diff --git a/gcc/ada/exp_disp.adb b/gcc/ada/exp_disp.adb
--- a/gcc/ada/exp_disp.adb
+++ b/gcc/ada/exp_disp.adb
@@ -3037,7 +3037,7 @@ package body Exp_Disp is
    begin
       pragma Assert (not Restriction_Active (No_Dispatching_Calls));
 
-      --  Null body is generated for interface types and non-concurrent
+      --  Null body is generated for interface types and nonconcurrent
       --  tagged types.
 
       if Is_Interface (Typ)


diff --git a/gcc/ada/freeze.adb b/gcc/ada/freeze.adb
--- a/gcc/ada/freeze.adb
+++ b/gcc/ada/freeze.adb
@@ -9500,9 +9500,7 @@ package body Freeze is
          Minsiz : constant Uint := UI_From_Int (Minimum_Size (Typ));
 
       begin
-         if Known_RM_Size (Typ)
-           and then RM_Size (Typ) /= Uint_0
-         then
+         if Known_RM_Size (Typ) then
             if RM_Size (Typ) < Minsiz then
                Error_Msg_Uint_1 := RM_Size (Typ);
                Error_Msg_Uint_2 := Minsiz;


diff --git a/gcc/ada/gen_il-gen.ads b/gcc/ada/gen_il-gen.ads
--- a/gcc/ada/gen_il-gen.ads
+++ b/gcc/ada/gen_il-gen.ads
@@ -204,9 +204,22 @@ package Gen_IL.Gen is
    --  Gen_IL.Fields, and delete all occurrences from Gen_IL.Gen.Gen_Entities.
 
    --  If a field is not set, it is initialized by default to whatever value is
-   --  represented by all-zero bits, with two exceptions: Elist fields default
-   --  to No_Elist, and Uint fields default to Uint_0. In retrospect, it would
-   --  have been better to use No_Uint instead of Uint_0.
+   --  represented by all-zero bits, with some exceptions. This means Flags are
+   --  initialized to False, Node_Ids and List_Ids are initialized to Empty,
+   --  and enumeration fields are initialized to 'First of the type (assuming
+   --  there is no representation clause).
+   --
+   --  Elists default to No_Elist.
+   --
+   --  Fields of type Uint (but not its subtypes) are initialized to No_Uint.
+   --  Fields of subtypes Valid_Uint, Unat, Upos, Nonzero_Uint, and Ureal have
+   --  no default; it is an error to call a getter before calling the setter.
+   --  Likewise, other types whose range does not include zero have no default
+   --  (see package Types for the ranges).
+   --
+   --  If a node is created by a function in Nmake, then the defaults are
+   --  different from what is specified above. The parameters of Make_...
+   --  functions can have defaults specified; see Create_Syntactic_Field.
 
    procedure Create_Node_Union_Type
      (T : Abstract_Node; Children : Type_Array);


diff --git a/gcc/ada/repinfo.adb b/gcc/ada/repinfo.adb
--- a/gcc/ada/repinfo.adb
+++ b/gcc/ada/repinfo.adb
@@ -2120,7 +2120,7 @@ package body Repinfo is
 
    function Rep_Value (Val : Node_Ref_Or_Val; D : Discrim_List) return Uint is
 
-      function B (Val : Boolean) return Uint;
+      function B (Val : Boolean) return Ubool;
       --  Returns Uint_0 for False, Uint_1 for True
 
       function T (Val : Node_Ref_Or_Val) return Boolean;
@@ -2141,7 +2141,7 @@ package body Repinfo is
       -- B --
       -------
 
-      function B (Val : Boolean) return Uint is
+      function B (Val : Boolean) return Ubool is
       begin
          if Val then
             return Uint_1;


diff --git a/gcc/ada/repinfo.ads b/gcc/ada/repinfo.ads
--- a/gcc/ada/repinfo.ads
+++ b/gcc/ada/repinfo.ads
@@ -118,12 +118,12 @@ package Repinfo is
    --  this field is done only in -gnatR3 mode, and in other modes, the value
    --  is set to Uint_Minus_1.
 
