Negation_Operator
diff --git a/src/vhdl/vhdl-nodes.ads b/src/vhdl/vhdl-nodes.ads
index ec354499d..26d9601f8 100644
--- a/src/vhdl/vhdl-nodes.ads
+++ b/src/vhdl/vhdl-nodes.ads
@@ -1625,6 +1625,29 @@ package Vhdl.Nodes is
    --
    --   Get/Set_Name_Staticness (State2)
 
+   -- Iir_Kind_Anonymous_Signal_Declaration (Short)
+   --
+   --  Anonymous signal created for vhdl 2008 port association with a non
+   --  globally static expression.
+   --
+   --   Get/Set_Parent (Field0)
+   --
+   --   Get/Set_Chain (Field2)
+   --
+   --   Get/Set_Identifier (Field3)
+   --
+   --  Must be Null.
+   --   Get/Set_Default_Value (Field4)
+   --
+   --  The expression that is assigned to the signal.
+   --   Get/Set_Expression (Field5)
+   --
+   --   Get/Set_Type (Field1)
+   --
+   --   Get/Set_After_Drivers_Flag (Flag5)
+   --
+   --   Get/Set_Is_Ref (Flag12)
+
    -- Iir_Kind_Signal_Attribute_Declaration (Short)
    --
    --  Chain of implicit signals created from signal attribute.  This is just
@@ -3701,6 +3724,8 @@ package Vhdl.Nodes is
    --  This doesn't correspond to a name in the sources.  This is an artificial
    --  name in the tree which is owned and reference another name.
    --
+   --   Get/Set_Type (Field1)
+   --
    --   Get/Set_Named_Entity (Field4)
    --
    --  The name from which the reference was created.  Can be Null_Iir if the
@@ -4237,6 +4262,7 @@ package Vhdl.Nodes is
       Iir_Kind_Interface_Function_Declaration, --         interface
       Iir_Kind_Interface_Procedure_Declaration, --        interface
 
+      Iir_Kind_Anonymous_Signal_Declaration,
       Iir_Kind_Signal_Attribute_Declaration,
 
    -- Expressions.
diff --git a/src/vhdl/vhdl-nodes_meta.adb b/src/vhdl/vhdl-nodes_meta.adb
index 5c55f608a..eea011a3f 100644
--- a/src/vhdl/vhdl-nodes_meta.adb
+++ b/src/vhdl/vhdl-nodes_meta.adb
@@ -1256,6 +1256,8 @@ package body Vhdl.Nodes_Meta is
             return "interface_function_declaration";
          when Iir_Kind_Interface_Procedure_Declaration =>
             return "interface_procedure_declaration";
+         when Iir_Kind_Anonymous_Signal_Declaration =>
+            return "anonymous_signal_declaration";
          when Iir_Kind_Signal_Attribute_Declaration =>
             return "signal_attribute_declaration";
          when Iir_Kind_Identity_Operator =>
@@ -3344,6 +3346,15 @@ package body Vhdl.Nodes_Meta is
       Field_Chain,
       Field_Interface_Declaration_Chain,
       Field_Return_Type_Mark,
+      --  Iir_Kind_Anonymous_Signal_Declaration
+      Field_Identifier,
+      Field_Is_Ref,
+      Field_After_Drivers_Flag,
+      Field_Parent,
+      Field_Chain,
+      Field_Default_Value,
+      Field_Expression,
+      Field_Type,
       --  Iir_Kind_Signal_Attribute_Declaration
       Field_Parent,
       Field_Chain,
@@ -4094,6 +4105,7 @@ package body Vhdl.Nodes_Meta is
       Field_Base_Name,
       --  Iir_Kind_Reference_Name
       Field_Is_Forward_Ref,
+      Field_Type,
       Field_Named_Entity,
       Field_Referenced_Name,
       --  Iir_Kind_External_Constant_Name
@@ -4548,155 +4560,156 @@ package body Vhdl.Nodes_Meta is
       Iir_Kind_Interface_Package_Declaration => 974,
       Iir_Kind_Interface_Function_Declaration => 991,
       Iir_Kind_Interface_Procedure_Declaration => 1004,
-      Iir_Kind_Signal_Attribute_Declaration => 1007,
-      Iir_Kind_Identity_Operator => 1011,
-      Iir_Kind_Negation_Operator => 1015,
-      Iir_Kind_Absolute_Operator => 1019,
-      Iir_Kind_Not_Operator => 1023,
-      Iir_Kind_Implicit_Condition_Operator => 1027,
-      Iir_Kind_Condition_Operator => 1031,
-      Iir_Kind_Reduction_And_Operator => 1035,
-      Iir_Kind_Reduction_Or_Operator => 1039,
