[Ada] Support aspect Relaxed_Initialization on private types and constants

--- gcc/ada/einfo.adb
+++ gcc/ada/einfo.adb
@@ -8256,8 +8256,7 @@  package body Einfo is
    function Is_Relaxed_Initialization_State (Id : E) return B is
    begin
       --  To qualify, the abstract state must appear with simple option
-      --  "Relaxed_Initialization" (??? add reference to SPARK RM once the
-      --  Relaxed_Initialization aspect is described there).
+      --  "Relaxed_Initialization" (SPARK RM 6.10).
 
       return
         Ekind (Id) = E_Abstract_State

--- gcc/ada/sem_attr.adb
+++ gcc/ada/sem_attr.adb
@@ -1333,8 +1333,7 @@  package body Sem_Attr is
                null;
 
             --  Attribute 'Result is allowed to appear in aspect
-            --  Relaxed_Initialization (??? add reference to SPARK RM once this
-            --  attribute is described there).
+            --  Relaxed_Initialization (SPARK RM 6.10).
 
             elsif Prag_Nam = Name_Relaxed_Initialization
               and then Aname = Name_Result

--- gcc/ada/sem_ch13.adb
+++ gcc/ada/sem_ch13.adb
@@ -2216,19 +2216,37 @@  package body Sem_Ch13 is
                --  Will be set to True if we need to restore the scope table
                --  after analyzing the aspect expression.
 
+               Prev_Id : Entity_Id;
+
             --  Start of processing for Analyze_Aspect_Relaxed_Initialization
 
             begin
                --  Set name of the aspect for error messages
                Error_Msg_Name_1 := Nam;
 
-               --  Annotation of a type; no aspect expression is allowed
+               --  Annotation of a type; no aspect expression is allowed.
+               --  For a private type, the aspect must be attached to the
+               --  partial view.
+               --
                --  ??? Once the exact rule for this aspect is ready, we will
                --  likely reject concurrent types, etc., so let's keep the code
                --  for types and variable separate.
 
                if Is_First_Subtype (E) then
-                  if Present (Expr) then
+                  Prev_Id := Incomplete_Or_Partial_View (E);
+                  if Present (Prev_Id) then
+
+                     --  Aspect may appear on the full view of an incomplete
+                     --  type because the incomplete declaration cannot have
+                     --  any aspects.
+
+                     if Ekind (Prev_Id) = E_Incomplete_Type then
+                        null;
+                     else
+                        Error_Msg_N ("aspect % must apply to partial view", N);
+                     end if;
+
+                  elsif Present (Expr) then
                      Error_Msg_N ("illegal aspect % expression", Expr);
                   end if;
 
@@ -2239,6 +2257,19 @@  package body Sem_Ch13 is
                      Error_Msg_N ("illegal aspect % expression", Expr);
                   end if;
 
+               --  Annotation of a constant; no aspect expression is allowed.
+               --  For a deferred constant, the aspect must be attached to the
+               --  partial view.
+
+               elsif Ekind (E) = E_Constant then
+                  if Present (Incomplete_Or_Partial_View (E)) then
+                     Error_Msg_N
+                       ("aspect % must apply to deferred constant", N);
+
+                  elsif Present (Expr) then
+                     Error_Msg_N ("illegal aspect % expression", Expr);
+                  end if;
+
                --  Annotation of a subprogram; aspect expression is required
 
                elsif Is_Subprogram (E) then

--- gcc/ada/sem_util.adb
+++ gcc/ada/sem_util.adb
@@ -12495,13 +12495,20 @@  package body Sem_Util is
          when E_Abstract_State =>
             return Is_Relaxed_Initialization_State (E);
 
+         --  Constants have this aspect attached directly; for deferred
+         --  constants, the aspect is attached to the partial view.
+
+         when E_Constant =>
+            return Has_Aspect (E, Aspect_Relaxed_Initialization);
+
          --  Variables have this aspect attached directly
 
          when E_Variable =>
             return Has_Aspect (E, Aspect_Relaxed_Initialization);
 
          --  Types have this aspect attached directly (though we only allow it
-         --  to be specified for the first subtype).
+         --  to be specified for the first subtype). For private types, the
+         --  aspect is attached to the partial view.
 
          when Type_Kind =>
             pragma Assert (Is_First_Subtype (E));

--- gcc/ada/sem_util.ads
+++ gcc/ada/sem_util.ads
@@ -1382,9 +1382,10 @@  package Sem_Util is
    --  yet received a full declaration.
 
    function Has_Relaxed_Initialization (E : Entity_Id) return Boolean;
-   --  Returns True iff entity E, which can be either a type, a variable, an
-   --  abstract state or a function, is subject to the Relaxed_Initialization
-   --  aspect.
+   --  Returns True iff entity E is subject to the Relaxed_Initialization
+   --  aspect. Entity E can be either type, variable, constant, function,
+   --  or abstract state. For private types and deferred constants E should
+   --  be the private view, because aspect can only be attached there.
 
    function Has_Signed_Zeros (E : Entity_Id) return Boolean;
    --  Determines if the floating-point type E supports signed zeros.