-   subtype Node_Ref is Uint;
+   subtype Node_Ref is Unegative;
    --  Subtype used for negative Uint values used to represent nodes
 
    subtype Node_Ref_Or_Val is Uint;
-   --  Subtype used for values that can either be a Node_Ref (negative)
-   --  or a value (non-negative)
+   --  Subtype used for values that can be a Node_Ref (negative) or a value
+   --  (non-negative) or No_Uint.
 
    type TCode is range 0 .. 27;
    --  Type used on Ada side to represent DEFTREECODE values defined in
@@ -306,7 +306,7 @@ package Repinfo is
    --  In the case of components, if the location of the component is static,
    --  then all four fields (Component_Bit_Offset, Normalized_Position, Esize,
    --  and Normalized_First_Bit) are set to appropriate values. In the case of
-   --  a non-static component location, Component_Bit_Offset is not used and
+   --  a nonstatic component location, Component_Bit_Offset is not used and
    --  is left set to Unknown. Normalized_Position and Normalized_First_Bit
    --  are set appropriately.
 


diff --git a/gcc/ada/sem_ch3.adb b/gcc/ada/sem_ch3.adb
--- a/gcc/ada/sem_ch3.adb
+++ b/gcc/ada/sem_ch3.adb
@@ -21301,7 +21301,7 @@ package body Sem_Ch3 is
                      goto Leave;
                   end;
 
-               --  For non-concurrent types, transfer explicit primitives, but
+               --  For nonconcurrent types, transfer explicit primitives, but
                --  omit those inherited from the parent of the private view
                --  since they will be re-inherited later on.
 


diff --git a/gcc/ada/sem_ch8.adb b/gcc/ada/sem_ch8.adb
--- a/gcc/ada/sem_ch8.adb
+++ b/gcc/ada/sem_ch8.adb
@@ -9236,7 +9236,7 @@ package body Sem_Ch8 is
       if Ekind (S) = E_Void then
          null;
 
-      --  Set scope depth if not a non-concurrent type, and we have not yet set
+      --  Set scope depth if not a nonconcurrent type, and we have not yet set
       --  the scope depth. This means that we have the first occurrence of the
       --  scope, and this is where the depth is set.
 


diff --git a/gcc/ada/sinfo-utils.adb b/gcc/ada/sinfo-utils.adb
--- a/gcc/ada/sinfo-utils.adb
+++ b/gcc/ada/sinfo-utils.adb
@@ -189,13 +189,9 @@ package body Sinfo.Utils is
    ------------------
 
    function End_Location (N : Node_Id) return Source_Ptr is
-      L : constant Uint := End_Span (N);
+      L : constant Valid_Uint := End_Span (N);
    begin
-      if No (L) then
-         return No_Location;
-      else
-         return Source_Ptr (Int (Sloc (N)) + UI_To_Int (L));
-      end if;
+      return Source_Ptr (Int (Sloc (N)) + UI_To_Int (L));
    end End_Location;
 
    --------------------


diff --git a/gcc/ada/uintp.adb b/gcc/ada/uintp.adb
--- a/gcc/ada/uintp.adb
+++ b/gcc/ada/uintp.adb
@@ -380,8 +380,8 @@ package body Uintp is
 
       procedure Image_String (S : String) is
       begin
-         for X in S'Range loop
-            Image_Char (S (X));
+         for X of S loop
+            Image_Char (X);
          end loop;
       end Image_String;
 


diff --git a/gcc/ada/uintp.ads b/gcc/ada/uintp.ads
--- a/gcc/ada/uintp.ads
+++ b/gcc/ada/uintp.ads
@@ -104,6 +104,7 @@ package Uintp is
    subtype Unat is Valid_Uint with Predicate => Unat >= Uint_0; -- natural
    subtype Upos is Valid_Uint with Predicate => Upos >= Uint_1; -- positive
    subtype Nonzero_Uint is Valid_Uint with Predicate => Nonzero_Uint /= Uint_0;
+   subtype Unegative is Valid_Uint with Predicate => Unegative < Uint_0;
    subtype Ubool is Valid_Uint with Predicate => Ubool in Uint_0 | Uint_1;
    subtype Opt_Ubool is Uint with
      Predicate => No (Opt_Ubool) or else Opt_Ubool in Ubool;