-      Iir_Kind_Reduction_Nand_Operator => 1043,
-      Iir_Kind_Reduction_Nor_Operator => 1047,
-      Iir_Kind_Reduction_Xor_Operator => 1051,
-      Iir_Kind_Reduction_Xnor_Operator => 1055,
-      Iir_Kind_And_Operator => 1060,
-      Iir_Kind_Or_Operator => 1065,
-      Iir_Kind_Nand_Operator => 1070,
-      Iir_Kind_Nor_Operator => 1075,
-      Iir_Kind_Xor_Operator => 1080,
-      Iir_Kind_Xnor_Operator => 1085,
-      Iir_Kind_Equality_Operator => 1090,
-      Iir_Kind_Inequality_Operator => 1095,
-      Iir_Kind_Less_Than_Operator => 1100,
-      Iir_Kind_Less_Than_Or_Equal_Operator => 1105,
-      Iir_Kind_Greater_Than_Operator => 1110,
-      Iir_Kind_Greater_Than_Or_Equal_Operator => 1115,
-      Iir_Kind_Match_Equality_Operator => 1120,
-      Iir_Kind_Match_Inequality_Operator => 1125,
-      Iir_Kind_Match_Less_Than_Operator => 1130,
-      Iir_Kind_Match_Less_Than_Or_Equal_Operator => 1135,
-      Iir_Kind_Match_Greater_Than_Operator => 1140,
-      Iir_Kind_Match_Greater_Than_Or_Equal_Operator => 1145,
-      Iir_Kind_Sll_Operator => 1150,
-      Iir_Kind_Sla_Operator => 1155,
-      Iir_Kind_Srl_Operator => 1160,
-      Iir_Kind_Sra_Operator => 1165,
-      Iir_Kind_Rol_Operator => 1170,
-      Iir_Kind_Ror_Operator => 1175,
-      Iir_Kind_Addition_Operator => 1180,
-      Iir_Kind_Substraction_Operator => 1185,
-      Iir_Kind_Concatenation_Operator => 1190,
-      Iir_Kind_Multiplication_Operator => 1195,
-      Iir_Kind_Division_Operator => 1200,
-      Iir_Kind_Modulus_Operator => 1205,
-      Iir_Kind_Remainder_Operator => 1210,
-      Iir_Kind_Exponentiation_Operator => 1215,
-      Iir_Kind_Function_Call => 1223,
-      Iir_Kind_Aggregate => 1230,
-      Iir_Kind_Parenthesis_Expression => 1233,
-      Iir_Kind_Qualified_Expression => 1237,
-      Iir_Kind_Type_Conversion => 1242,
-      Iir_Kind_Allocator_By_Expression => 1246,
-      Iir_Kind_Allocator_By_Subtype => 1251,
-      Iir_Kind_Selected_Element => 1259,
-      Iir_Kind_Dereference => 1264,
-      Iir_Kind_Implicit_Dereference => 1269,
-      Iir_Kind_Slice_Name => 1276,
-      Iir_Kind_Indexed_Name => 1282,
-      Iir_Kind_Psl_Expression => 1284,
-      Iir_Kind_Sensitized_Process_Statement => 1305,
-      Iir_Kind_Process_Statement => 1325,
-      Iir_Kind_Concurrent_Simple_Signal_Assignment => 1337,
-      Iir_Kind_Concurrent_Conditional_Signal_Assignment => 1349,
-      Iir_Kind_Concurrent_Selected_Signal_Assignment => 1362,
-      Iir_Kind_Concurrent_Assertion_Statement => 1370,
-      Iir_Kind_Concurrent_Procedure_Call_Statement => 1377,
-      Iir_Kind_Psl_Assert_Statement => 1390,
-      Iir_Kind_Psl_Cover_Statement => 1403,
-      Iir_Kind_Block_Statement => 1417,
-      Iir_Kind_If_Generate_Statement => 1428,
-      Iir_Kind_Case_Generate_Statement => 1437,
-      Iir_Kind_For_Generate_Statement => 1446,
-      Iir_Kind_Component_Instantiation_Statement => 1457,
-      Iir_Kind_Psl_Default_Clock => 1461,
-      Iir_Kind_Simple_Simultaneous_Statement => 1468,
-      Iir_Kind_Generate_Statement_Body => 1479,
-      Iir_Kind_If_Generate_Else_Clause => 1485,
-      Iir_Kind_Simple_Signal_Assignment_Statement => 1495,
-      Iir_Kind_Conditional_Signal_Assignment_Statement => 1505,
-      Iir_Kind_Selected_Waveform_Assignment_Statement => 1516,
-      Iir_Kind_Null_Statement => 1520,
-      Iir_Kind_Assertion_Statement => 1527,
-      Iir_Kind_Report_Statement => 1533,
-      Iir_Kind_Wait_Statement => 1541,
-      Iir_Kind_Variable_Assignment_Statement => 1548,
-      Iir_Kind_Conditional_Variable_Assignment_Statement => 1555,
-      Iir_Kind_Return_Statement => 1561,
-      Iir_Kind_For_Loop_Statement => 1570,
-      Iir_Kind_While_Loop_Statement => 1579,
-      Iir_Kind_Next_Statement => 1586,
-      Iir_Kind_Exit_Statement => 1593,
-      Iir_Kind_Case_Statement => 1601,
-      Iir_Kind_Procedure_Call_Statement => 1607,
-      Iir_Kind_If_Statement => 1617,
-      Iir_Kind_Elsif => 1623,
-      Iir_Kind_Character_Literal => 1631,
-      Iir_Kind_Simple_Name => 1639,
-      Iir_Kind_Selected_Name => 1648,
-      Iir_Kind_Operator_Symbol => 1654,
-      Iir_Kind_Reference_Name => 1657,
-      Iir_Kind_External_Constant_Name => 1665,
-      Iir_Kind_External_Signal_Name => 1673,
-      Iir_Kind_External_Variable_Name => 1682,
-      Iir_Kind_Selected_By_All_Name => 1688,
-      Iir_Kind_Parenthesis_Name => 1693,
-      Iir_Kind_Package_Pathname => 1697,
-      Iir_Kind_Absolute_Pathname => 1698,
-      Iir_Kind_Relative_Pathname => 1699,
-      Iir_Kind_Pathname_Element => 1704,
-      Iir_Kind_Base_Attribute => 1706,
-      Iir_Kind_Subtype_Attribute => 1711,
-      Iir_Kind_Element_Attribute => 1716,
-      Iir_Kind_Left_Type_Attribute => 1721,
-      Iir_Kind_Right_Type_Attribute => 1726,
-      Iir_Kind_High_Type_Attribute => 1731,
-      Iir_Kind_Low_Type_Attribute => 1736,
-      Iir_Kind_Ascending_Type_Attribute => 1741,
-      Iir_Kind_Image_Attribute => 1747,
-      Iir_Kind_Value_Attribute => 1753,
-      Iir_Kind_Pos_Attribute => 1759,
-      Iir_Kind_Val_Attribute => 1765,
-      Iir_Kind_Succ_Attribute => 1771,
-      Iir_Kind_Pred_Attribute => 1777,
-      Iir_Kind_Leftof_Attribute => 1783,
-      Iir_Kind_Rightof_Attribute => 1789,
-      Iir_Kind_Delayed_Attribute => 1798,
-      Iir_Kind_Stable_Attribute => 1807,
-      Iir_Kind_Quiet_Attribute => 1816,
-      Iir_Kind_Transaction_Attribute => 1825,
-      Iir_Kind_Event_Attribute => 1829,
-      Iir_Kind_Active_Attribute => 1833,
-      Iir_Kind_Last_Event_Attribute => 1837,
-      Iir_Kind_Last_Active_Attribute => 1841,
-      Iir_Kind_Last_Value_Attribute => 1845,
-      Iir_Kind_Driving_Attribute => 1849,
-      Iir_Kind_Driving_Value_Attribute => 1853,
-      Iir_Kind_Behavior_Attribute => 1853,
-      Iir_Kind_Structure_Attribute => 1853,
-      Iir_Kind_Simple_Name_Attribute => 1860,
-      Iir_Kind_Instance_Name_Attribute => 1865,
-      Iir_Kind_Path_Name_Attribute => 1870,
-      Iir_Kind_Left_Array_Attribute => 1877,
-      Iir_Kind_Right_Array_Attribute => 1884,
-      Iir_Kind_High_Array_Attribute => 1891,
-      Iir_Kind_Low_Array_Attribute => 1898,
-      Iir_Kind_Length_Array_Attribute => 1905,
-      Iir_Kind_Ascending_Array_Attribute => 1912,
-      Iir_Kind_Range_Array_Attribute => 1919,
-      Iir_Kind_Reverse_Range_Array_Attribute => 1926,
-      Iir_Kind_Attribute_Name => 1935
+      Iir_Kind_Anonymous_Signal_Declaration => 1012,
+      Iir_Kind_Signal_Attribute_Declaration => 1015,
+      Iir_Kind_Identity_Operator => 1019,
+      Iir_Kind_Negation_Operator => 1023,
+      Iir_Kind_Absolute_Operator => 1027,
+      Iir_Kind_Not_Operator => 1031,
+      Iir_Kind_Implicit_Condition_Operator => 1035,
+      Iir_Kind_Condition_Operator => 1039,
+      Iir_Kind_Reduction_And_Operator => 1043,
+      Iir_Kind_Reduction_Or_Operator => 1047,
+      Iir_Kind_Reduction_Nand_Operator => 1051,
+      Iir_Kind_Reduction_Nor_Operator => 1055,
+      Iir_Kind_Reduction_Xor_Operator => 1059,
+      Iir_Kind_Reduction_Xnor_Operator => 1063,
+      Iir_Kind_And_Operator => 1068,
+      Iir_Kind_Or_Operator => 1073,
+      Iir_Kind_Nand_Operator => 1078,
+      Iir_Kind_Nor_Operator => 1083,
+      Iir_Kind_Xor_Operator => 1088,
+      Iir_Kind_Xnor_Operator => 1093,
+      Iir_Kind_Equality_Operator => 1098,
+      Iir_Kind_Inequality_Operator => 1103,
+      Iir_Kind_Less_Than_Operator => 1108,
+      Iir_Kind_Less_Than_Or_Equal_Operator => 1113,
+      Iir_Kind_Greater_Than_Operator => 1118,
+      Iir_Kind_Greater_Than_Or_Equal_Operator => 1123,
+      Iir_Kind_Match_Equality_Operator => 1128,
+      Iir_Kind_Match_Inequality_Operator => 1133,
+      Iir_Kind_Match_Less_Than_Operator => 1138,
+      Iir_Kind_Match_Less_Than_Or_Equal_Operator => 1143,
+      Iir_Kind_Match_Greater_Than_Operator => 1148,
+      Iir_Kind_Match_Greater_Than_Or_Equal_Operator => 1153,
+      Iir_Kind_Sll_Operator => 1158,
+      Iir_Kind_Sla_Operator => 1163,
+      Iir_Kind_Srl_Operator => 1168,
+      Iir_Kind_Sra_Operator => 1173,
+      Iir_Kind_Rol_Operator => 1178,
+      Iir_Kind_Ror_Operator => 1183,
+      Iir_Kind_Addition_Operator => 1188,
+      Iir_Kind_Substraction_Operator => 1193,
+      Iir_Kind_Concatenation_Operator => 1198,
+      Iir_Kind_Multiplication_Operator => 1203,
+      Iir_Kind_Division_Operator => 1208,
+      Iir_Kind_Modulus_Operator => 1213,
+      Iir_Kind_Remainder_Operator => 1218,
+      Iir_Kind_Exponentiation_Operator => 1223,
+      Iir_Kind_Function_Call => 1231,
+      Iir_Kind_Aggregate => 1238,
+      Iir_Kind_Parenthesis_Expression => 1241,
+      Iir_Kind_Qualified_Expression => 1245,
+      Iir_Kind_Type_Conversion => 1250,
+      Iir_Kind_Allocator_By_Expression => 1254,
+      Iir_Kind_Allocator_By_Subtype => 1259,
+      Iir_Kind_Selected_Element => 1267,
+      Iir_Kind_Dereference => 1272,
+      Iir_Kind_Implicit_Dereference => 1277,
+      Iir_Kind_Slice_Name => 1284,
+      Iir_Kind_Indexed_Name => 1290,
+      Iir_Kind_Psl_Expression => 1292,
+      Iir_Kind_Sensitized_Process_Statement => 1313,
+      Iir_Kind_Process_Statement => 1333,
+      Iir_Kind_Concurrent_Simple_Signal_Assignment => 1345,
+      Iir_Kind_Concurrent_Conditional_Signal_Assignment => 1357,
+      Iir_Kind_Concurrent_Selected_Signal_Assignment => 1370,
+      Iir_Kind_Concurrent_Assertion_Statement => 1378,
+      Iir_Kind_Concurrent_Procedure_Call_Statement => 1385,
+      Iir_Kind_Psl_Assert_Statement => 1398,
+      Iir_Kind_Psl_Cover_Statement => 1411,
+      Iir_Kind_Block_Statement => 1425,
+      Iir_Kind_If_Generate_Statement => 1436,
+      Iir_Kind_Case_Generate_Statement => 1445,
+      Iir_Kind_For_Generate_Statement => 1454,
+      Iir_Kind_Component_Instantiation_Statement => 1465,
+      Iir_Kind_Psl_Default_Clock => 1469,
+      Iir_Kind_Simple_Simultaneous_Statement => 1476,
+      Iir_Kind_Generate_Statement_Body => 1487,
+      Iir_Kind_If_Generate_Else_Clause => 1493,
+      Iir_Kind_Simple_Signal_Assignment_Statement => 1503,
+      Iir_Kind_Conditional_Signal_Assignment_Statement => 1513,
+      Iir_Kind_Selected_Waveform_Assignment_Statement => 1524,
+      Iir_Kind_Null_Statement => 1528,
+      Iir_Kind_Assertion_Statement => 1535,
+      Iir_Kind_Report_Statement => 1541,
+      Iir_Kind_Wait_Statement => 1549,
+      Iir_Kind_Variable_Assignment_Statement => 1556,
+      Iir_Kind_Conditional_Variable_Assignment_Statement => 1563,
+      Iir_Kind_Return_Statement => 1569,
+      Iir_Kind_For_Loop_Statement => 1578,
+      Iir_Kind_While_Loop_Statement => 1587,
+      Iir_Kind_Next_Statement => 1594,
+      Iir_Kind_Exit_Statement => 1601,
+      Iir_Kind_Case_Statement => 1609,
+      Iir_Kind_Procedure_Call_Statement => 1615,
+      Iir_Kind_If_Statement => 1625,
+      Iir_Kind_Elsif => 1631,
+      Iir_Kind_Character_Literal => 1639,
+      Iir_Kind_Simple_Name => 1647,
+      Iir_Kind_Selected_Name => 1656,
+      Iir_Kind_Operator_Symbol => 1662,
+      Iir_Kind_Reference_Name => 1666,
+      Iir_Kind_External_Constant_Name => 1674,
+      Iir_Kind_External_Signal_Name => 1682,
+      Iir_Kind_External_Variable_Name => 1691,
+      Iir_Kind_Selected_By_All_Name => 1697,
+      Iir_Kind_Parenthesis_Name => 1702,
+      Iir_Kind_Package_Pathname => 1706,
+      Iir_Kind_Absolute_Pathname => 1707,
+      Iir_Kind_Relative_Pathname => 1708,
+      Iir_Kind_Pathname_Element => 1713,
+      Iir_Kind_Base_Attribute => 1715,
+      Iir_Kind_Subtype_Attribute => 1720,
+      Iir_Kind_Element_Attribute => 1725,
+      Iir_Kind_Left_Type_Attribute => 1730,
+      Iir_Kind_Right_Type_Attribute => 1735,
+      Iir_Kind_High_Type_Attribute => 1740,
+      Iir_Kind_Low_Type_Attribute => 1745,
+      Iir_Kind_Ascending_Type_Attribute => 1750,
+      Iir_Kind_Image_Attribute => 1756,
+      Iir_Kind_Value_Attribute => 1762,
+      Iir_Kind_Pos_Attribute => 1768,
+      Iir_Kind_Val_Attribute => 1774,
+      Iir_Kind_Succ_Attribute => 1780,
+      Iir_Kind_Pred_Attribute => 1786,
+      Iir_Kind_Leftof_Attribute => 1792,
+      Iir_Kind_Rightof_Attribute => 1798,
+      Iir_Kind_Delayed_Attribute => 1807,
+      Iir_Kind_Stable_Attribute => 1816,
+      Iir_Kind_Quiet_Attribute => 1825,
+      Iir_Kind_Transaction_Attribute => 1834,
+      Iir_Kind_Event_Attribute => 1838,
+      Iir_Kind_Active_Attribute => 1842,
+      Iir_Kind_Last_Event_Attribute => 1846,
+      Iir_Kind_Last_Active_Attribute => 1850,
+      Iir_Kind_Last_Value_Attribute => 1854,
+      Iir_Kind_Driving_Attribute => 1858,
+      Iir_Kind_Driving_Value_Attribute => 1862,
+      Iir_Kind_Behavior_Attribute => 1862,
+      Iir_Kind_Structure_Attribute => 1862,
+      Iir_Kind_Simple_Name_Attribute => 1869,
+      Iir_Kind_Instance_Name_Attribute => 1874,
+      Iir_Kind_Path_Name_Attribute => 1879,
+      Iir_Kind_Left_Array_Attribute => 1886,
+      Iir_Kind_Right_Array_Attribute => 1893,
+      Iir_Kind_High_Array_Attribute => 1900,
+      Iir_Kind_Low_Array_Attribute => 1907,
+      Iir_Kind_Length_Array_Attribute => 1914,
+      Iir_Kind_Ascending_Array_Attribute => 1921,
+      Iir_Kind_Range_Array_Attribute => 1928,
+      Iir_Kind_Reverse_Range_Array_Attribute => 1935,
+      Iir_Kind_Attribute_Name => 1944
      );
 
    function Get_Fields_First (K : Iir_Kind) return Fields_Index is
@@ -7045,7 +7058,8 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Interface_Constant_Declaration
            | Iir_Kind_Interface_Variable_Declaration
            | Iir_Kind_Interface_Signal_Declaration
-           | Iir_Kind_Interface_File_Declaration =>
+           | Iir_Kind_Interface_File_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             return True;
          when others =>
             return False;
@@ -7355,6 +7369,7 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Interface_Package_Declaration
            | Iir_Kind_Interface_Function_Declaration
            | Iir_Kind_Interface_Procedure_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Signal_Attribute_Declaration
            | Iir_Kind_Sensitized_Process_Statement
            | Iir_Kind_Process_Statement
@@ -7466,6 +7481,7 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Interface_File_Declaration
            | Iir_Kind_Interface_Type_Declaration
            | Iir_Kind_Interface_Function_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Identity_Operator
            | Iir_Kind_Negation_Operator
            | Iir_Kind_Absolute_Operator
@@ -7528,6 +7544,7 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Simple_Name
            | Iir_Kind_Selected_Name
            | Iir_Kind_Operator_Symbol
+           | Iir_Kind_Reference_Name
            | Iir_Kind_External_Constant_Name
            | Iir_Kind_External_Signal_Name
            | Iir_Kind_External_Variable_Name
@@ -7879,7 +7896,8 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Interface_Constant_Declaration
            | Iir_Kind_Interface_Variable_Declaration
            | Iir_Kind_Interface_Signal_Declaration
-           | Iir_Kind_Interface_File_Declaration =>
+           | Iir_Kind_Interface_File_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration =>
             return True;
          when others =>
             return False;
@@ -8129,6 +8147,7 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Interface_Package_Declaration
            | Iir_Kind_Interface_Function_Declaration
            | Iir_Kind_Interface_Procedure_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Selected_Element
            | Iir_Kind_Sensitized_Process_Statement
            | Iir_Kind_Process_Statement
@@ -9084,6 +9103,7 @@ package body Vhdl.Nodes_Meta is
          when Iir_Kind_Conditional_Expression
            | Iir_Kind_Attribute_Specification
            | Iir_Kind_Disconnection_Specification
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Parenthesis_Expression
            | Iir_Kind_Qualified_Expression
            | Iir_Kind_Type_Conversion
@@ -9344,6 +9364,7 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Interface_Package_Declaration
            | Iir_Kind_Interface_Function_Declaration
            | Iir_Kind_Interface_Procedure_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Signal_Attribute_Declaration
            | Iir_Kind_Sensitized_Process_Statement
            | Iir_Kind_Process_Statement
@@ -10659,6 +10680,7 @@ package body Vhdl.Nodes_Meta is
            | Iir_Kind_Interface_Signal_Declaration
            | Iir_Kind_Interface_File_Declaration
            | Iir_Kind_Interface_Type_Declaration
+           | Iir_Kind_Anonymous_Signal_Declaration
            | Iir_Kind_Sensitized_Process_Statement
            | Iir_Kind_Concurrent_Simple_Signal_Assignment
            | Iir_Kind_Concurrent_Conditional_Signal_Assignment
diff --git a/src/vhdl/vhdl-prints.adb b/src/vhdl/vhdl-prints.adb
index 634e2be3c..a1ce5f01b 100644
--- a/src/vhdl/vhdl-prints.adb
+++ b/src/vhdl/vhdl-prints.adb
@@ -2209,6 +2209,8 @@ package body Vhdl.Prints is
                Disp_Attribute_Specification (Ctxt, Decl);
             when Iir_Kind_Signal_Attribute_Declaration =>
                null;
+            when Iir_Kind_Anonymous_Signal_Declaration =>
+               null;
             when Iir_Kind_Group_Template_Declaration =>
                Disp_Group_Template_Declaration (Ctxt, Decl);
             when Iir_Kind_Group_Declaration =>
@@ -3484,6 +3486,17 @@ package body Vhdl.Prints is
          when Iir_Kind_Implicit_Dereference =>
             Print (Ctxt, Get_Prefix (Expr));
 
+         when Iir_Kind_Anonymous_Signal_Declaration =>
+            declare
+               Act : constant Iir := Get_Expression (Expr);
+            begin
+               if Act /= Null_Iir then
+                  Print (Ctxt, Act);
+               else
+                  Disp_Identifier (Ctxt, Expr);
+               end if;
+            end;
+
          when Iir_Kind_Left_Type_Attribute =>
             Disp_Name_Attribute (Ctxt, Expr, Name_Left);
          when Iir_Kind_Right_Type_Attribute =>
diff --git a/src/vhdl/vhdl-sem.adb b/src/vhdl/vhdl-sem.adb
index 503d43293..7e6785a2b 100644
--- a/src/vhdl/vhdl-sem.adb
+++ b/src/vhdl/vhdl-sem.adb
@@ -462,6 +462,31 @@ package body Vhdl.Sem is
       Res := Sem_Generic_Association_Chain (Inter_Parent, Assoc_Parent);
    end Sem_Generic_Association_Chain;
 
+   --  LRM08 6.5.6.3 Port clauses
+   function Sem_Insert_Anonymous_Signal (Formal : Iir; Actual : Iir)
+                                        return Iir
+   is
+      Sig : Iir;
+      Res : Iir;
+   begin
+      --  Create the anonymous signal.
+      Sig := Create_Iir (Iir_Kind_Anonymous_Signal_Declaration);
+      Location_Copy (Sig, Actual);
+      Set_Expression (Sig, Actual);
+      Set_Type (Sig, Get_Type (Formal));
+
+      --  Declare it.
+      Add_Implicit_Declaration (Sig);
+
+      --  Return a reference to it.
+      --  FIXME: The referenced name is not a name.
+      Res := Create_Iir (Iir_Kind_Reference_Name);
+      Set_Referenced_Name (Res, Sig);
+      Set_Named_Entity (Res, Sig);
+      Set_Type (Res, Get_Type (Sig));
+      return Res;
+   end Sem_Insert_Anonymous_Signal;
+
    --  INTER_PARENT contains ports interfaces;
    --  ASSOC_PARENT constains ports map aspects.
    procedure Sem_Port_Association_Chain
@@ -577,18 +602,24 @@ package body Vhdl.Sem is
                           & "expression");
                   end if;
 
+                  --  Is it possible to have a globally static name that is
+                  --  not readable ?
+                  Check_Read (Actual);
+
                   --  LRM93 1.1.1.2 Ports
                   --  The actual, if an expression, must be a globally
                   --  static expression.
                   if Get_Expr_Staticness (Actual) < Globally then
-                     Error_Msg_Sem
-                       (+Actual,
-                        "actual expression must be globally static");
+                     if Flags.Vhdl_Std >= Vhdl_08 then
+                        --  LRM08 6.5.6.3 Port clauses
+                        Actual := Sem_Insert_Anonymous_Signal (Inter, Actual);
+                        Set_Actual (Assoc, Actual);
+                     else
+                        Error_Msg_Sem
+                          (+Actual,
+                           "actual expression must be globally static");
+                     end if;
                   end if;
-
-                  --  Is it possible to have a globally static name that is
-                  --  not readable ?
-                  Check_Read (Actual);
                else
                   Error_Msg_Sem
                     (+Assoc,
diff --git a/src/vhdl/vhdl-sem_decls.adb b/src/vhdl/vhdl-sem_decls.adb
index 9e98c26a3..0f173d923 100644
--- a/src/vhdl/vhdl-sem_decls.adb
+++ b/src/vhdl/vhdl-sem_decls.adb
@@ -116,6 +116,9 @@ package body Vhdl.Sem_Decls is
       if Current_Signals_Region.Decls_Parent = Parent
         and then Current_Signals_Region.Implicit_Decl /= Null_Iir
       then
+         --  There are pending implicit declarations.  Can happen only
+         --  during analysis of declarations, therefore when declarations are
+         --  not fully analyzed.
          pragma Assert (not Current_Signals_Region.Decls_Analyzed);
 
          --  Add pending implicit declarations before the current one.
@@ -128,6 +131,22 @@ package body Vhdl.Sem_Decls is
       end if;
    end Insert_Pending_Implicit_Declarations;
 
+   procedure Add_Implicit_Declaration (Sig : Iir) is
+   begin
+      --  Only for anonymous signals, which appear in instantiations (so
+      --  once the declarations have been analyzed).
+      pragma Assert (Get_Kind (Sig) = Iir_Kind_Anonymous_Signal_Declaration);
+      pragma Assert (Current_Signals_Region.Decls_Analyzed);
+
+      if Current_Signals_Region.Last_Decl = Null_Iir then
+         Set_Declaration_Chain (Current_Signals_Region.Decls_Parent, Sig);
+      else
+         Set_Chain (Current_Signals_Region.Last_Decl, Sig);
+      end if;
+      Current_Signals_Region.Last_Decl := Sig;
+      Set_Parent (Sig, Current_Signals_Region.Decls_Parent);
+   end Add_Implicit_Declaration;
+
    --  Mark the end of declaration analysis.  New implicit declarations will
    --  simply be appended to the last declaration.
    procedure End_Of_Declarations_For_Implicit_Declarations
diff --git a/src/vhdl/vhdl-sem_decls.ads b/src/vhdl/vhdl-sem_decls.ads
index f22cd8791..3ab43adf8 100644
--- a/src/vhdl/vhdl-sem_decls.ads
+++ b/src/vhdl/vhdl-sem_decls.ads
@@ -75,9 +75,14 @@ package Vhdl.Sem_Decls is
    procedure Pop_Signals_Declarative_Part
      (Cell: in Implicit_Signal_Declaration_Type);
 
-   --  Declare an implicit signal.
+   --  Declare an implicit signal.  This is called from sem_names when a
+   --  signal attribute is analyzed.
    procedure Add_Declaration_For_Implicit_Signal (Sig : Iir);
 
+   --  Append declaration SIG (for an anonymous signal) to the current
+   --  declarative part.
+   procedure Add_Implicit_Declaration (Sig : Iir);
+
 private
    type Implicit_Signal_Declaration_Type is record
       --  Declaration or statement than will contain implicit declarations.
@@ -92,10 +97,13 @@ private
 
       --  If True, declarations of DECLS_PARENT have already been analyzed.
       --  So implicit declarations are appended to the parent, and the last
-      --  declaration is LAST_DECL.
+      --  declaration is LAST_DECL.  This is the usual case when attribute
+      --  signals are used in statements.
       --  If False, declarations are being analyzed.  Implicit declarations
       --  are appended to IMPLICIT_DECL/LAST_ATTRIBUTE_SIGNAL and will be
-      --  inserted before the current declaration.
+      --  inserted before the current declaration.  This can happen if a
+      --  attribute signal is used in a declaration, the attribute signal
+      --  must be declared before it is used.
       Decls_Analyzed : Boolean;
 
       --  Last declaration in the region.  If an implicit_decl is createed, it
diff --git a/src/vhdl/vhdl-sem_names.adb b/src/vhdl/vhdl-sem_names.adb
index 35516f6f0..fa57a0d26 100644
--- a/src/vhdl/vhdl-sem_names.adb
+++ b/src/vhdl/vhdl-sem_names.adb
@@ -3345,6 +3345,8 @@ package body Vhdl.Sem_Names is
       Prefix : Iir;
    begin
       Prefix := Get_Named_Entity (Get_Prefix (Attr));
+
+      --  Create the proper signal attribute node.
       Res := Create_Iir (Kind);
       Location_Copy (Res, Attr);
       if Kind = Iir_Kind_Delayed_Attribute then
@@ -3371,6 +3373,8 @@ package body Vhdl.Sem_Names is
                null;
          end case;
       end if;
+
+      --  Add a declaration for it.
       Sem_Decls.Add_Declaration_For_Implicit_Signal (Res);
       return Res;
    end Sem_Signal_Signal_Attribute;
diff --git a/src/vhdl/vhdl-utils.adb b/src/vhdl/vhdl-utils.adb
index ea269f2cc..8c550ab98 100644
--- a/src/vhdl/vhdl-utils.adb
+++ b/src/vhdl/vhdl-utils.adb
@@ -163,7 +163,8 @@ package body Vhdl.Utils is
       end case;
    end Get_Operator_Name;
 
-   function Get_Longuest_Static_Prefix (Expr: Iir) return Iir is
+   function Get_Longuest_Static_Prefix (Expr: Iir) return Iir
+   is
       Adecl: Iir;
    begin
       Adecl := Expr;
@@ -177,6 +178,7 @@ package body Vhdl.Utils is
                return Adecl;
             when Iir_Kind_Signal_Declaration
               | Iir_Kind_Guard_Signal_Declaration
+              | Iir_Kind_Anonymous_Signal_Declaration
               | Iir_Kind_Interface_Signal_Declaration =>
                return Adecl;
             when Iir_Kind_Object_Alias_Declaration =>
@@ -297,6 +299,7 @@ package body Vhdl.Utils is
               | Iir_Kind_Scalar_Nature_Definition
               | Iir_Kind_Group_Template_Declaration
               | Iir_Kind_Group_Declaration
+              | Iir_Kind_Anonymous_Signal_Declaration
               | Iir_Kind_Signal_Attribute_Declaration
               | Iir_Kind_Unaffected_Waveform
               | Iir_Kind_Waveform_Element